Insights into Coking Deactivation of Zeolite Catalysts:Coke deposition behavior,Mechanism and Factor
沸石催化剂焦化失活研究：焦炭沉积行为、机理及影响因素

2. Coke Deposition Behavior in Zeolite Catalysts
2. 沸石催化剂中的焦炭沉积行为

Coke deposition stands as a primary cause of deactivation in zeolite catalysts, significantly impeding their performance across various industrial processes. Understanding the intricate behavior of coke deposition is crucial for designing robust and long-lasting catalytic systems. This section provides a comprehensive overview of coke deposition, comparing and contrasting findings across different zeolite types and reaction conditions, while classifying coke based on its location, nature, and quantity. It further analyzes the profound impact of coke on the accessibility of active sites and the diffusion of reactants and products within the zeolite structure, identifying key correlations between zeolite properties and observed coking patterns.
焦炭沉积是沸石催化剂失活的主要原因，严重阻碍了其在各种工业过程中的性能。了解焦炭沉积的复杂行为对于设计稳健和持久的催化系统至关重要。本节全面概述了焦炭沉积，比较和对比了不同沸石类型和反应条件下的研究结果，并根据焦炭的位置、性质和数量对其进行了分类。本节还进一步分析了焦炭对活性位点可及性以及反应物和产物在沸石结构内扩散的深远影响，确定了沸石性质与观察到的焦化模式之间的关键关联。

The spatial distribution of coke within zeolite catalysts is highly diverse and depends on the specific zeolite architecture and reaction environment. Common patterns include an “eggshell” distribution, where coke preferentially accumulates on the outer surface or edges of zeolite crystals, observed in ZSM-5 and SAPO-34 systems [19,24]. Coke evolution often progresses from initial deposition on external surfaces or crystal steps to migration and accumulation within pore channels as reactions proceed [16,20,22]. The relative distribution between external, micropore, and mesopore coke can vary significantly, with micropores sometimes accounting for the largest fraction in certain applications like residue fluid catalytic cracking [33]. Zeolite pore size plays a nuanced role; while smaller pores might limit coke to the external surface and larger pores allow internal accumulation, the actual behavior is complex, influenced by factors like co-feeding agents, reactant source, and catalyst modifications [12,34,38,39,42]. Advanced characterization techniques, including Confocal Fluorescence Microscopy (CFM), Hyperpolarized (HP)
沸石催化剂中焦炭的空间分布高度多样化，取决于具体的沸石结构和反应环境。常见的模式包括“蛋壳”分布，即焦炭优先积聚在沸石晶体的外表面或边缘，这在 ZSM-5 和 SAPO-34 体系中均有观察到[19,24]。焦炭的演变通常从最初在外表面或晶体台阶上的沉积开始，随着反应的进行，逐渐迁移并积聚在孔道内[16,20,22]。外部、微孔和介孔焦炭的相对分布可能差异很大，在某些应用中，如渣油催化裂化，微孔焦炭有时占最大比例[33]。沸石孔径扮演着微妙的角色；虽然较小的孔可能将焦炭限制在外表面，而较大的孔允许内部积聚，但实际行为是复杂的，受共进料剂、反应物来源和催化剂改性等因素的影响[12,34,38,39,42]。先进的表征技术，包括共聚焦荧光显微镜（CFM）、超极化（HP）

The nature and composition of coke vary significantly, ranging from soft, aliphatic species to hard, condensed polycyclic aromatic hydrocarbons (PAHs) and even graphite-like structures [9,22,40]. This composition dynamically evolves over reaction time, with a general trend towards increasing unsaturation and condensation, evidenced by a decreasing H/C ratio and the formation of larger polyaromatic species [10,19,20,30]. Zeolite topology critically influences the resultant coke composition; for instance, HZSM-5 typically forms benzene-derived species, while larger-pore zeolites like
积炭的性质和组成差异显著，从柔软的脂肪族化合物到坚硬的稠合多环芳烃（PAHs），甚至类石墨结构均有发现[9,22,40]。其组成随反应时间动态演变，总体趋势表现为不饱和度增加和稠合度提高，这通过降低的 H/C 比和更大分子量多环芳烃的形成得以证实[10,19,20,30]。沸石拓扑结构对最终积炭组成具有决定性影响——例如 HZSM-5 通常生成苯系衍生物，而大孔沸石如...

The quantification and temporal evolution of coke are essential for predicting catalyst lifetime. Coke content typically increases over time-on-stream, often with an initial rapid accumulation followed by a deceleration or saturation phase, demonstrating diverse kinetic profiles such as exponential or linear growth depending on the system [7,10,19,21,30,39,47]. During this evolution, softer coke species transform into harder, more difficult-to-remove forms, impacting regeneration strategies [16,20,22]. Reaction conditions, including temperature, reactant partial pressure, and feed composition, profoundly influence coking rates and total coke quantities [7,18,30,34,36]. Zeolite properties such as the
积碳的定量分析与时效演变对预测催化剂寿命至关重要。积碳含量通常随运行时间延长而增加，其动力学曲线常呈现初期快速累积后进入减速或饱和阶段的不同特征，具体表现为指数型或线性增长等模式，这取决于反应体系特性[7,10,19,21,30,39,47]。在此演变过程中，较软的积碳前驱体会逐渐转化为更难脱除的硬质焦炭，这一特性直接影响再生策略的制定[16,20,22]。反应条件（包括温度、反应物分压及进料组成）会显著影响结焦速率与积碳总量[7,18,30,34,36]。而分子筛的固有特性如

Coke deposition critically impacts catalyst properties through two primary mechanisms: the direct coverage and poisoning of active sites, and the physical blockage of the pore network. Active sites, particularly Brønsted and strong acid sites, are preferentially affected, leading to a significant reduction in acidity and catalytic activity [5,12,14,18,29,30,33,35,43,45,48,49]. Simultaneously, coke physically occludes the zeolite's pore network, reducing total surface area and pore volume, with micropores often experiencing more severe blockage than mesopores [10,16,18,21,22,24,36,39,44,47]. This pore blockage leads to severe mass transfer limitations, as bulky coke species hinder the diffusion of reactants to active sites and products from the catalyst, consequently diminishing reaction rates and altering product selectivity [9,19,20,28,31,37,38,46]. Furthermore, coke accumulation can induce subtle structural changes within the zeolite framework itself, affecting its overall stability and performance [6,17,34,39,45].
积炭主要通过两种机制显著影响催化剂性能：一是直接覆盖和毒化活性位点，二是物理堵塞孔道网络。其中布朗斯特酸位点和强酸位点等活性中心优先受到影响，导致催化剂酸性和催化活性显著下降[5,12,14,18,29,30,33,35,43,45,48,49]。与此同时，积炭会物理堵塞分子筛的孔道系统，减少总比表面积和孔体积，其中微孔通常比介孔遭受更严重的堵塞[10,16,18,21,22,24,36,39,44,47]。这种孔道堵塞会导致严重的传质限制，因为大体积积炭物种阻碍了反应物向活性位点的扩散以及产物从催化剂中的脱附，从而降低反应速率并改变产物选择性[9,19,20,28,31,37,38,46]。此外，积炭的持续积累还可能引起分子筛骨架结构的微妙变化，影响其整体稳定性和催化性能[6,17,34,39,45]。

In summary, coke deposition is a multi-faceted phenomenon governed by complex interactions between zeolite properties (e.g., pore size, crystallinity, acidity), reaction conditions (e.g., temperature, feed composition, time-on-stream), and the intrinsic chemical pathways of coke formation. The spatial distribution, chemical nature, and accumulated quantity of coke collectively determine the extent of active site poisoning and pore blockage, directly influencing catalytic activity and selectivity. While significant progress has been made in characterizing these aspects, further research is needed to fully decouple the intricate relationships and develop more effective strategies for mitigating coking-induced deactivation in zeolite-catalyzed processes.
总之，积炭是一种受多种因素影响的现象，其形成过程涉及沸石特性（如孔径、结晶度、酸性）、反应条件（如温度、原料组成、运行时间）与积炭形成内在化学路径之间复杂的相互作用。积炭的空间分布、化学性质及累积量共同决定了活性位点中毒和孔道堵塞的程度，直接影响催化活性和选择性。尽管在这些方面的表征研究已取得显著进展，但仍需进一步研究以完全解析这些复杂关系，并开发更有效的策略来减轻沸石催化过程中积炭导致的失活。

2.1 Location of Coke Deposition
2.1 积炭沉积位置

The spatial distribution of coke deposits within zeolite catalysts is a critical factor influencing deactivation mechanisms, exhibiting complex patterns influenced by zeolite pore structure, crystal morphology, and reaction conditions. A frequently observed pattern is the “eggshell” distribution, where coke preferentially accumulates on the outer surface or edges of zeolite crystals. This phenomenon has been reported for various zeolites, including ZSM-5 extrudates during catalytic pyrolysis of biomass, where Confocal Fluorescence Microscopy (CFM) revealed an egg-shell spatial distribution with initial accumulation on the external surface, potentially influenced by diffusion limitations [24]. Similarly, for SAPO-34, coke species tend to deposit more on the outer shell, leading to a yolk-shell like distribution, as determined by CFM and hyperpolarized (HP) ^{129}Xe NMR techniques [19].
沸石催化剂中焦炭沉积的空间分布是影响失活机制的关键因素，其复杂分布模式受沸石孔道结构、晶体形貌及反应条件共同调控。其中"蛋壳型"分布是最常见的模式之一，表现为焦炭优先在沸石晶体外表面或边缘区域富集。在生物质催化热解过程中，ZSM-5 挤出催化剂通过共聚焦荧光显微镜（CFM）观测到这种外表面初始沉积的蛋壳型空间分布，可能与扩散限制有关[24]。类似地，SAPO-34 催化剂通过 CFM 和超极化（HP）^{129}Xe 核磁共振技术证实，焦炭组分更易在外壳沉积，形成类似蛋黄-蛋壳的分布特征[19]。

The evolution of coke deposition often follows a progression from external to internal sites. Initial carbon deposits may form on the catalyst surface [16], or at the edges and crystal steps of zeolites like ZSM-5 [20]. Subsequently, coke can migrate into the pore channels as the reaction proceeds [16,22]. Advanced stages can see a heavy coke envelope forming around zeolite crystals, blocking access to microporosity [10]. However, the relative proportions of external, micropore, and mesopore coke can vary significantly; for instance, in residue fluid catalytic cracking (RFCC) catalysts, micropores can account for the largest fraction of coke (41%) compared to the surface (32%) and mesopores (27%) [33].
积炭的演化通常遵循从外部位点向内部位点发展的过程。初始碳沉积可能形成于催化剂表面[16]，或 ZSM-5 等沸石晶体的边缘及台阶处[20]。随着反应进行，积炭会向孔道内迁移[16,22]。在高级阶段，沸石晶体周围可能形成致密积炭层，从而阻塞微孔通道[10]。然而外部积炭、微孔积炭与介孔积炭的相对比例存在显著差异：例如在渣油催化裂化（RFCC）催化剂中，微孔积炭占比（41%）可能远高于表面积炭（32%）和介孔积炭（27%）[33]。

The relationship between zeolite pore size and the location of coke deposition is complex and not always straightforward. While it is often hypothesized that zeolites with smaller pores tend to have coke deposited primarily on the external surface due to diffusion limitations, and those with larger pores exhibit coke deposition within the pores, the literature presents a more nuanced picture. For zeolites with restricted access to internal voids, such as ZSM-22 and SAPO-34, activity loss is largely attributed to soluble coke species retained within the structure, indicating internal deposition [21]. In SAPO-34, internal channels can become completely blocked prior to external access blockage due to easy accessibility [18], and presituated coke can distribute relatively evenly throughout the crystal [48].
沸石孔径与焦炭沉积位置之间的关系复杂，并非总是简单明了。尽管人们常假设，孔径较小的沸石由于扩散限制，焦炭主要沉积在其外表面，而孔径较大的沸石则在孔隙内部发生焦炭沉积，但现有文献呈现出更为细致的图景。对于内部空隙受限的沸石，如 ZSM-22 和 SAPO-34，其活性损失主要归因于结构内保留的可溶性焦炭物种，这表明存在内部沉积[21]。在 SAPO-34 中，由于易于接近，内部通道可能在外部通道被堵塞之前就完全堵塞[18]，并且预先形成的焦炭可以相对均匀地分布在整个晶体中[48]。

Conversely, larger pore structures like those in H-beta and H-SSZ-13 provide more space for the alkylation and cross-linking of cyclic intermediates, leading to the rapid accumulation of polycyclic aromatic hydrocarbons (PAHs) within the zeolite structure [44]. However, for Mordenite and Beta catalysts, which possess larger, three-dimensional pore networks, an accumulation of insoluble coke species, presumably on the external surface, is observed [21]. This suggests that while large pores can accommodate internal coke, they also facilitate the diffusion of coke precursors to the external surface where larger, insoluble species can form.
相反，H-beta 和 H-SSZ-13 等具有较大孔结构的分子筛为环状中间体的烷基化和交联提供了更多空间，导致多环芳烃（PAHs）在分子筛结构内迅速积累[44]。然而，对于具有更大三维孔网络的丝光沸石和 Beta 催化剂，观察到不溶性焦炭物种的积累，推测是在外表面[21]。这表明，虽然大孔可以容纳内部焦炭，但它们也促进了焦炭前体扩散到外表面，从而形成更大的不溶性物种。

For intermediate pore zeolites like ZSM-5, coke can be found both outside the crystals and inside the pores [45]. Internal coke in ZSM-5 is primarily located in channel intersections and along straight channels, with a higher fraction in straight channels (ca. 29%) compared to sinusoidal channels (ca. 16%) [39,42]. Factors such as co-feeding agents can drastically alter this distribution; formaldehyde cofeeding leads to more prominent micropore filling in ZSM-5, unlike pure methanol feed where external coke forms first [34]. Similarly, the source of reactants (e.g., lignin-derived coke forming externally vs. cellulose-derived coke accumulating internally in ZSM-5) [12] and catalyst modifications (e.g., alkaline treatment shifting ZSM-5 coke deposition from internal to preferential external) [38] can influence the predominant coke location. The type of loaded metal (Mo vs. W) can also dictate whether external or internal coke dominates deactivation [9].
对于 ZSM-5 等中孔沸石，焦炭可同时存在于晶体外部和孔道内部[45]。ZSM-5 内部焦炭主要分布在通道交叉处和直型通道内，其中直型通道的焦炭占比（约 29%）显著高于正弦型通道（约 16%）[39,42]。共进料剂等外部因素会显著改变这种分布：与纯甲醇进料时外部焦炭优先形成不同，甲醛共进料会导致 ZSM-5 微孔填充更为显著[34]。类似地，反应物来源（如木质素衍生焦炭主要形成于外部，而纤维素衍生焦炭则在 ZSM-5 内部积聚）[12]和催化剂改性（如碱处理使 ZSM-5 焦炭沉积从内部转向优先外部）[38]都会影响焦炭的主要分布位置。负载金属类型（钼与钨）同样能决定导致失活的是外部还是内部焦炭[9]。

2.2 Nature and Composition of Coke
2.2 焦炭的性质与组成

Coking deactivation in zeolite catalysts is fundamentally driven by the nature and composition of carbonaceous deposits, which vary significantly based on reaction conditions and zeolite characteristics. Generally, coke can be broadly categorized into two main types: soft coke, primarily composed of aliphatic hydrocarbons, and hard coke, characterized by more condensed aromatic and graphitic structures [22,40]. Analytical techniques such as FTIR,
沸石催化剂的积炭失活本质上是由碳质沉积物的性质和组成驱动的，这些沉积物会因反应条件和沸石特性的不同而显著变化。通常，积炭可大致分为两种主要类型：以脂肪烃为主的软焦和以稠合芳烃及石墨结构为特征的硬焦[22,40]。傅里叶变换红外光谱(FTIR)、

Nature and Evolution of Coke Species
积炭物种的性质与演化

The composition of coke is dynamically influenced by reaction time and conditions, undergoing a conversion from softer, more hydrogenated forms to harder, polycyclic aromatic hydrocarbons (PAHs) and even graphite-like structures. Initially, young coke contains a higher proportion of hydrogen and more aliphatic chains compared to older, more mature coke [40]. As reaction time progresses, a noticeable shift occurs: the H/C ratio of the coke decreases, indicating increasing unsaturation and condensation [10,30]. This evolution is evidenced by the transition from predominantly monocyclic to bicyclic and then polycyclic arenes [19] and the gradual growth of polyaromatic and methylated aromatic species into graphite-like structures over time [20]. For instance, during catalytic pyrolysis, an initial dominance of aliphatic coke gives way to the formation of benzene-like, naphthalene, and pyrene-like molecules [10]. Specific reaction conditions also dictate coke nature; higher reaction temperatures, such as those above
焦炭的组成受反应时间和条件的动态影响，经历从较软、氢化程度较高的形态向更硬的多环芳烃（PAHs）甚至类石墨结构的转变。初期形成的"年轻焦炭"含有较高比例的氢和更多脂肪链，而"成熟焦炭"则相反[40]。随着反应时间推移，可观察到明显变化：焦炭的 H/C 比下降，表明不饱和度和缩合度增加[10,30]。这一演变过程表现为从单环芳烃为主到双环芳烃，再到多环芳烃的转变[19]，以及多芳香和甲基化芳香物种随时间逐渐生长为类石墨结构[20]。例如在催化裂解过程中，初始阶段以脂肪族焦炭为主，随后逐渐形成苯系、萘系和芘系分子[10]。特定反应条件也决定焦炭性质；较高反应温度（如超过...

Zeolite type and its topological properties profoundly influence the structure and location of coke. Different zeolites yield distinct coke compositions, as observed during polyethylene cracking [15]. For HZSM-5, coke primarily consists of benzene molecules with long aliphatic chains, single-ring aromatics, indane, indene, and methyl-substituted aromatics [15,42]. In contrast,
沸石类型及其拓扑结构特性对积炭的结构与位置具有深远影响。不同沸石在聚乙烯裂解过程中会生成截然不同的积炭组分[15]。对于 HZSM-5 沸石，积炭主要由带有长脂肪链的苯分子、单环芳烃、茚满、茚以及甲基取代芳烃构成[15,42]。相比之下，

A clear correlation exists between the graphitization degree of coke and the severity of catalyst deactivation. Hard coke, characterized by highly graphitized PAHs, is a major contributor to deactivation, often appearing on the outer catalyst surface and blocking pores [9]. The formation of more condensed and less-alkylated PAHs with increasing coke content directly impacts catalyst performance [39]. For instance, the linear increase in C=C bonds in conjugated aromatics is directly correlated with catalyst deactivation [34]. Larger, more graphite-like coke species, identified by shifts in fluorescence emission maxima, are indicative of increased deactivation [20]. Micro–mesoporous zeolite catalysts, which generate lower order graphite carbon compared to the high-order graphite-carbon on HZSM-5, can influence the deactivation rate [25]. The rapid decrease in micropore volume and BET surface area, even at relatively low coke loads, underscores the critical role of highly condensed, graphitic coke in hindering catalytic activity [21].
焦炭的石墨化程度与催化剂失活程度之间存在明显相关性。以高度石墨化多环芳烃为特征的硬焦炭是导致失活的主要原因，通常出现在催化剂外表面并堵塞孔道[9]。随着焦炭含量增加，形成的缩合度更高、烷基化程度更低的多环芳烃会直接影响催化剂性能[39]。例如，共轭芳烃中 C=C 键的线性增加与催化剂失活直接相关[34]。通过荧光发射最大值位移识别出的更大、更类似石墨的焦炭物种，表明失活程度加剧[20]。与 HZSM-5 上形成的高序石墨碳相比，微介孔沸石催化剂产生的低序石墨碳会影响失活速率[25]。即使在相对较低的焦炭负载量下，微孔体积和 BET 表面积的快速下降也凸显了高度缩合的石墨化焦炭在阻碍催化活性中的关键作用[21]。

Coke composition is inherently linked to its formation mechanism and direct impact on catalyst deactivation. Coke formation often initiates from precursors that undergo oligomerization, alkylation, and cross-linking to form complex PAHs [44]. These precursors can include aromatic hydrocarbons within pores and long-chain saturated hydrocarbons on the outer surface [45]. Metallic contaminants (e.g., Fe, Ni, V) in heavy oil can catalyze dehydrogenation, accelerating the formation of polyaromatic coke that leads to pore blockage and deactivation [33]. Coke can deposit in various locations within the catalyst structure, from internal pores (e.g., in SAPO-34 after precoking, leading to decreased micropore volume) to sinusoidal and straight channels (e.g., in ZSM-5, where PAHs form in straight channels and C–O/C–C bonds in sinusoidal channels) [39,48]. The evolution of coke morphology from irregular forms to solid, spherical structures, along with a decrease in oxygen-containing functional groups, signifies increased carbon content and exacerbated deactivation [16]. The formation of coke agglomerates, identified as clusters of 30–60 carbon atoms, further illustrates the physical growth of deactivating species [43]. Ultimately, the accumulation of these carbonaceous deposits, particularly the more condensed and graphitic forms, blocks access to active sites and pores, thereby reducing catalytic efficiency and accelerating deactivation.
积炭组成与其形成机制及对催化剂失活的直接影响密切相关。积炭形成通常始于前驱体，通过低聚、烷基化和交联反应形成复杂的多环芳烃（PAHs）[44]。这些前驱体可包括孔道内的芳香烃和外表面的长链饱和烃[45]。重油中的金属杂质（如 Fe、Ni、V）会催化脱氢反应，加速形成导致孔道堵塞和失活的多环芳烃积炭[33]。积炭可沉积在催化剂结构的不同位置——从内部孔道（如 SAPO-34 预积炭后微孔体积减少）到正弦通道与直形通道（如 ZSM-5 中多环芳烃在直形通道形成，而 C-O/C-C 键在正弦通道生成）[39,48]。积炭形貌从不规则形态演变为固态球状结构，同时含氧官能团减少，表明碳含量增加且失活加剧[16]。 焦炭聚集体的形成，即由 30-60 个碳原子组成的团簇，进一步阐明了失活物种的物理生长过程[43]。最终，这些碳质沉积物（尤其是更为稠密和石墨化的形态）的积累会阻塞活性位点和孔道，从而降低催化效率并加速失活。

2.3 Temporal Evolution and Quantification of Coke
2.3 焦炭沉积的时间演变与定量分析

The quantification of coke formation on zeolite catalysts is critical for understanding deactivation mechanisms and designing robust catalytic processes. Various analytical techniques are employed, including thermogravimetric analysis (TGA) [3,6,7,17,19,21,22,28,31,38,39,48,49], thermogravimetric analysis coupled with differential scanning calorimetry (TG-DSC) [31,36], elemental analysis, and temperature-programmed oxidation (TPO) [13,22,24]. Gravimetric methods are also utilized [37].
对沸石催化剂上焦炭形成的定量分析对于理解失活机制和设计稳健的催化过程至关重要。目前采用的分析技术包括热重分析（TGA）[3,6,7,17,19,21,22,28,31,38,39,48,49]、热重-差示扫描量热联用（TG-DSC）[31,36]、元素分析以及程序升温氧化（TPO）[13,22,24]，此外也采用重量分析法[37]。

图 Temporal Evolution of Coke Deposition
图 焦炭沉积的时间演变

The temporal evolution of coke deposition exhibits diverse patterns depending on the reaction system and zeolite type. Deactivating species initiate formation at the very onset of the reaction [21]. For instance, in SAPO-34, the coke content was found to increase from 2.5 wt% at 5 minutes to 15.8 wt% at 96 minutes of reaction time, with a significant decrease in methanol conversion observed when coke exceeded 8.1 wt% [19]. Similarly, ZSM-5 catalysts showed an increase in coke content from 3.0 wt% at 1 hour to 10.2 wt% at 19.5 hours during methanol-to-hydrocarbons (MTH) conversion [39]. Initially, coke accumulation can be rapid or even exponential, followed by a deceleration. For β-zeolite, coke content increases exponentially in the initial 0–30 minutes, after which the coking rate decreases [30]. Likewise, for ZSM-5, the majority of coke build-up occurs within the first 20 minutes, with the deposition rate subsequently slowing down [47]. This behavior sometimes suggests an initial autocatalytic coking rate, as observed in dimethyl ether (DME) conversion over SAPO-34, where the coking rate increased with coke content during the early stages, with a saturated coke content of about 5.3 wt% [7]. Other studies note that coke content can increase linearly with time-on-stream until breakthrough, after which the accumulation rate levels off, as seen for ZSM-5 in MTH reactions [21]. In some cases, coke content can fluctuate around a saturation point, such as 9–10.3 wt% C after multiple reuses of industrial ZSM-5 catalysts [10].
积炭沉积的时间演化特征因反应体系和分子筛类型而异。失活物种在反应初始阶段即开始形成[21]。例如，在 SAPO-34 分子筛中，积炭含量从反应 5 分钟时的 2.5 wt%增至 96 分钟时的 15.8 wt%，当积炭超过 8.1 wt%时甲醇转化率显著下降[19]。类似地，ZSM-5 催化剂在甲醇制烃(MTH)反应过程中，积炭含量从 1 小时的 3.0 wt%增加至 19.5 小时的 10.2 wt%[39]。初始阶段积炭可能快速甚至呈指数增长，随后增速减缓。β分子筛在反应前 0-30 分钟内积炭呈指数增长，之后结焦速率下降[30]。同样对于 ZSM-5，大部分积炭形成于前 20 分钟内，随后沉积速率逐渐降低[47]。 这种现象有时表明初始焦化速率是自催化的，正如在 SAPO-34 上二甲醚（DME）转化过程中所观察到的，焦化速率在早期随焦炭含量增加而增加，饱和焦炭含量约为 5.3 wt% [7]。其他研究指出，焦炭含量可以随在线时间线性增加直至穿透，此后累积速率趋于平稳，如 ZSM-5 在 MTH 反应中所示 [21]。在某些情况下，焦炭含量可能在饱和点附近波动，例如工业 ZSM-5 催化剂多次重复使用后，焦炭含量为 9–10.3 wt% C [10]。

A crucial aspect of temporal evolution is the transformation of coke species. Initially formed “soft coke” (low molecular weight, amorphous, readily combustible) tends to convert into “hard coke” (high molecular weight, graphitic, more difficult to remove) with increasing reaction time. The
时间演变的一个关键方面是焦炭物种的转化。最初形成的“软焦”（低分子量、无定形、易燃）倾向于随着反应时间的增加转化为“硬焦”（高分子量、石墨化、更难去除）。

Coke formation is intricately linked to reaction conditions and directly impacts catalyst performance. Higher reaction temperatures and increased reactant partial pressures generally lead to higher coking rates [7]. However, in some cases, increasing the reaction temperature from 350 to 425 °C can lead to a decrease in coke deposition, attributed to cracking of coke intermediates and increased water flow as a reaction product [18]. Feed composition also plays a significant role; light olefins lead to higher coke content (up to 9.68 wt%) compared to paraffins, and aromatics can have synergistic coking effects when co-fed with olefins [30]. The addition of ethanol, for instance, can increase coke accumulation substantially, from 30.5 mg g⁻¹₍cat₎ to 70.4 mg g⁻¹₍cat₎ with 20 wt% ethanol addition in n-heptane catalytic cracking [36]. The presence of formaldehyde in the feed also leads to higher coke content at similar residual conversion levels [34].
焦炭的形成与反应条件错综复杂地联系在一起，并直接影响催化剂性能。通常，较高的反应温度和增加的反应物分压会导致更高的焦化率[7]。然而，在某些情况下，将反应温度从 350℃提高到 425℃反而会降低焦炭沉积，这归因于焦炭中间体的裂解和作为反应产物的水流量增加[18]。进料组成也起着重要作用；与石蜡相比，轻质烯烃导致更高的焦炭含量（高达 9.68 wt%），并且当与烯烃共同进料时，芳烃可能具有协同焦化效应[30]。例如，在正庚烷催化裂化中，添加乙醇可以显著增加焦炭积累，从 30.5 mg g⁻¹₍cat₎增加到 70.4 mg g⁻¹₍cat₎（添加 20 wt%乙醇）[36]。进料中甲醛的存在也导致在相似的残余转化水平下焦炭含量更高[34]。

The “burning cigar” model, which describes a deactivation front propagating through the catalyst bed, is a relevant concept. Studies confirm spatial variations in deactivation, with catalyst beds often separated into top, middle, and bottom layers to evaluate the degree of deactivation along the bed [17]. At a more localized scale, coke concentrations are often highest near the catalyst surface and decrease towards the center of the crystal [6,43], supporting the concept of a progressing deactivation front, whether macroscopic or within individual catalyst particles.
描述失活前沿在催化剂床层中传播的“燃烧雪茄”模型是一个相关概念。研究证实了失活的空间变化，催化剂床层通常被分为顶部、中部和底部，以评估沿床层的失活程度[17]。在更局部的尺度上，焦炭浓度通常在催化剂表面附近最高，并向晶体中心降低[6,43]，这支持了无论是宏观还是在单个催化剂颗粒内部，失活前沿都在推进的概念。

The SiO₂/Al₂O₃ ratio of zeolite catalysts significantly influences coke formation and deactivation rates. A higher SiO₂/Al₂O₃ ratio generally leads to lower coke formation, as demonstrated by nanocrystal ZSM-5 catalysts where coke content decreased from 3.3 wt% for NZ 23 to 0.1 wt% for NZ 411 as the ratio increased [49]. This suggests that tuning the acid site density can modulate the propensity for coke formation.
沸石催化剂的 SiO₂/Al₂O₃比显著影响焦炭形成和失活速率。较高的 SiO₂/Al₂O₃比通常导致较低的焦炭形成，纳米晶 ZSM-5 催化剂的研究表明，随着该比值的增加，焦炭含量从 NZ 23 的 3.3 wt%降至 NZ 411 的 0.1 wt%[49]。这表明调节酸位密度可以改变焦炭形成的倾向。

Coke deposition directly correlates with the deterioration of catalyst textural properties and activity. As coke accumulates, it leads to active site fouling and pore blocking, reducing catalytic conversion [29]. For
焦炭沉积与催化剂结构性质和活性的恶化直接相关。随着焦炭的积累，会导致活性位点污染和孔道堵塞，从而降低催化转化率[29]。对于

2.4 Impact on Catalyst Properties
2.4 对催化剂性能的影响

Coke deposition profoundly impacts the physicochemical properties of zeolite catalysts, primarily leading to a reduction in the accessibility of active sites and a hindrance to the diffusion of reactants and products within the zeolite structure, which collectively diminish catalytic activity and alter selectivity.
焦炭沉积深刻影响沸石催化剂的物理化学性质，主要表现为活性位点可及性降低，阻碍反应物和产物在沸石结构内的扩散，这些因素共同导致催化活性下降并改变反应选择性。

One primary mechanism of deactivation involves the coverage and poisoning of active sites. Carbonaceous deposits directly adsorb onto and block catalytic active centers, such as Brønsted and Lewis acid sites, rendering them inaccessible for catalysis [5,29,33,43,49]. Studies consistently show a significant reduction in acidity upon coking. For instance, in HZSM-5, both weak and strong acid sites are substantially reduced, with acid strengths diminishing to the extent that the desorption peak for strong acid sites can disappear [45]. Strong acid sites, particularly those located within micropores, are more susceptible to damage and blocking by coke [30,35]. Specifically, Brønsted acid sites are heavily impacted, with industrial ZSM-5 catalysts exhibiting up to a 99% loss after five pyrolysis runs, while Lewis sites show minimal impact in such scenarios [10]. Similarly, coke deposition preferentially blocks acid sites with strength above
催化剂失活的一个主要机制涉及活性位点的覆盖与中毒。碳质沉积物直接吸附并堵塞催化活性中心，如布朗斯特和路易斯酸位点，使其无法参与催化反应[5,29,33,43,49]。研究一致表明积炭会导致酸度显著降低。例如在 HZSM-5 分子筛中，弱酸位点和强酸位点均大幅减少，酸强度减弱程度甚至可使强酸位点的脱附峰完全消失[45]。位于微孔内的强酸位点尤其容易受到积炭的破坏和堵塞[30,35]。具体而言，布朗斯特酸位点受影响最为严重，工业 ZSM-5 催化剂在五次裂解反应后损失率高达 99%，而相同条件下路易斯位点几乎不受影响[10]。同样地，积炭沉积会优先堵塞酸强度高于

The second major mechanism is the physical blockage of the zeolite pore network, which impedes mass transfer. Coke deposition causes a significant reduction in the total surface area and pore volume, including both micropores and mesopores, although micropores are typically more severely affected [22,24,44,47]. For instance, ZSM-5 micropore volume can decrease from 0.12 to 0.07
第二种主要机制是沸石孔道网络的物理堵塞，这会阻碍传质过程。焦炭沉积导致包括微孔和中孔在内的总表面积和孔体积显著减少，其中微孔通常受影响更为严重[22,24,44,47]。例如 ZSM-5 的微孔体积可从 0.12 降至 0.07

This pore blockage directly results in hindered diffusion of reactants and products, creating severe mass transport limitations. Bulky coke species, especially when localized in the internal pores or shell layers of crystals, reduce the accessibility of inner acidic sites by physically obstructing the diffusion pathways [9,19]. This is evidenced by a decrease in the self-diffusion coefficients of small molecules like methane and ethene with increasing coke amounts [19]. Internal coke formation is particularly detrimental, as it more efficiently blocks the catalytically active micropores even at low coking levels compared to external coke [38]. The growth of smaller coke compounds into larger, graphite-like species with longer time on stream (TOS) can specifically block sinusoidal zeolite micropores [20]. These diffusion limitations mean that reactants struggle to reach active sites, and products are hindered in exiting the catalyst, leading to a decrease in overall reaction rates and accumulation of adsorbed species on the catalytic surface [28,46].
这种孔道堵塞直接导致反应物和产物的扩散受阻，造成严重的传质限制。大体积焦炭物种（尤其是积聚在晶体内部孔道或壳层时）会通过物理阻碍扩散通道来降低内部酸性位点的可及性[9,19]。甲烷和乙烯等小分子自扩散系数随积炭量增加而降低的现象证实了这一点[19]。内部积炭的形成危害尤为严重，因为与外部积炭相比，即使在低积炭水平下，它也能更高效地阻塞具有催化活性的微孔[38]。随着运行时间(TOS)延长，较小焦炭化合物逐渐生长为更大的类石墨物质，会特异性堵塞正弦曲线状沸石微孔[20]。这些扩散限制意味着反应物难以到达活性位点，产物也难以离开催化剂，最终导致整体反应速率下降及催化表面吸附物种的累积[28,46]。

The cumulative effect of active site reduction and pore blockage is a marked decrease in catalytic activity and altered selectivity. The deactivation is manifested as a declining conversion over time, as seen in m-cresol alkylation [29]. In cracking and deoxygenation reactions, decreased activity is directly linked to these coke-induced changes [24]. Selectivity can also shift; for instance, in the Prins reaction, pore blockage leads to a decrease in overall conversion but an increase in the selectivity towards 3-buten-1-ol and buta-1,3-diene [31]. In catalytic co-pyrolysis, catalyst deactivation leads to a decrease in aromatic formation and a breakthrough of non-catalytic products like oxygenates, alkanes, and alkenes [37]. While the zeolite's crystalline structure often remains intact even at high coke levels, some studies report subtle structural changes, such as a contraction along the a-axis and elongation along the b-axis in ZSM-5, correlating with internal coke content and deactivation [17,34,39]. Furthermore, the formation of coke can induce structural distortion in the alumina framework, leading to increased octahedral and penta-coordinated alumina sites [6]. The granule size of zeolite can also increase due to coke coverage, further affecting overall performance [45]. These systematic changes in catalyst properties underscore the intricate relationship between coke deposition and the resultant loss of performance in zeolite-catalyzed reactions.
活性位点减少与孔道堵塞的累积效应导致催化活性显著下降及选择性改变。失活表现为随时间推移转化率持续降低，如间甲酚烷基化反应所示[29]。在裂解和脱氧反应中，活性下降与焦炭引发的这些变化直接相关[24]。选择性也可能发生偏移：例如在 Prins 反应中，孔道堵塞导致总转化率下降，但对 3-丁烯-1-醇和丁二烯-1,3 的选择性却有所提升[31]。催化共热解过程中，催化剂失活会造成芳烃产物减少，并出现含氧化合物、烷烃和烯烃等非催化产物的穿透现象[37]。虽然沸石的晶体结构在高积碳条件下通常保持完整，但部分研究报道了细微的结构变化——如 ZSM-5 分子筛沿 a 轴收缩与 b 轴伸长，这种变化与内部积碳含量及失活程度存在关联[17,34,39]。此外，焦炭形成还可能引发氧化铝骨架结构畸变，导致八面体和五配位铝位点数量增加[6]。 沸石颗粒尺寸也可能因积炭覆盖而增大，进一步影响整体性能[45]。催化剂性质的这些系统性变化揭示了积炭沉积与沸石催化反应性能下降之间复杂的关联关系。

3. Mechanisms of Coking Deactivation
3. 积炭失活机制

Coking deactivation represents a critical challenge in zeolite catalysis, profoundly impacting catalyst longevity and process efficiency across various industrial applications. Understanding the intricate mechanisms governing coke formation is paramount for designing robust catalysts and optimizing catalytic processes. This section comprehensively evaluates the diverse proposed mechanisms of coking deactivation, critically examining the evidence supporting each, and considering the specific reaction environments, zeolite structures, and operating conditions under which they manifest. Furthermore, it delves into the individual and synergistic contributions of different types of active sites to coke formation, analyzing how their density and distribution dictate the rate and selectivity of coking reactions.
积炭失活是沸石催化领域面临的关键挑战，深刻影响着各类工业应用中催化剂的寿命和工艺效率。理解积炭形成的复杂机制对于设计高稳定性催化剂和优化催化工艺至关重要。本节系统评估了多种积炭失活的可能机制，批判性地审视了支持每种机制的实验证据，并考察了其发生的特定反应环境、沸石结构和操作条件。此外，还深入探讨了不同类型活性位点对积炭形成的单独及协同作用，分析其密度和分布如何决定积炭反应的速率和选择性。

The formation of coke is a complex sequence of successive chemical transformations, fundamentally involving the conversion of reactant molecules or reactive intermediates into increasingly condensed, carbonaceous deposits that ultimately impede catalyst activity [22,30,36,40]. These pathways typically encompass elementary steps such as oligomerization, cyclization, aromatization, and dehydrogenation, leading to the formation of polycyclic aromatic hydrocarbons (PAHs) [9,22,44]. Predominant mechanistic frameworks include the alkene-driven mechanism, where highly reactive olefins (often formed through initial dehydrogenation or cracking) undergo extensive oligomerization, alkylation, and aromatization to form coke, as observed in n-heptane cracking and fluid catalytic cracking (FCC) processes [15,28,32,36]. Conversely, in methanol-to-hydrocarbons (MTH) and methanol-to-olefins (MTO) processes, the hydrocarbon pool (HCP) mechanism is central, where polyalkyl aromatics act as both active intermediates and crucial precursors for coke deposition [4,7,34,39,41]. The specific zeolite structure and its shape selectivity play a critical role, dictating the confinement and growth of these carbonaceous species within the catalyst pores [7,15,19,39].
积碳的形成是一系列复杂的连续化学转化过程，其本质是反应物分子或活性中间体逐步转化为高度缩合的碳质沉积物，最终导致催化剂失活[22,30,36,40]。该过程通常包含低聚、环化、芳构化和脱氢等基元反应步骤，最终形成多环芳烃（PAHs）[9,22,44]。主要机理框架包括：烯烃驱动机制（在正庚烷裂解和流化催化裂化（FCC）过程中观察到）——高活性烯烃（通常通过初始脱氢或裂解形成）经深度低聚、烷基化和芳构化形成积碳[15,28,32,36]；而在甲醇制烃类（MTH）和甲醇制烯烃（MTO）过程中，烃池（HCP）机制起主导作用——多烷基芳烃既作为活性中间体，又成为积碳沉积的关键前驱体[4,7,34,39,41]。 特定沸石结构及其形状选择性起着关键作用，决定了这些碳质物种在催化剂孔道内的限域与生长[7,15,19,39]。

The nature, density, and accessibility of active sites on zeolite catalysts are fundamental determinants of the rate and selectivity of coke formation [40,45]. Both Brønsted acid sites (BAS) and Lewis acid sites (LAS) contribute to coke deposition, albeit through distinct mechanisms and with varying susceptibilities to deactivation. BAS, through proton donation, are instrumental in catalyzing oligomerization and subsequent coke formation, especially strong BAS, which are frequently blocked by coke [24,32]. Conversely, LAS can initiate coke growth by abstracting hydrides from alkanes, forming carbenium ions [14,32]. High concentrations of strong acid sites typically accelerate the formation of coke precursors [15,49]. Furthermore, the nanoscale distribution of active sites directly correlates with coke formation, with higher coke densities observed around regions of elevated aluminum content and crystal surface steps [2,43]. The presence of metal additives significantly influences coking, with some (e.g., Pt) promoting coke precursor hydrogenation and suppression, while others (e.g., Zn, Fe, Mo) can either enhance desired reactions or promote side reactions leading to coke formation through their unique catalytic properties and interactions with acid sites [1,9,25,28,29].
沸石催化剂上活性位点的性质、密度及可接近性是焦炭形成速率与选择性的根本决定因素[40,45]。布朗斯特酸位(BAS)和路易斯酸位(LAS)均会促进焦炭沉积，但通过不同机制且具有差异化的失活敏感性。BAS 通过质子转移催化低聚反应及后续焦炭形成，其中强 BAS 尤其容易被焦炭阻塞[24,32]；而 LAS 则可通过从烷烃中夺取氢负离子形成碳正离子来引发焦炭生长[14,32]。高浓度强酸位通常会加速焦炭前驱体的形成[15,49]。此外，活性位点的纳米级分布与焦炭形成直接相关，在铝含量较高区域和晶体表面台阶处可观察到更高的焦炭密度[2,43]。 金属添加剂的存在显著影响结焦，其中一些（例如，Pt）促进焦炭前体加氢和抑制，而另一些（例如，Zn、Fe、Mo）则通过其独特的催化性能以及与酸性位点的相互作用，既可以促进目标反应，也可以促进导致焦炭形成的副反应[1,9,25,28,29]。

Kinetic studies are indispensable for quantitatively describing and predicting coke formation and catalyst deactivation. Various models, such as the Voorhies correlation or more complex multi-parameter equations, are employed to characterize coke accumulation over time, often revealing distinct stages or rate dependencies [7,30]. Theoretical approaches, particularly Density Functional Theory (DFT) calculations, provide critical insights into the energetics and rate-limiting steps of coke precursor formation, detailing the free energy barriers for crucial coupling, cyclization, and hydrogen transfer reactions that underpin coke growth [41,44]. Catalyst deactivation kinetics are frequently described using deactivation functions within overall kinetic models, such as the LHHW or Janssens models, which quantify activity decay due to active site fouling and pore blocking [1,29,38]. The order of the deactivation reaction can further elucidate the number of active sites involved in the deactivation event, distinguishing between single-site and multi-site deactivation mechanisms [1,31].
动力学研究对于定量描述和预测积炭形成及催化剂失活至关重要。研究者采用多种模型（如 Voorhies 关联式或更复杂的多参数方程）来表征积炭随时间累积的特性，这些模型常能揭示不同的积炭阶段或速率依赖关系[7,30]。理论研究方法，特别是密度泛函理论（DFT）计算，为积炭前驱体形成的能量学及限速步骤提供了关键见解，详细阐明了支撑积炭生长的关键偶联、环化和氢转移反应的自由能垒[41,44]。催化剂失活动力学通常采用整体动力学模型中的失活函数进行描述，例如 LHHW 模型或 Janssens 模型，这些模型可量化因活性位点毒害和孔道堵塞导致的活性衰减[1,29,38]。失活反应级数可进一步阐明参与失活事件的活性位点数量，从而区分单一位点与多位点失活机制[1,31]。

In summary, the mechanisms of coking deactivation are profoundly intertwined, with coke formation pathways dictated by reactant chemistry and zeolite topology, catalyzed by specific active sites whose characteristics critically influence the rate and selectivity, and quantified by kinetic models that describe the overall deactivation process. A key challenge remains in fully deciphering the complex interplay between reaction-specific precursor generation, the precise roles of different acid sites and their synergistic effects, and the evolving physical properties of the growing coke. Future research should prioritize multi-modal experimental techniques combined with advanced computational modeling to achieve a more holistic and predictive understanding of coking, enabling the rational design of more coke-resistant zeolite catalysts.
总之，结焦失活机制错综复杂：焦炭形成路径受反应物化学性质与沸石拓扑结构共同支配，由特定活性位点催化——这些位点的特性对反应速率和选择性具有决定性影响，并通过描述整体失活过程的动力学模型进行量化。当前的核心挑战在于全面解析反应特异性前驱体生成、不同酸性位点的精确作用及其协同效应、以及生长中焦炭物理性质动态演变之间的复杂相互作用。未来研究应优先采用多模态实验技术结合先进计算建模方法，以建立更具整体性和预测性的结焦认知体系，从而为理性设计抗结焦沸石催化剂提供理论基础。

3.1 Coke Formation Pathways
3.1 焦炭形成路径

Coke formation on zeolite catalysts is a complex process involving a series of successive reactions, fundamentally rooted in the conversion of reactant molecules into increasingly condensed, carbonaceous deposits that ultimately deactivate the catalyst. These pathways vary depending on the reaction type, feedstock, and zeolite structural properties, but generally involve common elementary steps such as oligomerization, cyclization, aromatization, and dehydrogenation, leading to the formation of polycyclic aromatic hydrocarbons (PAHs) [22,36,49].
沸石催化剂上的积炭形成是一个复杂过程，涉及一系列连续反应，其本质是反应物分子逐步转化为高度缩合的碳质沉积物，最终导致催化剂失活。这些反应路径因反应类型、原料及沸石结构特性而异，但通常包含低聚、环化、芳构化和脱氢等共同基元步骤，最终形成多环芳烃(PAHs)[22,36,49]。

A prominent pathway observed in many catalytic processes is the alkene-driven mechanism. In reactions such as n-heptane catalytic cracking, long-chain n-alkanes are initially dehydrogenated to form olefin intermediates, which then undergo skeletal isomerization or chain scission [22]. These olefins are highly reactive and prone to successive reactions including oligomerization, alkylation, isomerization, cyclization, aromatization, and dehydrogenation, culminating in coke formation [36]. For instance, the oligomerization of olefins produced during the isomerization of endo-tetrahydrodicyclopentadiene (THDCPD) has been identified as a direct route to coke formation, where carbenium ion intermediates undergo further side reactions like β-scission and hydrogen transfer to generate various olefin species [28]. Similarly, in fluid catalytic cracking (FCC), coke formation can initiate from small C3 and C4 molecules through alkylation, isomerization, ring closure, and dehydrogenation, following reaction schemes proposed by Guisnet and Magnoux [18,40]. The initial stages of FCC also involve thermal (radical) cracking on the outer catalyst surface, with carbenium ions forming and subsequently cracking via β-scission [32]. Alkanes can be cracked into C6- olefins, which then oligomerize to C6+ olefins. Subsequent hydrogen transfer reactions form diolefins that oligomerize into naphthenes, eventually forming aromatics through isomerization and further hydrogen transfer steps [33].
在许多催化过程中观察到的一种主要途径是烯烃驱动机制。在正庚烷催化裂化等反应中，长链正构烷烃首先脱氢形成烯烃中间体，然后发生骨架异构化或断链[22]。这些烯烃具有高反应活性，易发生连续反应，包括低聚、烷基化、异构化、环化、芳构化和脱氢，最终导致焦炭形成[36]。例如，内型四氢二环戊二烯（THDCPD）异构化过程中产生的烯烃的低聚已被确定为焦炭形成的直接途径，其中碳正离子中间体发生进一步的副反应，如β-断裂和氢转移，生成各种烯烃物种[28]。类似地，在流化催化裂化（FCC）中，焦炭的形成可以从小 C3 和 C4 分子通过烷基化、异构化、闭环和脱氢开始，遵循 Guisnet 和 Magnoux 提出的反应方案[18,40]。 FCC 的初始阶段还涉及催化剂外表面的热（自由基）裂解，碳正离子形成后通过β-断裂进一步裂解[32]。烷烃可以裂解成 C6-烯烃，然后聚合成 C6+烯烃。随后的氢转移反应形成二烯烃，二烯烃聚合成环烷烃，最终通过异构化和进一步的氢转移步骤形成芳烃[33]。

For methanol-to-hydrocarbons (MTH) and methanol-to-olefins (MTO) processes, the hydrocarbon pool (HCP) mechanism is central to both product formation and coke deposition. Methanol is first dehydrated to dimethyl ether (DME), which then reacts to form primary products that undergo oligomerization, cyclization, aromatization, aromatic methylation, hydrogen transfer, and aromatic dealkylation [49]. In this mechanism, polyalkyl aromatics, formed on Brønsted acid sites, serve a dual role: they are critical active intermediates for the catalytic cycle and also significant precursors for coke formation [4,7]. Ethene and propene molecules, generated within the HCP, undergo oligomerization and deprotonation to form larger species. Subsequent hydride transfer reactions and cyclization lead to the formation of cyclic compounds such as methylcyclopropane carbenium ions, cyclopentene, methylcyclopentadiene, and eventually benzene through successive hydride transfer reactions [41]. Cyclo-dienes and methylbenzenes (MBs) are identified as important precursors for the formation of di- and polycyclic aromatics, with alkylation and/or crosslinking of these cyclic species being a crucial route for PAH formation [44]. Smaller
在甲醇制烃类（MTH）和甲醇制烯烃（MTO）工艺中，烃池（HCP）机制对产物形成与积炭沉积均具有核心作用。甲醇首先脱水生成二甲醚（DME），随后通过反应形成初级产物，这些产物经历齐聚、环化、芳构化、芳烃甲基化、氢转移及芳烃脱烷基等过程[49]。该机制中，布朗斯特酸位上形成的多烷基芳烃具有双重功能：既是催化循环的关键活性中间体，也是积炭形成的重要前驱体[4,7]。烃池内生成的乙烯和丙烯分子通过齐聚和去质子化形成更大分子，后续的氢转移反应与环化作用导致甲基环丙烷碳正离子、环戊烯、甲基环戊二烯等环状化合物的形成，并最终通过连续氢转移反应生成苯[41]。 环二烯和甲基苯（MBs）被确认为形成双环及多环芳烃的重要前驱体，这些环状化合物的烷基化和/或交联反应是生成多环芳烃的关键路径[44]。较小的

In biomass upgrading, coke formation pathways are influenced by the oxygenated nature of the feedstocks. Biomass pyrolysis produces anhydrosugars and other small oxygenated molecules, which can dehydrate to furans, particularly on Brønsted acid sites of zeolites like HZSM-5 [37]. These oxygenates undergo further deoxygenation to various olefins that feed into the hydrocarbon pool, acting as precursors to aromatics [37]. Smaller aromatics and cracked species can enter zeolite pores, forming one or two-ring aromatic compounds through deoxygenation, oligomerization, and hydrogen transfer. These compounds can then polymerize to larger aromatics, gradually covering acid sites and forming primary coke [45]. The coke originating from lignin, for example, forms primarily on the catalyst external surface via condensation of pyrolytic monomers and oligomers or the formation of a phenolic pool. In contrast, coke from cellulose is attributed to the formation of multiring aromatics on active sites, leading to micropore blocking [12].
在生物质升级过程中，焦炭形成路径受原料含氧特性的显著影响。生物质热解会生成脱水糖类及其他小分子含氧化合物，这些物质在 HZSM-5 等沸石的布朗斯特酸位点上易脱水转化为呋喃类化合物[37]。此类含氧组分通过进一步脱氧反应生成多种烯烃，成为芳烃前驱体并参与碳氢化合物池反应[37]。小分子芳烃及裂解产物可进入沸石孔道，经脱氧、低聚和氢转移反应形成单环或双环芳烃化合物。这些化合物通过聚合反应逐渐生成大分子芳烃，覆盖酸性位点并形成初级焦炭[45]。以木质素来源的焦炭为例，其主要通过热解单体/低聚物缩合或酚类池反应在催化剂外表面形成；而纤维素衍生的焦炭则源于活性位点上多环芳烃的生成，最终导致微孔堵塞[12]。

The role of zeolite structure and its acid sites is critical in directing coke formation. Coke formation generally follows a sequence where wax molecules, often formed via thermal cracking, enter zeolite pores and react at acid sites through carbocation mechanisms [15]. The shape selectivity of the zeolite then dictates the growth and condensation of these coke precursors [15]. For instance, in SAPO-34, whose pore size is smaller than benzene, polyalkyl aromatics larger than benzene are confined within the cages, leading to their accumulation and subsequent conversion into coke [7]. Acid sites also catalyze condensation and hydrogen transfer reactions that lead to hard coke, characterized by polycyclic aromatic structures [35].
沸石结构及其酸性位点在引导积炭形成过程中起着关键作用。积炭形成通常遵循以下序列：蜡质分子（常通过热裂解产生）进入沸石孔道，在酸性位点上通过碳正离子机制发生反应[15]。随后沸石的形状选择性决定了这些积炭前驱体的生长和缩合过程[15]。以 SAPO-34 为例，其孔径小于苯环尺寸，导致大于苯环的多烷基芳烃被限制在笼状结构中，进而发生积累并最终转化为积炭[7]。酸性位点还会催化缩合和氢转移反应，形成以多环芳烃结构为特征的重质积炭[35]。

Other specific coke formation pathways include the condensation of aldehyde-ketone species followed by cyclization reactions of intermediate products, as seen in the conversion of ethanol to butadiene [14]. In propane aromatization, coke formation can involve free radical activation pathways where alkenes are generated through C-H bond breaking on dehydrogenation sites or by migration of carbon radicals to nearby Brønsted acid sites. These olefins can oligomerize into long-chain olefins, which, under high temperatures and strong acid sites, form aliphatic coke through continuous oligomerization and excessive dehydrogenation. Alternatively, long-chain hydrocarbons can cyclize into unsaturated cyclic olefins, leading to either condensation into PAHs or dehydrogenation into lighter aromatic products, depending on the presence of metal sites [9]. Formaldehyde, if present, can react with alkenes via Prins and hydroacylation reactions to yield dienes and polyenes, which readily undergo cyclization and hydrogen transfer to form arenes, further contributing to deactivating species like diphenylmethane [34].
其他特定的积炭形成途径包括醛酮类物质的缩合反应及其中间产物的环化反应，这在乙醇转化为丁二烯的过程中已有报道[14]。在丙烷芳构化反应中，积炭形成可能涉及自由基活化路径：通过脱氢位点上的 C-H 键断裂或碳自由基向邻近布朗斯特酸位点迁移生成烯烃。这些烯烃可低聚成长链烯烃，在高温和强酸位点作用下，通过持续低聚和过度脱氢形成脂肪族积炭；或者长链烃类可环化为不饱和环状烯烃，根据金属位点的存在情况，或进一步缩合生成多环芳烃，或脱氢生成轻质芳烃产物[9]。若存在甲醛，其可通过普林斯反应和氢酰化反应与烯烃作用生成二烯和多烯，这些产物极易发生环化和氢转移形成芳烃，进而生成如二苯甲烷等导致催化剂失活的物质[34]。

For deactivation mitigation, targeting several critical steps in these pathways is essential. Inhibiting the excessive oligomerization and dehydrogenation of olefins to prevent the formation of highly condensed PAHs is crucial. Controlling the growth and merging of initial small carbon clusters into larger coke structures represents another key area [43]. In processes involving the hydrocarbon pool, managing the balance between the productive pathways of HCP species (e.g., formation of light olefins) and their conversion into bulky, trapped polyaromatics is paramount [41,44]. Modifying zeolite pore architecture to prevent the confinement and subsequent condensation of large aromatic precursors, especially within smaller pores, could also mitigate coke formation [7].
为缓解失活问题，针对这些路径中的几个关键环节至关重要。抑制烯烃过度低聚和脱氢以防止形成高度缩合的多环芳烃尤为关键。控制初始小碳簇生长并聚集成更大焦炭结构是另一关键领域[43]。在涉及烃池的反应过程中，调控 HCP 物种的生成路径（如轻质烯烃形成）与其转化为大体积滞留多环芳烃之间的平衡至关重要[41,44]。通过调整分子筛孔道结构来防止大分子芳烃前驱体的限域及后续缩合（尤其在较小孔道内），也可有效抑制积焦[7]。

3.2 Role of Active Sites
3.2 活性位点作用

The nature, density, and accessibility of active sites on zeolite catalysts fundamentally dictate the rate and selectivity of coke formation, consequently influencing catalyst deactivation. Research indicates that both Brønsted acid sites (BAS) and Lewis acid sites (LAS) contribute to coke deposition, albeit through distinct mechanisms and with varying susceptibilities to deactivation [40,45].
分子筛催化剂上活性位点的性质、密度和可及性从根本上决定了积焦的速率和选择性，进而影响催化剂失活。研究表明，布朗斯特酸位（BAS）和路易斯酸位（LAS）均会促进积焦沉积，但其作用机制不同且对失活的敏感性存在差异[40,45]。

The type of acid site plays a critical role in coke precursor formation. BAS are known to donate protons to alkenes, facilitating oligomerization and subsequent coke formation [28,32]. For instance, the conversion of methanol/dimethyl ether (DME) to olefins (MTO/DMO) relies on co-catalysis by both BAS and the hydrocarbon pool mechanism, where strong BAS are implicated in the formation of coke-inducing intermediates like formaldehyde [7,34]. Conversely, Lewis acid sites can abstract hydrides from alkanes, forming carbenium ion species that also contribute to coke growth [32,40]. The interaction between electrons from nitrogen compounds in heavy oil feedstocks and either LAS or BAS can also promote coke generation [33].
酸位类型对焦炭前驱体形成具有决定性影响。布朗斯特酸位(BAS)可向烯烃提供质子，促进低聚反应及后续焦炭形成[28,32]。例如甲醇/二甲醚(DME)制烯烃(MTO/DMO)过程同时依赖 BAS 和烃池机制的协同催化，其中强 BAS 参与生成如甲醛等诱导焦炭的中间体[7,34]。相反，路易斯酸位(LAS)能从烷烃中夺取氢负离子，形成同样促进焦炭增长的碳正离子物种[32,40]。重油原料中含氮化合物的电子与 LAS 或 BAS 的相互作用也会加剧焦炭生成[33]。

The strength and density of acid sites significantly impact their propensity for coking. Strong acid sites, particularly those with acidic strength above
酸位强度与密度显著影响其结焦倾向。强酸位点（尤其是酸强度超过

There are varying observations regarding which specific acid sites are more prone to coking. Some research suggests strong Lewis acid centers are preferentially covered by carbon deposits, leading to deactivation [14,30]. For instance, tetrahedrally coordinated Zr atoms in Zr-β zeolite, acting as Lewis acid sites, are crucial for ethanol-to-butadiene (ETB) reactions and are susceptible to coking [14]. However, other studies indicate that Brønsted sites, particularly those located within zeolite micropores, are heavily impacted by coking, experiencing significant loss of activity [10]. Hierarchical zeolites with higher mesoporosity and acidity (including more BAS and a higher concentration of strong acid sites) show a notable selectivity of coke towards BAS, resulting in larger coke deposits [47]. In contrast, Lewis sites, often situated on the external surface or alumina binder in mesopores, are less impacted [10]. The sustained formation and accumulation of coke species lead to the coverage of acidic sites and a pronounced reduction in the relative intensity of Brønsted acid sites [19].
关于何种特定酸性位点更易发生结焦，现有研究存在不同观察结果。部分研究表明强路易斯酸中心会优先被积碳覆盖而导致失活[14,30]。例如 Zr-β沸石中四面体配位的 Zr 原子作为路易斯酸位点，在乙醇制丁二烯(ETB)反应中至关重要且易发生结焦[14]。然而其他研究指出，布朗斯特酸位点（尤其是位于沸石微孔内的位点）受结焦影响更为严重，活性显著降低[10]。具有更高介孔率和酸度（包含更多布朗斯特酸位点及高浓度强酸位点）的多级孔沸石中，积碳对布朗斯特酸位点表现出明显选择性，导致更大规模的积碳沉积[47]。相比之下，通常位于外表面或介孔氧化铝粘结剂上的路易斯酸位点受影响较小[10]。焦炭物种的持续形成和积累会导致酸性位点覆盖，并显著降低布朗斯特酸位点的相对强度[19]。

The presence of metal additives profoundly influences coke formation by altering the catalyst's hydrogenation/dehydrogenation capabilities and interacting with existing acid sites. Platinum (Pt) sites, for instance, promote the hydrogenation of coke precursors, thereby effectively suppressing coke formation [28]. Metal carbides, particularly those containing Fe and Mo, act as active sites (MetalCx or MetalCxOy) that facilitate the dehydrogenation of light alkanes into alkyl intermediates, which then dehydrodimerize to olefins. These metal carbide sites are formed on the basis of BAS and maintain a dynamic balance with the total BAS population, indicating a direct interplay between metal and acid sites in coke formation pathways [9]. Zinc (Zn) modification, as seen in Zn-HY zeolites, increases Lewis acidity, which, while enhancing catalytic activity for desired reactions, can also promote side reactions leading to coke [29]. Extraframework zinc ions can also introduce methanol dehydrogenation pathways that lead to formaldehyde formation, a known coke precursor [34]. Furthermore, the bimetallic modification with nickel and molybdenum (NiMo) on micro-mesoporous zeolites can significantly reduce coke yield, as demonstrated by a 33.6% reduction in coke yield in the HAP&NiMo/AZM catalytic system compared to AZM alone, highlighting the beneficial role of specific metal combinations in mitigating deactivation [25]. The deactivation of Ni-Beta zeolite catalysts in ethene dimerization also depends on the density of isolated Ni(II) ions and the active Ni(II)-alkyl sites formed in situ, underscoring the direct involvement of metal active site density in deactivation mechanisms [1]. In essence, metal sites contribute to coke formation and their interactions with acid sites can either accelerate or inhibit coking depending on their inherent properties and the reaction environment [40].
金属添加剂的存在通过改变催化剂的加氢/脱氢能力以及与现有酸性位点的相互作用，对积炭形成产生深远影响。以铂（Pt）位点为例，其能促进焦炭前驱体的加氢反应，从而有效抑制积炭形成[28]。金属碳化物（尤其是含 Fe 和 Mo 的碳化物）作为活性位点（MetalCx 或 MetalCxOy），可促进轻质烷烃脱氢生成烷基中间体，这些中间体继而发生脱氢二聚反应生成烯烃。这些金属碳化物位点以布朗斯特酸位（BAS）为基础形成，并与总 BAS 数量保持动态平衡，表明金属位点与酸性位点在积炭形成路径中存在直接相互作用[9]。锌（Zn）改性（如 Zn-HY 分子筛）会增加路易斯酸性，虽然能提升目标反应的催化活性，但也会促进导致积炭的副反应[29]。骨架外锌离子还可能引入甲醇脱氢路径，形成已知的焦炭前驱体——甲醛[34]。 此外，在微介孔分子筛上进行镍钼双金属（NiMo）改性可显著降低积炭产率，如 HAP&NiMo/AZM 催化体系相比单独 AZM 的积炭产率降低了 33.6%，这凸显了特定金属组合在缓解失活方面的积极作用[25]。Ni-Beta 分子筛催化剂在乙烯二聚反应中的失活程度还取决于孤立 Ni(II)离子的密度及原位形成的活性 Ni(II)-烷基位点，这证实了金属活性位点密度在失活机制中的直接参与[1]。本质上，金属位点会促进积炭形成，而其与酸性位点的相互作用可能加速或抑制积炭过程，具体取决于金属固有特性及反应环境[40]。

3.3 Kinetics of Coke Formation and Deactivation
3.3 积炭形成与失活动力学

4. Factors Influencing Coking Deactivation
4. 影响积炭失活的因素

Coking deactivation is a primary challenge in the industrial application of zeolite catalysts. This challenge stems from a complex interplay of various intrinsic and extrinsic factors that dictate the rate and nature of carbonaceous deposit formation. Understanding these contributing elements is paramount for designing robust catalytic systems and optimizing process conditions to minimize coke accumulation and prolong catalyst lifespan [33,36].
积碳失活是沸石催化剂工业应用中的主要挑战。这一挑战源于多种内在和外在因素的复杂相互作用，这些因素决定了碳质沉积物的形成速率和性质。理解这些影响因素对于设计稳健的催化系统、优化工艺条件以减少积碳积累并延长催化剂寿命至关重要[33,36]。

The inherent zeolite properties play a foundational role in determining susceptibility to coking. These include the zeolite’s framework topology, pore size and channel structure, acidity (both strength and concentration), Si/Al ratio, crystal size, and the presence of mesoporosity or incorporated heteroatoms [3,9,14,15,17,29,32,34,38,39,44,46]. These structural and chemical characteristics govern reactant diffusion, active site accessibility, and the stability of coke precursors—directly influencing coke location and growth.
沸石固有特性在决定积碳敏感性方面起着基础性作用。这些特性包括沸石的骨架拓扑结构、孔径和通道结构、酸性（包括强度和浓度）、硅铝比、晶体尺寸以及介孔性或杂原子掺杂的存在[3,9,14,15,17,29,32,34,38,39,44,46]。这些结构和化学特性决定了反应物扩散、活性位点可及性以及积碳前驱体的稳定性，直接影响积碳的位置和生长。

Beyond the catalyst’s intrinsic nature, reaction conditions are critical determinants of coking kinetics and characteristics. Key parameters such as temperature, pressure, weight hourly space velocity (WHSV), and time-on-stream directly impact coke formation rates and the physical state (e.g., soft vs. hard coke) of the deposits [3,17,24,29,34,35]. The operational environment dictates the reaction pathways, the equilibrium of intermediates, and the removal efficiency of potential coke precursors.
除催化剂本身特性外，反应条件是影响结焦动力学与结焦特征的关键决定因素。温度、压力、重量空速（WHSV）及运行时间等关键参数会直接影响焦炭形成速率及其物理状态（如软焦与硬焦）[3,17,24,29,34,35]。操作环境决定了反应路径、中间体平衡状态以及潜在焦炭前驱体的脱除效率。

The feedstock and reactant properties significantly influence the propensity for coke formation. The specific molecular structures, functional groups, and overall composition of the feed—including the presence of various hydrocarbons (paraffins, olefins, naphthenes, aromatics), oxygenates, and other impurities—govern the availability and reactivity of coke precursors [30,32,33,34,36]. Heavier or more aromatic feedstocks, for instance, generally lead to increased coking [32].
原料与反应物性质对结焦倾向具有显著影响。进料中特定分子结构、官能团及整体组成——包括各类烃类（烷烃、烯烃、环烷烃、芳烃）、含氧化合物及其他杂质的存在——决定了焦炭前驱体的可及性与反应活性[30,32,33,34,36]。例如，重质或高芳烃含量的原料通常会导致更严重的结焦现象[32]。

Furthermore, the strategic incorporation of metal loading and promoters/additives can significantly modulate coking behavior. While some metals can accelerate deactivation by promoting specific coke-forming reactions or through migration and aggregation, others—particularly those with hydrogenation functionalities—can effectively suppress coke formation or improve catalyst stability by modifying acidity or creating new active sites [1,22,28,29,32,33].
此外，金属负载与助剂/添加剂的策略性引入可显著调控积炭行为。某些金属虽会通过促进特定结焦反应或迁移聚集而加速失活，但具有加氢功能的金属则能通过调节酸性或创造新活性位点，有效抑制积炭形成或提升催化剂稳定性[1,22,28,29,32,33]。

Finally,...
最后，...

The following subsections will delve deeper into each of these factors, providing a detailed analysis of their individual contributions and interactions in the context of zeolite coking deactivation.
后续小节将逐一深入剖析这些因素，详细阐释其在分子筛积炭失活中的独立贡献与相互作用机制。

4.1 Zeolite Properties
4.1 分子筛特性

Zeolite properties, including pore size and channel structure, acidity, Si/Al ratio, crystal size, mesoporosity, and heteroatom incorporation, significantly influence coke formation and catalyst deactivation [4,17].
沸石特性，包括孔径与孔道结构、酸性、硅铝比、晶体尺寸、介孔性及杂原子掺杂，对积炭形成及催化剂失活具有显著影响[4,17]。

Pore Architecture and Channel Structures
孔道构型与结构特征

The specific pore architecture and channel topology of zeolites dictate reactant diffusion, product selectivity, and the nature of coke deposition, thereby impacting deactivation rates [4,21,46]. For instance, HZSM-5, with its elliptical pores of approximately 5.0 Å diameter, exhibits shape selectivity to allow compounds up to C10 molecules to enter and leave the zeolite [45]. Its pore topology is noted for enhancing coke stripping, which prolongs catalyst activity [15]. In contrast, SAPO-34, characterized by a tridimensional structure with narrow channels (3.1 Å) connecting larger cavities (6.7–10 Å), often exhibits a higher coke deposition rate compared to HZSM-5 due to its distinct porous structure [18]. The small pore opening and mild acid strength of SAPO-34 contribute to high selectivity for light olefins [7]. Zeolite Y, possessing a 3-D pore system with approximately 7.3 Å pores connecting around 13 Å cages, can trap coke molecules within its supercages, leading to deactivation [15,28,32]. The limited room in the pore system of ZSM-5 makes it more difficult to accommodate larger bimolecular transition states, affecting catalytic outcomes [32].
沸石独特的孔道结构和拓扑构型决定了反应物扩散、产物选择性及积炭特性，进而影响催化剂失活速率[4,21,46]。例如，具有约 5.0 Å椭圆形孔道的 HZSM-5 分子筛表现出形状选择性，允许 C10 以下分子自由进出[45]，其孔道拓扑结构因促进积炭脱除而显著延长催化剂寿命[15]。相比之下，SAPO-34 具有三维骨架结构，其狭窄通道（3.1 Å）连接较大空腔（6.7-10 Å），由于独特的孔结构特性，其积炭速率通常高于 HZSM-5[18]。SAPO-34 的小孔径和适中酸强度使其对轻质烯烃具有高选择性[7]。Y 型分子筛的三维孔道系统包含约 7.3 Å的孔窗和 13 Å的超笼结构，易将积炭分子截留在超笼中导致失活[15,28,32]。ZSM-5 孔道空间有限，较难容纳较大的双分子过渡态，从而影响催化反应结果[32]。

Micropore topology significantly influences the structure and location of coke. Comparisons among different zeolite topologies reveal distinct coking behaviors: the chabazite (CHA) structure (e.g., SSZ-13, SAPO-34) tends to show a more homogeneous carbon distribution than the MFI structure (e.g., ZSM-5), indicating topology-dependent nanoscale coking [2]. In the methanol-to-hydrocarbons (MTH) reaction, ZSM-5 (MFI, with intersecting 10-membered ring straight and sinusoidal channels) demonstrates significantly higher cumulative turnover capacities compared to SSZ-13 (CHA, with 8-membered ring cages) and ZSM-35 (FER, with
微孔拓扑结构显著影响焦炭的结构和位置。不同沸石拓扑结构之间的比较揭示了不同的结焦行为：菱沸石（CHA）结构（例如 SSZ-13、SAPO-34）倾向于显示比 MFI 结构（例如 ZSM-5）更均匀的碳分布，这表明结焦行为具有拓扑结构依赖的纳米尺度特征[2]。在甲醇制烃（MTH）反应中，ZSM-5（MFI，具有交叉的 10 元环直通道和正弦通道）显示出比 SSZ-13（CHA，具有 8 元环笼）和 ZSM-35（FER，具有

Acidity and Si/Al Ratio
酸度和 Si/Al 比

Zeolite acidity, governed by the concentration and strength of acid sites, critically influences the rate and selectivity of coke formation. A direct correlation exists where higher acid strength and increased acid site concentration generally accelerate catalyst deactivation [4]. Strong acid sites are particularly prone to coking [9]. For instance, catalysts with a higher total number of acid sites may exhibit lower activity due to faster deactivation by coke [31]. Conversely, weak acid sites in molecular sieves are generally advantageous for light olefin production and exhibit anti-carbon deposition properties [13]. The zinc-modified HY zeolite's acidity, for example, is a major factor influencing the reaction and, indirectly, coking [29].
沸石的酸性由酸位点的浓度和强度决定，对积炭形成的速率和选择性具有关键影响。研究表明，酸强度越高、酸位点浓度越大，通常会导致催化剂失活加速[4]。强酸位点尤其容易引发积炭[9]。例如，具有更多酸位点总数的催化剂可能因积炭导致的快速失活而表现出较低活性[31]。相反，分子筛中的弱酸位点通常有利于轻质烯烃生产，并表现出抗积炭特性[13]。以锌改性 HY 沸石为例，其酸性是影响反应的主要因素，并间接影响积炭行为[29]。

The Si/Al ratio is a primary determinant of zeolite acidity. A lower Si/Al ratio (i.e., higher aluminum content) typically results in a higher density of acid sites and stronger acidity [23,49]. While this can initially lead to high catalytic activity, it also corresponds to a higher coke formation rate and rapid catalyst deactivation [49]. For example, HZSM-5 with a low Si/Al ratio (e.g., HZ30) shows the highest acid site density and strength, favoring the formation of oligomers which are partially confined in the catalyst, contributing to deactivation [35]. Conversely, higher Si/Al ratios often correlate with lower acidity and reduced coke formation, though beyond a certain point, very high Si/Al ratios can lead to fewer active acid sites and reduced conversion [26]. The concentration of Brønsted acid sites can also influence coking propensity, with lower concentrations leading to reduced coking and higher selectivity toward C3+ alkenes [34]. The Si/Al ratio also strongly correlates with the amount of coke deposited, particularly in materials like ZSM-5 which can exhibit variations in Al content across the crystal [43].
硅铝比是决定沸石酸性的主要因素。较低的硅铝比（即较高的铝含量）通常会导致酸位点密度更高、酸性更强[23,49]。虽然这最初可能带来较高的催化活性，但也对应着更高的积炭速率和快速的催化剂失活[49]。例如，低硅铝比的 HZSM-5（如 HZ30）显示出最高的酸位点密度和强度，有利于低聚物的形成，这些低聚物部分滞留在催化剂中，从而导致失活[35]。相反，较高的硅铝比通常与较低的酸性和减少的积炭形成相关，但超过一定限度后，过高的硅铝比会导致活性酸位点减少和转化率降低[26]。布朗斯台德酸位点的浓度也会影响积炭倾向，较低浓度可减少积炭并提高对 C3+烯烃的选择性[34]。硅铝比还与积炭沉积量密切相关，特别是在 ZSM-5 等材料中，其晶体内部铝含量可能存在差异[43]。

Crystal Size and Mesoporosity
晶体尺寸与介孔性

Crystal size and the presence of mesoporosity significantly impact reactant diffusion, product removal, and ultimately, coke accumulation. Zeolites with complex porosity, comprising both micropores and macro/mesopores (e.g., ZSM-5 nanocrystals agglomerated with attapulgite), facilitate mass transfer [24]. The introduction of mesopores (2–50 nm) dramatically enhances mass-transfer capacity and reduces steric hindrance, with diffusion coefficients orders of magnitude larger than those in micropores [9]. This improved diffusion allows for better removal of coke precursors and products, thereby mitigating deactivation [9].
晶体尺寸和介孔的存在显著影响反应物扩散、产物脱除及最终的积炭行为。具有复杂孔道结构（同时包含微孔和大孔/介孔）的沸石（如与凹凸棒石黏土团聚的 ZSM-5 纳米晶）能有效促进传质过程[24]。引入 2-50 nm 介孔可大幅提升传质能力并降低空间位阻，其扩散系数比微孔高数个数量级[9]。这种改善的扩散性能有利于积炭前驱体及产物的脱除，从而缓解催化剂失活[9]。

Techniques like alkaline desilication can modify zeolite porosity, leading to increased mesoporosity [38,47]. For instance, treated Zeolite Y and ZSM-5 show increased mesopore volume and diameter, accompanied by a decrease in micropore volume [38,47]. While such treatments enhance specific surface area and mesopore volume, they can also lead to a decrease in overall acid site quantity [25]. A crucial consideration is the potential for excessive loss of crystallinity at high alkali concentrations (
碱处理脱硅等技术可调控沸石孔结构以增加介孔率[38,47]。例如经处理的 Y 型沸石和 ZSM-5 表现出介孔体积与孔径增大，同时微孔体积减少[38,47]。虽然此类处理能提高比表面积和介孔体积，但也会导致酸性位点总数下降[25]。需特别注意高碱浓度下可能造成晶体结构过度破坏

Heteroatom Incorporation
杂原子掺入

Incorporation of heteroatoms into the zeolite framework can modify their physicochemical properties, including acidity and pore characteristics, thereby influencing coking behavior. For example, dealumination can significantly increase the Si/Al ratio, as demonstrated by the creation of deAl-β zeolite with a Si/Al ratio of 1000 [14]. Subsequent incorporation of other metals, such as zirconium, to form
将杂原子掺入沸石骨架可以改变其物理化学性质，包括酸度和孔隙特征，从而影响结焦行为。例如，脱铝可以显著提高 Si/Al 比，如 Si/Al 比为 1000 的脱铝-β沸石所示[14]。随后掺入其他金属，如锆，形成

In SAPO-34, the incorporation of silicon into the
在 SAPO-34 中，硅的掺入

4.2 Reaction Conditions
4.2 反应条件

Reaction conditions significantly dictate the kinetics and characteristics of coke formation on zeolite catalysts, influencing both the rate of deactivation and the nature of the deposited coke [9]. Key parameters such as temperature, pressure, space velocity, and feed composition exhibit complex interplays that can either promote or inhibit coke deposition.
反应条件显著决定着沸石催化剂上积炭的动力学特性与形成特征，同时影响着失活速率和沉积积炭的性质[9]。温度、压力、空速及原料组成等关键参数之间存在复杂的相互作用，这些作用既可促进也可抑制积炭沉积。

Temperature is a critical factor with multifaceted effects on coke formation. In several processes, an increase in reaction temperature generally correlates with a higher coking rate. For instance, in dimethyl ether (DME) conversion over SAPO-34, high reaction temperatures lead to elevated coking rates [7]. Similarly, for methanol-to-hydrocarbons (MTH) reactions, increasing the temperature from 623 K to 773 K substantially reduces the catalyst lifetime (
温度是影响积炭形成的关键因素，具有多方面的作用。在多个反应过程中，反应温度升高通常与积炭速率加快相关。例如，在 SAPO-34 分子筛上进行的二甲醚（DME）转化反应中，高温会导致积炭速率显著上升[7]。同样地，在甲醇制烃类（MTH）反应中，当温度从 623 K 升至 773 K 时，催化剂寿命（

Conversely, in some catalytic systems, higher temperatures within certain ranges can reduce coke deposition. For example, during the transformation of reactants over a SAPO-34 catalyst, increasing the reaction temperature from
相反，在某些催化体系中，特定温度区间内的升温反而能抑制积炭。例如 SAPO-34 催化剂上反应物转化过程中，当反应温度从

Pressure also significantly influences coke formation. Increasing reaction pressure typically leads to higher coke content. For example, in 1‑butene oligomerization, raising the pressure from 1.5 bar to 40 bar escalates the soft coke content from 5.7 wt% to 19.4 wt%, primarily due to enhanced formation of heavy oligomers and their reduced volatility, promoting confinement within the catalyst pores [35]. Similarly, high dimethyl ether (DME) partial pressure contributes to higher coking rates [7]. Reactions are commonly performed at atmospheric pressure [6,30,36,48], but higher pressures up to 2 MPa are also utilized [22].
压力也显著影响焦炭的形成。提高反应压力通常会导致更高的焦炭含量。例如，在 1-丁烯齐聚反应中，将压力从 1.5 巴提高到 40 巴，软焦炭含量从 5.7 wt%增加到 19.4 wt%，这主要是由于重质齐聚物的形成增加及其挥发性降低，促进了其在催化剂孔隙内的限制[35]。类似地，高二甲醚（DME）分压会导致更高的结焦速率[7]。反应通常在大气压下进行[6,30,36,48]，但也会使用高达 2 MPa 的更高压力[22]。

Weight Hourly Space Velocity (WHSV) is another crucial operational parameter. Generally, higher WHSVs can accelerate catalyst coking and deactivation. In MTH reactions, increasing WHSV results in enhanced coke-induced deactivation [34]. For specific catalysts like ZSM-35 and SSZ-13, a lower WHSV is required compared to ZSM-5 due to their inherently faster deactivation rates [42]. Common WHSV values reported range from
重时空速（WHSV）是另一个关键的操作参数。通常，较高的 WHSV 会加速催化剂的结焦和失活。在 MTH 反应中，增加 WHSV 会导致焦炭引起的失活加剧[34]。对于 ZSM-35 和 SSZ-13 等特定催化剂，由于其固有的更快的失活速率，需要比 ZSM-5 更低的 WHSV[42]。报告的常见 WHSV 值范围从

Feed composition and carrier gas atmosphere also play significant roles. The presence of a hydrogen (
原料组成和载气氛围同样起着重要作用。氢气（H2）的存在

The intricate interplay between reaction conditions and zeolite properties is paramount in determining coke deposition behavior. Zeolite topology and acidity influence how specific conditions, like temperature or WHSV, manifest in deactivation rates. For instance, the faster deactivation of ZSM-35 and SSZ-13 compared to ZSM-5 at similar reaction conditions highlights the impact of zeolite structure on coke formation dynamics [42]. Ultimately, optimizing reaction conditions involves a delicate trade-off between achieving desired product yields and minimizing coke formation. For example, while higher temperatures might be kinetically favorable for primary reactions, they can also promote the formation of undesirable coke, necessitating a balanced approach to sustain catalyst activity and selectivity [46].
反应条件与沸石性质之间的复杂相互作用对决定积炭行为至关重要。沸石的拓扑结构和酸性会影响特定条件（如温度或重时空速）在失活速率中的表现。例如，在相似反应条件下，ZSM-35 和 SSZ-13 比 ZSM-5 更快的失活速率凸显了沸石结构对积炭形成动力学的影响[42]。最终，优化反应条件需要在获得理想产品收率与最小化积炭形成之间取得微妙平衡。例如，虽然较高温度可能对主反应动力学有利，但也会促进不良积炭的形成，因此需要采取平衡策略以维持催化剂的活性和选择性[46]。

4.3 Feedstock and Reactant Properties
4.3 原料与反应物性质

The properties of reactants and the overall feedstock composition significantly influence coke formation and catalyst deactivation in zeolite-catalyzed processes. The specific molecular structures, functional groups, and synergistic interactions among feed components dictate the pathways and rates of coke deposition, thereby affecting catalyst lifetime and product selectivity.
反应物性质和整体进料组成显著影响沸石催化过程中的焦炭形成和催化剂失活。进料组分中特定的分子结构、官能团和协同相互作用决定了焦炭沉积的途径和速率，从而影响催化剂寿命和产物选择性。

Individual reactant characteristics play a critical role in their propensity to form coke. For instance, in the methanol-to-olefins (MTO) process, methanol itself serves as the primary source of coke, with coke formation from reaction products being less significant [7,48]. The use of D-methanol, incorporating a kinetic isotope effect where the higher energies of C–D/O–D bonds reduce reaction rates, has been shown to increase
单个反应物特性对其形成焦炭的倾向性起着关键作用。例如，在甲醇制烯烃（MTO）过程中，甲醇本身是焦炭的主要来源，而反应产物形成的焦炭则不那么显著[7,48]。使用 D-甲醇，通过动力学同位素效应（其中 C-D/O-D 键的更高能量降低了反应速率），已显示出增加

Studies on catalytic cracking have demonstrated that light olefins, such as ethylene (
催化裂化研究表明，与正十六烷(n-C16p)等长链烷烃相比，乙烯(

[30].
[30]。

While 1-butene has been utilized as a "coke" precursor in "precoking" treatments to investigate coke formation mechanisms [48], ethanol can modulate coke formation by altering product distribution. Its higher proton affinity (776.4
虽然 1-丁烯常被用作"积碳"前驱体进行"预积碳"处理以研究积碳形成机制[48]，但乙醇可通过改变产物分布来调控积碳形成。相较于乙烯(680.5

Other model reactants like n-hexadecane [22] and m-cresol with iso-propanol have also been investigated, with the latter favoring iso-propoxonium species formation over carbenium species during alkylation, influencing reaction pathways [29].
其他模型反应物如正十六烷[22]以及间甲酚与异丙醇的混合体系也被研究过，后者在烷基化过程中更倾向于形成异丙氧鎓物种而非碳正离子物种，从而影响反应路径[29]。

Feedstock composition, particularly in complex mixtures, exerts a profound influence on coking behavior. For biomass conversion, the molecular structure of biopolymers such as cellulose and lignin significantly affects coke formation and deactivation pathways. Cellulose, a linear glucose polymer, and lignin, a complex polyaromatic polymer, contribute distinctly to coke formation, as evidenced by studies on pine—which comprises various sugars and lignin [3,12]. Lignocellulosic biomass, such as oak, is a typical feedstock for catalytic pyrolysis, further highlighting the role of its components [24].
原料组成（尤其是复杂混合物）对结焦行为具有深远影响。在生物质转化过程中，纤维素和木质素等生物高分子的分子结构会显著影响焦炭形成与失活路径。研究表明，作为线性葡萄糖聚合物的纤维素与复杂多环芳香聚合物的木质素对焦炭形成的贡献截然不同，这在对松木（含有多种糖类与木质素）的研究中得到证实[3,12]。橡木等木质纤维素生物质是催化热解的典型原料，进一步凸显了其组分的作用[24]。

In the context of Fluid Catalytic Cracking (FCC), feedstocks are inherently complex, containing impurities like Conradsen carbon, metals (e.g., Ni, V), oxygenates, nitrogen- and sulfur-containing molecules, and even elements like Na, Ca, and Fe in tight oils. These impurities can significantly impact catalyst performance and promote coke formation [32]. An increase in feedstock basicity has also been observed to promote coke generation [33].
在流化催化裂化（FCC）中，原料本身是复杂的，含有康拉德森碳、金属（如镍、钒）、含氧化合物、含氮和含硫分子等杂质，甚至在致密油中还含有钠、钙和铁等元素。这些杂质会显著影响催化剂性能并促进焦炭形成[32]。此外，人们还观察到原料碱度的增加会促进焦炭的生成[33]。

Furthermore, synergistic effects among different feed components can dramatically alter coking rates and mechanisms. For example, aromatics like methylbenzene exhibit a synergistic effect on coke formation when co-fed with olefins [30]. In biomass co-pyrolysis, blending switchgrass with high-density polyethylene (HDPE) over HZSM-5 leads to complex deactivation patterns. The production of aromatic hydrocarbons from the blend decreases significantly compared to switchgrass alone, indicating interactions that influence catalyst deactivation and coke formation during the process [37]. Similarly, co-feeding glycerol with standard vacuum gas oil (VGO) in FCC operations leads to a reduction in gasoline yield, coupled with increased gas and coke formation, underscoring the detrimental synergistic impact of oxygenates on coking behavior in complex hydrocarbon matrices [46].
此外，不同原料组分间的协同效应会显著改变结焦速率与机理。例如，甲基苯等芳烃与烯烃共进料时对焦炭形成表现出协同效应[30]。在生物质共热解过程中，柳枝稷与高密度聚乙烯（HDPE）在 HZSM-5 催化剂上的混合会导致复杂的失活模式。相较于单独使用柳枝稷，混合原料的芳烃产量显著下降，这表明该过程中存在影响催化剂失活与焦炭形成的相互作用[37]。类似地，在流化催化裂化（FCC）操作中，将甘油与标准减压瓦斯油（VGO）共进料会导致汽油收率降低，同时伴生气相产物和焦炭产量增加，这凸显了含氧化合物在复杂烃类基质中对结焦行为的有害协同影响[46]。

4.4 Metal Loading and Promoters/Additives
4.4 金属负载与助剂/添加剂

The presence of metals and various promoters or additives significantly influences coke formation and deposition on zeolite catalysts, with their effects varying from promoting to inhibiting coking depending on the metal, its loading, the zeolite structure, and the catalytic reaction.
金属及各类助剂或添加剂的存在显著影响沸石催化剂上的积炭形成与沉积，其作用从促进到抑制积炭不等，具体取决于金属种类、负载量、沸石结构以及催化反应条件。

Some metals can accelerate catalyst deactivation by promoting specific coke-forming pathways or by exhibiting poor stability of their active phases. For instance, extraframework zinc cations in ZSM-5 catalysts can introduce a highly reactive pathway for formaldehyde formation via methanol dehydrogenation during methanol-to-hydrocarbons (MTH) conversion, leading to catalyst deactivation [34]. Similarly, zinc loading in HY zeolites enhances the Lewis acidity, which subsequently impacts catalyst activity and selectivity, potentially influencing coking behavior [29]. In the context of fluid catalytic cracking (FCC), metals like nickel (Ni) and vanadium (V) are known contaminants that can promote coke formation, necessitating the use of metal traps as additional components in FCC catalysts to mitigate their detrimental effects [32]. Furthermore, for NiWS/SAPO-11 catalysts, the migration and aggregation of the NiWS active phase itself contributes to catalyst deactivation, likely through a loss of active sites or pore blockage by aggregated species, which can be linked to coke accumulation [22]. The impact of metal loading is also critical, as evidenced by studies on Ni-β zeolite catalysts, where different Ni site densities (e.g., 0.21 and 0.82 Ni per
某些金属可以通过促进特定的结焦途径或表现出较差的活性相稳定性来加速催化剂失活。例如，ZSM-5 催化剂中的骨架外锌阳离子在甲醇制烃（MTH）转化过程中，可以通过甲醇脱氢引入高反应性的甲醛形成途径，导致催化剂失活[34]。类似地，HY 沸石中的锌负载会增强路易斯酸性，进而影响催化剂的活性和选择性，可能影响结焦行为[29]。在流化催化裂化（FCC）中，镍（Ni）和钒（V）等金属是已知的污染物，可以促进焦炭形成，因此需要在 FCC 催化剂中使用金属捕集剂作为附加组分以减轻其有害影响[32]。此外，对于 NiWS/SAPO-11 催化剂，NiWS 活性相本身的迁移和聚集导致催化剂失活，这可能是由于活性位点的损失或聚集物对孔道的堵塞，这与焦炭的积累有关[22]。 金属负载量也至关重要，如对 Ni-β沸石催化剂的研究所示，其中不同的 Ni 位点密度（例如，每 0.21 和 0.82 个 Ni）

Conversely, a wide range of metals and additives are employed to inhibit coke formation, enhance catalytic stability, and improve overall performance. The loading of platinum (Pt) onto HY zeolite, for example, is crucial for promoting hydrogenation reactions, which actively suppresses coke formation by converting coke precursors into less detrimental species [28]. Bimetallic systems can offer synergistic effects; NiMo/AZM catalysts, for instance, exhibit stable catalytic performance and higher activity, largely due to a stabilizing effect between nickel and molybdenum species that inhibits coke formation and preserves catalyst structure and activity during catalytic fast pyrolysis of biomass [25].
相反，人们采用多种金属和添加剂来抑制焦炭形成，提高催化稳定性，并改善整体性能。例如，将铂（Pt）负载到 HY 沸石上对于促进加氢反应至关重要，这通过将焦炭前体转化为危害较小的物质来积极抑制焦炭形成[28]。双金属体系可以提供协同效应；例如，NiMo/AZM 催化剂表现出稳定的催化性能和更高的活性，这主要归因于镍和钼物种之间的稳定作用，该作用在生物质催化快速热解过程中抑制焦炭形成并保持催化剂结构和活性[25]。

The role of promoters is also critical in tailoring zeolite properties for improved coke resistance. Phosphorous treatment is frequently applied to zeolite ZSM-5 to increase its stability [32]. Similarly,
助剂的作用对于调整沸石性能以提高抗焦化性也至关重要。磷处理常用于 ZSM-5 沸石以提高其稳定性[32]。同样，

The influence of metals often stems from their ability to modify the zeolite's acidity. Cations of metal elements exchanged into zeolites tend to reduce the overall acidity by creating Lewis acid sites that are generally weaker than the bridging Brønsted acid sites [26]. This modification of acid site strength and distribution can profoundly alter reaction pathways and coke-forming propensity. Various metals have been successfully applied for the modification of different zeolites to enhance catalytic performance and stability. For ZSM-5, metals like manganese, calcium, potassium, strontium, lanthanum, gallium, and cerium have been utilized, while for SAPO-34, copper, calcium, tungsten, zinc, iron, cobalt, nickel, manganese, lanthanum, cerium, zirconium, and niobium have been explored, all aiming to increase stability in reactions such as methanol-to-olefins (MTO) [26]. Optimal metal loading is also crucial; for example, in Mn/MOR catalysts, a 1 wt.% Mn loading was found to exhibit the highest catalytic activity, suggesting that excessive or insufficient loading can negatively impact performance and deactivation resistance [5].
金属的影响通常源于它们改变沸石酸度的能力。交换到沸石中的金属元素阳离子倾向于通过产生路易斯酸位点来降低总酸度，这些路易斯酸位点通常弱于桥式布朗斯台德酸位点[26]。酸位点强度和分布的这种改变可以深刻地改变反应路径和结焦倾向。各种金属已成功应用于不同沸石的改性，以提高催化性能和稳定性。对于 ZSM-5，已使用锰、钙、钾、锶、镧、镓和铈等金属，而对于 SAPO-34，已探索铜、钙、钨、锌、铁、钴、镍、锰、镧、铈、锆和铌，所有这些都旨在提高甲醇制烯烃（MTO）等反应的稳定性[26]。最佳金属负载量也至关重要；例如，在 Mn/MOR 催化剂中，发现 1 wt.%的 Mn 负载量表现出最高的催化活性，这表明过量或不足的负载量都会对性能和抗失活性产生负面影响[5]。

7. Case Studies: Coke Deposition in Specific Reactions
7. 案例研究：特定反应中的焦炭沉积

This section presents a comparative analysis of coke deposition behavior across various zeolite-catalyzed reactions, offering in-depth case studies that highlight the intricate interplay between feedstock, catalyst properties, and operating conditions. While coke-induced deactivation is a pervasive challenge in heterogeneous catalysis, the specific characteristics of coke species, their formation pathways, and the resulting deactivation mechanisms exhibit significant variability depending on the target reaction. This analysis systematically compares and contrasts the coking phenomena observed in prominent applications such as Methanol-to-Olefins/Hydrocarbons (MTO/MTH) processes, Biomass Catalytic Fast Pyrolysis (CFP), and diverse Hydrocarbon Cracking and Aromatization reactions.
本节对不同沸石催化反应中的积炭行为进行了对比分析，通过深入案例研究揭示了原料特性、催化剂性质与操作条件之间复杂的相互作用机制。虽然积炭失活是多相催化中普遍存在的挑战，但积炭物种的具体特征、形成途径及导致的失活机理会因目标反应的不同而呈现显著差异。本分析系统比较了甲醇制烯烃/烃类（MTO/MTH）、生物质催化快速热解（CFP）以及多种烃类裂解与芳构化反应等典型应用场景中观察到的积炭现象。

Each case study will thoroughly investigate the nature of coke formed, ranging from light, loosely bound oligomers to highly condensed, graphitic structures, often influenced by the reaction intermediates and catalyst pore architecture. For instance, the formation of polymethylated benzenes from hydrocarbon pools in MTO/MTH processes represents a distinct coking pathway [17,41], while biomass pyrolysis yields coke with varying compositions and locations depending on the biopolymer source (e.g., cellulose vs. lignin) [12]. Similarly, different hydrocarbon cracking feeds lead to diverse coke types and deactivation kinetics [30,46].
每个案例研究都将深入探究积炭的性质，其范围从轻质、松散结合的低聚物到高度缩合的类石墨结构，这些性质往往受反应中间体和催化剂孔道结构的影响。例如，甲醇制烯烃/甲醇制烃（MTO/MTH）过程中烃池反应生成的多甲基苯代表了一种独特的积炭路径[17,41]，而生物质热解则根据生物聚合物来源（如纤维素与木质素）产生不同组成和位置的积炭[12]。同样地，不同烃类裂解原料会导致积炭类型和失活动力学的显著差异[30,46]。

Furthermore, the discussion will detail the primary deactivation mechanisms at play, which commonly involve the physical blockage of zeolite pores, the encapsulation or masking of active sites, and the impediment of reactant/product diffusion. These mechanisms are profoundly shaped by the location of coke deposition, whether internal within the microporous network or on the external catalyst surface, as observed across different zeolite topologies like SAPO-34 and ZSM-5 in MTO/MTH [19,39]. Finally, the effectiveness of various mitigation strategies, including catalyst design modifications (e.g., core-shell structures) and process parameter optimization, will be evaluated within the context of each specific reaction, providing a holistic understanding of managing coke-induced deactivation in industrial applications and advanced catalytic processes such as hydroisomerization [28] and oligomerization [35]. This comprehensive overview serves to establish a framework for understanding the nuances of coking behavior and catalyst deactivation across the spectrum of zeolite-catalyzed reactions.
此外，讨论将详细阐述主要失活机制，这些机制通常涉及沸石孔道的物理堵塞、活性位点的包覆或掩蔽以及反应物/产物扩散受阻。正如在 SAPO-34 和 ZSM-5 等不同沸石拓扑结构（应用于 MTO/MTH 反应）中观察到的[19,39]，这些机制深受积炭位置的影响——无论是微孔网络内部还是催化剂外表面。最后，将结合加氢异构化[28]和低聚反应[35]等具体工业应用及先进催化工艺，评估包括催化剂设计改进（如核壳结构）和工艺参数优化在内的多种缓解策略的有效性，从而全面理解如何应对工业应用中积炭导致的失活问题。本综述旨在建立一个理解框架，以把握沸石催化反应中积炭行为与催化剂失活的细微差别。

7.1 Methanol-to-Olefins (MTO) / Methanol-to-Hydrocarbons (MTH)
7.1 甲醇制烯烃(MTO)/甲醇制烃类(MTH)

The Methanol-to-Olefins (MTO) and Methanol-to-Hydrocarbons (MTH) processes are critical catalytic routes for converting methanol into valuable light olefins and hydrocarbons. A central challenge in these processes is catalyst deactivation due to coke deposition, a phenomenon intimately linked to the dual role of hydrocarbon pool (HCP) species within the zeolite catalyst framework [41,44].
甲醇制烯烃（MTO）和甲醇制烃类（MTH）工艺是将甲醇转化为高附加值轻质烯烃及烃类的关键催化路径。这些工艺面临的核心挑战是积碳导致的催化剂失活现象，该现象与沸石催化剂骨架内烃池（HCP）物种的双重作用密切相关[41,44]。

Hydrocarbon pool species serve as crucial active intermediates in the MTO/MTH reaction cycles. For instance, ethene and propene formed in the initial stages can rapidly construct methylcyclopentadiene and methylbenzene, which act as initial HCP intermediates. These cyclic species then facilitate the production of light olefins through both pairing and side-chain routes, propelling the MTO reaction into its steady state governed by the HCP mechanism [41]. However, these very HCP species can also evolve into detrimental coke precursors. Studies have shown that polymethylated benzene species, particularly trimethylbenzene and tetramethylbenzene, are key coke precursors in the MTH process over ZSM-5 catalysts [17]. Furthermore, formaldehyde, an intermediate involved in initial C–C bond formation, has been implicated in coke formation pathways and subsequent deactivation mechanisms in ZSM-5 catalysts during MTH conversion [34,40]. Deactivation of HZSM-5 at lower temperatures (270–
烃池物种是甲醇制烯烃/甲醇制烃（MTO/MTH）反应循环中至关重要的活性中间体。例如，反应初期生成的乙烯和丙烯可快速构建甲基环戊二烯和甲苯，这些环状物种作为初始烃池中间体，随后通过配对路径和侧链路径促进轻质烯烃的生成，推动 MTO 反应进入由烃池机制主导的稳态阶段[41]。然而，这些烃池物种也可能演变为有害的积炭前驱体。研究表明，在多甲基苯类物种中，特别是三甲苯和四甲苯，是 ZSM-5 催化剂上 MTH 过程的关键积炭前驱体[17]。此外，参与初始碳-碳键形成的中间体甲醛，也被证实与 ZSM-5 催化剂在 MTH 转化过程中的积炭路径及后续失活机制相关[34,40]。HZSM-5 在较低温度（270-

The behavior of coke formation and its impact on deactivation vary significantly across different zeolite topologies, notably between SAPO-34 and ZSM-5 [21]. For SAPO-34, a catalyst widely recognized for its high selectivity to light olefins, deactivation by coke deposition can be significant even in the initial minutes of operation. Despite this rapid initial coking, high light olefin yields (above 90%) can be maintained for a period, indicating that the catalyst can sustain performance even with considerable coke accumulation [18]. This characteristic is partly due to the nature and spatial distribution of coke species within SAPO-34, which correlates with intracrystalline diffusion and the accessibility of acidic sites [19]. Microsized SAPO-34 catalysts exhibit high methanol conversion but suffer from a notably short lifetime (less than 4 hours), with a rapid decline in conversion attributed to the vast amount of coke species trapped within its cavities [13].
不同分子筛拓扑结构中的积炭行为及其对失活的影响存在显著差异，尤其在 SAPO-34 与 ZSM-5 之间表现明显[21]。对于以高轻质烯烃选择性著称的 SAPO-34 催化剂，运行初始几分钟内就可能因积炭沉积导致显著失活。尽管初始积炭速率极快，该催化剂仍能在一段时间内维持 90%以上的高轻质烯烃收率，表明其可在严重积炭情况下保持性能[18]。这一特性部分源于 SAPO-34 内部积炭物种的性质与空间分布，这与晶内扩散过程及酸性位点可及性密切相关[19]。微米级 SAPO-34 催化剂虽具有高甲醇转化率，但其寿命显著缩短（不足 4 小时），转化率快速下降归因于大量积炭物种被困在其孔腔内部[13]。

In contrast, ZSM-5 catalysts generally demonstrate more favorable stability during MTH reactions, though typically with lower methanol conversion compared to SAPO-34 [13]. The coke deposition behavior in ZSM-5 has been extensively studied at the nanoscale [20,43]. For ZSM-5, a decreasing
相比之下，ZSM-5 催化剂在 MTH 反应中通常表现出更有利的稳定性，尽管其甲醇转化率通常低于 SAPO-34 [13]。ZSM-5 中的结焦行为已在纳米尺度上得到广泛研究 [20,43]。对于 ZSM-5，降低

The location and morphology of coke within the zeolite pores are critical determinants of deactivation. Experimental evidence indicates that coke formation in ZSM-5 during MTH conversion preferentially begins within the channel intersections [39]. As coking progresses, the straight pores become increasingly loaded with condensed coke, which directly correlates with a significant loss of catalytic activity in the later stages of deactivation [39]. Studies on various zeolites, including ZSM-5, ZSM-35, and SSZ-13, reveal that the micropore topology fundamentally directs the confinement and structure of the coke. Specifically, the largest void zones within the micropore space are the most susceptible to coke deposition [42]. For SAPO-34, the deactivation mode involves coke diffusion and subsequent blockage of acidic sites due to the spatial distribution of coke species [19]. This understanding of coke location and its interplay with zeolite architecture is crucial for designing more robust and long-lasting catalysts for MTO/MTH processes.
沸石孔道内积炭的位置和形貌是催化剂失活的关键决定因素。实验证据表明，ZSM-5 分子筛在甲醇制烃（MTH）转化过程中，积炭优先在孔道交叉处开始形成[39]。随着积炭程度加深，直型孔道逐渐被稠合积炭占据，这与失活后期催化活性显著下降直接相关[39]。对 ZSM-5、ZSM-35 和 SSZ-13 等多种沸石的研究表明，微孔拓扑结构从根本上主导了积炭的限域形态和结构特征，其中微孔空间内最大空隙区域最易发生积炭沉积[42]。就 SAPO-34 而言，其失活模式涉及积炭扩散及随后因积炭物种空间分布导致的酸性位点阻塞[19]。这种对积炭位置及其与沸石结构相互作用的理解，对于设计更稳定、寿命更长的甲醇制烯烃/烃（MTO/MTH）工艺催化剂至关重要。

7.2 Biomass Catalytic Fast Pyrolysis (CFP)
7.2 生物质催化快速热解（CFP）

Catalytic fast pyrolysis (CFP) of biomass for the production of biofuels and chemicals is significantly impacted by catalyst deactivation due to coke formation [24,25,37]. Understanding the coking behavior, especially from different biopolymer constituents, is crucial for mitigating deactivation.
生物质催化快速热解（CFP）生产生物燃料和化学品受到焦炭形成引起的催化剂失活的显著影响[24,25,37]。了解结焦行为，特别是来自不同生物聚合物组分的结焦行为，对于减轻失活至关重要。

Studies investigating coke deposition during CFP of various biomass feedstocks, such as oak, pine, and switchgrass, over catalysts like HZSM-5 and
研究了在 HZSM-5 等催化剂上，各种生物质原料（如橡木、松木和柳枝稷）在 CFP 过程中焦炭沉积的情况，

Significant differences exist in the coking behavior of cellulose and lignin during CFP over ZSM-5 catalysts. Cellulose-derived coke, as observed in studies with both ZSM-5 and unilamellar mesoporous MFI nanosheets (UMNs), tends to be more prolific, with its quantity and impact on catalyst activity and selectivity extensively examined [3,4,12]. Lignin, on the other hand, contributes distinctively to coke formation. Research indicates that cellulose predominantly forms coke within the catalyst's internal channels, leading to pore blocking and active site masking. In contrast, lignin contributes more significantly to coke formation on the external surface of the catalyst, which can encapsulate the active sites but may also influence vapor diffusion into the pores [12]. These differences in spatial distribution—internal versus surface coke—are critical in understanding the dominant deactivation pathways.
在 ZSM-5 催化剂上进行催化快速热解（CFP）时，纤维素与木质素的结焦行为存在显著差异。研究表明，无论是 ZSM-5 还是单层介孔 MFI 纳米片（UMNs）催化剂，纤维素衍生的焦炭往往更易生成，其数量及对催化剂活性和选择性的影响已得到广泛研究[3,4,12]。而木质素则表现出独特的结焦特性。数据显示，纤维素主要在内孔道形成焦炭，导致孔道堵塞和活性位点覆盖；相比之下，木质素更倾向于在催化剂外表面形成焦炭，这种表面焦炭虽会包覆活性位点，但同时也可能影响反应物蒸气向孔内的扩散[12]。这种空间分布差异——内部结焦与表面结焦——对于理解催化剂失活的主导路径具有关键意义。

The composition of coke also varies depending on the biopolymer source and is correlated with reaction conditions and catalyst properties such as acidity and pore size. Lignin-derived coke is typically more aromatic and highly condensed due to its inherent phenolic structure, forming polyaromatic hydrocarbons that are difficult to remove. Cellulose, being a polysaccharide, generates a wider range of oxygenates and smaller hydrocarbon fragments, which can then polymerize into coke structures that are often less graphitic than those from lignin [12]. The formation of intermediates like phenol and cresols during the deactivation process, particularly from pine pyrolysis vapors over HZSM-5, underscores the role of these oxygenated compounds in coke precursor formation [4]. Catalyst pore architecture, such as that of UMNs, influences the accessibility of active sites and thus the extent and location of coke deposition, which in turn affects the deactivation rate and product selectivity [4].
焦炭的组成因生物聚合物来源不同而异，并与反应条件及催化剂特性（如酸性和孔径）密切相关。木质素衍生的焦炭通常因其固有的酚类结构而具有更高的芳香性和缩合度，形成难以去除的多环芳烃。纤维素作为多糖化合物，会产生更广泛的含氧化合物和较小烃类片段，这些物质随后聚合成焦炭结构，其石墨化程度通常低于木质素衍生物[12]。失活过程中酚类和甲酚等中间体的形成（特别是松木热解蒸气在 HZSM-5 催化剂上的反应），凸显了这些含氧化合物在焦炭前驱体形成中的作用[4]。催化剂孔道结构（如 UMNs）会影响活性位点的可及性，从而决定焦炭沉积的程度和位置，进而影响失活速率和产物选择性[4]。

The location and composition of coke profoundly impact catalyst performance in terms of cracking, deoxygenation, and aromatic production. Internal coke from cellulose can severely impede the cracking of larger pyrolysis vapors and limit the deoxygenation reactions by blocking access to acid sites. This leads to a rapid decline in overall catalytic activity and a shift in product selectivity [3,12]. Surface coke from lignin can also lead to deactivation by covering external active sites and reducing the effective catalyst surface area. Moreover, highly condensed, aromatic coke can act as a secondary catalyst or a diffusion barrier, influencing the selectivity towards specific products, including aromatics, by favoring certain reaction pathways or inhibiting others [12]. Therefore, tailoring catalyst properties and reaction conditions to manage the formation and characteristics of coke derived from different biomass components is essential for sustaining catalyst performance and optimizing biofuel production.
积炭的位置与组成对催化剂在裂解、脱氧和芳烃生成方面的性能具有深远影响。纤维素衍生的内部积炭会严重阻碍较大热解蒸汽的裂解，并通过阻塞酸性位点来限制脱氧反应，导致催化剂整体活性迅速下降及产物选择性发生偏移[3,12]。木质素产生的表面积炭同样会覆盖外部活性位点、减少有效催化剂表面积而导致失活。此外，高度缩合的芳香族积炭可作为次级催化剂或扩散屏障，通过促进特定反应路径或抑制其他路径，影响包括芳烃在内的特定产物选择性[12]。因此，通过调控催化剂特性和反应条件来管理不同生物质组分衍生积炭的形成与特性，对于维持催化剂性能和优化生物燃料生产至关重要。

7.3 Hydrocarbon Cracking and Aromatization
7.3 烃类裂解与芳构化

Coke formation represents a predominant deactivation mechanism for zeolite catalysts employed in hydrocarbon cracking and aromatization processes. This deactivation typically manifests through several interconnected phenomena, including the physical blockage of catalyst pores, the coverage of active catalytic sites, and the impediment of reactant/product diffusion, collectively leading to a reduction in catalytic activity and selectivity over time. The rate and nature of coke deposition are highly dependent on the type of hydrocarbon feed and the specific reaction conditions.
积炭是烃类裂解和芳构化过程中沸石催化剂失活的主要机制。这种失活通常通过几种相互关联的现象表现出来，包括催化剂孔隙的物理堵塞、活性催化位点的覆盖以及反应物/产物扩散受阻，这些因素共同导致催化活性和选择性随时间下降。积炭的速率和性质高度依赖于烃类原料类型和特定反应条件。

Various studies highlight the differential coking propensity of diverse feedstocks. For instance, the cracking of a range of hydrocarbons, including n-hexadecane, olefins, naphthenes, and aromatics, has been investigated to understand coke evolution and its impact on catalyst performance [30]. Similarly, the cracking of high-density polyethylene (HDPE) on zeolites such as HZSM-5,
多项研究强调了不同原料的差异化积炭倾向。例如，为理解积炭演变及其对催化剂性能的影响，已对包括正十六烷、烯烃、环烷烃和芳烃在内的一系列烃类裂解进行了研究[30]。同样，高密度聚乙烯（HDPE）在 HZSM-5 等沸石上的裂解过程，

The manifestation of deactivation is empirically observed as a decline in conversion over time. For example, in n-hexane cracking over H-MFI zeolites at 923 K, a clear decrease in n-hexane conversion was noted as the reaction progressed, directly correlating with coke accumulation [23]. This highlights the practical impact of coke on catalyst longevity and efficiency.
失活现象在实验中表现为转化率随时间逐渐下降。以 923K 下正己烷在 H-MFI 沸石上的裂解反应为例，随着反应进行可观察到正己烷转化率明显降低，这与积炭量的积累直接相关[23]。这一现象凸显了积炭对催化剂寿命和效率的实际影响。

In aromatization processes, understanding the dynamic migration of intermediates across active sites is crucial for elucidating the mechanisms of coke formation and catalyst deactivation. While specific detailed mechanisms of intermediate migration leading to coke in aromatization were not explicitly elaborated in the provided digests, research often focuses on coking in the context of light alkanes aromatization [9] and other complex hydrocarbon conversions such as hydroisomerization [28]. The interplay between reactant adsorption, reaction pathways, and the mobility of reactive intermediates on the zeolite surface and within its pores ultimately dictates the formation and accumulation of coke species. These studies collectively underscore the necessity of characterizing coke deposition behavior across various feeds and understanding its mechanistic implications for catalyst stability and performance in cracking and aromatization applications [15,23,30,36,46].
在芳构化过程中，理解中间体在活性位点间的动态迁移对于阐明积炭形成和催化剂失活机制至关重要。虽然提供的摘要中未明确阐述芳构化过程中中间体迁移导致积炭的具体详细机制，但研究通常聚焦于轻质烷烃芳构化[9]以及加氢异构化[28]等其他复杂烃类转化过程中的积炭现象。反应物吸附、反应路径与活性中间体在沸石表面及孔道内迁移性之间的相互作用，最终决定了积炭物种的形成与累积。这些研究共同强调了表征不同原料积炭沉积行为的必要性，并理解其对裂解和芳构化应用中催化剂稳定性与性能的机制性影响[15,23,30,36,46]。

8. Conclusions and Future Directions
8. 结论与未来研究方向

The pervasive challenge of coking deactivation in zeolite catalysts remains a critical bottleneck for many industrial processes, despite extensive research over several decades. Current understanding highlights coke formation as a complex interplay of catalyst properties, reaction conditions, and the inherent chemistry of hydrocarbon transformation. The primary mechanisms of deactivation are recognized as the physical blockage of pores and channels, along with the chemical masking or destruction of active acidic sites, particularly strong Brønsted acid sites, by polyaromatic carbonaceous deposits [18,24,35].
沸石催化剂积炭失活这一普遍性挑战仍是制约众多工业过程的关键瓶颈，尽管相关研究已持续数十年。现有研究表明，焦炭形成是催化剂特性、反应条件与烃类转化内在化学性质之间复杂相互作用的结果。失活的主要机制已被确认为多环芳烃碳质沉积物造成的孔道物理堵塞，以及对活性酸性位点（尤其是强布朗斯特酸位点）的化学覆盖或破坏[18,24,35]。

Key factors influencing coke deposition include the zeolite's pore structure and topology, which dictate the spatial confinement and growth of coke species [19,23,42]. For instance, coke typically initiates in channel intersections and more spacious regions, subsequently propagating into straight pores and eventually blocking micropores and mesopores [39,42]. The acidity of the zeolite, encompassing its strength, density, and distribution, also plays a pivotal role, with stronger acid sites often being more susceptible to coke formation and deactivation [18,31]. Reaction conditions such as temperature, reactant partial pressure, and the presence of specific feedstock components (e.g., light olefins, formaldehyde, ethanol) can significantly accelerate coking rates [7,30,34,36]. Conversely, the presence of water or a hydrogen atmosphere can attenuate coke formation [18,28]. The evolution of coke often follows an autocatalytic mechanism, progressing through distinct periods of initial deposition, transition, and steady-state coking [7,16].
影响焦炭沉积的关键因素包括沸石的孔结构和拓扑结构，它们决定了焦炭物种的空间限制和生长[19,23,42]。例如，焦炭通常在通道交叉点和更宽敞的区域开始形成，随后扩散到直孔中，最终堵塞微孔和中孔[39,42]。沸石的酸性，包括其强度、密度和分布，也起着关键作用，其中较强的酸性位点通常更容易发生焦炭形成和失活[18,31]。反应条件，如温度、反应物分压和特定原料组分（如轻烯烃、甲醛、乙醇）的存在，可以显著加速焦化速率[7,30,34,36]。相反，水或氢气氛的存在可以减缓焦炭的形成[18,28]。焦炭的演变通常遵循自催化机制，经历初始沉积、过渡和稳态焦化等不同阶段[7,16]。

Despite significant progress in understanding these phenomena, several areas urgently require further research. A critical need exists for developing more accurate and comprehensive models of coke formation and deactivation, moving beyond empirical correlations to capture the complex, multi-scale nature of coking, including its spatial and chemical evolution within the catalyst framework [30]. Such models should integrate insights from kinetic studies, like the autocatalytic nature observed in DTO reactions, and account for the dynamic changes in coke morphology and location throughout the deactivation process [7,16].
尽管对这些现象的理解已取得重大进展，仍有若干领域亟需深入研究。当前迫切需要开发更精确、更全面的结焦形成与失活模型，突破经验关联式的局限，以捕捉结焦过程复杂的多尺度特性——包括其在催化剂骨架内的空间分布与化学演化[30]。这类模型应整合动力学研究（如 DTO 反应中观察到的自催化特性）的洞见，并考虑失活过程中焦炭形貌与位置分布的动态变化[7,16]。

Designing more coke-resistant catalysts is paramount. Specific research directions include:
设计抗结焦催化剂至关重要。具体研究方向包括：

1. Novel Catalyst Architectures with Tailored Pore Structures and Acidity: This involves engineering hierarchical porosity to improve active site accessibility while maintaining crystallinity, as well as optimizing mesopore diameters and acid site properties [3,4,38]. The development of nanocrystalline zeolites and composites like SAPO-34/ZSM-5, which minimize diffusion restrictions and moderate acid site strength, shows promise [13,45]. Further studies should also explore the optimal
1. 具有定制孔结构和酸性的新型催化剂架构：这包括构建分级孔隙度以在保持结晶度的同时提高活性位点可及性，以及优化中孔直径和酸性位点性质[3,4,38]。开发纳米晶分子筛和复合材料，如 SAPO-34/ZSM-5，可最大限度地减少扩散限制并调节酸性位点强度，显示出广阔前景[13,45]。进一步的研究还应探索最佳的

2. Advanced Characterization Techniques: The use of in situ and operando studies with techniques like Atom Probe Tomography (APT), Electron Diffraction (ED), and hyperspectral confocal microscopy (TEFL imaging) is crucial for real-time, nanoscale investigation of coke formation and evolution [20,39,43]. These techniques can provide invaluable insights into the precise location, 3D structure, and chemical nature of coke species, correlating them with catalytic performance and deactivation mechanisms at an unprecedented level of detail [2,6,42]. For instance, understanding how carbon clusters relate to local acid site density can guide material design [43].
2. 先进表征技术：采用原子探针断层扫描（APT）、电子衍射（ED）和高光谱共聚焦显微镜（TEFL 成像）等原位及工况研究方法，对焦炭形成与演化的纳米尺度实时观测至关重要[20,39,43]。这些技术能以前所未有的精度揭示焦炭物种的精确位置、三维结构及化学性质，并将其与催化性能及失活机制相关联[2,6,42]。例如，理解碳簇与局部酸位密度的关系可指导材料设计[43]。

3. Optimization of Regeneration Processes: While conventional air oxidation is effective at restoring activity by burning off coke, alternative methods that minimize catalyst degradation and maximize regeneration efficiency are needed [14,24]. Investigating the long-term impact of repeated regeneration cycles on catalyst stability, as well as exploring novel techniques such as ozonation for mild-condition regeneration, are promising avenues [10,47]. The efficacy of non-thermal plasma (NTP) assisted catalytic technology also warrants further exploration for its potential in reducing coke yield and enhancing activity [45].
3. 再生工艺优化：虽然传统空气氧化法能通过燃烧积炭有效恢复催化剂活性，但仍需开发能最大限度减少催化剂降解并提高再生效率的替代方法[14,24]。研究多次再生循环对催化剂稳定性的长期影响，以及探索臭氧氧化等温和条件再生新技术，都是极具前景的研究方向[10,47]。非热等离子体（NTP）辅助催化技术在降低积炭产率和提升活性方面的潜力也值得进一步探索[45]。

4. Application of Machine Learning (ML): ML holds significant potential to assist in the design of anti-coking catalysts by establishing and optimizing prediction models based on feedstock composition, catalyst structure, and reaction conditions. This can accelerate the discovery of new materials and operating parameters with superior anti-deactivation abilities, leading to improved yields and conversion rates in processes like RFCC [33].
4. 机器学习（ML）应用：机器学习通过建立基于原料组成、催化剂结构和反应条件的预测模型并进行优化，在抗积炭催化剂设计方面具有重要潜力。这能加速发现具有优异抗失活能力的新材料和操作参数，从而提升如重油催化裂化（RFCC）等工艺的收率和转化率[33]。

Addressing these challenges necessitates a robust interdisciplinary approach, integrating expertise from materials science, chemical engineering, and computational chemistry. This collaborative effort will be vital for unlocking the full potential of zeolite catalysts and ensuring their long-term viability in critical industrial applications [4,26,33].
应对这些挑战需要采用强有力的跨学科方法，整合材料科学、化学工程和计算化学领域的专业知识。这种协同努力对于充分释放沸石催化剂潜力、确保其在关键工业应用中长期稳定运行至关重要[4,26,33]。

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[35] 1-丁烯齐聚反应中 HZSM-5 沸石催化剂的积碳失活与再生

[36] Roles of ethanol in coke formation and HZSM-5 deactivation during n-heptane catalytic cracking
[36] 乙醇在正庚烷催化裂化过程中对焦炭形成及 HZSM-5 失活的作用

[37] Catalytic co-pyrolysis of switchgrass and polyethylene over HZSM-5 Catalyst deactivation and coke formation
[37] 柳枝稷与聚乙烯在 HZSM-5 催化剂上的共催化热解：催化剂失活与焦炭形成

[38] Effects of secondary mesoporosity and zeolite crystallinity on catalyst deactivation of ZSM-5 in propanal conversion
[38] 二次介孔性与沸石结晶度对 ZSM-5 催化剂在丙醛转化中失活行为的影响

[39] Electron Diffraction Enables the Mapping of Coke in ZSM-5 Micropores Formed during Methanol-to-Hydrocarbons
[39] 电子衍射技术实现甲醇制烃过程中 ZSM-5 微孔内焦炭分布的定位表征

[40] Carbon Deposit Analysis in Catalyst Deactivation, Regeneration, and Rejuvenation
[40] 催化剂失活、再生与恢复过程中的积碳分析

[41] Origin and evolution of the initial hydrocarbon pool intermediates in the transition period for the conversion of methanol to olefins
[41] 甲醇制烯烃转化过渡期初始烃池中间体的起源与演化

[42] how-micropore-topology-influences-the-structure-and-location-of-coke-in-zeolite-catalysts
[42] 微孔拓扑结构对分子筛催化剂中积炭结构与位置的影响机制

[43] Coke Formation in a Zeolite Crystal During the Methanol‐to‐Hydrocarbons Reaction as Studied with Atom Probe Tomography
[43] 基于原子探针层析技术研究甲醇制烃反应中分子筛晶体内积炭形成过程

[44] Formation and evolution of the coke precursors on the zeolite catalyst in the conversion of methanol to olefins
[44] 沸石催化剂上甲醇制烯烃过程中焦炭前驱体的形成和演变

[45] Coking characteristics and deactivation mechanism of the HZSM-5 zeolite employed in the upgrading of biomass-derived
[45] 生物质衍生气体升级改造中 HZSM-5 沸石的结焦特性和失活机理

[46] Catalytic deactivation pathways during the cracking of glycerol and glycerol VGO blends under FCC unit conditions
[46] FCC 装置条件下甘油和甘油 VGO 混合物裂解过程中的催化失活途径

[47] Deactivation and regeneration dynamics in hierarchical zeolites
[47] 分级沸石的失活和再生动力学

[48] Presituated “coke”-determined mechanistic route for ethene formation in the methanol-to-olefins process on SAPO-34 catalyst
[48] SAPO-34 催化剂上甲醇制烯烃过程中乙烯生成的预沉积"积炭"决定机制路径

[49] Effect of SiO2-Al2O3 ratio on the performance of nanocrystal ZSM-5 zeolite catalysts in methanol to gasoline conversion
[49] SiO2-Al2O3 比例对纳米晶 ZSM-5 沸石催化剂在甲醇制汽油转化中性能的影响