Matrix Effects in a Fluid Catalytic Cracking Catalyst Particle: Influence on Structure,Acidity, and Accessibility

Matrix effects in a fluid catalytic cracking (FCC) catalyst have been studied in terms of structure, accessibility, and acidity. An extensive characterization study into the structural and acidic properties of a FCC catalyst, its individual components (i.e., zeolite H-Y, binder (boehmite/silica) and kaolin clay), and two model FCC catalyst samples containing only two components (i.e., zeolite-binder and binder-clay) was performed at relevant conditions. This allowed the drawing of conclusions about the role of each individual component, describing their mutual physicochemical interactions, establishing structure-acidity relationships, and determining matrix effects in FCC catalyst materials. This has been made possible by using a wide variety of characterization techniques, including temperature-programmed desorption of ammonia, infrared spectroscopy in combination with CO as probe molecule, transmission electron microscopy, X-ray diffraction, Ar physisorption, and advanced nuclear magnetic resonance. By doing so it was, for example, revealed that a freshly prepared spray-dried FCC catalyst appears as a physical mixture of its individual components, but under typical riser reactor conditions, the interaction between zeolite H-Y and binder material is significant and mobile aluminum migrates and inserts from the binder into the defects of the zeolite framework, thereby creating additional Brønsted acid sites and restoring the framework structure.     

Staining of fluid-catalytic-cracking catalysts: localising Brønsted acidity within a single catalyst particle

A time‐resolved in situ micro‐spectroscopic approach has been used to investigate the Brønsted acidic properties of fluid‐catalytic‐cracking (FCC) catalysts at the single particle level by applying the acid‐catalysed styrene oligomerisation probe reaction. The reactivity of individual FCC components (zeolite, clay, alumina and silica) was monitored by UV/Vis micro‐spectroscopy and showed that only clay and zeolites (Y and ZSM‐5) contain Brønsted acid sites that are strong enough to catalyse the conversion of 4‐fluorostyrene into carbocationic species. By applying the same approach to complete FCC catalyst particles, it has been found that the fingerprint of the zeolitic UV/Vis spectra is clearly recognisable. This almost exclusive zeolitic activity is confirmed by the fact that hardly any reactivity is observed for FCC particles that contain no zeolite. Confocal fluorescence microscopy images of FCC catalyst particles reveal inhomogeneously distributed micron‐sized zeolite domains with a highly fluorescent signal upon reaction. By examining laboratory deactivated FCC catalyst particles in a statistical approach, a clear trend of decreasing fluorescence intensity, and thus Brønsted acidity, of the zeolite domains is observed with increasing severity of the deactivation method. By comparing the average fluorescence intensities obtained with two styrenes that differ in reactivity, it has been found that the Brønsted acid site strength within FCC catalyst particles containing ZSM‐5 is more uniform than within those containing zeolite Y, as confirmed with temperature‐programmed desorption of ammonia.     

Pt-KL zeolite catalysts of different preparation: Part I. Catalyst characterization

0.8% Pt on KL zeolite was prepared by reduction with H₂ and NaBH₄. Transmission electron microscopy and X-ray diffraction were used for characterization of morphology of the metal particles; acidity of the zeolite framework was measured with IR spectra of adsorbed pyridine. Reduction by NaBHP₄ produced rather large, needle-like Pt crystallites on the outer surface of zeolite grains which contained very little acidity. Subsequent hydrogen treatment brought about their severe sintering; at the same time, small crystallites appeared. A bimodal distribution was seen when the catalyst was reduced with hydrogen; this sample exhibited appreciable acidity. X-ray diffraction data showed the presence of Pt particles above noise level in the case of borohydride-reduced catalyst only, in agreement with EM data.     

Probing the Different Life Stages of a Fluid Catalytic Cracking Particle with Integrated Laser and Electron Microscopy

While cycling through a fluid catalytic cracking (FCC) unit, the structure and performance of FCC catalyst particles are severely affected. In this study, we set out to characterize the damage to commercial equilibrium catalyst particles, further denoted as ECat samples, and map the different pathways involved in their deactivation in a practical unit. The degradation was studied on a structural and a functional level. Transmission electron microscopy (TEM) of ECat samples revealed several structural features; including zeolite crystals that were partly or fully severed, mesoporous, macroporous, and/or amorphous. These defects were then correlated to structural features observed in FCC particles that were treated with different levels of hydrothermal deactivation. This allowed us not only to identify which features observed in ECat samples were a result of hydrothermal deactivation, but also to determine the severity of treatments resulting in these defects. For functional characterization of the ECat sample, the Brønsted acidity within individual FCC particles was studied by a selective fluorescent probe reaction with 4‐fluorostyrene. Integrated laser and electron microscopy (iLEM) allowed correlating this Brønsted acidity to structural features by combining a fluorescence and a transmission electron microscope in a single set‐up. Together, these analyses allowed us to postulate a plausible model for the degradation of zeolite crystals in FCC particles in the ECat sample. Furthermore, the distribution of the various deactivation processes within particles of different ages was studied. A rim of completely deactivated zeolites surrounding each particle in the ECat sample was identified by using iLEM. These zeolites, which were never observed in fresh or steam‐deactivated samples, contained clots of dense structures. The structures are proposed to be carbonaceous deposits formed during the cracking process, and seem resistant towards burning off during catalyst regeneration.     

Nickel Poisoning of a Cracking Catalyst Unravelled by Single-Particle X-ray Fluorescence-Diffraction-Absorption Tomography

Ni contamination from crude oil in the fluid catalytic cracking (FCC) process is one of the primary sources of catalyst deactivation, thereby promoting dehydrogenation–hydrogenation and speeding up coke growth. Herein, single-particle X-ray fluorescence, diffraction and absorption (μXRF-μXRD-μXAS) tomography is used in combination with confocal fluorescence microscopy (CFM) after thiophene staining to spatially resolve Ni interaction with catalyst components and study zeolite degradation, including the processes of dealumination and Brønsted acid sites distribution changes. The comparison between a Ni-lean particle, exposed to hydrotreated feedstock, and a Ni-rich one, exposed to non-hydrotreated feedstock, reveals a preferential interaction of Ni, found in co-localization with Fe, with the γ-Al₂O₃ matrix, leading to the formation of spinel-type hotspots. Although both particles show similar surface zeolite degradation, the Ni-rich particle displays higher dealumination and a clear Brønsted acidity drop.     

High‐Resolution Single‐Molecule Fluorescence Imaging of Zeolite Aggregates within Real‐Life Fluid Catalytic Cracking Particles

Fluid catalytic cracking (FCC) is a major process in oil refineries to produce gasoline and base chemicals from crude oil fractions. The spatial distribution and acidity of zeolite aggregates embedded within the 50–150 μm‐sized FCC spheres heavily influence their catalytic performance. Single‐molecule fluorescence‐based imaging methods, namely nanometer accuracy by stochastic chemical reactions (NASCA) and super‐resolution optical fluctuation imaging (SOFI) were used to study the catalytic activity of sub‐micrometer zeolite ZSM‐5 domains within real‐life FCC catalyst particles. The formation of fluorescent product molecules taking place at Brønsted acid sites was monitored with single turnover sensitivity and high spatiotemporal resolution, providing detailed insight in dispersion and catalytic activity of zeolite ZSM‐5 aggregates. The results point towards substantial differences in turnover frequencies between the zeolite aggregates, revealing significant intraparticle heterogeneities in Brønsted reactivity.     

Nickel Poisoning of a Cracking Catalyst Unravelled by Single‐Particle X‐ray Fluorescence‐Diffraction‐Absorption Tomography

Ni contamination from crude oil in the fluid catalytic cracking (FCC) process is one of the primary sources of catalyst deactivation, thereby promoting dehydrogenation–hydrogenation and speeding up coke growth. Herein, single‐particle X‐ray fluorescence, diffraction and absorption (μXRF‐μXRD‐μXAS) tomography is used in combination with confocal fluorescence microscopy (CFM) after thiophene staining to spatially resolve Ni interaction with catalyst components and study zeolite degradation, including the processes of dealumination and Brønsted acid sites distribution changes. The comparison between a Ni‐lean particle, exposed to hydrotreated feedstock, and a Ni‐rich one, exposed to non‐hydrotreated feedstock, reveals a preferential interaction of Ni, found in co‐localization with Fe, with the γ‐Al₂O₃ matrix, leading to the formation of spinel‐type hotspots. Although both particles show similar surface zeolite degradation, the Ni‐rich particle displays higher dealumination and a clear Brønsted acidity drop.     

以催化裂化废催化剂为原料合成NaY分子筛的研究

针对催化裂化(FCC)废催化剂的回收利用问题,提出了一种废催化剂再利用的方法,即以FCC废催化剂为铝源,合成时只补充部分硅源,采用自制的高效NaY沸石导向剂,水热合成NaY分子筛。同时,以普通的化工原料合成了对比试样Y型分子筛。讨论了不同的FCC废催化剂预处理方式对合成产物性能的影响,发现以经过碱熔活化处理的废催化剂为原料合成的Y分子筛拥有更高的结晶度和纯度。采用X射线衍射、热分析、程序升温脱附法(NH3-TPD)和N₂静态容量吸附法对结晶产物和对比样品的晶体结构,热稳定性、酸性质、比表面积以及孔分布进行了表征。结果显示,以FCC废催化剂为原料完全可以合成出与普通原料性能接近的NaY分子筛。其BET比表面积可以达到615 m²·g^-1,孔体积可达0.38 cm³·g^-1,孔径集中在0.51 nm左右。     

丙烯醚化合成二异丙醚催化剂研究

比较了Hβ沸石、树脂、ZSM-5沸石等常用于丙烯醚化合成二异丙醚（DIPE）催化剂的性能,考察了助剂对Hβ沸石孔结构、酸度及催化活性的影响。结果表明,Hβ沸石上丙烯醚化合成DIPE的催化活性优于ZSM-5沸石,而树脂催化剂可催化丙烯水合生成异丙醇（IPA）反应。TiO2、ZrO2、碱土金属、稀土元素和VB族元素均使Hβ沸石的B酸中心减少,L酸中心增多。总酸量较大、L酸中心较多的催化剂,更有利于DIPE的生成。孔性质对催化剂活性的影响较小。TiO2可以大幅度提高DIPE选择性和时空产率,对提高丙烯转化率并无贡献。ZrO2可提高DIPE选择性、丙烯转化率和DIPE的时空产率,副产丙酮,且C6杂质较多。同时添加一种碱土金属、一种稀土元素和一种VB族元素制备的Hβ沸石催化剂具有较好的合成DIPE活性,在165℃、7.0 MPa、水/丙烯摩尔比0.5和LHSV 0.5h－1时,DIPE的初始收率达到39%。运转1 000 h后,DIPE收率仅下降了3%。     

多酸基深度加氢脱硫催化剂的原位表征和反应性能

采用浸渍法合成了镍盐复合的磷钨酸(HPW)/纳米晶HZSM-5固体酸催化剂,其在催化裂化(FCC)汽油加氢改质反应中显示出了良好地深度加氢脱硫活性。 原位电子自旋共振和原位吡啶吸附红外光谱表征手段的研究结果表明,纳米晶HZSM-5沸石上Ni(Ⅱ)结合3电子还原态的HPW(Ⅲ)是FCC汽油深度加氢脱硫反应的活性中心。 探讨了多酸基催化剂在FCC汽油深度加氢脱硫反应中活性改善的原因。     

FCC轻汽油催化裂化生产丙烯反应规律的研究

在提升管实验装置和脉冲色谱装置上，采用ZSM-5催化剂，考察了不同条件下FCC轻汽油和2M1C5＝的裂化。结果表明,催化裂化过程添加ZSM 5催化剂可提高汽油中C5＝、C6＝的质量分数。轻汽油裂化生产丙烯的性能优于重汽油和全馏分汽油，在相对低的温度下瞬时反应能得到较高的丙烯收率。在脉冲色谱装置上，反应温度和载气流量对轻汽油和2M1C5＝裂化生产丙烯的影响一致，即反应温度升高，载气流量降低，丙烯收率增加。提高反应温度，延长停留时间可以提高丙烯对丁烯的比例。轻汽油在ZSM-5催化剂上反应，催化剂结焦失活速度开始较快，后来减缓。ZSM-5催化剂结焦失活对丙烯生成的抑制作用大于对丁烯的抑制作用，ZSM-5的强酸中心多则更有利于生成丙烯。     

Characterization of the Effects of Vanadium Traps in Cracking Catalysts by Imaging Secondary Ion Mass Spectrometry and Microactivity Test

The vanadium trapping effect of Mg and La containing additives in cracking catalyst contaminated with 2300 ppm Ni and 4700 ppm V has been analyzed by microactivity test (MAT) and imaging secondary ion mass spectrometry (SIMS). The results of SIMS imaging are consistent with cracking activity data and show that the La/spinel is a superior vanadium trap for the fluid catalytic cracking of hydrocarbons (FCC) operation. La/spinel serves as a dual function additive for both vanadium trap and SO_x removal. The optimum amount of La/spinel added to the cracking catalyst is about 15% by weight. This results in an increased catalytic activity, an increase in gasoline yield, and a decrease in coke and gas factors. The MgAl₂O₄ phase of Mg/Al₂O₃ additive is found capable of trapping vanadium while its MgO of Mg/Al₂O₃ phase can migrate to zeolite particles (the active component of the FCC catalyst) that, in turn, causes a decline in the activity of that catalyst.     

Aromatic reduction of residue oil of naphtha cracking over bimetallic Pt−Pd catalysts supported on mesoporous molecular sieve

An Al-containing mesoporous molecular sieve (Al-MMS) was prepared by hydrolysis of H₂SiF₆ and Al(NO₃)₃·9H₂O. NH₃-TPD results suggest that the acidity of Al-MMS was less than that of dealuminated zeolite. Y. The potential use of mesoporous molecular sieve as a new support material for dearomatization of residue oil of naphtha cracking was described. In case of C₉ ⁺ and PGO feed, Pt?Pd/Al-MMS showed a higher activity than Pt?Pd/dealuminated zeolite Y catalyst. This is ascribed to its better accessibility of bulky molecules, and much less cracking activity due to mild acidity, indicating high yield of liquid. Thus, Pt?Pd/Al-MMS catalyst can be applied effectively to the hydrogenation of aromatic compounds in the residue oil of a commercial naphtha cracker.     

Effect of acid strength distribution on conversion of FCC gasoline over a ZSM-5 zeolite catalyst

Summary Acid strength distribution and the distribution of aromatics formed in the FCC gasoline conversion reaction on a ZSM-5 zeolite with different Na contents have been studied. With increasing Na content in the ZSM-5 zeolite, the acid sites determined by NH₃-TPD technique, especially the strong acid sites, clearly decrease. When used as catalyst for the aromatization reaction, the transformation of olefins in the FCC gasoline into aromatics is governed directly by the strong acid sites on the ZSM-5 catalyst. Only under the conditions that a ZSM-5 catalyst possesses suitable strong acid sites is reaction temperature favorable for the aromatics formed.     

Dispersion and Orientation of Zeolite ZSM‐5 Crystallites within a Fluid Catalytic Cracking Catalyst Particle

Confocal fluorescence microscopy was employed to selectively visualize the dispersion and orientation of zeolite ZSM‐5 domains inside a single industrially applied fluid catalytic cracking (FCC) catalyst particle. Large ZSM‐5 crystals served as a model system together with the acid‐catalyzed fluorostyrene oligomerization reaction to study the interaction of plane‐polarized light with these anisotropic zeolite crystals. The distinction between zeolite and binder material, such as alumina, silica, and clay, within an individual FCC particle was achieved by utilizing the anisotropic nature of emitted fluorescence light arising from the entrapped fluorostyrene‐derived carbocations inside the zeolite channels. This characterization approach provides a non‐invasive way for post‐synthesis characterization of an individual FCC catalyst particle in which the size, distribution, orientation, and amount of zeolite ZSM‐5 aggregates can be determined. It was found that the amount of detected fluorescence light originating from the stained ZSM‐5 aggregates corresponds to about 15 wt %. Furthermore, a statistical analysis of the emitted fluorescence light indicated that a large number of the ZSM‐5 domains appeared in small sizes of about 0.015–0.25 μm², representing single zeolite crystallites or small aggregates thereof. This observation illustrated a fairly high degree of zeolite dispersion within the FCC binder material. However, the highest amount of crystalline material was aggregated into larger domains (ca. 1–5 μm²) with more or less similarly oriented zeolite crystallites. It is clear that this visualization approach may serve as a post‐synthesis quality control on the dispersion of zeolite ZSM‐5 crystallites within FCC particles.     

丙烯水合反应中改性β沸石催化剂的酸性与催化活性

经酸交换，水蒸气处理及加入粘合剂后的催化剂表面酸性均比Ｈβ原粉要低，主要是Ｂ酸变化较为明显。β沸石在酸洗过程中，酸量降低较大，Ｂ酸下降幅度较大，这可能是与其脱铝程度明显有关。经水蒸汽处理后，除在４００℃水蒸汽处理下酸量变化不大外，其余均有所下降。     

A Cationic Oligomer as an Organic Template for Direct Synthesis of Aluminosilicate ITH Zeolite

There are a large number of zeolites, such as ITH, that cannot be prepared in the aluminosilicate form. Now, the successful synthesis of aluminosilicate ITH zeolite using a simple cationic oligomer as an organic template is presented. Key to the success is that the cationic oligomer has a strong complexation ability with aluminum species combined with a structural directing ability for the ITH structure similar to that of the conventional organic template. The aluminosilicate ITH zeolite has very high crystallinity, nanosheet‐like crystal morphology, large surface area, fully four‐coordinated Al species, and abundant acidic sites. Methanol‐to‐propylene (MTP) tests reveal that the Al‐ITH zeolite shows much higher selectivity for propylene and longer lifetime than commercial ZSM‐5. FCC tests show that Al‐ITH zeolite is a good candidate as a shape‐selective FCC additive for enhancing propylene and butylene selectivity.     

Methanol-to-hydrocarbons conversion over MoO3/H-ZSM-5 catalysts prepared via lower temperature calcination: a route to tailor the distribution and evolution of promoter Mo species,and their corresponding catalytic properties

A series of MoO₃/H-ZSM-5 (Si/Al = 25) catalysts were prepared via calcination at a lower-than-usual temperature (400 °C) and subsequently evaluated in the methanol-to-hydrocarbon reaction at that same temperature. The catalytic properties of those catalysts were compared with the sample prepared at the more conventional, higher temperature of 500 °C. For the lower temperature preparations, molybdenum oxide was preferentially dispersed over the zeolite external surface, while only the higher loading level of MoO₃ (7.5 wt% or higher) led to observable inner migration of the Mo species into the zeolite channels, with concomitant partial loss of the zeolite Brønsted acidity. On the MoO₃ modified samples, the early-period gas yield, especially for valuable propylene and C₄ products, was noticeably accelerated, and is gradually converted into an enhanced liquid aromatic formation. The 7.5 wt% MoO₃/H-ZSM-5 sample prepared at 400 °C thereby achieved a balance between the zeolite surface dispersion of Mo species, their inner channel migration and the corresponding effect on the intrinsic Brønsted acidity of the acidic zeolite. That loading level also possessed the highest product selectivity (after 5 h reaction) to benzene, toluene and xylenes, as well as higher early-time valuable gas product yields in time-on-stream experiments. However, MoO₃ loading levels of 7.5 wt% and above also resulted in earlier catalyst deactivation by enhanced coke accumulation at, or near, the zeolite channel openings. Our research illustrates that the careful adoption of moderate/lower temperature dispersion processes for zeolite catalyst modification gives considerable potential for tailoring and optimizing the system''s catalytic performance.     

氟硅酸铵改性纳米HZSM-5分子筛催化甲醇制丙烯

在静态条件下, 采用不同浓度的氟硅酸铵溶液对纳米ZSM-5分子筛进行了改性处理. 利用粉末X射线衍射(XRD)、²⁷Al 魔角旋转固体核磁共振(²⁷Al MAS NMR)、X射线荧光光谱(XRF)、X射线光电子能谱(XPS)、N₂ 吸附、透射电镜(TEM)、NH₃程序升温脱附(NH₃-TPD)、吡啶吸附红外光谱(Py-IR)等技术对改性前后纳米ZSM-5分子筛的骨架结构、织构性质、酸性质进行了表征. 并在常压、反应温度为450℃、甲醇质量空速(WHSV)为1 h^-1的条件下, 研究了改性前后纳米HZSM- 的甲醇制丙烯(MTP)催化性能. 结果表明, 合适浓度的氟硅酸铵处 理能够选择性地脱除纳米ZSM-5 分子筛的外表面铝, 从而使得HZSM-5 的酸密度降低, 比表面积和孔容增大, MTP催化性能显著提高. 氟硅酸铵改性后纳米HZSM-5 的丙烯选择性和丙烯/乙烯(P/E)质量比分别由原来的 28.8%和2.6提高到45.1%和8.0, 催化剂寿命增加了近2倍.     

Diffusion of Paraffins in Dealuminated Y Mesoporous Molecular Sieve

Mesoporous materials have been intensely studied recently, mainly as possible component for FCC (Fluid Catalytic Cracking) catalysts due to their large surface area and accessibility to large hydrocarbon molecules. It is thus of interest for the oil industry to understand the diffusion behavior of some standard molecules in these materials. Y Zeolites, usually employed in fluid catalytic cracking, can be modified by removal of aluminum atoms from the zeolitic framework to present a greater mesoporous contribution. Dealumination of Y zeolite framework is also known to improve the stability of the catalyst thus making it more suitable for the FCC operation. This study presents diffusion measurements performed with the ZLC (Zero-Length Column) method, developed in the late eighties by Eic and Ruthven (1988a, b). The ZLC method has been largely used for a number of systems, either in gas or in liquid phases. We have now applied the ZLC method for gas phase diffusion measurements of linear paraffins (C₇–C₁₀) in dealuminated Y zeolite (USY). Experimental data were obtained at different temperatures (150 to 240°C) and flow rates (40 to 120 ml/min) and correlated through a transient Fickian diffusion model.