Core-shell-structured Composite ZSM-5@MCM-41 Catalysts:Fabrication,Characterization,and Enhanced Performance in Hexane Catalytic Cracking

A series of core-shell zeolites with a ZSM-5 zeolite core and a MCM-41 shell with varying shell thicknesses were successfully fabricated via a cetyltrimethylammonium bromide(CTAB)-directed sol-gel coating method in an ultradilute solution. Extensive characterization techniques, including XRD, TEM, N_(2) adsorption-desorption, NH_(3)-TPD, and IR measurements, confirmed the successful coating of a microporous ZSM-5 core with a mesoporous MCM-41 shell layer and were further employed to explore the textural properties and acidic properties of the samples. The hexane cracking results revealed a significant enhancement in olefin yields after introducing the MCM-41 shell to ZSM-5. Interestingly, a volcanic trend in olefin yields was observed with the increase in the shell thickness. In particular, the highest olefin yield of 51.5%, exceeding that of the core catalyst by 17.1%, was achieved when the shell thickness was controlled at 40 nm.Moreover, the catalyst lifetime investigation revealed that the core-shell composite catalyst exhibited a minimal reduction in hexane conversion of merely 3.8% over a 120 h reaction period, significantly outperforming the 11.3% reduction exhibited by the core catalyst. This remarkable catalytic performance was attributed to the passivation of external acid sites and the introduction of more developed pore channels by the shell, which effectively mitigated unwanted side reactions. The successful synthesis of these core-shell structured catalysts presents a novel strategy for improving catalytic performance in hexane cracking, in addition to serving as a solid foundation for the design of industrial catalysts for light naphtha cracking.

Effects of Calcination Temperature on the Acidity and Catalytic Performances of HZSM-5 Zeolite Catalysts for the Catalytic Cracking of n-Butane

The acidic modulations of a series of HZSM-5 catalysts were successfully made by calcination at different treatment temperatures, i.e. 500, 600, 650, 700 and 800 ℃, respectively. The results indicated that the total acid amounts, their density and the amount of B-type acid of HZSM-5 catalysts rapidly decreased, while the amounts of L-type acid had almost no change and thus the ratio of L/B was obviously enhanced with the increase of calcination temperature （excluding 800 ℃）. The catalytic performances of modified HZSM-5 catalysts for the cracking of n-butane were also investigated. The main properties of these catalysts were characterized by means of XRD, N2 adsorption at low temperature, NH3-TPD, FTIR of pyridine adsorption and BET surface area measurements. The results showed that HZSM-5 zeolite pretreated at 800 ℃ had very low catalytic activity for n-butane cracking. In the calcination temperature range of 500-700 ℃, the total selectivity to olefins, propylene and butene were increased with the increase of calcination temperature, while, the selectivity for arene decreased with the calcination temperature. The HZSM-5 zeolite calcined at 700 ℃ produced light olefins with high yield, at the reaction temperature of 650 ℃ the yields of total olefins and ethylene were 52.8% and 29.4%, respectively. Besides, the more important role is that high calcination temperature treatment improved the duration stability of HZSM-5 zeolites. The effect of calcination temperature on the physico-chemical properties and catalytic performance of HZSM-5 for cracking of n-butane was explored. It was found that the calcination temperature had large effects on the surface area, crystallinity and acid properties of HZSM-5 catalyst, which further affected the catalytic performance for n-butane cracking.

Study on Catalytic Cracking of Cyclohexane to Produce Light Olefins

Catalytic cracking of cyclohexane(CHA) over ZSM-5, Beta, and USY zeolite catalysts was examined in a fixed fluidized bed reactor(ACE) at 773 K. The adsorption of cyclohexane in ZSM-5, Beta, and USY catalysts was investigated by IR spectroscopy. The IR results demonstrated that the zeolite structure has a remarkable influence on adsorption. Beta zeolite has stronger adsorption of cyclohexane than ZSM-5 and USY zeolites. During the cracking of cyclohexane, path Ⅰ(cyclohexane →methycyclopentane →light olefins) and path Ⅱ(cyclohexane → cyclohexene → light olefins) were found as two important reaction pathways to produce light olefins. A mixture of ZSM-5 and Beta zeolites is better suited for path Ⅰ, and a combination of ZSM-5 and USY zeolites is suitable for path Ⅱ. When pathway Ⅰ and pathway Ⅱ had the same proportion in cyclohexane conversion, pathway Ⅱ would be a better choice for light olefins production.

Catalytic Cracking Characteristics of Plant Oil for Producing Light Olefins and Light Aromatics

Catalyst containing shape selective zeolite is used to investigate the catalytic cracking characteristics of palm oil and three types of hydrocarbon VGOs on a fixed fluidized bed(FFB) unit. The advantage of producing light olefins and light aromatics by catalytic cracking of plant oil is discussed. Results indicate that the hydrocarbyl group of the plant oil molecule is quite readily crackable; the C_6—C_8 aromatics yield is well above and the light olefins yield is about the same with the hydrocarbon feeds, while the yields of low value products are lower; the hydrocarbyl group of the plant oil molecule has strong tendency of aromatization, and can enter the zeolite pores to selectively form C_6—C_8 aromatics; during catalytic cracking of plant oil and fatty acids, a portion of the oxygen is removed in the form of water through hydrogen transfer reaction, while olefins are prevented from being saturated, which can ensure proper yields of both low-carbon olefins and light aromatics.

Targeted Catalytic Cracking to Olefins(TCO):Reaction Mechanism,Production Scheme,and Process Perspectives

Light olefins are important organic building blocks in the chemicals industry.The main low-carbon olefin production methods,such as catalytic cracking and steam cracking,have considerable room for improvement in their utilization of hydrocarbons.This review provides a thorough overview of recent studies on catalytic cracking,steam cracking,and the conversion of crude oil processes.To maximize the production of light olefins and reduce carbon emissions,the perceived benefits of various technologies are examined.Taking olefin generation and conversion as a link to expand upstream and downstream processes,a targeted catalytic cracking to olefins(TCO)process is proposed to meet current demands for the transformation of oil refining into chemical production.The main innovations of this process include a multiple feedstock supply,the development of medium-sized catalysts,and a diameter-transformed fluidizedbed reactor with different feeding schemes.In combination with other chemical processes,TCO is expected to play a critical role in enabling petroleum refining and chemical processes to achieve low carbon dioxide emissions.

Catalyst for Increasing Ethylene and Propylene Production and Its Industrial Application in a Catalytic Pyrolysis Unit

Light olefins,particularly ethylene and propylene,are the most important building blocks for the petrochemical industry,and demand for their production has been increasing.The catalytic pyrolysis process(CPP)and the corresponding catalyst,developed by SINOPEC Research Institute of Petroleum Processing Co.,Ltd.,are designed to maximize the light olefin yield from catalytic cracking of heavy feedstocks.However,owing to the continuing degradation of feedstocks,the original catalyst can no longer maintain its activity.Herein,we describe the rational design of the new catalyst,Epylene,from a new metal-modified hierarchical ZSM-5 zeolite and matrix.Epylene was tested in the CPP unit of Shaanxi Yanchang Coal Yulin Energy and Chemical Company.A test run and base run were conducted to demonstrate the better performance of Epylene compared with the original catalyst.The properties of the feedstocks and the operating conditions in both runs were similar.The light olefin yield was increased from 33.95%to 36.50%and the coke yield was only 9.58%in the test run,which was lower than that in the base run.

Study on reformulation of fluid catalytic cracking gasoline and increasing production of light olefins

The effects of reaction temperature,mass ratio of catalystto oil,space velocity,andmass ratio of water to oil on the product distribution,the yields of light olefins(light olefins including ethylene,propylene and butylene)and the composition of the fluid catalytic cracking(FCC)gasoline upgraded over the self-made catalyst GL in a confined fluidized bed reactor were investigated.The experimental results showed that FCC gasoline was obviously reformulated under appropriate reaction con-ditions.The olefins(olefins with C atom number above 4)content of FCC gasoline was markedly reduced,and the aromaticscontent andoctanenumber were increased.The upgraded gasoline met the new standard of gasoline,and meanwhile,higher yields of light olefins were obtained.Furthermore,higher reaction temperature,higher mass ratio of catalyst to oil,higher mass ratio of water to oil,and lower space velocity were found to be beneficial to FCC gasoline reformulation and light olefins production.

Conversion of Benzene in the Catalytic Cracking Process

The catalytic cracking of 1-hexene,1-heptene,1-octene,1-nonene,1-decene,and five olefins mixed with benzene,over USY catalysts was conducted in a small fixed fluidized bed reactor to study the conversion of benzene under catalytic cracking conditions.Benzene mainly alkylated with C_(2)-C_(5)light olefins,generating monosubstituted alkylbenzenes,and the concentration of light olefins dramatically affected the alkylbenzene yield.Due to the limitation of thermodynamic equilibrium,the yield of benzene alkylation to alkylbenzene in catalytic cracking was in a relative low level.The equilibrium constant of benzene alkylation decreases with the increasing reaction temperature which resulted in reduction of alkyl benzene yield.

Industrial Application and Fundamental Research Progress on Fluid Catalytic Cracking Technology of Downer Reactors

Fluid catalytic cracking(FCC)technologies of downer reactors,which have reached the demonstration or commercial scale,are systematically discussed,i.e.,millisecond catalytic cracking,fluidization lab of Tsinghua University,and high-severity FCC.Moreover,aiming to promote industrial application,the fundamental studies are comprehensively described,particularly focusing on high-density downer reactors,clusters,and up-scaling.Furthermore,from the perspective of industrial application,some research directions toward further developments are suggested.

Synergism of Titanium in MFI Zeolite to Acidity with Its Appliance to N-Hexane Catalytic Cracking Reaction

Catalytic cracking of naphtha is now a process of huge development potential to produce light olefins, which are important basic raw materials used in various industries, but current industrial catalysts like ZSM-5 zeolites suffer from low selectivity and high energy consumption. Here, Ti/Al-containing nanosize MFI-structure zeolites in-situly synthesized through one-pot method were applied to the catalytic cracking using n-hexane as the model reactant. The maximum mass yield of combined light olefins reaches 49.2% with 99% conversion at 600°C and 1 atm. Multiple characterizations are used to identify the Ti-related active species and their effect on the performance. It was found that a higher proportion of LAS caused by Ti was beneficial to the activation of reactant, and the slightly increased amount of BAS leaded to more alkanes converting into light olefins. This understanding may open new opportunities for design and modification of catalytic cracking catalysts.

Development and Application of DCC Catalysts to Meet New Demands

The new generation of DCC catalysts, the DMMC/RMMC series catalysts developed by RIPP are introduced in this paper. The large molecule cracking ability is enhanced by increasing the portion of large pores; and the coke selectivity is improved by adjusting the acidity site density on the matrix surface, while the selective cracking reactions are increased. The sphericity of catalysts is improved by adopting new preparation method. The commercial application results have shown that applying DMMC/RMMC series catalysts with the mixed VGO, VGO plus AR, and hydrotreated VGO feed can increase the propylene yield by 2.43, 1.3 and 0.8 percentage points, respectively, as compared to the previous catalysts along with improvement in some products yields. The refining enterprises can make more profits after applying new series of DCC catalysts.

Commercial Test of HGY-2000R FCC Catalyst for Maximizing Gasoline Yield

HGY-2000R catalyst developed by Research Institute of Petroleum Processing, SINOPEC wastested in the RFCC unit, Ulsan complex, SK Corporation, Korea from July to August 2002. The primaryresults of commercial test show that it has good performance of higher activity, good hydrothermal stability,higher residue cracking ability, good coke selectivity and good fluidization properties as well as maximizinggasoline yield with a lower olefin content.

Development of MIP Technology and Its Proprietary Catalysts

A novel catalytic cracking process named the MIP process was developed by the Research Institute of Petroleum Processing(RIPP),SINOPEC,to manufacture clean gasoline with lower olefin contents. The MIP pro-cess features a unique riser consisting of two sequential reaction zones with different radii,in which different kinds of chemical reactions are intensified respectively to achieve better product slates and product properties. In order to fully implement the MIP potentials,a proprietary catalyst RMI tailored to the needs of the MIP process was devel-oped by adopting an AIRY zeolite having improved accessibility to active sites,which could result in better heavy oil cracking,coke selectivity and olefin reduction performance compared with the conventional REUSY zeolite. Its commercial application showed that the RMI catalyst could further reduce the olefin content in gasoline and raise the gasoline octane number while increasing the total liquid yield. On the basis of the MIP process,the MIP-CGP process was also developed to significantly reduce the olefin content in FCC naphtha and to enhance the propylene yield simultaneously. As far as the MIP-CGP process itself is concerned,both the MIP-CGP process and the MIP process have the similar reactor configuration but with different reactor size and operating parameters. The proprietary catalyst CGP-1 is also proposed to tailor for the MIP-CGP process. The specific features of the CGP-1 catalyst cover the new matrix,which possesses excellent capability to accommodate coke formation in the first reaction zone;the modified Y zeolite,which exhibits high hydrogen transfer activity in the second reaction zone;and the MFI zeolite,which has good gasoline olefin cracking activity. The commercial test results of MIP-CGP process applied along with the CGP-1 catalyst showed that the olefin content of gasoline was less than 18 v% and the propylene yield was more than 8 m%. Furthermore,as compared with the conventional FCC process,the gasoline properties were improved greatly and a higher total liquid yield was obtained. The advantages and characteristics of the MIP-CGP process were fully exploited by using the CGP-1 catalyst.

MMC——High Propylene Selectivity DCC Catalyst

RIPP 开发了催化剂在增加丙烯收益瞄准了的第三根产生小说两重棉包线，作为 MMC 系列催化剂说出。这催化剂具有作为主要活跃部件由 ZSP 沸石组成的 MFIstructure，它为生产低碳的石蜡有更高的能力，特别地丙烯。在 SINOPEC Anqing 石油化学的同伴的这催化剂的商业应用程序表明了 MMC-2 催化剂的采纳导致了百分比以化工物品性质在基本上类似的条件下面在丙烯产量增加的 1.6-4.0 ，进程操作政体在在芳香的内容的汽油石蜡内容和增加结合了减小改进汽油质量。

Light olefin production by catalytic co-cracking of Fischer–Tropsch distillate with methanol and the reaction kinetics investigation

Catalytic co-cracking of Fischer–Tropsch(FT) light distillate and methanol combines highly endothermic olefin cracking reaction with exothermic methanol conversion over ZSM-5 catalyst to produce light olefins through a nearly thermoneutral process. The kinetic behavior of co-cracking reactions was investigated by different feed conditions: methanol feed only, olefin feed only and co-feed of methanol with olefins or F–T distillate. The results showed that methanol converted to C2–C6 olefins in first-order parallel reaction at low space time, methylation and oligomerization–cracking prevailed for the co-feed of methanol and C2–C5 olefins, while for C6–C8 olefins,monomolecular cracking was the dominant reaction whether fed alone or co-fed with methanol. For FT distillate and methanol co-feed, alkanes were almost un-reactive, C3–C5 olefins were obtained as main products, accounting for 71 wt% for all products. A comprehensive co-cracking reaction scheme was proposed and the model parameters were estimated by the nonlinear least square method. It was verified by experimental data that the kinetic model was reliable to predict major product distribution for co-cracking of FT distillate with methanol and could be used for further reactor development and process design.

Effects of Operating Conditions on the Catalytic Performance of HZSM-5 Zeolites in n-Pentane Cracking

In this work,n-pentane catalytic cracking over HZSM-5 zeolites was studied at 650°C under atmosphere pressure.A particular attention was paid to the measurement of n-pentane conversion,light olefins production,product distribution,coke deposit,etc.Several indexes were defined to evaluate the effects of operating conditions on the catalytic performance of HZSM-5 zeolites.It was found that decreasing the weight hourly space velocity,increasing the reactant partial pressure,and increasing the carrier gas flow rate could inhibit C-H bond breaking and enhance the C-C bond breaking and hydride transfer reactions,leading to reduced alkenes selectivity,which suppressed the formation of external coke and alleviated the deactivation of HZSM-5 zeolites.It was deduced that the catalytic stability of HZSM-5 zeolites was improved at the cost of alkenes selectivity.Compared with decreasing the weight hourly space velocity and increasing the reactant partial pressure,increasing the carrier gas flow rate could enhance the diffusion process and protect alkenes from being consumed in coke formation in order to improve the catalytic stability of HZSM-5 zeolites with less reduction of alkenes selectivity.

基质Lewis酸性调控及其催化轻烃裂化反应性能

催化剂分子筛和基质的合理匹配是提高石脑油催化裂化制低碳烯烃产量的最有效路径之一,但是基质表面Lewis酸性对裂化反应的影响尚未明确。本研究通过硼和锌改性γ-Al_(2)O_(3)和锡改性KIT-6介孔氧化硅材料调变表面的Lewis酸,研究基质及其与ZSM-5分子筛配合使用时催化正庚烷和1-己烯裂化制低碳烯烃的性能。采用XRD、TEM、N2物理吸附-脱附以及NH3-TPD等方法探讨了改性γ-Al_(2)O_(3)和KIT-6的结构性质和表面酸性质。结果表明,B可以降低γ-Al_(2)O_(3)的表面Lewis酸性(酸量和酸强度),而Zn可以增强其表面酸性;此外,Sn可以提高有序介孔KIT-6表面Lewis酸性。催化裂化反应结果表明,当基质单独使用时,随基质表面Lewis酸性增强,轻烃反应活化能降低且转化率升高;当基质与ZSM-5配合使用时,基质在上分子筛在下的双床层排布方式对应的转化率最高,且随基质Lewis酸性增强,轻烃转化率升高,但Lewis酸性过强会加速氢转移反应,降低低碳烯烃的选择性。

C_(4)烯烃转化制丙烯工艺及催化剂研究

目的开发C_(4)烯烃催化裂解制丙烯工艺和催化剂制备工艺技术,完成小试和工业侧线试验。方法采用固定床评价装置考查了催化剂配方、改性及工业条件对催化剂活性、选择性、稳定性能的影响。结果以ZSM-5分子筛为活性组分的催化剂在C_(4)烯烃转化制丙烯反应中具有较好的活性、选择性、稳定性和再生性,磷的引入未改变催化剂的晶型结构,但降低了催化剂酸性位点数量,并调节了催化剂的n(B酸)/n(L酸),随着磷负载量增加到5%(w),分子筛中磷与铝的相互作用逐渐增强,磷可以和骨架铝和非骨架铝相互作用。结论C_(4)烯烃的转化率达到80%以上,丙烯的选择性达到35%~45%,催化剂的单程寿命达到一个月以上,且经再生后,再生恢复率达95%。

多级孔花状ZSM-5分子筛的合成及其正辛烷催化裂解反应性能研究

高性能催化剂的研发是石脑油催化裂解制低碳烯烃领域的研究热点。使用双子季胺盐表面活性剂[C_(18)H_(37)-N^(+)(CH_(3))_(2)-C_6H_(12)-N^(+)(CH_(3))_(2)-C_6H_(13)]Br_(2)作为结构导向剂,成功合成了花状ZSM-5分子筛。利用XRD、SEM、N_(2)吸附-脱附和NH_(3)-TPD表征技术研究了晶化温度、n(Si)/n(Al)、n(H_(2)O)/n(Si O_(2))和n(Na_(2)O)/n(Si O_(2))等合成条件对ZSM-5分子筛物化性质的影响,并考察其正辛烷催化裂解反应性能。研究结果表明,花状ZSM-5分子筛的优化制备条件为:n(Na_(2)O)∶n(Al_(2)O_(3))∶n(Si O_(2))∶n(C_(18-6-6)Br_(2))∶n(H_(2)O)=5∶1∶100∶10∶4000、晶化时间为72 h、晶化温度为175℃。随着n(Si)/n(Al)的增大,花状分子筛颗粒逐渐团聚;当投料n(Na_(2)O)/n(Si O_(2))高于0.05时,分子筛样品中开始出现其他杂相;随着投料n(H_(2)O)/n(Si O_(2))的增大,分子筛层状形貌逐渐不明显。在催化裂解正辛烷制乙烯和丙烯反应中,经过30 h连续测试,花状ZSM-5分子筛的正辛烷转化率始终保持稳定,乙烯和丙烯总收率从62.0%逐渐增加至64.4%。花状ZSM-5分子筛较高的催化活性和优异的抗积炭稳定性主要归结于其独特的层状形貌和多级孔结构。

不同结构分子筛对正己烷催化裂解反应性能的影响

对不同结构分子筛IM-5,Al-ITQ-13,USY和ZSM-23的物相、孔结构、晶粒形貌及酸性质进行了对比分析,并在固定床微反装置上对上述4种分子筛催化正己烷裂解反应性能进行了评价。结果表明:4种分子筛均为纯相,具有较高的结晶度,USY具有最大的比表面积、孔体积和酸量,ZSM-23的比表面积和孔体积最小,Al-ITQ-13的酸量最低;USY和IM-5的正己烷转化率较高,说明酸性质与反应活性直接相关,Al-ITQ-13的低碳烯烃总收率和选择性最高,说明低碳烯烃选择性与酸量和孔结构密切相关;具有适宜酸量、较小孔径的Al-ITQ-13在正己烷催化裂解反应中表现出增产低碳烯烃的优异催化性能。