共查询到18条相似文献,搜索用时 140 毫秒
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简要介绍了广泛应用于石油化工和工业催化中的沸石分子筛的特点以及多级孔沸石分子筛的基本合成策略,包括“自上而下”和“自下而上”两类合成策略;重点介绍了近年来发展出来的新型双功能模板法合成策略,包括如何利用季铵基团表面活性剂双功能模板,特别是利用聚合物双功能模板来直接合成不同拓扑结构的多级孔沸石分子筛的最新研究进展,以及两类双功能模板合成多级孔沸石的特点和优点。最后,对多级孔沸石分子筛在合成条件优化、模板剂选择、合成机理探究等方面所面临的挑战和在工业催化实际条件下的稳定性应用前景进行了展望。 相似文献
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相比传统ZSM-5分子筛,多级孔ZSM-5分子筛具有空间位阻小、传质效率高、焦炭少等特点,近年来在分子筛领域应用广泛。多级孔分子筛通常可用后处理法和模板剂法制备,相比后处理法,模板剂法能更好地控制介孔的结构和孔道尺寸。概述了采用传统表面活性剂、两亲性的有机硅烷、双功能多季铵盐表面活性剂及高分子聚合物等软模板法合成多级孔ZSM-5分子筛的研究进展。分析不同软模板剂的特点和作用机理,阐述了合成后分子筛的结构特点及催化性能等。指出在今后的研究中,可以设计价格较低的新型功能化模板剂,优化合成过程,致力于在理解合成机理的前提下,寻找操作简单、绿色环保的合成路线,并将其推行到实际工业生产中。 相似文献
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多级孔道ZSM-5分子筛的合成及其催化应用 总被引:1,自引:0,他引:1
多级孔道ZSM-5分子筛具有微孔沸石分子筛良好的择形催化性能和介孔材料优异的传质扩散性能,在催化领域显示出良好的应用前景。本文综述了近年来多级孔道ZSM-5分子筛的研究进展,重点介绍了多级孔道ZSM-5分子筛的不同合成方法,包括后处理法、硬模板法和软模板法等,同时介绍了不同方法得到的多级孔道ZSM-5分子筛在催化反应中的应用,分析表明多级孔道ZSM-5分子筛以其良好的扩散性能和适宜的酸性提高了反应转化率和目标产物选择性。最后对多级孔道ZSM-5分子筛的发展方向进行了展望,指出研发简单、经济和环保的新合成路线是多级孔道ZSM-5分子筛发展中的重大挑战,深入研究多级孔道分子筛中介孔的形成机理和开发具有多级孔道整体式催化剂以及负载型多级孔道ZSM-5分子筛是今后的研究重点。 相似文献
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以四丙基氢氧化铵、四丙基溴化铵、正丁胺和季戊四醇为模板剂水热合成ZSM-5分子筛,采用XRF、XRD、SEM、NH3-TPD、Py-FTIR和27Al MAS NMR等进行了表征,研究了模板剂对ZSM-5分子筛性质及甲醛制三聚甲醛催化性能的影响。结果表明,通过改变模板剂可改变ZSM-5分子筛的酸中心分布、表面酸性质和粒径;较大空间的孔道交叉位置的酸性中心、小催化剂粒径和高表面B酸/L酸比值有利于提高三聚甲醛选择性。以四丙基氢氧化铵为模板剂合成的ZSM-5分子筛的颗粒尺寸为240nm×240nm×150nm,分布于直形孔道和S形孔道的孔道交叉处的Br?nsted酸中心较多,甲醛转化率和三聚甲醛的选择性分别为30.15%和88.35%。 相似文献
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在丁烯异构化反应催化剂中,镁碱沸石分子筛由于具有十元环和八元环交错的独特的二维孔道结构、良好的水热稳定性和化学稳定性、较高的选择性等诸多优点受到广泛关注;但由于有机模板剂的影响,在环境友好方面有所欠缺。本文综述了镁碱沸石(FER)的合成方法:有机模板剂合成法、非模板剂合成法、层状前体合成法、乳化剂控制合成法,归纳比较了各种合成方法的优缺点,阐述了FER的合成后处理方式,指出采用无毒无害的原材料替代有机合成模板剂,从而提高镁碱沸石分子筛的催化性能,对环境友好大大改善,是未来研究镁碱沸石分子筛催化剂的发展方向之一。 相似文献
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Huan Wang Guo Du Jiaqing Jia Shaohua Chen Zhipeng Su Rui Chen Tiehong Chen 《Frontiers of Chemical Science and Engineering》2021,15(6):1444
Hierarchically porous zeolites are promising candidates in catalytic conversion of relatively bulky molecules, and their syntheses have attracted significant attention. From both industrial and scientific perspectives, different carbon materials have been widely employed as hard templates for the preparation of hierarchically porous zeolites during the past two decades. In this review, the progress in synthetic strategies using carbon materials as templates is comprehensively summarized. Depending on the affinity between the carbon templates and zeolite precursors, the substantial strategies for synthesizing hierarchical zeolites are introduced in direct templates and indirect templates. Direct templates methods, by which the carbon materials are directly mixed with precursors gel as hard templates, are first reviewed. Then, we discuss the indirect templates method (crystallization of carbon-silica composites), by which the carbon is produced by in situ pyrolysis of organic-inorganic precursors. In addition, the technique of encapsulating metal species into zeolites crystals with the assistance of carbon templates is also discussed. In the conclusion part, the factors affecting the synthesis of carbon-templated hierarchically porous zeolites are remarked. This review is expected to attract interest in the synthesis strategies of hierarchically porous zeolites, especially cost-effective and large-scale production methodologies, which are essential to the industrial application of hierarchical zeolites. 相似文献
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E. V. Parkhomchuk K. A. Sashkina N. A. Rudina N. A. Kulikovskaya V. N. Parmon 《Catalysis in Industry》2013,5(1):80-89
The synthesis of macroporous supports using nanosized templates, which are then removed from the final product by burning or dissolution, has been extensively developed since 1997. Here, we report the template synthesis of 3D-structured macroporous supports of different chemical natures, namely, alumina, titanium and zirconium dioxides, and hierarchical silicalite and Fe-silicalite with the zeolite ZSM-5 structure. The templates consist of monodisperse, close-packed, polystyrene spheres 250 to 1150 nm in diameter. The template synthesis affords a marked increase in the specific pore volume and in the external surface area of the porous oxides. The pore volume of granular alumina samples obtained in the absence and in the presence of the polystyrene template is 0.34 and 1.22 cm3/g, respectively. The specific external surface area of Fesilicalite with the ZSM-5 structure increases from 26.8 to 410 m2/g on passing from the sample synthesized without a template to the sample prepared in the presence of the polystyrene template. The textural properties of the new materials are very promising for adsorption and catalytic processes involving macromolecular compounds, such as catalytic refining of heavy petroleum fractions and biomass and lignin conversion into chemical products, including liquid hydrocarbons; for the pharmaceutical industry; and for adsorption of large molecules, including heavy metals, from aqueous solutions. 相似文献
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Ilbige C. Arik Joeri F. Denayer Gino V. Baron 《Microporous and mesoporous materials》2003,60(1-3):111-124
The influence of the composition and synthesis method on the low-coverage adsorption properties of C5–C9 n-alkanes on ZSM-5 zeolites was studied using the pulse chromatographic technique at temperatures between 200 and 400 °C. Experiments were performed with materials having Si/Al ratios between 12 and 400, synthesized with and without an organic template. For all ZSM-5 samples, the Henry adsorption constants increase exponentially with the carbon number, while zero-coverage adsorption enthalpies increase in a linear way. With decreasing Al content, the Henry constants and adsorption enthalpies decrease. An increase in adsorption enthalpy of 10.1 kJ/mol per added –CH2– group is observed for an Si/Al ratio of 400, while an increase of 12.1 kJ/mol is found for an Si/Al ratio of 15. The contribution to the adsorption entropy per carbon atom depends on the ZSM-5 composition and varies between 11.2 and 14.4 J/(mol K). A significant effect of the synthesis method on the Henry constants, adsorption enthalpies and entropies is observed. All ZSM-5 samples synthesized using organic templates show the same unique relationship between adsorption enthalpy and entropy, different from that of zeolites synthesized without organic template. 相似文献
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Suh J 《Accounts of chemical research》2003,36(7):562-570
Effective artificial enzymes have been designed by adopting macromolecular systems for catalyst-substrate complexes. Artificial active sites comprising two or more organic functional groups were built on macromolecular backbones, leading to several types of organic artificial proteases. The activity of metal centers for peptide or DNA hydrolysis was greatly enhanced by attachment to polystyrene, leading to artificial metallopeptidases with substrate selectivity as well as artificial metallonucleases with high catalytic activity for double stranded DNA. A small artificial protease selective for a macromolecular target protein was synthesized. Target-specific artificial proteases can be used as protein-cleaving catalytic drugs. 相似文献
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为了考察硅源对ZSM-5分子筛合成和催化性能的影响,分别采用白炭黑、硅胶、硅溶胶和单分散SiO2为硅源合成ZSM-5分子筛,对合成的ZSM-5分子筛进行XRD、SEM、BET和NH3-TPD表征,并以C4烯烃为原料评价合成的ZSM-5分子筛的催化裂解性能。结果表明,以硅溶胶为硅源合成的ZSM-5分子筛具有较好的结晶度和催化活性。水热处理使分子筛酸量减少,孔容缩小,改善了分子筛的乙烯丙烯选择性。经600 ℃水热处理4 h的ZSM-5分子筛在常压、580 ℃和空速9 h-1反应条件下,丁烯催化裂解为乙烯和丙烯平均转化率为90.2%,乙烯和丙烯总收率达61.1%。 相似文献