共查询到20条相似文献,搜索用时 15 毫秒
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分子筛催化剂上正十六烷的临氢异构化反应 总被引:13,自引:0,他引:13
对分子筛催化剂上正十六烷的临氢异构化反应进行了研究,考察了不同分子筛催化剂的活性和选择性,并对临氢异构化反应的产物分布进行了分析.在此基础上,对正十六烷的临氢异构化反应机理进行了初步探讨.结果表明,正十六烷在中孔分子筛催化剂上的临氢异构化反应主要在分子筛外表面和孔口进行,分子筛的择形作用对异构选择性的影响有限.这与一般情况下低分子量正构烷烃在择形分子筛上的临氢异构化反应有所不同.临氢异构化反应的异构选择性主要取决于催化剂酸性组分的酸性质,弱酸和中等强度的酸对异构化反应有利,而催化剂的活性则由酸性组分中B酸中心的数量和加氢组分的活性共同决定. 相似文献
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DUSY沸石催化α-蒎烯异构化反应的动力学研究 总被引:3,自引:0,他引:3
研究了脱铝超稳Y(DUSY)沸石催化α-蒎烯异构化反应的动力学特征,考察了催化剂的硅铝比及反应温度对速率常数和表现反应活化能的影响。结果表明,α-蒎烯的异构化反应服从准一级动力学模型,速率常数与温度的关系符合A rrhenius方程并存在补偿效应。 相似文献
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无粘结剂ZSM-5沸石催化剂骨架脱铝改性的研究 总被引:1,自引:0,他引:1
对比了无粘结剂和有粘结剂ZSM-5沸石催化剂的吸附性质, 证实前者的优良品质. 以27Al固体核磁共振(MAS NMR)考察了盐酸处理、水蒸气处理及水蒸气-盐酸相结合处理后无粘结剂ZSM-5沸石催化剂的骨架脱铝行为以及非骨架铝的状态. 以X射线粉末衍射(XRD), X射线荧光光谱(XRF), 低温氮吸附, NH3-TPD和吡啶吸附原位红外光谱(in situ IR)等详细表征了骨架脱铝对其晶体、元素组成及孔结构、表面强(S)酸与弱(L)酸、Brönsted(B)酸与Lewis(L)酸酸量分布等影响. 揭示了水蒸气处理的深度骨架脱铝强烈地调变沸石的结构和表面酸性的本质, 证明了该处理方式对调变S酸和B酸起主导作用. 相似文献
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采用连续固定床反应器,考察了几种具有不同酸性和孔道尺寸的分子筛催化剂上丁烯-2齐聚反应的性能,并与固体磷酸(SPA)催化剂进行了对比.结果表明,分子筛催化剂的酸性和孔道尺寸是影响丁烯-2齐聚反应活性和选择性的重要因素.具有八元环孔道的分子筛的扩散阻力大,反应活性很低;十二元环分子筛的孔道降低了扩散阻力,有利于提高催化剂的低温活性和C9= 选择性;十元环分子筛的孔道尺寸和强酸中心可以提高催化剂的活性,促进C9= 生成.SPA催化剂上C9= 选择性低于30%,而具有强酸中心的十元环ZSM-5和ZSM-22分子筛,以及十二元环β分子筛催化剂上可高达50%以上,这说明分子筛催化剂具有更好的齐聚催化性能. 相似文献
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It is a challengeto explore the possibility of developing various novel oxynitrided zeolites in whichoxygen bridging atoms are substituted to some levels by isoelectronic groups…… 《催化学报》2001,22(3):227-228
It is a challenge to explore the possibility of developing various novel oxynitrided zeolites,in which oxygen bridging atoms are substituted to some levels by isoelectronic groups 相似文献
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沸石分子筛催化剂上萘的择形异丙基化反应性能 总被引:17,自引:0,他引:17
研究了HY,Hβ,HM和HZSM-5沸石分子筛对萘择形异丙基化反应的催化性能.结果发现,这些沸石分子筛的活性顺序为HY>Hβ>HM>HZSM-5,对2,6-二异丙基萘的选择性顺序为HM>Hβ>HY.除沸石分子筛的酸量与酸分布外,其孔道结构与大小是影响萘异丙基化反应的主要因素.脱铝能选择性地降低沸石外表面的酸性,且对沸石的催化性能有较大影响.常压水蒸气脱铝结合强酸再处理有利于催化剂催化性能的提高.提高反应温度有利于萘的转化,但温度过高会引发许多副反应,适宜的反应温度约为523K.反应时间对产物分布的影响不明显.异丙醇/萘摩尔比应小于2. 相似文献
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Dirk Mehlhorn Dr. Rustem Valiullin Prof. Dr. Jörg Kärger Kanghee Cho Prof. Dr. Ryong Ryoo 《Chemphyschem》2012,13(6):1495-1499
Specially synthesized extra‐large crystallites of zeolite LTA with intentionally added mesoporosity are used for an in‐depth study of guest diffusion in hierarchical nanoporous materials by the pulsed field gradient NMR technique. Using propane as a guest molecule, intracrystalline mass transfer is demonstrated to be adequately described by a single effective diffusivity resulting from the weighted average of the diffusivities in the two (micro‐ and meso‐) pore spaces. Gas‐kinetic order‐of‐magnitude estimates of the diffusivities are in satisfactory agreement with the experimental data and are thus shown to provide a straightforward means for predicting and quantifying the benefit of hierarchically structured nanoporous materials in comparison with their purely microporous equivalent. 相似文献
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Dr. Ming-Hui Sun Prof. Dr. Li-Hua Chen Shen Yu Prof. Dr. Yu Li Xian-Gang Zhou Dr. Zhi-Yi Hu Prof. Dr. Yu-Han Sun Prof. Dr. Yan Xu Prof. Dr. Bao-Lian Su 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(44):19750-19759
Zeolite Beta single crystals with intracrystalline hierarchical porosity at macro-, meso-, and micro-length scales can effectively overcome the diffusion limitations in the conversion of bulky molecules. However, the construction of large zeolite Beta single crystals with such porosity is a challenge. We report herein the synthesis of hierarchically ordered macro-mesoporous single-crystalline zeolite Beta (OMMS-Beta) with a rare micron-scale crystal size by an in situ bottom-up confined zeolite crystallization strategy. The fully interconnected intracrystalline macro-meso-microporous hierarchy and the micron-sized single-crystalline nature of OMMS-Beta lead to improved accessibility to active sites and outstanding (hydro)thermal stability. Higher catalytic performances in gas-phase and liquid-phase acid-catalyzed reactions involving bulky molecules are obtained compared to commercial Beta and nanosized Beta zeolites. The strategy has been extended to the synthesis of other zeolitic materials, including ZSM-5, TS-1, and SAPO-34. 相似文献
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ZHAOZhen-Hua 《应用化学》2002,19(4):310-312
Beak et al[1 ] reported that the acylation of ethylidenecyclohexane( EDC) using zincchloride as a catalyst gave 3 -( 1 -cyclohexenyl) -2 -butanone( CHB) in good yield.However,it is pity that they provided only little information about reaction conditions,and no information on comparison of activities of various catalysts. Itis well known thatconventional Zn Cl2 catalyst leads to a great number of environmental pollution,whichcould be mainly overcome by use of the solid catalysts as we have … 相似文献
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Measurements have been performed on the influence of a small amount of water on adsorption properties of alkanes (C3 to C6) and olefins (C3 and C4) in NaX zeolite. Adsorption capacity and heat of adsorption have been measured by a Volume Step method. Kinetics has been measured by Thermal Frequency Response method and the results have been compared with the results obtained by PFG-NMR.It has been found that water reduces the adsorption capacity especially at low adsorbate concentration. The heat of adsorption is slightly reduced by water. The kinetics of alkanes is always reduced by the adsorbed water. On the contrary, the diffusion kinetics of olefins is improved or remains unchanged, depending of the sorbat concentration. 相似文献
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沸石分子筛催化苯甲醚与苯甲酰氯的苯甲酰化反应 总被引:2,自引:0,他引:2
分别采用五种H型沸石在无溶剂条件下催化了苯甲醚与苯甲酰氯的苯甲酰化合成4-甲氧基二苯甲酮.各种沸石的酸中心分布和孔道结构各不相同,使其表现出不同的催化效果.Hβ沸石的三维孔道和集中的中强酸中心为反应提供了适宜的条件,使苯甲酰氯的转化率和4-甲氧基二苯甲酮的选择性分别可达99.5%和91.2%.Pyrid ine-FT-IR结果表明B酸中心为H型沸石主要酸中心,H+为催化活性点;NH3-TPD谱图表明中强酸中心是苯甲酰化反应的合适酸中心,据此提出了H型沸石催化苯甲醚苯甲酰基化的反应机理. 相似文献
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Tien T. Tsong 《Progress in Surface Science》2001,67(1-8):235-248
Mechanisms of surface diffusion of single atoms, molecules and atomic clusters on flat terraces (with and without a driving force) of metal and semiconductor surfaces are discussed, focusing on our recent scanning tunneling microscopy (STM) results. Experimental evidence leading to these conclusions is presented. Besides the commonly known hopping mechanism, there are many other mechanisms. In Arrhenius analysis, a linear behavior can be expected for only some of the simpler mechanisms. 相似文献
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Zhongyuan Guo Xin Li Shen Hu Guanghua Ye Xinggui Zhou Marc‐Olivier Coppens 《Angewandte Chemie (International ed. in English)》2020,59(4):1548-1551
Applications of zeolites in catalysis are plagued by strong diffusion resistance, which results from limitations to molecular transport in micropores, across external crystal surfaces, but also across internal interfaces. The first type of diffusion resistance is well understood, the second is receiving increasing attention, while the diffusion barriers at internal interfaces remain largely unclear. We take Pt/Beta catalyzed isomerization of n‐heptane as the model system to explore the role of internal diffusion barriers in zeolite catalysis. The two as‐synthesized Pt/Beta catalysts have an identical Pt loading, similar Beta particle size and acidity, but different internal structures. A Pt/Beta crystal with no observable internal interfaces can be 180 % higher in activity and 22 % higher in selectivity than its counterpart with numerous internal interfaces. This can only be attributed to the strong transport barriers across internal interfaces, as supported by directly comparing the apparent diffusivities of the two Beta samples. 相似文献
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HAlMCM-41介孔分子筛催化1,3-苯并二噁茂烷合成的研究 总被引:1,自引:0,他引:1
研究了HAlMCM-41分子筛催化邻苯二酚与环己酮、丁酮、丙酮、丙醛、丁醛、异丁醛、戊醛、正己醛、正辛醛、苯甲醛、二苯甲酮等十余种醛(酮)的缩合反应. 考察了反应时间、酚与醛(酮)的配比、HAlMCM-41分子筛用量、硅铝比、催化剂重用次数等因素对邻苯二酚与醛(酮)反应的影响. 结果表明, 当邻苯二酚与醛(酮)物质的量比为1∶1.4, 催化剂用量为3.5 g/mol邻苯二酚, 反应4 h, 分子筛n(SiO2)/n(Al2O3)为15时, 选择性一般在99.4%以上, 转化率也一般在85.6%以上, 因此, HAlMCM-41分子筛对邻苯二酚与醛(酮)的反应有较好的催化性能. 相似文献
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本文综述了甲烷无氧芳构化反应及Mo基分子筛催化剂的研究进展。在众多的催化剂中以Mo基分子筛催化性能最佳。概括了催化剂中关于MoO<em>x前躯体结构和其在分子筛中落位,Mo2C物种和诱导期等;讨论了反应中涉及的中间产物、双功能机理以及催化剂失活等问题;归纳了催化剂制备过程中制备方法、焙烧温度与时间、Mo载量和分子筛硅铝比以及催化剂预处理对反应活性的影响;综述了提高催化剂催化性能和反应性能的各种方法,并对其分析,同时介绍了两种催化剂再生方法。最后,依据本实验室研究进展,对甲烷芳构化从工艺角度进行一些可行性讨论,并提出相关问题和展望。 相似文献
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HAIMCM-41介孔分子筛催化1,3-苯并二嗯茂烷合成的研究 总被引:1,自引:0,他引:1
研究了HAlMCM-41分子筛催化邻苯二酚与环己酮、丁酮、丙酮、丙醛、丁醛、异丁醛、戊醛、正己醛、正辛醛、苯甲醛、二苯甲酮等十余种醛(酮)的缩合反应.考察了反应时间、酚与醛(酮)的配比、HA1MCM-41分子筛用量、硅铝比、催化剂重用次数等因素对邻苯二酚与醛(酮)反应的影响.结果表明,当邻苯二酚与醛(酮)物质的量比为1:1.4,催化剂用量为3.5g/mol邻苯二酚,反应4h,分子筛n(SiO_2)/n(Al_2O_3)为15时,选择性一般在99.4%以上,转化率也一般在85.6%以上,因此,HAlMCM-41分子筛对邻苯二酚与醛(酮)的反应有较好的催化性能. 相似文献