The Cu-exchanged SSZ-13 with the small-pore chabazite framework is considered as a highly efficient catalyst for selective catalytic reduction of NO with NH_(3)(NH_(3)-SCR).In order to further improve the catalytic pr...The Cu-exchanged SSZ-13 with the small-pore chabazite framework is considered as a highly efficient catalyst for selective catalytic reduction of NO with NH_(3)(NH_(3)-SCR).In order to further improve the catalytic property,a series of Mn ion-assisted Cu/SSZ-13 powder catalysts were prepared by co-exchange method and stepwise exchange method.It is found that the NH_(3)-SCR activity,N_(2) selectivity,hydrothermal stability and sulfur resistance of Cu/SSZ-13 are promoted by introducing a minority of Mn(0.15%to 0.23%(mass))through co-exchange method.Characterization results reveal that the Cu,Mn co-exchange enables the higher amounts of Cu^(2+)active sites,the abundant medium strong and strong acid,the optimized ratio of Lewis acid to Brønsted acid etc.,which are required for a good NH_(3)-SCR catalytic property over broad temperature range and under harsh working environment.Moreover,a monolithic catalyst was prepared by impregnating a cordierite ceramic support into the coating slurry containing the optimized CuMn/SSZ-13 powder.The diesel engine bench tests show that Cu,Mn co-exchange gives the monolith catalyst a better catalytic property than commercial catalysts.This work provides an important guidance for the rational design of secondary-ion-assisted zeolites applied in NH_(3)-SCR.展开更多
High-quality standard oil synthetic zeolite-13(SSZ-13) membranes with thickness only ~ 1.0 μm were prepared on tubular supports by the new seeded-gel approach. Seeded-gel approach is simpler than the normal secondary...High-quality standard oil synthetic zeolite-13(SSZ-13) membranes with thickness only ~ 1.0 μm were prepared on tubular supports by the new seeded-gel approach. Seeded-gel approach is simpler than the normal secondary-growth one since adding seeds in the gel is simpler than seeding on the support surface. The synthesis time was greatly reduced from 3.0 to 1.0 d after synthesis modification of gel aging and seed sizes. Low temperature ozone calcination was used for the removal of the organic structural directing agent. The best SSZ-13 membrane displayed CO_(2)permeances of 1.3 × 10^(-6) and 1.5 × 10^(-6) mol·m^(-2)·s^(-1)·Pa^(-1) and CO_(2)/CH_(4) and CO_(2)/N_(2) selectivities of 125 and 27 for equimolar CO_(2)/CH_(4) and CO_(2)/N2mixtures at 0.2 MPa pressure drop and 298 K, respectively. Separation performance of the membrane in the two binary mixtures is higher than that of most zeolite membranes. Three SSZ-13 membranes were reproducibly prepared on tubular supports by seeded-gel approach and the standard deviation ratios of CO_(2) permeance and CO_(2)/CH_(4) selectivity are 12.5% and 7%, respectively. It suggests that this new synthesis approach is creditable. The effects of temperature and pressure on separation performance of the thin SSZ-13 membranes were studied in the two binary mixtures. The tubular SSZ-13 membranes displayed great potentials for CO_(2) capture from natural gas, biogas and flue gas.展开更多
SSZ-13和SAPO-34是性能优异的甲醇制烯烃(methanol to olefins,MTO)催化剂。本文从酸性、积炭、烃池物种及其反应途径等方面介绍了SSZ-13和SAPO-34的酸强度和酸中心密度的差异及其对MTO反应催化性能的影响,综述了SSZ-13和SAPO-34在MTO...SSZ-13和SAPO-34是性能优异的甲醇制烯烃(methanol to olefins,MTO)催化剂。本文从酸性、积炭、烃池物种及其反应途径等方面介绍了SSZ-13和SAPO-34的酸强度和酸中心密度的差异及其对MTO反应催化性能的影响,综述了SSZ-13和SAPO-34在MTO中的催化反应机理和失活机理的研究进展。总结显示,尽管SSZ-13和SAPO-34都是CHA型拓扑结构,但SSZ-13的酸性强于SAPO-34,更有利于碳正离子的生成;与修边机理相比,侧链烷基化机理是更主要的反应途径,且SSZ-13的甲基化速率比SAPO-34高3个数量级;SSZ-13和SAPO-34的积炭速率和积炭物种存在差异,积炭行为受温度影响较大。从催化剂的角度,指出合理调控酸强度和酸中心密度、研制出能够抑制反应失活的催化剂结构、发展高产乙烯或者丙烯的特色MTO催化剂是以后的研究方向;从反应机理的角度,认为SSZ-13和SAPO-34在MTO反应中活性中间体的形成以及转化途径、活性物种到积炭物种的演变有待进一步研究。此外,如何在MTO反应过程中观察到高活性的反应中间体是今后研究的难点。展开更多
文摘The Cu-exchanged SSZ-13 with the small-pore chabazite framework is considered as a highly efficient catalyst for selective catalytic reduction of NO with NH_(3)(NH_(3)-SCR).In order to further improve the catalytic property,a series of Mn ion-assisted Cu/SSZ-13 powder catalysts were prepared by co-exchange method and stepwise exchange method.It is found that the NH_(3)-SCR activity,N_(2) selectivity,hydrothermal stability and sulfur resistance of Cu/SSZ-13 are promoted by introducing a minority of Mn(0.15%to 0.23%(mass))through co-exchange method.Characterization results reveal that the Cu,Mn co-exchange enables the higher amounts of Cu^(2+)active sites,the abundant medium strong and strong acid,the optimized ratio of Lewis acid to Brønsted acid etc.,which are required for a good NH_(3)-SCR catalytic property over broad temperature range and under harsh working environment.Moreover,a monolithic catalyst was prepared by impregnating a cordierite ceramic support into the coating slurry containing the optimized CuMn/SSZ-13 powder.The diesel engine bench tests show that Cu,Mn co-exchange gives the monolith catalyst a better catalytic property than commercial catalysts.This work provides an important guidance for the rational design of secondary-ion-assisted zeolites applied in NH_(3)-SCR.
基金Financial supports from the National Natural Science Foundation of China (21921006, 21938007 and 21576131)the open project of the State Key Laboratory of Materials-Oriented Chemical Engineering of China (KL21-04)。
文摘High-quality standard oil synthetic zeolite-13(SSZ-13) membranes with thickness only ~ 1.0 μm were prepared on tubular supports by the new seeded-gel approach. Seeded-gel approach is simpler than the normal secondary-growth one since adding seeds in the gel is simpler than seeding on the support surface. The synthesis time was greatly reduced from 3.0 to 1.0 d after synthesis modification of gel aging and seed sizes. Low temperature ozone calcination was used for the removal of the organic structural directing agent. The best SSZ-13 membrane displayed CO_(2)permeances of 1.3 × 10^(-6) and 1.5 × 10^(-6) mol·m^(-2)·s^(-1)·Pa^(-1) and CO_(2)/CH_(4) and CO_(2)/N_(2) selectivities of 125 and 27 for equimolar CO_(2)/CH_(4) and CO_(2)/N2mixtures at 0.2 MPa pressure drop and 298 K, respectively. Separation performance of the membrane in the two binary mixtures is higher than that of most zeolite membranes. Three SSZ-13 membranes were reproducibly prepared on tubular supports by seeded-gel approach and the standard deviation ratios of CO_(2) permeance and CO_(2)/CH_(4) selectivity are 12.5% and 7%, respectively. It suggests that this new synthesis approach is creditable. The effects of temperature and pressure on separation performance of the thin SSZ-13 membranes were studied in the two binary mixtures. The tubular SSZ-13 membranes displayed great potentials for CO_(2) capture from natural gas, biogas and flue gas.
文摘SSZ-13和SAPO-34是性能优异的甲醇制烯烃(methanol to olefins,MTO)催化剂。本文从酸性、积炭、烃池物种及其反应途径等方面介绍了SSZ-13和SAPO-34的酸强度和酸中心密度的差异及其对MTO反应催化性能的影响,综述了SSZ-13和SAPO-34在MTO中的催化反应机理和失活机理的研究进展。总结显示,尽管SSZ-13和SAPO-34都是CHA型拓扑结构,但SSZ-13的酸性强于SAPO-34,更有利于碳正离子的生成;与修边机理相比,侧链烷基化机理是更主要的反应途径,且SSZ-13的甲基化速率比SAPO-34高3个数量级;SSZ-13和SAPO-34的积炭速率和积炭物种存在差异,积炭行为受温度影响较大。从催化剂的角度,指出合理调控酸强度和酸中心密度、研制出能够抑制反应失活的催化剂结构、发展高产乙烯或者丙烯的特色MTO催化剂是以后的研究方向;从反应机理的角度,认为SSZ-13和SAPO-34在MTO反应中活性中间体的形成以及转化途径、活性物种到积炭物种的演变有待进一步研究。此外,如何在MTO反应过程中观察到高活性的反应中间体是今后研究的难点。
文摘以硅溶胶、硫酸铝、氢氧化钠、去离子水为原料,以N,N,N-三甲基金钢烷氢氧化铵为模板剂(R),用传统的水热法合成分子筛SSZ-13,对合成产物用XRD、SEM、FT-IR和BET进行表征,并通过改变原料的配比和反应条件确定它的最佳合成条件.实验结果表明:在反应温度为155℃、晶化时间为3 d时,其最佳合成氧化物的摩尔比范围:SiO2/A12O3为40,Na2O/A12O3为12～16,R2O/A12O3为3～5,H2O/A12O3为900～1 350.在最佳条件下合成的分子筛SSZ-13,大大缩短了反应时间,加晶种或促进剂时,晶化时间缩短为2 d.
