The catalytic decomposition of NO over Ag-ZSM-5 catalyst prepared by ion-exchange was investigated. The exchanged silver in the zeolite was reduced and it collected in the course of the reaction to form silver particl...The catalytic decomposition of NO over Ag-ZSM-5 catalyst prepared by ion-exchange was investigated. The exchanged silver in the zeolite was reduced and it collected in the course of the reaction to form silver particles of about 20 nm. The catalytic reaction induced a pronounced restructuring of the Ag particles through preferential formation of the (111) facets. These facets were shown to hind a tightly bound oxygen species (O-gamma). The O-gamma species occupies the active sites for NO adsorption resulting in catalyst deactivation. It could be removed by appropriate reducing agents, such as CO, to recover the active sites at elevated temperatures.展开更多
以I2为修饰剂,采用等体积浸渍法成功改性制备了I-Ag/ZSM-5催化剂,考察了不同Ag负载量对催化剂物化性质和MTO反应催化性能的影响。采用XRD、NH3-TPD、XRF等手段对不同Ag负载量I-Ag/ZSM-5催化剂微观结构、表面酸性质及反应前后元素组成等...以I2为修饰剂,采用等体积浸渍法成功改性制备了I-Ag/ZSM-5催化剂,考察了不同Ag负载量对催化剂物化性质和MTO反应催化性能的影响。采用XRD、NH3-TPD、XRF等手段对不同Ag负载量I-Ag/ZSM-5催化剂微观结构、表面酸性质及反应前后元素组成等进行分析表征。结果表明,I负载量9%时,不同Ag负载量对I-Ag/ZSM-5催化剂物化性质和MTO反应催化性能影响较大;Ag负载量9%时,Ag与I形成适宜化学吸附,提高了催化剂稳定性,产生了部分较弱中强酸;在常压、反应温度330℃、氮气流速20 m L/min、进料空速为2.4 h-1反应条件下,9%I-9%Ag/ZSM-5催化剂表现出良好催化性能,甲醇转化率和低碳烯烃选择性分别达90.13%和87.44%。展开更多
ZSM-5 zeolite microparticles(MPs)were synthesized under hydrothermal condition using a low crystal seed addition approach without template.The synthesis parameters such as the seed addition amount,the SiO2/Al2O3ratio,...ZSM-5 zeolite microparticles(MPs)were synthesized under hydrothermal condition using a low crystal seed addition approach without template.The synthesis parameters such as the seed addition amount,the SiO2/Al2O3ratio,the aluminum source,the feeding addition method,aging,and crystallization were investigated.The structure,morphology and composition of the as-synthesized ZSM-5 zeolite MPs were characterized by X-ray powder diffraction(XRD),scanning electron microscopy(SEM),laser particle size distribution(PSD)measurements,and inductively coupled plasma-atomic emission spectrometry(ICP-AES).The SiO2/Al2O3ratio of ZSM-5 zeolite MPs was in the range of 20—80.The low seed addition was beneficial to improving the crystallinity and shortening the crystallization time,and the suitable amount of seed was 0.25%(SiO2).The ZSM-5 zeolite MPs synthesized with aluminium nitrate nonahydrate used as the aluminum source exhibited a relatively high crystallinity.An appropriate aging time could eliminate the effect of feeding addition method and effectively adjust particle size.The particle size of ZSM-5 zeolite obtained at an aging time of 20 h was around 2.0μm.Prolonging the aging time appropriately could also shorten the high-temperature crystallization time.The suitable aging time was 24 h,and the relative crystallinity of ZSM-5 zeolite could reach up to 99%after crystallization for 24 h at 180℃.展开更多
文摘The catalytic decomposition of NO over Ag-ZSM-5 catalyst prepared by ion-exchange was investigated. The exchanged silver in the zeolite was reduced and it collected in the course of the reaction to form silver particles of about 20 nm. The catalytic reaction induced a pronounced restructuring of the Ag particles through preferential formation of the (111) facets. These facets were shown to hind a tightly bound oxygen species (O-gamma). The O-gamma species occupies the active sites for NO adsorption resulting in catalyst deactivation. It could be removed by appropriate reducing agents, such as CO, to recover the active sites at elevated temperatures.
文摘以I2为修饰剂,采用等体积浸渍法成功改性制备了I-Ag/ZSM-5催化剂,考察了不同Ag负载量对催化剂物化性质和MTO反应催化性能的影响。采用XRD、NH3-TPD、XRF等手段对不同Ag负载量I-Ag/ZSM-5催化剂微观结构、表面酸性质及反应前后元素组成等进行分析表征。结果表明,I负载量9%时,不同Ag负载量对I-Ag/ZSM-5催化剂物化性质和MTO反应催化性能影响较大;Ag负载量9%时,Ag与I形成适宜化学吸附,提高了催化剂稳定性,产生了部分较弱中强酸;在常压、反应温度330℃、氮气流速20 m L/min、进料空速为2.4 h-1反应条件下,9%I-9%Ag/ZSM-5催化剂表现出良好催化性能,甲醇转化率和低碳烯烃选择性分别达90.13%和87.44%。
基金Financial support from the Innovation Fund for Elitists of Henan Province,China(No.0221001200)the Talent Training Joint Fund of NSFC-Henan(No.U1204203)the China Postdoctoral Science Foundation(No.2012M511121)
文摘ZSM-5 zeolite microparticles(MPs)were synthesized under hydrothermal condition using a low crystal seed addition approach without template.The synthesis parameters such as the seed addition amount,the SiO2/Al2O3ratio,the aluminum source,the feeding addition method,aging,and crystallization were investigated.The structure,morphology and composition of the as-synthesized ZSM-5 zeolite MPs were characterized by X-ray powder diffraction(XRD),scanning electron microscopy(SEM),laser particle size distribution(PSD)measurements,and inductively coupled plasma-atomic emission spectrometry(ICP-AES).The SiO2/Al2O3ratio of ZSM-5 zeolite MPs was in the range of 20—80.The low seed addition was beneficial to improving the crystallinity and shortening the crystallization time,and the suitable amount of seed was 0.25%(SiO2).The ZSM-5 zeolite MPs synthesized with aluminium nitrate nonahydrate used as the aluminum source exhibited a relatively high crystallinity.An appropriate aging time could eliminate the effect of feeding addition method and effectively adjust particle size.The particle size of ZSM-5 zeolite obtained at an aging time of 20 h was around 2.0μm.Prolonging the aging time appropriately could also shorten the high-temperature crystallization time.The suitable aging time was 24 h,and the relative crystallinity of ZSM-5 zeolite could reach up to 99%after crystallization for 24 h at 180℃.
