The AEI cavity of SAPO-18 catalyst was modified with zinc cations with the conventional ion exchange procedure.The cavity modification effectively tunes the product selectivity,and shifts the products from mainly prop...The AEI cavity of SAPO-18 catalyst was modified with zinc cations with the conventional ion exchange procedure.The cavity modification effectively tunes the product selectivity,and shifts the products from mainly propylene to comparable production of ethylene and propylene in methanol to olefin(MTO)reaction.The incorporation of zinc ions and the generation of bicyclic aromatic species in the AEI cavity of SAPO-18 catalysts introduce additional diffusion hindrance that exert greater influence on the relatively bulky products(e.g.propylene and higher olefins),which increase the selectivity to small-sized products(e.g.ethylene).It appears that the incorporated zinc cations facilitate the generation of lower methylbenzenes which promote the generation of ethylene.The cavity modification via incorporating zinc ions effectively tunes the product selectivity over SAPO molecular sieves with relatively larger cavity,which provides a novel strategy to develop the potential alternative to SAPO-34 catalysts for industrial MTO reaction.展开更多
Halo-olefinic impurities in 1,1,1,3,3-pentafluoropropane （HFC-245fa） product used as blowing agents, etc. could damage the human body and must be removed. Activated carbon was treated by HCI, HN03 and NaOH, respecti...Halo-olefinic impurities in 1,1,1,3,3-pentafluoropropane （HFC-245fa） product used as blowing agents, etc. could damage the human body and must be removed. Activated carbon was treated by HCI, HN03 and NaOH, respectively. The adsorptive performance of unmodified and modified activated carbons for the removal of a low con- tent of l-chloro-3,3,3-trifluoro-l-propene （HCFC-1233zd）, 1,3,3,3-tetrafluoro-l-propene （HFC-1234ze）, 1- chloro-l,3,3,3-tetrafluoro-l-propene （HFC-1224zb） and 2-chloro-l,3,3,3-tetrafluoro-l-propene （HFC-1224xe） halo-olefins in the 1,1,1,3,3-pentafluoropropane （HFC-245fa] product was investigated. These halo-olefinic im- purities could be substantially removed from the HFC-245fa product via the adsorption over activated carbon when the adsorption temperature was under 333 K, which can be attributed to the n-n dispersion interactions between the halo-olefins and carbon graphite layer. The basic surface groups of activated carbon could catalyze the decomposition of HFC-245fa to form HFC-1234ze. However, the significant increase in the amount of surface acidic groups of activated carbon led to a distinct decrease of adsorption capacity due to the reduction in the mi- cropore volume of adsorbent and a decrease in the strength of the n-n dispersive interactions between halo- olefin molecules and carbon basal. The breakthrough time of halo-olefinic impurities on activated carbon in- creased with the increase of molecular mass and the decrease of molecular symmetry.展开更多
基金supported by the Key Research Program of Frontier Sciences,CAS(QYZDY-SSW-JSC024)the Youth Innovation Promotion Association of the CAS(2014165)the National Natural Science Foundation of China(21603223,21473182,91334205,91545104)~~
文摘The AEI cavity of SAPO-18 catalyst was modified with zinc cations with the conventional ion exchange procedure.The cavity modification effectively tunes the product selectivity,and shifts the products from mainly propylene to comparable production of ethylene and propylene in methanol to olefin(MTO)reaction.The incorporation of zinc ions and the generation of bicyclic aromatic species in the AEI cavity of SAPO-18 catalysts introduce additional diffusion hindrance that exert greater influence on the relatively bulky products(e.g.propylene and higher olefins),which increase the selectivity to small-sized products(e.g.ethylene).It appears that the incorporated zinc cations facilitate the generation of lower methylbenzenes which promote the generation of ethylene.The cavity modification via incorporating zinc ions effectively tunes the product selectivity over SAPO molecular sieves with relatively larger cavity,which provides a novel strategy to develop the potential alternative to SAPO-34 catalysts for industrial MTO reaction.
基金Supported by the Major Project of Green Chemical Industry of Zhejiang Province(2007C11043)
文摘Halo-olefinic impurities in 1,1,1,3,3-pentafluoropropane （HFC-245fa） product used as blowing agents, etc. could damage the human body and must be removed. Activated carbon was treated by HCI, HN03 and NaOH, respectively. The adsorptive performance of unmodified and modified activated carbons for the removal of a low con- tent of l-chloro-3,3,3-trifluoro-l-propene （HCFC-1233zd）, 1,3,3,3-tetrafluoro-l-propene （HFC-1234ze）, 1- chloro-l,3,3,3-tetrafluoro-l-propene （HFC-1224zb） and 2-chloro-l,3,3,3-tetrafluoro-l-propene （HFC-1224xe） halo-olefins in the 1,1,1,3,3-pentafluoropropane （HFC-245fa] product was investigated. These halo-olefinic im- purities could be substantially removed from the HFC-245fa product via the adsorption over activated carbon when the adsorption temperature was under 333 K, which can be attributed to the n-n dispersion interactions between the halo-olefins and carbon graphite layer. The basic surface groups of activated carbon could catalyze the decomposition of HFC-245fa to form HFC-1234ze. However, the significant increase in the amount of surface acidic groups of activated carbon led to a distinct decrease of adsorption capacity due to the reduction in the mi- cropore volume of adsorbent and a decrease in the strength of the n-n dispersive interactions between halo- olefin molecules and carbon basal. The breakthrough time of halo-olefinic impurities on activated carbon in- creased with the increase of molecular mass and the decrease of molecular symmetry.
