Modification and performance of Li induced silica phase transition of （Mn＋W）/SiO2 catalyst, under reaction conditions of oxidative coupling of methane （OCM）, have been investigated employing textural characteriza...Modification and performance of Li induced silica phase transition of （Mn＋W）/SiO2 catalyst, under reaction conditions of oxidative coupling of methane （OCM）, have been investigated employing textural characterizations and redox studies. Stability and precrystalline form of fresh Li induced silica phase transition catalyst depend on the Li loading. A catalyst, with high lithium loading, destabilizes on OCM stream. This destabilization is not due to Li evaporation at OCM reaction conditions, α-cristobalite is proposed to be an intermediate in the crystallization of amorphous silica into quartz in the Li-induced silica phase transition process. However, the type of crystalline structure was found to be unimportant with regard to the formation of a selective catalyst. Metal-metal interactions of Li-Mn, Li-W and Mn-W, which are affected during silica phase crystallization, are found to be critical parameters of the trimetallic catalyst and were studied by TPR. Role of lithium in Li doped （Mn＋W）/SiO2 catalyst is described as a moderator of the Mn-W interaction by involving W in silica phase transition. These interactions help in the improvement of transition metal redox properties, especially that of Mn, in favor of OCM selectivity.展开更多
Because of the ever-increasing consumption of crude oil, the role played bythe natural gas as a raw material has become more and more important in chemical industry and thepotential of methane used as a source for the...Because of the ever-increasing consumption of crude oil, the role played bythe natural gas as a raw material has become more and more important in chemical industry and thepotential of methane used as a source for the production of ethylene has attracted much attention.In this paper, the LiCl-B_2O_3/MnO_2 and Li_2SO_4-Mn_xO_y/TiO_2 catalysts for Oxidative Coupling ofMethane (OCM) have been studied, and the results show that the catalysts exhibit high activity andselectivity. Furthermore, The influence of the components in the catalyst and the reactionconditions on OCM performance has been studied and a possible active new component, cubicLi_4B_7O_(12)Cl, has been found.展开更多
he deactivation of highly active multicomponent oxide LiLa_0.5 Ti_0.5 O_(2+λ) cata-lyst at high reaction temperatures has been studied. The surface and bulk structureof the catalyst were characterized by means of XRD...he deactivation of highly active multicomponent oxide LiLa_0.5 Ti_0.5 O_(2+λ) cata-lyst at high reaction temperatures has been studied. The surface and bulk structureof the catalyst were characterized by means of XRD, IR, XPS, BET, O_2-TPD,SEM etc.. The results show that the deactivation of the catalyst at high reactiontemperatures is mainly due to the loss of surface lithium. As a result , the diffusionof lithium from bulk to surface leads to the decompositiqn of the active phase con-taining lithium, which lowers tlie number of oxygen vacancies and decreases themobility of lattice oxygen.展开更多
文摘Modification and performance of Li induced silica phase transition of （Mn＋W）/SiO2 catalyst, under reaction conditions of oxidative coupling of methane （OCM）, have been investigated employing textural characterizations and redox studies. Stability and precrystalline form of fresh Li induced silica phase transition catalyst depend on the Li loading. A catalyst, with high lithium loading, destabilizes on OCM stream. This destabilization is not due to Li evaporation at OCM reaction conditions, α-cristobalite is proposed to be an intermediate in the crystallization of amorphous silica into quartz in the Li-induced silica phase transition process. However, the type of crystalline structure was found to be unimportant with regard to the formation of a selective catalyst. Metal-metal interactions of Li-Mn, Li-W and Mn-W, which are affected during silica phase crystallization, are found to be critical parameters of the trimetallic catalyst and were studied by TPR. Role of lithium in Li doped （Mn＋W）/SiO2 catalyst is described as a moderator of the Mn-W interaction by involving W in silica phase transition. These interactions help in the improvement of transition metal redox properties, especially that of Mn, in favor of OCM selectivity.
基金Project supported by the Foundation of Shanghai Science and Technology Development(No.023012007)
文摘Because of the ever-increasing consumption of crude oil, the role played bythe natural gas as a raw material has become more and more important in chemical industry and thepotential of methane used as a source for the production of ethylene has attracted much attention.In this paper, the LiCl-B_2O_3/MnO_2 and Li_2SO_4-Mn_xO_y/TiO_2 catalysts for Oxidative Coupling ofMethane (OCM) have been studied, and the results show that the catalysts exhibit high activity andselectivity. Furthermore, The influence of the components in the catalyst and the reactionconditions on OCM performance has been studied and a possible active new component, cubicLi_4B_7O_(12)Cl, has been found.
文摘he deactivation of highly active multicomponent oxide LiLa_0.5 Ti_0.5 O_(2+λ) cata-lyst at high reaction temperatures has been studied. The surface and bulk structureof the catalyst were characterized by means of XRD, IR, XPS, BET, O_2-TPD,SEM etc.. The results show that the deactivation of the catalyst at high reactiontemperatures is mainly due to the loss of surface lithium. As a result , the diffusionof lithium from bulk to surface leads to the decompositiqn of the active phase con-taining lithium, which lowers tlie number of oxygen vacancies and decreases themobility of lattice oxygen.
