Conversion Of Syngas To Higher Alcohols Over CuCo Catalysts Derived From Pervoskite

Owing to the energy structural characteristics of "rich coal,poor oil and little gas" in our country and the potential applications of higher alcohols in fuel,fuel additives and chemicals,higher alcohols synthesis from coal or biomass via syngas has important strategic significance and potential applications prospect.In this paper,based on the diversity of the composition of the perovskite-type-oxides,we have doped some different metal ions into the B sites of perovskite and prepared a series of LaCo_0.7Cu_0.3O₃/SiO₂,Co₃O₄/LaFe_0.7Cu_0.3O₃ and LaCo_0.7Cu_0.3O₃/ZrO₂ catalyst precursors using the citrate complexation method.By reducing the meso-macroporous SiO₂ supported LaCo_0.7Cu_0.3O₃ catalyst precursors under different conditions,bimetallic nanoparticles with core-shell structure supported on SiO₂-La₂O₃ were made,and the structure of the nano bimetal could be adjusted via controlling the reduction conditions.The obtained bimetallic catalysts were used for higher alcohols synthesis,and the relationship between the structure and catalytic performance was found.The supported bimetal with cobalt as the core and copper as the shell favored the alcohols synthesis but was not active enough;the bimetal with copper as the core and cobalt as the shell exhibited lower selectivity to alcohols but was more active.Mesoporous LaFe_0.7Cu_0.3O₃ perovskite was prepared by a simple nanocasting method,the prepared mesoporous perovskite has a high surface area.Furthermore,mesoporous LaFe_0.7Cu_0.3O₃ supported Co₃O₄ was prepared by using the impregnation method.During reduction,the structure of Co₃O₄/La Fe0.7Cu0.3O3 was transferred to CuCo/La₂O₃-LaFeO₃,in which Co-Cu was in state of solid solution alloy.The catalysts of Cu-Co/La₂O₃-LaFeO₃ was used for higher alcohols synthesis and showed good activity,high selectivity to alcohols and relatively good stability.The good activity and high selectivity to alcohols on Cu-Co/La₂O₃-LaFeO₃ was attributed to the very high surface area of the support and the formation of Co-Cu alloy.Simultaneously,the good antisintering ability and maintained mesoporous structure of the catalyst contributed to the relatively good stability.The stability in long run and the deactivation of LaCo_0.7Cu_0.3O₃/ZrO₂ has been investigated.The results showed that LaCo_0.7Cu_0.3O₃/ZrO₂ tends to generate nanoparticles of Co-Cu alloy supported on La₂O₃ doped ZrO₂ during reduction.When the Co-Cu alloy contacted with syngas,part of the Co-Cu alloy would decompose into Cu and Co₂C.Along with the reaction,the catalyst became relatively stable and was transformed to a mixture of Cu,Co₂C,（Cu-Co alloy）@ Co₂C,which were supported on La₂O₃-doped ZrO₂.During reaction,no sintering of the active nanoparticles in the catalyst and the support could be observed,and the amount of coke deposition on the catalyst surface was also small,meaning that the sintering and coke deposition were not responsible for the deactivation of the Co-Cu/La₂O₃-ZrO₂ catalyst.In the reaction period of 200-1500 h,the deactivation of the Cu-Co/La₂O₃-doped ZrO₂ catalyst is mainly attributed to cobalt volatilization in the form of its carbonyl at the reaction temperature,which resulted in the decrease of CO conversion.The analysis of the deactivation of Cu-Co/ZrO₂ would provide some guidance for the design of Cu-Co based catalysts and other bimetallic nanocatalysts.