Study On Preparation And Performance Of Novel Cobalt-based Fischer-tropsch Catalysts Derived From Ldh

Fischer-Tropsch Synthesis（FTS）is a catalytic chemical reaction that transforms syngas（mixture of CO and H₂）from biomass,coal or natural gas into ultra-clean fuels or value-added chemicals.However,the conventional catalysts used in the FTS process may easily deactivate due to sintering,surface phase change or oxidation,resulting in the shortened service life.Layered double hydroxide（LDHs,also known as hydrotalcites）with adjustable metal ion composition,uniform dispersion and high specific surface area characteristics can be used as a catalyst precursor containing high metal loading of Co.The calcination of the precursor material can be topologically transformed into a layered bimetallic oxide（LDO）and applied to the FTS reaction.In this paper,the precursor of LDHs was prepared by urea hydrolysis,introducing different metals（Zn,Al,Mg and Ni）with Co into LDHs,to prepare catalysts with high dispersion,suitable pore structure and good catalytic performance.XRD,BET,SEM and H₂-TPR were used to characterize the CXL-600 catalyst,and its catalytic performance was evaluated in a fixed-bed reactor.The results showed that high crystallinity was observed for the prepared precursor,and the CAL-600 catalyst after calcination showed a specific surface area of 271 m²·g^-1,CO conversion of 22.0%and the C₅₊selectivity of 91.6%.Due to the superior properties in dispersion,specific surface area and pore volume,which favor the absorption and surface reaction of syngas in the catalyst pore,CAL-600 was selected as the precursor for the Co based FT catalyst in this study.As it is generally believed that size of Co crystalline in the catalyst and the reducibility of catalyst plays important role in the FTS reaction,CAL was used as the catalyst precursor,which was calcined in N₂ at 500-800℃to obtain high dispersion and high active Co metal loading（>51 wt.%）in LDHs derived catalyst.The results show that Co crystalline size and reducibility grows with increasing calcination temperature,but high calcination temperature can cause physical collops of the LDH structure.Both surface area and pore volume show a maxima as calcination temperature increases.The CAL-800 catalyst prepared at a calcination temperature of800℃yields a maximum CO conversion rate up to 25.4%,and the C₅₊selectivity up to 79.4%.The results obtained from this study can help in our further investigation of LDHs as potential high efficient catalyst for FTS.