The Stability Of CoGa Catalysts Based On Layered Double Hydroxides In Syngas Conversion

Supported metal are widely used in petrochemical,fine chemical,coal chemical and biomass conversion and utilization.It is an great challenge for supported metal catalysts inactivation due to sintering.Therefore,the development of supported metal catalysts with high stability is important for heterogeneous catalysis.The previous work from our group reported a uniformly dispersed CoGa catalyst with CoGa particles trapped in the oxide support,which is not only highly active and selective but also distinctively stable in the synthesis of C2+alcohols from syngas.Based on the topological transformation effect of layered double hydroxides(LDHs)and the adjustable metal ratio of LDHs layer,this paper further researchs the reduction conditions of trapped structure and explores the important factors to improve the stability of CoGa catalysts.The main research contents and conclusions are as follows:1.Through tailoring the reduction temperature,heating rate,or retention time to investigate the reduction conditions of trapped structure.●Through tailoring the reduction temperature was 550℃,600℃,700℃,750℃,and 800 0C(5℃/min,hold 0 h),it was found that when the reduction temperature was 600℃,700 0C and 750 0C,Co or CoGa particles with trapped structure could be formed,and when the reduction temperature was 550℃ or 800℃,Co and CoGa particles without trapped structure could be formed respectively.●Through tailoring the heating rate was 1℃/min,5℃/min and 10℃/min(700℃,hold 0 h),it was found that CoGa particles with trapped structure could be formed when the heating rate was 1℃/min and 5℃/min,CoGa particles without trapped structure could be formed when the heating rate was 10℃/min.●Through tailoring the retention time to 2 h of the topological transformation process,it was found that the supported Co particles with trapped structure could be formed at 600℃ for 0 h,and the supported Co particles with no trapped structure were formed for 2 h.Except 600℃,the reduction temperature and heating rate were adjusted under the retention time of 2 h,compare to retention time of 0 h,the formation conditions of trapped structure were consistent with the retention time of 0 h.In syngas conversion reaction,CoGa particles with trapped structure have good stability.while CoGa particles without trapped structure and Co particles with trapped structure have poor stability.The trapped structure can stabilize CoGa particles,but not stabilize Co particles effectively.2.By adjusting the Ga/Co,no trapped structure for Co particles were observed when Ga/Co ratio is 0,trapped structure for CoGa particles were observed when Ga/Co ratio is 0.2 and 0.5,and no trapped structure for CoGa particles were observed when Ga/Co ratio is 1.0,2.4 and 8.0.In syngas conversion,CoGa particles with trapped structure have good stability.CoGa particles without trapped structure,such as Ga/Co=2.4 and 8.0,also have good stability.There is a large amount of Ga0 on the surface of samples with Ga/Co=2.4 and 8.0,Ga0 can promote the stability of CoGa particles.With the increase of Ga0/Co0 ratio,the selectivity of C2+alcohol in the products increased,while that of alkane decreased.