Study On Rh Catalysts For Ethanol Synthesis From Syngas

Ethanol synthesis form syngas can satisfy the potential demand for fuel ethanol and sufficiently utilize plenty coal resource in China.Rh-based catalyst is one of the most potential catalysts for the direct conversion of syngas to ethanol.This paper investigated the effect of single promoter,dual promoters,and different supports on the catalytic performance,and improved the behaviors of catalysts by adding proper promoter loading and choosing appropriate support.Rh-Fe/y-Al2O3 catalysts for the synthesis of ethanol from syngas were prepared by incipient wetness impregnation.The effect of Fe loadings on Rh-based catalysts was explored by means of XRD,N2 adsorption,H2-TPR and CO-TPD.H2-TPR results showed that the introduction of Fe led to the hindered reducibility of Rh oxide species.CO-TPD experiments indicated that Fe could promote the CO non-dissociation adsorption but suppress the CO dissociation adsorption.Catalytic performance showed that CO conversion was improved by the addition of Fe promoter.The catalyst with 4 wt%Fe exhibited the highest selectivity to ethanol.Rh-based catalysts on different supports were prepared by incipient wetness impregnation.The effect of γ-Al2O3,TiO2,Ce0.8Zr0.2O2,Silicalite-1 and Fe-MFI supports was explored by means of N2 adsorption,XRD,CO-TPD,NH3-TPD and Uv-vis,and the performance of these catalysts in CO hydrogenation was investigated.Results showed that the channel and acidity of supports could affect the production of ethanol.Compared with catalysts supported on zeolite,catalysts supported on metal oxides had high ethanol selectivity due to their mesopore channel and proper acidity.The influence of Li loading on the activity and selectivity of Rh-Fe/γ-Al2O3 catalysts for the synthesis of ethanol from syngas was explored.Rh-Fe-Li/y-Al2O3 catalysts were prepared by incipient wetness impregnation.The catalysts were characterized by means of XRD,N2 adsorption,TPR,XPS,CO-TPD,and DRIFTS.Results from H2-TPR and XPS showed that the introduction of Li led to the hindered reducibility of Rh oxide species,which caused Rh+content increase on reduced Li promoted catalysts.Furthermore,CO-TPD and DRIFTS experiments proved that the incorporation of Li to Fe promoted Rh catalysts facilitated the generation of CO(gdc)and strengthened the stabilization of CO(gdc)species on Rh+ sites which are beneficial to CO insertion,and at the same time impeded the formation of CO(1)and CO(b)species on Rh0 sites which are responsible for CO dissociation.Catalytic results showed that under the condition of 260℃、2MPa and 3600mL·g-1·h-1,lower hydrocarbons selectivity and higher ethanol selectivity were observed on Li modified Rh-Fe catalysts.The catalyst with 0.5 wt%Li exhibited the highest ethanol selectivity being 30.2%.