Research Of Co/AC Catalysts For Higher Alcohols Synthesis From Syngas

It is now attracting more and more attention for higher alcohols synthesis from syngas based on coal and natural gas due to the energy saving and environmentally friendly properties.Cobalt-based catalyst has advantages such as cost,tolerance to poisoning and product processing.However,it still exists many drawbacks,such as low catalytic activity,low selectivity to higher alcohol.Therefore,in this study,Co/AC catalysts were explored for higher alcohol synthesis.The influence of cobalt loading,promoters,acid treatment of carrier and preparation methods on the physico-chemical and catalytic properties of the Co/AC catalysts for higher alcohol synthesis has been investigated.Activated carbon and catalysts were characterized by Hz program-temperature-reduction(H2-TPR),CO chemical adsorption,N2 physical adsorption.(BET)and X-ray diffraction(XRD).The effect of catalyst composition,promoters and preparation methods on the physical structure,reducing property,Co dispersion and the phase were also studied.Firstly,the effects of the cobalt loading and promoters(La,Zr)on the performance of the catalysts were disclosed.The result shows that the performance in synthesis of higher alcohol is better when the loading of Co,Zr,La is 15%and 1.0%,0.5%respectively than others.Secondly,with the above optimal catalyst composition,the influence of the treatment with different concentrations of nitric acid and citric acid separately on the catalytic performance of the Co-Zr-La/AC catalyst was investigated.The results show that treatment of support can improve the CO conversion level significantly,and the selectivity to higher alcohol is also increased following the treatment with nitric acid or citric acid After treatment with appropriate concentration of acid,the catalysts display high CO conversion and selectivity to the higher alcohols.For example,catalyst with its support treated by 4.6mol/L nitric acid,CO conversion increases from 9.9%to 44.8%,and the ratio of high alcohols to total alcohols jumps from 12.6%to 40.3%..Following the treatment by 2.0mol/L citric acid,the CO conversion increases to 61.0%,and the ratio of high alcohols to total alcohols reaches 29.2%.Finally,in addition to the acid treatment,the impregnation solvent and impregnation sequence were studied.The results show that catalyst prepared by the impregnation sequence of promoters followed by Co can improve conversion of CO and the selectivity to higher alcohols;while the catalysts display higher CO conversion and selectivity to higher alcohol after impregnation with ethanol.