Study Of Hydrotalcite Load Cu-Co-Rh Catalyst For Ethanol Synthesis From Syngas

Ethanol is not only an important industrial chemical but also a new clean energy.Coal-based synthesis gas catalytic conversion method has attracted most attention among all the approaches to prepare and produce ethanol.In this method,many researches have studied two types of catalysts,namely the precious metal Rh-based catalyst and Cu-Co based catalyst,and both of them have incompatible problem of their catalyst activity with the selectivity of ethanol.However,the two types of catalysts have different advantages and disadvantages from each other.This paper aims to study the two catalysts and use XRD,SEM,BET,H2-TPR,XPS,CO-TPD and TEM to characterize the catalysts.Hydrothermal synthesis method and solvothermal method are used to prepare and produce hydrotalcite in different Mg-Al ratios,urea concentrations and CTAB addition levels to investigate the effects of Mg-Al ratio,urea concentration and CTAB addition levels of hydrotalcite on properties of catalyst loaded with RhCuCo.The results showed that with the increase of Mg-Al ratio,the selectivity of hydrocarbons improved and the selectivity of alcohols decreased.As the urea concentration grows,the selectivity of hydrocarbons declined and then increased,the selectivity of methanol grew,the selectivity of ethanol increased and then fell.With the increasing addition level of CTAB,the selectivity of hydrocarbons increased greatly,and the selectivity of alcohols fell dramatically.When Mg-Al ratio reaches 2:1 and urea concentration Al ion ratio approaches 5:1,the property of hydrotalcite is the best.Incipient wetness impregnation is used to prepare and produce the RhCuCo/LDHs catalyst in different Cu-Co ratios and different loads of K to investigate the effect of Cu-Co ratio and K load on properties of the catalyst.It is found in the result that the increase of Cu-Co ratio is beneficial to improve the selectivity of ethanol,and is harmful to the rise of Co conversion rate and generation of hydrocarbons.The certain addition of K is beneficial to improve the selectivity of ethanol,while the excessive addition of K is more helpful to the production of methanol.When the Cu-Co ratio reaches 2:1,and K load is 1%,the catalyst has the highest selectivity of ethanol.Incipient wetness impregnation is applied to prepare RhCuCoK/LDHs catalyst with different loads of Rh,and investigate the influence of different loads of Rh on property of the catalyst.The results demonstrated that Rh load exerted a significant effect on textural properties of the catalyst.A certain load of Rh improved dispersion of Cu and Co,and agglomeration process would appear with an excessive load of Rh.A certain amount of Rh restrained reduction of Cu,and strengthened interaction between Rh and Cu,while an excessive amount of Rh would weaken the interaction between Rh and Cu.A certain amount of Rh addition could improve Cu content on the surface of the catalyst,and increase non-dissociative adsorption of CO concentration on the surface of the catalyst.Evaluation results of the catalyst property shows that in the reaction condition of 230?,2MPa,8000mL/?g.h?,H2/CO=1:1,and 2%Rh load,CO conversion rate is 54.49%,selectivity of ethanol is 25.03%.Incipient wetness impregnation with addition of Carbon Nano powder is applied to prepare and produce RhCuCoK/LDHs catalyst in different levels of Carbon Nano powder addition to investigate the effects of different addition and content of Carbon Nano powder on properties of the catalysts.The results presented that the addition of Carbon Nano powder promoted the generation of Cu-CO alloy,and a certain amount of Carbon Nano powder addition is helpful to improve the dispersion of metals.It promoted the reduction of Rh,allowed more Rh³⁺to reduce for Rh⁺with Rh⁰ species,increased the content of Rh⁺with Rh⁰.It stabilized the non-dissociated adsorption and dissociation adsorption species of CO on the catalyst,and increased the concentration of the two on the catalyst surface.It also reduced the size of active metal particles and improved the dispersion degree of the metal.Catalyst property evaluation results states that in reaction condition of 230?,2mpa,8000 ml/?g.h?,H2/CO=1:1,5%Carbon Nano powder addition,CO conversion rate is as high as 58.28%,the selectivity of ethanol ups to 27.27%.By comparing effects of different loads of Rh on properties of Carbon Nano powder catalyst,the research result indicated that when Rh load is 1%,the selectivity of ethanol was the highest.Compared with results of the catalyst without Carbon Nano powder,the addition of Carbon Nano powder is effective in reducing loads of precious metals.