Study On The Catalyst For Isobutanol Synthesis From Syngas

Mixed alcohols can be used as not only fuels, but also raw materials of fine chemical, organic solvents et al. As a part of the coal chemical industry, the development of syngas chemical has a significant effect on the applications for clean coal resources. Both methanol modified and Fischer-Tropsch modified catalysts, prepared by co-precipitation or impregnation or combination of the two methods, are studied for the synthesis of isobutanol from syngas, and characterized by BET, H2-TPR, CO-TPD, CO2-TPD and XRD for assessment of the impact of support and additives on the structure and morphology of catalysts.After screening, Cu is determined as the active component. Result indicates basic support MgO is more advantageous for isobutanol synthesis than supports Al2O3, ZrO2 and SiO2, and the appropriate molar ratio of Cu/MgO is 1. For Cu/MgO catalyst, the ability of carbon chain growth and space time yield of C2+OH increase with the addition of Zn. The introduction of Zn in Cu/MgO increases the specific surface area of catalysts and the dispersion of Cu, Mg species, and also increases the number and intensity of basic site. Under the condition of Zn/Cu=0.25, the mass fraction of isobutanol in total alcohol increases from 1.54% to 2.24% after Zn is added in Cu/MgO catalyst.For Cu/Zn/MgO catalyst, the addition of K decreases the activity of catalyst and the content of C2+OH in total alcohol while Pd increases the selectivity of alcohol but decreases the mount of CO2 in outlet. The ability of carbon chain growth decreases due to the strong hydrogenation ability of Pd. Process optimization on Cu/Zn/MgO shows that the higher temperature favours higher alcohol synthesis, but increases the possibility of the coke formation coating on catalysts, which decreases the number of active site. A higher partial pressure of CO as well as longer residence times benefits the formation of higher alcohol. For Fe modified Cu/Zn/MgO catalyst, prepared by co-precipitation-impregnation method, evaluation results reveal that MgFe2O4 phase is formed, which promotes the dispersion of both the Fe and Mg species when Fe is added. The optimal amount of Fe promotes the adsorption intensity of CO and facilitates the synthesis of C2+alcohols. Compared with catalyst without Fe, the mass fraction of C2+alcohols in total alcohol and space time yields of C2+ alcohols increased from 19.6% to 59.7% and 23.3 g/(kgcat·h) to 45.3 g/(kgcat·h) respectively when the molar ratio of Fe is n(Fe)/n(Cu)=0.15.