Study On Preparation And Performance Of Cu-Co Based Catalytsts Supported On Mixed Carriers

In this thesis, synthesis of lower carbon mixed alcohols from syngas over Cu-Co catalytsts with mixed carriers was studied.The influence of the preparation technology of carrier, the Cu/Co molar ratio, the mixture ratio of ZSM-5/Al2O3 and the Si/Al ratio of ZSM-5 on structure and properties of the catalysts was studied. The catalysts were characterized by Ar physics-stripping in low temperature, H2-temperature programmed reduction (H2-TPR), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscope (TEM) and CO-temperature programmed desorption (CO-TPD).The kinetics of Cu-Co/ZSM-5/Al2O3 was studied,and the process parameters of reaction conditions was optimized. The results were listed as follows:(1) With the increase of Cu content in the catalyst, the CO conversion and the selectivity of C2+ alcohol increased firstly and then decreased. The the optimal Cu/Co molar ratio was 0.4. On which the CO conversion reached 16.47%, and the selectivity of C2+ alcohols reached 34.25%.(2) The study of mixed methods exhibited that the activity of Cu-Co/ZSM-5/Al2O3 is the best, and it superior to the single carrier catalyst, Cu-Co/ZSM-5/SiO2 and ZSM-5@ Cu-Co/Al2O3 core-shell catalyst.(3)The mixture ratio of support on Cu-Co/ZSM-5/Al2O3 was studied, the results showed that when the ZSM-5/Al2O3 weight ratio is 1, the CO conversion and selectivity of C2+ alcohol are highest.The characterizations show that the carrier structure and the interaction between active components may be responsibility performance of ZSM-5/Al2O3 composite catalyst. (a) The mixture carrier has different pore structure camparied with single carrier, which may promote the dispersion of active species; (b) The mixture carrier changed the chemical state of surface active species.(4)The study of Si/Al molar ratio of ZSM-5 on Cu-Co/ZSM-5/Al2O3 show that when the Si/Al=50, the CO conversion and selectivity of C2+ alcohol are the best. The change of Si/Al ratio of ZSM-5 affect the pore structure, promote the dispersion of active components and change the chemical state of surface active species. When the Si/Al= 50, The conversion of CO reaches 21.31%, and the selectivity of C2+ alcohols reaches 41.80%.(5) The kinetics of reaction was studied, the effects of internal and extemal diffusion had been excluded by change the space velocity and catalyst particle size. The apparent activation energy and the reaction order with respect to H2 and CO for products were calculated through power law models. The apparent activation energies of methane, methanol, ethanol and carbon dioxide are 553.97 kJ·mol-1,404.38 kJ·mol-1,435.62 kJ·mol-1 and 305.49 kJ·mol-1, respectively.