Properties of Sm2O3-ZrO2 composite oxides and their catalytic performance in isosynthesis

摘要

Sm2O3 doped ZrO2-based catalysts(Sm2O3-ZrO2 composite oxide)were prepared by co-precipitation and their physical properties(texture and structure)and chemical properties(acid-base and redox)were characterized with the methods of N2 adsorption-desorption isotherm,powder X-ray diffraction,Raman spectroscopy,NH3 and CO2 temperature programmed desorption and H2 temperature programmed reduction.The catalytic performances of the catalysts(activity and selectivities)were evaluated in the CO hydrogenation to isobutene and isobutane(isosynthesis)under the reaction conditions of 673 K,5.0 MPa,and 650 h~(-1).The relationship between the catalytic performance and the physical/chemical properties of Sm2O3-ZrO2 catalysts were also examined.The catalytic activity and selectivity of the Sm2O3-ZrO2 catalysts varied with Sm2O3 doping.The physical properties of the catalysts,such as cumulative pore volumes,average pore diameters and crystal sizes had some influences on the activity and selectivity in the isosynthesis.CO conversion increased with an increase in the amount of the acidic sites on the surface of Sm2O3-ZrO2 catalysts,while iso-C4 percentage in total hydrocarbons increased with an increase in the amount of the basic sites.The addition of Sm2O3 into ZrO2 enhanced the reducibility of Sm2O3-ZrO2 catalysts.The highest CO conversion(21.6%)and C4 selectivity(41.8%)were obtained over the catalyst that had a maximum amount of H2 consumptions(57.7 mu mol g~(-1))in the TPR measurement for Sm2O3-ZrO2 catalysts.A coordination of the acid-base properties and the redox property may play important role for the improvement of the catalytic performances of the isosynthesis.