Effect of Synthesis Conditions on the Structure and Catalytic Performance of V- and Ce-Incorporated SBA-15-like Materials in Propane Selective Oxidation

Vanadia- and/or ceria-incorporated SBA-15-like materials were prepared by impregnation and one-pot hydrothermal synthesis procedures at different solution pH values. The pH of the synthesis solution was found to have a very strong effect on the pore structure, chemical composition, and morphology of the synthesized materials. Materials synthesized by impregnation of V and/or Ce and by the one-pot hydrothermal route at pH << 1.0 showed the characteristic ordered pore structure of SBA-15. However, the materials prepared by the one-pot synthesis route at pH 1.5 gave complex pore structures with bottleneck-shaped and/or slit-like interconnected pores. Activity tests in the selective oxidation of propane showed higher activities for the V-incorporated materials than for the materials containing Ce and V-Ce. Catalysts synthesized by impregnation gave higher propane conversions. However, the propylene selectivity values were higher with the catalysts prepared by the one-pot route. An increase in the temperature from 550 to 600 degrees C led to increases in both the conversion and the propylene selectivity with the V- and V-Ce-incorporated materials prepared by the one-pot procedure at pH 1.5. For the V-incorporated catalyst prepared by this route, the propane conversion and propylene selectivity were obtained as 40% and 62%, respectively, at a space time of 0.4 s.g.cm(-3) and a temperature of 600 degrees C.