2020 Volume 63 Issue 5 Pages 267-273
The effect of Ce addition to a Bi–Mo complex oxide catalyst supported on SiO2 was examined on the partial oxidation of propylene to acrolein. The catalyst consisted of an oxygen-supply phase in which the lattice oxygen in Mo-oxide was doped with transition metals such as Fe, Ni and Co and was supported by SiO2 and a catalytic-active phase that involved hydrogen abstraction from a reactant in the Bi-center of Bi–Mo oxide, which was supported by the oxygen-supply phase. In the present study, Ce was added to the oxygen-supply phase to enhance its redox nature. Ce addition was advantageous particularly under oxygen-rich conditions in the feed stream. For example, at P(C3H8) = 10.1 kPa and P(O2) = 15.5 kPa at 623 K, the yield of acrolein was slightly enhanced from 57.6 % with 0 % Ce doping to 65.3 % with 20 % Ce doping at 6 h on-stream. However, under more oxygen-rich conditions at P(C3H8) = 10.1 kPa and P(O2) = 31.0 kPa at 623 K, the yield of acrolein was approximately doubled from 27.7 % with 0 % Ce doping to 61.8 % with 20 % Ce doping at 6 h on-stream. Analysis using XPS of the previously used catalysts for the reaction in the absence of gaseous oxygen confirmed the unique redox behavior between the catalytic-active phase and the oxygen-supply phase as the lattice oxygen in the catalytic-active phase was replenished from the oxygen-supply phase to maintain the surface properties of the catalytic-active phase. The XPS results and the remarkable effect of Ce addition to the oxygen-supply phase under oxygen-rich conditions confirmed the validity of the concept of the catalyst preparation consisting of an oxygen-supply phase and a catalytic-active phase.
