Modulation of selective sites by introduction of N 2O, CO 2 and H 2 as gaseous promoters into the feed during oxidation reactions

Abstract

Results obtained by adding gaseous promoters (CO 2, N 2O and H 2) into the reaction feed are presented for two different reactions: (i) oxidative dehydrogenation of propane (ODP), and (ii) catalytic combustion of methane (CCM). The ODP is performed on a mixture of NiMoO 4 and CeO 2, by adding 3 vol.% CO 2 into the feed, and on a NiMoO 4/[ Si,V] -MCM-41 mesoporous catalyst, in the presence of 1 or 5 vol.% N 2O in the feed. The CCM is carried out (i) on Pd(2 wt.%)/Ce x Zr 1− x O 2 and Pd(2 wt.%)/γ-Al 2O 3 catalysts, on pure CeO 2 and on a mixture of Pd(2 wt.%)/γ-Al 2O 3 and CeO 2 powders, by adding 3 vol.% CO 2 into the feed, and (ii) on a Pd(2 wt.%)/γ-Al 2O 3 catalyst, in the presence of various amounts of H 2 in the feed. It is shown, through all these various examples, that the activity and/or the selectivity of catalysts can be improved by tuning, in a very controlled manner, the oxidation state of active sites via the use of these gaseous promoters.