Modulation of selective sites by introduction of N2O, CO2 and H2 as gaseous promoters into the feed during oxidation reactions

Results obtained by adding gaseous promoters (CO2, N2O and H2) 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 NiMoO4 and CeO2, by adding 3 vol.% CO2 into the feed, and on a NiMoO4/[Si,V]-MCM-41 mesoporous catalyst, in the presence of 1 or 5 vol.% N2O in the feed. The CCM is carried out (i) on Pd(2 wt.%)/CexZr1−xO2 and Pd(2 wt.%)/γ-Al2O3 catalysts, on pure CeO2 and on a mixture of Pd(2 wt.%)/γ-Al2O3 and CeO2 powders, by adding 3 vol.% CO2 into the feed, and (ii) on a Pd(2 wt.%)/γ-Al2O3 catalyst, in the presence of various amounts of H2 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.