Modifying SBA-15 with Binary Elements of Chromium and Molybdenum for Improved Catalytic Performance in the Oxidative Dehydrogenation of Isobutane to Isobutene

Abstract

In the oxidative dehydrogenation of isobutane to isobutene, selectivity and stability were improved by introducing chromium and molybdenum into SBA-15. The direct synthesis method (DM) was used to introduce these binary elements into SBA-15. Use of the DM resulted in a higher specific surface area of the catalyst and a greater dispersion of chromium and molybdenum species compared with a corresponding binary catalyst prepared using the incipient wetness impregnation method (IM). Selectivity to isobutene was improved, along with a decrease in the selectivities to CO and CO2 with the introduction of greater amounts of molybdenum, which suggests that molybdenum must suppress the tendency of isobutene to over-oxidate to either CO or CO2. The molybdenum species must be in close proximity to the chromium species, which results in the formation of an active Cr-O-Mo site.