Characterization of V-based supported catalysts for oxidative dehydrogenation of propane and partial oxidation of crotonaldehyde

Abstract

The vanadium oxide supported catalysts (1 wt. % of vanadium on SiO2- (silica, aerosil), TiO1- anatase, ZrO2, Al2O3 - y-alumina, MgO) were prepared by impregnation method and characterized by means of XRF, N2-BETH, H2-TPR methods. By means of H2-TPR, four different VOx units were determined on the catalyst surface - monomer VOx, oligomer VOx units, bulk V2O5 and inter-oxide species for the basic supports. The catalytic activity of these catalysts was tested in two different oxidation reactions: oxidative dehydrogenation of propane and partial oxidation of crotonaldehyde (but-2-enal) in gas phase. The catalyst prepared were active in both studied reactions, but the activity of the catalyst in each reaction was attributed to different catalytic active sites. The reaction rate of both reactions is in correlation with the given types of active sites: monomer VOx exhibited activity in C3H8 oxudative dehydrogenation, on the other hand oligomer units of VOx were active in partial oxidation of crotonaldehyde. Using of the most acid catalysts resulted in high celectivity in oxidative dehydrogenation reaction. Moreover, reaction scheme for crotonaldehyde oxidation was suggested where the formation of furan proceeds via the oxidative dehydrogenation of ciscrotonaldehyde isomerized on an acid site of the catalysts, followed by the possiblesubsequent oxidation of furan to maleic anhydride (furan-(2,5)-dione). The partical oxidation of crotonaldehyde via crotonic acid (but-2-enoic acid) is the second parallel pathway of the formation of maleic anhydride.