The oxygen-assisted transformation of propane to COx/H2 through combined oxidation and WGS reactions catalyzed by vanadium oxide-based catalysts

Abstract

This paper reports about the gas-phase oxidation of propane catalyzed by bulk vanadium oxide and by alumina-and silica-supported vanadium oxide. The reaction was studied with the aim of finding conditions at which the formation of H 2 and CO 2 is preferred over that of CO, H 2 O and of products of alkane partial oxidation. It was found that with bulk V 2 O 5 considerable amounts of H 2 are produced above 400 8C, the temperature at which the limiting reactant, oxygen, is totally consumed. The formation of H 2 derived from the combination of: (i) oxidation reactions, with generation of CO, CO 2 , oxygenates (mainly acetic acid), propylene and H 2 O, all occurring in the fraction of catalytic bed that operated in the presence of gas-phase oxygen, and (ii) WGS reaction, propane dehydrogenation and coke formation, that instead occurred in the fraction of bed operating under anaerobic conditions. This combination of different reactions in a single catalytic bed was possible because of the reduction of V 2 O 5 to V 2 O 3 at high temperature, in the absence of gas-phase oxygen. In fact, vanadium sesquioxide was found to be an effective catalyst for the WGS, while V 2 O 5 was inactive in this reaction. The same combination of reactions was not possible when vanadium oxide was supported over high-surface area silica or alumina; this was attributed to the fact that in these catalysts vanadium was not reduced below the oxidation state V 4+ , even under reaction conditions leading to total oxygen conversion. In consequence, these catalysts produced less H 2 than bulk vanadium oxide.

V–Al–O catalysts prepared by flame pyrolysis for the oxidative dehydrogenation of propane to propylene

“…Here, however, a better solvent/precursor selection was precluded (vide supra) by solubility problems for the precursors. impregnation of a high-surface-area alumina [45]. In that case, however, the gain in selectivity achieved with the anaerobic operation, with respect to the co-feed, was not higher than 20%.…”

“…Fig.9b plots the change of selectivity to propylene as a function of propane conversion, at 550°C; it is worth reminding that the higher propane conversion was obtained, for each catalyst, at the beginning of the reactivity test, when the sample was still oxidized. The decrease of conversion caused an improvement of selectivity to propylene, due both to the lower consecutive propylene combustion and to an increasing contribution of propane dehydrogenation versus oxidative dehydrogenation on the more reduced catalyst [45][46][47][48]. however, was slightly higher than that one of propylene (1.7 mol%), because the formation of coke also contributed to hydrogen formation.…”

EPR enlightening some aspects of propane ODH over VOx–SiO2 and VOx–Al2O3

“…Oxidative dehydrogenation (ODH) of propane to propylene represents an interesting alternative to the energy demanding dehydrogenation process and supported VOx demonstrated promising catalysts for this reaction [1][2][3][4][5][6][7][8][9][10]. Different supports have been tested, such as ZrO2 [11,12], TiO2 [13], V-substituted zeolites or silicalites [14], SiO2 [7,9,11] and Al2O3, usually as the -phase [3,[4][5][6]8,10,11,13].…”

“…Different supports have been tested, such as ZrO2 [11,12], TiO2 [13], V-substituted zeolites or silicalites [14], SiO2 [7,9,11] and Al2O3, usually as the -phase [3,[4][5][6]8,10,11,13].…”

Synthesis of V2O3/C composites with different morphologies by a facile route and phase transition properties of the compounds

“…A broad second-order transformation occurs at about 350 K to about 550 K from a PM phase to a second metal (PM') phase [19,21,22]. These feature properties make V 2 O 3 and its derivative compounds to have wide practical applications, such as optical devices, temperature sensors, field effect transistors, conductive composite polymer, catalyst and so on [19,[23][24][25][26].…”