Experimental studies and kinetic regularities of isobutane dehydrogenation over Ga2O3/Al2O3

Catalytic behavior of 6 wt% of Ga/Al2O3 in isobutane dehydrogenation has been investigated in a laboratory-scale fixed-bed reactor at atmospheric pressure. Experiments were performed in the temperature range of 520-580 degrees C and a short residence time of 0.03-0.30 s, allowing operation far from equilibrium. Among the major by-products, besides methane and propene, three butene isomers (1- and 2-butenes) were formed, not generated by isobutene isomerization according to Gibbs free energy calculations. The observed isobutane transformation rates and the apparent Arrhenius parameters were determined. An extent of thermal dehydrogenation reactions, occurring without a catalyst, was limited to 2 mol.% conversion. The overall rate was not an additive of thermal and catalytic contributions, as presence of catalysts clearly inhibited formation of radicals. For comparison, a catalyst with a similar content of chromia was investigated under the same conditions. The apparent activation energy for gallia/alumina catalyst was 191 kJ/mol, which is larger compared to chromia/alumina catalyst, exhibiting 105 kJ/mol, while reaction orders in isobutane were the same for both catalysts under identical experimental conditions.