Oxidative dehydrogenation of isobutane over pyrophosphates catalytic systems

The catalytic effect of metal pyrophosphates (i.e., Mn2P2O7, Ni2P2O7, CeP2O 7, Mg2P2O7, ZrP2O7, Ba2P2O7, V-4(P2O7)(3) and Cr-4(P2O7)(3)) on the oxidati ve dehydrogenation of isobutane to isobutene in the reaction temperature ra nge of 400-600 C-degrees has been investigated. CeP2O7 gives the highest is obutene yield and selectivity (71%), however, V-4(P2O7)(3) is the most acti ve catalyst with an isobutane conversion of 33.5% at 500 C-degrees. Increas ing the reaction temperature results in higher isobutane conversions and lo wer isobutene selectivity. Reaction by-products are propylene, CO, CO2 and traces of methane and ethylene. No oxygenate products are formed under the used reaction conditions. The sum of selectivities of CO, CO2 and methane i s approximately equal to that of propylene, indicating their formation from total oxidation of C-1 species accompanying the isobutane crack reactions. Working at temperatures higher than 550 C-degrees, the homogeneous gas pha se reactions become significant and the oxygen conversion reaches 100%.