OXIDATION OF ISOBUTANE ON A HETEROPOLYCOMPOUND HYDROGEN RESERVOIR

The selective oxidation of isobutane to methacrylic acid (MAA) has bee n studied on Cs1.6H2.4P1.7Mo11V1.1O40 which is a heteropolycompound (H PC). The oxidation mechanism isobutane --> isobutene --> MAL --> MAA h as already been proposed previously with a rate determining step corre sponding to the first step of the reaction, i.e., to dehydrogenation o f isobutane leading to isobutene. Here we show that the HPC which is a ctive in the oxidation of isobutane possesses, in the reduced state, a nionic vacancies able to store reactive hydrogen species H presenting the ability to diffuse through the solid. Such a result is of great i mportance since dehydrogenation requires the abstraction of hydrogen f rom the molecule which could be performed by a lacunar phase. Therefor e, a mechanism of the dehydrogenation step is proposed. involving a he terolytic abstraction of a H- species from the alkane.