Role of surface properties of the vanadyl pyrophosphate in the formation of maleic and phtalic anhydrides by n-pentane oxidation

F. CAVANI; A. COLOMBO; F. GIUNTOLI; F. TRIFIRO; P. VÁZQUEZ; P. VENTUROLI

CATALYSIS TODAY

Elsevier

Año: 1996 vol. 32 p. 125 - 130

0920-5861

AbstractThe mechanism of synthesis of maleic and phthalic anhydrides by the gas phase oxidation of n-pentane over VPO-basedcatalysts was studied. The oxidation of the paraffin was carried out under conditions which may lead to the isolation ofpossible reaction intermediates: very low residence time and high n-pentane/oxygen ratio. Under these conditions a numberof by-products were identified, which were attributed to the oxidation of intermediate pentene and pentadiene, as well asother products with more than 5 C atoms, among which were alkylaromatics. Alkylaromatics also were found to be formedin the anaerobic transformation of pentadiene. A mechanism is proposed, which takes into account the oxidehydrogenationof the paraffin to pentene and pentadiene, followed by two parallel pathways: (i) dimerization, dehydrocyclization andaromatization of the diolefin, followed by oxidation of the alkylaromatic to phthalic anhydride, and (ii) multi-step oxidationof pentadiene to maleic anhydride.Keywords: Surface properties; Vanadyl pyrophosphate; Maleic anhydride; Phthalic anhydride; n-Pentane oxidation