Vanadium-phosphorous-oxygen industrial catalysts for C4 hydrocarbon selective oxidation to maleic anhydride

Wenig, Robert
Journal Title
Journal ISSN
Volume Title
Source URI
Research Projects
Organizational Units
Journal Issue

The selective oxidation of n-butane to maleic anhydride by vanadium-phosphorus-oxygen (V-P-O) industrial catalysts varying in P-to-V ratio has been studied. V-P-O catalysts have been synthesized, characterized, and the reactivity of these catalysts has been studied in a fixed bed integral reactor system. Catalyst characterization studies including X-ray diffraction, laser Raman spectroscopy, infrared spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy, X-ray energy dispersive spectroscopy, and BET surface area measurements were used. A strong effect of P-to-V synthesis ratio on catalyst structure, catalyst morphology, vanadium oxidation state, and reactivity in n-butane selective oxidation was observed. A slight "excess" of catalyst phosphorus (P/V = 1.1 catalyst) was found to stabilize an active and selective (VO)(,2)P(,2)O(,7) phase. The mechanism of n-butane selective oxidation to maleic anhydride was studied by in situ infrared spectroscopy using n-butane, 1-butene, 1,3-butadiene, crotyl alcohol, maleic acid, crotonic acid, and maleic anhydride feeds. During paraffin selective oxidation, highly reactive olefin species and maleic acid were observed on the surfaces of V-P-O catalysts. Further evidence in support of conjugated or possibly strained olefin and maleic acid reaction intermediates in n-butane and 1-butene partial oxidation to maleic anhydride was gathered.

Chemical engineering