Partial oxidation of C-5 hydrocarbons to maleic and phthalic anhydrides over molybdate-based catalysts

The study presented in this paper demonstrates the use of molybdena-based catalysts in the partial oxidation of n-pentane and 1-pentene to phthalic and maleic anhydrides. The catalysts used are two-phase materials consisting of molybdenum oxide and a simple molybdate. The catalysts have been characterized by BET surface area measurement, laser Raman spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy and temperature-programmed desorption techniques. The reaction studies have been performed using a fixed-bed flow reactor. The phenomenon of contact synergy and the effect of reaction parameters have been examined. The reaction and TPD experiments suggest that MoO3 has the sites for the activation of pentane. At lower temperatures, it is also possible to perform the oxygen insertion steps and/or C-C bond formation steps. However, at higher temperatures, the cracking and complete oxidation reactions become more dominant, changing the product distribution in favor of lower alkanes and alkenes and carbon oxides. The presence of two phases (MoO3 and MnMoO4) in close proximity appears to control the complete oxidation step while allowing the desorption of partially oxidized and/or coupled products.