NiMoO₄ selective oxidation catalysts containing excess MoO₃ for the conversion of C₄ hydrocarbons to maleic anhydride. II. Selective oxidation of 1-butene

The selective oxidation of 1-butene to maleic anhydride over NiMoO₄ catalysts containing "excess" MoO₃ was studied using a fixed-bed, integral reactor system. Activity and selectivity measurement were performed using catalysts which had been prepared by precipitation, impregnation, or solid-state reaction and which had previously undergone extensive characterization. The most selective component of the catalyst for maleic anhydride production was determined to be a MoO₃ phase which possessed a surface covering of NiMoO₄. Postreaction characterization by laser Raman spectroscopy. Raman microprobe spectroscopy, X-ray photoelectron spectroscopy, and scanning electron microscopy revealed that the catalyst was stable for prolonged reaction times.