Simple molybdate selective oxidation catalysts containing excess MoO3 for C4 hydrocarbon oxidation to maleic anhydride

摘要

The selective oxidation of C(,4) hydrocarbons to maleic anhydride over NiMoO(,4) and CoMoO(,4) catalysts containing excess MoO(,3) was studied using a fixed bed, integral reactor system. The synthesis of pure phases and the techniques for incorporating excess MoO(,3) have been investigated. Synthesis techniques included precipitation, solid state reaction, and impregnation. Extensive characterization of the catalyst has been performed using complementary instrumentation techniques, including laser Raman spectroscopy, Raman microprobe spectroscopy, x-ray diffraction, x-ray fluorescence, x-ray photoelectron spectroscopy, scanning electron microscopy, and energy dispersive x-ray analysis. Activity and selectivity measurements were performed using these catalysts for 1-butene, 1,3-butadiene, and furan oxidation. The most selective component of the catalyst for maleic anhydride production was determined to be a MoO(,3) phase which possessed a surface covering of NiMoO(,4). NiMoO(,4) was found to have a multifunctional role in the catalytic job distribution, including catalysis of the oxidative dehydrogenation of 1-butene to 1,3-butadiene and establishment of selectivity for maleic anhydride by selectively blocking complete oxidation sites on the MoO(,3) surfaces. Post-reaction characterization by laser Raman spectroscopy, Raman microprobe spectroscopy, x-ray photo-electron spectroscopy, and scanning electron microscopy revealed that the catalyst was stable for prolonged reaction times.