Niobium Based Catalysts for Methyl Oleate Epoxidation Reaction

In this paper, nine different catalysts have been used for the epoxidation of methyl oleate with hydrogen peroxide as oxidant. The prepared catalysts were mostly based on supported systems niobia-alumina and niobia-silica. Experimental runs were carried out in a lab-scale reactor, keeping constant operating parameters such as reaction temperature (80 degrees C) and time (5 h), and molar ratio between oxidant and methyl oleate (equal to 4). Runs aimed at the quantitative evaluation of system conversion, yield and selectivity. Nb2O5/SiO2 were found to be active in epoxidation reaction, in particular the catalyst with intermediate niobia loading (6% w/w) showed very high conversion (77%) even if with a very low selectivity to epoxides (30%). Instead, regarding the system based on Nb2O5/Al2O3, both better activity and selectivity were reached. In particular, the material containing 12% of Niobia yielded the highest values for conversion (83%) and selectivity (89%). The results have been critically discussed through the outcomes of a deep characterization of the catalytic materials, carried out through porosimetric, X-ray diffraction, ultra violet and visible diffuse reflection, and Raman microscopy analyses. The discussion highlighted the more relevant parameters able to influence the activity of niobia-based catalysts in the methylesters epoxidation.