Influence of Impurities in a Methanol Solvent on the Epoxidation of Propylene with Hydrogen Peroxide over Titanium Silicalite-1

The recycled methanol solvent of the HPPO (liquid-phase epoxidation of propylene and hydrogen peroxide to propylene oxide) process usually contains many kinds of trace impurities, such as fusel alcohol, aldehyde, ketone, ester, acetal, and amine. In this study, the influence of these impurities on the catalytic performance of titanium silicalite-1 (TS-1) in the liquid-phase epoxidation of propylene with H2O2 was investigated with a batch reactor and simulated methanol solvents. The results show that amine and acetone are the most hazardous impurities, as they could remarkably suppress the conversion of H2O2. Furthermore, competitive adsorption experiments and IR and UV-Raman spectroscopic studies indicate that the suppression effect of impurities on the catalytic activity of TS-1 can be attributed to the competitive adsorption of the impurities on the tetra-coordination framework Ti sites. With this funding, the suppression mechanism of different impurities in a methanol solvent on the catalytic activity of TS-1 in the liquid-phase epoxidation of propylene was discussed.

Epoxidation of Karanja (Millettia pinnata) Oil Methyl Esters in the Presence of Hydrogen Peroxide over a Simple Niobium-Containing Catalyst

The synthesis, characterization and catalytic performance of a conceptually simple, novel NbOx-SiO2 catalyst are here described. The niobium(V)-silica catalyst was prepared starting from cheap and viable reactants, by alkaline deposition of NH4Nb(C2O4)2·H2O in the presence of fructose as a stabilizer and subsequent calcination. The NbOx-SiO2 solid (0.95 Nb wt.%) was tested in the liquid-phase epoxidation with aqueous hydrogen peroxide of methyl oleate, as a model substrate. It was then tested in the epoxidation of a mixture of methyl esters (FAMEs) obtained by transesterification with methanol and purification of karanja oil, extracted from the autochthonous Indian variety of Millettia pinnata tree. The catalyst showed a promising performance in terms of methyl oleate conversion (up to 75%) and selectivity to epoxide (up to 82%). It was then tested on the FAME mixture from karanja oil, where interesting conversion values were attained (up to 70%), although with lower selectivities and yields to the mixture of desired epoxidized FAMEs. The solid withstood four catalytic cycles overall, during which a non-negligible surface reorganization of the Nb(V) sites was observed. However, this restructuring did not negatively affect the performance of the catalysts in terms of conversion or selectivity.

Enhancing ethylene epoxidation of a MWW-type titanosilicate/H2O2 catalytic system by fluorine implanting

SiO3/2F units in the framework of Ti-MWW generate stronger hydrogen-bonding between Hend in Ti–Oα–Oβ–Hend intermediates and the adjacent Si–F species, which effectively improves the catalytic performance of Ti-MWW for the liquid-phase epoxidation of ethylene.