This report deals with the results of a study on the oxidation of cyclohexanone to adipic acid with air,\ud
catalysed by Keggin-type polyoxometalates of composition H3+xPMo12−xVxO40 (x = 1 and 2), which was\ud
carried out in a semi-continuous stirred-tank reactor. It was found that when conducted in the presence\ud
of a water-only solvent, the reaction proceeds with a redox mechanism, in which the step of\ud
reoxidation of the reduced POM by oxygen is rate limiting. When, however, the reaction was carried\ud
out with an acetic acid co-solvent, a radical-chain autoxidation mechanism prevailed, especially when\ud
very low amounts of catalyst were used. Autoxidation overlapped with the redox mechanism when the\ud
catalyst-to-cyclohexanone ratio was increased. Moreover, the composition of the polyoxometalate, that\ud
is, the number of V atoms per Keggin unit, affected the relative importance of the two mechanisms. The\ud
selectivity to adipic acid achieved was a function of the reaction mechanism, but also was affected by\ud
cyclohexanone conversion, due to the presence of a complex reaction network
This paper deals with the catalytic properties of different supported heteropolyacids (HPAs), both molybdenum- and tungsten-based, in the oxidative desulfurization process of diesel. We are jointly developing a new oxidative desulfurization process, aimed at reducing the sulfur content in diesel to less than 10 ppm (parts per million) using in situ produced peroxides. In this new process, high-molecular-weight organosulfur compounds, such as 4,6-dimethyl-dibenzothiophene (DMDBT), difficult to be eliminated by conventional hydrodesulfurization, are oxidized to the corresponding sulfones and subsequently removed by adsorption. Molybdenum-based HPAs, with Keggin structure, proved to be the most active and selective catalysts for oxidizing DMDBT with on-stream lifetimes exceeding 1500 h time on stream (t.o.s.).
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.