Catalytic Hydrogenolysis of Phenothiazine, Thianthrene, and Phenoxathiin

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Abstract
Catalytic hydrogenolysis of phenothiazine, thianthrene, and phenoxathiin as appropriate model reactants in the competing reactions of sulfur, nitrogen, and oxygen removal over NH4Y zeolite, pre-sulfided Co–Mo–Al2O3, and Ni–W–SiO2Al2O3 catalysts has been carried out using the batch method. The cleavage patterns and the schemes in the hydrogenolysis of the three compounds and the active sites of an NH4Y zeolite for the hydrogenolysis are discussed. The C–S bond in phenoxathiin was more prone to cleavage than the C–O bond, and the C–N bond in phenothiazine was not broken in our experiments. Sulfur removal from the three compounds took place more than the removal of nitrogen or oxygen. The reactivity over the zeolite Y, pre-sulfided Co–Mo–Al2O3, and Ni–W–SiO2Al2O3 catalysts decreased in the order of phenothiazine>phenoxathiin>thianthrene, but in the absence of the catalyst the thermal stability was phenoxathiin>thianthrene>phenothiazine. In the hydrogenolysis of the three compounds over the NH4Y catalyst the desulfurization activity of the zeolite Y catalyst was maximized when calcined at 500 °C. The reaction of phenoxathiin was found to be accelerated by Brönsted acid, but this did not hold true in the case of phenothiazine and thianthrene.