Heteropoly compounds .30. Alkane oxidation with mixed addenda heteropoly catalysts containing Ru(III) and Rh(III)

Oxidation of alkanes, mainly of cyclohexane, with t-butyl hydroperoxide (TBHP) catalyzed by alkylammonium salts of mixed addenda heteropoly compounds having Keggin-type polyanions were studied in benzene solutions, with regard to the relative catalytic activity, reaction orders and the stability of catalysts. Tetra-n-hexylammonium salts of SiRu(H2O)W11O395- and SiRh(H2O)W11O395- showed higher catalytic activities than the corresponding Fe- and Go-substituted catalysts for the selective oxidation of cyclohexane to cyclohexanol and cyclohexanone. Although the Ru catalyst was possibly a mixture, it consisted mainly of SiRu(H2O)W11O395- and gave reproducible catalytic performance for repeated preparations. The initial rates were approximately proportional to the concentrations of cyclohexane, TBHP and the catalyst. Although the rate decreased with the consumption of TBHP, the initial rate was resumed by the addition of TBHP, indicating the absence of the deterioration of catalytic activity. Similarly alcohols and ketones were selectively formed from n-decane and ethylbenzene.