Metal phthalocyanines used as catalysts in gas phase reactions: IX. Oxidation and decomposition of 2-propanthiol vapor catalyzed by crystalline monomeric β-metal phthalocyanines of the first transition period

Abstract

Monomeric β-metal phthalocyanines (MPc's) have been shown to be good catalysts for decomposition and oxidation of 2-propanthiol vapor at 250–350 °C. From the heats of activation and the degrees of conversion the following sequences of catalytic activity have been derived: FePc > CuPc > MnPc > CoPc > ZnPc > NiPc for the oxidation and CoPc > CuPc > FePc > ZnPc > MnPc, NiPc for the decomposition. Low heats of activation correspond to high degrees of conversion (FePc, CoPc) and vice versa (NiPc). Metal-free phthalocyanine is found to be inactive. H 2S, formed by decomposition of 2-propanthiol, is strongly adsorbed; therefore, the steady-state degree of conversion of decomposition of 2-propanthiol is low. However, in the presence of O 2, adsorbed H 2S is oxidized readily forming SO 2; the original catalytic activity of MPc's for decomposition of 2-propanthiol is thereby restored. For the same reason, the catalytic activity in oxidation of 2-propanthiol is influenced only to a moderate extent by H 2S inhibition. Heats of activation are independent of the amount of H 2S adsorbed; i.e., H 2S reduces only the number of active centers involved in the reaction.