Metal phthalocyanines used as catalysts in gas phase reactions: IV. Oxidation of 2-propanol catalyzed by monomeric β-Cu-phthalocyanine in the presence of sulfur compounds

Abstract

The stability of monomeric β-Cu-phthalocyanine (CuPc) against poisoning by sulfur compounds has been shown with respect to catalytic oxidation at 350 °C of 2-propanol to acetone and water in the presence of 2-propanthiol in threefold excess to 2-propanol. H 2S, generated by decomposition of 2-propanthiol, blocks the active sites (the central Cu ions) of the CuPc. In the presence of O 2, H 2S is oxidized to SO 2 and H 2O. The steady state activity of CuPc in the presence of 2-propanthiol is 45% of the activity in the absence of sulfur compounds. When O 2 is absent, as in the study of the decomposition of 2-propanthiol, CuPc is poisoned to 8% of the initial activity. By titration of the adsorbed H 2S with pulses of O 2 it is shown that H 2S is not only adsorbed at the active sites on the outer (010) faces of the CuPc crystals but penetrates into the interior. The ability of small molecules such as O 2 or H 2S to penetrate into the CuPc lattice is further shown by comparison of the amount of adsorbed O 2, titrated by pulses of 2-propanol, and the amount of adsorbed 2-propanol, titrated by pulses of O 2.