Metal phthalocyanines used as catalysts in gas phase reactions: X. Decomposition and reduction of NO catalyzed by crystalline monomeric β-metal phthalocyanines of the first transition period

Abstract

Monomeric β-metal phthalocyanines (MPc's) of the first transition row (Mn to Cu) have been shown to be good catalysts with respect to both reduction of NO in H 2 flow and decomposition of NO either in H 2 or in He flow in the temperature range of 180 to 425 °C. Depending on the central metal atom, in H 2 flow either reduction of NO to N 2 and H 2O (CuPc, NiPc above a certain concentration of NO) or to NH 3 and H 2O (CoPc, NiPc below a certain concentration of NO) is observed. Decomposition (MnPc, FePc) leads to N 2 and O 2, the latter apparently strongly adsorbed by MPc's. From the apparent heats of activation as well as from the degrees of conversion normalized to constant weight of the catalyst, the sequence of catalytic activity with respect to reduction of NO is found to be NiPc > CoPc ⪢ CuPc > MnPc > FePc. In contrast, catalytic activity with respect to decomposition of NO shows the following sequence: MnPc > FePc ⪢ CuPc > NiPc > CoPc. H 2Pc is found to be inactive.