Influence of Na content on the catalytic properties of Pt-Ir/Al2O3 catalysts for selective ring opening of decalin

Abstract

The influence of the Na addition on Pt-Ir/Al2O3 on the reaction of selective ring opening of decalin and methyl cyclopentane was studied. The catalysts were evaluated by means of TPR, pyridine TPD, TEM, FTIR-CO and by the reaction tests of cyclohexane dehydrogenation, hydrogenolysis of cyclopentane, selective ring opening of decalin and methyl cyclopentane. It was found that Na strongly decreases the acidity and influences the metal properties of Pt-Ir/Al2O3 catalysts. The interaction between Pt and Ir is increased by the presence of Na, with larger metal crystals being obtained on the support modified by Na. As a consequence, the catalytic properties are also modified and the CP/CH ratio (parameter of demanding/not demanding reaction) is increased with sodium concentration. In the case of MCP reaction, Na strongly decreases the aromatic and n-C6 formation and favors the selective reaction mechanism, thus favoring the formation of 2MP and 3MP. For the decalin reaction, it was found that the yield to the dehydrogenated product of the catalysts supported on Al2O3-Na is lower than that of the free Na-alumina supported catalyst, whereas the opposite occurs with the yield to C1 due to the higher hydrogenolytic and lower dehydrogenation activity of the catalysts with Na. The yield to ring contraction (RC) products is higheron the catalyst without Na due to the higher acidity which favors the ring contraction reaction and the lower metallic activity; thus, the transformation of the RC product to ring opening products is decreased.