C6-Alkane Reactions over gamma-Alumina Supported Palladium Catalysts

A series of Pd/Al2O3 catalysts of different Pd loading were tested in C6-alkane reactions. Different catalyst pretreatment was used to change both the acidity of alumina and the state of palladium. A parallel study with the use of n-hexane and 2,2-dimethylbutane showed several similarities in the catalytic behaviour of the Pd/Al2O3 catalysts. Highly reduced catalysts showed completely different performance than samples reduced at lower temperatures. High temperature reduction leads to a big enhancement of catalytic activity and also vastly increases the isomerization selectivity. Considerable changes were also noticed in the activation energy. Oxidation and subsequent mild reduction of highly reduced samples brings about, however, different results for isomerization selectivity: a partial recovery in the case of n-hexane and only a very small change for the 2,2-dimethylbutane reaction. The results confirm the major contribution of acidic sites present in activated alumina to the overall catalytic behaviour of Pd/Al2O3 samples.