Catalytic testing of TiO2/platinum/silicalite-1 composites

The synthesis, characterisation and testing of a composite catalyst, consisting of TiO2-supported platinum catalyst particles covered with a 0.8–1.3 µm thick silicalite-1 layer, are described. The composite shows mass transport selectivity, which is demonstrated by the high ratios of the initial conversion rates in the competitive hydrogenation of a linear and a dibranched alkene, reaching average values of 35 at 100 °C. At the temperatures applied, adsorption of the alkene is dominant and hydrogen supply to the catalytic sites is relatively small. As a result the double-bond migration is more pronounced than with an uncovered platinum catalyst. At the catalytic sites of the composites steric constraints are observed, which lead to regioselectivity in the hydrogenation of long-chain alkenes. A linear alkene with a terminal double bond is converted preferentially over an isomer with an internal double bond.