Regioselective hydrogenation of alkenes over Pt-loaded zeolite BEA

The hydrogenation of dec-1-ene and of (E)-dec-5-ene has been studied over platinum/Na-BEA and non-zeolitic platinum catalysts. Provided that the solvent does not compete with the substrates for sorption in the zeolite, and that the external surface platinum is deactivated with a bulky phosphine, dec-1-ene is hydrogenated 18 times faster than (E)-dec-5-ene, whereas the ratio is only ca. 2 for platinum on non-microporous supports. This regioselectivity is explained by steric constraints imposed by the microporous structure of the zeolite. The hydrogenation rate over platinum/Na-BEA is much lower than that observed over the amorphous supported platinum catalysts; further, for the zeolite-based catalyst, approximately first-order kinetics are found compared with zero-order for the amorphous catalysts. Both effects can be explained in terms of alkene coverage of the Pt sites in the two types of catalyst.