The effects of intraparticle diffusion on the yield of the liquid-phase hydrogenation of phenylacetylene in a stirred basket reactor.

Abstract

The liquid-phase consecutive hydrogenations of phenylacetylene are investigated in the presence of a 0.5% Pt-Al2O3 catalyst. Experiments are performed in a stirred reactor with basket impellers in which the catalyst pellets are held, and a stirred slurry reactor in which the finely powdered pellets are suspended. The intrinsic kinetic equations are derived empirically from the rate measurements with the powdered catalysts. Under the intrinsic kinetic limitation, the intrinsic yield of styrene is independent of both the initial concentration of phenylacetylene and the hydrogen concentration. With the catalyst pellets the hydrogenation rates and the yields are significantly influenced by the intraparticle diffusion. The yield in the regime of the diffusional limitation is reduced below the intrinsic yield, but it is restored up to the level of the intrinsic yield with increasing initial concentration of phenylacetylene and/or decreasing hydrogen concentration. The intraparticle diffusion effects on the hydrogenations are modeled theoretically and solved numerically. By the favorable assessment of the effective diffusivities of the reaction species, the calculated conversion and yield are in good agreement with the experimental results.