Hydrogenation of commercial polystyrene on Pd/TiO2 monolithic ceramic foam catalysts: catalytic performance and enhanced internal mass transfer

摘要

Monolithic TiO2 ceramic foam (CF) supported palladium nanoparticles, possessing three-dimensional structure with open accessible pores, were developed as effective catalysts for the hydrogenation of commercial polystyrene. The monolithic CF was synthesized through uniform coating of TiO2 on synthetic template and partial sintering. The mechanical and structural properties of CF were investigated. The distribution and texture of Pd nanoparticles on the CF and their hydrogenation performances were studied. Furthermore, the internal mass transfer analysis of PS coils during the hydrogenation was evaluated. The results showed that the TiO2 CF-0.652 possessed interconnected cell windows of 400-600 mu m and macropores of 200-300 nm on the struts. In 0.06 wt% Pd/CF-0.652, Pd nanoparticles (5.0 nm) were located on the surface of the TiO2 ceramic base, the dispersion of Pd was 34.3 %. As the Pd loading increased, the dispersion of Pd on the Pd/CF significantly decreased. The activity of Pd for PS hydrogenation slightly increased when the Pd loading increased from 0.06 to 0.45 wt%, which could be explained by the existence of interaction between Pd atoms and TiO2 CF at low metal loadings. For Pd/CF-0.652 catalysts, the Weisz modulus was calculated to be less than 0.30, indicating that internal diffusion limitation inside the Pd/CF-0.652 catalysts could be neglected for unique macropores on the struts.