Tunable growth of carbon nanotubes forests on nickel foam as structured support for palladium catalyst toward polystyrene hydrogenation

Heterogeneous catalytic hydrogenation of polystyrene (PS) over classical porous catalysts to polycyclohexylethylene (PCHE) with added commercial values is severely limited by pore diffusion of polymer coils due to the large molecule size and high solution viscosity. To improve accessibility of PS to active sites and eliminate catalyst separation, a structured catalyst, Pd supported on CNTs decorated nickel foam (Pd/CNTs@NF) was prepared and displayed an excellent hydrogenation activity. The high performance could be contributed to the non-porous and wide-open structure of CNTs layer and strong pi-pi interaction between CNTs surface and PS molecules which facilitates the diffusion and adsorption of PS coils respectively. The average diameter and graphitization degree of CNTs could be tuned by adjusting the chemical vapor deposition (CVD) temperature and consequently its surface area and interaction with PS molecules. CVD temperature was optimized to obtain PcliCNTs@NF with highly dispersed Pd nanoparticles and enhanced adsorption capacity of PS. It shows great industrial potential for structured Pd/CNTs@NF catalyst with outstanding catalytic activity and stability. (C) 2019 Taiwan Institute of Chemical Engineers. Published by Elsevier B.V. All rights reserved.