Palladium supported on carbon nanotube modified nickel foam as a structured catalyst for polystyrene hydrogenation

Abstract

A structured support of carbon nanotubes modified nickel foam (CNTs@NF) was synthesized through a facile method of chemical vapor deposition. The entangled CNTs layer with open pores and the dense carbon layer beneath covered around the skeleton of nickel foam establishes a hybrid hierarchical structure with large effective surface area which dramatically promotes the internal diffusion of large polystyrene (PS) coils. Palladium was chosen as the catalyst for PS hydrogenation and deposited on the CNTs@NF support in the form of nanoparticles. Characterization analysis including scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), thermo gravimetric analysis (TGA), Raman spectrum and N2 physisorption were conducted to investigate the morphology and structure of the resulting Pd supported on CNTs@NF catalysts (Pd/CNTs@NF). The macroscopic structured Pd/CNTs@NF catalyst was applied to PS hydrogenation and displayed a quite excellent hydrogenation activity with a final hydrogenation degree (HD) of 73.6%, almost 8 times higher than nickel foam supported Pd catalyst (Pd/NF) and remarkably similar to powdered CNTs supported Pd catalyst (Pd/CNTs) under the identical condition. Moreover, the turn-over-frequency (TOF) of Pd/CNTs@NF (0.041 s−1) was also comparable to Pd/CNTs (0.056 s−1), which confirmed a similar intrinsic catalytic activity of Pd on both supports. Inspiringly, the performance of Pd/CNTs@NF catalyst was comparable to powdered Pd/CNTs catalyst with the merit of eliminating filtration operation. It has revealed the structured Pd/CNTs@NF catalyst with outstanding recyclability could be an attractive alternative to the powdered Pd/CNTs catalyst for heterogeneously catalyzed polymers hydrogenation reactions.