Synthesis of Reduced Graphene Oxide-Carbon Nanotubes (rGO–CNT) Composite and Its Use As a Novel Catalyst Support for Hydro-Purification of Crude Terephthalic Acid

Abstract

Palladium nanocatalysts supported on reduced graphene oxide (rGO), multi walled carbon nanotubes (MWCNT), and rGO/CNT composite were synthesized by a wet impregnation method using PdCl2 as a precursor. Palladium loading was 0.3 wt %, and the catalysts were reduced at 300 °C. The catalysts were characterized by inductively coupled plasma, Brunauer−Emmett−Teller (BET) analysis, Fourier transform infrared spectroscopy, X-ray powder diffraction, transmission electron microscopy, temperatue-programmed reduction, temperatue-programmed desorption, and Raman spectroscopy. The performance of the catalysts was investigated for hydro-purification of crude terephthalic acid (CTA) containing 2100 ppm 4-carboxybenzaldehyde (4-CBA) as an impurity. The reaction products were analyzed by HPLC to determine the amounts of 4-CBA, benzoic acid, and p-toluic acid. Pd/rGO–CNT catalyst had excellent performance in terms of both selectivity and 4-CBA conversion. All catalysts exhibited more than 99% removal of 4-CBA. The most desired selectivity, however, was obtained for the catalyst with rGO–CNT as a support. Comparison with the performance of the commercial catalyst (0.5 wt % palladium on activated carbon) indicated that the Pd/rGO–CNT catalyst had a better performance.