Graphene as efficient and robust catalysts for catalytic wet peroxide oxidation of phenol in a continuous fixed-bed reactor

Abstract

Monolayer graphene film (Gr) as a metal-free catalyst was synthesized on the paper-like sintered stainless steel fibers (PSSF) with three-dimensional net structure by chemical vapor deposition (CVD) technique. The prepared PSSF-Gr was characterized by SEM, EDS, XRD, AFM, TEM, and Raman spectroscopy. Then, the optimum reaction conditions for catalytic wet peroxide oxidation (CWPO) of phenol in a continuous reactor using PSSF-Gr catalysts were explored by analyzing the effects of reaction temperature, feed flow rate, and catalyst bed height on catalytic performance. Moreover, the long-term stability of PSSF-Gr catalyst was investigated and demonstrated complete phenol oxidation and dramatic TOC removal (values ranging between 80.7% and 91.0%) after continuously operating for 72 h under optimum condition. Finally, a reasonable reaction mechanism for CWPO of phenol was proposed by analyzing the HPLC results and evolution of aromatic intermediates content. From these results, seldom toxic aromatic intermediates were observed on account of the production of short-chain organic acids by opening of aromatic ring, which subsequently mineralized to CO2 and H2O. The simple preparation method, unique structure, extraordinary catalytic activity and stability of the graphene-based material would provide a new potential catalyst for environmental catalysis.