Catalytic combustion of toluene over mesoporous Cr2O3-supported platinum catalysts prepared by in situ pyrolysis of MOFs

Abstract

Three-dimensional penetrating Pt-loaded mesoporous Cr2O3 catalysts (Pt@M-Cr2O3) were synthesized by pyrolysis of MIL-101-Cr containing pre-impregnated Pt NPs. Physicochemical properties of the samples were characterized by means of various techniques including XRD, Raman, BET, SEM, TEM, XPS and H2-TPR, and their catalytic activities were evaluated by toluene combustion compared with commercial Cr2O3 (C-Cr2O3). It is found that mesoporous Cr2O3 (M-Cr2O3) support with a high surface area of 77.40 m2/g is composed of vast Cr2O3 nanocrystallites. With pre-impregnated Pt loading in MIL-101-Cr, it partly restrains the aggregation of Pt NPs during the pyrolysis of MOFs to M-Cr2O3 and strengthens the interaction between Pt NPs and Cr2O3 nanocrystallites. The obtained 0.82Pt@M-Cr2O3 exhibits the best catalytic performance of toluene combustion, giving 120, 140 and 144 °C of T10%, T50% and T90% under 1000 ppm of toluene at space velocity of 20,000 mL/(g h), respectively. The investigation of the different space velocity, the catalytic stability and the effect of water vapor on catalytic activity over 0.82Pt@M-Cr2O3 have confirmed the good catalytic performance. Furthermore, the studies of in situ DRIFTS indicate toluene degradation over 0.82Pt@M-Cr2O3 is via benzoate species by rapidly transforming of benzylic and aldehydic species, and then oxidized to maleic anhydride in an aromatic-ring opening reaction, finally is decayed to CO2 and H2O.