Coking of Pt/γ-Al2O3 catalyst in landfill gas deoxygen and its effects on catalytic performance

Abstract

Catalytic oxidation of CH4 has been proved to be an attractive option for landfill gas (LFG) upgrading. However, coking of catalysts in catalytic LFG deoxygen has been clearly observed in industrial applications. In this regard, it is necessary to investigate whether coke deposition originates from CH4 or volatile organic compounds present in LFG, and the influence of coke deposition on catalytic performance. Herein, we evaluate the LFG deoxygen on Pt/γ-Al2O3 catalyst in simulated LFG (CH4, CO2, O2, N2) and its co-feed with representative volatile organic compounds, ethylbenzene, toluene, benzene and cyclohexane. The results show that the coking of the catalyst is originated from volatile organic compounds rather than CH4. The Pt/γ-Al2O3 catalyst does not deactivate during LFG deoxygen process, even significant amount of coke deposited, up to 18.15% (mass). Characterization analyses reveal that although coke deposition overall covers the catalyst surface, resulting in mesopores blockage and a reduced number of accessible Pt sites, however, the coke formed, H-rich carbonaceous components, behaves as counterpart for O2 elimination. Besides, the coke deposited is mainly filamentous. Thus, coke formation has little negative effect on the overall catalytic performance of Pt/γ-Al2O3 catalyst ultimately. The results obtained in this work are helpful for the rational design of robust Pt based catalysts for LFG deoxygen without undue attention to their coking properties, and also favor the innovation of more attractive purification scheme configurations.