Effect of air introduction on filamentous coke during CO2 reforming of tar with core-shell catalysts

摘要

The coke accumulation is the main factor affecting the activity of nickel-based catalysts during the CO2 reforming of tar. In this work, toluene is chosen to study the influence of filamentous coke on the coke-forming mechanism of the Ni/La2O3 @SiO2 catalyst. Two methods are proposed to address the problem of reduced tar conversion of Ni/La2O3 @SiO2 due to coke deposition. The Ni/La2O3 @SiO2 is first modified with cobalt doping to improve the resistance to coke accumulation. The Ni8Co/La2O3 @SiO2 catalyst showed higher carbon conversion (50-75%) and hydrogen conversion (35-55%) than Ni/La2O3 @SiO2 within the 5 h tar reforming process. And the used Ni8Co/La2O3 @SiO2 catalysts had only 0.1 g/g of filamentous coke after reforming reaction. Next, air is intro-duced to oxidize the deposited coke to address the problem of coke accumulation affecting catalyst activity. An appropriate air flow rate could provide oxidation of the coke and prolong the reaction activity of the catalyst from 5 h to 10 h.