Performance of Catalysts of Different Nature in Model Tar Component Decomposition

Abstract

Municipal solid waste constitutes one of the major challenges and concerns of our society. Disposal of waste material is potentially dangerous, harming both environment and mankind. In order to diminish negative effects of municipal solid waste, its thermal decomposition to valuable chemicals has been studied. The principal draw-back of thermal processes used for solid waste utilization as raw material is tar formation. In this study, low-cost catalysts of different origin were tested in the decomposition of a model component of tar originating from waste material pyrolysis/gasification. p-Xylene was selected as the model compound found in biomass decomposition products. Its decomposition was carried out in the presence of either tire pyrolysis char- or clay minerals-based catalysts. Tar-cracking activities of both catalyst types at varying experimental conditions were compared and related to the catalysts physical-chemical properties. In experiments, either empty reactor or reactor filled with 10 g of the catalyst was used; p-xylene mass flow was set to 2.58 g h−1 (50 μL min−1, room temperature), and decomposition temperature ranging from 750 °C to 850 °C was applied. Moreover, evolution of the output variables, p-xylene conversion and hydrogen content in the gas phase, with the reaction time was investigated. Catalysts’ properties were assessed based on nitrogen adsorption isotherms, thermogravimetric and elemental composition analyses. Amounts and composition of p-xylene catalytic decomposition products were evaluated using GC analysis of both gaseous phase and condensable products. Results showed the superiority of tire pyrolysis char catalyst over that based on clay minerals.