Catalytic conversion of toluene by modified biochar from oak

Abstract

To study the catalytic conversion effect of toluene (biomass gasification tar model compound) by oak char, a fixed-bed test system is employed to examine the conversion efficiency. The liquid phase products are analyzed by GC-MS. Oak char samples are analyzed by SEM-EDS, BET specific surface area analyzer, XRD and XPS. The results indicate that the toluene conversion efficiency does not exceed 58.43% at 600 or 700 °C, whereas it rises remarkably at 800 °C. The toluene conversion efficiency by Mn-OC (oak char modified by KMnO4) is 93.07%, which is much higher than that of other samples. The compositions of liquid phase products are affected by the modification method and temperature. They mainly compose of aromatic compounds. Among them, biphenyl derivatives and bibenzyl are the main intermediate products during the catalytic conversion of toluene. Inorganic salt particles are attached to the surface of Mn-OC and K-OC (oak char modified by KCl), promoting the biochar activity. The number of oxygen-containing functional groups and micropores, and the specific surface area (575.80 m2 g−1) of Mn-OC increase significantly, which is an important reason for improving the activity of biochar. The O contents in Mn-OC and K-OC are remarkably higher than those of other samples due to the C–O–K structure formed in oak char. Therefore, oak char modified by KMnO4 could be an excellent catalyst during the catalytic conversion of toluene.