Toluene cracking and reforming over biomass-derived char under microwave heating

From the point of developing a new approach for the disposal of tar derived from biomass gasification, microwave-assisted tar cracking and reforming were performed over a biomass-derived char, with toluene as a model compound of tar aromatic substances. And the reaction rules, production distribution and changes of biomass char in process of toluene cracking and reforming were studied. The results indicated that biomass char had a catalytic effect on toluene cracking, and it was approved that microwave heating could favor toluene cracking. By analyzing the results, it was observed that toluene conversion and hydrogen selectivity were directly correlated to bed temperature in cracking reaction. Toluene cracking was optimized at 750℃, and the greatest toluene conversion and hydrogen selectivity were obtained, which were 92.77% and 91.94%, respectively. Afterwards, changes in toluene conversion and hydrogen selectivity were insignificant. It was further revealed that the introduction of CO2 could reform toluene into syngas production. At 700℃, the highest conversion rate of 92.03% was reached at CO2 flow rate of 80 mL/min, accompanied by a maximal syngas yiled rate of 91.30%. And increasing CO2 flow rate decreased the ratio of H2 to CO dramatically. The lowest ratio of 0.22 was obtained at CO2 flow rate of 120 mL/mm. The introduction of CO2 also brought about a loss of carbon in biomass char. And carbon loss was maximized to 5.42% at 700℃. At the same time, the depleted carbon was further converted into additional syngas production, which provided the highest contribution of 15.40% for total syngas production. Finally, it was demonstrated that an excess of CO2 could slow down the negative effect of carbon deposition on toluene conversion. ©, 2015, Chinese Society of Agricultural Machinery. All right reserved.