Research on Deoxygenation Pyrolysis of Larch Based on Microwave Heating

Aiming at problems such as low energy utilization efficiency and the high oxygen content of liquid products in the process of conventional biomass conversion to prepare liquid fuels, the deoxygenation pyrolysis technology route of larch based on microwave heating was proposed in this paper. Two kinds of calcium–iron composite oxygen carriers, including Ca2Fe2O5 with iron ore structure and CaFe2O4 with spinel structure, were successfully synthesized. The results showed that the selectivity of ideal products was improved under the action of single iron-based oxygen carriers; however, the deoxygenation effect was undesirable. Under the action of CaFe2O4, the selectivity of aromatics was increased to 27.17% and the selectivity of phenols was decreased to 36.46%, which mainly existed in the form of O1P with low oxygen content. The oxygen content of bio-oil was reduced to 27.70% and the calorific value was increased to 29.05 MJ/kg, thus leading to a great improvement in the quality of liquid products. After the pyrolysis reaction, the Fe2P3/2 XPS peak of CaFe2O4 shifted to a higher binding energy and was characterized as higher valence of iron oxide, which proved its “oxygen grabbing” capacity in microwave pyrolysis. The deoxygenation conversion of larch without an external hydrogen supply was achieved.