With increasing concern of environmental pollution and carbon emissions, energy production with renewable feedstocks especially biomass was become more attractive in recent decades. Liquid fuel, which was also called bio-oil, can be directly produced from biomass through fast pyrolysis. Nevertheless, the quality of the bio-oil generated from fast pyrolysis is low due to high oxygen and water content, low heating value and high viscosity. Therefore, upgrading of bio-oil is essential for its full utilization as a kind of renewable energy.
This work is aimed to study an innovative method for the bio-oil upgrading without external hydrogen that hydrogenating a bio-oil model compound with in-situ hydrogen generated from aqueous phase reforming of glycerol. The process was studied using guaiacol as the model compound of bio-oil and conducted in a batch stirred reactor. Initially, experiments of hydrogen production from glycerol reforming were performed at different operation conditions to maximize hydrogen yield. Then experiments were conducted to study hydrogenation of guaiacol with in-situ produced hydrogen from glycerol. The effect of the primary process variables was studied, and a potential reaction pathway was proposed followed by a catalysts screening in this process as a collaboration with Boreskov Institute of Catalysis (Novosibirsk, Russia).
For the experiments of glycerol reforming, it was found that the operating conditions had great influence on the hydrogen yield and selectivity of gas product. Optimum conditions were determined where the maximum hydrogen yield was obtained. In the experiments of hydrogenation of guaiacol, it was notable that hydrogenated aromatic compounds were formed in the absence of glycerol. It is believed that methanol produced from hydrolysis of guaiacol is the internal source of hydrogen. In addition, it was observed that guaiacol conversion and yield of organic soluble product increased with additional glycerol. Moreover, Ni/Al2O3 showed a better performance than promoted Ni based catalysts in terms of guaiacol conversion and organic soluble product yield. It is predicted that the capacity of hydrogen production of Ni based catalysts was inhibited by promotors.