(583cg) Catalytic Hydrodeoxygenation of Guaiacol

Catalytic hydrodeoxygenation (HDO) is a rapidly developing technology for oxygen removal from bio-oils obtained from pyrolysis of biomass. While various catalysts have been studied for this purpose, due to the presence of more than 400 oxygenated organic compounds in bio-oil, the catalytic activity and reaction pathways for the HDO process are not well understood. In this context, it is important to select model compounds which represent the raw bio-oil. In this study, Guaiacol, a phenol derived compound produced by the thermal degradation of lignin, is selected as a model compound because it is among the major components of bio-oil and, in addition, is thermally unstable and leads to coke formation – a feature of bio-oil as well. Conducted in a fixed-bed reactor at atmospheric pressure, this work studied the performance of four carbon supported noble metal catalysts (Ru, Pt, Pd and Rh) on the guaiacol HDO reaction process. The screening criteria were as follows: (1) High degree of deoxygenation, (2) Low hydrogen consumption, (3) High carbon recovery in liquid phase, and (4) Long catalyst lifetime. Our results showed that, among the tested catalysts, Ru and Pt had higher deoxygenation activity. Pt/C showed the most promising activity: at its optimum reaction temperature (300^oC), guaiacol conversion was above 90%, the carbon recovery in liquid product stabilized at above 70% after 3 hours, and no sign of catalyst deactivation was observed in 10 hours. Ru/C catalyst, although provided relatively high guaiacol conversion and liquid yield at the initial stage, had noticeable amount of deactivation within 5 hours. Based on analysis of both the liquid and the gas phase products, the reaction pathways were proposed for both catalysts. In addition, the cause of catalyst deactivation (particularly for Ru/C) was investigated through catalyst characterization.