Wood liquefaction with phenol by microwave heating and FTIR evaluation
We examined wood liquefaction using phenol and mixed acid catalysts with microwave heating, and compared that with similar processes that use oil bath heating. The reaction time for microwave heating to achieve a residue content was one sixth, one eighteenth, and one twenty-fourth of that from oil bath heating, respectively, for phenol to wood (P/W) ratios of 2.5/1, 2/1 and 1.5/1. A low P/W ratio tended to result in carbonization of liquefied wood due to an insufficient amount of phenol and localized microwave superheating. Fourier transform infrared spectroscopic (FTIR) evaluation of the liquefied residue, showed that the liquefaction rates of wood components differed. Hemicellulose was most susceptible to liquefaction, crystalline cellulose was most recalcitrant, and guaiacyl units the most prone to re-condensation. From FTIR, the chemical components and substitution patterns of bonded phenol were similar for both methods.