Comparative study about catalytic liquefaction of alkali lignin to aromatics by HZSM-5 in sub- and supercritical ethanol

In this paper, HZSM-5 catalysts were first combined with sub-and supercritical ethanol (scEtOH) in alkali lignin catalytic liquefaction to produce bio-oil, and the synergistic effect of different reaction parameters (temperature, catalytic content, and reaction time) on conversion as well as product yields (bio-oil, solid residue, and aromatic compounds) was systematically studied. Gas chromatography mass spectrometry (GC-MS) and Fourier transform infrared spectroscopy analyses were carried out to evaluate the composition of main products. Treatment of alkali lignin with 10% HZSM-5 catalyst in scEtOH at 360 degrees C for 90 min resulted in the highest bio-oil yield of 53.81 wt. %. It has also been confirmed that a combination of HZSM-5 catalyst in subcritical ethanol is beneficial for saving the reaction time and inhibitation of repolymerization reaction. On the basis of GC-MS analysis, the combination of HZSM-5 catalysts and scEtOH resulted in the highest relative content of total aromatic compounds, reaching 71.61% at 280 degrees C. The most abundant monomers produced in the identical liquefaction are phenols and aromatic hydrocarbons. Published by AIP Publishing.