Abstract
Microwave-assisted catalytic solvolysis of lignin in formic acid was studied concerning the addition of HUSY catalysts modified by oxalic acid. Characteristics of the modified catalysts were examined by XRD, NH3-TPD and BET. The highest yield of liquid product was achieved as 88.28 wt% (aromatic monomer fraction as bio-oil 1 of 15.36% and oligomer fraction as bio-oil 2 of 67.52%) with the addition of HUSY modified by 0.2 mol/L oxalic acid (HUSY-0.2 M). The production of aromatic monomers in bio-oil 1 identified by GC/MS was enhanced with the addition of HUSY catalysts regardless of acidic treatment, and achieved the maximum value for HUSY-0.2 M experiment. Aromatic oligomers with molecular weight of 328, 342, 358, 378, 394, 424 and 454 were characterized by Matrix-Assisted Laser Desorption/Ionization Time-of-Flight Mass Spectrometry (MALDI-TOF MS) analysis. Formation of almost all identified oligomers was promoted with catalytic experiments with HUSYs except that of 328, extent of which is significantly determined by the pore size, Si/Al ratio and acidic site distribution of the modified catalysts.