Lignin Characterization and Catalytic Pyrolysis for Phenol-Rich Oil with TiO2-Based Catalysts

In this study, the chemical structure of corn straw lignin and the catalytic pyrolysis behavior at 350-650 degrees C in a fixed bed was investigated, with TiO2-based catalysts (load Cu, Fe, and Mo) respective to phenolic compounds production. It was found that beta-O-4 is the most frequent linkage in corn straw lignin, up to 89%. The highest selectivity (79%) and yield (21.17 mg/(g lignin)) of phenols was obtained at 450 degrees C for lignin pyrolysis. TiO2 addition enhanced the production of bio-oil with more phenols formed, and the selectivity of phenols reached 86%, with the yield up to 23.64 mg/(g lignin). With Cu or Fe loading, the yield and selectivity of phenols decreased, but the content of aromatic ketones increased obviously. But with Mo addition, the yield and selectivity of phenols increased apparently to 26.72 mg/(g lignin) and 89%, respectively, especially for monophenols and guaiacols. This suggests that the thermal catalytic activity of TiO2 can be further improved by doping a specific metal.