Production of Aryl Oxygen-Containing Compounds by the Pyrolysis of Bagasse Alkali Lignin Catalyzed by LaM_0.2Fe_0.8O₃ (M = Fe, Cu, Al, Ti)

A series of LaM_0.2Fe_0.8O₃ (M = Fe, Cu, Al, Ti) samples synthesized by the sol–gel method were used to catalyze the pyrolysis of bagasse alkali lignin (BAL) to produce aryl oxygen-containing compounds. The effects of doping metal ions in the B-site of LaFeO₃ were investigated by X-ray diffraction, scanning electron microscopy, Brunauer–Emmett–Teller, and X-ray photoelectron spectrometer. Furthermore, the catalytic pyrolysis performances of the perovskites were evaluated by thermogravimetric analysis and the fixed-bed microreactor, and the gaseous and liquid pyrolysis products were analyzed by GC and gas chromatography/mass spectrometry (GC/MS), respectively. The results indicated that the perovskites have a cubic crystal phase, porous structure, and large specific surface area. After doping Cu, Al, and Ti ions in the B-site of perovskites, the grain sizes were refined, the performance of catalyzing BAL pyrolysis was improved, and the yields of liquid pyrolysis products increased by 24.1–39.1%. The selectivities of CO₂ and CO in gaseous products decreased by 5.8–16.3 and 26.0–34.8%, respectively, which resulted from the inhibition of decarboxylation and decarbonylation. The total selectivities of target products, i.e., aryl oxygen-containing compounds (including phenolics, guaiacols, syringols, and phenylates) obtained from BAL pyrolysis catalyzed using perovskites were all greater than 74 wt %, which was higher than that obtained from the pyrolysis of pure BAL (62 wt %) in the absence of catalyst. After 5 cycles of redox reaction, the perovskite still showed a well-maintained structural and catalytic stability.