Catalytic transformation of lignin to aromatic hydrocarbons over solid-acid catalyst: Effect of lignin sources and catalyst species

Catalytic pyrolysis of two lignin samples extracted from Chinese fir and rice straw was investigated by Pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS), concerning the effect of reaction temperatures (550–900 °C) and catalyst species (HZSM-5 (25), HZSM-5 (50), HZSM-5 (210), H-β and H-USY) on the production of specific aromatic hydrocarbons (such as benzene, toluene and xylene). The yield of specific aromatic hydrocarbons from catalytic pyrolysis of the two lignin samples with HZSM-5 (25) achieved the maximum value at 650 °C. Formation of p-xylene was remarkably promoted with the decreased Si/Al ratio of HZSM-5 over that of toluene. Production of o-xylene from two lignin samples under 650 °C was selectively enhanced by H-USY due to its compatible pore structure. HZSM-5 (25) with suitable distribution of acidic sites identified by NH3-TPD was estimated to be the potential commercial catalyst for production of toluene and p-xylene from catalytic pyrolysis of lignin. Yield of oligo-aromatic hydrocarbons (naphthalene and methylnaphthalene) from catalytic pyrolysis of Chinese fir lignin under 650 °C is remarkably higher than that from rice straw lignin possibly due to their different oxygen contents.