Production of aromatic monomers from catalytic pyrolysis of black-liquor lignin

• Fast pyrolysis of lignin with and without HZSM-5 was investigated by Py–GC/MS from 550 to 900 °C.
• Production of aromatic monomers was significantly changed by HZSM-5 with Si/Al ratio of 25, 50 and 210, H-β and H-USY.
• Selectivity of aromatic monomer formation was determined by pore size and Si/Al ratio of the catalysts.

Lignin, mostly existing in forms of solid residue from pulping process of biomass, has been intensively investigated as a potential feedstock for producing high-value chemicals. In this work, lignin precipitated from the acidified black liquor was pyrolyzed under different temperatures (550, 650, 800 and 900 °C) using the analytical pyrolysis technology coupled with GC/MS (Py–GC/MS). The experiments in absence and presence of five solid zeolite catalysts (HZSM-5(25), HZSM-5(50), HZSM-5(210), H-β and H-USY) were carried out, in order to identify the optimal reaction temperature and the best catalyst for producing aromatic monomers (such as guaiacol, phenol, benzene, toluene, etc) from lignin. HZSM-5(25) played an important role in promoting the yield of aromatic monomers from lignin under 650 °C, while H-USY enhanced the formation of aromatic hydrocarbons such as benzene, toluene and xylene.