Pyrolysis and catalytic pyrolysis of industrial lignins by TG-FTIR: Kinetics and products

• Sodium lignosulfonate was pyrolyzed under un-catalytic and catalytic conditions.
• The main pyrolysis process of SL was separated into three stages.
• HZSM-5 enhanced the mass loss and inhibited char formation.
• HZSM-5 promoted cracking reactions of oxygenated products.
• Aromatics, water, CO2 and CO are the main products.

Industrial lignins are by-products of the pulp and paper industry and generally used as a low-grade fuel. In this study, pyrolysis and catalytic pyrolysis (using HZSM-5, an aluminosilicate zeolite) of sodium lignosulfonate (SL) were carried out in a coupling of thermogravimetric analysis and Fourier transform infrared spectroscopy (TG-FTIR) using nitrogen. The reaction temperature was increased from 30 to 650 °C, while the heating rates were varied from 10 to 40 °C/min. The pyrolysis process could be divided into three parts. Kissinger's method had been used to carry out dynamics calculation concerning pyrolysis of SL in main pyrolysis. The kinetic parameters and reaction orders in the three pyrolysis stage were gained. The generated products for SL pyrolysis were water, CO, CO2, aromatics, alkenes and alkyls. The catalytic effect of HZSM-5 is obvious. It inhibited char formation of SL pyrolysis, and promoted the degradation of high molecular weight compounds to low molecular weight compounds, promoted cracking reactions of oxygenated products.