Pyrolysis characteristics, gas products, volatiles, and thermo–kinetics of industrial lignin via TG/DTG–FTIR/MS and in–situ Py–PI–TOF/MS

The lignosulfonates and de–alkalized lignin pyrolysis characteristics were evaluated by using TG/DTG–FTIR/MS and in–situ Py–PI–TOF/MS. TG/DTG experiments showed that lignin sample pyrolysis proceeded in three stages from 303.15 to 1173.15 K, and the thermographs shifted to higher temperatures with increasing heating rate. Gases MS analysis showed that the pyrolysis of sodium lignosulfonate produced more CH4 and CO2 than the pyrolysis products of calcium lignosulfonate and de–alkalized lignin. The escape temperature of volatile matter in the lignin samples were basically consistent with the order of its organic content, but there were obvious differences in product composition. The escape peak temperature of olefins, aromatics, monophenols, and bisphenols showed a decline trend with the increase of substituent carbon number. The sample pyrolysis thermo–kinetics was estimated by Coats–Redfern, FWO, KAS, and integral Master–plots methods. The activation energies were 66.74–678.20 kJ mol−1 (calcium lignosulfonate) > 32.24–598.38 kJ mol−1 (sodium lignosulfonate) > 44.27–265.69 kJ mol−1 (de–alkalized lignin). The most potential kinetic models were not all consistent with the standard curves for the stages of sample pyrolysis. This study provides theoretical and practical guidance for solving the engineering problems of lignin wastes pyrolysis in papermaking wastewater.