Thermal behavior and kinetics of enzymatic hydrolysis lignin modified products

[Display omitted] •Utilizing different modification methods to modify lignin.•Applying phenolation to promote the grafting rate of flame-retardant (N, P) groups.•Thermodynamic stability of modified products changed obviously.•Kinetic analysis further elaborated the pyrolysis mechanism. Enzymatic hydrolysis lignin (EHL) used in this experiment was extracted from the bio-ethanol production residue by enzymatic hydrolysis method. With different modification methods, the purpose of this paper was to investigate the pyrolysis behavior and kinetics of lignin modified products via thermogravimetric analyzer coupled with Fourier transform infrared spectrometry (TG-FTIR). The emergence of specific functional groups detected by FTIR predicted that specific functional groups was grafted onto lignin successfully. Thermogravimetry/derivate thermogravimetry (TG/DTG) results showed that only the pyrolysis process of Lig-F (one of lignin modified products) was similar to that of Lig-C (purified lignin), and pyrolysis processes of other lignin-modified products had changed greatly. Moreover, pyrolysis properties of lignin modified products were different because of different grafting functional groups. In addition, the kinetics of Lig-F was conducted by two kinetic models (FWO: Flynn-Wall-Ozawa and KAS: Kissinger-Akahira-Sunose). Both methods obtained analogous values of activation energy, ranging from 157 kJ mol−1 to 219 kJ mol−1. This paper also gave a further evaluation of the application of lignin modified products in the field of flame retardants, which would better promote the multi-functional application of lignin.