Selective conversion of alkali lignin mediated by oxygen carrier CoFe2O4: Insights into kinetic, activation thermodynamic, and product distribution

The valorization of alkali lignin, an abundant by-product of the pulp and paper industry, is crucial for advancing circular bioeconomy goals. In the present study, its chemical looping pyrolysis (CLP) using CoFe 2 O 4 as an oxygen carrier was studied. Thermogravimetric analysis revealed that the incorporation of CoFe 2 O 4 accelerated lignin decomposition, with peak temperatures declining from 466-493°C to 399-442°C. Fourier transform infrared spectrometry and gas chromatography/mass spectrometry analyses showed a shift in product distribution, with relative abundance of acetone increasing from 14% to 56.34%, while phenolic compounds significantly decreased. The activation energies decreased from an average of 245.39 kJ mol −1 for alkali lignin to 174.93 kJ mol −1 for lignin/CoFe 2 O 4 blend. Linear lnA versus E a correlation was observed and isokinetic temperatures were found to be 967.34 K and 942.99 K, respectively, supporting the appropriateness of A2 model for lignin conversion and F2 mechanism for the CLP process. Thermodynamic analysis showed a decrease in Gibbs free energy from 175.36 to 159.90 kJ mol −1 , indicating enhanced thermodynamic favorability. Additionally, compensation effect analysis revealed compensation temperatures of 740.21 K for lignin and 681.96 K for the blend, confirming a consistent thermodynamic mechanism. These findings underscored the potential of CoFe 2 O 4 to enhance the selectivity of biomass pyrolysis, offering promising prospects for sustainable biofuel and bio-based chemical production.