The non-isothermal thermal degradation behavior of raw lignin and Cu-impregnated lignin was investigated by thermogravimetric analysis at heating rates of 10, 15, 20, and 25 °C min⁻1. Kinetic parameters were determined using Friedman, Flynn–Wall–Ozawa (FWO), Kissinger–Akahira–Sunose (KAS), Starink, and Kissinger methods, together with thermodynamic analysis. In both samples, the activation energy (<InlineEquation ID="IEq1"> <EquationSource Format="TEX">${E}_{\upalpha }$</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mi>E</mi> <mi mathvariant="normal">α</mi> </msub> </math></EquationSource> </InlineEquation>) varied significantly with conversion, confirming that lignin degradation proceeds through a multistep and kinetically heterogeneous pathway. For raw lignin, the average <InlineEquation ID="IEq2"> <EquationSource Format="TEX">${E}_{\upalpha }$</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mi>E</mi> <mi mathvariant="normal">α</mi> </msub> </math></EquationSource> </InlineEquation> values obtained by Friedman, FWO, KAS, and Starink methods were 210.95, 220.83, 206.43, and 207.17 kJ mol⁻1, respectively, whereas the corresponding values for Cu-impregnated lignin were 85.32, 155.00, 125.64, and 135.07 kJ mol⁻1. The Friedman method provided comparatively more stable conversion-dependent trends, while the integral methods showed greater deviations at selected conversion levels. Thermodynamic analysis showed positive <InlineEquation ID="IEq3"> <EquationSource Format="TEX">$\Delta H$</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi mathvariant="normal">Δ</mi> <mi>H</mi> </mrow> </math></EquationSource> </InlineEquation> and <InlineEquation ID="IEq4"> <EquationSource Format="TEX">$\Delta G$</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi mathvariant="normal">Δ</mi> <mi>G</mi> </mrow> </math></EquationSource> </InlineEquation> values, indicating that lignin degradation is endothermic and non-spontaneous, requiring external heat input. Overall, Cu-impregnation modified the apparent degradation behavior of lignin and influenced its conversion-dependent kinetic and thermodynamic characteristics under non-isothermal conditions.

Pyrolytic degradation of lignin via in situ copper catalyst: kinetic modeling and analysis

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2026年7月3日

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Ankit Kumar

摘要

The non-isothermal thermal degradation behavior of raw lignin and Cu-impregnated lignin was investigated by thermogravimetric analysis at heating rates of 10, 15, 20, and 25 °C min⁻¹. Kinetic parameters were determined using Friedman, Flynn–Wall–Ozawa (FWO), Kissinger–Akahira–Sunose (KAS), Starink, and Kissinger methods, together with thermodynamic analysis. In both samples, the activation energy ( ${E}_{\upalpha }$ $E_{α}$ ) varied significantly with conversion, confirming that lignin degradation proceeds through a multistep and kinetically heterogeneous pathway. For raw lignin, the average ${E}_{\upalpha }$ $E_{α}$ values obtained by Friedman, FWO, KAS, and Starink methods were 210.95, 220.83, 206.43, and 207.17 kJ mol⁻¹, respectively, whereas the corresponding values for Cu-impregnated lignin were 85.32, 155.00, 125.64, and 135.07 kJ mol⁻¹. The Friedman method provided comparatively more stable conversion-dependent trends, while the integral methods showed greater deviations at selected conversion levels. Thermodynamic analysis showed positive $\Delta H$ $Δ H$ and $\Delta G$ $Δ G$ values, indicating that lignin degradation is endothermic and non-spontaneous, requiring external heat input. Overall, Cu-impregnation modified the apparent degradation behavior of lignin and influenced its conversion-dependent kinetic and thermodynamic characteristics under non-isothermal conditions.