Integrating kinetics, thermodynamics, and compensation effects of cellulose conversion with bimetallic oxygen carriers

Abstract

The chemical looping pyrolysis (CLP) of cellulose over NiFe₂O₄ was probed to elucidate the kinetic and thermodynamic mechanisms and compensation effects. The incorporation of oxygen carrier NiFe₂O₄ induced additional decomposition peaks, indicative of altered reaction pathways. Thermogravimetric/Fourier transform infrared spectroscopy (TG-FTIR) and thermogravimetry/gas chromatography-mass spectrometry (TG-GC/MS) analyses revealed a shift in major products from D-glucose in cellulose to furan derivatives and acetic acid in the cellulose/NiFe₂O₄ blend, demonstrating catalytic promotion of secondary conversion pathways. Model-free kinetic analyses showed a decrease in the apparent activation energies from 147.90 kJ mol⁻¹ to 93.99 kJ mol⁻¹ . Master-plots analysis indicated the dominant R3 reaction mechanism, with deviations toward the A2 model at α> 0.60. Thermodynamic parameters revealed a decrease in the enthalpy change from 142.66 kJ mol⁻¹ to 88.50 kJ mol⁻¹ and negative entropy change (−0.088 kJ mol⁻¹K⁻¹) for the blend, while Gibbs free energy change remained nearly constant (∼143.5 kJ mol⁻¹). Kinetic and enthalpy–entropy compensation effects were confirmed, with isokinetic temperatures of 596.50 K and 880.07 K for cellulose and the blend, and corresponding free energy of compensation of 143.81 and 140.05 kJ mol⁻¹ . These findings demonstrated that NiFe₂O₄ lowered energy barriers, reorganized transition states, and enhanced cellulose reactivity, providing a quantitative basis for optimizing CLP processes.