Non-isothermal reduction of TeO2 by hydrogen: Integrated distributed-activation-energy-model (DAEM)-shrinking-core-model (SCM) kinetic modeling and enthalpy-entropy compensation analysis

Abstract

The non-isothermal reduction of TeO 2 (tellurium dioxide) by hydrogen (H 2 ) was investigated using thermal analysis (TG/DTG) techniques at multiple heating rates (1.0, 4.8, 9.6, and 18.8 K/min). Reaction kinetics were evaluated through an integrated Distributed Activation Energy Model (DAEM) coupled with a Shrinking Core Model (SCM), enabling accurate description of the multi-step gas-solid process. The results reveal a pronounced variation of the apparent activation energy with conversion, indicating a transition from surface-controlled to diffusion-limited regimes. Analysis of ln P vs . 1/ T relationship shows the significant deviation from linearity, confirming non-ideal Van't Hoff behavior and the presence of enthalpy-entropy compensation (EEC). The compensation temperature ( T comp ≈ 847 K) and Compensation Quality Factor ( CQF = 0.640) suggest a physically meaningful but non-isokinetic process. High-temperature regions exhibit elevated apparent enthalpy values, consistent with the product-layer diffusion control. The combined kinetic-thermodynamic approach provides comprehensive insight into the mechanism of TeO 2 reduction by hydrogen.