Thermal and calorimetric evaluation of nanocatalysts for renewable fuel production

Nanomaterial heterogeneous catalysts are key components of the intensification of renewable fuel synthesis through processes such as transesterification and esterification for biodiesel production, owing to their large specific surface area, controlled basicity/acidity, and mass-transfer properties compared with traditional bulk catalysts. Since catalytic activity, thermal stability, sintering behavior, and reusability depend on the thermal behavior of the material, a thorough thermal analysis should be undertaken before proceeding toward nanocatalyst scale-up. In this study, a novel approach integrating thermal analysis and calorimetry of metal-oxide nanocatalysts (NiO, CaO, and ZnO) for biodiesel production is presented using thermogravimetry (TGA), differential thermal analysis (DTA), differential scanning calorimetry (DSC), and isothermal reaction calorimetry, together with Arrhenius-type kinetic studies of the transesterification reaction. The synthesis, calcination, and characterization of the nanocatalysts using XRD, FTIR, BET, TEM/SEM, TGA-DTA, and DSC are described, followed by evaluation of mass-loss characteristics, decomposition temperature, transition enthalpy, specific heat capacity, isothermal heat flow, activation energy, biodiesel yield, and reusability over seven reaction cycles. The key findings indicate that CaO exhibited the lowest apparent activation energy, the largest reaction enthalpy release, the highest biodiesel yield, and the highest reusability among the three nanocatalysts investigated. In contrast, ZnO showed the highest BET surface area but comparatively lower catalytic performance and reusability, demonstrating that surface area alone is insufficient to predict overall catalyst performance. These results demonstrate that the combined consideration of thermal stability, calorimetric behavior, kinetic parameters, surface characteristics, and reusability provides a more comprehensive basis for nanocatalyst screening and selection. Future studies should validate these relationships using experimentally measured datasets and extend the investigation to waste and high-free-fatty-acid feedstocks, alternative alcohols, and post-use structural and surface characterization to clarify catalyst deactivation mechanisms. The proposed integrated thermal–calorimetric framework provides practical design guidelines for evaluating and selecting durable metal-oxide nanocatalysts for renewable-fuel production.