The sulfur–iodine thermochemical water-splitting cycle is a promising route proposed for hydrogen production. The decomposition temperature remains a challenge in the process. Catalysts, such as Pd supported on Al₂O₃, are being considered to decrease reaction temperatures. However, little is known regarding the kinetic behavior of such systems. In this work, zinc sulfate thermal decomposition was studied through non-isothermal thermogravimetric analysis to understand the effect of a catalyst within the sulfur–iodine reaction system context. The findings of this analysis were also related to a thermodynamic assessment. It was observed that the presence of Pd/Al₂O₃ modified the reaction mechanism, possibly with some intermediate reactions that were suppressed or remarkably accelerated. The proposed model suggests that zinc sulfate transformation occurred in two sequential stages without the Pd-based material. Activation energy values of 238 and 368 kJ·mol⁻¹ were calculated. In the presence of Pd/Al₂O₃, an activation energy value of 204 kJ·mol⁻¹ was calculated, which is lower than observed previously.

The sulfur related thermochemical water-splitting cycles are an important class of chemical processes considered for hydrogen production. Recently, the magnesium sulfate thermal decomposition has been reported as a potential unit operation in one of these cycles. Therefore, some interest has been observed in the use of catalysts to lower the activation energy of such reactions. In this context, the present manuscript reports the thermodynamics and kinetics modeling results associated with this reaction system in the presence of a Pd catalyst supported over γ-Al2O3. The presence of such species is responsible for shifting the decomposition temperature to lower values in at least 100 °C. It was observed that the magnesium content is still oriented towards MgO formation. The obtained results indicate that the Pd/Al2O3 catalyst could be a good alternative in reducing the thermal decomposition temperature as its presence was responsible for diminishing the process activation energy from 368.2 to 258.8 kJ.mol−1.

This study investigated the kinetics of the reduction reaction of nitric oxide (NO) by carbon monoxide (CO), aiming to evaluate NOx emissions in automotive exhaust gases. Although the overall reaction leads to the formation of inert nitrogen gas (N₂), nitrous oxide (N₂O), a potent greenhouse gas, can arise as a byproduct, depending on the catalyst composition and operating conditions. The study demonstrates that light-off curves are an effective and practical method for determining the kinetic parameters and product distribution in the reduction of NO by CO over Pd/Al₂O₃. These curves provide results consistent with isothermal experiments, while requiring simpler and faster procedures. N₂O was identified as a reaction intermediate, formed in the partial conversion of NO and consumed as N₂ becomes the dominant product. Its formation occurs over a wide temperature range, which is especially relevant for cold start conditions in gasoline engines. The Pd/Al₂O₃ catalyst demonstrated high thermal stability and resistance to deactivation up to 500 °C. A first-order kinetic model successfully reproduced the main experimental trends, including the transient behavior of N₂O. Graphical Abstract The alternative text for this image may have been generated using AI.