CO2-assisted hydrogen recovery from isopropanol over Ni/CeO2 catalysts: Thermodynamic and kinetic insights

[EN] The difficulties and risks associated with the storage and transport of hydrogen are among the chief challenges for the development of a hydrogen economy. In this context, the use of hydrogen carriers such as the alcohols derived from biomass are deemed promising alternatives to safe storing and transportation. A route for recovering hydrogen from alcohols is their catalytic oxidation with soft oxidizing agents that avoid the combustion of the alcohol. Within this context, we analyze herein the catalytic oxidation of isopropanol with CO2. Particularly, we did a thermodynamic equilibrium analysis of the reaction and performed catalytic experiments over Ni/CeO2 catalysts of different metallic loadings. The results of the thermodynamic analysis showed the production of H2 and CH4 accompanied by coke between 100-400 degrees C, at atmospheric pressure. On the other hand, the catalytic tests showed that increasing the Ni loading of Ni/CeO2 enhances both isopropanol conversion and H2 production. Furthermore, CH4 formed for the catalyst with the highest Ni loading. Operando DRIFTS analysis suggested that Ni promotes the dehydrogenation of isopropanol to acetone. But, this penalizes the lifespan of the catalyst owing to the promotion of the formation of carbonaceous deposits. Meanwhile, the basic sites on CeO2 reduce CO2 to CO. This process mitigates acetone and propene formation whose further transformation contributes to coke production. Overall, the catalytic results indicated that the recovery of molecular hydrogen and methane from isopropanol in the presence of CO2 is governed by the competitive adsorption of isopropanol and CO2 on the catalyst surface.