Solvent-Free Dehydrogenation of Decahydroquinoline over Palladium Nanoparticles Supported on Modified Ceria-Based Structures

Hydrogen storage and transportation technologies based on liquid organic hydrogen carriers (LOHCs) are of high research interest. The next generation of LOHCs with a higher hydrogen capacity and lower dehydrogenation temperature is required, and the decahydroquinoline/quinoline (DHQ/Q) system is among promising LOHCs. The catalysts comprising palladium nanoparticles supported on the synthesized high-surface area materials (CeO2, CeO2-ZrO2 mixed oxide, and Ce0.75Zr0.25O2), as well as reverse CeO2/Pd/oxide catalysts were tested in solvent-free dehydrogenation of DHQ at a high DHQ:Pd molar ratio, with DHQ being investigated as a hydrogen-storage source. The oxide-supported Pd nanoparticles were synthesized via the deposition–precipitation of Pd poly-hydroxo complexes, while a redox method was used to prepare the reverse catalysts. The highest hydrogen yields of 45% and 55% with the DHQ conversions of 61% and 76% at molar ratios DHQ:Pd of 1000 and 500, respectively, have been reached over the Pd/Ce0.75Zr0.25O2 catalyst at 220 °C, which results in hydrogen production exceeding that of other known catalysts studied in solvent-free DHQ dehydrogenation. The challenges and prospects for further catalyst development are discussed.