Support Effect of Palladium Catalysts for Naphthalene Hydrogenation as Model Hydrogen Storage Process Using Low Grade Hydrogen Containing CO

The organic hydride method utilizes the reversible hydrogenation-dehydrogenation cycle of aromatic hydrocarbons for the storage and transportation of hydrogen. If low-grade hydrogen containing CO impurity is used in the hydrogenation process, storage and purification of hydrogen can be attained simultaneously. This study investigated the effect of Pd on SiO2, Al2O3 and SiO2-Al2O3 catalyst supports on the hydrogenation of naphthalene in the presence of CO. Pd/Al2O3 catalyst had the highest activity for hydrogenation using pure hydrogen. However, Pd/SiO2-Al2O3 showed the highest activity using 2%CO/H2. All catalysts allowed only the hydrogenation of naphthalene to proceed and no CO hydrogenation was observed. CO probe FT-IR spectra were observed at elevated temperatures. Desorption behavior was dependent on the catalysts and, especially on the lower wavenumber side, strongly adsorbed CO changed more significantly with the catalyst. CO desorption behavior of Pd/SiO2-Al2O3 indicated weak Pd-CO bond. Deconvolution of the IR spectra showed that the acidity of the SiO2-Al2O3 support decreased the electron density of Pd, resulting in weakening of the Pd-CO bond, which promoted the high hydrogenation activity in the presence of CO.