The results of studies on the hydrogen accumulation, storage and release systems differing in the type of hydrogen interaction with the material (medium) used for hydrogen storage are analyzed. Published data on the use of polycyclic hydrocarbons as the basis for hydrogen storage in a chemically bound state are summarized. Substrate-structure-dependent differences between the mechanisms of heterogeneous catalytic hydrogenation reactions of mono- and polycyclic aromatic hydrocarbons with hydrogen storage capacity > 7 mass% and dehydrogenation of corresponding polycyclic naphthenes are discussed.The bibliography includes 188 references.

Reduction of CO₂ with hydrogen into CO was studied for the first time on alumina-supported Co and Fe catalysts under supercritical conditions with the goal to produce either CO or CH₄ as the target products. The extremely high selectivity towards methanation close to 100% was found for the Co/Al₂O₃ catalyst, whereas the Fe/Al₂O₃ system demonstrates a predominance of hydrogenation to CO with noticeable formation of ethane (up to 15%). The space–time yield can be increased by an order of magnitude by using the supercritical conditions as compared to the gas-phase reactions. Differences in the crystallographic phase features of Fe-containing catalysts cause the reverse water gas shift reaction to form carbon monoxide, whereas the reduced iron phases initiate the Fischer–Tropsch reaction to produce a mixture of hydrocarbons. Direct methanation occurs selectively on Co catalysts. No methanol formation was observed on the studied Fe- and Co-containing catalysts.

Hydrogenation of phenol in aqueous solutions on Pt-Ni/SiO₂, Pt-Ni-Cr/Al₂O₃, Pt/C, and Ru/C catalysts was studied at temperatures of 150–250 °C and pressures of 40–80 bar. The possibility of hydrogenation of hydrolysis lignin in an aqueous medium in the presence of a Ru/C catalyst is shown. The conversion of hydrolysis lignin and water-soluble sodium lignosulfonate occurs with the formation of a complex mixture of monomeric products: a number of phenols, products of their catalytic hydrogenation (cyclohexanol and cyclohexanone), and hydrogenolysis products (cyclic and aliphatic C₂–C₇ hydrocarbons).