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.
The transformations of glucose over the Pt/C catalyst in a flow reactor in the temperature range 140–200°C at a pressure of 5.0 MPa have been studied. The main routes of glucose conversion in an aqueous phase in the presence of hydrogen, helium, or air have been considered. A product formation scheme depending on the reaction parameters has been proposed. At 140°C, glucose hydrogenation into sorbitol occurs with a selectivity of 77%. In an oxidizing atmosphere, glucose transforms into gluconic acid (with 73% selectivity at 140°C); here, the formation of sorbitol and mannitol (with a selectivity of 5–7% at 180–200°C) is also possible. Glucose transformation by-products, such as C3–C5 polyatomic alcohols, ketones, acids, and furfural derivatives, have been identified. The degree of glucose reforming in the aqueous solution with the formation of the gaseous products H2 and CO2 is no higher than 10% at 200°C.
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).
The conversion of isobutane-butenes mixtures on the H-form of ultrastable zeolite Y and sulfated zirconia under supercritical conditions at 150–160°C and 80 atm was studied. The isobutane/C4-olefins molar ratios (I/O) were 1.5, 14, and 28. In isobutane alkylation (I/O = 14 and 28), sulfated zirconia was more stable: at 150°C and 80 atm, the olefin conversion above 90% was retained for 5 h. Under the same conditions, the deactivation of the zeolite catalyst started after 1–2.5 h (depending on the initial I/O ratio). Selectivity for the formation of C8 hydrocarbons was 30–40%. An increase in the butene content of the initial mixture led to the domination of the dimerization of butenes over the alkylation of isobutane.