Tuning cis-decalin Selectivity in Naphthalene Hydrogenation Over Carbon-supported Rhodium Catalyst Under Supercritical Carbon dioxide

Abstract

Catalytic hydrogenation of naphthalene to decalin was studied over a carbon-supported rhodium catalyst in supercritical carbon dioxide solvent at 333 K, and the results were compared with those in an organic solvent. cis-, trans-Decalin and tetralin were formed from the beginning of the reaction in supercritical carbon dioxide. Higher concentration of hydrogen in carbon dioxide solvent and on the active site, and also the suppression of desorption of partially hydrogenated tetralin molecules from the active site would be responsible for higher selectivity to cis-decalin in supercritical carbon dioxide than that in an organic solvent.

Selective hydrogenation of citral over Au-based bimetallic catalysts in supercritical carbon dioxide

“…As the CO 2 pressure increased, the selectivities to cis-and trans-4-tert-butylcyclohexanol decreased, whereas the selectivity to 4-tert-butylcyclohexanone increased due to the higher solubility of the intermediate product 4-tert-butylcyclohexene-1-ol at higher CO 2 pressures, resulting in its further hydrogenation to 4-tert-butylcyclohexanone [39]. The similar effect also appeared in hydrogenation of naphthalene and tetralin in scCO 2 [40][41][42]. In addition, the adsorption mode of the reactants on the surface of the catalysts can be tuned through changing CO 2 pressure, resulting in a variation in product distribution.…”

Toward green catalytic synthesis—Transition metal-catalyzed reactions in non-conventional media

“…Shirai and co-workers have found Ru/C to be a better catalyst than Rh/C for the reduction of biphenyl to bicyclohexyl in scCO 2 at a low temperature (50 • C), allowing for 100% conversion [89]. The same catalyst was also shown to be active for the selective reduction of 1-and 2-phenylethanols to 1-and 2-cyclohexylethanol [90] and for the formation of cis-decalin from the selective reduction of naphthalene or tetralin in scCO 2 [91]. In general, the higher concentration of H 2 in scCO 2 has been considered to be the reason for the improved reaction rates.…”

Heterogeneous Catalysis in Supercritical Media: 1. Carbon Dioxide

“…By increasing the H 2 partial pressure, selectivity in supercritical CO 2 increased significantly, compared to that in the organic solvent. This was attributed to an increased hydrogen concentration near the catalyst [76,77].…”