Regeneration of Aluminopalladium Catalyst for Hydrogenation Using Supercritical Fluid CO2-Extraction Process

Abstract

An experimental setup was designed for studying the solubility of a catalyst-deactivating compound – polyisoprene – in pure supercritical carbon dioxide (SC-CO2) and in SC-CO2 with a co-solvent (3,5 wt % chloroform). In pure SC-CO2, the crossover-type variations in the solubility was observed in isotherms t = 70, 100 and 120 °C at the pressure region between 15 and 34 MPa, and the pressure of ca. 19 MPA determined in the top crossover point. Addition of chloroform to SC-CO2 was shown to result in an average 2 to 2,5 times increase in the solubility. The process of supercritical fluid CO2-extraction regeneration of the aluminopalladium catalyst LD-265 for hydrogenation was studied. Dimethylsulfoxide and ethanol were used as co-solvents for SC-CO2. The maximal efficiency of the regeneration was observed at the co-solvent concentration of 5,5–6,5 wt %, dimethylsulfoxide being more effective co-solvent than ethanol. With the catalysts subjected to the SC-CO2 regeneration, the resulting diene and bromine numbers, as well as conversions of styrene and methylcyclopentadiene, meet the standards on catalytic systems for selective hydrogenation of diene hydrocarbons to benzene-toluene-xylene fractions.