Synthesis of Ru/AC catalyst via chemical fluid deposition for selective hydrogenation of dioctyl phthalates in compressed CO2/H2O

Ruthenium catalysts supported on activated carbon (AC) were synthesized via chemical fluid deposition (CFD) using supercritical CO2 as the solvent. Uniformly dispersed Ru nanoparticles with an average size of similar to 3.7 nm were obtained. The performances of the prepared catalysts for hydrogenation of dioctyl phthalates (DOP) in water and CO2/H2O were investigated. The Ru/AC catalyst with 2.5 wt% Ru (Ru-2.5/AC) exhibited much better catalytic activity in water than in ethanol and hexane or in the solventless condition. The Ru2.5/AC catalyst showed a DOP conversion efficiency of 91.1% in water at 140 degrees C and 1000 psi of H-2 in 2 h, despite the poor solubility of DOP in water, while the DOP conversion efficiencies of the catalyst in ethanol and hexane were 33.1% and 10.0%, respectively. The enhanced activity of Ru-2.5/AC catalyst in water can be attributed to the "on -water" mechanism. Moreover, a highest DOP conversion of 99.7% with DEPPH selectivity of 100% could be achieved at 120 degrees C, 3 h, and 1500 psi of CO2 in H2O. The acidity of solvent and the interaction between the aromatic ring and the hydrogen proton generated from CO2/H2O played a key role in accelerating the adsorption of DOP on active Ru sites, resulting in an increase in the reaction rate. This work demonstrates the great potential of the combination of the low-cost highly efficient Ru-2.5/AC catalyst and green CO2/H2O solvent for the selective hydrogenation of aromatic compounds, including plasticizers.