Solvent Effect in Liquid-Phase Selective Hydrogenation of Acetylene

Selective hydrogenation is used for removing acetylene from ethylene and producing ethylene from acetylene. It is particularly effective to carry out in a liquid phase when the feed has high C2H2 and CO concentrations. We conducted liquid-phase hydrogenation with methyl-amides as representative dipolar aprotic solvents and alkanes as representative nonpolar solvents to investigate the solvent effect. Hydrogenation in the methyl-amides gave similar products and selectivity–conversion relationships due to the similar structures of the methyl-amide solvents. These types of similarities were also observed with the alkanes. The reaction rate and selectivity are higher in the methyl-amide solvents compared to the alkanes. The activity in 1,3-dimethyl-3,4,5,6-tetrahydro-2(1H)-pyrimidinone is 1.35 times higher than that in the alkanes and N-methylpyrrolidone. The higher acetylene solubility in the methyl-amides resulted in higher acetylene hydrogenation rates.