Hydrogenolysis of glycerol to propylene glycol was performed using nickel, palladium, platinum, copper, and copper-chromite catalysts. The effects of temperature. hydrogen pressure, initial water content, choice of catalyst, catalyst reduction temperature, and the amount of catalyst were evaluated. At temperatures above 200 degrees C and hydrogen pressure of 200 psi, the selectivity to propylene glycol decreased due to excessive hydrogenolysis of the propylene glycol. At 200 psi and 200 degrees C the pressures and temperaures were significantly lower than those reported in the literature while maintaining high selectivities and good conversions. The yield of propylene glycol increased with decreasing water content. A new reaction pathway for converting glycerol to propylene glycol via an intermediate was validated by isolating the acetol intermediate. (c) 2004 Elsevier B.V. All rights reserved.