The influence of the acidity of HZSM5(X) (X = SiO2/Al2O3 ratios) on the activity of Ru catalysts and product selectivity (particularly during the formation of methane by-products) in glycerol hydrogenolysis was investigated. The catalyst systems were Ru/Al2O3 (or Ru/SiO2)+ HZSM5(X) (here, HZSM5(X) were used as additives) and supported Ru/HZSM5(X) catalysts. The reaction data revealed that adding HZSM5(X) to a Ru/Al2O3 (or Ru/SiO2)-catalyzed glycerol hydrogenolysis reaction increased the conversion of glycerol, but CH4 formation also increased. The characterization results revealed that when Ru was supported on HZSM5(X), the acid amount and strength of the Ru/HZSM5(X) catalyst decreased. As the ratio of SiO2/Al2O3 to HZSM5(X) decreased, the acidity of HZSM5(X) increased and the conversion of glycerol over Ru/HZSM5(X) catalysts increased; however, the selectivity to specific products (propanediols, ethylene glycol) decreased, while the selectivity to CH4 increased. The acidity of HZSM5(X) might increase the ability of Ru to cleave C C bonds and consequently degrade glycerol. (C) 2013 Elsevier B.V. All rights reserved.