The promotion effects of alkaline earth metals (Mg, Ca, Sr, Ba) on the catalytic property of the Cu/SiO2 catalyst for the gas phase dehydrogenation of 1,4-butanediol were investigated. The addition of Ca, Sr or Ba to the Cu/SiO2 catalyst resulted in the improvements of the catalytic activity and the gamma-butyrolactone selectivity, and the Cu-Ba/SiO2 catalyst gave 99.6% yield of gamma-butyrolactone even after 900 h running. The catalysts were prepared by co-impregnation and characterized by N-2 physisorption, X-ray diffraction (XRD), SEM, TEM, H-2-temperature programmed reduction (H-2-TPR), N2O-decomposition, ammonia temperature-programmed desorption (NH3-TPD), CO2-TPD, XPS, and FTIR spectroscopy of adsorbed pyridine and CO. On the base of the experimental results, two types of copper species on the reduced catalyst were proposed. The Cu-0 account for the dehydrogenation of 1,4-butanediol, while the electropositive copper species (Cu+) is suggested to be the strong Lewis acid site to catalyze side reactions. The selectivity of gamma-butyrolactone was increased with the increasing of the Cu-0/Cu+ ratio, and the yield of gamma-butyrolactone was increased with copper surface area. The main byproduct 2,3-dihydrofuran may be formed from 1,4-butanediol by the metal/acid-base concerted catalysis. (C) 2012 Elsevier B.V. All rights reserved.