The catalytic decomposition of acrylonitrile over Ag supported on different crystal phases of TiO2 was studied. Ag/TiO2 containing anatase TiO2 exhibited high NH3 and N-2 selectivity at low and high temperatures, respectively, whereas Ag/TiO2 composed of only rutile TiO2 exhibited medium N-2 and high NO selectivity at low and high temperatures, respectively. X-ray diffraction, x-ray photoelectron spectroscopy, and temperature-programmed reduction by H-2 revealed that the anatase phase favors the formation of ionic Ag, whereas the rutile phase favors that of metallic Ag. We concluded that product selectivity in acrylonitrile decomposition was influenced by the oxidation state of Ag, which was in turn affected by the crystal phase of TiO2. (C) 2012 Elsevier B.V. All rights reserved.