Influence of TiO2 crystal structure on acrylonitrile decomposition over Ag/TiO2

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 N2 selectivity at low and high temperatures, respectively, whereas Ag/TiO2 composed of only rutile TiO2 exhibited medium N2 and high NOx selectivity at low and high temperatures, respectively. X-ray diffraction, X-ray photoelectron spectroscopy, and temperature-programmed reduction by H2 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.

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► Crystal phase of TiO2 affects product selectivity in acrylonitrile decomposition on Ag/TiO2.
► Ag/anatase–TiO2 shows high N2 selectivity, and Ag/rutile–TiO2 shows high NOx selectivity.
► Anatase and rutile phase tend to form ionic and metallic Ag, respectively.
► Ionic Ag catalyzes hydrolysis and metallic Ag catalyzes total oxidation.