Effect of support materials on Ag catalysts used for acrylonitrile decomposition

The effect of the support material on the Ag-catalyzed decomposition of acrylonitrile (AN) to form N-2 was studied for catalyst systems of Ag-ZSM-5, Ag/Al2O3, Ag/TiO2, Ag/SiO2, Ag/MgO, and Ag/ZrO2. Ag/TiO2 and Ag/SiO2 exhibited high AN conversion with high N-2 selectivity. X-ray diffraction, ultraviolet-visible spectroscopy, and H-2 temperature-programmed reduction revealed that both metallic and oxidized Ag species were present on TiO2 and SiO2. On the basis of diffuse reflectance infrared Fourier transform spectroscopy measurements, NH3 appeared to be formed by hydrolysis of AN, and this hydrolysis was enhanced by the presence of oxidized Ag species in the catalysts. The high AN decomposition activity was due to the presence of both oxidized and metallic Ag species, which promoted the hydrolysis of AN to form NH3 and the subsequent oxidation of NH3 to N-2, respectively. (C) 2008 Elsevier Inc. All rights reserved.