Performance of Pd catalysts supported on nanocrystalline α-Al2O3 and Ni-modified α-Al2O3 in selective hydrogenation of acetylene

摘要

Nanocrystalline α-Al2O3 and Ni-modified α-Al2O3 have been prepared by sol-gel and solvothermal methods and employed as supports for Pd catalysts. Regardless of the preparation method used, NiAl2O4 spinel was formed on the Ni-modified α-Al2O3 after calcination at 1150 °C. However, an addition of NiO peaks was also observed by X-ray diffraction for the solvothermal-made Ni-modified α-Al2O3 powder. Catalytic performances of the Pd catalysts supported on these nanocrystalline α-Al2O3 and Ni-modified α-Al2O3 in selective hydrogenation of acetylene were found to be superior to those of the commercial α-Al2O3 supported one. Ethylene selectivities were improved in the order: Pd/Ni-modified α-Al2O3-sol-gel > Pd/Ni-modified α-Al2O3-solvothermal approx = Pd/α-Al2O3-sol-gel > Pd/α-Al2O3-solvothermal Pd/α-Al2O3-commerical. As revealed by NH3 temperature program desorplion studies, incorporation of Ni atoms in α-Al2O3 resulted in a significant decrease of acid sites on the alumina supports. Moreover, XPS revealed a shift of Pd 3d binding energy for Pd catalyst supported on Ni-modified α-Al2O3-sol-gel where only NiAl2O4 was formed, suggesting that the electronic properties of Pd may be modified.