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Okorn Mekasuwandumrong Nitikon Wongwaranon Joongjai Panpranot Piyasan Praserthdam 《Materials Chemistry and Physics》2008,111(2-3):431-437
In the present study, Ni-modified α-Al2O3 with Ni/Al ratios of 0.3 and 0.5 were prepared by sol–gel and solvothermal method and then were impregnated with 0.3 wt.% Pd. Due to different crystallization mechanism of the two preparation methods used, addition of nickel during preparation of α-Al2O3 resulted in various species such as NiAl2O4, mixed phases between NiAl2O4 and α-Al2O3, and mixed phases between NiAl2O4 and NiO. As revealed by NH3-temperature programmed desorption, formation of NiAl2O4 drastically reduced acidity of alumina, hence lower amounts of coke deposited during acetylene hydrogenation was found for the Ni-modified α-Al2O3 supported catalysts. For any given method, ethylene selectivity was improved in the order of Pd/Ni–Al2O3-0.5 > Pd/Ni–Al2O3-0.3 > Pd/Ni–Al2O3-0 Pd/α–Al2O3-commercial. When comparing the samples prepared by different techniques, the sol–gel-made samples showed better performances than the solvothermal-derived ones. 相似文献
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Nitikon Wongwaranon Okorn Mekasuwandumrong Piyasan Praserthdam Joongjai Panpranot 《Catalysis Today》2008,131(1-4):553
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 ≈ Pd/α-Al2O3–sol–gel > Pd/α-Al2O3-solvothermal Pd/α-Al2O3-commerical. As revealed by NH3 temperature program desorption 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. 相似文献
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