稀土对Ni-ZnO基脱硫催化剂反应性能的影响机制

Mechanism of Rare Earth Metal's Effect on the Performance of Ni-ZnO Desulfurization Catalyst

为考察La、Ce对还原后的Ni-ZnO催化剂电子结构的调变作用,模拟工业条件对催化剂进行高压还原,对还原后的催化剂进行Ar离子刻蚀-XPS表征。结果表明,还原后的催化剂中以Ni 0为主,La不会被还原,Ce^(4+)被还原为Ce^(3+)。La^(3+)和Ce^(3+)在催化剂外表面富集,并与Ni之间存在相互作用,电子由Ni偏向La^(3+)和Ce^(3+),导致Ni的电子不饱和度增加,从而增强其对硫化物中孤对电子的吸附,使Ni-ZnO催化剂脱硫活性增强。但由于La、Ce与Ni-ZnO的电子配位结构存在明显差别,使用Ce改性的催化剂,在相同脱硫率下,汽油产品辛烷值较高;特别是当催化剂中Ce的质量分数为3.0%时,汽油的平均硫质量分数仅为5.1μg/g,与原料相比,研究法辛烷值增加0.3个单位。

In order to investigate the modulation effects of Ce and La on the electronic structure of the reduced Ni-ZnO catalyst, the high-pressure reduction of the catalyst was carried out by simulating the industrial conditions, and the Ar ion etching-XPS characterization of the catalyst was carried out. The results showed that after the reduction of the catalyst, the main species of Ni is Ni^0,the La could not be reduced, and the Ce^4＋ was reduced to Ce^3＋. La^3＋ and Ce^3＋ enriched on the outer surface of the catalysts. The interaction between La^3＋ and Ce^3＋ with Ni^0 was detected and the electron is biased by La^3＋ or Ce^3＋ , which leads to the increase of Ni＇s electron instauration. The increase of the electron instauration of Ni can enhance the adsorption of the lone pair electrons in the thiophenic sulfides, which in turn enhances the desulfurization activity of Ni-ZnO catalysts. But because of the obvious difference of electron structure between La^3＋ or Ce^3＋ modified Ni-ZnO catalysts, using Ce modified catalyst could yield higher octane number gasoline under the same desulfurization conversion; this is especially so with the Ce mass fraction of 3% , where the average sulfur mass fraction of gasoline product was only 5. 1 μg/g and the RON increased 0. 3 compared with feed.