Zn改性Ni/Al_(2)O_(3)催化剂的苯乙炔选择加氢性能

Zn-Modified Ni/Al_(2)O_(3)Catalyst for Enhanced Phenylacetylene Hydrogenation Performance

采用浸渍法制备了一系列不同Zn质量分数的ZnNi/Al_(2)O_(3)催化剂,并通过X射线粉末衍射(XRD)、氢气程序升温吸附(H_(2)-TPR)、X射线光电子能谱(XPS)等表征手段和密度泛函理论(DFT)计算模拟等考察了Zn的引入对催化剂的结构、性质以及苯乙炔选择加氢制苯乙烯反应性能的影响。结果表明,适量Zn的添加显著提升了Ni/Al_(2)O_(3)催化剂的苯乙炔选择加氢性能,与Ni/Al_(2)O_(3)催化剂相比,3%Zn-Ni/Al_(2)O_(3)催化剂上苯乙炔转化率由92.2%提高至96.8%,而苯乙烯的损失率则由4.3%下降至1.8%。催化剂的XRD和H_(2)-TPR表征结果显示,Zn掺杂到NiO晶格中增强了活性金属Ni与载体间的相互作用,有利于提高Ni的分散度;XPS表征结果表明,Zn表面的电子会向Ni转移,使Ni表面更加富电子。理论计算结果证实引入Zn后的催化剂表面容易形成稳定的Zn7Ni结构,Zn的表面电子向Ni迁移形成了富电子的Ni活性中心,对苯乙烯过渡加氢能垒为1.42 eV,高于选择加氢制苯乙烯的脱附能垒(0.55 eV),提高了Zn改性Ni/Al_(2)O_(3)催化剂的苯乙炔选择性加氢性能。

This study employed an impregnation method to prepare a series of ZnNi/Al_(2)O_(3)catalysts with varying Zn content.The catalysts were characterized using techniques such as X-ray powder diffraction(XRD),hydrogen temperature-programmed reduction(H_(2)-TPR),X-ray photoelectron spectroscopy(XPS),and density functional theory(DFT)calculations.The structural and property characterization aimed to investigate the impact of Zn introduction on the catalysts during the phenylacetylene selective hydrogenation to styrene.Experimental results revealed a significant enhancement in catalyst performance with the introduction of Zn,leading to an increase in the conversion rate of phenylacetylene selective hydrogenation to styrene from 92.2%to 96.8%.Characterization of the support and catalyst structure indicated that Zn doping into the NiO lattice substantially strengthened the interaction between the active metal Ni and the support,significantly improving Ni dispersion.Due to the facile segregation of Zn metal,the ZnNi alloy formed on the reduced catalyst surface altered the surface electronic structure of Ni metal.The migration of Zn surface electrons to Ni formed electron-rich Ni active centers,facilitating the phenylacetylene selective hydrogenation to styrene.Theoretical calculations indicated that the introduced Zn led to the formation of a stable Zn7Ni structure on the catalyst surface,resulting in a transition hydrogenation barrier for styrene of 1.42 eV,significantly higher than the desorption barrier for styrene in selective hydrogenation(0.55 eV).These findings elucidate the fundamental factors underlying the performance enhancement of Ni/Al_(2)O_(3)catalysts by the Zn component.