Understanding the Role of Coordinatively Unsaturated Al<sup>3+</sup> Sites on Nanoshaped Al<sub>2</sub>O<sub>3</sub> for Creating Uniform Ni–Cu Alloys for Selective Hydrogenation of Acetylene
Yuanfei Song, Shaoxia Weng, Xue Fan, Alan J. McCue, Lirong Zheng, Yufei He, Junting Feng, Yanan Liu, Dianqing Li
Abstract
In this work, we report a synthesis approach for catalyst preparation using shape-controlled Al 2 O 3 supports with enriched quantities of coordinatively unsaturated Al 3+ centers. These centers can then induce ordering in bimetallic catalysts, even with a simple impregnation strategy and this is shown to be beneficial for selective hydrogenation of acetylene. Interestingly, nanorod Al 2 O 3 induced a highly homogeneous and ordered Ni 1 Cu 1 nanoalloy, mainly attributed to the coordination effect of unsaturated Al 3+ sites that accelerate atomic diffusion and ordering (affirmed by molecular simulation). The as-obtained Ni–Cu/Al 2 O 3 -rod catalyst exhibited both satisfactory activity and ethylene selectivity of 86% under mild reaction conditions, which outperformed most of Ni-based catalysts reported to date. Through the combination of in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) studies and computational modeling by density functional theory, it was found that a di-σ-adsorption mode of acetylene on the ordered Ni 1 Cu 1 nanoalloy featuring alternating rows of Cu and Ni atoms played a key role in the improvement of selectivity.