Enhanced acetylene semi-hydrogenation on a subsurface carbon tailored Ni–Ga intermetallic catalyst

Abstract

Tailoring the active sites to promote the formation of the target product is of great importance for selective hydrogenations catalyzed by non-noble metals but remains challenging. Herein, we propose to employ carbon atoms to be incorporated into the Ni₃Ga intermetallic with partially isolated Ni sites aiming to enhance the catalytic performances for acetylene semi-hydrogenation. The incorporation of carbon atoms into the lattice of the Ni₃Ga intermetallic is achieved by thermal processing of the Ni₃Ga intermetallic catalyst in an acetylene atmosphere. The processed catalyst is proven to show the typical Ni₃GaC_0.5 phase by multiple characterization techniques including atomic-resolution electron microscopy and X-ray absorption spectroscopy. The presence of subsurface carbon in the Ni₃GaC_0.5 catalyst is experimentally and theoretically demonstrated to synergize with Ga sites for modifying the electronic structures of Ni via obvious hybridization of Ni 3d with Ga 2p and C 2p orbitals. The performance tests show that the Ni₃GaC_0.5 catalyst delivers high ethylene selectivity, up to ca. 90% at full conversion of acetylene, which outperforms the referred Ni and Ni₃Ga catalysts. The excellent selectivity to ethylene is rationalized by theoretical calculations, which point out that the desorption of ethylene from the Ni₃GaC_0.5 catalyst is kinetically more favourable than its hydrogenation to ethane. In addition, the stability of the Ni₃GaC_0.5 catalyst is also enhanced against the Ni and Ni₃Ga catalysts due to the suppressed formation of C₄ products.