Bimetallic NiCu catalyst with tailored d-band center derived from nanoflower-like LDHs for efficient and tunable selectivity of maleic anhydride hydrogenation

Abstract

The primary products of the direct hydrogenation of Maleic Anhydride (MA) are Succinic Anhydride (SAH) and γ-butyrolactone (GBL). Achieving selective synthesis of these products by regulating the composition, structure, and textural properties remains a focal point in the research field of maleic anhydride hydrogenation. Based on the characteristic of atomic level uniform distribution of cations of layered double hydroxides (LDHs), a highly loaded, highly dispersed and homogenized NiCu alloy bimetallic catalyst was synthesized using NiCuAl-LDHs as precursor. Compared with Ni/Al₂O₃ catalyst derived from NiAl-LDHs, the introduction of Cu can effectively improve the hydrogenation activity of C=C bonds while inhibiting the hydrogenolysis of C=O bonds. Under identical reaction conditions, the primary product of the Ni/Al₂O₃ catalyst was γ-butyrolactone (GBL) with a yield of 94.2 %, whereas the primary product of the NiCu_0.4/Al₂O₃ catalyst was Succinic Anhydride (SAH) with a yield of 90.5 %. The introduction of Cu resulted in the formation of a homogeneous NiCu alloy phase in the catalyst, which significantly influenced the adsorption configurations and adsorption energies of the reactants and intermediates. This effect can be attributed to the electronic interactions between Ni and Cu, which shift the d-band center of Ni away from the Fermi energy level, thereby facilitating the directed synthesis of Succinic Anhydride (SAH) and γ-butyrolactone (GBL). These findings were confirmed by various characterization techniques and DFT theoretical calculations. Future catalyst development in maleic anhydride hydrogenation will significantly benefit from the design approach and research ideas presented in this study.