Upgrading Bioethanol to a High-Energy-Density Sustainable Fuel over a Novel Bimetallic Nanocomposite Catalyst

The present study reports an innovative bimetallic NiCuMgAlO composite catalyst with unique properties synthesized via a bioglycerol template-assisted coprecipitation method for the efficient conversion of ethanol to n-butanol, a promising “drop-in” replacement for gasoline. The simultaneous introduction of Ni and Cu into the MgAlO matrix in the presence of a bioglycerol template led to the development of key features in the resulting NiCuMgAlO material. These features include an optimal combination of acid–base dual sites, synergism between Cu and Ni, a Cu–Ni alloy structure, and unique textural properties referred to as honeycomb morphology, comprising three-dimensional hierarchical micro- and mesopores with both cylindrical and wedge-shaped geometries. This catalyst exhibited outstanding performance, achieving 52% ethanol conversion with 82% n-butanol selectivity at 250 °C, the highest values reported to date, to the best of our knowledge. The present study discovered that the optimal combination of acid–base dual sites, coupled with the synergistic interaction between Cu and Ni, and the Cu–Ni alloy structure formed within the NiCuMgAlO catalyst, are key factors in achieving the highest ethanol conversion. This is made possible by the simultaneous involvement of Ni and Cu in the MgAlO matrix, facilitated by the coprecipitation process, which significantly enhances the catalytic performance at relatively low temperatures. The unique textural properties of the NiCuMgAlO catalyst, including its honeycomb morphology with 3-dimensional pores in both cylindrical and wedged shapes, are a result of the special effect of the bioglycerol template. These characteristics play a crucial role in enabling shape-selective catalysis, which contributes to the high selectivity for n-butanol. The catalyst also showed a long time activity for 12 h in the upgrading of ethanol to n-butanol. Overall, this work demonstrates a more stable and efficient bimetallic NiCuMgAlO catalyst that is well-suited for the cascade conversion of ethanol to n-butanol, a high-energy-density sustainable fuel.