Upgrading ethanol to n-butanol over highly dispersed Ni-MgAlO catalysts

- Ethanol was transformed to n-butanol over highly dispersed Ni-MgAlO catalysts.
- The selectivity for n-butanol reached 55.2% at 18.7% ethanol conversion.
- Metallic Ni sites promoted ethanol dehydrogenation and hydrogen spillover.
- Strong base sites and moderate acid sites were crucial for C-C coupling reactions.

Ethanol is widely used as a fuel blender for gasoline. However, it has a low energy content and blending ratio. The fuel quality can be improved by upgrading ethanol to high-energy-content alcohols such as n-butanol. Here, we synthesized high-carbon alcohols from ethanol over Ni-based catalysts in a fixed-bed reactor. The selectivities for n-butanol and C4-C8 alcohols reached 55.2% and 85%, respectively, at 18.7% ethanol conversion over the optimal catalyst, Ni4MgAlO, with an areal reaction rate of 62.6 μmol h−1 m−2 at 523 K. The effects of Ni promotion and acid-base site distributions of catalysts were investigated using various techniques. The results show that metallic Ni sites promoted ethanol dehydrogenation, and the released hydrogen spilled over the catalyst, leading to in situ hydrogenation of reaction intermediates. Strong basic and moderately acidic sites were needed for aldol condensation reactions. A reaction network was proposed based on product analysis under different conditions.

244