Iso-butanol production as a sustainable chemical from renewable methanol/ethanol upgrading using Ni/Cu-Al hydrotalcite-derived catalysts under mild conditions

Iso-butanol (i-BuOH) is a high-value bio-derived alcohol with significant potential as a renewable fuel and chemical intermediate. Sustainable production of i-BuOH is made possible by the Guerbet reaction, which presents a viable pathway for the selective conversion of ethanol into higher alcohols. In this work, we examine the catalytic performance of various Ni/Cu-Al hydrotalcite-derived catalysts for the synthesis of i-BuOH from a methanol/ethanol mixture. Via Guerbet reaction, the mixture of methanol/ethanol mainly converts into i-BuOH and small amounts of 1-propanol, 2-methyl-butanol, and 2-methyl-pentanol. The experiment with a 5.0 wt% loading of Ni10/2Cu-Al catalyst at 185 °C, 6 bar N2 and 4 h reaction time exhibits exceptional activity, producing 100% selectivity toward higher alcohols (C3C6) with 156.4 mmol/L i-BuOH (85.8% selectivity), 11.4% ethanol conversion, and space-time yield of 7.6 mmol.g-1.h-1, respectively. The catalyst's active sites of Ni and Cu species, which encourage the dehydrogenation/re-hydrogenation, and formation of C–C bonds and improve the efficiency of the methanol/ethanol coupling process, are responsible for its exceptional performance. Moreover, the Cu-Al hydrotalcite-derived structure offers stable and adjustable support, promoting selective product generation and reducing side reactions. The knowledge gathered from this research helps to create effective catalytic systems that convert bio-alcohols into renewable fuels and value-added chemicals as well as understanding the reaction pathways of methanol/ethanol coupling. This opens the door to more carbon neutrality for producing chemicals and energy.