Eco-friendly and sustainable process for converting hydrous bioethanol to butanol

The purpose of the study was the development of water-resistant catalyst and catalytic processes for the conversion of hydrous ethanol to 1-butanol. Water, in hydrous ethanol, strongly inhibits conversion to 1-butanol on solid catalysts. In this study, the nonstoichiometric P-deficient hydroxyapatite containing carbonate anions (C-HAP), Ca10−x/2(PO4)6−x(CO3)x(OH)2, displayed good performance in the Guerbet condensation of hydrated ethanol to 1-butanol, after proper stabilization of reaction conditions. Hydrous ethanol (96 wt%) was converted on C-HAP formed as extru-dates with silica binder at 400 °C and weight jour space velocity (WHSV) = 0.5–1.0 h⁻¹ to yield 21– 23% 1-butanol and 73–74% selectivity. It displayed stable operation for up to 170 h on streams con-ducted in bench and mini-pilot rigs with catalyst loadings of 2 and 50 cm³, respectively. The process simulation employed the recycling of ethanol without laboratory verification to reach 68% theoret-ical yield of 1-butanol. The techno-economic analysis demonstrated the feasibility of this process, showing that it may be profitable depending on the prices of hydrated ethanol and 1-butanol.