Efficient conversion of ethanol to 1-butanol and C₅-C₉ alcohols over calcium carbide

Production of 1-butanol or alcohols with 4-9 carbon atoms (C₄-C₉ alcohols) from widely available bio-ethanol has attracted much interest in recent years in academia and industry of renewable chemicals and liquid fuels. This work discloses for the first time that calcium carbide (CaC₂) has a superior catalytic activity in condensation of ethanol to C₄-C₉ alcohols at 275-300 °C. The 1-butanol yield reached up to 24.5% with ethanol conversion of 62.4% at the optimized conditions. The by-products are mainly alcohols with 5-9 carbons besides 2-butanol, and the total yield of all the alcohols reached up to 56.3%. The reaction route was investigated through controlled experiments and quantitative analysis of the products. Results indicated that two reaction routes, aldol-condensation and self-condensation, took place simultaneously. The aldol-condensation route involves coupling of ethanol with acetaldehyde (formed from ethanol dehydrogenation) to form 2-butenol, which is subsequently hydrogenated to 1-butanol. The alkynyl moiety in CaC₂ plays an important role in the catalytic pathways of both routes and affords the good activity of CaC₂. CaC₂ is converted to acetylene [C₂H₂] and calcium hydroxide [Ca(OH)₂] simultaneously by the H₂O that was generated from the condensation of alcohols.