Direct synthesis of C2-C4 alcohols with methanol and CaC2 by tandem reactions

Methanol (MeOH) and calcium carbide (CaC2) are important platform compounds and many downstream chemicals have been produced from them. However, direct conversion of MeOH to higher alcohols remains a challenging topic due to the absence of beta-H in MeOH. In this study, direct synthesis of ethanol (EtOH), n-propanol and isobutanol without the use of metal catalysts and H2 was achieved in one pot at temperatures above 350 degrees C. After a 6-hour period at 425 degrees C, the total yield of these alcohols reaches 54.6%. The reaction route was mainly explored via 13C-labeling experiments and an exhaustive analysis on the gas and solid products. The results indicate that the rapid reaction of MeOH with the alkynyl moiety of CaC2 leads to the formation of methyl vinyl ether (MVE). MVE undergoes gradual hydrocracking, resulting in the formation of EtOH and methane, where MeOH severs as the provider of active hydrogen. In subsequent stages, EtOH progressively reacts with MeOH, yielding n-propanol and isobutanol. It is speculated that calcium methoxide (Ca(OCH3)2), a solid product of the CaC2 and MeOH reaction, may potentially exert a catalytic influence by facilitating the dehydrogenation of MeOH and the condensation of EtOH.