Density functional theory study of ethanol synthesis from dimethyl ether and syngas over cobalt catalyst

Abstract The reaction mechanism of ethanol synthesis from dimethyl ether (DME) and syngas was studied via density functional theory calculations. Various possible pathways for ethanol formation, and byproduct formations of methanol, acetic acid, methane, carbon dioxide, and water over an active cobalt stepped surface were calculated. The most favorable pathway for ethanol synthesis starts with the dissociation of dimethyl ether to CH 2 , followed by carbon monoxide insertion to form CH 2 CO, and then undergoes successive hydrogenations to give ethanol. CH 3 CHO hydrogenation to CH 3 CHOH becomes the rate–determining step with a reaction barrier of 1.48 eV. DME decomposition and CH 2 carbonylation occur easily with low barriers of 0.61 eV and 0.48 eV, respectively. Carbon monoxide insertion into CH 2 is more facile than into CH 3 and CH. Hydrogenation at the carbon atom occurs prior to the oxygen atom in the order of α–carbon > carbonyl carbon > oxygen. The calculations demonstrate that ethanol synthesis via DME carbonylation and hydrogenation is thermodynamically favored and is kinetically faster than that via syngas direct synthesis. Methane and acetic acid are two dominant competing byproducts.