Density functional theory (DFT) calculations are used to investigate the oxidative carbonylation of ethanol occurring on Cu(I)/beta or Pd(II)/beta. The thermochemistry and activation energy for all elementary steps involved in the formation of diethyl carbonate are presented. Upon calculation, we identify that the mechanisms for the formation of surface O atom are varying on different catalysts. Ethanol can react with the surface O atom to produce (C2H5O)(OH)-mip (m=Cu+,Pd2+,) species. And this intermediate can further react with carbon monoxide or ethanol to give monoethyl carbonate or di-ethoxied species ((C2H5O)(2)-M/beta). Diethyl carbonate can form via two distinct reaction pathways: (I) ethanol reacts with monoethyl carbonate or (II) carbon monoxide inserts into di-ethoxide species. Upon calculation, we confirmed that both reaction pathways for the formation of DEC are accessible on Cu(I)/beta catalyst, whereas only Path II is achievable on Pd(II)/beta catalyst. C) 2014 Elsevier BAT. All rights reserved.