DFT calculations are performed to investigate the catalytic activity of Ti-doped graphene nanoflake (Ti-GNF) in oxidation of ethylene to ethylene oxide by NO molecules. According to our results, this reaction proceeds in three steps. At first, two NO molecules are adsorbed on Ti-GNF in the dimer form and the reaction starts with the dissociation of (NO)(2) into N2O and O-ads species. Next, ethylene is oxidized to ethyleneoxy intermediate by O-ads. Finally, the cyclization of ethyleneoxy results the ethylene oxide as a desirable product. The activation energies suggest that Ti-GNF is an efficient catalyst for the epoxidation of ethylene by NO. (C) 2017 Elsevier B.V. All rights reserved.