Direct Chlorination of Ethene on ZnO (0001̅) by Hot Chlorine Atoms

Abstract

The interaction between ethene and Cl2 on ZnO(0001̅) has been investigated using X-ray photoelectron spectroscopy (XPS), temperature-programmed desorption (TPD), and density functional theory (DFT) calculations. At 110 K, the Cl2 molecule is perpendicularly adsorbed on ZnO(0001̅). Upon heating, Cl2 is dissociated on the surface in the temperature range of 200–230 K. When the surface coadsorbed with Cl2 and ethene is heated, the desorption of 1,2-dichloroethane is observed at ∼230 K. The desorption temperature is comparable to the dissociation temperature of Cl2 on ZnO(0001̅). Ethene does not react with Cl atoms chemisorbed on ZnO(0001̅). We propose that “hot” Cl atoms, which are produced during thermal dissociation of Cl2, promote the direct chlorination of C2H4. The energy of the hot Cl atoms is calculated to be maximum 27.5 kcal/mole higher than the energy of the chemisorbed Cl atoms.