Direct Chlorination of Ethene on ZnO (000(1)over-bar) by Hot Chlorine Atoms

초록

The interaction between ethene and Cl-2 on ZnO(000 (1) over bar) has been investigated using X-ray photoelectron spectroscopy (XPS), temperature-programmed desorption (TPD), and density functional theory (DFT) calculations. At 110 K, the Cl-2 molecule is perpendicularly adsorbed on ZnO(000 (1) over bar). Upon heating, Cl-2 is dissociated on the surface in the temperature range of 200-230 K. When the surface coadsorbed with Cl-2 and ethene is heated, the desorption of 1,2-dichloroethane is observed at similar to 230 K. The desorption temperature is comparable to the dissociation temperature of Cl-2 on ZnO(000 (1) over bar). Ethene does not react with Cl atoms chemisorbed on ZnO(000 (1) over bar). We propose that "hot" Cl atoms, which are produced during thermal dissociation of Cl-2, 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.

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