Effect of Surface and Oxygen Coverage on Ethylene Epoxidation
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Ethylene epoxidation was studied as a function of oxygen coverage; for three different surfaces (111), (100) and (110) of three different IB metals using periodical DFT calculations. Oxygen coverage dependence was tested for 11, 25 and 33 % surface oxygen on Ag(111) surface. Calculations showed that increasing oxygen amount increased the exothermicity of the reaction while lowering the activation barriers. At studied oxygen ratios ethylene oxide and acetaldehyde formations proceed through OMC intermediate. In agreement with earlier studies, predicted selectivity is independent of surface structure. Generally the activation barriers for aldehyde formation are lower than those for epoxide formation on the studied surfaces. On copper surfaces the high stability of the precursor intermediates caused high activation barriers for the product formations. Also, epoxide formation is endothermic with respect to pre-oxygenated copper surfaces. On the other hand gold surfaces showed the smallest activation barriers for the product formations. Ag surfaces did not show conclusive differences for the activation barriers for epoxide versus aldehyde formation, which is in agreement with the ~50 % EO selectivity of the un-promoted metallic silver.
KeywordsAlkene Epoxidation Ethylene Oxide Silver Gold Copper
This work was supported by NWO-NCF and SARA for the computation time on Huygens computer system with the project number SH-074-09 and was supported in part by TÜBİTAK through TR-Grid e-Infrastructure Project.
- 1.Shell (2010) Ethylene oxide/ethylene glycol (EO/EG) processes. http://www.shell.com/home/content/globalsolutions/products_services/licensed_technologies/petrochemical_technology/ethylene_oxide_processes. Accessed July 2012
- 2.Lefort ET (1935), Process for the production of ethylene oxide. Catalyse, Generalisee FR. DE. SAGoogle Scholar
- 3.Voge HH, Adams CR (1967) Catalytic oxidation of olefins. Academic Press, New YorkGoogle Scholar
- 12.Grant RB and Lambert RM (1983) J Chem Soc, Chem Commun (12):662Google Scholar
- 23.Linic S, Barteau MA (2008) Heterogeneous catalysis of alkene epoxidation. Wiley, WeinheimGoogle Scholar
- 31.Van Santen RA, Kuipers HPCE (1987) The mechanism of ethylene epoxidation. Academic Press, New YorkGoogle Scholar
- 44.Michaelides M-LBaA (2006) Exploring the catalytic activity of a noble metal: the Ag catalyzed ethylene epoxidation reaction. Imperial College Press, LondonGoogle Scholar
- 53.Grant RB et al (1987) J Chem Soc Faraday Transact1 Phys Chem Condens Phases 83(7):2035Google Scholar
- 59.Handbook of Chemistry & Physics Online (2011) 91: http://www.hbcpnetbase.com. Accessed July 2012