Exploring and suppressing decomposition pathways in Vinyl Acetate Monomer synthesis

CALAZA, FLORENCIA C.; TYSOE, WILFRED T.

Asheville, NC

Simposio; South Eastern Catalysis Society 8th Annual Symposium; 2009

North American Catalysis Society

(Poster - Presenter) Vinyl acetate monomer is industrially synthesized from ethylene, acetic acid and oxygen using Pd based catalysts. In the last decade, Pd-Au catalysts have been shown to have increased selectivity to VAM compared to pure Pd. The surface chemistry of VAM adsorbed on Pd(111) shows two different decomposition pathways, but when oxygen is pre-adsorbed on the surface one of them is almost completely suppressed.1 The adsorption geometry changes from pi-bonded to di-sigma bonded in the presence of surface oxygen making one of these pathways to be less accessible. On Au-Pd(111) alloys, the same effect is found, without oxygen, which partially explains the higher selectivity obtained.2 Same effect has been found for the reactivity of VAM adsorbed on Pd(100) and compared to oxygen pre-covered Pd(100) 3 and Au-Pd(100) alloys 4. Under reaction conditions during VAM synthesis, ethylene, acetic acid and vinyl acetate molecules rapidly burn in the presence of oxygen. By using Au, lees oxygen feed will be needed, giving less combustion products. References 1) F. Calaza, D. Stacchiola, M. Neurock, W.T. Tysoe, Surface Science, 598 (2005) 263. 2) F. Calaza, Z. Li, F. Gao, J. Boscoboinik and W.T. Tysoe, Surface Science, 602 (2008) 3523. 3) Z. Li, F. Calaza, C. Plaisance, M. Neurock and W.T. Tysoe, J. Phys. Chem. C, 113 (2009) 971 4) F. Calaza, Z. Li, F. Gao, J. Boscoboinik and W.T. Tysoe, Surf. Sci., in press