The nature of the active site for vinyl acetate synthesis over Pd–Au

Promotional Effects of Au in Pd-Au Catalysts for Vinyl Acetate Synthesis

“…Such a broad feature can be assigned to both -bonded and di--bonded C 2 D 4 with the former desorbing at the lower temperature and the latter, at the higher temperature [2,[54][55][56]. In contrast, C 2 D 4 -TPD on Pd-Au (1:1 atomic ratio) nanoparticles shows a much narrower desorption feature between 180 and 260 K with a peak desorption temperature of 215 K. The sharper desorption feature and the lower peak desorption temperature are consistent with the formation of isolated Pd monomers, to which ethylene can -bond [2]. These results demonstrate that the addition of Au to Pd clusters inhibits the formation of adjacent Pd atoms and thus the formation of the strongly bound di--C 2 D 4 species, the species that converts to ethylidyne.…”

“…The key results are that Au atoms break contiguous Pd atom ensembles at the surface into isolated Pd monomers. The absence of contiguous Pd sites significantly reduces the formation of combustion by-products and suppresses the poison effects of CO, thus enhancing the VA formation selectivity and activity.Key words: vinyl acetate; bimetal; palladium; gold; alloy effect Bimetallic alloy systems are important in numerous technological applications, including metallurgy, catalysis, electrochemistry, magnetic materials, and microelectronics fabrication [1,2]. In heterogeneous catalysis, for example, the addition of a second metal component can greatly enhance the catalytic performance, particularly with respect to activity and selectivity [2][3][4][5].…”

“…In heterogeneous catalysis, for example, the addition of a second metal component can greatly enhance the catalytic performance, particularly with respect to activity and selectivity [2][3][4][5]. A thorough understanding of the reaction mechanism over bimetallic surfaces at the atomic level can aid in understanding reaction mechanisms and in the optimization of catalytic performance.…”

“…Pd is an active catalyst for the acetoxylation of ethylene to vinyl acetate (VA), see equation (1) [2,3,[24][25][26][27][28][29][30][31][32][33][34][35][36]. However Pd is also an active catalyst for the combustion of ethylene and acetic acid and thus exhibits a low selectivity for VA synthesis (equations (2) and (3) 3) The addition of small amounts of Au to a supported Pd catalysts can significantly enhance its selectivity and activity for this reaction, as shown in Fig.…”

“…Bimetallic alloy systems are important in numerous technological applications, including metallurgy, catalysis, electrochemistry, magnetic materials, and microelectronics fabrication [1,2]. In heterogeneous catalysis, for example, the addition of a second metal component can greatly enhance the catalytic performance, particularly with respect to activity and selectivity [2][3][4][5].…”