Sites for the selective hydrogenation of ethyne to ethene on supported NiO/Au catalysts

Abstract

Au, NiO, and NiO/Au clusters of 2.5-16 nm, supported on Al 2 O 3 , ZrO 2 , TiO 2 , and ZnO, were studied in the purification of ethene feedstock from ethyne by hydrogenation at 357 K. The Au, NiO, and NiO/Au catalysts possessed 100 % selectivity to ethene. As the size of NiO clusters decreased from 7 to 3 nm, the turnover frequency (TOF) decreased from 812-1,023 to 276 h −1 . In contrast with NiO, Au activity increased with decreasing particle size. NiO/Au catalysts possessed higher stability and activity in comparison with Au and NiO catalysts. The synergistic gain on NiO/Au clusters (SG) calculated as TOF NiO/Au -TOF Au -TOF NiO was 1,466; 1,147; 563; and 569 h −1 for NiO/Au/Al 2 O 3, NiO/Au/TiO 2 , NiO/Au/ZnO, and NiO/Au/ ZrO 2 , respectively. The reasons of the observed catalytic trends and the origin of the most active and selective sites are discussed.

The effect of metal deposition order on the synergistic activity of Au–Cu and Au–Ce metal oxide catalysts for CO oxidation

“…The formation of Au δ+ accompanied by reduction of CuO and CeO 2 , which was observed for our bimetallic catalysts, is in agreement with the reported data [38,[55][56][57] 0<δ<1) oxidation state due to electron transfer from gold to the metal oxide [55]. The reduction of Ce 4+ to Ce 3+ after deposition of Au on CeO 2 (111) was observed by Škoda et al [58].…”

“…This correlation indicates that the size effects and rough shape of the particles take an important part in the formation of the most active sites of the bimetallic catalysts. °C range, all bimetallic catalysts have exhibited high synergistic gain, which is calculated as the difference between CO conversion over bimetallic catalyst and the sum of CO conversions over its monometallic precursor measured at a specified temperature [56]. At high temperatures, the synergistic gain decreased (Fig.…”

Hydrogenation of Propyne Verifying the Harmony in Surface and Bulk Compositions for Fe-Ni Alloy Nanoparticles

“…2(c)). [22][23][24][25] Even if the latter step is rate determining, the apparent E a probably depends on the H 2 dissociation, because enhancement of the dissociation provides Inset is a magni cation of x ≤ 0.8. The rate for x = 0 was assumed to be 0 by measurement using commercial Fe powder.…”

Ligand-protected gold clusters: the structure, synthesis and applications

“…144 Considerable activation of the hydrocarbon in the complex favours efficient hydrogenation of acetylene. 145 Supported gold nanoparticles are widely used in heterogeneous catalysis. These catalysts are prepared by traditional chemical methods, e.g., impregnation of support with Au III or Au I salts and subsequent reduction and calcination.…”

“…This is a common feature of gold clusters and gold nanoparticles in selective hydrogenation of alkynes. 144,145,344,345 Concluding this Section, the use of [L s Au n X m ] q atomic clusters as catalysts allows catalytic reactions to be studied at the molecular level and thus the measured property of the catalyst (activity, selectivity and stability) can be related to a particular composition and structure of the cluster; this can hardly be done for most heterogeneous catalytic systems. The type of the active site in the heterogeneous systems based on ligand-protected gold clusters is governed by the annealing temperature and reaction temperature.…”