Synergistic and size effects in selective hydrogenation of alkynes on gold nanocomposites

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

“…The degree of NaCl removing was controlled via AgNO 3 test. Then the sample was dried for 24 h at 298 K and calcined for 3 h in air at 623 K. Monometallic NiO samples were prepared by impregnation of the calcined support (3 h, air, 623 K) with the aqueous solution of Ni(NO 3 ) 2 , corresponding to the pore volume of the support, followed by drying for 24 h at 298 K and calcining for 3 h in air at 623 K [15]. Bimetallic NiO/ Au/supports and Ag/Pd/Al 2 O 3 were produced by pore volume impregnation of fresh Au/supports and Pd/Al 2 O 3 with the aqueous solution of Ni(NO 3 ) 2 and AgNO 3 , respectively.…”

“…It was reported that Au/Al 2 O 3 catalysts possess high activity (up to 0.142 s −1 ) in the hydrogenation of ethynylbenzene into styrene at 423 K. A synergistic effect was revealed for NiO/Au/Al 2 O 3 in the hydrogenation of ethyne into ethene [15]: The conversion of ethyne on the NiO/Au catalysts was higher than the sum of conversions on Au and Ni catalysts. It was found that synergistic gain on NiO/Au clusters was maximized at 357 K, and Au/Ni ratio equaled 1:1 [15]. According to the analysis of oxidation state of metals in gold-contained catalysts [7], it was proposed that synergistic effect could be caused by the formation of new Au δ+ catalytic sites.…”

“…Au/supports and Pd/ Al 2 O 3 were produced by deposition-precipitation [15,16]. In typical synthesis, 50 ml of the aqueous solution of HAuCl 4 (or PdCl 2 ) with 5.8×10 −6 g/ml metal content was adjusted to pH equal to the IEP of the support by adding the aqueous solution of NaOH (0.1 M).…”

“…This work is an extension of studies of the catalytic properties of Au and NiO/Au clusters in the hydrogenation of ethyne derivatives [13,15]. It was reported that Au/Al 2 O 3 catalysts possess high activity (up to 0.142 s −1 ) in the hydrogenation of ethynylbenzene into styrene at 423 K. A synergistic effect was revealed for NiO/Au/Al 2 O 3 in the hydrogenation of ethyne into ethene [15]: The conversion of ethyne on the NiO/Au catalysts was higher than the sum of conversions on Au and Ni catalysts.…”

Effects of Ultrasound and Microwaves on Selective Reduction: Catalyst Preparation and Reactions

“…[28] Such catalysts include phosphinated polymer incarcerated (PI) palladium catalysts, [122] nickel(0) nanoparticles, [123] zinc and ammonium chloride, [124] non-precious metal alloys, [125] ruthenium (II) phosphine/mesoporous silica catalysts, [126] and Au/Al2O3 and Au-Ni/Al2O3 nanocomposites, and BASF's NanoSelect Pd catalysts. [127,128] In 1985, the US-accelerated hydrogenation of olefins using a Pd catalyst and hydrazine under N2 atmospheric pressure was reported. [10] In the hydrogenation of diphenylacetylene, a 75% yield was obtained by sonication in an US bath in 1 h, while a 24% yield was obtained with stirring in 1 h. The improvement may arise from increased catalyst surface area caused by the ultrasonic fragmentation of the carbon support, or from the sonic activation of the Pd surface.…”