Showing papers by "Masatake Haruta published in 2017"
TL;DR: A classical SMSI is demonstrated for Au/TiO2, evidenced by suppression of CO adsorption, electron transfer from TiO2 to Au nanoparticles, and gold encapsulation by a TiOx overlayer following high-temperature reduction (reversed by subsequent oxidation), akin to that observed for titania-supported platinum group metals.
Abstract: Supported metal catalysts play a central role in the modern chemical industry but often exhibit poor on-stream stability. The strong metal–support interaction (SMSI) offers a route to control the structural properties of supported metals and, hence, their reactivity and stability. Conventional wisdom holds that supported Au cannot manifest a classical SMSI, which is characterized by reversible metal encapsulation by the support upon high-temperature redox treatments. We demonstrate a classical SMSI for Au/TiO2, evidenced by suppression of CO adsorption, electron transfer from TiO2 to Au nanoparticles, and gold encapsulation by a TiOx overlayer following high-temperature reduction (reversed by subsequent oxidation), akin to that observed for titania-supported platinum group metals. In the SMSI state, Au/TiO2 exhibits markedly improved stability toward CO oxidation. The SMSI extends to Au supported over other reducible oxides (Fe3O4 and CeO2) and other group IB metals (Cu and Ag) over titania. This discovery highlights the general nature of the classical SMSI and unlocks the development of thermochemically stable IB metal catalysts.
319 citations
TL;DR: In contrast to traditional catalysts, the gold catalyst is inert with respect to the vinyl group and is only active with regard to the nitro group, as demonstrated by the results of the control experiments and attenuated total reflection infrared spectra.
Abstract: Chemoselective hydrogenation of 3-nitrostyrene to 3-vinylaniline is quite challenging because of competitive activation of the vinyl group and the nitro group over most supported precious-metal catalysts. A precatalyst comprised of thiolated Au25 nanoclusters supported on ZnAl-hydrotalcite yielded gold catalysts of a well-controlled size (ca. 2.0 nm)—even after calcination at 500 °C. The catalyst showed excellent selectivity (>98 %) with respect to 3-vinylaniline, and complete conversion of 3-nitrostyrene over broad reaction duration and temperature windows. This result is unprecedented for gold catalysts. In contrast to traditional catalysts, the gold catalyst is inert with respect to the vinyl group and is only active with regard to the nitro group, as demonstrated by the results of the control experiments and attenuated total reflection infrared spectra. The findings may extend to design of gold catalysts with excellent chemoselectivity for use in the synthesis of fine chemicals.
122 citations
TL;DR: In this article, two series of Fe-and Cr-doped Co3O4 catalysts were prepared by a single-step solution combustion technique, and the catalytic activity of new materials for low-temperature CO oxidation was correlated to the nature of the dopant.
Abstract: Co3O4 with a spinel structure shows unique activity for CO oxidation at low temperature under dry conditions; however the active surface is not very stable. In this study, two series of Fe- and Cr-doped Co3O4 catalysts were prepared by a single-step solution combustion technique. Fe was chosen because of its redox activity corresponding to the Fe2+/Fe3+ redox couple and compared to Cr, which is mainly stable in the Cr3+ state. The catalytic activity of new materials for low-temperature CO oxidation was correlated to the nature of the dopant. As a function of dopant concentration, the temperature corresponding to the 50% CO conversion (T50) demonstrated significant differences. The maximal activity was achieved for 15% Fe-doped Co3O4 with T50 of −85 °C and remained almost constant up to 25% Fe. In the case of Cr, the activity was observed to be maximum for 7% of Cr with T50 of −42 °C and significantly decreased for higher Cr loadings. Similarly, there was a contrasting behavior in catalyst stability too. 1...
64 citations
TL;DR: A series of imidazole containing crosslinked copolymer poly(divinylbenzene- co - N - vinylimidazoles) (PDVB-VI- n ) supported Au catalysts were prepared by using AuCl 3 as the precursor as discussed by the authors.
Abstract: A series of imidazole containing crosslinked copolymer poly(divinylbenzene- co - N - vinylimidazole) (PDVB-VI- n ) supported Au catalysts were prepared by using AuCl 3 as the precursor. The resulting Au/PDVB-VI- n catalysts were employed to catalyze the aerobic oxidation of benzyl alcohol with molecular oxygen as the sole oxidant and water as the solvent. By optimizing the sizes of Au NPs and the composition of PDVB-VI- n , Au/PDVB-VI- n exhibited the excellent activities even only using a small amount of basic K 2 CO 3 . Interestingly, the conversion of benzyl alcohol increased monotonously with the increase of Au sizes in the range of 2–5 nm, but the selectivity to benzoic acid increased first and then decreased gradually. The highest selectivity to benzoic acid of ∼80%was achieved over ∼3.2 nm Au NPs.
22 citations
TL;DR: In this article, the surface plasmon resonance (SPR) mediated visible-light-responsive photocatalyst achieved over 99% conversion of pollutants (thiophene, thiol, rhodamine B, and phenol) during photocatalytic oxidation with oxygen or air as oxidant under visible light irradiation.
Abstract: Solar driven catalysis by semiconductors is considered as a promising route to mitigate environmental problems caused by the combustion of fossil fuels and water pollution. Surface plasmon resonance (SPR) has offered a new opportunity to overcome the limited efficiency of photocatalysts. Herein we report that the SPR-mediated visible-light-responsive photocatalyst, 0.5 wt.% Au/SO42−–TiO2, can achieve over 99% conversion of pollutants (thiophene, thiol, rhodamine B, and phenol) during photocatalytic oxidation with oxygen or air as oxidant under visible light irradiation. The considerable enhancement of photocatalytic activity can be attributed to the synergistic effect of Au SPR and Lewis acidic SO42−–TiO2 which are beneficial for the efficient separation and transfer of the photo-generated electrons and holes. Such a strategy would be important to the design and preparation of highly photocatalytic active semiconductor catalysts.
20 citations
TL;DR: In this paper, small nanoparticles supported on metal oxides could be prepared by deposition-precipitation followed by microwave irradiation as a drying method and then calcination, and the drying method influenced the size of the Au particles.
19 citations
23 Jun 2017
3 citations
Patent•
14 Sep 2017
TL;DR: In this paper, a novel gold composite material comprising a carrier and gold microparticles carried on the carrier is characterized, where the carrier being an acidic solid metal oxide, and a gold colloid solution containing gold particles having a particle diameter of 5 nm or less is used as the solution.
Abstract: [Problem] To provide a novel gold composite material having higher catalytic activity than conventional gold nanoparticle catalysts, a method for manufacturing the gold composite material, and a gold nanocatalyst in which the gold composite material is used. [Solution] A gold composite material comprising a carrier and gold microparticles carried on the carrier, the gold composite material being characterized in that the carrier is an acidic solid metal oxide. A method for manufacturing a gold composite material, wherein the method for manufacturing a gold composite material is characterized in being provided with a carrying step for carrying gold microparticles using the acidic solid metal oxide and a gold colloid solution, and in the carrying step, a solid metal oxide having a high specific surface area of at least 20 m2/g is used as the solid metal oxide, and a gold colloid solution containing gold particles having a particle diameter of 5 nm or less is used as the gold colloid solution.