Platinum Group Metal-Doped Tungsten Phosphates for Selective C-H Activation of Lower Alkanes

Platinum group metal (PGM)-based catalysts are known to be highly active in the total combustion of lower hydrocarbons. However, through an alternative catalyst design reported in this paper by isolating PGM-based active sites in a tungsten phosphate matrix, we present a class of catalysts for selective oxidation of n-butane, propane, and propylene that do not contain Mo or V as redox-active elements. Two different catalyst concepts have been pursued. Concept A: isolating Ru-based active sites in a tungsten phosphate matrix coming upon as ReO3-type structure. Concept B: dilution of PGM-based active sites through the synthesis of X-ray amorphous Ru tungsten phosphates supported on SiO2. Using a high-throughput screening approach, model catalysts over a wide compositional range were evaluated for C3 and C4 partial oxidation. Bulk crystalline and supported XRD amorphous phases with similar Ru/W/P compositions showed comparable performance. Hence, for these materials, composition is more crucial than the degree of crystallinity. Further studies for optimization on second-generation supported systems revealed even better results. High selectivity for n-butane oxidation to maleic anhydride and propane oxidation to an acrolein/acrylic acid has been achieved

Ca–Ag compounds in ethylene epoxidation reaction

The ethylene epoxidation is a challenging catalytic process, and development of active and selective catalyst requires profound understanding of its chemical behaviour under reaction conditions. The systematic study on intermetallic compounds in the Ca–Ag system under ethylene epoxidation conditions clearly shows that the character of the oxidation processes on the surface originates from the atomic interactions in the pristine compound. The Ag-rich compounds Ca2Ag7 and CaAg2 undergo oxidation towards fcc Ag and a complex Ca-based support, whereas equiatomic CaAg and the Ca-rich compounds Ca5Ag3 and Ca3Ag in bulk remain stable under harsh ethylene epoxidation conditions. For the latter presence of water vapour in the gas stream leads to noticeable corrosion. Combining the experimental results with the chemical bonding analysis and first-principles calculations, the relationships among the chemical nature of the compounds, their reactivity and catalytic performance towards epoxidation of ethylene are investigated. © 2019, © 2019 The Author(s). Published by National Institute for Materials Science in partnership with Taylor & Francis Group

Synthesis of Pt3Y and Other Early-Late Intermetallic Nanoparticles by Way of a Molten Reducing Agent.

Early-late intermetallic phases have garnered increased attention recently for their catalytic properties. To achieve the high surface areas needed for industrially relevant applications, these phases must be synthesized as nanoparticles in a scalable fashion. Herein, Pt3Y-targeted as a prototypical example of an early-late intermetallic-has been synthesized as nanoparticles approximately 5-20 nm in diameter via a solution process and characterized by XRD, TEM, EDS, and XPS. The key development is the use of a molten borohydride (MEt3BH, M = Na, K) as both the reducing agent and reaction medium. Readily available halide precursors of the two metals are used. Accordingly, no organic ligands are necessary, as the resulting halide salt byproduct prevents sintering, which further permits dispersion of the nanoscale intermetallic onto a support. The versatility of this approach was validated by the synthesis of other intermetallic phases such as Pt3Sc, Pt3Lu, Pt2Na, and Au2Y

Synthesis of Pt3Y and Other Early-Late Intermetallic Nanoparticles by Way of a Molten Reducing Agent.

Early-late intermetallic phases have garnered increased attention recently for their catalytic properties. To achieve the high surface areas needed for industrially relevant applications, these phases must be synthesized as nanoparticles in a scalable fashion. Herein, Pt3Y-targeted as a prototypical example of an early-late intermetallic-has been synthesized as nanoparticles approximately 5-20 nm in diameter via a solution process and characterized by XRD, TEM, EDS, and XPS. The key development is the use of a molten borohydride (MEt3BH, M = Na, K) as both the reducing agent and reaction medium. Readily available halide precursors of the two metals are used. Accordingly, no organic ligands are necessary, as the resulting halide salt byproduct prevents sintering, which further permits dispersion of the nanoscale intermetallic onto a support. The versatility of this approach was validated by the synthesis of other intermetallic phases such as Pt3Sc, Pt3Lu, Pt2Na, and Au2Y