Noble metal

About: Noble metal is a research topic. Over the lifetime, 15113 publications have been published within this topic receiving 337947 citations.

Catalyst and process for direct catalystic production of hydrogen peroxide, (H2O2)

Abstract: A particulate supported noble metal phase-controlled catalyst material having 5-1000 μm surface area of 50μ500 m 2 /gm is provided for use in direct catalytic production of hydrogen peroxide (H 2 O 2 ) product from hydrogen and oxygen-containing feedstreams. The catalyst is made by depositing phase controlled crystals of a noble metal such as palladium on a suitable particulate support material such as carbon black, by utilizing a precursor solution of the metal and a suitable control ionic polymer having molecular weight of 300-8000 such as sodium polyacrylate in a selected metal to polymer molar ratio of 1:0.1 to 1:10, which procedure provides desired phase control of the noble metal atoms to form widely dispersed minute noble metal crystals on the support material. The invention includes methods for making the catalyst, and also a process for utilizing the catalyst to directly produce high yields of hydrogen peroxide (H 2 O 2 ) product from hydrogen and oxygen-containing gaseous feedstreams.

Supported Metal Cluster Catalysts

Abstract: Highly dispersed metal catalysts containing supported clusters of only several metal atoms each, exemplified by Ir 4 and Ir 6 , were prepared by removal of CO ligands from supported precursors, for example, [Ir 4 (CO) 12 ] and [Ir 6 (CO) 16 ]. Transmission electron microscopy (TEM), extended X-ray absorption fine structure spectroscopy and density functional theory indicate the metal–support-oxygen coordination numbers and distances, which identify the supports as multidentate oxygen-donor ligands. Theory indicates that Ir 4 clusters in zeolite NaX are neutral or slightly negatively charged and that cluster-support bonding induces a polarization of the cluster that could affect reactivity and catalysis. Supported catalysts prepared from precursors with noble metal-oxophilic metal bonds are modeled as clusters of a few atoms of the noble metal ‘nested’ in a supported cluster of the oxophilic metal oxide, which helps to anchor and stabilize the noble metal clusters. Changes in the oxide support have only modest effects on the catalytic activities of supported metal clusters for toluene hydrogenation, but the catalytic activity of γ-Al 2 O 3 -supported Ir clusters per exposed Ir atom increases with increasing cluster size, and this observation remains to be explained.

Perspectives on Electron-Assisted Reduction for Preparation of Highly Dispersed Noble Metal Catalysts

Abstract: Electrons are the greenest reducing agent for the preparation of highly dispersed noble metal catalysts. Two methods have been developed with electrons as the reducing agent: electron beam irradiation and room-temperature electron reduction with glow discharge or radio frequency discharge as the source of electrons. In this perspective, we attempt to summarize the current status of electron reduction with those non-hydrogen discharges as the electron source. Future developments have been addressed, too. The room-temperature electron reduction via discharges is excellent for size control with fast nucleation and slow crystal growth. It is a simple, easy, cheap, and energy efficient way to reduce metal ions. It is also worthwhile to load noble metal particles into channels of ordered porous materials, like SBA-15, with no need for complex chemical modification. The room-temperature operation makes it very useful for the preparation of noble metal catalysts supported on thermal sensitive substrates like poro...

Alcohols production by hydrogenation of carboxylic acids

Abstract: Ethanol is produced from acetic acid or propanol is produced from propionic acid by contacting either acetic acid or propionic acid in the vapor phase with hydrogen at elevated temperature and a pressure in the range from 1 to 150 bar in the presence of a catalyst comprising as essential components (i) a noble metal of Group VIII of the Periodic Table of the Elements, and (ii) rhenium, optionally on a support, for example a high surface area graphitized carbon.