Jinhai Wang

In situ surface Raman spectroscopy studies of oxygen adsorbed on electrolytic silver

In situ Raman spectroscopy has been employed to investigate oxygen adsorption on electrolytic silver catalyst under industrial conditions for methanol oxidation to formaldehyde. Both adsorbed atomic and molecular oxygen species are shown to exist on the silver surface in O2 flow above 870 K. The peroxide species is determined to be a precursor to atomic adsorbed oxygen. In consideration of the industrial process, the molecular mechanism of the partial oxidation of methanol and the adsorption mechanism of oxygen on electrolytic silver surface are discussed.

In situ Raman spectroscopy studies on the methanol oxidation over silver surface

Abstract In situ surface Raman spectroscopy has been employed to investigate the oxidation of methanol on a silver. The intermediates at various temperatures were identified. According to the results, the reaction pathways in the practical process were suggested and compared with the conclusion obtained under UHV condition previously. They showed a remarkably close agreement except the temperature at which the surface intermediates exist. All these results proved that the mechanism of methanol oxidation obtained under UHV condition is effective under the industrial conditions.

Interaction of oxygen with silver surface at high temperature

The interaction between oxygen and silver surface at high temperature was investigated by Auger electron spectrometer (AES), ISS, X-ray photoelectron spectra (XPS), thermal desorption spectra (TDS) and high-resolution electron energy loss spectra (HREELS). When dosing oxygen to silver surface at 873 K, a new atomic oxygen species forms on the silver surface. This species of oxygen has very high thermal stability, and the TDS experiment shows no detectable desorption peak appearing below 973 K. The O-1s binding energy of this oxygen species is 529.3 eV and HREELS result gives a peak at 352 cm(-1). All these properties show that this kind of atomic oxygen species is different from those previously found on silver surface

Oxidative dehydrogenation of glycol to glyoxal on a P-modified electrolytic silver catalyst

A phosphorus-modified electrolytic silver catalyst was prepared and used as catalyst in the oxidative dehydrogenation of glycoto glyoxal. The yield of glyoxal was observed as high as 82% at 98% conversion for the Ag-P catalyst, while 62% at 89% conversion for the pure electrolytic silver. The formation of the surface compounds between the phosphorus additives and the silver surface was demonstrated by means of XPS and SEM. It caused the decrease of the surface concentration of atomic oxygen species, and restrained the decomposition and total oxidation of adsorbed glycol to C1 products.

In situ surface Raman spectroscopy studies on the interaction between oxygen and ethanol on electrolytic silver catalyst

In situ Raman spectroscopy is employed to investigate the oxidation of ethanol on the electrolytic silver catalyst under catalytic conditions. Over the temperature range of 300–873 K, the configuration of the surface intermediates is detected. The ethoxide species, acetate species, adsorbed acetaldehyde and surface hydroxide exist on the silver surface. The mechanism for the oxidation of ethanol on the silver surface under industrial conditions is discussed and compared with that obtained in ultrahigh vacuum systems.

Synthesis and evaluation of a ruthenium–copper oxide/silica catalyst derived from microemulsion processing

Bimetallic Ru–Cu catalysts supported on SiO2 have been synthesized in microemulsions using sodium metasilicate (Na2SiO3), copper nitrate (Cu(NO3)2·3H2O) and ruthenium chloride (RuCl3) at 28 °C. The microemulsion system consists of sodium 1,4‐bis(2‐ethylhexyl) sulfosuccinate (AOT) and sodium dodecyl sulphate (SDS), cyclohexane, and an aqueous solution of sodium metasilicate or metal salts. The catalysts have been characterized by XPS, EDX/SEM with line scanning and they possess a very narrow pore size distribution (around 38 Å) and relatively high specific surface areas (around 400 m2/g). The catalytic results of the N2O decomposition reveal that higher conversions of N2O can be achieved by the catalysts synthesized from the microemulsion process at lower temperatures (around 400 °C).