Xinli Yang

Transformation of Various Oxygen Species on the Surface of Electrolytic Silver Characterized by in Situ Raman Spectroscopy

Abstract Transformation of various oxygen species adsorbed on the electrolytic silver surface pretreated by pure oxygen at 423–973 K under ambient pressure was observed for the first time by in situ confocal microprobe Raman spectroscopy. Ag-O 2 species can transform into Ag[O-O] − species slowly at temperatures below 423 K. Once the temperature rises to 423 K, the transformation of Ag[O-O] − to Ag-O(α) species takes place. With further increase in temperature, the Ag-O(α) species first transforms to Ag-O-O-Ag and then to Ag-O(γ) species, which is the most stable oxygen species on the silver surface and can be maintained even above 973 K. As for the practical reaction system, the adsorbed molecular oxygen was found to be present on the silver surface at low temperature. It transforms to Ag-O(α) species under similar conditions to those for the partial epoxidation of ethylene, and then transforms to Ag-O(γ) oxygen species under conditions similar to those for selective oxidation of methanol to formaldehyde. A possible mechanism for the detailed transformation of oxygen species was also proposed.

A green process for O-heterocyclization of cycloocta-1,5-diene by peroxotungstic species with aqueous H2O2

The hydroxy- and carbonyl-derivatives of 9-oxabicyclo[3.3.1]nonane have been synthesized through an economic and green catalytic reaction between cycloocta-1,5-diene (COD) and aqueous H2O2 with tungstic acid as the catalyst. This process has advantages from the viewpoint of green chemistry, in that the aqueous H2O2 is used as the green oxygen donor, the only by-product of H2O2 is water and the tungstic acid catalyst can also be easily recovered. The excellent yields of the object products (1 and 2) (see Scheme 1) are reached easily under mild reaction conditions.

Tungsten containing materials as heterogeneous catalysts for green catalytic oxidation process

This chapter provides a comprehensive description of the recent advances in the field of tungsten-containing heterogeneous catalysts for green catalytic oxidation processes. This chapter contains three sections. The first exhibits the advances in the pristine tungsten-based catalysts for the green catalytic oxidation process. The second highlights various green catalytic oxidation reactions with tungsten-based catalysts supported on different carriers. The third illustrates the existing problems and outlook for the tungsten-based catalysts applied in the green catalytic oxidation reactions. All these contributions provide a proper guide and overview to tungsten-based catalysts for the sake of the better development of highly efficient green oxidation catalytic systems.