Chemical equilibrium controlled synthesis of polyoxymethylene dimethyl ethers over sulfated titania

The chemical equilibrium and reaction kinetic behavior in the synthesis of polyoxymethylene dimethyl ethers （DMMn） were investigated over sulfated titania in order to reveal the decisive factor controlling the reaction. The results showed that the molar ratio of adjacent DMMn products in equilibrium solution had the same value, which depended absolutely on the reaction temperature. Meanwhile, the reactions had the same DMMn products distributions under varied reaction conditions. The equilibrium constants of the related step-wise reactions for DMMn formation were equal, which were calculated based on the bulk compositions of the reaction solution. And thus, the selectivity to DMMn was mainly controlled by the chemical equilibrium, i.e., thermodynamic control. In brief, the present results provide some guidance for future synthesis of DMMn.

Catalytic Decomposition of Methylene Chloride by Sulfated Titania Catalysts

Catalytic decomposition of methylene chloride in air below 300℃ was studied. Sulfated titania was very effective in converting 959ppm methylene chloride selectively to CO, C02 and HCl. Complete decomposition of methylene chloride was achieved at low temperature (275℃ ). It was found that the acidic property of catalyst was a determinant factor for the catalytic activity. The presence of water vapor in the feed stream remarkably reduced the catalytic activity, which could be due to the blockage of acidic sites on the surface of catalyst by water molecules. A bifunctional catalyst comprising copper oxide was developed to improve the selectivity of catalytic oxidation , which indicated that copper oxide can promote the deep oxidation of methylene chloride. The crystal form of TiO2 imposes an important influence upon the catalytic oxidation.