The structure and properties of 12-heteropolyacid of molybdenum and tungsten (H3PMo6W6O40) solvated by dimethyl ether

The crystal structure of H3PMo6W6O40 3C2H6O was determined by X-ray crystallography and refined to R = 0.0698 based on 2279 observed reflections to give unit cell parameters a = 16.48(2)Angstrom, c = 25.205(5)Angstrom , gamma = 120 degrees, hexagonal, space group R (3) over bar. The organic solvent molecules were characterized also by IR, H NMR spectra. Weak interaction existed between the organic solvent and the heteropoly acid in the secondary structure. The novel compound showed different behaviours in solubility, oxidizability and photosensitivity in comparison with classical dodeca heteropolyacid of molybdenum and tungsten. (C) 1998 Elsevier Science B.V.

Selective homogeneous snythesis of dimethyl ether from methanol

Selected Bronsted acidic ionic liquids were tested as homogeneous catalysts for the dehydration of methanol to dimethyl ether. Ionic liquids incorporating an alkanesulfonic acid as a part of the cation, a complex acidic anion, [A(2)H](-), or both, proved to be good catalysts for this process, providing high conversions and selectivities. Homogeneous catalysis in the liquid state represents a novel approach to dimethyl ether synthesis.

Activity and deactivation studies for direct dimethyl ether synthesis using CuO-ZnO-Al2O3 with NH(4)ZSM-5, HZSM-5 or gamma-Al2O3

Herein we investigate the use of CuO-ZnO-Al2O3 (CZA) with different solid acid catalysts (NH(4)ZSM-5. HZSM-5 or gamma-Al2O3) for the production of dimethyl ether from syngas. It was found that of the solid acids, which are necessary for the dehydration function of the admixed system, the CZA/HZSM-5 bifunctional catalyst with a 0.25 acid fraction showed high stability over a continuous period of 212 h.

As this particular system was observed to loose around 16.2% of its initial activity over this operating period this study further investigates the CZA/HZSM-5 bifunctional catalyst in terms of its deactivation mechanisms. TPO investigations showed that the catalyst deactivation was related to coke deposited on the metallic sites: interface between the metallic sites and the support near the metal-support: and on the support itself.