Search

Epoxidation of styrene over vanadium silicalite with ferrierite (FER) type topology is undertaken. Influence of temperature, pressure, various solvents and solvent to substrate mole ratio was investigated. Conversion increased with increase in temperature and pressure. Solvent to substrate mole ratio is found to play a crucial role in increasing the conversion and selectivity. Catalytic activity of V‐FER was compared with those of Ti‐FER, TS‐1 and Fe‐FER. In the case of V‐ and Ti‐ferrierite analogs, styrene oxide was the major product, whereas phenylacetaldehyde was the major product in the case of TS‐1. The catalyst could be recycled after washing by a suitable solvent such as acetone and showed no significant loss in catalytic activity.

A natural zeolite of stilbite type, collected from the Deccan traps (Aurangabad, M.S., India), has been investigated for its selectivity sequence in exchanging extra-framework cations for the first time, using Ca2+, Sr2+, Ba2+, Mg2+, Na+and Ag+cations as the probe cations. The different cation-exchanged forms were characterised by X-ray powder diffraction, IR spectroscopy, TG/DTA, chemical analysis and water sorption capacity.Water sorption isotherms in the temperature range 303–393 K were obtained as a function of different non-framework cations up to a pressure of 22 Torr. The sorption data were analysed in terms of different sorption models. The characteristics and population of the non-framework cations were found to influence the chemical affinity for water sorbate almost in a similar trend.

The epoxidation of styrene was studied using a titanium silicate molecular sieve TS-1 as catalyst and dilute (25%) H₂O₂ as oxidizing agent. Mainly two types of reactions were observed: The major reaction (~75-85 mole%) was epoxidation and its further isomerization into phenylacetaldehyde. The other reaction was oxidative cleavage into benzaldehyde (~10-20 mole%). While generally the products were analyzed by capillary GC and GCMS, in certain cases, the products were separated and isolated by column chromatography and analyzed by 1H and 13C NMR spectroscopy. Polar and nonpolar solvents have marked influence on product distribution in styrene epoxidation. In methanol, a significant part of styrene epoxide undergoes alcoholysis through the addition of methanol forming 2-methoxy-2-phenyl-ethanol. The influence of reaction time, temperature, and styrene/H₂O₂ molar ratio on the conversion and product distribution was also studied.Copyright 1995, 1999 Academic Press, Inc.