Monodireotional 12 membered ring zeolites (offretite, L. mordenite and Ω) are very inefficient as catalysts for formaldehyde benzene condensation to give diphenylmethane, esterifioation of phenylacetic acid with equimolar amounts of ethanol, Friedel-Crafts acylation of 3-phenylpropanoyl chloride with anisole and Claisen-Schmidt condensation of acetophenone with benzaldehyde. This fact has been attributed to diffusional constraints of organic compounds inside the channels. By contrast, the behaviour of the tridirectional β zeolite is very similar to that of dealuminated HY zeolites, increasing the turnover of the acid sites with the framework Si-to-Al ratio.
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