Ethanol dehydration on silica-aluminas: Active sites and ethylene/diethyl ether selectivities

Commercial silica-alumina catalysts prepared by different procedures have been characterized. Both present strong Lewis acidity together with Br\uf8nsted sites able to protonate pyridine. No evidence of "zeolitic" bridging OH's but significant heterogeneity of terminal silanol groups, part of which are likely "pseudobridging", was found. Similar high activity in ethanol conversion but markedly different selectivities to ethylene and diethyl ether were found. They are less active than both zeolites and \u3b3-Al2O3. Lewis sites with alumina-like acidobasic neighbor are more selective for ethylene production while Lewis sites with silica-like covalent neighbor are more selective for diethyl ether