Solketal Formation in a Continuous Flow Process over Hierarchical Zeolites

摘要

Glycerol ketalization with acetone to solketal, an oxygenate fuel additive, was demonstrated over hierarchical zeolites of ZSM5, Beta and Mordenite structure in a continuous flow system. Micro-mesoporous zeolites were prepared in two steps, by means of alkaline treatment with NaOH followed by the ionic exchange with NH4NO3 and a subsequent treatment with citric acid. The presence of mesopores in the applied catalysts was confirmed by N-2 adsorption/desorption measurements and TEM microscopy. Hierarchical zeolites showed superior catalytic performance and lifetime over 24 hours under mild conditions (atmospheric pressure, acetone to glycerol molar ratio of 3 : 1, WHSV of 3-8 h(-1), reaction temperature of 323 K). Glycerol conversion of about 90 % and selectivity to solketal up to 98 % have been obtained over micro-mesoporous catalysts within 24 h without any drop of performance and the symptoms of clogging. Among all hierarchical catalysts tested in a flow reactor, the very high activity defined as solketal yield (88 %) showed ZSM5 and Beta zeolites.