Abstract
Although the oxidative hydration of ethylene with hydrogen peroxide (H2O2) to ethylene glycol (EG) over Ti-MWW zeolites take advantages of step-saving and facile operation, both H2O2 utilization efficiency and EG yield are relatively low, because some extra-framework octahedral Ti species are usually formed in the Ti-MWW zeolites synthesized by prevailing methods, which are detrimental to selective oxidation. In the present work, an acid-modulated isomorphous substitution method, i.e., layered borosilicate MWW-type zeolite (ERB-1) treated with HNO3 aqueous solution containing tetrabutyl orthotitanate (TBOT), is developed to synthesize a Ti-MWW zeolite without extra-framework octahedral Ti species under the optimized synthesis conditions. In combination with the results from extensive characterizations for the synthesized zeolites, it is found that in the zeolite prepared by the currently developed synthesis method there are more open Ti(OSi)3OH sites formed, resulting in the stronger Lewis acidity that is very helpful to EG production from the oxidative hydration of ethylene with H2O2, compared to the one synthesized by the prevailing method. Moreover, the developed catalyst is recyclable after the regeneration of the deactivated zeolite by calcination at high temperatures. Therefore, it is anticipated that the currently developed Ti-MWW might be industrially applicable in the one-pot synthesis of EG from ethylene with H2O2.
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