Applied Catalysis A: General, Vol.491, 78-85, 2015
Ti-rich TS-1: A highly active catalyst for epoxidation of methallyl chloride to 2-methyl epichlorohydrin
Ti-rich TS-1 showed high catalytic activity and H2O2 efficiency for epoxidation of methallyl chloride (MAC). Unexpectedly, it was much more active in tert-butyl alcohol (TBA) solvent than in methanol and acetonitrile partially because TBA increased the adsorption amount of MAC in the channel of Ti-rich TS-1, and consequently enhanced the MAC concentration around the Ti sites. By optimizing reaction conditions, the MAC conversion reached 85.4% with epoxide selectivity of 96.7%, which could be maintained by regenerating the catalyst by calcination. Addition of alkali or salt into the reaction system or impregnation of these materials on the Ti-rich TS-1 led to a drastic decrease in activity. In combination with NH3-TPD and diffuse reflectance UV-vis spectroscopy results, it was found that active Ti-OOH (eta(2)) intermediates were formed for framework tetrahedral Ti species with moderately strong Bronsted acidity. This indicates that an Eley-Rideal-type reaction mechanism probably dominated the MAC epoxidation over Ti-rich TS-1. (C) 2014 Elsevier B.V. All rights reserved.