Organically modified titanium-rich Ti-MCM-41, efficient catalysts for epoxidation reactions

Highly ordered, titanium-rich organically modified Ti-MCM-41 materials have been synthesized at 413 K using a mixture of organo-triethoxysilane and te traethyl orthosilicate, Various organic substituents on Ti-MCM-41 used in t he present study are methyl, vinyl, allyl, 3-chloropropyl, pentyl, and phen yl. The highest amount of Ti incorporated for a given Si/Ti mole ratio of 3 0 in the synthesis gel was 33.6 in the case of the 3-chloropropyl group. Fo r methyl, vinyl, allyl, pentyl, and phenyl this ratio varied from 42 to 53, which is considerably lower than for unmodified Ti-MCM-41 reported earlier . Whereas incorporation of short chain organic functionality (C-1-C-3) caus es an increase in the d spacing, resulting in wider pore openings, long cha in (pentyl) and aromatic (phenyl) substituents cause a decrease in d spacin g in these mesoporous molecular sieves. An increase in the organic content in the synthesis gel beyond a certain level also causes a decrease in d spa cing. N-2 and H2O adsorption studies revealed that these organically modifi ed well ordered Ti-MCM-41 materials are more hydrophobic than that synthesi zed in the absence of organic modifiers. These organically modified Ti-MCM- 41 materials are efficient catalysts in the epoxidation reaction of unsatur ated alcohols followed by cyclization to cyclic ethers using TBHP as oxidan t. (C) 2000 Academic Press.