Dimethylacetals of ketones; cyclohexanone, acetophenone,
and benzophenone have been prepared by reacting
ketones with methanol under mild reaction conditions.
Large pore zeolites (H-Y and its rare earth metal, Ce3+, La3+,
and RE3+ modified forms), and mesoporous clay (K-10
montmorillonite and its cerium exchanged counterpart) with
regular pore structure, silica and silica-alumina have been
used as catalysts. Clay catalysts are found to be much more
active than zeolites, thanks to slightly bigger pore size. The
nature of the pores of the solid acid catalysts determine acetalization
efficiency of a particular catalyst. As evidenced
by the reaction time studies, the catalyst decay is greater
over the zeolites than over the clays. Carrying out the reaction
with ketones of different molecular sizes it is shown
that K-10 clays and rare earth exchanged H-Y zeolites are
promising environmentally friendly catalysts for their use in
the production fine chemicals.
One-pot acetalizations of cyclohexanone. acetophenone and benzophenone were carried out using methanol over H-montmorillonite clay
(a mesoporous material). silica, alumina, and different zeolites such as HFAU-Y.HBeta, H-ZSM-5, and H-mordenite. In all the cases a single
product-the corresponding dimethylacetal-was obtained in high yields. Hemiacetal formation was not observed with any catalyst. A
comparison of catalytic activity indicated that montmorillonite K-10 is the most active catalyst for the reaction. As evidenced by the reaction
time studies, the catalyst decay is greater over the zeolite catalyst than over the clay.