Synthesis, characterization and catalytic activity of the pillared molecular sieve MCM-36

MCM-36 materials were prepared by swelling the layered MCM-22 precursors wi th large organic molecules and then pillaring the resulting material with p olymeric silica. A mesopore region with 0.25-0.3 nm thickness between the m icroporous layers was identified. The BET surface area obtained for MCM-36 was 2.5 to 3 times higher than that of MCM-22. The sorption characteristics of linear alkanes are similar for MCM-22 and MCM-36 materials, indicating that sorption is dominated by the 10-membered ring microporous channel syst em and that the pore structure of the MCM-22 layers stays intact during the swelling and pillaring processes. Swelling and pillaring, however, decreas ed the concentration of Bronsted acid sites compared with the starting mate rial. The largest fraction of strong Bronsted acid sites is located in this zeolite layer. Adsorption of 2,2,4-trimethylpentane indicates that only ab out 10% of the bridging hydroxyl groups are located in the mesoporous regio n. The superior catalytic performance of MCM-36 compared with MCM-22 for al kylation of isobutane with n-butene indicates that the open mesoporous stru cture can be successfully utilized to make acid sites of the layers accessi ble to large molecules. (C) 1998 Elsevier Science B.V. All rights reserved.