Enhancement of catalytic properties of interlayer-expanded zeolite Al-MWW via the control of interlayer silylation conditions

Treatment of the zeolitic layered precursor of Al-MWW, so-called Al-MWW(P), with diethoxydimethylsilane (DEDMS) in 1.0 M HNO3 media gave an aluminosilicate-type interlayer-expanded zeolite MWW (Al-IEZ-MWW) with expanded 12-membered ring (12-MR) micropores. By the interlayer-silylation of Al-MWW(P), the micropore diameter of interlayers with 12-MR supercages enlarged from ca. 7.0 to ca. 8.0 Å, verifying the formation of the interlayer-expanded structure. The interlayer-silylation of Al-MWW(P) under the acidic conditions with 1.0 M HNO3 caused the penetration of DEDMS molecules into the interlayers, resulting in the formation of monomeric silica puncheons between the MWW layers. Whereas the interlayer-silylation of Al-MWW(P) by using 1.0 M HNO3 caused remarkable dealumination of the MWW framework, the “two-step” silylation, namely, the first silylation in 0.1 M HNO3 and the following silylation in 1.0 M NH3, gave Al-IEZ-MWW retaining most of framework Al. The obtained Al-IEZ-MWW showed a high catalytic activity in the Friedel–Crafts acylation of anisole with acetic anhydride compared to Al-MWW as well as zeolite beta, suggesting that Al-IEZ-MWW is a useful candidate as a solid acid catalyst for the acylation reactions and other acid-catalyzed reaction of bulky molecules.

Figure optionsDownload as PowerPoint slideHighlights
► The interlayer silylation of Al-MWW layered precursor gave Al-IEZ-MWW with 12-MR.
► The “two-step” silylation gave Al-IEZ-MWW retaining most of framework Al.
► The Al-IEZ-MWW showed high catalytic activity in Friedel–Crafts acylation of anisole.