Swelling of MCM-56 and MCM-22P with a new medium — surfactant–tetramethylammonium hydroxide mixtures

Two different types of layered MWW zeolite, i.e., delaminated MCM-56 and multilayer MCM-22P, have been studied for swelling using a new surfactant/tetraalkylammonium combination as the swelling reagent. The commonly used in the past tetrapropylammonium hydroxide (TPA-OH) was replaced by its tetramethylammonium (TMA-OH) homologue. The latter was previously considered unsuitable for use in swelling of MCM-22P. The extent of swelling with different amounts of TMA-OH accompanying surfactant was determined first by X-ray diffraction. Selected samples were pillared with silica and evaluated quantitatively by nitrogen sorption at 77 K and FTIR. The swelling of MCM-56, which is reported in detail for the first time, has been found to be more facile and extensive compared to the multi-layer MCM-22P, consistent with its delaminated nature. BET surface areas of pillared MCM-56 samples increase with the amount of hydroxide used for swelling and approach 700 m2/g. Pillared MCM-22P show similar trend but have somewhat lower BET values than pillared MCM-56. The observed successful swelling of MCM-22P is notable because the presence of small cations was previously found to be unfavorable for this process. FTIR measurements of selected samples confirmed higher Al/acid center content in pillared MCM-56 products in comparison to MCM-22 ones. Compared to unmodified MCM-22, there was an increase in most cases in the concentration of acid sites interacting with di-tert-butyl-pyridine. This confirms increased access of larger molecules to acid sites, which is the main goal of such swelling/pillaring treatments.