Characterisation by adsorption of various organic vapours of the porosity of fresh and coked H-MCM-22 zeolites

The microporosity of H-MCM-22 samples, fresh and deactivated by coke during methylcyclohexane transformation at 350 degrees C for 10 h, was characterised by adsorption of nitrogen and organic molecules of different size, namely, p- and o-xylenes, mesitylene and methylcyclohexane. Nitrogen adsorption was also carried out on the fresh sample after pre-adsorption of the hydrocarbons. All of these can fit the outer 12 MR Cups, but show differences in their ability to enter the internal microporosity. p-Xylene can enter all the inner micropores, methylcyclohexane adsorbs in the supercages and at some sinusoidal channel entrances, o-xylene is adsorbed at the pore windows of the supercages only, and mesitylene is completely excluded from the inner micropores. it was deduced that the microporosity of the MCM-22 sample investigated consists of 0.01 cm(3) g(-1) of outer pockets (similar to 5% of the total volume), 0.06 cm(3) g(-1) of sinusoidal channels (similar to 32%) and 0.12 cm(3) g(-1) of supercages (similar to 63%). Coke deposited during methylcyclohexane transformation caused the complete blockage of the supercages but had no effect on the outer cups and sinusoidal channels. (C) 2008 Elsevier Inc. All rights reserved.