Acidic and catalytic properties of MCM-22 and MCM-36 zeolites synthesized from the same precursors Original Research Article

Samples of MCM-22 and MCM-36 (the pillared MCM-22 analog), synthesized from the same precursors were characterized by various techniques: XRD, N2 adsorption, pyridine and 2,4-dimethylquinoline adsorption followed by IR spectroscopy, m-xylene transformation at 350 °C in absence or in presence of 2,4-dimethylquinoline. The MCM-36 samples were shown to present sinusoidal channels, mesopores and/or supermicropores containing cups but also a small amount of undesired supercages. The method previously developed to estimate the activity and selectivity of the three MCM-22 pore systems (sinusoidal channels, supercages and external cups) was adapted to the characterization of the MCM-36 pore systems. Pillaring causes a large change in the distribution of the activity: approximately 15% of m-xylene transformation occurs in the inner micropores of the synthesized MCM-36 against more than 70% in the corresponding MCM-22 sample. Hence, 85% of the activity of MCM-36 (against 30% in MCM-22) is due to the protonic sites located in cups which are accessible to bulky molecules.