Characterization and Catalytic Activity of MCM-22 and MCM-56 Compared with ITQ-2

MCM-22, MCM-56 and ITQ-2 zeolites, have been characterized by different physicochemical techniques (XRD, 29Si MAS NMR, IR, adsorption, and catalytic test), and they show that the first two are similar in structure and reactivity while ITQ-2 is different. The external surface area of the MCM-56 sample is somewhat larger than MCM-22, both being much smaller than ITQ-2. This is in agreement with the 15–20% larger adsorption capacity for 1,3,5-trimethylbenzene shown by MCM-56 with respect to MCM-22, and the seven times larger adsorption shown by ITQ-2. This is a consequence of a higher degree of disorder along the c axes in MCM-56 than in MCM-22. A similar type of disorder, i.e., the same XRD pattern than for MCM-56, was observed after adsorbing acetone on the laminar precursor of MCM-22. The external surface acidity of the three samples, as measured by 2,6 ditertbutylpyridine (26 DTBPy), follows the order ITQ-2>MCM-56>MCM-22 and this is reflected by the catalytic activity towards a large molecule (1,3,5-triisopropylbenzene) which can react only at the external surface (external cups) of these materials.