Characterization and catalytic properties of hydrothermally dealuminated MCM-22

MCM-22 has been synthesized and dealuminated by hydrothermal treatments. Th e resulting solids were characterized by different techniques in order to k now how the acid properties of the dealuminated solids were modified. It ap pears that the number of acid sites was decreased by hydrothermal treatment s but the acid strength was not modified. Nondealuminated and dealuminated solids were used in the n-octane hydroconversion. Results suggested that fo r both types of solids the hydroisomerization is mainly occurring in the 10 -membered ring (MR) channels whereas the hydrocracking is mainly coming fro m acid sites located in 12-membered ring channels. According to the observe d distribution of monobranched isomers, MCM-22 shows some "shape-selective" character typical of the pentasil family, whereas, according to the absolu te yield of isopentane in the hydrocracked products at low hydrocracking co nversions, "MCM-22 behaves more like a 12 MR zeolite" (6). Similar conclusi ons were proposed in (7). (C) 1999 Academic Press.