Desenvolvimento de zeólitas do tipo MCM-22 destinadas a serem utilizadas como aditivos em catalisadores de FCC.

Abstract

The additives are introduced in the FCC catalyst to crack the heavy hydrocarbons, to increase the gasoline octane number and/or to form lighter olefins. The MCM-22 zeolite, due to its framework form, when used like additive it can be compared with the ZSM-5 zeolite. The MCM-22 zeolite was synthesized preparing initially, the precursor materials, through two different hydrothermal treatments, dynamic and static ones. The precursors were characterized by XRD, EDX, TG/DrTG and FTIR, and they were calcined, in oven muffle to 650 ºC being obtained the (Na-MCM-22) zeolites, which they were characterized by XRD, EDX and SEM. To obtain the zeolite in the acid form (H-MCM-22) it was realized an ionic exchange with the ammonium chloride (NH4Cl) and, subsequent, calcination under N2 and synthetic air flow at 500 ºC. These zeolites were characterized by Physical Adsorption of N2 (B. E. T. Method) and n-hexane cracking model reaction. Tests of hydrothermal deactivation were realized in muffle to 800 ºC for 5 hours in a rich atmosphere in water steam The results obtained by XRD, EDX, TG/DrTG and FTIR, showed that, independent of the kind of the hydrothermal treatment used, the characteristics were similar. The micrographs presented some differences in relation to the morphology of the formed particles, due the kind of the hydrothermal treatment used. Through the results of Physical Adsorption of N2 (B.E.T. method) it was possible to verify that the H-MCM-22 zeolite obtained by the dynamic method presented textural characteristics superior to HMCM- 22 zeolite obtained by the static method. The tests realized by the n-hexane cracking model reaction revealed that the not deactivated samples of the H-MCM-22 zeolite, obtained by the dynamic and static methods, presented higher global conversions in relation to the hydrothermally deactivated samples in muffle to 800 ºC for 5 hours in a rich atmosphere in water steam, indicating the degenerative action of the dealumination. With base in the deactivation tests was possible to conclude that the MCM-22 zeolites, obtained through the dynamic and static methods, presented good hydrothermal stability indicating to be promising materials to be used like additives in FCC catalysts.