Sharif Digital Repository

A number of HZSM-5 catalysts modified with 5 wt% Mg, Na, Zr, and Al as well as others modified with 5-60 wt% Zn prepared by wet impregnation. These materials were characterized by the NH3-TPD, XRF, and XRD analyses and tested in a slurry reactor to determine their activities in dehydration of methanol solution in kerosene. Reactions were carried out at 230°C and 19 bar for 4 h of residence time in the reactor. Results showed that in the first series, the catalyst modified with Zr and in the second series, the one modified with 10 wt% Zn led to the highest methanol conversion. It was deduced that elimination of strong acid sites and partial replacement of active cations in the HZSM-5 zeolite... 

Faujasite (X, Y) zeolites are considered the main and important catalysts in hydrorefining processes. In order to obtain zeolites with higher acidity and volume of mesopores, post-synthesis modification, dealumination by different pickling techniques (using ethylenediamine tetraacetic acid [EDTA] chelating agent), and thermal treatment (calcination) were employed. The dealumination process led to the removal of the aluminum atoms from the zeolite structure and a rise in acidity while maintaining the zeolite crystalline lattice. X-ray diffraction (XRD), atomic absorption spectrometry (AAS), Fourier-transform infrared (FT-IR), field-emission scanning electron microscopy (FE-SEM),... 

In order to make a Na–Y zeolite with Si/Al ratio of 2.27 more acidic with a higher volume of mesopores, a combination of different and consecutive methods including; chemical (i.e.; utilizing different compounds, such as NH4F and EDTA) and thermal/hydrothermal (i.e.; implementing calcination/steaming) methods, were employed for modification and dealumination. The combination of acidic-hydrothermal dealumination method led to a further structural collapse compared to that of the acidic calcination. In comparison with the other dealumination methods, the fluorination strategy (i.e.; utilizing NH4F) resulted in a zeolite with higher crystallinity, acidity, and specific surface area. The...