Zeolite modification

DETAILED DESCRIPTION AND SPECIFIC EMBODIMENTS The high silica content zeolite treated by the method of this invention is of the ZSM-5 type, exemplified by ZSM-5, ZSM-11, ZSM-12, ZSM-23, ZSM-35, ZSM-38 and ZSM-48, as more fully described hereinbelow.
The treatment is conducted with a physical mixture of the zeolite and a solid source of aluminum.
The solid source of aluminum, which is believed to furnish the aluminum for insertion into the robust framework of the zeolite, may be in the form of discrete beads of alumina, or it may be present as the alumina binder in an extrudate formed from a mixture of the zeolite and alpha alumina monohydrate, for example.
Both of the foregoing variants exemplify physical mixtures for purposes of the present invention.
The proportions of the zeolite and solid source of aluminum are not believed to be critical, and the physical mixture may contain 1 wt% to 99 wt%, preferably 15 wt% to 85 wt% of the solid source of aluminum.
It has been observed that an intimate mixture, such as provided by an extrudate, activates more readily compared with a less intimate mixture such as that provided by discrete alumina beads, but both are effective.
It is a feature of this invention that discrete alumina beads may be used to treat a zeolite either incorporated with or to be incorporated with an alumina-free binder.
Although the preferred solid source of aluminum is an alumina, one skilled in the art will recognize that other solids comprising alumina may be used.
Such solids which may be used, either with or without prior treatment, include silica-alumina gels, clays such as attapulgite, montmorillonite, alumina hydrosols, and Dixie and Mac Namee clays.
For purposes of the method of this invention, the solid source of aluminum, such as an alumina, may be the sole source of aluminum.
The activation method of this invention is exceedingly simple.
The physical mixture of ZSM-5 type zeolite and solid source of aluminum is treated with liquid water at a temperature below its critical temperature, i