Process for inserting silicon into zeolite frameworks
AssigneeUop LLC
InventorsGary W. Skeels, Diane M. Chapman-Snyder, Edith M. Flanigen
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Abstract
The removal of aluminum and silicon atoms from the framework of crystalline zeolites and the reinsertion of at least some of the removed silicon atoms into the sites vacated by extracted aluminum atoms is accomplished by the process of contacting the zeolite with an aqueous solution of a bifluoride salt, preferably ammonium bifluoride. The treated zeolites have higher crystal destruction temperatures than their precursor starting zeolites.
Claims12
A process for increasing the Si/Al.sub.2 molar ratio and the thermal stability of a crystalline zeolite which comprises contacting and reacting a zeolite starting composition with a solution or slurry of a bifluoride salt in proportions such that there is from about 0.5 to 10 moles of bifluoride ion per mole of zeolitic framework aluminum, said contact between zeolite and bifluoride salt solution or slurry carried out at a temperature of from about 60.degree. C. to 100.degree. C. and the starting pH of the bifluoride salt solution being not greater than 7, whereby framework silicon and aluminum atoms are removed from the zeolite and at least some of the removed silicon atoms are inserted into sites vacated by removed aluminum atoms and the product zeolite has a crystal collapse temperature higher than that of the starting zeolite.
Dependencies are inferred from the claim text.