This invention relates to a new method to manufacture molecular sieves and more particularly to a new method to manufacture crystalline borosilicate AMS-1B molecular sieve and to a product made from that method.
Zeolitic materials, both natural and synthetic, are known to have catalytic capabilities for many hydrocarbon processes. Zeolitic materials typically are ordered porous crystalline aluminosilicates having a definite structure with cavities interconnected by channels. The cavities and channels throughout the crystalline material generally are uniform in size allowing selective separation of hydrocarbons. Consequently, these materials in many instances are known in the art as "molecular sieves" and are used, in addition to selective adsorptive processes, for certain catalytic properties. The catalytic properties of these materials are affected to some extent by the size of the molecules which selectively penetrate the crystal structure, presumably to contact active catalytic sites within the ordered structure of these materials.
Generally, the term "molecular sieve" includes a wide variety of both natural and synthetic positive-ion-containing crystalline zeolite materials. They generally are characterized as crystalline aluminosilicates which comprise networks of SiO.sub.4 and AlO.sub.4 tetrahedra in which silicon and aluminum atoms are cross-linked by sharing of oxygen atoms. The negative framework charge resulting from substitution of an aluminum atom for a silicon atom is balanced by positive ions, for example, alkali-metal or alkaline-earth-metal cations, ammonium ions, or hydrogen ions.
Boron is not considered a replacement for aluminum or silicon in a zeolitic composition. However, recently a new crystalline borosilicate molecular sieve AMS-1B was disclosed in U.S. Pat. Nos. 4,268,420 and 4,269,813 incorporated by reference herein. According to these patents AMS-1B can be synthesized by crystallizing a source of an oxide of silicon, an oxide of boron, an oxide of sodium and an organic template compound such as a tetra-n-propylammonium salt. In order to form a catalytically-active species of AMS-1B, sodium ion typically is removed by one or more exchanges with ammonium ion followed by calcination. Other methods to produce borosilicate molecular sieves include using a combination of sodium hydroxide and aqueous ammonia together with an organic template as disclosed in U.S. Pat. No. 4,285,919, incorporated herein by reference, and using high concentrations of amine such as hexamethylenediamine as described in German Patent Application 28 30 787. British Patent Application 2,024,790 discloses formation of a borosilicate using ethylene diamine with sodium hydroxide. Aluminosilicates have been prepared with low sodium content using diamines containing four or more carbon atoms as described in European Published Patent Applications 669 and 11 362. U.S. Pat. Nos. 4,139,600 and 4,151,189 describe methods to produce aluminosilicate sieves containing low sodium using diamines or C.sub.2 -C.sub.5 alkyl amines.
A method to produce AMS-1B crystalline borosilicate molecular sieve which is low in sodium would be desirable in that an exchange procedure to remove sodium would be unnecessary. Also a method to produce AMS-1B crystalline borosilicate having a higher boron content than usually prepared by conventional techniques would be very advantageous. Further, a method to produce AMS-1B crystalline borosilicate without use of added alkali or ammonium hydroxides would be desirable. In addition a product formed from such method which shows increased activity over conventionally-prepared material would be most advantageous.
USPTO Backgrounds
USPTO Backgrounds