Method of synthesizing aluminophosphate and silicoaluminophosphate molecular sieves
View Patent ↗In a method of synthesizing an aluminophosphate or silicoaluminophosphate molecular sieve, a synthesis mixture is prepared by mixing a plurality of starting materials including at least a source of water, a source of phosphorus, a source of aluminum, optionally, a source of silicon and, and at least one organic directing agent for directing the formation of said molecular sieve. The starting materials are maintained at a temperature between 25° C. and 50° C., preferably between 30° C. and 45° C., during the mixing and until preparation of the starting mixture is complete, whereafter the synthesis mixture is heated to a crystallization temperature between about 100° C. and about 350° C. until crystals of the molecular sieve are produced. When crystallization is complete, the molecular sieve is recovered.
1. A method of synthesizing an aluminophosphate or silicoaluminophosphate molecular sieve, the method comprising:
(a) (i) mixing at least a source of water, and a source of aluminum with a source of phosphorus to form a synthesis mixture; (ii) adding a source of silicon to the synthesis mixture, and (iii) adding at least one organic directing agent to the synthesis mixture;
(b) maintaining the synthesis mixture at a temperature between 29° C. and 44° C. from the moment the source of phosphorus is completely added into the synthesis mixture;
(c) heating the synthesis mixture to a crystallization temperature between about 100° C. and about 350° C. until crystals of the molecular sieve are produced; and
(d) recovering the molecular sieve crystals.
2. The method of claim 1 , and including cooling at least some of the synthesis mixture during at least part of the mixing (a).
3. The method of claim 1 , wherein the crystallization temperature is between about 125° C. and about 270° C.
4. The method of claim 1 , wherein the crystallization temperature is between about 150° C. and about 200° C.
5. The method of claim 1 , wherein the synthesis mixture is agitated during (a) and (b).
6. The method of claim 1 , wherein the synthesis mixture is agitated during the heating (c).
7. The method of claim 1 , wherein the particle size distribution of the molecular sieve crystals is such that the (d90- d10)/d50 ratio is less than would be obtained by allowing the temperature to drop below 25° C. or to exceed 50° C. during the mixing (a).
8. The method of claim 1 , wherein the particle size distribution of the molecular sieve crystals is such that the (d90- d10)/d50 ratio is less than 1 .
9. The method of claim 1 , wherein the molecular sieve crystals have an average, D50, particle size of less than 3 microns.
10. The method of claim 1 , wherein the aluminophosphate or silicoaluminophosphate comprises a CHA framework-type molecular sieve.
11. The method of claim 1 , wherein the volume of the synthesis mixture is less than 2 liters.