Stable high-temperature borohydride formulation
A stabilized aqueous mixture containing at least one borohydride compound and at least one metal hydroxide compound. The mixture has improved stability with regard to decomposition of borohydride, especially at elevated temperatures.
1. An aqueous mixture comprising:
(a) from 15 wt. % to 65 wt. % of at least one borohydride compound;
(b) from 1 wt. % to 10 wt. % of at least one metal hydroxide; and
(c) from 0.1 wt. % to 20 wt. % of at least one absorbent polymer or excipient.
2. The aqueous mixture of claim 1 in which said at least one borohydride compound is sodium borohydride, potassium borohydride or a combination thereof, and said at least one metal hydroxide is sodium, lithium or potassium hydroxide, or a combination thereof.
3. The aqueous mixture of claim 2 in which said at least one absorbent polymer or excipient is selected from among water-soluble polymers, cellulose and its derivatives and cross-linked polymers.
4. The aqueous mixture of claim 3 in which the borohydride compound is sodium borohydride and the metal hydroxide is sodium hydroxide.
5. The aqueous mixture of claim 4 having from 2 wt. % to 8 wt. % sodium hydroxide and from 20 wt. % to 50 wt. % sodium borohydride.
6. The aqueous mixture of claim 5 in which said at least one absorbent polymer or excipient is polyacrylic acid or a copolymer of acrylic acid having at least 50% acrylic acid monomer units.
7. The aqueous mixture of claim 6 having from 0.1 wt. % to 1 wt. % polyacrylic acid or acrylic acid copolymer, and in which weight average molecular weight of the polyacrylic acid or copolymer of acrylic acid is at least 1500.
8. A method for stabilizing an aqueous borohydride mixture containing from 15 wt. % to 65 wt. % of at least one borohydride compound and from 1% to 10 wt. % of at least one metal hydroxide; said method comprising adding from 0.1 wt. % to 20 wt. % of at least one absorbent polymer or excipient.
9. The method of claim 8 said at least one metal hydroxide is sodium hydroxide and said at least one borohydride compound is sodium borohydride.
10. The method of claim 9 in which the aqueous borohydride mixture has from 2 wt. % to 8 wt. % sodium hydroxide and from 20 wt. % to 50 wt. % sodium borohydride.