PROCESSES FOR OXIDATION OF BROMIDES TO PRODUCE BROMINE AND CATALYSTS USEFUL THEREIN

Abstract

Methods are provided for producing bromine wherein an aqueous solution is formed from at least a bromide source, an oxidant, and a catalyst comprising a Group 1 cation and an oxide of a transition metal

Description

EXAMPLES

The following examples are illustrative of the principles of this invention. It is understood that this invention is not limited to any one specific embodiment exemplified herein.

Example 1

HBr (357.20 g of 7.46 wt % aqueous solution; 0.33 mol HBr) and Na₂MoO₄ (2.04 g of 4 wt % aqueous solution; 0.4 mmol Na₂MoO₄) were added into a 500 mL Erlenmeyer flask along with HCl (16.08 g of 12M HCl; 0.13 mol HCl) and H₂O₂ (2.84 g of 70 wt % aqueous solution; 0.06 mol H₂O₂). The mixture was stirred, cooled, and kept at 15-20° C. during addition at 10 mL/min into the reflux stream above a 12″×1″ column fitted with 24/40 glassware into a 500 mL three-necked round bottomed-flask into which live steam was injected. Excess condensate and HBr were removed by pump and the overhead products, comprising bromine and water, were condensed using a Friedrich's condenser cooled with aqueous glycol at 4-7° C. This condensate and any uncondensables were conveyed into 300 mL (15 wt %) Na₂SO₃ solution where the bromine was reduced into bromide ion and quantified by titration with 0.1N AgNO₃. A total of 9.27 g bromine was obtained; a H₂O₂-based bromine yield of 99.04 wt %.

Example 2

The procedure of Example 1 was used with HBr (356.77 g of 8.96 wt % aqueous solution; 0.40 mol HBr), HCl (11.40 g of 12M HCl; 0.09 mol HCl), Na₂MoO₄ (3.09 g of 4 wt % aqueous solution; 0.6 mmol Na₂MoO₄), and H₂O₂ (2.91 g of 70 wt % aqueous solution; 0.06 mol H₂O₂). A total of 8.99 g bromine was obtained; a H₂O₂-based bromine yield of 93.91 wt %.

Example 3

Comparative Example

The procedure of Example 1 was used with HBr (356.54 g of 7.52 wt % aqueous solution; 0.33 mol HBr), HCl (17.90 g of 12M HCl; 0.15 mol HCl), and H₂O₂ (2.80 g of 70 wt % aqueous solution; 0.06 mol H₂O₂). No catalyst according to this invention was added. A total of 7.32 g bromine was obtained; a H₂O₂-based bromine yield of 79.38 wt %.

Example 4

Comparative Example

The procedure of Example 1 was used with HBr (360.80 g of 6.19 wt % aqueous solution; 0.28 mol HBr), HCl (19.27 g of 12M HCl; 0.16 mol HCl), and H₂O₂(3.39 g of 70% wt aqueous solution; 0.07 mol H₂O₂) added into the feed HBr. No catalyst according to this invention was added. A total of 5.19 g bromine was obtained; a H₂O₂-based bromine yield of 46.43 wt.

Example 5

Comparative Example

The procedure of Example 1 was used with HBr (355.68 g of 7.46 wt % aqueous solution; 0.33 mol HBr), HCl (159.02 g of 30 wt % aqueous solution; 1.14 mol HCl), and H₂O₂ (2.65 g of 70 wt % aqueous solution; 0.06 mol H₂O₂). No catalyst according to this invention was added. A total of 8.30 g bromine was obtained; a H₂O₂-based bromine yield of 95.09 wt %.

Example 6

Comparative Example

The procedure of Example 1 was used with HBr (356.65 g of 17.20 wt % aqueous solution; 0.76 mol HBr), HCl (22.04 wt % by titration; 46.10 g (0.28 mol) HCl), and H₂O₂ (14.98 g of 70 wt % aqueous solution; 0.31 mol H₂O₂); in addition, a recycle acid source was used. No catalyst according to this invention was added. A total of 45.65 g bromine was obtained; a H₂O₂-based bromine yield of 92.50 wt %.

As can be see from these examples (data summarized in Table 1), use of a catalyst of this invention in a bromine oxidation reaction improves Br₂ yield. Compare the oxidation reaction of Example 3, where 0.33 mol HBr were oxidized using 0.15 mol HCl and 0.06 mol H₂O₂, resulting in a H₂O₂-based Br₂ yield of 79.38 wt %, to the reaction of Example 1, where 0.33 mol HBr were oxidized using 0.13 mol HCl 0.06 mol H₂O₂, and 0.4 mmol of a catalyst according to this invention (Na₂MoO₄), resulting in a H₂O₂-based Br₂ yield of 99.04 wt % (vs. the 79.38 wt % yield of Example 3). Also compare Example 3 to Example 2, where slightly less HCl was used (0.09 mol vs. 0.15 mol), and 0.6 mmol of a catalyst according to this invention (Na₂MoO₄) was used, resulting in a H₂O₂-based Br₂ yield of 93.91 wt % (vs. the 79.38 wt % yield of Example 3). The Examples also show that increased amounts of HCl cam improve the effectiveness in a bromine oxidation reaction. For example, comparing Example 3 to Example 5, increasing HCl from 0.15 mol to 1.14 mols can result in increased oxidant-based bromine (Br₂) yield from 79.38 wt % to 95.09 wt %.

TABLE 1
					H2O2-based Br2
Example	HBr	HCl	H2O2	Na2MoO4	yield
Number	(mols)	(mols)	(mols)	(mmols)	(wt %)
1	0.33	0.13	0.06	0.4	99.04
2	0.40	0.09	0.06	0.6	93.91
3	0.33	0.15	0.06	—	79.38
4	0.28	0.16	0.07	—	46.43
5	0.33	1.14	0.06	—	95.09
6	0.76	0.28	0.31	—	92.50

While the present invention has been described in terms of one or more preferred embodiments, it is to be understood that other modifications may be made without departing from the scope of the invention, which is set forth in the claims below.

Claims

1. A method for producing bromine comprising forming an aqueous solution from at least a bromide source, an oxidant, and a catalyst comprising a Group 1 cation and an oxide of a transition metal.

2. A method according to claim 1 wherein the Group 1 cation comprises Na+ or K+.

3. A method according to claim 1 wherein the oxide comprises molybdate (MoO4−2).

4. A method according to claim 1 wherein the catalyst comprises sodium molybdate (Na2MoO4).

5. A method according to claim 1 wherein the bromide source comprises hydrogen bromide or sodium bromide.

6. A method according to claim 1 wherein the oxidant comprises hydrogen peroxide (H2O2), chlorine (Cl2), or oxygen (O2).

7. A method according to claim 4 wherein the molar ratio of bromide source to catalyst is from about 150:1 to about 1200:1.

8. A method comprising: (i) forming an aqueous solution from at least a bromide source, an oxidant, a mineral acid, and a catalyst comprising a Group 1 cation and an oxide of a transition metal, wherein the aqueous solution has a pKa of less than about −1.74; and(ii) producing bromine.

9. A method for producing bromine comprising forming an aqueous solution from at least hydrogen bromide, sodium molybdate, hydrogen peroxide and HCl.

10. A method for producing bromine comprising forming an aqueous solution from at least a bromide source, an oxidant, a mineral acid, and a catalyst composing a Group 1 cation and an oxide of a transition metal.