HK1130460B - Processes for oxidation of bromides to produce bromine and catalysts useful therein - Google Patents

Description

Method for preparing bromine by oxidizing bromide and catalyst used therein

Background

Bromine is widely used in industrial fields. For example, bromine is used in the manufacture of a fire retardant, 1, 2-dibromoethane (CH)₂BrCH₂Br) (which is used in gasoline additives to prevent lead precipitation in the cylinder); compounds used for photography (e.g., silver bromide, AgBr, which is a photosensitive substance in film), dyes, and drugs; in an analytical laboratory for detecting the unsaturation of organic compounds, in which bromine is added to the multiple bonds of unsaturated compounds; as a disinfectant; and in the production of fumigants, water purification compounds, dyes, pharmaceuticals; and a sanitizer. Bromine can be prepared by oxidizing bromide using hydrogen peroxide as an oxidizing agent. For example, the following reactions are suitable: h₂O₂+2HBr→Br₂+2H₂O (reaction (1)). Bromine can also be prepared by oxidizing bromides using chlorine as the oxidizing agent. For example, the following reactions are suitable:(reaction (2)).

US 5,266,295 describes the use of strong acids, such as sulphuric or phosphoric acid, to improve efficiency when hydrogen bromide is oxidised to bromine using hydrogen peroxide as the oxidant. However, the addition of acid affects the economics of the manufacturing process, and in some cases the acid source is not readily available. Either of reactions (1) and (2) can benefit from increasing the conversion of bromide to bromine by the addition of a catalyst. Ammonium molybdate ((NH)₄ ⁺)₂MoO₄ ^-) Is a well-known oxidation catalyst and can be titrated for H using iodometry₂O₂. However, NH in commercial bromine column units₄ ⁺And cannot be used as a choice of cations in the additive.

Thus, in view of the presently available technology, there remains a need for commercially viable processes for increasing the conversion of bromides to bromine, and for catalysts useful therein.

Disclosure of Invention

The present invention fulfills the above needs by providing a process for producing bromine comprising forming an aqueous solution from at least a bromine source, an oxidant, and a catalyst comprising a group 1 cation and an oxygenate of a transition metal. Further, a process is provided comprising (i) forming an aqueous solution from at least a bromine source, an oxidizing agent, an inorganic acid, and a catalyst comprising a group 1 cation and a transition metal oxide, said aqueous solution having a pKa of less than about-1.74; and (ii) preparation of bromine. Also provided is a process for producing bromine comprising forming an aqueous solution from at least a bromine source, an oxidizing agent, hydrogen chloride, and a catalyst according to the invention. The process according to the invention can be carried out in a continuous manner or batchwise. The invention also provides a process for producing bromine wherein the aqueous solution has a pKa of less than about-1.74.

Catalyst and process for preparing same

The catalyst used in the process according to the invention comprises a cation of main group 1 and an anion comprising a transition metal anion. The group 1 cation may comprise Na⁺，K⁺，Rb⁺，Cs⁺，Fr⁺，Li⁺Or H⁺. The anion may comprise an oxide derived from one or more transition metals such as vanadium, cerium, chromium, manganese, niobium, molybdenum, ruthenium, tungsten, rhenium, and/or osmium. For example, the anion may comprise MoO₄ ^-2. An example of a catalyst according to the invention comprises sodium molybdate (Na)₂MoO₄). Catalysts comprising transition metal oxide anions that promote the decomposition of hydrogen peroxide are useful in the process of the present invention because the anions in the catalyst activate hydrogen peroxide in the direction of oxidizing bromide, thus yielding at least 90% (or at least 95% or 98%) by weight bromine based on hydrogen peroxide.

Bromine source

In the process of the present invention, the bromine source may comprise hydrogen bromide (HBr) or sodium bromide (NaBr). The HBr can be generated from in situ decomposition of less stable (e.g., secondary and tertiary) aliphatic alkyl bromides. Other suitable bromine sources include potassium bromide (KBr) and lithium bromide (LiBr). Another bromine source suitable for the present invention includes aqueous hydrobromic acid, hydrogen bromide gas, or a group 1 metal bromide in combination with hydrochloric acid. The group 1 metals include lithium (Li), sodium (Na), and potassium (K).

Oxidizing agent

In the method of the present invention, the oxidizing agent may comprise hydrogen peroxide (H)₂O₂) Chlorine (Cl)₂) Or oxygen (O)₂). The oxidizing agent may comprise a salt of hydrogen peroxide, for example, lithium peroxide. Chlorine as the oxidant may be introduced as a gas or generated in situ from chloride ions and peroxide, including hydrogen peroxide. Oxygen, an economically beneficial bromide oxidizing agent, generally requires temperatures above room temperature for activation and can be used in gaseous form. Can be used forOxygen transporters such as cerium oxide or vanadium pentoxide are used. Other suitable oxidizing agents include organic peroxides, for example, benzoyl peroxide, which decompose upon heating.

Inorganic acid

In the process of the present invention, the mineral acid may increase the acidity of the aqueous solution formed. Suitable inorganic acids include hydrochloric acid, sulfuric acid and/or phosphoric acid.

Oxidation of bromide to bromine

Oxidation of bromide to bromine according to the present invention typically produces bromine in a continuous system with hydrogen peroxide as the oxidant in a commercial packed column environment with the addition of reactants and steam, however, variations can be made by those skilled in the art.

The bromine provided herein can be derived from about 0.01 wt.% to about 60 wt.% HBr, about 3 wt.% to about 70 wt.% H₂O₂About 0.03 wt% to about 0.5 wt% of the catalyst according to the invention and about 5 wt% to about 20 wt% of HCl, all based on HBr, H prior to use in the preparation of bromine₂O₂The total weight of catalyst and HCl. Typically, the bromine source, oxidant and catalyst, and when present hydrogen chloride or mineral acid, are in aqueous solution. The present invention also provides that the molar ratio of bromine source to catalyst according to the present invention is from about 150: 1 to about 1200: 1, alternatively from about 200: 1 to about 1000: 1, alternatively from about 400: 1 to about 900: 1, alternatively from about 600: 1 to about 850: 1, alternatively from about 658: 1 to about 831: 1.

Examples

The following examples are illustrative of the principles of the present invention. It is to be understood that the invention is not limited to any one particular specific example illustrated herein.

Example 1: HBr (357.20g of 7.46% by weight aqueous solution; 0.33mol HBr) and Na were added₂MoO₄(2.04g of a 4% by weight aqueous solution; 0.4mmol of Na₂MoO₄) With HCl (16.08g of 12M HCl; 0.13mol HCl) and H₂O₂(2.84g of a 70% by weight aqueous solution; 0.06mol of H₂O₂) Were added together in a 500mL Erlenmeyer flask. The mixture was stirred, cooled and kept at 15-20 ℃ at 10mL/min was added to the reflux stream at the top of a 12 "X1" column fitted with 24/40 condenser (glass ware) into a 500mL three-necked round bottom flask filled with live steam. Excess condensate and HBr were removed by pump and the overhead product comprised bromine and water, which was condensed by a Friedrich's condenser cooled with aqueous ethylene glycol at 4-7 ℃. The condensate and any non-condensed material were transferred to 300mL (15 wt%) of Na₂SO₃In solution, bromine is reduced to bromide ions in the solution and 0.1N AgNO is used₃And (4) titration quantification. A total of 9.27g of bromine, based on H, are obtained₂O₂The yield of bromine was 99.04 wt%.

Example 2: the procedure of example 1 was followed using HBr (356.77g of 8.96% by weight in water; 0.40mol HBr), HCl (11.40g of 12M HCl; 0.09mol HCl), Na₂MoO₄(3.09g of a 4% by weight aqueous solution; 0.6mmol of Na₂MoO₄) And H₂O₂(2.91g of a 70% by weight aqueous solution; 0.06mol H₂O₂). A total of 8.99g of bromine, based on H, are obtained₂O₂The yield of bromine was 93.91 wt%.

Example 3 (comparative example): the procedure of example 1 was followed using HBr (356.54g of 7.52 wt.% aqueous solution; 0.33mol HBr), HCl (17.90g of 12M HCl; 0.15mol HCl), and H₂O₂(2.80g of a 70% by weight aqueous solution; 0.06mol of H₂O₂). Without addition of the catalyst according to the invention, a total of 7.32g of bromine, based on H, were obtained₂O₂The yield of bromine was 79.38 wt%.

Example 4 (comparative example): the procedure of example 1 was followed using HBr (360.80g of 6.19 wt% aqueous solution; 0.28mol HBr), HCl (19.27g of 12M HCl; 0.16mol HCl), and H₂O₂(3.39g of a 70% by weight aqueous solution; 0.07mol of H₂O₂) Added to the feed HBr. Without addition of the catalyst according to the invention, a total of 5.19g of bromine, based on H, were obtained₂O₂The yield of bromine was 46.43 wt%.

Example 5 (comparative example): the procedure of example 1 was followed using HBr (355.68g of 7.46% by weight aqueous solution; 0.33mol HBr), HCl (159.02g of 30% by weight aqueous solution; 1.14mol HCl), and H₂O₂(2.65g of a 70% by weight aqueous solution; 0.06mol of H₂O₂). Without addition of the catalyst according to the invention, a total of 8.30g of bromine, based on H, were obtained₂O₂The yield of bromine was 95.09 wt%.

Example 6 (comparative example): the procedure of example 1 was followed using HBr (356.65g of 17.20% by weight in water; 0.76mol HBr), HCl (22.04% by weight; 46.10g (0.28mol) HCl by titration), and H₂O₂(14.98g of a 70% by weight aqueous solution; 0.31mol of H₂O₂) (ii) a In addition, recycled acid sources are used. Without addition of the catalyst according to the invention, a total of 45.65g of bromine, based on H, were obtained₂O₂The yield of bromine was 92.50 wt%.

As seen in the above examples (data summarized in Table 1), the use of the catalyst of the present invention in the oxidation of bromine increases Br₂The yield of (a). Comparative example 3 Oxidation, in which 0.15mol HCl and 0.06mol H are used₂O₂Oxidation of 0.33mol HBr, results based on H₂O₂Br₂The yield of (3) was 79.38% by weight, whereas in the reaction of example 1, 0.13mol of HCl, 0.06mol of H were used₂O₂And 0.4mmol of the catalyst according to the invention (Na)₂MoO₄) Oxidation of 0.33mol HBr, results based on H₂O₂Br₂The yield of (a) was 99.04 wt% (yield of 79.38 wt% relative to comparative example 3). Also comparing example 3 with example 2, in example 2 the use of HCl (0.09mol versus 0.15mol) was slightly reduced and 0.6mmol of the catalyst according to the invention (N) was useda₂MoO₄) Results are based on H₂O₂Br₂The yield of (a) was 93.91 wt% (yield of 79.38 wt% relative to comparative example 3). The above examples also show that increasing the amount of HCl can increase the efficiency of the bromine oxidation reaction. For example, comparing example 3 to example 5, increasing HCl from 0.15mol to 1.14mol can result in bromine (Br) based oxidizing agent₂) The yield increased from 79.38 wt% to 95.09 wt%.

TABLE 1

Example numbering	HBr(mols)	HCl(mols)	H2O2(mols)	Na2MoO4(mmols)	Based on H2O2Br of2Yield of (1) (% by weight)
						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

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

Claims (5)

1. A method of making bromine comprising:

(i) forming an aqueous solution from at least a bromine source, hydrogen peroxide, an inorganic acid, and a catalyst comprising a group 1 cation and an anion comprising a transition metal anion, wherein the anion comprises MoO₄ ^-2Said aqueous solution having a pK of less than-1.74_a；

(ii) Passing the aqueous solution and steam through a packed column operating in a continuous manner; and

(iii) bromine is produced in a yield of at least 90 wt.% based on hydrogen peroxide.

2. The method of claim 1, wherein the group 1 cation comprises Na⁺Or K⁺。

3. The process of claim 1, wherein the catalyst comprises Na₂MoO₄。

4. The method of claim 1, wherein the bromine source comprises hydrogen bromide or sodium bromide.

5. The process according to claim 3, wherein the molar ratio of bromine source to catalyst is from 150: 1 to 1200: 1.