阅读说明：本技术 用于通过蒽醌法生产过氧化氢的装置和方法 (Device and method for producing hydrogen peroxide by the anthraquinone method ) 是由 N·H·塞德尔 J·坎普 J·格伦艾伯格 C·潘茨 E·F·A·萨阿德 H·P·曼加拉帕利 于 2021-05-28 设计创作，主要内容包括：本发明公开了用于生产过氧化氢的循环蒽醌法,其包括用于浓缩过氧化氢的具有蒸气压缩的蒸馏单元,将来自蒸馏单元的水性冷凝物输送通过呈其质子化形式的阳离子交换树脂的床以提供经纯化的冷凝物,并且将经纯化的冷凝物用作蒽醌法中用于萃取过氧化氢的萃取剂、用作蒸馏单元的塔回流、或用作稀释过氧化氢水溶液的稀释剂。(A cyclic anthraquinone process for the production of hydrogen peroxide comprising a distillation unit with vapour compression for concentrating hydrogen peroxide, passing an aqueous condensate from the distillation unit through a bed of cation exchange resin in its protonated form to provide a purified condensate, and using the purified condensate as an extractant for extracting hydrogen peroxide in the anthraquinone process, as column reflux for the distillation unit, or as a diluent for diluting aqueous hydrogen peroxide.)

1. An apparatus for producing hydrogen peroxide by the anthraquinone process comprising:

a) a hydrogenator (2) for hydrogenating a working solution (1) comprising alkylanthraquinone and/or alkyltetrahydroanthraquinone and at least one water-immiscible solvent for said alkylanthraquinone and/or alkyltetrahydroanthraquinone with a gas (3) comprising molecular hydrogen in the presence of a hydrogenation catalyst to provide a hydrogenated working solution;

b) an oxidizer (4) for oxidizing the hydrogenated working solution with a molecular oxygen containing gas (5) to provide an oxidized working solution containing dissolved hydrogen peroxide, the oxidizer (4) being connected to the hydrogenator (2) to receive the hydrogenated working solution;

c) an extractor (7) for extracting hydrogen peroxide from an oxidized working solution containing dissolved hydrogen peroxide with an aqueous extractant (8) to provide a dilute aqueous hydrogen peroxide solution (9), the extractor (7) being connected to the oxidizer (4) to receive the oxidized working solution containing dissolved hydrogen peroxide.

d) A distillation unit for concentrating an aqueous hydrogen peroxide solution to provide a concentrated aqueous hydrogen peroxide solution (14) and an aqueous condensate (19), the distillation unit comprising a hydrogen peroxide evaporator (11), a distillation column (10) receiving vapour (13) from the hydrogen peroxide evaporator (11), and a vapour compressor (17) receiving overhead vapour (16) from the distillation column (10) and delivering compressed vapour (18) as a heating medium to the hydrogen peroxide evaporator (11), the distillation unit being connected to the extractor (7) to receive the dilute aqueous hydrogen peroxide solution (9); and

e) a purification unit comprising a bed (23) of cation exchange resin in its protonated form for purifying the aqueous condensate (19) to provide a purified condensate (26), the purification unit being connected to the distillation unit to receive the aqueous condensate (19) as a feed and (i) being connected to the extractor (7) to deliver the purified condensate (26) as an aqueous extractant (8) to the extractor (7), or (ii) being connected to the distillation unit to deliver the purified condensate (26) as a column reflux to the distillation column (10), or (iii) being connected to a hydrogen peroxide dilution device to deliver the purified condensate (26) as a diluent to the hydrogen peroxide dilution device, or (iv) being connected to any combination of (i) to (iii).

2. The apparatus according to claim 1, wherein the vapor compressor (17) of the distillation unit is a steam driven ejector.

3. The apparatus of claim 1 or 2, wherein the distillation unit comprises: a falling film evaporator as a hydrogen peroxide evaporator (11); a separation vessel (12) horizontally divided by a demister, connected to the falling film evaporator below the demister, to receive the vapor-liquid mixture provided by the hydrogen peroxide evaporator (11); a conduit connected to the separation vessel (12) above the demister for conveying vapor to the distillation column (10); and a recycle conduit for recycling liquid from the bottom of the separation vessel (12) to the falling film evaporator.

4. The device according to any one of claims 1 to 3, wherein the purification unit comprises a first filter (22) upstream of the bed (23) of cation exchange resin.

5. The device of any one of claims 1 to 4, wherein the cation exchange resin is a sulfonated polystyrene resin.

6. The device according to any one of claims 1 to 5, further comprising a buffer vessel (25), which buffer vessel (25) is connected to the purification unit to receive the purified condensate (26) and to the extractor (7) to provide the aqueous extractant (8).

7. The apparatus according to any one of claims 1 to 6, wherein the purification unit comprises a second filter (24) downstream of the bed (23) of cation exchange resin.

8. The apparatus according to any one of claims 1 to 7, comprising a heat exchanger (20), which heat exchanger (20) transfers heat from the aqueous condensate (19) to the dilute aqueous hydrogen peroxide solution (9).

9. A process for the production of hydrogen peroxide by the anthraquinone process comprising the steps of:

a) hydrogenating a working solution comprising alkylanthraquinone and/or alkyltetrahydroanthraquinone and at least one solvent for said alkylanthraquinone and/or alkyltetrahydroanthraquinone with a gas comprising molecular hydrogen in the presence of a hydrogenation catalyst to provide a hydrogenated working solution,

b) oxidizing the hydrogenated working solution of step a) with a gas comprising molecular oxygen to provide an oxidized working solution comprising dissolved hydrogen peroxide,

c) extracting hydrogen peroxide from the oxidised working solution of step b) with an aqueous extractant to provide a dilute aqueous hydrogen peroxide solution containing from 25 to 50 wt% hydrogen peroxide,

d) concentrating the dilute aqueous hydrogen peroxide solution of step c) in a distillation unit comprising a hydrogen peroxide evaporator, a distillation column receiving vapor from the hydrogen peroxide evaporator, and a vapor compressor receiving overhead vapor from the distillation column and delivering compressed vapor as a heating medium to the hydrogen peroxide evaporator, to provide a concentrated aqueous hydrogen peroxide solution containing 45 to 90 weight percent hydrogen peroxide, and an aqueous condensate,

e) purifying the aqueous condensate of step d) in a purification unit by passing it through a bed of cation exchange resin in its protonated form to provide a purified condensate, and

f) reusing the purified condensate of step e) as (i) an aqueous extractant in extraction step c), (ii) a column reflux for concentrating the distillation column in step d), (iii) a diluent in a step of diluting an aqueous hydrogen peroxide solution, or (iv): (i) any combination of (i) to (iii).

10. The method according to claim 9, wherein in step d) a steam driven ejector is used as the vapour compressor.

11. The method according to claim 9 or 10, wherein step e) comprises: filtering the aqueous condensate of step d) before passing it through the bed of cation exchange resin.

12. The process according to any one of claims 9 to 11, wherein part of the purified condensate is sent to the top of the distillation column of step d) to provide column reflux and the remaining of the purified condensate is sent to extraction step c).

13. The process according to any one of claims 9 to 12, wherein in step e) when the concentration of iron, nickel or chromium in the purified condensate increases to a value of more than 0.02mg/l, the bed of cation exchange resin is replaced with fresh resin.

14. The process according to any one of claims 9 to 13, wherein the extracted working solution of step c) is recycled to hydrogenation step a).

15. The process according to claim 14, wherein the extracted working solution of step c) is dried before recycling it to hydrogenation step a).

Technical Field

The present invention relates to an apparatus and a process for producing hydrogen peroxide by the anthraquinone process, which produces an aqueous solution of hydrogen peroxide with low energy consumption, low deionized water consumption and a lower degree of wastewater.

Background

The anthraquinone process, which is the most important process for the production of hydrogen peroxide on an industrial scale, produces hydrogen peroxide by hydrogenating a working solution of alkylanthraquinone or alkyltetrahydroanthraquinone in a water-immiscible solvent and oxidizing the hydrogenated solution with molecular oxygen, usually air. The hydrogen peroxide is then extracted from the working solution with water and the working solution is reused for the generation of hydrogen peroxide. An overview of the anthraquinone process is given in Ullmann's Encyclopedia of Industrial Chemistry, network edition, entry "Hydrogen Peroxide", pages 5-21, DOI 10.1002/14356007.a13_443.pub3, and in particular in FIG. 5 on page 11.

For safety reasons, the extraction of hydrogen peroxide from the working solution is usually carried out to a concentration of up to 40% by weight. The aqueous hydrogen peroxide solution obtained by extraction is then typically concentrated to 45 to 70% by weight by evaporation of the water under reduced pressure to reduce its volume and weight for transportation. The condensate from this evaporation step can be reused for extraction.

EP 419406 a1 and WO 2012/025333 disclose an apparatus and a method for concentrating hydrogen peroxide comprising a vapor compressor and heating the evaporator with the heat of condensation of the compressed vapor to reduce the energy required to concentrate the hydrogen peroxide.

Disclosure of Invention

The inventors of the present invention have now found that recycling the condensate obtained from the step of concentrating hydrogen peroxide with vapour compression to the extraction step of the anthraquinone process, especially when a steam driven ejector is used for vapour compression, may lead to increased decomposition of hydrogen peroxide in the extraction step of the anthraquinone process and to insufficient storage stability of the hydrogen peroxide product. This results in the condensate from the steam compression being discharged to waste water treatment, as the condensate may contain impurities, such as dissolved iron and other metal ions. The inventors of the present invention have further found that such problems of increased decomposition of hydrogen peroxide can be prevented by purifying the condensate with a cation exchange resin in its protonated form. This purified condensate from the steam compression contains a low content of hydrogen peroxide and can be used as feed (inlet) to the extraction step, recycled to the distillation column for concentrating the hydrogen peroxide, or recycled to the step of diluting the aqueous hydrogen peroxide solution. Therefore, wastewater treatment and deionized water consumption can be saved. The purified condensed vapour containing a low content of hydrogen peroxide can be recycled instead of sending the unpurified condensate to waste water treatment. The lower amount of steam condensate sent to the wastewater treatment results in a lower hydrogen peroxide content in the wastewater. This in turn avoids potential inhibition of biological activity by hydrogen peroxide in wastewater treatment.

The subject of the present invention is therefore an apparatus for producing hydrogen peroxide by the anthraquinone process, comprising:

a) a hydrogenator for hydrogenating a working solution comprising alkylanthraquinone and/or alkyltetrahydroanthraquinone and at least one water-immiscible solvent for said alkylanthraquinone and/or alkyltetrahydroanthraquinone with a gas comprising molecular hydrogen in the presence of a hydrogenation catalyst to provide a hydrogenated working solution;

b) an oxidizer for oxidizing the hydrogenated working solution with a gas comprising molecular oxygen to provide an oxidized working solution containing dissolved hydrogen peroxide, the oxidizer connected to the hydrogenator to receive the hydrogenated working solution;

c) an extractor for extracting hydrogen peroxide from an oxidized working solution containing dissolved hydrogen peroxide with an aqueous extractant (aqueous concentrate) to provide a dilute aqueous hydrogen peroxide solution, the extractor being connected to the oxidizer to receive the oxidized working solution containing dissolved hydrogen peroxide;

d) a distillation unit for concentrating an aqueous hydrogen peroxide solution to provide a concentrated aqueous hydrogen peroxide solution and an aqueous condensate, the distillation unit comprising a hydrogen peroxide evaporator, a distillation column receiving vapor from the hydrogen peroxide evaporator, and a vapor compressor receiving overhead vapor from the distillation column and delivering compressed vapor to the hydrogen peroxide evaporator as a heating medium, the distillation unit being connected to the extractor to receive the dilute aqueous hydrogen peroxide solution; and

e) a purification unit comprising a bed of cation exchange resin in its protonated form for purifying the aqueous condensate to provide a purified condensate, the purification unit connected to the distillation unit to receive the aqueous condensate as a feed and (i) connected to the extractor, delivering the purified condensate to the extractor as an aqueous extractant, or (ii) connected to the distillation unit, delivering the purified condensate to the distillation column as a column reflux, or (iii) connected to a hydrogen peroxide dilution device, delivering the purified condensate to the hydrogen peroxide dilution device as a diluent, or (iv) connected to any combination of (i) to (iii).

The subject of the present invention is also a process for the production of hydrogen peroxide by the anthraquinone process, comprising the following steps:

a) hydrogenating a working solution comprising alkylanthraquinone and/or alkyltetrahydroanthraquinone and at least one solvent for said alkylanthraquinone and/or alkyltetrahydroanthraquinone with a gas comprising molecular hydrogen in the presence of a hydrogenation catalyst to provide a hydrogenated working solution,

b) oxidizing the hydrogenated working solution of step a) with a gas comprising molecular oxygen to provide an oxidized working solution comprising dissolved hydrogen peroxide,

c) extracting hydrogen peroxide from the oxidised working solution of step b) with an aqueous extractant to provide a dilute aqueous hydrogen peroxide solution containing from 25 to 50 wt% hydrogen peroxide,

d) concentrating the dilute aqueous hydrogen peroxide solution of step c) in a distillation unit comprising a hydrogen peroxide evaporator, a distillation column receiving vapor from the hydrogen peroxide evaporator, and a vapor compressor receiving overhead vapor from the distillation column and delivering compressed vapor as a heating medium to the hydrogen peroxide evaporator, to provide a concentrated aqueous hydrogen peroxide solution containing 45 to 90 weight percent hydrogen peroxide, and an aqueous condensate,

e) purifying the aqueous condensate of step d) in a purification unit by passing it through a bed of cation exchange resin in its protonated form to provide a purified condensate, and

f) reusing the purified condensate of step e) as (i) an aqueous extractant in extraction step c), (ii) a column reflux for concentrating the distillation column in step d), (iii) a diluent in a step of diluting an aqueous hydrogen peroxide solution, or (iv): (i) any combination of (i) to (iii).

The vapour compressor of the distillation unit is preferably a steam driven ejector.

Drawings

The figure shows a preferred embodiment in which a steam ejector is used as the vapor compressor, a falling film evaporator is used as the hydrogen peroxide evaporator, a counter-current extraction column is used to extract the hydrogen peroxide, and the purified condensate is used as the aqueous extractant in the extraction step.

Detailed Description

In the process of the present invention, hydrogen peroxide is produced by the anthraquinone process.

The anthraquinone process uses a working solution comprising at least one or more of: 2-alkylanthraquinone, 2-alkyltetrahydroanthraquinone, or a mixture of both 2-alkylanthraquinone and 2-alkyltetrahydroanthraquinone (hereinafter referred to as quinone), and at least one solvent for dissolving quinone and hydroquinone. The 2-alkylanthraquinone is preferably 2-Ethylanthraquinone (EAQ), 2-amylanthraquinone (AAQ), or 2- (4-methylpentyl) -anthraquinone IHAQ, more preferably a mixture of EAQ with AAQ and/or IHAQ, wherein the molar fraction of quinone bearing ethyl groups is from 0.05 to 0.95. The working solution preferably contains both 2-alkylanthraquinone and the corresponding 2-alkyltetrahydroanthraquinone, and the ratio of 2-alkyltetrahydroanthraquinone plus 2-alkyltetrahydroanthrahydroquinone to 2-alkylanthraquinone plus 2-alkylanthrahydroquinone is preferably maintained in the range of 1 to 20 by adjusting the conditions of the hydrogenation and regeneration steps used in the anthraquinone process. The working solution preferably comprises a mixture of an alkylbenzene having 9 or 10 carbon atoms as solvent for the anthraquinone and at least one polar solvent selected from the group consisting of Diisobutylcarbinol (DiBC), methylcyclohexyl acetate (MCA), trioctyl phosphate (TOP), Tetrabutylurea (TBU) and N-octylcaprolactam as solvent for the anthrahydroquinone, preferably DiBC, MCA and TOP, and most preferably TOP.

The anthraquinone process is a cyclic process which comprises: step a), hydrogenating the working solution with hydrogen; step b) of oxidizing the hydrogenated working solution of step a) with molecular oxygen; and a step c) of extracting hydrogen peroxide from the oxidized working solution of step b), wherein the extracted working solution of step c) is returned to the hydrogenation step a) to complete the reaction cycle.

In step a), a working solution comprising alkylanthraquinone and/or alkyltetrahydroanthraquinone and at least one solvent for said alkylanthraquinone and/or alkyltetrahydroanthraquinone is hydrogenated with a gas comprising molecular hydrogen in the presence of a hydrogenation catalyst to provide a hydrogenated working solution.

In this hydrogenation step, all or a portion of the quinone is converted to the corresponding hydroquinone. All hydrogenation catalysts known from the prior art for anthraquinone recycling processes can be used as catalysts in the hydrogenation stage. Noble metal catalysts containing palladium as a main component are preferred. The catalyst may be used as a fixed bed catalyst or as a suspended catalyst, and the suspended catalyst may be an unsupported catalyst (such as palladium black) or a supported catalyst, with the suspended supported catalyst being preferred. SiO 2₂、TiO₂、Al₂O₃And mixed oxides thereof, zeolite, BaSO₄Or polysiloxanes can be used as support materials for fixed bed catalysts or supported suspension catalysts, with preference being given to Al₂O₃And sodium aluminum silicate. It is also possible to use catalysts in the form of monoliths or honeycomb moldings, the surface of which is coated with noble metal. The hydrogenation may be carried out in a bubble column reactor, a stirred tank reactor, a tubular reactor, a fixed bed reactor, a loop reactor (loop reactor) or a gas lift reactor, which may be equipped with means for distributing the hydrogen gas in the working solution, such as a static mixer or an injection nozzle. Preferably, a bubble column is used, with recirculation and injection of hydrogen gas at the bottom of the column, as in WO 2010/139728 and Ullmann's encyclopedia of IndThe entry "Hydrogen Peroxide" in the national Chemistry, DOI:10.1002/14356007.a13_443.pub3, pages 13 to 14 and described in FIG. 8. The hydrogenation is preferably carried out at a temperature of from 20 ℃ to 100 ℃, more preferably from 45 ℃ to 75 ℃ and at a pressure of from 0.1MPa to 1MPa, more preferably from 0.2MPa to 0.5 MPa. The hydrogenation is preferably carried out in this way: most of the hydrogen (preferably greater than 90%) introduced into the hydrogenation reactor is consumed in a single pass through the reactor. The ratio between the hydrogen fed to the hydrogenation reactor and the working solution is preferably chosen to convert between 30% and 80% of the quinones to the corresponding hydroquinones. If a mixture of 2-alkylanthraquinones and 2-alkyltetrahydroanthraquinones is used, the ratio between hydrogen and the working solution is preferably chosen such that only the 2-alkyltetrahydroanthraquinones are converted to hydroquinones and the 2-alkylanthraquinones remain in the quinone form.

In step b), the hydrogenated working solution of step a) is oxidized with a gas comprising molecular oxygen to provide an oxidized working solution containing dissolved hydrogen peroxide.

In the oxidation step, the hydrogenated working solution from step a) is reacted with an oxygen-containing gas, preferably with air or oxygen-enriched air. All oxidation reactors known from the prior art for the anthraquinone process can be used for the oxidation, preferably a bubble column operated in countercurrent. The bubble column may be free of internals, but preferably contains distribution means in the form of packing (packings) or sieve trays, most preferably sieve trays in combination with internal coolers. The oxidation is preferably carried out at a temperature of from 30 ℃ to 70 ℃, more preferably from 40 ℃ to 60 ℃. Preferably, the oxidation is carried out with an excess of oxygen to convert more than 90%, preferably more than 95%, of the hydroquinone to the quinone form.

In step c), hydrogen peroxide is extracted from the oxidized working solution of step b) with an aqueous extractant to provide a dilute aqueous hydrogen peroxide solution containing from 25 to 50 wt% hydrogen peroxide, preferably from 25 to 49 wt% hydrogen peroxide.

In this extraction step, the oxidized working solution containing dissolved hydrogen peroxide in step b) is extracted with an aqueous extractant to provide an aqueous hydrogen peroxide solution and an extracted oxidized working solution substantially free of hydrogen peroxide. Deionized water for pH adjustment and/or for preservation, which may optionally contain additives for stabilizing hydrogen peroxide, is preferably used for extracting hydrogen peroxide. Preferably, phosphoric acid is added for pH adjustment and for preservation. The extraction is preferably carried out in a countercurrent continuous extraction column, most preferably a sieve tray column. The aqueous hydrogen peroxide solution obtained by extraction may also be purified to remove the working solution components, preferably by washing with a solvent, which is preferably the solvent contained in the working solution.

Preferably, the extracted working solution of step c) is dried before recycling it to the hydrogenation step a). The extracted working solution is preferably dried by evaporating the water in the working solution at a temperature of 30 ℃ to 110 ℃, preferably 40 ℃ to 75 ℃, and a pressure of 10 mbar to 300 mbar, preferably 20 mbar to 100 mbar. This drying of the extracted working solution is preferably carried out under reduced pressure as described in WO 03/070632, page 8, line 24 to page 8, line 3.

In step d) of the process of the present invention, the dilute aqueous hydrogen peroxide solution obtained in step c is concentrated in a distillation unit to provide a concentrated aqueous hydrogen peroxide solution containing from 45 to 90% by weight of hydrogen peroxide, preferably from 50 to 90% by weight of hydrogen peroxide, and an aqueous condensate. The hydrogen peroxide is concentrated under reduced pressure, preferably at a pressure of 60 mbar to 130 mbar, to prevent explosive hydrogen peroxide vapour from forming in the distillation unit. The distillation unit comprises a hydrogen peroxide vaporizer, a distillation column receiving vapor from the hydrogen peroxide vaporizer, and a vapor compressor receiving all or a portion of the overhead vapor from the distillation column and delivering the compressed vapor to the hydrogen peroxide vaporizer as a heating medium. A thermosiphon vaporizer, which delivers a two-phase mixture of vapor and liquid directly to the distillation column, can be used as the hydrogen peroxide vaporizer. Preferably, a falling-film evaporator is used and the two-phase mixture of vapor and liquid produced in the evaporator is fed to a separation vessel from which the vapor separated is fed to a distillation column. The separation vessel preferably contains a demister horizontally dividing the separation vessel. Then, the two-phase mixture of vapor and liquid generated in the evaporator is introduced below the demister, and an outlet of vapor to be sent to the distillation column is arranged above the demister to remove liquid droplets of vapor separated from the separation vessel. Preferably, the liquid separated in the separation vessel is recycled to the falling-film evaporator. The concentrated aqueous hydrogen peroxide can be withdrawn from the bottom of the distillation column, or preferably from the liquid phase generated in the evaporator. When only a portion of the overhead vapor from the distillation column is compressed, the remaining uncompressed overhead vapor is condensed in a condenser. The aqueous condensate is obtained by condensation of the compressed vapor or by condensation of both the compressed vapor and the uncompressed overhead vapor. In a preferred embodiment, the aqueous condensate is passed through a heat exchanger to transfer heat to a dilute aqueous hydrogen peroxide stream that is passed to a distillation column. Suitable distillation units for concentrating dilute aqueous hydrogen peroxide solutions are known from the prior art. A preferred distillation unit is disclosed in WO 2012/025333, especially in figures 1 and 2 of that document. It is also suitable when the distillation unit of US5,171,407 is equipped with a vapour compressor as shown in figure 4 of that document.

Preferably, a steam-driven ejector is used as the vapour compressor in step d). In this case, the aqueous condensate contains water evaporated from a dilute aqueous hydrogen peroxide solution and condensed motive steam from a steam-driven ejector. The ejector may also be used to reduce the pressure in the distillation column to a desired level.

In step e) of the process of the present invention, the aqueous condensate obtained in step d) is purified in a purification unit by passing all or part of it through a bed of cation exchange resin in its protonated form to provide a purified condensate. Preferably, the aqueous condensate is filtered prior to being passed through the bed of cation exchange resin to prevent particulate impurities (e.g., metal particles) from entering the bed of cation exchange resin. The aqueous condensate is preferably conveyed through the bed of cation exchange resin in an upflow manner, preferably at a temperature of 0 to 90 ℃. The cation exchange resin may be both a gel type resin or a macroporous resin, and is preferably a strongly acidic cation exchange resin containing sulfonic acid groups. Most preferred is a macroporous sulfonated crosslinked polystyrene cation exchange resin. Suitable cation exchange resins shaped into spherical particles are commercially available. In a preferred embodiment, the purified condensate leaving the bed of cation exchange resin is also filtered to prevent accidental carryover of resin particles into the extraction or distillation column.

The bed of cation exchange resin may be regenerated from time to time by passing an aqueous solution of a strong acid through the bed of cation exchange resin to exchange metal ions or ammonium ions for protons. However, in a preferred embodiment, when the concentration of iron, nickel or chromium in the purified condensate increases to a value of more than 0.02mg/l, the bed of cation exchange resin cannot be regenerated, but is replaced with fresh resin. Replacement of the loaded resin rather than regeneration thereof prevents insoluble deposits of iron (III) compounds from accumulating on the resin and also prevents long-term resin degradation due to oxidation of the resin by hydrogen peroxide contained in the aqueous condensate.

In step f) of the process according to the invention, all or part of the purified condensate of step e) is reused. The purified condensate of step e) can be reused as aqueous extractant in the extraction step c). This reduces the amount of deionized water required to extract hydrogen peroxide from the working solution. Alternatively, or in addition, a portion of the purified condensate of step e) may be reused as column reflux for the distillation column in concentration step d). In another alternative, a portion of the purified condensate of step e) is used as diluent in the step of diluting the aqueous hydrogen peroxide solution. All three reuse alternatives may be employed simultaneously or alternately. In a preferred embodiment, part of the purified condensate is sent to the top of the distillation column of step d) to provide column reflux and preferably the remaining purified condensate is sent to extraction step c) to be used as aqueous extractant.

The process of the present invention prevents the introduction of transition metal ions into the hydrogen peroxide product when the condensate from the step of concentrating the hydrogen peroxide is reused in such a way that the condensate is introduced into the hydrogen peroxide product. This allows to save the use of deionized water in the production of hydrogen peroxide and at the same time provide good stability of the hydrogen peroxide product with a small amount of added stabilizer.

The process of the invention is particularly advantageous when a steam driven ejector is used as the vapour compressor in step d), as the steam used to drive the ejector may contain particles of iron salts or rust originating from the steam generator or from the carbon steel steam line, and the step e) of purifying the condensate may prevent carryover of such impurities to process stages where such impurities may increase the iron content in the hydrogen peroxide product.

The process of the present invention preferably comprises at least one additional step of regenerating the working solution, wherein the by-products formed in the process are converted back to quinones. The regeneration is carried out by taking the hydrogenated working solution between steps a) and b) and treating it with alumina and/or sodium hydroxide, preferably using a side stream of a cyclic process in which the regeneration is carried out continuously or periodically. In addition to regenerating the hydrogenated working solution, the extracted oxidized working solution can also be taken off after step c) and regenerated using aluminum oxide, sodium hydroxide or organic amines in a side stream. Suitable methods for regenerating the working solution of the anthraquinone process are known from the prior art.

The process of the invention is preferably carried out in an apparatus of the invention comprising: a hydrogenator for hydrogenating the working solution with a gas containing molecular hydrogen in the presence of a hydrogenation catalyst; an oxidizer for oxidizing the hydrogenated working solution with a gas comprising molecular oxygen, the oxidizer being connected to the hydrogenator to receive the hydrogenated working solution; an extractor for extracting hydrogen peroxide from the oxidized working solution with an aqueous extractant, the extractor being connected to the oxidizer to receive the oxidized working solution; a distillation unit for concentrating an aqueous hydrogen peroxide solution to provide a concentrated aqueous hydrogen peroxide solution and an aqueous condensate, the distillation unit comprising a hydrogen peroxide evaporator, a distillation column receiving vapor from the hydrogen peroxide evaporator, and a vapor compressor receiving overhead vapor from the distillation column and delivering compressed vapor to the hydrogen peroxide evaporator as a heating medium, the distillation unit being connected to an extractor to receive the aqueous hydrogen peroxide solution provided by the extractor; and a purification unit comprising a bed of cation exchange resin in its protonated form for purifying the aqueous condensate to provide a purified condensate, the purification unit being connected to the distillation unit to receive the aqueous condensate as a feed. The purification unit is (i) connected to the extractor to which the purified condensate is delivered as an aqueous extractant, or (ii) connected to the distillation unit to which the purified condensate is delivered as a column reflux, or (iii) connected to the hydrogen peroxide dilution unit to which the purified condensate is delivered as a diluent, or connected to any combination of devices (i) to (iii). The purification unit is preferably connected to both the extractor and the distillation unit to allow a portion of the purified condensate to be sent to the distillation column as column reflux and the remaining purified condensate to be sent to the extractor as aqueous extractant.

The apparatus of the invention preferably comprises a working solution for use in the method of the invention as further described above.

The hydrogenator a) of the apparatus of the present invention can be any type of hydrogenator known in the art for hydrogenating working solutions containing alkylanthraquinones, alkyltetrahydroanthraquinones or both. The hydrogenator may comprise a bubble column reactor, a stirred tank reactor, a tubular reactor, a fixed bed reactor, a loop reactor or a gas lift reactor for carrying out the hydrogenation reaction, depending on whether a suspended hydrogenation catalyst or a fixed bed hydrogenation catalyst should be used. The hydrogenator preferably comprises a bubble column which recirculates and sprays Hydrogen gas at the bottom of the column, used with a suspended catalyst, as is known, for example, in WO 2010/139728 and also Ullmann's Encyclopedia of Industrial Chemistry under the entry "Hydrogen Peroxide", DOI:10.1002/14356007.a 13-443. pub3, pages 13 to 14 and FIG. 8. The hydrogenator preferably comprises a heat exchanger for removing the heat of reaction from the working solution, preferably a heat exchanger arranged within the hydrogenation reactor. When a suspended hydrogenation catalyst should be used, the hydrogenator will typically also comprise a separator, such as a filter, preferably a cross-flow filter, for separating the catalyst from the working solution and returning it to the hydrogenation reactor. The hydrogenator preferably further comprises a hydrogen compressor for carrying out the hydrogenation at a pressure which is higher than the pressure provided by the hydrogen feed source. The hydrogenator may further comprise a separator for separating unreacted hydrogen gas from the hydrogenated working solution and recycling it to the hydrogenation reactor.

The oxidizer b) of the apparatus of the present invention can be any type of oxidizer known in the art for oxidizing a hydrogenated working solution comprising alkyl anthrahydroquinone, alkyl tetrahydroanthrahydroquinone, or both. The oxidizer generally comprises an oxidation reactor and a gas compressor for introducing a compressed gas (e.g., compressed air) comprising molecular oxygen into the oxidation reactor. Preferably, a bubble column, preferably operated in countercurrent, is used as oxidation reactor. The bubble column may be free of internal means, but preferably contains distribution means in the form of packing or sieve trays, most preferably sieve trays in combination with an internal heat exchanger. The oxidizer may further comprise a unit for recovering mechanical energy from the off-gas leaving the oxidation reactor, for example a turboexpander as described in US 4,485,084 or a gas jet pump as described in WO 03/070632.

The extractor c) of the apparatus of the invention may be any type of extractor known in the art for extracting hydrogen peroxide from an oxidized working solution containing dissolved hydrogen peroxide with an aqueous extractant. The extractor preferably comprises an extraction column, more preferably a counter-current continuous extraction column, most preferably a sieve tray column. The extractor may also comprise a coalescer unit for separating dispersed droplets of the working solution from the aqueous hydrogen peroxide solution obtained by extraction, a coalescer unit for separating dispersed water droplets from the extracted working solution, or both types of coalescer units. The extractor may further comprise a unit for purifying the aqueous hydrogen peroxide solution obtained by extraction by removing the working solution components, preferably a unit for washing the aqueous hydrogen peroxide solution with a solvent.

The distillation unit d) of the inventive device comprises a hydrogen peroxide evaporator, a distillation column receiving the vapor from the hydrogen peroxide evaporator, and a vapor compressor receiving the overhead vapor from the distillation column and delivering the compressed vapor to the hydrogen peroxide evaporator as a heating medium. Any type of hydrogen peroxide evaporator and distillation column known in the art for concentrating aqueous hydrogen peroxide solution may be used. The hydrogen peroxide vaporizer may be a distillation column bottom vaporizer (distillation column), which may be arranged separately from the distillation column or may be integrated into the distillation column, for example as disclosed in EP 0419406 a1, fig. 4 or in EP 0835680 a1, fig. 1 and fig. 2. A separate thermosyphon evaporator that delivers a two-phase mixture of vapor and liquid to the distillation column can be used as the distillation column bottom evaporator. Preferably, a separate falling-film evaporator is used as the evaporation bottom evaporator, which separate falling-film evaporator feeds the vapor to the distillation column while the unevaporated liquid is recycled to the falling-film evaporator. More preferably, the distillation unit comprises: a falling film evaporator; a separation vessel horizontally divided by a demister, connected to the falling film evaporator below the demister, to receive the vapor-liquid mixture provided by the evaporator; a conduit connected to the separation vessel above the demister for conveying vapor to the distillation column; and a recycle conduit for recycling liquid from the bottom of the separation vessel to the falling film evaporator. Suitable demisters for removing aqueous droplets from the vapor phase are known in the art, such as fillers, meshes (mesh) or nets (net) made of metal or polymers. The distillation unit may also comprise a hydrogen peroxide feed vaporizer and a distillation bottom vaporizer, wherein the compressed vapor is sent to the hydrogen peroxide feed vaporizer (e.g. as disclosed in WO 2012/025333, fig. 1 and 2), or to the distillation bottom vaporizer, or to both the hydrogen peroxide feed vaporizer and the distillation bottom vaporizer. The distillation column may contain trays or packing or a combination of both, and preferably contains structured packing to minimize pressure drop in the column. The vapor compressor may be a mechanical compressor, preferably a one-stage mechanical compressor, and most preferably a water ring pump. The vapour compressor may alternatively be a gas jet pump and preferably a steam driven ejector. The distillation unit may further comprise a heat exchanger for transferring heat from the aqueous condensate to the dilute aqueous hydrogen peroxide solution, which is fed into the distillation column. Preferably, the inlet of the heat delivery side of the heat exchanger is connected to the outlet for the aqueous condensate on the hydrogen peroxide evaporator, the inlet of the heat uptake side of the heat exchanger is connected to a conduit receiving a dilute aqueous hydrogen peroxide solution from the extraction column, and the outlet of the heat uptake side of the heat exchanger is connected to the feed inlet of the distillation column.

The purification unit e) of the apparatus of the invention comprises a bed of cation exchange resin in its protonated form for purifying the aqueous condensate to provide a purified condensate. The cation exchange resin may be both a gel type resin or a macroporous resin, and is preferably a strongly acidic cation exchange resin containing sulfonic acid groups. Most preferred are crosslinked sulfonated polystyrene cation exchange resins. The bed of cation exchange resin preferably consists of substantially spherical resin particles, preferably 0.1 to 2mm, more preferably 0.5 to 1.0mm in diameter. Suitable cation exchange resins shaped into spherical particles are commercially available. The bed of cation exchange resin is preferably provided as a resin column having a resin bed of length 0.1 to 10 m. The resin column preferably has an inlet for the aqueous condensate to be purified below the resin bed and an outlet for the purified condensate above the resin bed, so as to provide purification by upward flow through the resin bed. The purification unit preferably further comprises a pressure relief valve limiting the pressure in the bed of cation exchange resin. The pressure relief valve is preferably attached to the vessel containing the bed of cation exchange resin at a location above the bed of cation exchange resin. The vessel containing the bed of cation exchange resin may be further connected to a purge vessel located above the vessel containing the bed of cation exchange resin via a flush valve, and a temperature sensor may be placed within the bed of cation exchange resin to open the flush valve when the temperature within the bed of cation exchange resin exceeds a threshold value. This allows the vessel to be flushed with water containing the hydrogen peroxide stabilizer as the temperature on the bed of cation exchange resin rises due to the decomposition of hydrogen peroxide.

The purification unit preferably comprises a first filter upstream of the bed of cation exchange resin. The first filter preferably comprises a filter medium having an average pore size of 0.1 to 50 μm, more preferably 1 to 50 μm. Periodically operated or measured based on pressure differences across the filter, filter backflushing may be used to prevent the filter from becoming clogged with particulates. Any filter media that is sufficiently stable to aqueous hydrogen peroxide and does not promote decomposition of hydrogen peroxide may be used. Preferably, filter media made of aramid polymers, polyolefins, polyamides, fluorinated polymers, sintered metals, or combinations thereof are used. Suitable filter media are commercially available from 3M and Pall. Most preferably, the filter media is made of polypropylene, or is available under the trade nameThe obtained polyamide of 1, 3-diaminobenzene and benzene-1, 3-dicarboxylic acid. The purification unit may additionally comprise a second filter downstream of the bed of cation exchange resin. The same filter media used for the first filter may be used for the second filter.

The apparatus of the present invention preferably comprises an additional buffer vessel connected to the purification unit to receive the purified condensate. The buffer vessel may be connected to the extractor, the purified condensate is delivered to the extractor as an aqueous extractant, or to a distillation unit, the purified condensate is delivered to a distillation column as a column reflux, or to a hydrogen peroxide dilution unit, the purified condensate is delivered to the hydrogen peroxide dilution unit as a diluent, or to any combination of these devices. The buffer vessel is preferably connected to the extraction column to provide the aqueous extractant. The apparatus of the present invention may further comprise: a further buffer vessel for the aqueous condensate between the distillation unit and the purification unit; and a pump for conveying the aqueous condensate from the distillation unit to the purification unit and for conveying the purified condensate from the purification unit to the extractor, the distillation column and/or the hydrogen peroxide dilution device.

The apparatus of the present invention preferably comprises means for pressure relief (such as an opening or a safety valve on the purification unit and any buffer vessel connected thereto) to prevent pressure build-up due to decomposition of the hydrogen peroxide contained in the aqueous condensate. In a preferred embodiment, the purification unit comprises: a temperature sensor in or downstream of the bed of cation exchange resin; a reservoir placed at a position above the resin bed for an aqueous solution containing a hydrogen peroxide stabilizer; a rinse valve for rinsing the resin bed with the stabilizing agent from the reservoir; and a safety circuit that opens the flush valve when the temperature detected by the temperature sensor exceeds a threshold value.

The drawings show preferred embodiments of the apparatus and method of the present invention. The oxidized and extracted working solution (1) comprising alkylanthraquinones and alkyltetrahydroanthraquinones is hydrogenated with hydrogen (3) in a hydrogenator (2) in the presence of a hydrogenation catalyst. The hydrogenated working solution is fed to an oxidizer (4) where it is oxidized with air (5). The off-gas (6) from the oxidizer is further treated for recovery of solvent vapors in a unit not shown in the drawing. The oxidized working solution is transported at a location near the bottom of the extraction column (7) to a counter-current sieve plate extraction column (7) which serves as an extractor for extracting hydrogen peroxide and is extracted with an aqueous extractant (8), the aqueous extractant (8) being introduced at a location near the top of the extraction column (7). The extracted oxidized working solution (1) is obtained at the top of the extraction column (7) and recycled to the hydrogenator (2). A dilute aqueous hydrogen peroxide solution (9) provided by extraction is obtained at the bottom of the extraction column (7) and is fed to an intermediate section of a distillation column (10) of a distillation unit for concentrating the aqueous hydrogen peroxide solution (9). The distillation unit comprises a falling film evaporator (11) as column reboiler as hydrogen peroxide evaporator. The mixture of vapor and liquid generated in the column reboiler is conveyed to a separation vessel (12) equipped with a demister, and the separated vapor (13) is returned to the distillation column (10). The liquid separated in the separation vessel (12) is recycled to the column reboiler and a portion thereof is withdrawn from the recycle as concentrated aqueous hydrogen peroxide product (14). An aqueous stream (15) is introduced near the top of the distillation column (10) as column reflux. The overhead vapor (16) from the distillation column (10) is compressed using a steam-driven ejector (17) acting as a vapor compressor, and the compressed vapor (18) is delivered as a heating medium to the falling-film evaporator (11). The aqueous condensate (19) obtained in the falling-film evaporator (11) by condensing the compressed vapor (18) is passed through a heat exchanger (20) for heating the dilute aqueous hydrogen peroxide solution (9) supplied to the distillation column (10) and further to a first buffer vessel (21) of the purification unit. The aqueous condensate (19) is then passed through a first filter (22), a vessel containing a bed (23) of cation exchange resin in its protonated form, and a second filter (24) to a second buffer vessel (25). The purified condensate (26) collected in the second buffer vessel (25) is conveyed to the extraction column (7) as aqueous extractant (8).

Examples

Example 1

Using the iron test kit MerckArticle number 1.14761 and a 100mm wide cuvette, iron content was determined photometrically at a wavelength of 565nm using a Jenway UV/Vis photometer 6300. The lower detection limit was determined to be 0.02mg/L by calibration measurement.

The condensate from the hydrogen peroxide production facility, which used a steam driven ejector for vapor compression in a distillation unit for concentrating the extracted hydrogen peroxide solution, was analyzed and found to contain 0.09mg/l of dissolved iron. In the extraction step of the anthraquinone process, the condensate with such a high content of dissolved iron is used as an extractant, which will produce aqueous hydrogen peroxide with reduced stability due to decomposition of hydrogen peroxide induced by dissolved iron.

An aqueous solution containing 0.1mg/l of dissolved iron was prepared by adding a standard solution containing 10g/l of iron (III) in 0.5mol/l nitric acid to high purity water. The solution was passed at a flow rate of 2l/h to 7l/h upwards through a glass column containing a macroporous ion exchange resin having a diameter of 28mm and a height of 128mmSP 112H bed. The iron content of the treated water leaving the ion exchange resin bed was below the detection limit, i.e., less than 0.02mg/l, at all flow rates tested.

Example 2

Example 1 was repeated with a solution containing 10mg/l dissolved iron at a flow rate of 3 l/h. The purified solution contained less than 0.02 mg/l. The higher iron content was determined only after more than 200l of the solution was conveyed through the resin bed.

Example 3

The purification units shown in the figures with reference numbers (21) to (25) were installed in a commercial hydrogen peroxide production facility using the anthraquinone process and steam driven ejectors for vapor compression in a distillation unit for concentrating the extracted hydrogen peroxide solution. Passing an aqueous condensate from a hydrogen peroxide evaporator containing 10 to 50mg/l hydrogen peroxide upwardly through a cation exchange resin having a diameter of 145mm and a height of 450 to 600mm at a temperature of 30 to 50 ℃ at a flow rate of 45 to 90l/hSP 112H bed. The purified condensate is fed as an extraction agent to an extractor for extracting hydrogen peroxide from the oxidized working solution. The experiment was performed for 105 days. Throughout this period, the purified condensate contained less than 10 μ g/l iron (analyzed by voltammetry or ICP-MS) and its conductivity was less than 15 μ S/cm. The purified condensate is recycled to the extraction unit for extracting hydrogen peroxide without causing concentrated peroxide produced by the facilityThe decomposition rate of the aqueous hydrogen solution increases and thus the amount of wastewater decreases. Such recycling of the condensed vapor stream and subsequent purification can save up to 3m compared to operating the facility without re-using the aqueous condensate³H deionized water.

List of reference numerals:

1 oxidized and extracted working solution as working solution

2 hydrogenator

3 hydrogen as a gas comprising molecular hydrogen

4 oxidizing device

5 air as molecular oxygen-containing gas

6 waste gas

Sieve plate extraction tower as extractor

8 aqueous extractant

9 dilute aqueous hydrogen peroxide solution

10 distillation column

Falling film evaporator with 11 as hydrogen peroxide evaporator

12 separation container

13 steam flow

14 concentrated aqueous hydrogen peroxide solution

15 water

16 overhead vapor

17 steam-driven ejector as vapor compressor

18 compressed vapor

19 aqueous condensate

20 heat exchanger

21 first buffer container

22 first filter

23 bed of cation exchange resin

24 second filter

25 second buffer container

26 purified condensate