WO2001034301A1

WO2001034301A1 - Method and device for removal of salts from hydrogen peroxide solutions

Info

Publication number: WO2001034301A1
Application number: PCT/EP2000/011045
Authority: WO
Inventors: Helmut Berrsche; Sabine Gabel; Gabriele Iffland; Jürgen CIPRIAN; Anne Wenzel; Joaquim Henrique Teles; Alwin Rehfinger
Original assignee: Basf Aktiengesellschaft
Priority date: 1999-11-10
Filing date: 2000-11-08
Publication date: 2001-05-17
Also published as: DE19954055A1; AU1520001A

Abstract

A device for removal of at least one salt from a hydrogen peroxide solution, by ion exchange, is characterised in that the device comprises at least one ion exchange bed (I) with a flow area F and height H, whereby the height H of the ion exchange bed is less than or equal to 2, 5.F1/2.

Description

Device and method for removing salts from hydrogen peroxide solutions

The present invention relates to an apparatus and a method for removing at least one salt from a hydrogen peroxide solution by ion exchange.

Methods and devices for removing salts from liquids by ion exchange are known in the prior art, for example from wastewater technology. Here, the wastewater to be treated flows through a container that contains an ion exchange bed made of a solid bed of ion exchange particles.

However, the removal of salt or the setting of a certain salt content often plays a role in the modification or cleaning of chemical reagents.

For example, commercially available hydrogen peroxide solution always contains salts in small amounts, the content of which for certain applications, e.g. B. in the implementation of organic compounds, such as the conversion to propylene oxide starting from propene, is preferably adapted (DE-A 19926725.1), with some salts also being added, as described, for example, in EP-A 0 230 949 or EP A 0 712 852.

Hydrogen peroxide solutions can decay according to the following reaction equation: 2 H ₂ O _{2 (hq)} → 2 H ₂ O _(lιq ) + O ₂ + 46.5 kcal

This decay can release large amounts of gas and energy. An initial concentration of aqueous hydrogen peroxide solution of about 13% by weight is usually sufficient, because of the large amount of energy released, to heat the entire solution to boiling point by decomposition. At even higher initial concentrations, considerable amounts of water vapor can be released in addition to the oxygen formed. For example, the decomposition of a 50% by weight hydrogen peroxide solution can release up to 1000 liters of gas per liter of hydrogen peroxide solution. Additional energy is released by the oxidation of the ion exchanger by, for example, HO ₂ or O. If the hydrogen peroxide solution decomposes rapidly in an ion exchange bed, the pressure can build up due to the filling of the bed, which can cause the apparatus to burst, even if it is provided with a pressure relief device, such as a safety valve or a rupture disc, above or below the bed is. This is exacerbated when ion exchange material in the form of small bulk particles is used.

WO 98/54086 discloses a method for producing high-purity hydrogen peroxide, the hydrogen peroxide solution to be purified being passed through at least two ion exchange beds, it being imperative that at least one cation exchange bed and at least one anion exchange bed be present. This document also discloses that, according to the invention, only those ion exchange devices are used in which the ratio of height to diameter is greater than or equal to 5.

DE-A 42 22 109 describes a process for the production of high-purity hydrogen peroxide for microelectronics, in which hydrogen peroxide is used

Use an ion exchange membrane to clean it It is essential for the process that the hydrogen peroxide solution used is already pre-purified by distillation before it is brought into contact with the ion-exchanging membrane. This pretreatment represents an outlay on equipment that is undesirable in terms of process economy. Furthermore, the production of the ion-exchanging membrane, in which particles of an ion-exchanging resin are embedded in a polymer which does not have any ion-exchanging functional groups, likewise represents an effort which should not be underestimated.

WO 92/06918 discloses a process for purifying hydrogen peroxide, in which an acidic ion-exchanging resin is used. The results according to the invention were achieved here by carrying out a process in which the contact time of the solution to be cleaned with the ion exchange bed is short, i.e. is in the range up to a maximum of 75 seconds.

An object of the present invention was to provide an apparatus and a method for removing salts from hydrogen peroxide solutions by ion exchange, which offer a high degree of safety.

This object was achieved by a device for removing at least one salt from a hydrogen peroxide solution by ion exchange, which is characterized in that the device has at least one non-acidic ion exchange bed (I) with a flow cross-sectional area F and a height H, the height H of the ion exchange bed is less than or equal to 2.5 • F ^1/2 .

By limiting the height of the ion exchange bed, the

Decomposition of hydrogen peroxide solution forming gas can be safely removed. The danger associated with treating hydrogen peroxide solution in usual ion exchange beds can be reduced to a minimum.

The flow cross-sectional area F of an ion exchange bed relates to the empty flow cross-section.

In the context of the present invention, it has proven to be particularly advantageous

1/9 proved to choose the height H of the ion exchange bed less than or equal to 1, 5 • F. Accordingly, the present invention also relates to a device as described above, which is characterized in that the height H of the at least one ion exchange bed (I) is less than or equal to 1.5 * F.

As a rule, the height H of the ion exchange bed corresponds to at least one monolayer of ion exchange particles, that is to say at least the diameter of an ion exchange particle.

In principle, all non-acidic ion exchanger beds with a cation exchanger and / or anion exchanger can be used within the scope of the present invention. Cation and anion exchangers can also be used as so-called mixed beds within an ion exchange bed. In a preferred embodiment of the present invention, only one type of non-acidic ion exchanger is used.

It is further preferred to use a basic ion exchange, particularly preferably that of a basic anion exchanger and further particularly preferably that of a weakly basic anion exchanger.

If different types of ion exchangers are used, sequential treatment with at least one cation exchanger, followed by treatment with at least one anion exchanger, is preferred. As For anion exchangers, a weakly basic anion exchanger is preferred.

In principle, all ion exchangers known to the person skilled in the art can be used in the context of the present invention, for example organic ion exchangers, for example based on polystyrene, or inorganic ion exchangers, for example hydrotalcites, and other phyllosilicates which can contain exchangeable carbonate, hydrogen carbonate or hydroxide groups.

Examples of the particularly preferred in the present invention, weakly basic anion exchangers are polystyrene resins having tertiary amine groups, such as the commercially available anion exchanger Lewatit MP62 and Lewatit ^® MP 63, and Dowex MWA ^® / 1 and Dowex ^® AMW-500. In addition, the use of strongly basic ion exchangers, for example polystyrene resins containing quaternary ammonium groups (with hydroxide counterions), is also conceivable. By way of example here is the commercially available exchanger Lewatit ^® OC-1950 and Dowex ^® 1, Dowex ^® 2, Dowex ^® 11, Dowex ^® 21K and Dowex ^® 550A may be mentioned.

A preferred embodiment of the present invention provides at least two spatially separate ion exchange beds, each ion exchange bed having its own pressure relief device. This embodiment enables the treatment of hydrogen peroxide solutions that require a large volume of ion exchange material. The possibility of dividing the required amount of ion exchange material into two or more ion exchange beds which are spatially separated from one another and provided with their own pressure relief devices further reduces the risk potential when hydrogen peroxide decomposition begins. A large volume of ion exchange material may be required, for example, if the hydrogen peroxide solution to be treated is high Concentration of salts or if high demands are made on the maximum remaining salt amounts in the solution after the treatment.

Accordingly, the present invention also relates to a device as described above, which is characterized in that it comprises at least two spatially separate ion exchange beds (I), each ion exchange bed (I) having at least one pressure relief device (D) of its own.

Pressure relief devices that can be used in the context of the present invention can be selected, for example, from safety valves, rupture disks, pressure relief openings or a combination thereof. The pressure relief openings can be designed such that gases formed are released directly into the atmosphere. It is also possible to interpose a collecting container between the ion exchange bed and the atmosphere.

Accordingly, the present invention also relates to a device as described above, which is characterized in that the at least one pressure relief device (D) is selected from the group consisting of safety valves, rupture disks, pressure relief openings and a combination of two or more thereof.

In the context of the present invention, the ion exchange beds are preferably connected in series or cascade, so that the hydrogen peroxide solution which has been treated in a first ion exchange bed is introduced into a second ion exchange bed for further treatment and after this, if appropriate, into one or more further ion exchange beds , The present invention therefore also relates to a device as described above, which is characterized in that the ion exchange beds (I) are connected in series.

The ion exchange beds preferably have a flow cross-sectional area F in the range from about 0.01 to about 50 m ² , more preferably from about 0.1 to about 10 m ² and particularly preferably from about 0.2 to about 4 m ² .

The device according to the invention preferably has 2 to 200, more preferably 2 to 100, particularly preferably 5 to 50 ion exchange beds connected in series.

Accordingly, the present invention also relates to a device as described above, which is characterized in that it has 5 to 50 ion exchange beds connected in series, each of these ion exchange beds having a flow cross-sectional area in the range from 0.2 to 4 m ² .

The ion exchange beds can be fixed beds or fluidized beds made of ion exchange particles. Fixed bed fillings of ion exchange particles are preferably used. Spheres with a diameter in the range from 0.01 to 5 mm, more preferably from 0.05 to 3 mm and particularly preferably from 0.1 to 1 mm are preferably used as ion exchange particles.

The ion exchange beds are preferably arranged in spatially separate containers. But it is also possible to provide a common shell for all ion exchange beds. Tubular or cylindrical containers are preferred. The ion exchange beds preferably extend over the entire cross-sectional area of the container, so that the flow cross-sectional area F of the ion exchange bed corresponds to the cross-sectional area of the container. The ion exchange beds can be arranged in the containers, for example, as a random bed of ion exchange particles.

The present invention also provides a method for removing salts from a hydrogen peroxide solution by ion exchange. Accordingly, the present invention also relates to a method which is characterized in that the hydrogen peroxide solution is passed continuously through a device as described above.

An embodiment of the method is preferred in which the hydrogen peroxide solution is passed in succession through at least two ion exchange beds, the ion exchange beds being connected in series, spatially separated from one another and each having at least one pressure relief device of its own. By dividing the required amounts of ion exchanger over several ion exchanger beds of limited height, the risk potential with the onset of H ₂ O decomposition is further minimized.

The reaction conditions in which the hydrogen peroxide solution is treated by means of ion exchange are preferably selected so that the hydrogen peroxide solution obtained contains the amount of salt which corresponds to the desired specification.

The setting of the further parameters of the method according to the invention, for example with regard to temperature, pressure or flow rate, is within the range of experience of the person skilled in the art, but is preferably chosen so that the lowest possible decomposition of the hydrogen peroxide solution takes place. The process according to the invention is preferably carried out at normal pressure or at a slight negative pressure or a slight positive pressure, preferably up to 3 bar. The process control at normal pressure is particularly preferred. The temperature of the hydrogen peroxide solution is preferably in the range from 0 to 50 ° C. and particularly preferably from 5 to 20 ° C. The flow rate of the HO ₂ solution is preferably chosen so that the average residence time in each of the ion exchange beds is in the range from 5 minutes to one hour.

Accordingly, the present invention also relates to a process as described above, which is characterized in that the residence time of the hydrogen peroxide solution in each ion exchange bed (I) is in the range from 5 minutes to 1 hour.

A hydrogen peroxide solution which is treated in the process according to the invention and with the device according to the invention can have a hydrogen peroxide concentration in the range from 1 to 75% by weight. Even highly concentrated hydrogen peroxide solutions with a hydrogen peroxide concentration in the range from 40 to 75% by weight can be freed from salts with the present invention with a high degree of safety. These are preferably aqueous hydrogen peroxide solutions.

The hydrogen peroxide solution treated according to the present invention, the salt concentration of which has been reduced by the method according to the invention in the device according to the invention, can advantageously be used for the oxidation of organic compounds, e.g. for the production of alkylene oxides (epoxides) from olefins, in particular for the production of propylene oxide starting from propylene.

The present invention therefore also relates to the use of a hydrogen peroxide solution, the salt concentration of which has been reduced in one of the methods according to the invention described above, for the oxidation of an organic compound. In particular, the present invention relates to a use as described above, which is characterized in that the hydrogen peroxide solution is used to produce an alkylene oxide from an olefin.

It has surprisingly been found that by reducing the amount of dissolved salts in a hydrogen peroxide solution, the reaction of an organic compound, in particular an olefin to an alkylene oxide, with this hydrogen peroxide solution takes place with higher selectivity than it does with hydrogen peroxide solutions of the prior art Technology is the case. This applies in particular when using a catalyst which contains a subgroup metal as active metal. The reaction of the organic compound can be carried out with high selectivity without any pretreatment of the catalyst or addition to the reaction mixture if the amount of dissolved salts in the hydrogen peroxide solution is reduced. In this connection, reference is made to DE-A 199 26 725.1, the content of which in this regard is incorporated fully into the present application by reference.

The hydrogen peroxide solution treated according to the invention, which can be used to convert an organic compound, in particular an olefin to an alkylene oxide, preferably has a concentration of dissolved anions or cations after treatment with the method according to the invention of in each case less than 100 ppm, particularly preferably of a maximum of 60 ppm phosphate, 30 ppm nitrate, 30 ppm sodium ions and 5 ppm potassium ions. An aqueous hydrogen peroxide solution is preferably used for the reaction of the organic compounds.

The hydrogen peroxide concentration of the aqueous hydrogen peroxide solution preferably used is generally in the range from 1 to 70% by weight. %, more preferably in the range from 5 to 60% by weight and particularly preferably in the range from 10 to 50% by weight.

The reactions which can advantageously be carried out using the hydrogen peroxide solution treated according to the invention include the following: the epoxidation of olefins, such as the production of propylene oxide from propene and H ₂ O; Hydroxylations such as the hydroxylation of mono-, bi- or polycyclic aromatics to mono-, di- or higher substituted hydroxyaromatics, for example the conversion of phenol and HO to hydroquinone; oxime formation from ketones in the presence of H ₂ O and ammonia (ammonoximation), for example the preparation of cyclohexanone oxime from cyclohexanone; the Baeyer-Villiger oxidation.

The olefin used can be any organic compound which contains at least one ethylenically unsaturated double bond. It can be aliphatic, aromatic or cycloaliphatic in nature, it can consist of a linear or a branched structure. The olefin preferably contains 2 to 30 carbon atoms. There may be more than one ethylenically unsaturated double bond, for example in dienes or trienes. The olefin can contain additional functional groups such as halogen atoms, carboxyl groups, carboxylic ester functions, hydroxyl groups, ether bridges, sulfide bridges, carbonyl functions, cyano groups or nitro groups.

The following alkenes are mentioned as examples of such organic compounds with at least one C-C double bond:

Ethene, propene, 1-butene, 2-butene, isobutene, butadiene, pentene, piperylene, hexene, hexadiene, heptene, octene, diisobutene, trimethylpentene, nonene, decene, undecene, dodecene, tridecene, tetra- to eicosene, tri- and Tetrapropene, polybutadienes, polyisobutenes, isoprene, terpenes, geraniol, linalool, linalyl acetate, methylene cyclopropane, cyclopentene, cyclohexene, norbornene, cycloheptene, Vinylcyclohexane, vinyloxirane, vinylcyclohexene, styrene, cyclooctene, cyclooctadiene, vinylnorbornene, indene, tetrahydroindene, methylstyrene, dicyclopentadiene, divinylbenzene, cyclododecene, cyclododecatriene, stilbene, diphenylbutadiene, vitamin A, beta-carotene, vinylidene fluoride, allyl halides, crotyl chloride, methallyl chloride, dichlorobutene, allyl alcohol, methallyl alcohol , Butenols, butenediols, cyclopentenediols, pentenols, octadienols, tridecenols, unsaturated steroids, ethoxyethene, isoeugenol, anethole, unsaturated carboxylic acids such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, vinyl acetic acid, unsaturated fatty acids such as oleic acid, linoleic acid, naturally occurring, palatal acid and oils.

Mixtures of the olefins mentioned can also advantageously be epoxidized with the hydrogen peroxide solution treated according to the invention. Alkenes containing 2 to 8 carbon atoms, such as ethene, propene and butene, can be used particularly advantageously. The hydrogen peroxide solution treated according to the invention is particularly suitable for the epoxidation of propene to propylene oxide.

In principle, all heterogeneous catalysts which are suitable for reacting an organic compound with a hydrogen peroxide solution can be used to react the organic compounds with the hydrogen peroxide solution treated according to the invention.

Catalysts are preferably used which comprise a porous oxidic material such as a zeolite. Catalysts are preferably used which comprise a zeolite containing titanium, vanadium, chromium, niobium or zirconium as the porous oxidic material.

Zeolites are known to be crystalline aluminosilicates with ordered channel and cage structures, the pore openings of which are smaller in the area of micropores

0.9 nm. The network of such Zolithe is made up of SiO ₄ ^" and AlO ₄ ^" - Tetrahedra connected by the common oxygen bridges. An overview of the known structures can be found, for example, in MW Meier, DH Olson, Ch. Baerlocher "Atlas of Zeolite Structure Types" 4th edition, Elsevier, London, 1996.

To compensate for the negative electrovalence caused by the incorporation of Al (III) into the Si (IV) silicate lattice, exchangeable cations can be found in zeolites; in particular, depending on the production process, they can be cations of sodium, potassium, lithium or cesium act. If these cations are replaced by protons, for example by ion exchange, then the correspondingly acidic solid with a zeolite structure, the so-called H form, is contained.

Zeolites are now also known which do not contain aluminum and in which titanium (Ti) is partly substituted for Si (IV) in the silicate lattice. These titanium noethes, in particular those with an MFI-type crystal structure, and possibilities for their production are described, for example, in EP-A 0 311 983 or EP-A 405 978. In addition to silicon and titanium, such materials can also be additional

Elements such as As aluminum, zirconium, tin, iron, cobalt, nickel, gallium, boron or a small amount of fluorine. In the zeolite catalysts this can

Titanium of the zeolite can be partially or completely replaced by vanadium, zirconium, chromium or niobium or a mixture of two or more thereof. The molar

The ratio of titanium and / or vanadium, zirconium, chromium or niobium to the sum of silicon and titanium and / or vanadium and / or zirconium, and / or chromium and / or niobium is generally in the range from 0.01: 1 to 0 , 1: 1.

Titanium ohms with an MFI structure are known to be identified by a certain pattern in the determination of their X-ray diffraction images and additionally by a framework vibration band in the infrared region (TR) at about 960 cm ^"1 . Ti, Ge, Te, Ta, V, Cr, Nb, Zr zeolites and in particular Ti zeolites are preferably used.

Here, Ti, Ge, Te, Ta, V, Cr, Nb or Zr zeolites of the structure type MWW, MTN, RTH, FAU, LTA, BEA, MOR, TON, MTW, FER, MFI, MEL, CHA, ERI, RHO, GIS, BOG, NON, EMT, HEU, KFI, TAU, DDR, MTT, RUT, LTL, MAZ, GME, NES, OFF, SGT, EUO, MFS, MCM-22, MTF, MFI / MEL mixed structure and ITQ-4 or a mixture of two or more thereof, with those with MFI structure, BEA structure, MEL structure, ITQ-4 or MFI MEL mixed structure to be regarded as particularly preferred are. Zeolites of this type are described, for example, in the above-mentioned literature by W. M. Meier et al. described.

In particular, the Ti-containing zeolite catalysts, which are generally referred to as "TS-1", "TS-2", "TS-3", "ZSM-48" and "ZSM-12", are particularly preferred catalysts with Ti, TTM-1, Ti-RUT, Ti-MCM-35, titanium-containing zeolites of the type "UTD-1", "CIT-5" and "SSZ-24" as well as Ti zeolites with a zeolite beta-isomorphic To name scaffolding structure.

For example, titanium zothes are used, as are known, for example, from US Pat. No. 3,329,481. In such titanium zeolites, part of the Si (IV) originally present in the silicate lattice is replaced by titanium as Ti (IV). Further titanium zeolites, in particular those with a MFI-type crystal structure, and possibilities for their production are described, inter alia, in US Pat Content is fully included in the context of the present application. Further easily usable titanium-containing zeolites which have a structure different from the MFI structure are described, for example, in EP-A 0 405 978. In addition to silicon and titanium, such Zeolites also contain additional elements such as aluminum (described inter alia in DE-A 31 41 283), gallium (EP-A 0 266 825), boron (US 4,666,692) or small amounts of fluorine (EP-A 0 292 363). With regard to the zeolites described there, the content of the publications described above is also included in full in the context of the present application.

Other zeolite catalysts which can be used to react an organic compound with a hydrogen peroxide solution treated according to the invention include a. in US-A 5,430,000 and WO 94/29408, the relevant content of which is incorporated by reference into the present application.

Other titanium-containing zeolites are those with the structure of ZSM-48, ZSM-12, ferrierite or β-zeolite and mordenite.

The following zeolite catalysts can also be used:

Catalysts with a zeolite structure, as described in DE-A 196 23 611.8, which is hereby fully incorporated by reference into the context of the present application with respect to the catalysts described therein.

These are oxidation catalysts based on titanium or vanadium silicates with a zeolite structure, reference being made to the structures indicated above as preferred with regard to the zeolite structure. These catalysts are characterized in that, as described in detail in the above application, they are shaped by solidifying shaping processes.

Oxidation catalysts based on titanium or vanadium silicates with a zeolite structure with a content of 0.01 to 30 wt or several noble metals from the group of ruthenium, rhodium, palladium, osmium, iridium, platinum, rhenium, gold and silver, which are also characterized in that they have been formed by solidifying shaping processes. Such catalysts are described in DE-A 196 23 609.6, which is hereby fully incorporated by reference into the context of the present application with respect to the catalysts described therein.

With regard to the solidifying shaping processes, the binders and the auxiliaries and the structure of the oxidation catalysts, reference is made to DE-A 196 23 611.8.

The oxidation catalyst described in DE-A 196 23 609.6 has a content of 0.01 to 30% by weight, in particular 0.05 to 15% by weight, especially 0.1 to 8% by weight, in each case based on the amount of titanium or vanadium zeolites, the precious metals mentioned. Palladium is particularly preferred. The noble metals can be applied to the catalyst in the form of suitable base metal components, for example in the form of water-soluble salts, before, during or after the solidifying shaping step.

The following catalysts can also be used:

A molded article containing at least one porous oxidic material, obtainable by a process comprising the following steps: (I) adding a mixture containing at least one alcohol and water to a mixture containing a porous oxidic material or a mixture of two or more thereof , and (II) Kneading, shaping, drying and calcining the mixture added in step (I).

Details regarding this catalyst can be found in DE-A 197 23 751.7, which is hereby fully incorporated by reference into the context of the present application.

Solids containing silicon dioxide can also be produced by a process which comprises the following step (A): (A) contacting at least one precursor of silicon dioxide with at least one structuring agent in a liquid medium, characterized in that the structuring agent is a polyethyleneimine or a Mixture of two or more of them is used.

Details regarding this solid can be found in DE-A 197 32 865.2, the relevant context of which is fully incorporated in the present application by reference.

Other catalysts which can be used are moldings which comprise an inert support and at least one silicate, preferably a crystalline silicate, applied thereon, obtainable by applying a mixture comprising at least one silicate and at least one metal acid ester or a hydrolyzate thereof or a combination of metal acid ester and hydrolyzate of which on the inert carrier as described in DE-A 197 54 924.1, the relevant content of this application also being incorporated into the present application by reference.

Shaped bodies comprising at least one silicate and at least one metal oxide can also be produced by a process which comprises the following step (i): (i) Mixing the at least one silicate with at least one metal oxide sol which has a low content of alkali and alkaline earth metal ions, as described in DE-A 198 15 879.3, can be used.

The relevant content of this application is also incorporated by reference into the context of the present application.

According to the invention, titanium silicalites with a RUT structure can also be produced by a process which comprises steps (a) and (b):

(a) producing a mixture of at least one SiO ₂ source and at least one titanium source;

(b) Crystallization of the mixture from (a) in a pressure vessel with addition of at least one template compound, whereby a suspension is obtained, characterized in that amine or ammonium salts are used as template compound, which are used to stabilize cages of the silicate structure [4 ⁴ 5 ⁴ 6 ² ] and [4 ⁴ 5 ⁶ 6 ⁵ 8 ¹ ] are used.

Details regarding these catalysts can be found in DE-A 198 39 792.5.

In addition, the silicas described in DE-A 198 47 630.2 with mesopores and micropores can be used, which preferably have one or more of the following features (x) to (z):

(x) a sum of the specific surfaces of the meso and micro pores of at least 200 m ² / g;

(y) a sum of the pore volumes of the mesopores and micropores of at least 0.2 ml / g; (z) a maximum of the pore diameter distribution of the mesopores at at least 3 nm.

Further details regarding these catalysts can be found in the above-mentioned application, the relevant context of which is fully incorporated by reference into the present application.

The reaction of the organic compound with the hydrogen peroxide solution treated in accordance with the invention can in principle be carried out using all customary reaction procedures and in all customary reactor types, for example in a suspension procedure or in a fixed bed arrangement. You can work continuously or discontinuously. However, the reaction is preferably carried out in a fixed bed apparatus. A pressure of 1 to 100 bar is preferred. The reaction can be carried out with solvents such as water, alcohols, e.g. Methanol, ethanol, iso-propanol or tert-butanol, or mixtures thereof can be carried out. Mixtures of methanol and water are preferred as solvents, and methanol is particularly preferably used. The reaction can be carried out at temperatures in the range from 0 to 100 ° C., preferably from 20 to 90 ° C. and particularly preferably from 25 to 60 ° C.

A finished, commercially available H ₂ O ₂ solution whose salt content has been reduced in accordance with the present invention can be used for the reaction of an organic compound described above.

There is also the possibility of integrating the process according to the invention into a conventional anthraquinone process for the production of hydrogen peroxide in order to obtain a hydrogen peroxide solution with a reduced salt content. The anthraquinone process, by means of which practically the entire amount of hydrogen peroxide produced worldwide (> 2 million ta) is produced, is based on the catalytic hydrogenation of an anthraquinone compound corresponding anthrahydroquinone compound, subsequent reaction thereof with oxygen to form hydrogen peroxide and subsequent separation of the hydrogen peroxide formed by extraction with water. The anthraquinone compounds used are usually dissolved in a mixture of several organic solvents. The resulting solution is called a working solution. In the anthraquinone process, this working solution is generally passed continuously through the stages of the process described above, and after the hydrogen peroxide has been formed, it is extracted from the working solution with water. The catalytic cycle is closed by renewed hydrogenation of the re-formed anthraquinone compound. The water which receives the hydrogen peroxide in solution after the extraction can then be treated with the method according to the invention or the device according to the invention and thus the salt content can be reduced to a desired level.

The water used for the extraction preferably already has a phosphate, nitrate and sodium ion content before the extraction, which ensures extraction that is harmless from a safety point of view, i.e. usually about 100 ppm to a maximum of about 5000 ppm.

An overview of the anthraquinone process is given by Ullmann's Encyclopedia of Industrial Chemistry, 5th ed., Vol. A13, pp. 447-456.

The present invention has numerous advantages. With the aid of the device according to the invention or the method according to the invention, hydrogen peroxide solutions can be freed of salts almost completely and in a continuous manner by ion exchange. The onset of HO decomposition, which is associated with a strong evolution of gas, does not pose any danger potential even with highly concentrated hydrogen peroxide solutions. Gases formed can quickly leave the ion exchange bed, so that no pressure can build up in the ion exchange bed, which can lead to the device bursting. The present invention offers the possibility of freeing hydrogen peroxide solutions from salts, for example, directly after their manufacture in the manufacturer's plant on an industrial scale. This is possible because the process according to the invention is a continuous process which offers a high degree of security. With the method according to the invention or the device according to the invention, large amounts of hydrogen peroxide solutions can be processed per unit of time.

The present invention will now be explained in more detail with reference to the accompanying drawings, the following description relating thereto, as well as examples and comparative examples.

The drawings show in

Fig. 1 shows a schematic representation of a first preferred

Embodiment of the present invention, in

Fig. 2 in a schematic drawing a second preferred

Embodiment of the present invention, and in

Fig. 3 in a schematic drawing a third preferred

Embodiment of the present invention.

Figure 1 shows a schematic representation of a first preferred embodiment of the present invention. The device according to the invention for removing salts from hydrogen peroxide solutions by ion exchange has a number N of containers B. The containers B are connected in series or cascade. An ion exchange bed I is arranged in each of the containers B. It is a fixed bed from particulate ion exchange material. The containers B have a circular flow cross section. The ion exchange beds I have a flow cross-sectional area F and a height H. The flow cross-sectional area F is based on the empty flow cross-section. The flow cross-sectional area F accordingly corresponds to the cross-sectional area of the container B. The first container in the cascade of containers B is denoted by B _ls, the last container by the reference number B. Each container B has a pressure relief device D, for example in the form of a safety valve, a rupture disk or a simple pressure relief opening.

The hydrogen peroxide solution to be treated is fed along the line 1 from above into the container _\ . The hydrogen peroxide solution treated in the first ion exchange bed Ij leaves the container Bj below the container B-. through line 2. Line 2 connects the lower end of the tank Bj _. with the upper end of the subsequent, second container B. Via this line, the hydrogen peroxide solution treated in the container Bi with the ion exchange bed Ij is fed into the second container B from above. In the drawing, the round bracket with the index N-2 is intended to indicate that further containers with further ion exchange beds can be arranged in this cascade. The solution to be treated is fed into all containers B in the manner described above, namely the supply of the hydrogen peroxide solution to be treated from above into container B and the removal of the treated hydrogen peroxide solution at the lower end of the respective container B or respective ion exchange beds I. Also in the last container B _N , the hydrogen peroxide solution is introduced into the container from above and the finished hydrogen peroxide solution is discharged at the lower end through line N + 1.

The height H of the ion exchange bed is less than or equal to 2.5 • F, where F represents the flow cross-sectional area of the ion exchange bed. At a circular cross section of the ion exchanger bed, the flow cross-sectional area F is calculated according to the following formula:

F = π • r ² = (π / 4) • d ^: 2

where r corresponds to the radius of the ion exchange bed and d to the diameter. The height H of the ion exchange bed is preferably less than or equal to 1.5 - F ^1/2

Figure 2 shows a second preferred embodiment of the present invention. The same reference numerals in FIGS. 2 and 1 designate the same parts. In this respect, reference is made to the comments on FIG. 1. In contrast to FIG. 1, FIG. 2 shows an embodiment in which the containers B are kept open to relieve pressure and the hydrogen peroxide solution is fed into the containers B from below. Through a lateral overflow on each container B, the hydrogen peroxide solution treated in the containers leaves the containers and is fed to the subsequent container at its lower end. The lateral overflow is designed in such a way that the hydrogen peroxide solution is in contact with the entire ion exchange surface of the ion exchange beds. The overflow is accordingly above the upper end of the ion exchange beds. The hydrogen peroxide solution to be freed from salt loads is introduced via line 1 from below into the container Bi, in which the ion exchanger bed I- _. is arranged. The in the ion exchange bed Ij. treated solution leaves the container B _\ via the overflow of the container B _\ and is fed into the subsequent container B from below by means of a line 2. The solution treated in the second container can be further treated in a third, fourth, etc. container. The finished container B leaves the finished H ₂ O ₂ solution via the overflow of the container B _N and is discharged via line N + 1. FIG. 3 shows a third preferred embodiment of the present invention, in which the containers B, as in the embodiment in FIG. 2, are open at the top. The same reference numerals in Figures 3, 2 and 1 denote the same parts; in this respect, reference is made to the explanations relating to FIGS. 1 and 2. In contrast to FIG. 2, in the embodiment according to FIG. 3 the solution to be treated is not supplied to the individual containers B from below but from above. The treated hydrogen peroxide solution again leaves the container B as in Figure 2 via a side overflow. The ion exchange beds I are arranged in the containers B. The containers B also have a siphon on the side and a weir.

The hydrogen peroxide solution to be treated is fed into the container Bj from above and flows through the ion exchanger bed 1 from top to bottom. At the lower end of the tank Bj, the hydrogen peroxide solution changes direction by 180 ° and flows through the side siphon from bottom to top and leaves the tank Bi via the overflow. A line 2 leads the solution treated in the container B _{\ to} the second container B ₂ via the line 2. Again, the hydrogen peroxide solution is added to the ion exchanger bed I ₂ from above, flows through it from top to bottom, and leaves the container B ₂ via the side siphon and the overflow. Further treatment steps can be carried out in a third, fourth, etc. container. The finished hydrogen peroxide solution leaves the last container B _N via line N + 1.

The present invention is not limited to the embodiments described above. Rather, further embodiments of the present invention are conceivable, in particular also embodiments that consist of a combination of the embodiments described above; this applies in particular to the embodiments shown in FIGS. 1 to 3. a combination of the above-described embodiments; this applies in particular to the embodiments shown in FIGS. 1 to 3.

Examples

Comparative examples 1 and 2 illustrate the dangers of handling mixtures of hydrogen peroxide and basic ion exchangers.

Comparative Example 1: decomposition of H ₂ O ₂ in the presence of Lewatit ^® MP62 in a closed autoclave adiabatic

12.3 g (approx. 20 ml) of a freshly regenerated Lewatit ^® MP62 ion exchanger were poured into a thin-walled glass vessel (volume = 105 ml, with magnetic stirrer, internal temperature measurement, inlet valve and rupture disc). The glass vessel was placed in a larger autoclave with automatic pressure and temperature tracking. The mixture was stirred at room temperature until all temperatures were in equilibrium. The pressure tracking prevented the glass vessel from being destroyed. Temperature tracking should minimize heat loss and ensure as adiabatic operation as possible.

After a time t = 25.5 min, 48 g of a commercial 40% hydrogen peroxide solution were then quickly added through the feed valve. The

Results are shown in Figure 4. In FIG. 4, Y) denote the time of addition,

2) the time of the emergency relief,

~ ^ ~ * - ^• the product temperature, the vessel temperature, the pressure, T the temperature in ° C, t the time in min, p the pressure in bar abs ..

CORRECTED SHEET (RULE 91) ISA / EP The temperature and pressure initially rose only slowly. After an induction time of approx. 10 min, however, there was an uncontrollable thermal explosion with a very rapid increase in pressure and temperature, which led to the rupture disc responding.

Comparative Example 2: Decomposition of H ₂ O ₂ in the presence of Lewatit MP62 in a long column (ratio length L to diameter D = 36)

230 ml of the freshly regenerated, weakly basic Lewatit MP62 ion exchanger were filled into a pressure-resistant glass column with a diameter of 24 mm and a length of 870 mm and with a double jacket and an overflow open to the atmosphere, approved for a maximum of 3 bar, and initially with fully desalinated Washed water (approx. 2000 ml, approx. 2 bed volumes / h).

The jacket space was then connected to the cooling circuit of a thermostat and the column thermostated to approx. 10 ° C. 400 g / h of a 40% strength hydrogen peroxide solution were then metered in from below through the column and metering was continued for two days. On average, 97% of the anions present in the hydrogen peroxide solution (mainly phosphate and nitrate) were removed. As expected, the concentration of the cations remained constant. The hydrogen peroxide decomposition remained below the detection limit. The hydrogen peroxide concentration was determined by titration with permanganate solution in the inlet and outlet. In order to check the behavior of the column in the event of a malfunction, the feed and cooling were switched off. After an induction time of approximately 1 hour, an explosive decomposition of the hydrogen peroxide in the lower half of the column caused the column to burst, even though the column was open at the top and the entire cross section was thus available for relief.

Example 1: Decomposition of H ₂ O ₂ in the presence of Lewatit MP62 in a container according to the invention

A cylindrical, upwardly open glass container (height = 15.5 cm, flow cross-sectional area = 62 cm ² ) with a double jacket and bottom drain via a vented siphon with an outlet 120 mm above the bottom of the container was used for the experiment, as shown schematically in FIG. 5 shown. Designate in Figure 5

3) the hydrogen peroxide input,

4) the hydrogen peroxide overflow,

5) the coolant inlet, 6) the coolant outlet,

7) the ion exchange bed,

8) ventilation,

9) the ground network and

10) the coverage network. To hold the ion exchanger bed 7), a fixed and somewhat diagonally mounted metal mesh 9) and a plastic mesh 10) loosely resting on the ion exchanger bed were used on the floor. The container was filled with preconditioned Lewatit ^® MP62 ion exchanger to a height of 10 cm (to precondition the ion exchanger, it was stirred for 24 hours with a 30% hydrogen peroxide solution at room temperature, then regenerated with 5% sodium hydroxide solution and lye-free with deionized water washed) and covered with water. The ratio H: F ^{2 of} the ion exchange bed was approximately 1.13.

The jacket space was connected to the cooling circuit of a thermostat and the container thermostatted to approx. 10 ° C. 400 g / h of a 40% strength hydrogen peroxide solution, which had been precooled to 10 ° C., were then metered in from above through the ion exchange bed, and the metering was continued for four hours. After this time, the water was completely replaced by hydrogen peroxide. In the running hydrogen peroxide solution, 85% of the anions present in the feed (mainly phosphate and nitrate) had been removed. As expected, the concentration of the cations remained constant. The hydrogen peroxide decomposition remained below the detection limit. The hydrogen peroxide concentration was determined by titration with permanganate solution in the inlet and outlet.

In order to check the behavior of the tank in the event of a malfunction, the inlet and cooling were switched off. After an induction time of approx. 90 min, a noticeable decomposition of the hydrogen peroxide started. Although there was a violent evolution of oxygen and water vapor, these could escape unhindered, and there was no explosion or damage to the apparatus. Comparative Example 3: Epoxidation of propene with untreated H ₂ O ₂

Flows of 8.3 g / h of hydrogen peroxide (approx. 40% by weight, untreated) were passed through a tubular reactor with a reaction volume of approx. 50 ml, filled with 20 g of extruded TS-1 catalyst (produced according to WO 97/47386). 49 g / h of methanol and 7.8 g / h of propylene at 40 ° C reaction temperature and 20 bar reaction pressure passed. After leaving the reactor, the reaction mixture was let down in a Sambay evaporator against atmospheric pressure. The separated low boilers were analyzed online in a gas chromatograph. The liquid reaction product was collected, weighed and also analyzed by gas chromatography.

The hydrogen peroxide conversion achieved was 98.4%. The PO selectivity for hydrogen peroxide was 80.3%.

Example 2: Epoxidation of propene with H ₂ O ₂ treated according to the invention

Flows of 8.7 g / h of hydrogen peroxide (approx. 40% by weight), 48, were passed through a tubular reactor with a reaction volume of approx. 50 ml, filled with 16 g of extruded TS-1 catalyst (produced according to WO 97/47386). 8 g / h methanol and 8.3 g / h propylene at 40 ° C reaction temperature and 20 bar reaction pressure, the phosphate and nitrate concentration of H ₂ O by pretreatment with the ion exchanger Lewatit ^® MP62 to about 20% of initial values had been reduced. After leaving the reactor, the reaction mixture was let down in a Sambay evaporator against atmospheric pressure. The separated low boilers were analyzed online in a gas chromatograph. The liquid reaction product was collected, weighed and also analyzed by gas chromatography. The hydrogen peroxide conversion achieved was 98%. The PO selectivity for hydrogen peroxide was 96%. This example shows that by using an H ₂ O ₂ solution with a reduced concentration of dissolved salts, a significantly better propylene oxide selectivity can be achieved.

Claims

Expectations

1. Device for removing at least one salt from a hydrogen peroxide solution by ion exchange, characterized in that the device has at least one non-acidic ion exchange bed (I) with a

Flow cross-sectional area F and a height H, the height

1 py

H of the ion exchange bed is less than or equal to 2.5 • F.

2. Device according to claim 1, characterized in that the height H of the at least one ion exchanger bed (I) is less than or equal to 1.5 • F ^{1 2} .

3. Device according to claim 1 or 2, characterized in that it comprises at least two spatially separate ion exchange beds (I), each ion exchange bed (I) having at least its own pressure relief device (D).

4. The device according to claim 3, characterized in that the at least one pressure relief device (D) is selected from the group consisting of safety valves, rupture disks, pressure relief openings and a combination of two or more thereof.

5. Apparatus according to claim 3 or 4, characterized in that the ion exchange beds (I) are connected in series.

6. Device according to one of claims 1 to 5, characterized in that it has 5 to 50 ion exchange beds connected in series (I), each of these ion exchange beds has a flow cross-sectional area F in the range from 0.2 to 4 m ² .

7. A method for removing salts from a hydrogen peroxide solution by ion exchange, characterized in that the hydrogen peroxide solution is continuously passed through a device according to one of claims 1 to 6.

8. The method according to claim 7, characterized in that the residence time of the hydrogen peroxide solution in each ion exchange bed (I) is in the range of 5 minutes to 1 hour.

9. Use of a hydrogen peroxide solution, the salt concentration of which has been reduced in a process according to claim 7 or 8, for the oxidation of an organic compound.

10. Use according to claim 9, characterized in that the hydrogen peroxide solution is used to produce an alkylene oxide from an olefin.