DE4002335A1 - METHOD FOR PRODUCING HYDROGEN PEROXIDE - Google Patents

Abstract

Hydrogen peroxide is prepared by feeding hydrogen or a hydrogen-containing gas and working solution, i.e. an anthraquinone derivative in an organic solvent, into a tubular static mixing zone (9) which is continuous or comprises several parts, in order to hydrogenate the anthraquinone derivative in the presence of a solid catalyst, and by removing hydrogenated working solution (13) and gas (11) from the circulating reaction mixture (8). The reaction mixture (14) is circulated (8) via a catalyst-coated static mixing zone (9), where it is simultaneously both mixed and catalyzed. <IMAGE>

Description

The invention relates to a method for producing Hydrogen peroxide by the anthraquinone method and ins special one of them, namely hydrogenation. The invention particularly relates to a method in which a reaction solution is circulated, in which Reaction solution contain hydrogen or a hydrogen of gas and a working solution, d. H. an anthraquinone deri vat in an organic solvent, through a tube moderate, static mixing zone, which either continuously create or is composed of several parts, is fed to the anthraquinone derivative in the presence to hydrogenate a solid catalyst. Here hy third working solution and gas from the circulated Reaction mixture removed. The invention further relates to a tubular static mixer, the one or has several parts (sub-areas), and the use of the mixer in the aforementioned process.

The production of hydrogen peroxide according to the so-called Anthraquinone method is known. With this procedure becomes an anthraquinone derivative in a solvent that contains one or more components. The on solution made in this way is used as a working solution draws. In the production of hydrogen peroxide  the working solution is first introduced into the hydrogenation stage feeds. During this stage, the anthraquinone deri vate in the presence of a catalyst to the corresponding Anthrahydroquinone derivatives hydrogenated. Then the hydrated working solution fed to an oxidation in which Oxygen or a gas containing oxygen into the ar beit solution is introduced, with water in the solution fabric peroxide is formed. The main reactions of anthraquinone procedures are set out below:

The working solution containing hydrogen peroxide is in the Extraction stage fed in which the hydrogen peroxide is subjected to an extraction treatment to remove it from the Transfer working solution to an aqueous solution. The ex Tracted working solution is removed by removing excess dried water and in the beginning of the Kreislaufver driving, d. H. returned to the hydrogenation stage. The aqueous solution of water obtained by extraction cloth peroxide is cleaned and concentrated.

The hydrogenation described above does one challenging stage in the anthraquinone process. The Hy Dration catalyst must have high activity and high selec have activity. The implementation and selectivity of the Reaction at the hydrogenation stage depend on the partial pressure of hydrogen, temperature, concentrations of  reacting components, the catalyst and the flow conditions in the reactor. Secondary reactions can Amount of anthraquinone derivatives that bil hydrogen peroxide reduce that. So far, both Sus pension reactors and fixed bed reactors used wor the.

Suspended catalysts include, for example as porous catalysts so-called palladium black a carrier (e.g. alumina and activated carbon) palladium and Raney nickel. The porous catalyst becomes suspended, and the hydrogen is in the working solution, e.g. B. in a mixing tank reactor or a tubular Re actuator, dispersed. The is in the tubular reactor Mixing process due to the high linear speed of the ar solution reached. In general, the linear Speeds in excess of 3 m / s and less than 10 m / s an open tube (US-PS 44 28 923). The mixing process was also improved by alternating as a reactor tube used a narrowing and expanding tube (US-PS 34 23 176, Kabisch et al.).

From Finnish patent application 8 64 971 is additional a method of the type mentioned in the preamble known which is a reaction mixture, the hydrogen, the working solution and contains a solid suspended catalyst in one tubular reactor system is recirculated where the reactor system with a static mixer, the con is built up continuously or from several sub-areas exists, is equipped. The one prevailing in the tube system Pressure is below 15 bar and the temperature below 100 ° C. At This process becomes the working solution in the reaction tube system with a flow velocity under 3 m / s in Cycle.

The contact areas and contact times of the catalyst, the Working solution and the hydrogen gas are for the hydrie  reaction is important. When using a stationary, fe Most catalyst in the hydrogenation can be the contact time be shortened in the catalytic reaction, whereby the Share of side reactions is reduced. The lack of one elaborate filtration level represents a considerable after part when using a fixed catalyst bed represent a suspended catalyst. Filtration can also cause technical difficulties because the Kataly sator particles are small.

A suspended catalyst is used in the hydrogenation reaction tion partially not used because it much of the implementation time in a hydrogen-free Part of the process cycle, e.g. B. in the circulation tank det, or because it can remain in the process cycle. A suspended catalyst is also against sintering and mechanical abrasion more sensitive.

Carrier pellets and so-called honeycomb catalysts are used in fixed bed reactors (Berglin et al., US Pat. No. 4,552,748). The carrier used is usually active alumina, but porous supports with a large specific surface area can also be used, e.g. B. SiO ₂ or activated carbon. A noble metal, usually palladium, is absorbed as an active component on the carrier. Only one type of post-filtration is used when using a fixed bed reactor before the oxidation stage in order to separate particles that have come off the bed from the working solution.

In the case of fixed bed reactors, pellets (through knife usually 0.2 to 10 mm) between sieve plates or networks arranged. For pellets of this size it is Transfer of material to and from the deepest pores pores out slowly, which is why the active metal in the inner parts of the pellets unused during the reaction remains. Similarly, there is a high pressure ver  lust and the flow is channeled into the free packed catalyst beds. The reducing gas also leads to withdrawing into its own phase hen, causing the rate of hydrogenation to decrease. It must special care should be taken that no catalyst poison in the working solution or gets into the reducing gas.

The so-called honeycomb catalyst consists of one cellular support structure with parallel channels. The porous Support is fi as a thin layer on the support structure xiert. Furthermore, a noble metal is absorbed on it. A reak gate that works on such a principle has the Disadvantage of a slight mixing of the hydrogen with the Working solution and the possible separation of the gas bubbles un ter formation of its own phase. The heat transfer from the inner areas of the honeycomb remains small, which is why the temperature in it can get too high, a situation which lead to the formation of an increased amount of unwanted side leads products.

A stage that be the hydrogenation in fixed bed reactors limits, is the passage of hydrogen gas from a gas blow into the working solution. The speed of the passage of hydrogen depends on the size of the hydrogen bubbles in the working solution. The smaller the bubbles are, in where the hydrogen is in the solution, the more the total area of the interface between the ar is larger solution and the gas phase. Mixing hydrogen with the working solution was achieved by using static Mixers improved in one place in front of the fixed bed reactor (U.S. Patent 4,428,922). In this way the hydrogen is in of the working solution when entering the reactor in the form of small bubbles before, however, weakens as a result of Channeling in the reactor from the dispersion of the gas.  

A premix reactor in which the working solution is related Hydrogen saturation was also at one point used before the hydrogenation (US-PS 28 37 411).

The object of the invention is to provide a method and a Direction for the production of hydrogen peroxide after the to provide thrachinone method, which has the disadvantages conventional methods and devices are eliminated. The Main features of the invention result from the Claims.

In the process according to the invention, a reaction mixture the hydrogen or a gas containing hydrogen and contains the working solution, in a cycle in a con constant diameter or alternating ver constricting and expanding tubular reactor system ge leads, with the reactor system on horizontally or vertically is arranged and with a static mixer, the continuous is procured or several parts (sub-areas) around summarizes and is coated with a catalytic substance, is equipped. The reaction mixture is in the mixer mixed at the same time and the catalytic treatment subjected. The tubular reactor can be in simpler Be dimensioned so that its length is sufficient for the hydrogen has a sufficient reaction time stands before the end of the tubular reactor enough. Thus, the reducing gas in the reactor does not need Cycle to be led.

The static mixer according to the invention comprises a support structure made of a metallic, ceramic, polymeric or other corresponding material, on the surface of which a porous carrier is fixed. The carrier comprises, for example, aluminum oxide, SiO ₂ , silicates or activated carbon. A metal active in the hydrogenation, e.g. B. palladium, platinum, rhodium, nickel or a mixture of these metals is absorbed on the carrier.

In the reactor according to the invention, a sufficient excess carrying material between the gas and the liquid and sufficient heat transfer from the reactor mixture reached on the pipe wall by static mixers, which at described for example in the following publications are: Chem.-Ing.-Tech., Vol. 52 (1980, No. 4, pages 285-291; Chem. Eng. Prog. Vol. 82 (July 1986), No. 7, pages 42-48 and Vol. 20 (May-June 1986), No. 3, pages 147-154; R.H. Perry and C.H. Chilton, Chemical Engineer's Handbook, 5, New York, McGraw-Hill (1973), section 19, page 22. Likewise axial mixing is minimized and the temperature and concentration profiles in the cross-sectional area of the tube are standardized.

The reaction takes place in a thin catalyst layer from 5 to 300 µm on the surface of the mixer. Because the layer is thin, the proportion of the yield-reducing remains Side reactions small, which is due to the fact that the retention times of the reagents and the reaction pro products in the pores are short. It also becomes catalytic active metal in the thin catalyst layer in effective Way exploited. For this reason, the invention Catalyst layer versus a pellet Fixed bed advantageous.

In contrast to the honeycomb reactor according to US Pat. No. 4,552,748, in which the catalyst pieces are parallel to one another forming channels of equal length without mixing effect the structures in the reactor according to the invention not only as Fixing surfaces for the catalyst but also as Mi shear because the static mixer coated with catalyst Flow baffle plates that each other in differ Chen directions are arranged and the current in effective mer way over the entire cross-sectional area of the reactor to distribute. Such an effect is in the reactor according to US PS 45 52 748, the separate mixer for dispersing and dissolving  hydrogen in the working solution is not required given. According to the invention it is important that the reaction solution is mixed during the catalytic treatment, since it has been found that the hydrogenation reaction is not as effective when the catalytic loading action and mixing in different stages be performed as is the case in US Pat. No. 4,552,748.

Due to the mixing process, heat is transferred and material between the liquid and the catalyst surface faster than that of honeycomb structures straight, parallel channels exist. By means of the cat tors the linear velocities in the reactor can be reduced below 3 m / s because the static mixers Hydrogen even at low linear velocities, e.g. B. in the range of 0.1 to 1.5 m / s in the working solution disperse. At these speeds there is pressure loss and the mechanical abrasion of the catalyst coating low.

The catalyst activities in the static according to the invention Mixers remain almost unaffected even over long periods of time changed. This is partly due to a relatively open flow attribution, with no extensive impurities conditions can adhere to the catalyst surface and the Current keeps the canal walls clean. Furthermore, the na so water-free liquid phase and the oxygen-free gas phase maintaining the activity of the metal.

The length of the reactor depends on the type of mixer used. If the channels of the static mixer are smaller, it gives a larger geometric surface of the mixer where with a larger catalyst layer per unit volume can be bound, but at the same time a larger dy Namely pressure loss in the mixer results. So you can find an optimal size for the mixer channels.  

According to the invention, a high hydrogen peroxide yield calculated in relation to the active metal. This is first of all due to the fact that the entire Catalyst is in the part of the reactor system in where the hydrogenation reaction takes place. Furthermore, the thin catalyst layer is advantageous for the utilization of the active metal.

Another important advantage compared to the next A comparable process consists in the process of mixing of the hydrogen and the working solution related to Transfer of material and heat is beneficial. Consequently uniform conditions arise for selectivity and rate of the hydrogenation reaction advantageous are. By using a thin layer of catalyst the active metal in an effective manner for the hydrogenation be applied. Furthermore, the contact time between the Re agents and the catalyst in short, a factor that leads to ver reducing the amount of by-products.

The hydrogenation process according to the invention can be carried out in large tech African scale are carried out so that the reduction in all of them in an advantageous pressure range to be led. The pressure in the reactor is in the range of 1 to 15 bar, and preferably from 2 to 5 bar. The tem temperature of the working solution is in the advantageous temperature range from 40 to 60 ° C, for example at a Small-scale hydrogenation by attaching a cooling jacket at the reactor.

The invention will now be described with reference to FIG Drawing described in more detail. In the drawing is the hydrogenation process according to the invention schematically Darge poses.

The hydrogenation stage comprises a circulation tank 1 , into which the working solution 14 to be hydrogenated is fed by means of a pump 4 . The working solution is recycled into the circulation tank 1 by means of a pump 3 in the pipe system 8 via a hydrogenation reactor 2 , which is equipped with one or more mixers 9 coated with a catalytic material. The hydrogenation reactor 2 is equipped with a cooling jacket 6 , but it is clear that the cooling can also be achieved in other ways. The working solution 14 to be hydrogenated can also be fed directly into the circulation pipe system 8 . Hydrogen is introduced from a tube 12 into the hydrogenation circulation tube system at a point slightly ahead of the hydrogenation reactor 2 . Exhaust gases are removed through a pipe 11 , which is located in the upper region of the circulation tank 1 . Hydrogenated working solution is removed through a tube 13 , which is connected to the lower portion of the circulation tank 1 , and fed via a pump 5 and an ordered filter 7 to the oxygen treatment. The hydrogenation reaction can be influenced by adjusting the feed rate of hydrogen 12 , the pressure in the reactor and the liquid flow 8 through the reactor.

The invention will be explained in more detail below using an example explained.

example

In an experimental approach on a small scale, an Ar beitsolution used, the 100 g / liter 2-ethylanthraquinone contained. The solvent was a mixture from aromatic hydrocarbons and an organic Phosphorus compound. 10 static mixers with a ca talytical material were coated and a length of 40 mm were in the tubular reactor system, the Length about 400 mm and its diameter was 39 mm, arranged. The reaction mixture became more effective Way across the entire cross-sectional area of the tube distributed and mixed at the same time and a catalytic  subjected to treatment. A layer of approximately 50 µm porous gamma alumina support was on the surface of the metallic static mixer fixed. Was palladium in a total amount of about 0.5% by weight of the Alumina layer absorbed.

The flow rate of the working solution was approximately 2000 liters / h, which is a linear speed of 0.5 m / s corresponded. The temperature was 50 ° C and the pressure at the loading start of the reactor 4.0 bar.

Hydrogen was in the reactor at a rate of 55 liters / h (NTP), of which only a part in the Re actuator was consumed. The hydrogen peroxide formation in Re Actuator averaged 50 kg / (kg palladium) per Hour.

Claims (9)

1. A process for the preparation of hydrogen peroxide by the anthraquinone process by recycling a reaction mixture, in which hydrogen or a hydrogen-containing gas ( 12 ) and a working solution ( 14 ), ie an anthraquinone derivative in an organic solvent, via an elongated static mixing zone ( 2 ), which runs continuously or consists of several parts (partial areas), is fed in to hydrogenate the anthraquinone derivative in the presence of a solid catalyst, and by removing hydrogenated working solution ( 13 ) and gas ( 11 ) from the circulating reaction mixture, characterized in that the reaction mixture ( 8 ) is mixed during the catalytic treatment by being circulated through a static mixing zone ( 2 , 9 ) coated with catalyst. 2. The method according to claim 1, characterized in that the pressure in the mixing zone coated with the catalyst ( 2 , 9 ) is kept in the range from 1 to 15 bar and preferably from 2 to 5 bar and the temperature below 100 ° C and is preferably kept at 40 to 60 ° C. 3. The method according to claim 1 or 2, characterized in that the reaction mixture ( 8 ) through the coated with the cata tor, static mixing zone ( 2 , 9 ) at a speed of 0.1 to 1.5 m / s in a circuit becomes. 4. Tubular, static mixer ( 9 ) which has one or more sections for the catalytic hydrogenation of a reaction mixture which contains hydrogen or a hydrogen-containing gas ( 12 ) and a working solution ( 14 ), ie an anthraquinone derivative in one organic solvent, contains, characterized in that the static mixer ( 9 ) is coated with a solid catalyst. 5. Static mixer according to claim 4, characterized net that it is coated with a porous support which absorbed a material catalyzing a hydrogenation is beer. 6. Static mixer according to claim 5, characterized net that the thickness in the maximum about 300 microns and preferred is at least 5 µm. 7. Static mixer according to claim 5 or 6, characterized ge indicates that the porous support is active Alumina, silica, silicate and / or active coal trades. 8. Static mixer according to one of claims 4 to 7, characterized in that the hydrogenation-catalyzing palladium, platinum, rhodium and / or nickel are absorbed on the mixer ( 9 ). 9. Use of a tubular static mixer ( 9 ), which comprises one or more parts (sections), for the catalytic hydrogenation of an anthraquinone derivative in an organic solvent by hydrogen or a hydrogen-containing gas, the surface of the static mixer with a porous Carrier layer in a maximum thickness of preferably 300 microns be coated, wherein the hydration tion catalyzing metal is absorbed on the carrier layer.