DE2141234A1 - Process for the regeneration of degraded work solutions, such as those obtained in the production of hydrogen peroxide after the autoxidation process using an anthraquinone - Google Patents

Description

-DR. R. POSCHENRIEDER
DR. E. EG "TTNER
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MITSUBISHI BDOGAWA KAGAKU KABUSHIKI KAISHA, Eo.3-1, 2-chome, Marunouohi, Ghiyoda-ku, a? Okyo (Japan)

Process for the regeneration of degraded working solutions, such as those used in the production of hydrogen peroxide after the auto-oxidation process using an anthraquinone

The present invention relates to a method for regenerating a degraded working solution for re-use in the production of hydrogen peroxide after using anthraquinones Auto-oxidation process.

In the production of hydrogen peroxide after the autoxidation process, a working solution is usually used, the effective anthraquinones, such as ring-alkylated anthraquinones and ring-alkylated tetrahydroanthraquinones (cf. formulas I and V in the formula scheme below).

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For example, as explained in the equation below, effective anthraquinones are added to the corresponding anthrahydroquinones (formulas II and III) catalytically hydrogenated, and the resulting anthrahydroquinones are oxidized with a gas containing molecular oxygen to regenerate the anthraquinones, and the hydrogen peroxide formed is extracted with water to separate it from the working solution.

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2Η123Λ.

R represents an alkyl group

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Since the hydrogenation reaction and the oxidation reaction of the active anthraquinone are constantly repeated, undesired substances arise through side reactions that do not intervene in the quinone / hydroquinone conversion, even if the hydrogenation and the oxidation reaction are carried out under normal conditions will.

The undesirable substances can be divided into

(1) Oxanthrone (Formula IV) and similar substances and in

(2) other degraded substances.

The substance listed under (1) is one of the abnormal reduced substances of anthraquinone, and it is determined in the manner shown below and shall be referred to as "inactive anthraquinone" in the following description of the invention.

Determination of the inactive anthraquinone;

Part of the working solution is treated with gaseous oxygen at room temperature to produce the anthrahydroquinones, which remain in the non-oxidized state to completely oxidize, and the treated solution then becomes washed.

To a weighed sample taken from the solution treated as described above, an amount of tetrahydroanthraquinone is added that is greater than that of the inactive anthraquinone, which is believed to be in the solution,

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and a stream of gaseous nitrogen is then passed through it for 10 minutes. The following operations are performed in a nitrogen atmosphere to prevent any contact with oxygen. An amine, for example triethylamine, is then added to the sample in an amount of 1% as a catalyst, and the whole is left to stand for 50 minutes at room temperature. The reaction can be represented by the following reaction scheme:

The tetrahydroanthrahydroquinone thus formed is then determined by means of potentiometric titration with an oxidizing agent such as lead tetraacetate or ChloraniX.

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Moles of oxidizing agent consumed in the titration = moles of tetrahydroanthrahydroquinone in the sample = Moles of inactive anthraquinone in the sample

Even if the undesirable substances formed in the hydrogen peroxide production process are in their quantity are extraordinarily low per cycle, they do accumulate within a longer period of operation when the same working solution is circulated and after in larger amounts. That not only has a decrease in the effective anthraquinone concentration Result in a working solution, but also causes various types of disturbance in the process.

Some proposals have already been made for a method for regenerating a degraded solution been. So it has been recommended to use the working solution in the presence of an ion exchange resin or a base as a catalyst and then treated with an oxidizing agent to accelerate the reaction. at however, such treatment has been found to remove a substantial amount of the ineffective Anthraquinones converted into degraded substances that can hardly be regenerated.

The present invention aims to provide a much more effective method of regenerating a degraded Develop working solution, with the formation of actually degraded substances at a minimum is held.

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According to the present invention, the working solution used in the production of hydrogen peroxide by an autoxidation process, which contains inactive anthraquinone, is mixed with an olefinic compound at a temperature below 130 ^° C. in the presence of a metal catalyst applied to a carrier, the metal of which is a metal the platinum group is brought into contact so as to regenerate the inactive anthraquinone to effective anthraquinone.

As has already become known from German patent specification 1,219, tetrahydroanthraquinone ^{is dehydrogenated to the corresponding anthraquinone at 80 to 300 °} C. in the presence of an olefinic compound as hydrogen acceptor with a catalyst as used in the present invention.

However, if the working solution to be treated in the above manner contains ineffective anthraquinone, not only is the dehydrogenation of the tetrahydroanthraquinone delayed, but the catalyst becomes poisoned so that it does not hasten the reaction.

For example, in a solution with a content of 0.1 mol per liter of inactive anthraquinone, the rate of dehydration of tetrahydroanthraquinone at 150 to 170 ^o C is reduced to about half the rate that can be measured in the absence of the inactive anthraquinone, and it also shortens the life of the catalyst for dehydrogenation and also produces degraded substances as by-products. And in the case of a solution with a content of

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0.05 mol per liter, the rate of dehydrogenation decreases to almost zero at about 100 ° C.

The inventors of the present method have now found .that if the working solution in a
If the temperature is below 130 C, ineffective anthraquinone is converted into effective anthraquinone
is hardly dehydrated, while tetrahydroanthraquinone
will and also the formation of the substances that are responsible for
a catalyst used in the hydrogenation stage of an anthraquinone process are harmful, occurs only to an extremely small extent.

A temperature of 70 to is particularly advantageous
120 ^° C., because in this range the reaction rate in the regeneration treatment is practically entirely satisfactory, and a working solution is preferably treated which contains more than 0.02 mol per liter of inactive anthraquinone.

The catalyst for the purposes of the present invention in question consists of a metal which is selected from the group of platinum metals, for example from platinum, palladium, ruthenium or a mixture thereof, which is applied to a support, and the catalyst can also be a contain other metals such as nickel, silver or copper. The material used as a support for the catalyst is expediently made of
an alkaline earth oxide such as calcium oxide, magnesium oxide
or aluminum oxide or a compound which consists largely of one of the oxides just mentioned, ie of compounds of the formulas CaO.Al ₂ O ^, MgO.Al ₂ O ,,

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MgO.SiOp or the like. _{The systems Pt-on-Al 2} O-, Pd-on-AlpO-, or Pd-on-MgO.AlpO ^ systems can, for example, be cited as catalysts applied to a support which can be used well in accordance with the invention.

The catalyst, for example the Pd-on-AlgO. System, can be prepared in the following way: An active aluminum oxide, the particle size of which corresponds to a mesh screen fineness of 100 to 200 meshes, is suspended in water. An aqueous NapPdCl ^ solution is added to the suspension and the palladium salt is stirred well to ensure that it is almost completely absorbed onto the support. An aqueous formaldehyde solution is then added to the solution, the ρττ value of the solution being adjusted to 9 to 10 by adding an aqueous NaOH solution. The solution is heated with stirring and the Pd-on-AlpO catalyst system is formed. , by reducing the palladium salt. The palladium-on-AIpO- thus formed is washed with deionized water and then dried at a temperature below 100 ^0C.

In the process of the present invention, the major reaction is in which the inactive anthraquinone is converted into potent anthraquinone, in a dehydration, and it serves an olefinic compound as an acceptor for the hydrogen released from the inactive anthraquinone. What that as As far as olefin used hydrogen acceptor is concerned, it is recommended that its hydrogenation product is gaseous at the reaction temperature because a gaseous product is easily released from the reaction system

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is to be removed so that the implementation is easier to carry out. Preferred hydrogen acceptors are Ethylene, propylene and butylene.

The working solution is prepared by dissolving the alkyl anthraquinone and the alkyl tetrahydroanthraquinone in a solvent mixture that consists of a higher molecular weight alcohol and an alkylated aromatic Hydrocarbon.

After the working solution has been used continuously for quite a long period of time, it will be found that it contains a substantial amount of the ineffective anthraquinone caused by the abnormal reduction of the effective anthraquinone has been formed. The catalyst becomes the working solution, the ineffective one Containing anthraquinone, added, and the working solution is with a gaseous olefin or an inert gas containing an olefin at a temperature brought into contact below 130 ° C. The working solution can be brought into contact with the gas in a stirred tank in which the gas is sucked in or in which it bubbles up, or the contacting can be done in one Tower, in which the gas is introduced through a perforated plate or a distributor nozzle.

Since the rate of oxidation of tetrahydroanthraquinone is far slower than that of anthraquinone, In the hydrogen peroxide production process, efforts have been made by recycling the tetrahydroanthraquinone to dehydrate more effectively to anthraquinone in the working solution. The working solution regenerated according to the teaching of the present invention can successfully undergo dehydration

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of tetrahydroanthraquinone in the German,

Patent 1 219 ^ 66 described manner subjected without a decrease in the rate of dehydrogenation and a loss of high catalyst activity entry.

example 1

A working solution was prepared by dissolving 2-amylanthraquinone in a concentration of about 1 mol per liter in a mixture of trimethylbenzene and diisobutylcarbinol in a volume ratio of 50:50. Using the working solution described above in a circulating process would continuously generate hydrogen peroxide for a long time, the circulatory process comprising the alternating hydrogenation of the anthraquinone and the oxidation of the resulting anthrahydroquinone purpose regeneration of the anthraquinone, which the latter is then recycled after the hydrogen peroxide that had been formed had been removed by extraction with water. As can be seen from Table 1 below, the resulting working solution was found to contain inactive anthraquinone in a concentration of 0.12 mol per liter. To 1 liter of the working solution, 30 g of the Pd-on-MgO.AlgO4 catalyst, the metallic palladium content of which was 1 % and which had been prepared by the method described above, were added, and the working solution was made for 30 minutes heated under stirring and introducing an ethylene gas stream at 90 ⁰ C. As a result of this treatment, the inactive anthraquinone was regenerated to 2-amylanthraquinone. The numerical values in Table 1 give the concentrations of the components contained in the working solution in

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Moles per liter. The dehydration of tetrahydroanthraquinone is hardly noticeable during the regeneration treatment.

The table below is for anthraquinones Tetrahydroanthraquinone, inactive anthraquinone and the degraded substances the abbreviations AQ, THAQ, NAQ and DS are used.

Table 1

Manufacturing 1, AQ THAQ 00 NAQ 00 DS 00 at the regeneration 0, 00 O, 09 0, 12th O, 14th before the regeneration 0, 65 O, 09 O, 00 O, 14th after 77 O, 0, 0,

Comparison attempts

1) Sin · in example 1 regenerated «working solution was by introducing ethylene for about 30 minutes at 160.degree. C. with constant stirring in the presence of the same catalyst as used in Example 1 and a concentration of 100 c of catalyst per liter of reaction brought. The temperature of up to eu 160 ° C. was used for the dehydrogenation of the tetrahydroanthraquinone and anthraquinone.

2) A degraded working solution that was not subjected to the regenerating treatment in Example 1 became

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for the purpose of dehydrating the tetrahydroanthraquinone under the same conditions as above 1) are implemented.

Table 2 shows the concentrations of tetrahydroanthraquinone in the working solution (in moles per liter), according to the work instructions given above 1) and 2) have been compiled. The amount of anthraquinone produced by the dehydration of the tetrahydroanthraquinone was regenerated was three times as much in the working solution treated in Example 1 great as the one in the working solution that hadn't been treated like that.

Table 2

in front of the De
hydrogenation after the De
hydrogenation Difference in
of concentration D.
2) 0.09
0.09 0.06
0.08 0.02
0.01

Example 2

It became a working solution by dissolving 2-butylanthraquinone at a concentration of about 0.6 mol per liter in a mixture of tetramethylbenzene and Diisobutylcarbinoi produced in a volume ratio of 50:50. The working solution was, as described in Example 1, circulated and thus degraded Received working solution containing inactive anthraquinone and degraded substances.

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A 1-liter sample of the degraded working solution was stirred by passing propylene, containing about 50 volume ^ propane, in the presence of 30 of a Pd.Pt-on-Al ₂ 0, catalyst g for 40 minutes at 90 ⁰ C. . The catalyst was prepared in such a way that one applied palladium and platinum salts by absorption on aluminum oxide in a concentration corresponding to 0.9% by weight of metallic palladium and 0.1% of metallic platinum, and then the salts with formaldehyde in alkaline Solution reduced.

The concentrations of the components contained in the working solution were determined. The results are compiled in table 3.

Table 3

the Manufacturing AQ THAQ 00 NAQ 00 DS 00 at the regeneration 0.60 O, 09 O, 10 O, 00 before of regeneration 0.41 0, 09 0, 00 0, 00 after 0.51 0, 0, O,

Example 3

A working solution was prepared by solving 2-ethylanthraquinone and 2-ethyltetrahydroanthraquinone at a concentration of 0.3 mol per liter and 0.3 mol, respectively per liter in a mixture of tetramethylbenzene and diisobutylcarbinol in a volume ratio of 50:50. The Working solution was circulated as described in Example 1, and a degraded working solution was obtained.

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A 1 liter sample of the degraded working solution was stirred for 45 minutes at 100 ° C. _{while passing in butylene in the presence of a Pd-auf-CaO.Al 2 O, catalyst.} The catalyst was prepared in such a way that a palladium salt on CaO. AlpO ^ _{5 applied} by absorption in such an amount that the content of metallic palladium was 1 percent by weight, and then the salt was reduced with formaldehyde in an alkaline solution. The concentrations of the components in the working solution were determined.

The results are shown in Table 4.

Table 4

AQ THAQ NAQ DS in the preparation of
before regeneration
after regeneration 0.30
0.19
0.24 0.30
0.31
0.31 0.00
0.05
O ₄ OO 0.00
0.05
0.05

Examples 4 to 5

Bb a working solution was prepared by dissolving 2-aejrlaathraquinone in a concentration of about 1.20 hol per liter in a mixture of trimethylbenzene and di-isobutylcarbinol in a volume ratio never 50 to 50. The working solution was circulated as described in Example 1 , and a degraded working solution was obtained.

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Two 1 liter samples of the degraded working solution were dissolved separately. Introducing ethylene into G-cgi-n ^ r'-: from 50 g each of catalyst ^; 3n _? one of which is from P'c-on = "KgO.AIpO, and the other from Ru aUi.-i% O" riipC, was stirred for one hour at 90 ⁰ C. The consensus "" rions of the components in .lader work performance were determined * The results are is .. ^:: ', £ · .. ■ Λ le 5

1 ps -.

1.20 THAQ MQ DS in the preparation of 0.90 0.00 ' 0.00 0.00 before regeneration 0.07 0.20 0.03 after regeneration 1.10 Example 4 1.10 0.07 0.00 0.03 Example 5 0.07 0.00 0.03

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Claims (5)

JL ( ■ => Claims 1 "Process for the regeneration of degraded working solutions, such as those obtained in the production of hydrogen peroxide by the autoxidation process using an anthraquinone, characterized in that the inactive anthraquinone is brought into contact with the non-effective anthraquinone Anthraquinone-containing working solution with an olefinic compound regenerated in the presence of a catalyst at a temperature of below 150 ^° C., said catalyst consisting of a metal of the platinum group applied to a support. 2. The method of claim 1, characterized in that the regeneration is carried out at a temperature between 70 ^Q C and 120 ° C according to. 3. The method according to claim 1, characterized in, that a working solution is treated * which contains more than 0.02 mol of inactive anthraquinone per liter of solution contains. 4. The method according to claim 1, characterized in that said platinum group metal is either from platinum itself or from palladium or ruthenium or a mixture of the same. 5. The method according to claim 4, characterized in that said olefinic compound is selected from ethylene, Consists of propylene or butylene 209809 / U3S