DE2141234B2 - METHODS FOR THE REGENERATION OF DEGRADED WORKING SOLUTIONS, LIKE THEM IN THE MANUFACTURE OF HYDROGEN PEROXYDE AFTER THE AUTOXYDATION PROCESS USING AN ANTHRAQUINONE - Google Patents

Description

In the production of hydrogen peroxide by the autoxidation process, a working solution is usually used which contains anthraquinone compounds such as nucleus alkylated anthraquinones (t) and nucleus alkylated tetrahydroanthraquinones (■!). These are catalytically hydrogenated to the corresponding anthraquinones (II and III), which in turn are oxidized with a gas containing molecular oxygen. The anthraquinones are regenerated, and the water that is formed! Peroxide is extracted with water and separated from the working solution.

R represents an alkyl group.

Because the hydrogenation reaction and the oxidation reaction of the effective Auihrnchinons repeated over and over again be created by side reactions liner desired substances that are involved in the C'hinon / I lydroquinone conversion do not intervene even if the hydrogenation and the oxidation reaction are below normal Conditions continue to be carried out.

Such undesirable substances include what is referred to as "ineffective anthraquinone" in the following designated oxanthrone (IV), which by oxidizing the working solution with gaseous oxygen at room temperature, Wash the solution, add excess tetrahydroanthraquinone, 10 minutes Introducing gaseous nitrogen, adding a

Amines, / .. B. triethylainin, in an amount of 1% as Catalyst, standing for 30 minutes at room temperature under nitrogen and potentiometric titration of the tetrahydroanthrahydroquinone formed with an oxidizing agent such as lead tetraacetate or Chloranil, determined according to the reaction scheme:

OH

OH

Moles of oxidizing agent used in the titration

= Moles of tetrahydroanthrahydroquinone in the sample
= Moles of inactive anthraquinone in the sample.

The accumulation of these substances in the circulation of the same working solution over a lengthy period Operating period gradually in larger quantities has not only a decrease in the effective anthraquinone concentration result in the working solution, but also causes various types of disturbance.

To regenerate a degraded solution, it has already been recommended to keep the working solution in the presence an ion exchange resin or a base as a catalyst and then with an oxidizing agent treat to speed the response. However, such treatment is as stated a considerable amount of the inactive anthraquinone was converted into degraded substances, which can hardly be regenerated.

According to a method known from German patent specification 12 19 466, degraded working solutions, such as those obtained in the production of hydrogen peroxide by the autoxidation process using an anthraquinone, are obtained by dehydrating the tetrahydroanthraquinone contained in the working solution at 80 to 300 ^° C. using an olefin in the presence a catalyst made from a supported metal of the platinum group.

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

So / .. B. in a solution with a content of 0.1 mol per liter of inactive anthraquinone Rate of dehydration of tetra hydroanthraehinone at 150 to 170 "C to about half that Reduced the speed that can be measured in the absence of the inactive anthraquinone, and the life of the catalyst for dehydrogenation is also shortened, and also arises degraded substances as by-products. And in l'alle

<",

of a solution with a content of 0.05 mol per liter, the dehydration rate decreases at e'.wa 100 "C to almost zero.

The invention aims to regenerate a degraded working solution so that the formation of non-regenerable substances are kept to a minimum.

It has been found that when the working solution is treated at a temperature of 70 to 120 ° C, Ineffective anthraquinone is converted into effective anthraquinone, while tetrahydroanthraquinone is hardly dehydrated and also the formation of the substances that poison the hydrogenation catalyst, takes place only to an extraordinarily small extent.

The inventive method for the regeneration of degraded working solutions, as they arise in the production of hydrogen peroxide by the autoxidation process using an anthraquinone, by dehydrating the tetrahydroanthraquinone contained in the working solution at 80 to 300 ° C, using an olefin in the presence of a catalyst from a A metal of the platinum group applied to a carrier is characterized in that the working solution containing more than 0.02 mol per liter of inactive anthraquinone is brought into contact with the catalyst and the olefin at a temperature of 70 to 120 ° C. and then before the dehydrogenation carries out the dehydrogenation of the tetrahydroanthraquinone in a known manner.

The regenerated working solution can be successfully dehydrated by the method according to the invention of the tetrahydroanthraquinone in the manner described in German Patent 12 19 466 be subjected without a decrease in the rate of dehydration and a loss of high catalyst activity occurs.

In the temperature range from 70 to 120 ° C is the Reaction rate in the regenerating treatment is quite satisfactory, and it becomes preferably one Treated working solution that contains more than 0.02 moles per liter of ineffective anthraquinone.

The catalyst in question for the purposes of the present invention consists of a metal from the group of platinum metals z. B. of platinum, palladium, ruthenium or a mixture thereof, which is applied to a carrier. The catalyst can also be another metal, such as nickel, silver or Copper. The material used as a support for the catalyst advantageously consists of one Alkaline earth oxide, such as calcium oxide, magnesium oxide or aluminum oxide or a compound which largely consists of one of the oxides just mentioned, d. H. from compounds of the formulas

CaO Al ₂ O ₁₁ MgO Al ₂ Oi,
MgO ■ SiO ₂ or the like.

As more useful according to the invention, on one Supported catalyst can, for. B. the systems

Pt-on-AbOt, Pd-on-AI ₂ Oi or
Pd-on-MgO ■ Al.O,
be cited.

The catalyst, e.g. B. the system l'd-on-AhOi, can can be produced in the following way: Am active aluminum oxide, the particle size of which is one mesh unit from 100 to 200 stitches is used in Suspended in water. An aqueous Na ^ PdCLi solution is added to the suspension, and through good By stirring deep palladium salt

that it is almost completely absorbed on the carrier! will. An aqueous formaldehyde solution is then added to the solution, the pH of the solution being adjusted to 9 to Id by adding an aqueous NnOi I solution. The solution is heated without stirring, and the Kalnlysntor system F'd-atif-ALOi results from the reduction of the l'allaclium salt. The palladium-aui-Abu _t thus formed is washed with water and then enlionisiertem at a temperature of 10O ⁰ C unier dried.

In the process according to the invention, the main reaction is the inactive anthraquinone is converted into potent anthraquinone, in a dehydration, and it serves an olefinic one Compound as an acceptor for the hydrogen released from the inactive anthraquinone. The hydrogenation product of the olefin used as the hydrogen acceptor should be at de- reaction temperature be gaseous, so that it is more easily removed from the reaction system and the reaction is easier is to be carried 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 consisting of a higher molecular weight alcohol and an alkylated aromatic hydrocarbon.

After constant, longer. Use of the working solution is found to be a considerable one Contains the amount of inactive anthraquinone caused by the abnormal reduction in the effective Anthraquinone has been formed. The catalyst becomes the working solution, while the ineffective one Containing anthraquinone, added, and the working solution is with the gaseous olefin or an inert Gas containing an olefin at a temperature of 70 to 120 ° Cz. B. brought into contact in a stirred tank, in which the gas is sucked in or bubbles up. Bringing into contact can also take place in a tower, in to which the gas du.ch is introduced through a perforated plate or a distributor nozzle.

Because the rate of oxidation of tetrahydroanthraquinone is far lower than that of anthraquinone is, in the hydrogen peroxide production process, the tetrahydroanthraquinone in the working solution is more effectively dehydrated to anthraquinone.

example 1

A working solution was prepared by dissolving about 1 mol / 1 2-amylanthraquinone in a mixture of trimethylbenzene and diisobutylcarbinol in a volume ratio of 50:50. Using the working solution described above in a cycle process, hydrogen peroxide was continuously produced for a long time, the cycle process comprising the alternating hydrogenation of the anthraquinone and the oxidation of the resulting anthrahydroquinone for the purpose of regenerating the anthraquinone, which is then returned after '' as hydrogen peroxide, the was removed by extraction with water. As can be seen from the following table I /.u, the resulting working solution was found to contain ineffective anthraquinone in a concentration of 0.12 mol per liter. To 1 liter of the working solution, 30 g of the Pd-on-MgO ■ ΛΙ..Ο, catalyst, the content of metallic palladium was 1% and which had been prepared by the method described above, was added, and the Arbcilslösung was 30 minutes without stirring and heated to toilet while introducing a stream of ethylene gas. As a result of this treatment, the ineffective anthraquinone was regenerated to 2-amylanthradiinone. The numerical values in Table I indicate the concentrations of the components contained in the working solution in moles per liter. The dehydration of the tetrahydroanthraquinone during the regeneration treatment is hardly noticeable.

In the table below, for anthraquinone, Tetrahydroanthraquinone, ineffective anthraquinone or the degraded substances the abbreviations AQ, THAQ, NAQ and DS are used.

Table 1

AQ TIlAQ NAQ I) P.

15ci of manufacture
Before regeneration
After regeneration

1.00 0.00
0.65 0.09
0.77 0.09

0.00 0.00
0.12 0.11
0.00 (I, M

Comparative experiments

1) A working solution regenerated in Example 1 was prepared by introducing ethylene at 160 ° C for about 30 minutes with constant stirring in the presence of the same catalyst as was used in Example 1, in a concentration of 100 g of catalyst per liter Brought reaction. The temperature of up to 16O ⁰ C was applied to the dehydrogenation of tetrahydroanthraquinone to anthraquinone.

2) A degraded working solution that was not subjected to the regenerating treatment in Example 1 was used for the purpose of dehydrating the tetrahydroanthraquinone under the same conditions, as described above under 1), brought to implementation.

Table II shows the concentrations of the tetrahydroanthraquinone in the working solution (in moles per liter), following the working instructions given above 1) and 2) have been compiled. The amount of anthraquinone caused by dehydration of the tetrahydroanthraquinone had been regenerated was in the working solution treated in Example 1 Surprisingly three times the size of the one in the working solution that hadn't been treated that way.

Table 11

In front of animal

Dehydration

After dehydration
0.5 to 2 h. 1 h

1) 0.09

2) 0.09

1) 0.31

2) 0.31

0. (Ki 0.055 0.052 0.052

0.08 0.079 0.078 0.078

0.24 0.230 0.223 0.2 K.

0.29 (), 288 0.287 0.2Xd

It was also tetrahydroanthraquinone in ethylene in ethylene in the presence of 100 g / l catalyst

Tor dehydrated according to Example 1 under the specified conditions, the residual concentrations were determined in the specified Zcitinvallen. Neither at 8O ⁰ C still at 120 ⁰ C, a significant dehydration yielded.

Table 111 Table V

Concentration read Tetrahydro ;! nllirnc Ii inoiis, Möl / 1

at 12 (VC at 80 C

0.311 0.309 0.308 0.308 0.307

0.090 0.090 0.090 0.090 0.089

Under the same conditions oxanthrone was charged with 30 g / l of the same catalyst dehydrated, with complete dehydration at 120 ⁰ C and 80 ° C had occurred after about 30 minutes.

Table IV

0 0.311 0.5 0.307 1.0 0.305 1.5 0.304 3.0 0.303 0 0.090 0.5 0.089 1.0 0.089 1.5 0.089 3.0 0.088

Time, b

concentration

of oxantlirone, mol / l

at 120 C

at 80 C

.1S

0.120
0.00

Example 2

0.120 0.020 0.00

A working solution was found by solving. | S 2-Butylanthraquinone in a concentration of about 0.6 mol per liter in a mixture of triamethylbenzene and diisobutylcarbinol in a volume ratio of 50:50. The labor solution was in accordance with Example 1 circulated. v>

A t-liter sample of the degraded working solution was read through propylene containing about 50% by volume of propane in the presence of 30 g of a Pd · Pi on AbOi catalyst for 40 minutes stirred at 90 "C. The catalyst was in the way.« prepared by applying palladium and platinum salts to aluminum oxide by absorption, namely in a concentration corresponding to 0.9 percent by weight metallic palladium and 0.1% metallic platinum, and then the salts with! '' ormaldehyde in alkaline solution reduced.

The concentrations of the components contained in the working solution were determined. The results are compiled in Table V.

(U) AQ TIIAU NAU

During manufacture 0.60 0.00 0.00 0.00

Before regeneration 0.41 0.09 0.10 0.00 After regeneration 0.51 0.09 0.00 0.00

Example 3

A working solution was prepared by dissolving 2-ethylanthraquinone and 2-ethyltetrahydroanlhraquinone in a concentration of 0.3 mol per liter or 0.3 mol per liter in a mixture Tetramethylbenzene and diisobutylcarbinol in a volume ratio of 50:50. The working solution was according to Example 1 circulated.

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-on-CaO Al ₂ O _{r catalyst.} The catalyst was prepared by applying a palladium salt to CaO · AbOj by absorption in such an amount that the content of metallic palladium was 1% by weight, and then reducing the salt with formaldehyde in an alkaline solution. The concentrations of the components in the working solution were determined.

The results are shown in Table VI.

Table Vl

AU THAU NAU US

In the preparation of
Before regeneration
After regeneration

0.30
0.19
0.24

0.30
0.31
0.31

0.00 0.00 0.05 0.05 0.00 0.05

B e i s ρ i c 1 c 4 to 5

It became a working solution by dissolving 2-amylanthraquinone at a concentration of about 1.20 moles per liter in a mixture of trimethylbenzene and diisobutylcarbinol in a 50:50 ratio. The working solution was according to Example 1 circulated.

Two 1-liter samples of the degraded working solution were separated with the introduction of ethylene in the presence of 50 g of catalysts, one of which consisted of Pt-on-MgO. AbO) and the other of Ru-on-MgO. AbO ₁ Stirred at 90 ° C. for one hour. The concentrations of the components in each working solution were determined. The results are shown in Table VII.

AU HIAU NAU DS

In the preparation of 1.20 0.00 0.00 0.00 Before regeneration 0.90 0.07 0.20 0.03 After regeneration Example Ί 1.10 0.07 0.00 0.03 Example 5 1.10 0.07 0.00 0.03

Claims (1)

'right to claim: Process for the regeneration of degraded working solutions, such as those obtained in the production of hydrogen peroxide after the autoxidation process using an anthraquinone, by dehydrating the tetrahydroanthraquinone contained in the working solution at 80 to 300 ° C, using an olefin in the presence of a catalyst from a carrier applied metal of the platinum group, characterized in that before the dehydrogenation, the working solution containing more than 0.02 mol per liter of inactive anthraquinone is brought ^{into contact with the catalyst and the olefin at a temperature of 70 to 120 °} C. and then in a known manner carries out the dehydration of the tetrahydroanthraquinone.