DE2141234C3 - 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 - Google Patents

Description

In the production of hydrogen peroxide by the autoxidation process, a Working solution used the anthraquinone compounds, such as nucleus alkylated anthraquinones (I) and nucleus alkylated Contains tetrahydroanthraquinones (II). These become the corresponding anthraquinones (II and III) catalytically hydrogenated, which in turn is oxidized with a gas containing molecular oxygen will. The anthraquinones are regenerated and the hydrogen peroxide formed is mixed with water extracted and separated from the working solution.

R represents an alkyl group.

Because the hydrogenation reaction and the oxidation reaction of the active anthraquinone repeats continuously undesired substances arise through side reactions, which are converted into the quinone / hydroquinone 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, ζ. B. triethylamine, 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 _; _ _s

= 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 within a longer, ₀ operation period gradually in large quantities has not only a decrease in the effective concentration of the anthraquinone working solution resulted, but also causes various disorders.

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 after the autoxidation process using an anthraquinone, are dehydrated by dehydrating the tetrahydroanthraquinone contained in the working solution at 80 to 300 ^° C. using such an olefin in Regenerated in the presence of a supported platinum group metal catalyst.

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

So z. B. in a solution containing 0.1 mol per liter of inactive anthraquinone, the dehydration rate of tetrahydroanthraquinone at 150 to 170 ^c C is reduced to about half the rate that can be measured in the absence of the inactive anthraquinone, i, s 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 containing 0.05 mol per liter, the rate of dehydration decreases to almost zero at about 100 "C.

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 Arbeitslösüng is ^{treated at a temperature of 70 to 120 0} C, ineffective anthraquinone is converted into effective anthraquinone, while tetrahydroanthraquinone is hardly dehydrated and the formation of the substances that poison the hydrogenation catalyst only in extraordinarily small amount takes place

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 of 70 to 120 ° C, the reaction rate in the regeneration treatment is quite satisfactory, and a working solution is preferably treated which is greater than 0.02 moles per liter Contains ineffective anthraquinone.

The catalyst in question for the purposes of the present invention consists of a metal from the group of platinum metals, e.g. B. of platinum, palladium, ruthenium or a mixture thereof, which is applied to a carrier. The catalyst can also contain another metal such as nickel, silver or copper. The material used as a carrier 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 AI ₂ O ₃ , MgO AI2O3,
MgO · SiO2 or the like.

As the invention well usable, applied to a carrier catalyst can, for. B. the Systems

Pt-on-Al ₂ O ₃ , Pd-on-Al; O ₃ or
Pd-on-MgO · Al ₂ O ₃
be cited.

The catalyst, e.g. B. the system Pd-on-AbO ₃ , can be produced 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 Na2PdCl4 solution is added to the suspension and the palladium salt is stirred well to ensure that

that it is almost completely absorbed on the support. An aqueous formaldehyde solution is then added to the solution, the pH of the solution being adjusted to 9 to 10 by adding an aqueous NaOH solution. The solution is heated with stirring, and the catalyst system Pd-on-AijOj results from the reduction of the palladium salt. The palladium-on-aboi thus formed is washed with deionized water and then dried at a temperature below 100 ^0C.

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 the 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, prolonged use of the working solution, it can be seen that this is 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 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 / l 2-amylanthraquinone in a mixture of trimethylbenzene and diisobutylcarbinol in a volume ratio of 50:50. Using the working solution described above in a circulatory process, hydrogen peroxide was continuously produced for a long time, the circulatory 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 recycled after the hydrogen peroxide that has been formed , removed by extraction with water. As can be seen from Table I below, the resulting working solution was found to contain inactive anthraquinone at a concentration of 0.12 mol per liter. To 1 liter of the working solution, 30 g of the Pd-aui MgO ■ Al ₂ Oj catalyst, the content of metallic palladium was 1% and which had been prepared by the method described above, was added, and the working solution was stirred for 30 minutes and while passing in a stream of ethylene gas heated to 90 ° C / t. As a result of this treatment, the ineffective anthraquinone was regenerated to 2-amylanthraquinone. 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, anthraquinone is ineffective for anthraquinone, tetrahydroanthraquinone or the degraded substances have the abbreviations AQ, THAQ. NAQ or DS used.

Table I.

In the preparation of
Before regeneration
After regeneration

A (J 11 ΙΛΟ ΝΑΟ

1.00
0.65
0.77

0.00 0.09 0.09

0.0 (1 (1.00 0.12 0.14 0.00 0.14

Comparative experiments

1) Einein example 1 regenerated working solution was prepared by about 30 minutes long introducing ethylene at 160 ⁰ C with continuous stirring in the presence of the same catalyst as used in Example 1 and, in a concentration of 100 g of catalyst per liter for Brought reaction. The temperature of up to 160 ° C was used to dehydrate the 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 MoI 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 Il Before the
Dehydration To
0.5 h of dehydration
lh 2 h 3 h 0.09
0.09
0.31
0.31 0.06
0.08
0.24
0.29 0.055 0.052
0.079 0.078
0.230 0.223
0.2XX 0.2X7 0.052
0.078
0.216
(1.2X6 1)
2)
1)

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 being determined in the specified time intervals. Neither at 80 ^° C. nor at 120 ^° C. was there any noticeable dehydration.

Table 111

/ hurry, ii

Concentration of Tclrahydroanllirachinons, mol / l

at 120 C

at 80 C

0.311 0.309 0.308 0.308 0.307

0.090 0.090 0.090 0.090 0.089

Oxanthrone was dehydrogenated under the same conditions with 30 g / l of the same catalyst, whereby Complete dehydration at 120 ° C and 80 ° C had already occurred after about 30 minutes.

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

Table IV concentration
of the oxanlhrone, mol / l at 80 C Time, h at 120 C 0.120
0.020
0.00 0.120
0.00 0
0.5
1.0 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 diisobutylcarbinol by volume 50:50 prepared. The working solution was circulated according to Example 1.

A 1 liter sample of the degraded working solution was passed through with propylene containing about 50% Contained% propane by volume, in the presence of 30 g of a Pd - Pt-on-AhCh catalyst for 40 minutes stirred at 90 ° C. The catalyst was prepared in such a way that palladium and platinum salts were through Absorption on aluminum oxide, namely in a concentration that is 03 percent by weight metallic Palladium and 0.1% 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 V.

Tiihclle V

AQ TlIA (J NAQ I) P.

Hey the creation
Before regeneration
After regeneration

0.60
0.41
0.51

0.0 (1 0.09 0.09

0.00 0.00 0.10 0.00 0.00 0.00

Example 3

A working solution was prepared by dissolving 2-ethylanthraquinone and 2-ethyltetrahydroanthraquinone 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 Oj catalyst.} The catalyst was prepared by applying a palladium _{salt to CaO · Al 2} Oj by absorption in such an amount that the content of metallic palladium was 1 percent 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 compiled in Table VI.

Table Vl

AQ Tl IAQ NAQ I) S

0.00 0.00 0.05 0.05 0.00 0.05

During manufacture 0.30 0.30

Before regeneration 0.19 0.31 After regeneration 0.24 0.31

Examples 4 to 5

A working solution was made by dissolving 2-amy! Anthraquinone at a concentration of about 1.20 moles per liter in a mixture of trimethylbenzene and diisobutylcarbinol in a volume ratio of 50:50. The working solution was according to Example 1 circulated.

Two 1 liter samples of the degraded working solution were separately passed in with ethylene in the presence of 50 g of catalysts, one of which consisted of Pt-on-MgO · Al2O3 and the other of Ru-on-MgO · Al2O3 for one hour 90 ⁰ C stirred. The concentrations of the components in each working solution were determined. The results are shown in Table VII.

Table VII

AQ TIlAQ NAQ 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 4 1.10 0.07 0.00 0.03 Example 5 1.10 0.07 0.00 0.03

Claims (1)

Claim: Process for the regeneration of degraded working solutions, as they occur in the production of hydrogen peroxide after the autoxidation process using an anthraquinone, by dehydrating the tetrahydroanihraquinone 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 dehydration of the tetrahydroanthraquinone.