JPH0214333B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing hydrogen peroxide by the well-known anthraquinone method.

US Pat. No. 3,009,782 describes the production of hydrogen peroxide by an anthraquinone working solution process using a fixed bed hydrogenation unit with recirculation cooling of the unit.

U.S. Patent No. 2,966,398 describes the production of hydrogen peroxide using an anthraquinone liquid method, in which the liquid used in the hydroquinone state is sufficiently cooled when it leaves the hydrogenator to form hydroquinone crystals before oxygenation treatment. It is stated that

The present invention involves reducing an alkylated anthraquinone working solution in a hydrogenator using a slurry catalyst to produce a hydroquinone-state working solution, the product being hydrogenated. The present invention relates to a method for recycling a portion of the alkyl anthraquinone working solution to the hydrogenation reactor for improved temperature control. A uniform temperature within the hydrogenator is maintained by a stirrer and/or gas agitation, which also serves to keep the catalyst in suspension. This method eliminates the need to cool the anthraquinone working solution to near the alkyl anthraquinone precipitation temperature as is the case with current methods without recirculation cooling. Another advantage of this process is that high degrees of hydrogenation can be used while maintaining low hydrogenation temperatures.

The drawings are diagrams representing the flow of the method of the present invention.

The alkylanthraquinone working liquid is fed from storage tank 1 through line 2 to pump 3 and then to precooler 4, where it is cooled. The working liquid is supplied from the precooler 4 to a hydrogenator 6 through a line 5. The hydrogenator 6 is equipped with a stirrer 7 and may also be equipped with a cooling jacket 8. Hydrogen is supplied to the hydrogenator via line 9. The hydrogenated working liquid is separated from the catalyst by a strainer 10 immersed in the hydrogenator, and is supplied to a main overfeed tank 12 via a line 11 . The working liquid entering the overfeed tank is essentially free of catalyst. A portion of the effluent from the filter tank 12 is supplied via line 13 to a pump 14 and to the oxidation process via a supplementary cleaning filter (not shown);
The hydrogenated alkyl anthraquinone working solution is oxidized to produce hydrogen peroxide. The remaining working liquid from the filter tank 12 is passed through line 15 to pump 16.
and is further returned to the hydrogenator 6 via a recirculation cooler 17 and a line 18.

The anthraquinone method for producing hydrogen peroxide uses quinones dissolved in a solvent to prepare a working solution. Such solutions exhibit the properties of quinone precipitation or viscosity increase with decreasing temperature. In industrial methods,
It is desirable to use a working solution with a high concentration of quinone. These solutions are characterized by relatively high quinone precipitation temperatures.

Furthermore, in industrial processes it is desirable to operate quinones in solution at high degrees of hydrogenation (high titers). The hydrogenation reaction is exothermic, so as the titer increases, so does the heat generated during the hydrogenation process.

On the other hand, low temperatures are desirable to promote the reaction in the hydrogenation apparatus. This is because by-products are produced at high temperatures.

In conventional hydrogenation apparatuses, the heat from the hydrogenation reaction causes the temperature of the working liquid supplied to the reactor to rise from a pre-cooled state to the hydrogenation temperature in a so-called adiabatic manner. Even with frequent jacket cooling of the hydrogenator, only a small amount of the heat generated could be removed.

Since the lower limit of the cooling temperature of the working liquid supplied to the reactor is restricted by quinone precipitation, a method of cooling adiabatic temperature rise using only the solution supplied to the reactor does not generate a large amount of heat. The use of associated high titers results in high reactor temperatures, and limiting the reactor temperature limits the titer and process capacity to limit heat generation. It turns out.

Hydrogenation equipment is an adiabatic system in which the difference between the temperature of the working liquid, which has been precooled to such an extent that precipitation of quinone does not occur, and the reactor temperature corresponds to the titer required in the equipment. It is desirable to operate under conditions that are smaller than the temperature rise difference.

Various methods have been investigated to introduce supplemental cooling capacity into high capacity (titer) working liquid reactors. Together with a supported catalyst that suspends the working liquid,
Recirculating the condenser back to the reactor has not been adopted into industrial practice due to the tendency of the catalyst to be wasted in the recirculation cooling circuit.

Providing a cooling device inside the hydrogenator or a cooling jacket outside the hydrogenator is
Due to their inherently low cooling efficiency, limited cooling area, complex construction, or a combination of these disadvantages, they do not provide as effective cooling as is necessary.

To introduce supplementary cooling by recirculating a portion of the essentially catalyst-free working liquid through a cooler to the hydrogenator, the total flow rate of the working liquid leaving the hydrogenator must be reduced to oxidation. It needs to be higher (typically about twice) than the flow rate of the working liquid being delivered.

It has generally been thought that it is not possible with conventional equipment for a submerged vessel to withstand flow rates significantly in excess of those delivered to the oxidation stage. In fact, in conventional equipment, sometimes strong pressures are applied to deliver only the flow that is sent to the oxidation stage through the immersed filter.

Now, by adjusting the nature of the catalyst and the hydrogenation conditions, it is possible to achieve a suitable flow capacity through the submerged filter to satisfy both the flow rate delivered to the oxidation stage and the recirculation flow rate. I understand.

One catalyst adjustment that can be made to increase submerged filter flow is to use a catalyst support with a larger particle size than that used in previous devices. Another catalyst adjustment that can be made to increase submerged filter flow is to lower the catalyst concentration in the slurry in the hydrogenator. However, conventional expectations suggest that any of the above catalyst adjustments will work towards reducing the reactivity of the reactor and, in fact, will result in a higher capacity (titer).
In order to achieve the required reaction rate in the device,
It is necessary to support or enhance reactivity.

For these reasons, it would be surprising if sufficient catalytic hydrogenation activity, together with sufficient catalytic overcapacity, could be realized to allow recirculation cooling with catalyst-free working fluids.

The so-called quinone process for producing hydrogen peroxide uses a solution of an alkyl anthraquinone compound which is alternately reduced and oxidized to produce hydrogen peroxide in a suitable solvent. Suitable anthraquinone compounds include 2-ethylanthraquinone, 2-t-butylanthraquinone, 2-sec-amylanthraquinone, 2-isopropylanthraquinone, 2-sec-butylanthraquinone, 2-t-amylanthraquinone,
Included are 1,3-dimethylanthraquinone, mixtures of these quinones and their so-called tetrahydroquinone derivatives. One such compound used is a mixture of 2-tert-butylanthraquinone and sec-amylanthraquinone.

The anthraquinone working solution is prepared by dissolving the working compound in at least one organic solvent. A mixture of two or more organic solvents may be used to increase the solubility of the anthraquinone compound both in its hydrogenated and oxidized state. A number of such solvents and solvent mixtures are known to be useful for dissolving the use compounds during both the hydrogenation and oxidation stages. benzene,
Solvents consisting of mixtures of compounds such as toluene, alkylnaphthalenes, etc. and alcohols have been used for this purpose. Other solvent mixtures useful in this method include alkylbenzenes containing 9 to 11 carbon atoms, trialkyl phosphate esters such as tris(2-ethylhexyl) phosphate, and tetraalkylureas. Another useful solvent system is a mixture of alkylated benzene and diisobutyl carbinol.

Generally, the working solution entering the hydrogenator contains alkylanthraquinone in an oxidized state of 90 to 100%. Generally, the working liquor leaving the hydrogenator contains the alkyl anthraquinone in a 30-70% hydrogenated state, preferably in a 50-60% hydrogenated state.

Generally, the residence time of the working liquid in the hydrogenator is 10
~50 minutes.

Generally, hydrogenators are operated in the range 38° to 60°C, preferably in the range 40° to 45°C.

Generally, the hydrogenator is 69~690kPa (10~100psig)
and is preferably operated in the range of 103 to 344 kpa (15 to 50 psig).

The hydrogenator uses a catalyst slurried in the working liquid. The slurry hydrogenation catalyst of the process of the invention is characterized by a small particle size with a median particle size of 70-200 microns, contains less than 10% of particles less than 50 microns, and has a surface area of 100-350 m ² / g, and remains suspended in the working liquid in the hydrogenator. Suitable hydrogenator catalysts include platinum, palladium, and nickel on supports. The working liquid hydrogen is continuously passed through the hydrogenator. Stirring in the hydrogenator can be done in several ways:
For example, by means of a stirrer or by passing a gas stream through a hydrogenator sufficiently to cause turbulence throughout the working liquid containing the suspended catalyst.

A preferred catalyst is supported palladium.
Suitable support materials include alumina, titania and silica. Generally the catalyst contains palladium in the range 0.1 to 2.0% by weight, preferably 0.5 to 1% by weight. Generally, the working liquor in the hydrogenator contains 2 to 15% by weight of catalyst, preferably in the range of 4 to 8% by weight.

The working liquid in the oxidized state supplied to the reactor is
Preferably at 20-40℃ before being fed to the hydrogenator
Pre-cooled to 32-38°C.

The working liquid leaving the hydrogenator passes through a filter which is immersed within the hydrogenator. A wide variety of strainers can be used, such as cloth strainers and porous metal strainers. The permeating medium is selected to retain essentially all of the catalyst within the hydrogenator.

The hydrogenated working liquid is supplied to the overfeed tank. Upon exiting the superfeed tank, the working liquid is divided into two streams, one stream being sent to an oxidation stage to produce hydrogen peroxide. The other stream is cooled to 20-40°C, preferably 32-38°C, and then recycled to the hydrogenator. Generally 10-90% of the working liquid leaving the overfeed tank, preferably 25-70%
is recycled to the hydrogenator.

Compared to conventional slurry catalytic hydrogenation processes at constant titer or degree of hydrogenation, in the process of the present invention, the temperature of the chilled working liquid in the precooler is lower than that required in the absence of a chilled recirculation stream. It can be several degrees higher than it is. Unlike a normal pre-cooler that cools the liquid used below 30℃, there is no need to cool the liquid used below about 350℃, and the temperature of the hydrogenator is maintained below 45℃. be done. There is also no need to cool the recirculated hydrogenated working liquid below the precipitation temperature of any of its components. Along with these more favorable temperature conditions in the operating system, solutions with higher quinone concentrations can be used than in conventional equipment. This is because the amount of alkylanthraquinone in the working liquid is limited by its solubility at the lowest temperature experienced by the working liquid throughout the circuit. By using a high quinone concentration working solution, it is possible to produce a larger amount of hydrogen peroxide in a unit size unit. Regarding the liquid used, so-called supercooling, at which quinone precipitation does not occur, may occur at a temperature lower than the theoretically determined quinone precipitation temperature. It exists regardless of whether the supercooling temperature corresponds to the temperature or is lower than the precipitation temperature.

While relatively high precooler temperatures can be used, or alternatively, the process of the invention can be operated at lower reactor temperatures than conventional hydrogenators at a given titer. Low reaction temperatures support high productivity while minimizing working liquor by-product formation that occurs as the hydrogenation reaction temperature increases.

Instead of increasing the quinone concentration and hydrogenation degree of the working solution,
Alternatively, it is also possible to use an alkyl anthraquinone, which has lower solubility but is cheaper. That is, ethyl anthraquinone or t-butylanthraquinone can be used in place of an expensive and highly soluble anthraquinone such as 2-sec-amyl anthraquinone.

Additionally, another advantage of using a cooled recirculated stream of working fluid is that it allows the use of inexpensive cooling water, such as from a cooling tower, without the use of costly cryogenic cooling sources. It must be pointed out that although a small amount of heat can be removed by cooling through the reactor jacket, this amount is so small that it can be considered to play only a minor role in the apparatus.

Example 2-t-butylanthraquinone containing its tetrahydro derivative 13wt%, 2-sec-
7wt% amyl anthraquinone including its tetrahydro derivative, mixed alkylbenzene
47wt%, and diisobutyl carbinol 23wt%
The working liquid containing 10% is fed from a storage tank to a precooler, cooled to 35.2°C, and then fed to a 36.4 m ³ (8000 gallon) capacity hydrogenator with cooling jacket maintained at 45°C. . Hydrogenator with hydrogen and nitrogen
Maintain at 138kPa (20psig). In the hydrogenator, a palladium catalyst (0.6% Pd.) supported on alumina is used.
Contains weight%. Alumina has a median particle size of 120 microns and particles with a particle size of less than 50 microns.
Less than 0.2%. The hydrogenator is equipped with four submerged filters, which retain the catalyst within the hydrogenator and through which the hydrogenated working liquor is removed.
Supplied to oversupply tank. At this point, the alkylanthraquinone in the working solution is 50-55% hydrogenated. That is, the degree of hydrogenation is 0.36 Kg mol/m ³
(30bmols/1000ga). On leaving this overfeed tank, 67% of the working liquid is passed through a cleaning filter to the oxidizer, and 33% of the working liquid is recycled to the hydrogenator. This recycle stream is cooled to 35.8°C before being recycled to the hydrogenator.

[Brief explanation of drawings]

The drawings are explanatory diagrams showing the flow of the method of the present invention. 1... Storage tank, 3, 14, 16... Pump, 4
...precooler, 6...hydrogenator, 10...filter, 12
...superfeed tank, 17...recirculation cooler.

Claims (1)

[Scope of Claims] 1. A method for hydrogenating an alkyl anthraquinone working liquid; Supply to the hydrogenator maintained at ~60℃; increase the pressure inside the hydrogenator to 69~690kPa (approximately 10
~100 psig); remove the hydrogenated working solution through an immersed filter that serves to retain essentially all the catalyst within the hydrogenator; 10-90% of the used liquid from the liquid
separating a recycle stream consisting of % and maintaining the stream to be oxidized; cooling the recycle stream to 20-40°C; recycling this cooled stream to the hydrogenator;
A method consisting of things. 2. The method according to claim 1, comprising:
A method in which the catalyst is palladium supported on alumina, silica or titania. 3. The method according to claim 2, comprising:
A method in which the median particle size of the catalyst is between 70 and 200 microns, and less than 10% by weight of particles have a particle size of less than 50 microns. 4. A method according to claim 3, comprising:
30-70% of the alkyl anthraquinone leaving the hydrogenator
A method in which is in a hydrogenated state. 5. The method according to claim 4, comprising:
A method in which 25 to 70% of the used liquid is cooled and recirculated to the hydrogenator. 6. The method according to claim 5, comprising:
How to operate a hydrogenator at 103 to 344 kPa (about 15 to about 50) psig. 7. The method according to claim 6, comprising:
How to maintain a hydrogenator at 40° to 45°C. 8. The method according to claim 7, comprising:
50-60% of the alkyl anthraquinone leaving the hydrogenator
A method in which is in a hydrogenated state.