JPH0466560A - Method for activating catalyst - Google Patents

Abstract

PURPOSE:To obtain acrylamide useful as a monomer for various applications in improved selectivity by treating a practical Raney copper catalyst with a specific aqueous solution when acrylonitrile is reacted with water in the presence of the catalyst in a liquid phase. CONSTITUTION:When acrylonitrile is reacted with water in the presence of a practical Raney copper catalyst in a liquid phase to obtain the objective compound, the catalyst is preliminarily treated with the aqueous solution of one or more compounds selected from ammonium chloride, ammonium sulfate, sodium chloride and sodium carbonate for the activation thereof. The treatment is performed usually at 1-150 deg.C, preferably 50-120 deg.C. The concentration of the treating agent is preferably 1-40wt.%. The treatment is carried out for 0.5-5hr. The wt. ratio of the acrylonitrile and water is preferably 50/50 to 10/90.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for activating a practical Raney copper catalyst, and in particular, when catalytically synthesizing acrylamide from acrylonitrile and water in a liquid phase, the practical Raney copper catalyst to be used is activated in advance. This relates to a method of activating and activating by pretreatment.

Acrylamide is an industrially useful monomer that is used in the production of acrylamide-based polymers used as paper strength agents, flocculants, etc., and has many other uses.

[Prior Art] A method for producing acrylamide by catalytically hydrating acrylonitrile in the presence of a metallic copper-based catalyst including a Furany copper catalyst is already well known.

For example, Special Publication No. 49-30810, Special Publication No. 50-12
409, Special Publication No. 50-22019, Special Publication No. 54-77
54, Special Publication No. 5526910, Special Publication No. 55-1165
7, etc.

Various methods have also been proposed for improving the catalytic hydration reaction system. For example, in Tokuko Sho 50-'12409,
The activity is improved by adding copper salts such as copper nitrate and copper acetate to the reaction system, and in Japanese Patent Publication No. 57-20294, adding nitric acid or nitrates such as aluminum nitrate to the reaction system improves the activity and is maintained for a long time. Japanese Patent Application Publication No. 5
In No. 8-88344, the Raney copper catalyst is partially oxidized with nitrate or the like in advance to increase its activity.

In order to synthesize acrylamide by catalytic hydration of acrylonitrile in this way, nitrate is added to the reaction system of a metallic copper catalyst containing Raney copper, and an inorganic or organic acid is used as a dissolving agent for the oxidized portion of the catalyst. It is known that the addition of these compounds is advantageous for stably continuing the synthesis reaction over a long period of time.

Also known is a method for regenerating a Raney copper catalyst that has been deactivated over a long period of time in an acrylamide synthesis reaction. For example, Japanese Patent Publication No. 54-7754 and U.S. Pat. has been done.

[Problem to be Solved by the Invention 1] It is practical to use a Raney copper catalyst when synthesizing acrylamide by catalytic hydration of acrylonitrile (1
It is very convenient, and the catalyst can be used stably for a long period of time to convert acrylamide into 21. There is also no known method for manufacturing it commercially.

However, even if acrylamide is synthesized by catalytic hydration of acrylonitrile using the Raney copper catalyst, which has been commercialized as a practical catalyst, acrylamide cannot be synthesized with high activity and high selectivity as shown in the prior art. Currently, it is not possible to obtain the

An object of the present invention is to solve the problems of the prior art and provide a method for activating a Raney copper catalyst that is practical.

[Means for Solving the Problems] The present invention involves the catalytic synthesis of acrylamide by reacting acrylonitrile with water in a liquid phase in the presence of a practical Raney copper catalyst, in which the practical Raney copper catalyst used is preliminarily treated with ammonium chloride, ammonium sulfate, This is a method for activating a practical Raney copper catalyst, which is characterized by pre-treating and activating with an aqueous solution of at least one or two or more compounds selected from sulfur/lium chloride and sodium carbonate.

The details of the present invention will be sequentially explained below.

The Raney copper catalyst used in the present invention is based on known literature,
It is defined as follows. That is, aluminum, silica,
After producing an alloy of a metal that is soluble in alkali or acid, such as zinc, and a metal that is insoluble in alkali or acid, this is defined as a metal catalyst that is developed (raney copper catalyst). This means that the metal composition of the metal catalyst written after development is mainly copper.

Among Raney copper catalysts, aluminum is usually used as the alkali- or acid-soluble metal.

As a method 5 for preparing Raney copper catalyst, for example, alkali I/
Or if the metal soluble in acid is aluminum, 30 to 7
An alloy of aluminum and copper (Raney copper alloy) is produced by melting copper or copper and other metals in 0 weight 1% aluminum, then grinding it to an appropriate particle size, and then using alkali or acid to produce an alloy of aluminum and copper (Raney copper alloy). The deployment method is used.

As the developing method used at this time, a method of developing with alkali, acid, water or steam is used. As the alkali, hydroxide is commonly used.

The practical Raney copper catalyst used in the method of the present invention refers to a catalyst produced on an industrial scale, and is an alloy containing copper and aluminum as main components, that is, a Raney copper alloy, which is mixed with an alkali such as sodium hydroxide. After counter-questioning using
It shows what is considered a practical catalyst.

For example, practical Raney copper catalysts undergo the following process to
It has been J.

■Manufacturing and crushing process of Raney copper alloy The alloy is made by melting aluminum and copper in a weight ratio of 50/50.The alloy composition is mainly CuAIz. The bulk alloy is crushed to recover 80 mesh pieces of alloy.

(2) Development process The inside of the development tank containing a 10-30% aqueous solution of caustic soda is kept at 50°C while stirring. The alloy powder is introduced little by little so that the temperature inside the tank can be maintained at 50 to 60° C. by removing heat using a coil installed in the developing tank. After adding the entire amount of alloy powder, further increase the internal temperature to 50~50℃.
The development is completed by maintaining the temperature at 60°C and aging.

(2) Washing with water] - Process development path - After I', leave it to stand, discard the clear -L- water, add pure water and stir, and repeat this inclined washing operation 5 to 10 times.

Finally, the supernatant is discarded to obtain a developed catalyst immersed in water.

Even if the catalytic hydration reaction of acrylonitrile is carried out using the practical Raney copper catalyst obtained in this manner using I71, the rate of acrylamide formation is slow, and the acrylamide yield is usually 40 to 60 mol%, although it depends on the reaction conditions. This is extremely low in the range.

A further disadvantage is that the initial selectivity of the catalytic hydration reaction is extremely poor, resulting in by-products such as acrylic acid, hydroxypropionitrile, hydroxypropionamide, and oxypropiodinitrile (hereinafter referred to as AA, HPN, and HPM).
, OPN. ) etc. are produced in large quantities as by-products. The advantage of the catalytic hydration reaction of acrylonitrile using a Raney copper catalyst is that the selectivity of the catalyst is extremely good, for example, over 99%, so when producing acrylamide on a commercial scale, the purification process of acrylamide can be simplified and economical. It can also be advantageous. Considering the practicality, it is extremely disadvantageous to use a Raney copper catalyst due to its low selectivity.

The method of the present invention is related to activating such a practical Raney copper catalyst, and the Raney copper catalyst to be used is preliminarily treated with at least one selected from ammonium chloride, ammonium sulfate, sodium chloride, and sodium carbonate, or This can be achieved by treating ii'i1 with an aqueous solution of two or more compounds and then using it for the catalytic hydration reaction of acrylonitrile.

In the pretreatment according to the method of the present invention, the pretreatment temperature is usually in the range of 1 to 150°C, preferably 50 to 120°C.
The concentration of the pretreatment agent is preferably any concentration below the saturated solubility of the pretreatment agent at the pretreatment temperature, particularly in the range of 1 to 40% by weight.

If it is less than 1% by weight, a sufficient activation effect cannot be obtained, and 40
If it exceeds % by weight, there will be a large amount of unnecessary pretreatment agent and the amount of water used to wash the catalyst after pretreatment will be excessive, which is economically disadvantageous. The pretreatment time is preferably in the range of 0.5 to 5 hours.

Further, the pretreatment operation can be easily carried out by circulating the pretreatment aqueous solution in the reactor, but it can also be easily carried out by performing pretreatment outside the reactor and then charging it into the reactor.

The Raney copper catalyst pretreated by the method of the present invention is then thoroughly washed with water to remove and separate the pretreatment agent, and then,
Used in the catalytic hydration reaction of acrylonitrile.

When a practical Raney copper catalyst is used in the catalytic hydration reaction of acrylonitrile, the cause of insufficient activity and selectivity for acrylamide production is unknown, but several factors can be estimated from the catalyst manufacturing process. I can do it. That is, A: When producing Raney copper alloy, trace amounts of catalyst poisoning substances are mixed in with the raw materials copper and aluminum during the production of the alloy. A similar thing can occur in alloy crushing processes.

B. In the development process of Raney copper alloy, the catalyst is not developed uniformly because the development conditions are not strictly controlled. In particular, it is important to control the development temperature and caustic soda concentration. That is, unless these factors are controlled, the content of residual aluminum in the developed catalyst will not be constant.

Usually, it is important not to reduce most of the residual aluminum to O, but to allow a small amount of aluminum to remain, and the residual aluminum influences the performance and physical properties of the catalyst. Residual aluminum is an important factor that affects initial performance (activity and selectivity), catalyst particle size distribution, and particle strength.

C: In the water washing process of Raney copper catalyst, the quality of water used is not appropriate, impurities are mixed in, and water washing is insufficient.
If the pH of the immersion water in which the catalyst is stored is high, e.g.
1 or more, cases, etc. In particular, when a catalyst that has been stored in water with a high pH is drained and then used for the catalytic hydration reaction of acrylonitrile, the selectivity for acrylamide formation is extremely poor, and by-products such as AA, HPN, HPM, and OPN are noticeable. be.

D: It is known that the performance of Raney copper catalysts decreases when subjected to surface oxidation. Therefore, it is desirable to avoid contact with oxygen and oxygen afT gas during catalyst preparation and storage. In the production of practical Raney copper catalysts, contact with oxygen and oxygen-containing gases is avoided as much as possible in each step, for example, operations are performed under inert gas, deoxygenated pure water is used, Contamination with trace amounts of oxygen is unavoidable.
It is estimated that a portion of the catalyst surface is oxidized.

Although it is possible to infer the reason why the performance of practical Raney copper catalysts is low, it is difficult to identify the true cause, and it is assumed that the performance is reduced due to the combined effect of these causes. It's predictable.

According to the method of the present invention, a practical Raney copper catalyst is prepared in advance by:
To obtain acrylamide 1~ with high activity and high selectivity by performing a catalytic hydration reaction of fu'acrylonitrile after pretreatment with an aqueous solution of at least one species or two or more compounds selected from sodium carbonate. It becomes possible. The method of the present invention is considered to be an effective method for eliminating the above-mentioned complex causes.

Known technology, for example, Japanese Patent Publication No. 54-7754 describes a method for regenerating a Raney copper catalyst, in which a deactivated Raney copper catalyst is treated with caustic soda, caustic potash, calcium hydroxide, chloride, lithium,
It is proposed that a compound selected from one or a mixture of two or more of potassium carbonate, ammonium chloride, ammonium sulfate, etc. be immersed in water (8 liquids), then washed with water, and reused.

This technology is only effective for regenerating a deactivated Raney copper catalyst after producing acrylamide over a long period of time through the catalytic hydration reaction of acrylonitrile, and its scope is limited to deactivated Raney copper catalysts. It can be thought that.

Catalytically hydrating acrylonitrile using the method of the invention,
The method for synthesizing acrylamide is as follows.

The catalyst is used in powder form as a suspended bed, or in granular form as a fixed bed, and a flow or batch reaction type is adopted. When carrying out the reaction on a commercial scale, a method is often used in which a Raney copper catalyst is suspended in a flow-through stirred tank type reactor and the reaction is carried out continuously.

The ratio of acrylonitrile and water in the reaction is generally better when there is an excess of water, and the rate of acrylamide production is faster.
Considering the productivity, reactor capacity, etc., the weight ratio is preferably in the range of 60/40 to 5/95, and the weight ratio is preferably in the range of 50/50 to 10/90.

The reaction temperature is preferably in the range of 50 to 200°C, and a range of 70 to 150°C is particularly suitable from the viewpoint of preventing side reactions or polymerization and productivity. Although the preferred residence time is related to the reaction temperature, it is in the range of 0.5 to 5 hours, and in particular, in the range of 1 to 3 hours, side reactions or polymerization prevention and ilE
It is convenient in terms of productivity.

The conversion rate of acrylonitrile to acrylamide is preferably 10 to 98%, more preferably 3D-95%.
It is. Considering the prevention of acrylamide polymerization, counter pressure,
It is possible that unreacted acrylonitrile remains in the system.
It's fried.

At the IT ratio of acrylonitrile and water, the reaction temperature, and the conversion rate of acrylonitrile described in -1-, the three components of unreacted acrylonitrile, unreacted water, and produced acrylamide may not form a homogeneous solution system. . In order to do this, the synthesized acrylamide may be diluted and added to the reaction system again, or another inert solvent may be used.

It is desirable to avoid contact of the Raney copper catalyst with oxygen gas and oxygen-containing gas before and during use.

Oxygen reacts with the catalyst and does not impair or even improve the activity of the catalyst within certain limits, but beyond that it impairs the activity and even increases the This causes an increase in by-products.

Raney copper catalyst, acrylonitrile, fed to the reactor
As mentioned above, dissolved oxygen contained in water, solvent, etc. impairs catalyst activity and increases by-products such as HPN, HPM, and OPN, so it is important to remove it sufficiently before supplying it to the reactor. desirable. For the same reason, it is desirable to maintain an atmosphere in the reactor that does not contain oxygen gas.

For this reason, the raw material acrylonitrile and water preferably have a dissolved oxygen content of 5 ppm or less, more preferably 1 ppm.
It is preferred that the following supplementary oxygen be supplied to the reactor.

The inside of the reactor is maintained at the vapor pressure at the above-mentioned temperature and composition or at a pressure obtained by adding an inert gas such as nitrogen to the vapor pressure, and the pressure is usually in the range of normal pressure to 20 atmospheres.

Although the hydration reaction proceeds even if the amount of the catalyst used in the present invention is extremely small, the preferred amount of the catalyst is, for example, when the catalyst is used as a suspended bed, per mole of acrylonitrile.
0. A range of O1 to too g is preferred. In order to stably maintain the activity of the catalyst in the reaction system, copper salts such as copper nitrate, copper sulfate, copper acetate, etc. are added to the reaction solution at a concentration of 2 to 200 ppm as Cu"° relative to the water in the reaction solution. It is preferable to add within the range of .

When carrying out the present invention, it is desirable that the pH of the reaction solution is weakly acidic, neutral or slightly alkaline. usually,
In the reaction system in which the amount of Cu'' added is optimized, the pH
Even without adding a regulator, a buffer solution, etc., the pH of the reaction solution is in the range of 5 to 9, and it is often possible to carry out the reaction as is.

The present invention will be further explained with reference to Examples and Comparative Examples.

[Example 1 Example 1 <Catalyst pretreatment> Practical Raney copper catalyst manufactured by Naruni Co., Ltd. (improved CDT-60)
) was subjected to the following pretreatment. This Raney copper catalyst was stored in a suspended state in pure water at a slurry concentration of 50% by weight. In terms of composition, the amount of residual aluminum is 0.83
% by weight. Raney copper catalyst 3 mI was placed in a four-hole glass flask equipped with a stirrer, a thermometer, and a nitrogen inlet.
A 2% by weight ammonium chloride aqueous solution 30 was prepared by dissolving ammonium chloride in pure water that had been deoxidized in advance.
Prepare 0ml. However, all of these operations are carried out in a nitrogen box to prevent contact between the catalyst and oxygen as much as possible. The flask is immersed in an oil bath, and the temperature is gradually raised to 60°C while stirring the inside of the flask. Continue heating and stirring at 60°C for 2 hours. After heating, the mixture is cooled to room temperature and the catalyst and solution are separated. Subsequently, the catalyst is thoroughly washed with water using deoxygenated pure water using a decanting method. The above operations are also performed while avoiding contact with oxygen as much as possible. After washing with water, the catalyst was stored immersed in water.

Reaction> After purging the inside of an autoclave made of stainless steel (SUS-31,6) and having an inner volume of IC with nitrogen gas, 17 g of the Raney copper catalyst pretreated as described above suspended in deoxidized pure water was added. I prepared it. Further, 85 g and 200 g of acrylonitrile and pure water, which had been deoxidized in advance, were charged. The autoclave is equipped with a stirring device, a thermometer, and a small stainless steel sintered metal filter (pore size 2μ) inside.
is installed, and after the reaction, the reaction solution can be extracted through this filter.

The autoclave was immersed in an oil bath, and the temperature was gradually raised to 120°C while stirring the inside well, and the reaction was continued for 2 hours. After the reaction, the reaction solution is cooled to room temperature, extracted through a filter, and subjected to liquid chromatography (LC).
) and gas chromatography (GC) to analyze unreacted acrylonitrile and reaction products.

<Reaction Results> The acrylonitrile conversion rate was 87.2%, and the acrylamide yield and selectivity were 87.1% and 99.9%, respectively.

As by-products, only small amounts of hydroxypropionitrile (HPN) and acrylic acid FAA) are produced, and β-hydroxypropionamide (HPM) and oxybropiodinyl
No formation of rill (OPN) was observed.

Comparative Example 1 A hydration reaction of acrylonitrile was carried out in the same manner as in Example 1 using the same Raney copper catalyst as in Example 1 and using 17 g of ammonium chloride water (without pretreatment with liquid). At this time, the acrylonitrile conversion rate was 575
%, acrylamide yield 53.7%, AA and)
(The yield of PN, HPM, and OPN was 23.5.0.
59. Produced at 0.71%. It is clearly seen that a large amount of by-products has a low selectivity for the production of bovine acrylamide.

Example 2 Example 1 except that the same Raney copper catalyst as in Example 1 was used, and the pretreatment conditions with ammonium chloride j and aqueous solution were changed to 8 wt% ammonium chloride aqueous solution, 300 mff, 60° C., 2 hours. It was processed in the same way.

The hydration reaction of acrylonitrile was carried out in the same manner as in Example 1 using 17 g of the treated catalyst. At this time, the conversion rate of acryloni-1 to helyl was 875%, and the acrylamide yield was 8.
The percentage is 7.5%, and only a small amount of AA is produced, and the production of other side organisms is rare.

Example 3 Practical Raney copper catalyst, Nauni Co. product (improved type C1,) T-
60), but the composition was different from that of Example I, that is, the amount of residual aluminum was 120%.

This Raney copper catalyst was also treated in the same manner as in Example 1.
After treatment with a wt% ammonium chloride aqueous solution,
A hydration reaction of acrylonitrile was carried out under the same conditions using 17 g of the treated catalyst.

At this time, the conversion rate of acrylonitrile was 90.6%, the yield of acrylamide was 90.6%, and no by-products were observed at all except for a small amount of AA.

Comparative Example 2 Using the Raney copper catalyst used in Example 3, ammonium chloride water? 17g of the catalyst without pretreatment with 8 liquids.
The hydration reaction of acrylonitrile was carried out in the same manner as in Example 1 using

2, the acrylonitrile conversion rate was 66.5%, the acrylamide yield was +64.7%, and the by-products were AA, I-fPN, HPM, and OPN, respectively.
0.35.042% produced. It is clear that there are many by-products.

Example 4 Using the same Raney copper catalyst as in Example 3, but with 2% by weight ammonium sulfate in water? The catalyst was heated to 60°C using g if2.
, pretreated for 2 hours. The processing operations are the same as in Example 1. A hydration reaction of acrylonitrile was carried out in the same manner as in Example 1 using 17 g of the treated catalyst. Results similar to Example 3 were obtained, with an acrylonitrile conversion rate of 850% and an acrylamide (ζ) yield of 84.8%.

Example E), 6.7 Comparative Example 3, 4.5 A product made by another company was used as a practical Raney copper catalyst.

Namely, Company N (N-254D), Company S (R-100), R
There are three types: Company (R-300).

Improved CL) T-60 used in Example 1, 2% by weight was added to an islanded ammonium aqueous solution at 60°C, similar to the Raney copper catalyst.
Perform 0i1 treatment for 2 hours and use 17 g of treated catalyst,
The hydration reaction of acrylonitrile was carried out under the same conditions as in Example 1. The results are shown in Table 1. Examples 5, 6, and 7 are each N
These results correspond to 254D, R-100, and R-300.

Table 1 also shows the results of the hydration reaction of acrylonitrile carried out in the same manner as in Example 1 without pretreatment with an aqueous ammonium chloride solution.

Comparative Examples 3 and 4.5 are N-254D, R100, and R-, respectively.
This is the result corresponding to 300.

Table ■ [Effects of the Invention] In the method of the present invention, by pre-treating a practical Raney copper catalyst with an aqueous ammonium chloride solution, the activity and selectivity of acrylamide production through the catalytic hydration reaction of acrylonitrile can be significantly increased. Therefore, it is extremely effective industrially.

Claims (1)

[Claims] Acrylonitrile and water in the presence of a practical Raney copper catalyst,
When catalytically synthesizing acrylamide by reaction in a liquid phase, the catalyst is pretreated and activated with an aqueous solution of at least one or more compounds selected from ammonium chloride, ammonium sulfate, sodium chloride, and sodium carbonate. Characteristic catalyst activation method.