JP3683916B2 - Method for producing acrylamide - Google Patents

Description

【００９５】
【表２】

【００９６】
【発明の効果】
接触水和法アクリルアミド原料用のアクリロニトリルは、不純物の少ない高品質なものを用いないと、良い品質のアクリルアミドが得られないが、本発明の方法により、通常品質のアクリロニトリルを用いても、接触水和反応前に簡単なカラム吸着処理を行うだけで、高品質のアクリルアミドが得られ、このアクリルアミドは凝集剤用ポリアクリルアミドの製造原料として特に有用である。また、接触水和法用に一般的に使用されている高度に蒸留精製したアクリロニトリルに対し、本発明を適用すると、より高品質なアクリルアミドが得られる。[0001]
[Industrial application fields]
The present invention relates to a method for producing acrylamide by catalytic hydration of acrylonitrile with water in the presence of a copper-based catalyst. More particularly, the present invention relates to a method for purifying a raw material acrylonitrile for producing a high-quality acrylamide capable of producing a polymer having a sufficiently high molecular weight and good water solubility.
[0002]
[Prior art]
Acrylamide is conventionally used as an acrylamide polymer in papermaking chemicals, flocculants, oil recovery agents, and the like, and has a wide range of uses as a raw material comonomer for various polymers. The production method of acrylamide used for these applications has long been produced by the so-called sulfuric acid method, but recently, a contact method in which a reaction is carried out in the presence of a copper-based catalyst has been developed. It is industrially implemented.
[0003]
Among the above-mentioned uses of acrylamide, in particular, a flocculant has recently been used for wastewater treatment and the like, and a great effort has been made to improve quality performance. Among them, the acrylamide polymer used as the flocculant has a remarkable tendency to increase the molecular weight, which is said to directly affect the performance, and recently, a polymer having a high molecular weight of about 10 million or more, particularly about 15 million is demanded. This is much higher than the molecular weight required for acrylamide polymers or other polymers required for other applications, which is usually 1 million or less. In addition, since the acrylamide polymer obtained in addition is usually used as a flocculant dissolved in water, it is necessary to dissolve it quickly and without leaving insoluble components. In addition, due to the toxicity of the acrylamide monomer, it is also necessary that the unreacted monomer in the polymer is a trace amount of 0.2% by weight or less, for example.
[0004]
These requirements are properties that are difficult to achieve at the same time as high molecular weight, and that is why significant efforts have been made to achieve them. In addition, although such a high molecular weight acrylamide polymer is only one use of acrylamide, it cannot be widely used for general purposes unless it is suitable for such use. Also relates to the production of acrylamide that can be used for such applications.
[0005]
The molecular weight referred to in the present invention is based on the test method shown in Example 1 to be described later, and the water solubility is a problem because the polymer obtained in an aqueous medium is usually dried. This is a case where the moisture content is 20% by weight or less, particularly about 10% by weight, and the water solubility referred to in the present invention is mainly used in this sense.
[0006]
In order to produce such an acrylamide polymer having a high molecular weight and sufficient water solubility, it is said that it depends not only on the production method of the polymer but also on the quality of the acrylamide, and also the influence of the quality of the raw material acrylonitrile. Is said to be large.
[0007]
Acrylonitrile is usually synthesized by ammoxidation of propylene. Acrylonitrile is mainly used for acrylic fiber and ABS resin. Acrylonitrile for the acrylamide raw material of catalytic hydration method requires high quality with less impurities than these main applications, and measures such as strengthening the operating conditions of the distillation purification process are usually required to meet this requirement. It is common.
[0008]
Several methods have been proposed in order to obtain acrylonitrile suitable for the catalytic hydration method.
[0009]
For example, in Japanese Patent Application Laid-Open No. 63-118305, acrylonitrile in acrylonitrile as a raw material is brought into contact with an H-type cation exchange resin to make it 200 ppm or less, more preferably 25 ppm or less. Acrylamide synthesized by a hydration reaction in the presence of a copper-based catalyst is more stable than acrylamide synthesized in the same way from acrylonitrile containing oxazole, and the viscosity of the aqueous solution as a polymer is high. In addition, as a method for regenerating the cation exchange resin, it is described that the cation exchange resin is brought into contact with hot water, water vapor, methanol, a slightly acidic aqueous solution, or a mixture thereof.
[0010]
In Japanese Patent Publication No. 57-26264, when acrylonitrile purified with an inorganic acid or an acidic cation exchange resin is subjected to a hydration reaction in the presence of a copper-based catalyst, deterioration in catalytic activity can be prevented as compared with a case where it is not purified. It is written.
[0011]
In Japanese Examined Patent Publication No. 57-26586, acetylacetone or the like is reacted with acrolein in acrylonitrile, and the reaction product is separated from acrylonitrile by distillation or the like, so that the acrolein concentration is 1.5 ppm or less, more preferably 0.8. It is stated that when the concentration is 8 ppm or less, acrylamide obtained by hydration reaction of acrylonitrile in the presence of a copper-based catalyst can be obtained as a water-soluble polymer.
[0012]
Japanese Patent Publication No. 58-1108 discloses that acrolein in acrylonitrile is reduced to 0.8 ppm or less by bringing it into contact with a porous ion exchange resin having primary and / or secondary amino groups as exchange groups. Acrylamide obtained by hydration in the presence of a catalyst is described as having good water solubility and a sufficiently high molecular weight when made into a polymer.
[0013]
Similarly, Japanese Patent Application Laid-Open No. 58-134063 discloses that aldehydes in acrylonitrile, substantially acrolein, are obtained by contacting with a gel-type weakly basic ion exchange resin having primary and / or secondary amino functional groups. When the acrylamide is reduced, the water solubility of the polymer obtained by polymerizing the polymer is improved, and the water solubility of the polymer obtained by polymerizing the acrylamide itself is improved by performing the same treatment on the acrylamide itself. In addition, it is described that a sufficiently high molecular weight can be obtained.
[0014]
In Japanese Patent Publication No. 61-9303, after the content of acetonitrile is reduced to 20 ppm or less, more preferably 10 ppm or less by water extraction and / or water extraction distillation of acrylonitrile, It is described that acrylamide obtained by a hydration reaction at a temperature of ˜140 ° C. improves the water solubility in the case of a polymer.
[0015]
Further, in US Pat. No. 2,444,589 established in 1948, acrylonitrile synthesized from inorganic cyanide and organic substance contains a small amount of ionic impurities and a small amount of neutral impurities, and these impurities are synthesized from acrylonitrile as a raw material. It points out that it interferes with the isolation of the reaction product and reduces the yield. This acrylonitrile was treated with a cation exchanger (for example, a condensate of phenol and formaldehyde, or sulfonated coal) and an anion exchange resin (for example, a condensate of guanidine, urea, formaldehyde, etc.) to remove ionic substances. Thereafter, when a treatment with a decoloring agent (for example, activated carbon) is performed, decolorization that could not be performed by each of the ion exchange material and the decolorizing agent becomes possible. In the examples, the cation exchanger, the anion exchange resin, and the activated carbon It is described that the acrylonitrile treated in sequence increases the polymerization rate of acrylonitrile when polymerized.
[0016]
[Problems to be solved by the invention]
According to the knowledge of the present inventors, even if oxazole, acrolein, acetonitrile, etc. in acrylonitrile are removed using the above technique, it can be obtained by contact hydration with water in the presence of a copper catalyst. The quality of acrylamide is insufficient with respect to the water solubility and molecular weight of an acrylamide polymer obtained by polymerizing it alone or with other comonomers.
[0017]
In addition, by strengthening the operation conditions of the distillation purification process that is currently generally performed, the method of producing acrylonitrile with less impurities and using it as a raw material for acrylamide production, such as recovery loss and steam in the distillation purification process, etc. This comes at a great cost, such as a deterioration in the basic unit of service. Furthermore, when the low-impurity acrylonitrile obtained in this way is used for catalytic hydration, the quality of the acrylamide is generally good, but sometimes a product of poor quality is produced, resulting in poor quality stability and high quality acrylamide. As a commercial production technology, it is insufficient.
[0018]
Examples of using the above-described cation exchanger, anion exchange resin, and activated carbon are described. At the time of establishment of US Pat. No. 2,244,589 in 1948, (i) a method for producing acrylonitrile by ammoxidation of propylene and (B) None of the methods for producing acrylamide obtained by the hydration reaction of acrylonitrile in the presence of a copper-based catalyst has been industrialized. According to the method of this patent, (iii) purification of acrylonitrile produced by the ammoxidation method of propylene, and (d) acrylamide obtained by catalytic hydration of acrylonitrile and water in the presence of a copper-based catalyst. The effect relating to the physical properties of acrylamide polymers obtained by polymerization alone or with other comonomers is not described in this patent, and there are no known examples so far.
[0019]
Furthermore, in the above-mentioned examples, acrylonitrile is treated in the order of a cation exchanger, an anion exchange resin, and activated carbon, but this patent claims that coloring and the like are caused by removing ionic substances. In other words, the cation exchange treatment and the anion exchange treatment in the ion exchange treatment may be performed before the decoloring agent (for example, activated carbon) treatment. The order of the exchange process is not limited.
[0020]
[Means for Solving the Problems]
Therefore, the present inventors have arrived at the present invention as a result of intensive studies on a method for purifying acrylonitrile as a raw material in order to obtain sufficient water solubility and molecular weight of an acrylamide polymer obtained by polymerizing acrylamide.
[0022]
  One specific means of the present invention is that after at least two steps of contacting acrylonitrile with a strongly acidic cation exchange resin and then with a resin having primary and / or secondary amino groups, the copper-based catalyst In the method of hydration reaction in the presence ofis there.
[0023]
In the present invention, acrylonitrile is produced by an ammoxidation method of propylene,
A method in which acrylonitrile is contacted with a strongly acidic cation exchange resin, then contacted with a resin having a primary and / or secondary amino group, and further contacted with activated carbon;
A method in which acrylonitrile is contacted with a resin having primary and / or secondary amino groups, then contacted with a strongly acidic cation exchange resin, and further contacted with activated carbon; and
A method in which acrylonitrile is brought into contact with a strongly acidic cation exchange resin, then brought into contact with activated carbon, and further brought into contact with a resin having a primary and / or secondary amino group is preferred.
[0024]
A method for producing acrylonitrile by ammoxidation of propylene, which is a preferred object in the present invention, is a mixed gas of propylene, ammonia, oxygen or air, such as a molybdenum-bismuth catalyst, a uranium-antimony catalyst, or iron. -A production method by a gas phase ammoxidation reaction in which a direct reaction is carried out in the presence of a catalyst such as an antimony catalyst.
[0025]
Acrylonitrile is usually recovered from the synthesis reaction gas by absorbing it into water, and is separated from by-products such as hydrocyanic acid, acetonitrile, acetone, acrolein, methacrylonitrile, oxazole, and aldehydes in the subsequent purification and separation step. Distillation is mainly used as a purification separation method, but when producing acrylonitrile for acrylamide raw materials, it is generally practiced to strengthen the distillation purification conditions and reduce impurities compared to the usual, for example, fiber raw materials. .
[0026]
However, when the present invention is applied, normal quality acrylonitrile can also be used for acrylamide raw materials.
[0027]
Next, an outline of a method for producing acrylamide to which the present invention is applied will be described.
[0028]
Examples of copper catalysts used in the method of the present invention include
(A) A combination of copper and copper ions in the form of copper wire, copper powder, etc.
(B) What is obtained by reducing a copper compound with a reducing agent (reduced copper),
(C) obtained by decomposing a copper compound with heat (decomposed copper), and
(D) Products obtained by developing Raney alloy with alkali (Raney copper)
There is.
[0029]
As an example of the manufacturing method of the above reduced copper,
(1) A method of reducing copper oxide with hydrogen, carbon monoxide, or ammonia in a gas phase,
(2) A method of reducing a copper salt or hydroxide with formalin, hydrazine, or sodium borohydride in an aqueous solution, and
(3) Method of reducing copper salt or hydroxide with elemental aluminum, zinc or iron in aqueous solution
The main catalyst component of what is obtained is considered to be elemental copper.
[0030]
As an example of the above-mentioned method for producing decomposed copper,
(1) A method of thermally decomposing copper hydride obtained by treating a copper compound with sodium hypochlorite or the like in alkaline water,
(2) A method for thermally decomposing copper formate or oxalate,
(3) a method for thermally decomposing so-called cluster copper disclosed in JP-A-49-108015, and
(4) Method of adding copper acetylide or copper nitride directly to the hydration reaction system of acrylonitrile
The main catalyst component of what is obtained is considered to be elemental copper including that of item (4).
[0031]
As an example of the manufacturing method of the above Raney copper,
(1) A method of developing a copper-aluminum alloy almost completely with caustic soda, sulfuric acid, water, organic amine, etc., and
(2) A method in which a copper-aluminum alloy is partially developed with caustic soda, sulfuric acid, water, organic amine, etc., and a part of aluminum is left together with copper.
The main catalyst component of what is obtained is considered to be elemental copper.
[0032]
These copper catalysts may be supported on a commonly used carrier, and may contain a metal other than copper, for example, chromium or molybdenum.
[0033]
Although these copper-based catalysts have different catalytic activities depending on their adjustment methods, for example, there is no difference in reaction mode such as side reaction due to differences in reduced copper, copper hydride, Raney copper, etc. It has the same tendency regarding the generation tendency of impurities.
[0034]
Desirably, the catalyst avoids contact with oxygen and oxygen-containing gases before and after use. The reason is that oxygen impairs the activity as a catalyst and increases by-products such as ethylene cyanohydrin.
[0035]
The hydration reaction of acrylonitrile of the present invention is performed as follows in the presence of the copper-based catalyst. The reaction is carried out in a liquid phase suspension bed or a fixed bed catalyst bed, in a flow-through mode or in a batch mode.
[0036]
The weight ratio of acrylonitrile to water subjected to the hydration reaction is substantially arbitrary, but is preferably 60:40 to 5:95, and more preferably in the range of 50:50 to 10:90. It is. Moreover, the reaction rate of acrylonitrile becomes like this. Preferably it is 10-98%, More preferably, it is the range of 30-95%.
[0037]
The reaction temperature in the hydration reaction between acrylonitrile and water is preferably 50 to 200 ° C, more preferably 70 to 150 ° C.
[0038]
The inside of the reactor is maintained at a vapor pressure at the above-described temperature and composition, or a pressure obtained by adding an inert gas such as nitrogen thereto, and the pressure is usually atmospheric pressure to 10 atm. Since dissolved oxygen contained in the catalyst, acrylonitrile, water, etc. supplied to the reactor impairs the activity of the catalyst and increases by-products such as ethylene cyanohydrin, remove them sufficiently before supplying them to the reactor. For the same reason, it is desirable to maintain an atmosphere containing no oxygen in the reactor. The reaction liquid taken out from the reactor after the hydration reaction is mainly composed of unreacted acrylonitrile, unreacted water, and acrylamide, and further contains a by-product such as ethylene cyanohydrin and copper.
[0039]
The reaction solution obtained by the above reaction is subjected to a normal evaporation or distillation operation if necessary to obtain a concentrated aqueous acrylamide solution, and unreacted acrylonitrile and water are recovered by distillation. These recovered materials can be reused as new reaction raw materials.
[0040]
The content of impurities, etc. in the acrylonitrile described in the present invention refers to the content in the newly supplied acrylonitrile, not the total content of the newly supplied portion and the recovered reused portion. .
[0041]
The acrylamide aqueous solution obtained by concentrating the above reaction liquid (hereinafter, these liquids are abbreviated as acrylamide aqueous solution) is then subjected to cation exchange treatment, chelate resin treatment, anion exchange treatment, air or oxygen gas treatment, activated carbon treatment, and the like. It is purified by various purification methods. Moreover, what is called synthetic adsorption resin (For example, the product name: adsorption resin made by Hokuetsu Carbon Industry Co., Ltd.) used by the method similar to activated carbon or an ion exchange resin can also be used. During or after these purification steps, the aqueous acrylamide solution may be subjected to the above-described concentration treatment, or may be re-concentrated.
[0042]
Next, the purification method of acrylonitrile will be described in detail.
[0043]
Strongly acidic cation exchange resins (A) used for the purification of acrylonitrile are, for example, Lebatit S-100 (trade name, manufactured by Bayer), Diaion SK1B (trade name, manufactured by Mitsubishi Kasei), Dowex HCR-W2 ( Gel type resin such as trade name, manufactured by Dow Chemical Co., Ltd., or macroporous type such as, for example, Lebatit SP-112 (trade name, manufactured by Bayer), Dowex MSC-1 (trade name, manufactured by Dow Chemical) Any of the resins may be used, which is pre-treated with a dilute acid to form an H type, and can be used as it is after being sufficiently washed with water. More preferably, this is performed by hot air, dry nitrogen, or drying under reduced pressure. Use after thoroughly drying.
[0044]
In the case of using a resin having primary and / or secondary amino groups, it is sufficient that either or both of primary and secondary amino groups are present as an exchange group. For example, Diaion WA-20 (product Name, manufactured by Mitsubishi Kasei Co., Ltd.) or a gel-type resin such as Levacit OC1059 (trade name, manufactured by Bayer). I can do it. Of course, after pretreatment with a dilute alkali, it may be used after sufficiently washing with water. Alternatively, the resin after washing with water may be sufficiently dried by hot air, dry nitrogen, or reduced pressure drying regardless of the presence or absence of pretreatment with a dilute alkali.
[0045]
When contacting with activated carbon, the type of activated carbon to be used is not particularly limited. For example, call base activated carbon such as Calgon CPG (trade name, manufactured by Calgon) or Shirasagi LHc (trade name, Takeda Pharmaceutical Company Limited). Can be used. These activated carbon can use a commercially available thing as it is. Of course, it may be used after washing with water, or after washing with water, it may be used after sufficiently drying with hot air, dry nitrogen, or drying under reduced pressure.
[0046]
These resins and activated carbon can be packed in towers and continuously contacted and purified with acrylonitrile as a fixed layer, and can also be used in batch systems. However, it is desirable to use the former for reasons such as purification efficiency and ease of operation.
[0047]
  In the present invention, in the purification treatment of acrylonitrile, (b) contact with a strongly acidic cation exchange resin is essential, but (b) a resin having a primary and / or secondary amino group and / or (c) ) Contact with activated carbon. As order of contact,
(1)(B)-(b)
(2)(I)-(C)
(3)(B)-(b)-(c)
(Four)(B)-(b)-(c)
(Five)(I)-(C)-(B)
The method is good,(1) , (3) ~ (Five) IsBoth are within the scope of the present invention.(1) , (3) ~ (Five)In the refining treatment, a method of contacting and purifying with (iii) activated carbon in advance is also good and is within the scope of the present invention.As a reference example that can obtain the same effect as this case (2) Can be mentioned.
[0048]
When these resins and activated carbon are packed in a tower and used, the tower may be made of a material that is not affected by acrylonitrile such as SUS-304.
[0049]
The liquid temperature during treatment in these towers is usually 5 to 50 ° C, preferably 15 to 30 ° C. The flow rate of acrylonitrile through the column is selected from a flow rate of about 0.1 to 50 times, preferably about 0.5 to 10 times per hour, relative to the capacity of the packed resin or activated carbon.
[0050]
In addition, (a) the strongly acidic cation exchange resin is in contact with acrylonitrile, for example, when the outflow of a basic substance typified by oxazole is confirmed, water at normal temperature to 100 ° C., water vapor, methanol, dilute acid, Or it can reproduce | regenerate easily by making it contact with these mixtures.
[0051]
The purified acrylonitrile thus obtained is used to produce acrylamide by contact hydration with water using a copper catalyst, and this acrylamide is used to polymerize acrylamide alone or with other comonomers. When evaluated as a polymer, a remarkable improvement in water solubility and a sufficiently high molecular weight were obtained.
[0052]
  On the other hand, the above(1) , (3) ~ (Five)Purification methods other than, for example, (a) (i) purification treatment of acrylonitrile only with strong acid cation exchange resin, (b) (b) purification treatment of acrylonitrile only with resin having primary and / or secondary amino groups, (C) (c) Purification of acrylonitrile using only activated carbon, or (d) (a) A method in which a strongly acidic cation exchange resin is contacted last, for example, (b)-(i), (b)-(c) -(A) When other methods were performed in the same manner as described above, the removal of both oxazole and acrolein was analyzed in the treatment of (a), acrolein in the treatment of (b), and the treatment of (d). Confirmed by
[0053]
However, acrylamide is produced by contact hydration with water using a copper-based catalyst as described above, regardless of which acrylonitrile is subjected to the treatments (a), (b), (c) and (d). In this case, the water solubility of the acrylamide polymer obtained by polymerizing it alone or with another comonomer was not satisfactory.
[0054]
Regarding this reason, only oxazole is removed in (a) and only acrolein is removed in (b), which seems insufficient. The removal of both of them (d) had no effect on improving acrylamide quality. (I) When a strongly acidic cation exchange resin was put last, impurities such as aldehydes other than acrolein increased on the contrary. Is not considered good.
[0055]
  Above(1) , (3) ~ (Five)Among the methods, especially(3)The best results, that is, high-quality acrylamide, are obtained by contacting (b) a strongly acidic cation exchange resin, (b) a resin having a primary and / or secondary amino group, and (c) activated carbon. I can do it.
[0056]
The reason for this is not clear, but the purification effect of acrylonitrile according to the present invention is that the strongly acidic cation exchange resin, the resin having primary and / or secondary amino groups, or activated carbon, each independently removes impurities. In addition to certain harmful impurities, (b) jointly in the order of (a) a strongly acidic cation exchange resin, (b) a resin having primary and / or secondary amino groups, and then (c) activated carbon. It is thought that it is acting and removed.
[0057]
Next, a method for producing a high molecular weight acrylamide polymer used for a flocculant or the like is as follows.
[0058]
Acrylamide is used alone or in combination with other vinyl polymerization type comonomer. As comonomer, acrylic acid and methacrylic acid or their water-soluble salts: alkylaminoalkyl esters of acrylic acid and methacrylic acid or their quaternary ammonium derivatives: N- (dimethylaminopropyl) methacrylamide or their quaternary ammonium derivatives : Vinyl acetate: Acrylonitrile and the like. The mixing ratio of these comonomers and acrylamide is usually 100 mol or less, particularly 50 mol or less, per 100 mol of acrylamide.
[0059]
Polymerization of acrylamide and comonomer is carried out by a known method such as aqueous solution polymerization or emulsion polymerization. Among these, a general method of aqueous solution polymerization, which is most widely used, will be described.
[0060]
The total concentration of acrylamide and comonomer is usually 5-60% by weight. Examples of the polymerization initiator include peroxides such as potassium persulfate, ammonium persulfate, hydrogen peroxide, and benzoyl peroxide: azobisisobutyronitrile, 2 · 2′-azobis (4-amidinopropane) dihydrochloride, 4・ Azo-based free radical initiators such as 4′-azobis (sodium 4-cyanovalerate): a so-called redox system using the above-mentioned peroxide in combination with a reducing agent such as sodium bisulfite, triethanolamine, or ferrous ammonium sulfate. A catalyst is used.
[0061]
Regarding the temperature of the polymerization reaction, it is difficult to control the temperature by cooling or the like when the total concentration of acrylamide and comonomer is 15% by weight or more and the molecular weight of the obtained polymer is 10 million or more. In general, an adiabatic polymerization method is employed. In this case, the temperature of the polymerization system is increased by the heat of polymerization as the polymerization proceeds. In this case, the temperature at the start of polymerization is often selected from the range of −5 to 40 ° C., and the temperature after completion of the reaction reaches a high temperature of 55 to 100 ° C., for example.
[0062]
In order to increase the molecular weight to 10 million or more, particularly about 15 million, the total concentration of acrylamide and comonomer, the type and concentration of the polymerization initiator used, and the reaction temperature are devised. Although the same contrivance is made to make unreacted acrylamide in a trace amount of 0.2% by weight or less, for example, many methods for causing two or more kinds of polymerization initiators to act in different temperature ranges have been proposed and implemented. Yes.
[0063]
What is obtained by the polymerization reaction as described above is a water-containing gel, that is, a rubber-like gel containing water as it is to make acrylamide and a comonomer into an aqueous solution. Usually, this is a dry powder product. Therefore, a process such as extraction of water or dehydration by heat drying or crushing or pulverization of the hydrated gel or dried gel is added. Prior to or during these treatments, the acrylamide polymer may be chemically modified, for example, by heating caustic soda into a hydrous gel and heating to convert a part of the amide group into a carboxyl group.
[0064]
As described above, as a result of increasing the molecular weight, reducing the unreacted monomer, forming a dry powder, and in some cases performing chemical modification, the resulting polymer often becomes difficult to dissolve in water, such as a flocculant It tends to lose its value as a product. In order to solve the problem, a method of adding an insolubilization inhibitor before, during or after the polymerization reaction, a method using a specific polymerization initiator, or a method of drying a hydrogel under specific conditions is performed.
[0065]
Acrylamide to which the method of the present invention is applied is produced by a method comprising the purification of acrylonitrile, the hydration reaction, the distillation operation, various purification treatments and other incidental steps as described above. It is used for the production of molecular weight acrylamide polymers.
[0066]
Next, the present invention will be described in more detail with reference to examples.
[0067]
Example 1
<Purification of acrylonitrile>
According to a conventional method, 1 liter of strongly acidic cation exchange resin Levacit S-100 (trade name, manufactured by Bayer), which was treated with dilute hydrochloric acid to form H and washed sufficiently with water, was dried at 90 ° C. and normal pressure for about 8 hours. An SUS-304 column having an inner diameter of 70 mm and a length of 400 mm was packed. After 1 l of resin Diaion WA-20 (trade name, manufactured by Mitsubishi Kasei Co., Ltd.) having primary and / or secondary amino groups was washed with water, it was packed into a SUS-304 column having an inner diameter of 70 mm and a length of 400 mm. After 1 l of activated carbon Calgon CPG (trade name, manufactured by Calgon) was washed with water, it was similarly packed into a column made of SUS-304 having an inner diameter of 70 mm and a length of 400 mm.
[0068]
The three columns were connected in the order of Levacit S-100 to the first tower, Diaion WA-20 to the second tower, and Calgon CPG to the third tower. Acrylonitrile produced by a propylene ammoxidation method was passed through this at a flow rate of 6 l / hr. In addition, although the impurity concentration of acrylonitrile (LOT-1) used for the raw material was shown in Table 1, it is a normal quality product used for acrylic fiber manufacture etc. The impurity concentration of purified acrylonitrile after passing through the column is also shown in Table 1.
[0069]
<Manufacture of acrylamide>
Acrylamide was obtained by using the purified acrylonitrile obtained by the above method and performing a hydration reaction in the presence of a copper catalyst as follows.
Hydration catalyst:
A Raney copper alloy having a mesh size of 80 mesh or less was developed using a caustic soda using a conventional method and washed to produce a Raney copper catalyst. During production and subsequent handling, contact with oxygen-containing gases such as air was avoided.
Catalytic hydration reaction:
400 g of the above catalyst was charged in a reactor of about 2 liters made of SUS and equipped with a stirrer and a catalyst separator, and acrylonitrile excluding dissolved oxygen using nitrogen gas and water were previously added at 600 g / hr and 900 g, respectively. / Hr and fed at a rate of 120 ° C. The reaction solution is stirred together with the catalyst to form a suspension, and then passed through the catalyst separator and taken out from the reactor as a solution containing almost no catalyst. This reaction was continued for 3 days.
concentrated:
The obtained reaction solution was subjected to batch-type vacuum concentration, and the whole amount of unreacted acrylonitrile and a part of unreacted water were distilled off to obtain an aqueous acrylamide solution having a concentration of about 50% by weight. The aqueous acrylamide solution contained copper.
Copper removal treatment:
150 ml of strongly acidic cation exchange resin Levacit SP-112 (trade name, manufactured by Bayer) pretreated with dilute hydrochloric acid by a conventional method was packed in a glass column, and the acrylamide obtained by the above-described concentration treatment The aqueous solution was passed at 900 ml / hr. The obtained solution had a copper content of 0.01 ppm or less and a pH of 3.5 to 4.0.
pH adjustment:
During the copper removal treatment, caustic soda was continuously added to adjust the pH of the treatment solution to about 6.5.
[0070]
<Method for producing acrylamide polymer>
The aqueous acrylamide solution obtained by the above method was polymerized by the following method to obtain an acrylamide polymer.
[0071]
Water is added to the acrylamide aqueous solution to a concentration of 20% by weight, 500 g of this is put into a 1 l polyethylene container, and while maintaining at 18 ° C., the dissolved oxygen in the liquid is removed through nitrogen, and immediately, in a heat insulation block made of polystyrene foam. I put it in.
[0072]
Next, 200 × 10^-6mpm (molar ratio to acrylamide) of 4,4'-azobis (sodium 4-cyanovalerate), 200 x 10^-6mpm dimethylaminopropionitrile and 80 × 10^-6Mpm ammonium persulfate was each dissolved in a small amount of water and quickly injected into this sequence. Nitrogen gas was previously passed through these reagents, and before and after injection, a small amount of nitrogen gas was also passed through the polyethylene container to prevent contamination of oxygen gas. After injecting the reagent and after an induction period of several minutes, the temperature inside the polyethylene container was observed to rise, so the supply of nitrogen gas was stopped. After about 100 minutes, when the temperature reached the top of about 70 ° C., the polyethylene container was taken out of the heat insulating block, immersed in water at 97 ° C. for 2 hours, and then immersed in cold water to cool.
[0073]
The water-containing acrylamide polymer gel thus obtained is divided into small chunks, crushed with a meat grinder, dried with hot air at 100 ° C. for 2 hours, and pulverized with a high-speed rotary blade pulverizer to form a dry powdered acrylamide polymer. Obtained. Further, this was sieved to obtain a polymer sample for use in the subsequent tests. When the moisture content of the polymer sample was determined as a weight loss by drying with hot air overnight at 125 ° C., it was about 10% by weight for any polymer sample.
[0074]
<Testing method for acrylamide polymer>
The water solubility and standard viscosity of the polymer sample obtained by the above method were measured by the following method.
Water soluble:
Water solubility is obtained by putting 600 ml of water in a 1 l beaker, adding 0.66 g of polymer sample (0.6 g of pure content) while stirring with a stirring blade of a predetermined shape, and stirring at 400 rpm for 2 hours. The solution was filtered through a 150-mesh wire mesh, and water solubility was judged from the amount of insoluble matter and filterability. That is, ◎ is completely dissolved, ◯ is close to completely dissolved, there is an insoluble matter, △ is what can be filtered, △, the passage of the filtrate is slow, the insoluble matter is effectively filtered The thing which cannot be made was set as x.
If the molecular weight is about 15 million or more and the water solubility is ◯ or more, it is of a quality that can be used as a flocculant. Those having a water solubility of Δ can be used for papermaking chemicals, but are difficult to use as flocculants. Water-soluble x does not withstand use in most applications and has no commercial value.
Molecular weight:
The molecular weight was adjusted to several acrylamide polymer aqueous solutions with different concentrations using the filtrate obtained in the same manner as described above, sodium nitrate corresponding to 1M concentration was added thereto, and the intrinsic viscosity was measured using a capillary viscometer. Was calculated using the following formula.
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Intrinsic viscosity formula = 3.73 × 10^-Four× [weight average molecular weight]^0.66
The filtrate obtained by the above water solubility test is an aqueous polymer solution having a concentration of 0.1% by weight when water solubility is good. To this, sodium chloride corresponding to a concentration of 1M is added, and a BL type viscometer is used. Viscosity was measured using a BL adapter at 25 ° C. and a rotor rotation speed of 60 rpm (standard viscosity). Since the standard viscosity obtained by such a method is commonly used as a value correlated with the molecular weight, it was also used in this example. The evaluation results obtained by such a method are shown in Table 1. The water solubility of the obtained polymer was excellent, and the standard viscosity was 5.7 CPS (molecular weight of about 15.8 million).
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Comparative Example 1
The same procedure as in Example 1 was performed except that the purification of acrylonitrile was omitted. As a result, water solubility was x, viscosity was not measurable and had no commercial value.
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Through the application of the present invention to normal-quality acrylonitrile that could not be conventionally used as an acrylamide raw material through Example 1 and Comparative Example 1, it is possible to produce high-quality acrylamide that can withstand use as a flocculant. It was.
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Example 2
Acrylamide was produced in the same manner as in Example 1 using acrylonitrile (LOT-2), which is generally used as an acrylamide raw material and purified by distillation and reducing impurities to a higher degree than ordinary products. The results are shown in Table-1. The obtained polymer was water-soluble and had a very good quality with a standard viscosity of 5.9 CPS (molecular weight of about 16.7 million).
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Comparative Example 2
The same procedure as in Example 2 was performed except that the purification of acrylonitrile was omitted. The results are shown in Table-1. Water solubility was ◯, standard viscosity was 5.6 CPS (molecular weight about 15.3 million), and the minimum quality for the flocculant was maintained.
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Through Example 2 and Comparative Example 2, it was revealed that when the present invention was applied to acrylonitrile for acrylamide raw materials having a low impurity concentration, the quality was greatly improved.
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Example 3
When purifying acrylonitrile (LOT-1), the order of the purification tower was Diaion WA-20 in the first tower, Levatite S-100 in the second tower, and Calgon CPG in the third tower. The operation was performed. The results are shown in Table-2. Although the water solubility was Δ and the standard viscosity was 5.7 CPS, which had no commercial value (Comparative Example 1), the application of the present invention made it possible to withstand the use as a papermaking agent.
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Example 4
The same procedure as in Example 3 was performed except that the acrylonitrile used was changed to LOT-2 instead of LOT1-1. The results are shown in Table-2. Compared with Comparative Example 2, the water solubility was ◎ and the standard viscosity was 5.8 CPS (molecular weight of about 16.2 million).
Example 5
The same operation as in Example 1 was carried out except that the order of the purification tower was Revatit S-100 for the first tower, Calgon CPG for the second tower, and Diaion WA-20 for the third tower. The results are shown in Table-2. Although the water solubility was Δ and the standard viscosity was 5.7 CPS, which had no commercial value (Comparative Example 1), the application of the present invention made it possible to withstand the use as a papermaking agent.
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Example 6
The same procedure as in Example 5 was performed except that LOT-2 was used instead of LOT-. The results are shown in Table-2. The water solubility was 、, and the standard viscosity was 5.8 CPS.
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Example 7
The same procedure as in Example 1 was performed, except that activated carbon was not used in the order of the purification tower as Levacit S-100 in the first tower and Diaion WA-20 in the second tower. The results are shown in Table-2. The water solubility was ◯ and the standard viscosity was 5.7 CPS, which had no commercial value (Comparative Example 1), but the application of the present invention resulted in a quality that could be used as a flocculant.
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  Reference example8
  The same operation as in Example 1 was performed, except that the order of the purification tower was Calgon CPG in the first tower, Levacit S-100 in the second tower, and Diaion WA-20 in the third tower. The results are shown in Table 2. The water solubility was ◯ and the standard viscosity was 5.8 CPS, which had no commercial value (Comparative Example 1), but by applying the present invention, it became a quality that could be used as a flocculant.
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  Reference example9
  The same procedure as in Example 2 was performed, except that Diaion WA-20 was not used, with the order of the purification tower being Lebachit S-100 in the first tower and Calgon CPG in the second tower. The results are shown in Table 2. Compared with Comparative Example 2, the water solubility was ◎ and the standard viscosity was 5.8 CPS.
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Example 10
The same operation as in Example 7 was performed except that Levacit SP-112 was used for the first tower.
The results are shown in Table 2. The water solubility was ◯ and the standard viscosity was 5.7 CPS, which had no commercial value (Comparative Example 1), but by applying the present invention, it became a quality that could be used as a flocculant.
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Example 11
The same operation as in Example 1 was performed except that Levacit SP-112 was used for the first tower.
The results are shown in Table 2. Water solubility was ◎ and standard viscosity was 5.8 CPS, which had no commercial value (Comparative Example 1), but the application of the present invention resulted in a high-quality product that could withstand use as a flocculant. .
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Example 12
Instead of Diaion WA-20 (porous type), white bacon LHc (coconut shell base activated carbon) was used instead of Levacit OC1059 (gel type) and Calgon CPG (coal base activated carbon). The operation was performed. The results are shown in Table 2. The water solubility was ◎, and the standard viscosity was 5.8 CPS.
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Comparative Example 3
Acrylonitrile (LOT-1) was passed through S-100 only. Other than that was carried out in the same manner as in Example 1. As a result, the water solubility was x and no improvement effect was observed.
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Comparative Example 4
Low impurity acrylonitrile (LOT-2) was passed through S-100 only. Other than that was carried out in the same manner as in Example 1. As a result, the water solubility was Δ, and the quality deteriorated compared with Comparative Example 2 in which no purification treatment was performed.
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Comparative Examples 5-7
The same procedure as in Example 1 was conducted except that acrylonitrile (LOT-1) was passed through WA-20 alone (Comparative Example 5), CPG alone (Comparative Example 6), WA-20 and then CPG (Comparative Example 7). As a result, no improvement effect was observed.
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Comparative Examples 8-10
Acrylonitrile (LOT-1) is WA-20 and then S-100 (Comparative Example 8), WA-20 and then CPG is finally S-100 (Comparative Example 9), CPG and then WA-20 is finally S-100 (Comparative Example 10). ). Other than that was carried out in the same manner as in Example 1. As a result, no improvement effect was observed.
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[Table 1]

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[Table 2]

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【The invention's effect】
Acrylonitrile for the acrylamide raw material of catalytic hydration method cannot be obtained with high quality acrylamide unless there are few impurities. However, according to the method of the present invention, even if normal quality acrylonitrile is used, High-quality acrylamide can be obtained only by performing a simple column adsorption treatment before the summation reaction, and this acrylamide is particularly useful as a raw material for producing polyacrylamide for a flocculant. Further, when the present invention is applied to highly distilled and purified acrylonitrile generally used for the catalytic hydration method, higher quality acrylamide can be obtained.

Claims (5)

Acrylonitrile is contacted with a strongly acidic cation exchange resin and then a primary and / or at least contacted with the resin having a secondary amino group after passing through two steps, that hydrating reaction in the presence of a copper-based catalyst A method for producing acrylamide. The method for producing acrylamide according to claim 1, wherein the acrylonitrile is produced by an ammoxidation method of propylene. The method for producing acrylamide according to claim 1 or 2, wherein acrylonitrile is contacted with a resin having a primary and / or secondary amino group, and further contacted with activated carbon. Acrylamide is contacted with a resin having primary and / or secondary amino groups, then contacted with a strongly acidic cation exchange resin, then contacted with activated carbon, and then hydrated in the presence of a copper-based catalyst. Manufacturing method. Acrylonitrile is contacted with a strongly acidic cation exchange resin, then contacted with activated carbon, further contacted with a resin having primary and / or secondary amino groups, and then hydrated in the presence of a copper-based catalyst. A method for producing acrylamide.