JPH02500188A - Method for recovering and purifying unreacted acrylonitrile from waste streams in the production of 2-acrylamido-2-methylpropanesulfonic acid - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] In the production of 2-acrylamido-2-methylpropanesulfonic acid, waste streams or Method for recovering and purifying unreacted acrylonitrile from School plate ■ Toyotaka There are many ways to produce acrylonitrile. This compound is available It has become one of the most important and promising organic chemical intermediates. It is extensive surrounding products (e.g.

Particularly desirable when producing plastics, synthetic rubber, synthetic fibers, soil additives, etc. It is a new intermediate. For many uses.

Acrylonitrile must be of high purity and for this reason acrylonitrile Commercial manufacturing of rills must meet strict specifications.

“Each commercial method used to prepare acrylonitrile requires Impurities and by-products are generated. Each step has its own purification problems (See U.S. Pat. No. 3,459,639).

Different methods of producing acrylonitrile form different by-product impurities Different purification methods are required in that they are purified. Therefore, this impurity is removed However, different methods may be required to purify acrylonitrile.

Due to these limitations, none of the existing acrylonitrile purification methods Universally interchangeable with respect to usefulness in purifying acrylonitrile-containing compositions As shown in U.S. Pat. No. 4,404,064, which is unlikely to be A very good and commercially practiced method for producing phosphoric unsaturated nitriles The method is a catalytic reaction of ammonia and olefins. For example, acrylonitrile and methacrylonitrile, respectively, in the presence of ammonia. and isobutylene by catalytic oxidation in the gas phase.

These methods produce significant amounts of impurities. Ammonia and propylene By the production of acrylonitrile from

Acetonitrile, propionitrile, acetone, etc. are formed in significant amounts . By removing impurities from these by-products.

is necessary.

U.S. Pat. No. 3,459.639 to Borre et al. describes acrylonitrile, A complex mixture of acetonitrile and other substances (this.

Acrolein or propylene is catalytically acrylated in the presence of ammonia or oxygen. Disclosed is a method for purifying lonitrile (formed by vapor phase conversion to lonitrile). a Separating acrylonitrile from setonitrile is performed at a pH of at least 5 (preferably Alternatively, in steps 5 to 7), introduce an alkalizing agent into the distilled mixture and perform extractive distillation. be exposed.

Kuma's U.S. Pat. More specifically, olefinic nitriles (e.g. dimethacrylonitrile) and acrylonitrile).

here.

This olefinic nitrile is a combination of the olefinic nitrile and the following substances. Produced by ammoxidation of isobutylene and propylene from a mixture. Ni-heptonitrile, hydrogen cyanide, propionitrile, butyronitrile, metal Tacrolein, acrolein, acetone, acetaldehyde, etc.

The pillars point out the following: Olefins (e.g.

isobutylene or propylene) is exposed to air at high temperature in the presence of an ammoxidation catalyst. phase, when subjected to reaction with ammonia or molecular oxygen, the corresponding olefinic Nitriles (e.g.

Methacrylonitrile and acrylonitrile) are by-products of the ammoxidation reaction (this includes acetonitrile and hydrogen cyanide.

Propionitrile, butyronitrile, methacrolein, acrolein, acetone , acetaldehyde), mixtures of the desired olefinic nitriles, and and some of these by-products that appear in the eluate of the ammoxidation reactor. Generate according to quantity.

According to Huang's method, the products of the ammoxidation reaction are absorbed into water in the first step. 1 will be recovered by doing so. During this stage, some heavy or high-boiling organic compounds are formed by polymerization, condensation, etc. of some light organic products. Therefore.

This method of polishing removes heavy organic compounds as well as by-products formed in the ammoxidation reaction. This is an improved method for separating olefinic nitriles from other substances.

Also the method disclosed in U.S. Pat.

Concerning the purification of acrylonitrile. However, this method is particularly The acrylic acid produced by the catalytic gas phase reaction of ink with ammonia and molecular oxygen. Applicable to purification of lonitrile. In such reactions, crude acrylonitrile (1) Usually, preferably after neutralizing all unreacted ammonia.

By contacting the gaseous reaction products with water, a dilute aqueous solution (also known as 2) containing varying amounts of acrolein and hydrogen cyanide. Ru.

Once the purified form of acrylonitrile is obtained.

This acrylonitrile monomer can be used to produce various products as shown above. The present invention uses excess acrylonitrile to react with other reactants. to produce acrylonitrile from impurities. related. More specifically, an excess of acrylonitrile (which is itself an intermediate) ) is the product produced using .

2-acrylamido-2-methylpropanesulfonic acid (this is.

AMPS” (sold by Lubrizol Corporation). . During the production of ASPS, a stoichiometric excess of acrylonitrile is used. Ru. Therefore, even after the desired product has been formed and separated, various amounts of acrylonitrile The rill remains unreacted and is present along with other impurities. Many of these impurities is extremely reactive with acrylonitrile.

Causes polymerization. This polymerization more specifically refers to acrylonitrile monomer monomers. undesirable copolymerization of the monomer units of the monomers and the impurities present. impurities The unreacted acrylonitrile present along with the 2-acrylamide-2-methyl In the synthesis of lepropane sulfonic acid, if it is simply recycled.

The resulting product has the desired purity and does not meet the desired specifications. difference Furthermore, such impure acrylonitrile initiates unwanted polymerization. death Perhaps all the reaction products generated from such impure acrylonitrile (e.g. Does not have the desired specifications. 9. For example, there are no water-insoluble polymer particles, and the purity etc. are lacking. Therefore, the present invention is as follows.

We are developing an improved method to purify such unreacted acrylonitrile. Ru.

As pointed out above, how to purify acrylonitrile.

Varies based on factors such as impurities present with acrylonitrile. Book The invention differs from the method discussed above in the following ways: 2. The method discussed above generally , related to the purification of waste from acrylonitrile products. Against this 2 The process of the present invention uses an excess of acrylonitrile to produce a product ( For example, during the production of 2-acrylamido-2-methylpropanesulfonic acid), 9 The invention relates to the purification of unreacted acrylonitrile from the waste stream produced. paraphrase In other words, the present invention provides that this acrylonitrile is used as a reactant to produce other products. The purpose is to purify unreacted acrylonitrile when used as ing. Prior art techniques, such as those discussed above, generally involve producing acrylonitrile. For the purpose of purifying acrylonitrile from unreacted reactants used in There is. These unreacted reactants formed during the production of acrylonitrile are generally , unreacted product obtained from the production of 2-acrylamido-2-methylpropanesulfonic acid It is less reactive than the impurities present with the corresponding acrylonitrile. This impurity The higher the reactivity, the greater the need to remove such impurities.

Different impurities are obtained when different reactants are used.

Therefore, both methods purify acrylonitrile from all types of impurities. are not necessarily interchangeably useful in terms of doing so.

Lord Rio! And To synthesize 2-acrylamido-2-methylpropanesulfonic acid, an excess amount of of acrylonitrile is combined with sulfuric acid and isobutyne. the reaction obtained The product contains significant amounts of unreacted acrylonitrile and other by-products. .

Includes 2-acrylamido-2-methylpropanesulfonic acid.

This 2-acrylamido-2-methylpropanesulfonic acid is one of the residual acids. Acrylonite present along with impurities of , acrylamide, and other by-products It can be separated leaving a rill. This impurity is approximately 1 to 2 weight by weight based on the weight of one composition. Present in an amount of %.

These acid impurities include sulfuric acid and isobutylene monosulfonic acid.

Isobutylene disulfonic acid and a small amount of 2-acrylamido-2-methylpropane sulfonic acid, t-butylacrylamide and acrylamide. 1 Acrylonitrile containing ~2% impurities (e.g. residual acid) is For the production of acrylamide-2-methylpropanesulfonic acid, it should not be reused. , the resulting product (i.e., 2-acrylamido-2-methylpropanesulfate) (phonic acid) has 9 different undesirable properties. For example, the resulting product Undesirable compounds formed by polymerization of acrylonitrile monomer and impurity monomers Contains high polymeric substances. Therefore, this acrylonitrile must be purified before reuse. It is desirable to The present invention provides such a purification method and the products obtained therefrom. Aiming at things.

Unreacted acrylonitrile containing impurities (e.g. residual acid) is first removed.

It is neutralized by adding a base such as: aOH, NH3, Ca2 or lime (i.e. calcium oxide) and / or a mixture thereof. This base reacts with the impurity acid present and produces 9 Forms various salts (e.g. calcium salts). Ammonia is used under anhydrous conditions. I can stay. But 2 limes.

A more preferred base is used in the presence of a catalytic amount of water.

The inventors have found that both lime and water are particularly good for the neutralization associated with the present invention. I found that it works well. The amount of lime added will reduce the amount of impure material to be treated. Depends on the acid neutralization number of acrylonitrile. Neutral salts that form as solids are Accelerated by sedimentation or mechanically, with sedimentation or all unreacted lime The two can be separated using standard means (eg, centrifugation or filtration).

At this point, the acrylonitrile product is neutralized and purified to some extent. It will be done. However, it still contains impurities. This impurity may cause other substances (e.g.

2-acrylamido-2-methylpropanesulfonic acid). Nitrile can no longer be used. Therefore, after removing the neutral salt, this impure acrylic Rilonitrile is fed to the heat exchanger. This heat exchanger operates under vacuum at relatively low temperatures. (i.e. below 172°F, preferably in the range of 110°F to 140°F) Be manipulated. As a result, all substances present are heated to the desired range of temperatures. Ru.

Substances (including liquids and vapors) heated in a heat exchanger.

It is then transferred to the lower region of the distillation column. The column has a bottom opening, multiple distillation It consists of a.

This column is maintained under vacuum. Most of the heated material entering the distillation column is , fall to the bottom of the tower. In contrast, a small amount of purified acrylonitrile is stored at the top of the column. from there due to the pressure difference.

The heated material that has fallen to the bottom of the distillation column is (according to the first embodiment) returned to the heat exchanger. It will be done. According to a second embodiment, the material is divided into two parts. the lord The essential part is returned to the heat exchanger. According to the second embodiment, it falls to the bottom of the distillation column. A small portion of the collected material is transferred to a thin film evaporator. This distiller melts substances under vacuum. temperature above the point and below about 172°F, preferably from about 120°F to about The temperature is maintained in the range of 145°F. In a thin film evaporator, a relatively large amount of Impure waste containing residual acid falls to the bottom of the evaporator. Partially refined ac The rylonitrile product is removed from the top of this evaporator and transferred to a distillation column.

This partially purified substance.

It is preferably transferred to the following part of the distillation column: This part is where the material is transferred from the heat exchanger to the column. Preferably above where it enters, but below the tray of the tower.

This partially purified acrylonitrile product (which is a thin film similar to the second implementation B) 9) transferred from the evaporator to the distillation column) is then transferred while a vacuum is maintained in the distillation column. , further subjected to distillation. The highly purified acrylonitrile product is and according to the second embodiment 9 is removed from the upper opening of the distillation column. distillation column The impurities inside continue to fall to the bottom of the tower.

be removed. According to the first embodiment, most of the impurities are recycled to the heat exchanger. It is circulated. According to a second embodiment, this is divided into two parts. the The main part of this method is the heat exchanger, where the purified acrylonitrile product is transferred to the top of the distillation column. This is done continuously as the material is removed.

Impurities contained in the purified acrylonitrile product removed from the upper section of the distillation column The amount of substances such as residual acid and acrylamide is negligible. Therefore, this The purified acrylonitrile itself has a desired average molecular weight, and excellent storage stability. have sex. Furthermore, this purified acrylonitrile is used in the production of 2 other substances. can be used. For example, this substance.

2-acrylamido-2-methylpropanesulfonic acid (also of high purity) recycled for use in the production of This high purity makes acrylic It is obtained by removing impurities that are particularly reactive with nitriles, and is particularly important. Ru.

These reactive impurities react with acrylonitrile.

Forms water-insoluble polymers. This polymer is 2-acrylamido-2-methyl Clouding an aqueous solution prepared by incorporating propane sulfonic acid and water .

The main object of the present invention is to solve the following problems: Provides a method for purifying pure acrylonitrile waste streams: This reaction produces The reactants are reacted with excess acrylonitrile to obtain

A feature of the present invention is that residual acrylonitrile existing together with such unreacted acrylonitrile is Neutralizing the acid by treating it with a base (e.g. lime or ammonia) and removing the formed salt.

Another object of the present invention is to provide an economical and efficient method for producing acrylonitrile using vacuum and low temperatures. An object of the present invention is to provide a method for purifying tolyl.

An important feature of the invention is that while avoiding polymerization of acrylonitrile during purification, It is possible to purify such waste stream type impure acrylonitrile.

An advantage of the present invention is that acrylonitrile is environmentally acceptable and environmentally approved. The purpose of this invention is to provide a method for refining olefins.

Another advantage of the present invention is that 9 polymerization is significantly reduced and the salts formed are removed early in the process. Acrylonitrile concentrate with reduced sediment build-up in the equipment in terms of The purpose is to provide a manufacturing method.

An important feature of the present invention is that 2-acrylamido-2-methylpropanesulfonic acid is The unreacted acrylonitrile used in the production is converted into the following purified acrylonitrile. The objective is to provide a method that can be reused to produce products: The resulting product ζ5 may have desired properties (e.g. storage stability and water insolubility). (This is the result of the reaction of acrylonitrile with various reactive impurities.) 2-acrylamide-2-methylene (formed by) There is lupropanesulfonic acid.

Yet another object of the invention is to obtain purified acrylonitrile, such as having the desired properties as such. The object of the present invention is to provide a method for producing trills. This desired property includes 9 e.g. The absence of high molecular weight polymers that are insoluble in the One example is the storage stability.

Another feature of the invention is a purified acrylonitrile having desired properties and 2-acrylamido-2-methylpropanesulfonic acid (this is a clear aqueous solution) The object of the present invention is to provide purified acrylonitrile capable of forming

These and other objects, advantages and features of the present invention.

It will be apparent to those skilled in the art upon reading the present disclosure.

Brief description of the drawing Figure 1 is a blueprint showing an overview of a purification system used in a preferred embodiment of the present invention. be.

Detailed description of the invention The chemical product 2-acrylamido-2-methylpropanesulfonic acid (lubrizo) Manufactured as a product under the trademark "AMPS" by Paul Corporation), it is industrially Used for a variety of different purposes. This 2-acrylamido-2-methylpropane Not only the sulfonic acid product, but also other products It can be produced by reacting an acid and isobutylene. Economic factors 2-acrylamido-2-methylpropyl It is desirable to reuse unreacted acrylonitrile to produce sulfonic acid. Yes. However, unreacted acrylonitrile may be contaminated with other impurities (e.g. (lylamide and residual acids); and this itself is not storage stable. Produces high quality 2-acrylamido-2-methylpropanesulfonic acid that is low in If the acrylonitrile is not purified to the required degree, it cannot be reused. react with impurities present to form compounds that are insoluble in water. High quality 2-A to produce a crylamide-2-methylpropanesulfonic acid product, and 2. In order to obtain an effective use of acrylonitrile, we.

The unreacted impure acrylonitrile waste stream (this is the 2-acrylamide-2-methane We have discovered a method for purifying methylpropane sulfonic acid (produced during the production of methylpropane sulfonic acid).

When producing 2-acrylamido-2-methylpropanesulfonic acid, an excess amount of When acrylonitrile is used, the desired 2-acrylamide-2 formed - The methylpropanesulfonic acid product contains impurities that have not been completely removed, e.g. , sulfuric acid.

Isobutylene monosulfonic acid, isobutylene disulfonic acid.

acrylamide, and a small amount of 2-acrylamido-2-methylpropane sulfonate. (acrylonitrile) is removed leaving behind the acrylonitrile present with 1-2% by weight of phosphoric acid). obtain. This acrylonitrile is the impure waste stream acrylonitrile mentioned above. Ru.

In order to effectively purify unreacted acrylonitrile, the present inventors discovered that 2-acrylonitrile Nitrile with a strong base (e.g. 3 lime (i.e. calcium oxide), NaOH , NH3, or Ca(OH)z). We have found that it is first desirable to chemically treat the material. lime (i.e. .

When neutralizing with calcium oxide), the amount of lime added is 5. Depends on the acid neutralization number of rylonitrile. per acid equivalent of impure acrylonitrile, Although some effects can be obtained using 0.5 to 1.5 equivalents of lime, acrylonito It is generally desirable to use less than 1.0 equivalents of lime per acid equivalent of rill. do not have. Additionally, the inventors have determined that, per acid equivalent of impure acrylonitrile, approximately 1.1 An equivalent amount of lime can be used.

We have found that it is particularly preferable in the following respects: Use less than 1.0 equivalents of lime. and all the acids present are not completely neutralized.

And the use of more than 1.1 equivalents of lime is not economical.

When using lime for neutralization, water must be present. acrylonitrile The solubility of water in the solution is only about 3.2%. Therefore, water below 3.2% can be used. We have found that using water above about 2.7% It was discovered that um salt becomes viscous and difficult to handle. effective neutralization stage It has also been found that at least about 0.5% water should be present to provide It is. Therefore, water.

Preferably an amount of about 1.0 to 2.5%, more preferably about 1.5% to about 2.0%. exists in

Anhydrous ammonia may be used, but lime is mixed with a catalytic amount of water, as mentioned above. They are not effective unless used in combination. Unreacted acrylic treated with base The lonitrile is neutralized and a salt is formed. For example, in the presence of a catalytic amount of water.

By treatment with lime, calcium salts are formed. how many salts are formed The lime precipitates quickly and can be easily removed along with unreacted lime. precipitates quickly All salts that are not present are removed by precipitation or by mechanically promoting this base-treated material. removed by subjecting it to separated means (e.g. centrifugation and/or filtration) can be done.

After applying one or more of the mechanical separation means mentioned above, the salt or Most of the lime and unreacted lime are removed, and the acrylonitrile is purified to a certain extent. be done. However, at this point, acrylonitrile is still around 1.5% or less impurities. This impurity can be removed by other physical means (i.e. 6 various distillations).

Referring to the drawing, base-treated acrylonitrile (which precipitates and/or or with salts removed by various mechanical means) is passed through line 1 for heat exchange. is supplied to vessel 2.

Feed rates may vary depending on the particular equipment and implementation used. Main departure The authors have found that a feed rate of about 40 to 100 gal/win is useful, and about 70 gal/win. It has been found that l/min is preferable.

This heat exchanger 2 is preferably a single bath shell and tubular heat exchanger. Ru. The inventors constructed a 316 stainless steel panel approximately 750 square feet in size. The use of shell and tubular heat exchangers has been found to be particularly useful. I started it. Impure acrylonitrile in heat exchanger 2 is removed from the outer shell of heat exchanger 2. 3 to the heating fluid (which is preferably in the form of saturated steam, under reduced pressure ’F to approximately 215″F) is continuously circulated. By flying about 320 meters, the temperature below 172 degrees Fahrenheit, preferably about maintained at a temperature of 110"F to about 140F, more preferably about 120F .

At atmospheric pressure, the temperature of acrylonitrile is kept below 172°F to prevent monopolymerization. Must drip. We maintain the pressure at a reduced pressure of approximately 320a+mHg. However, we have found that it is desirable to keep the temperature in the range of 110@F to about 140'F. I put it out.

Steam temperature and pressure increase as the internal components of the heat exchanger collide. death However, due to this temperature level, acrylonitrile undergoes significant polymerization. I never received it.

Fouling of components in contact with acrylonitrile is greatly reduced.

Avoid polymerization and deposition (which accumulates on internal surfaces in contact with acrylonitrile). The reduction in is one substantial advantage of the present invention.

This heated fluid is introduced around the shell 3 by an input line 4 . Here, The hot fluid circulates around the shell 3 9 and then via the discharge line 5 to the outlet. this This keeps the acrylonitrile at a relatively constant temperature. many different factors is correlated and determined by whether acrylonitrile reacts with impurities. Ru. As the temperature, pressure, amount of impurities, and degree of reactivity of the impurities increase , undesirable polymers, and impurities themselves and/or acrylonitrile. The possibility of forming a copolymer between

This acrylonitrile contains both liquid and vapor substances, along with impurities. It becomes a thermofluid substance. Some impurities are removed from the vapor part of this substance. Ru. From heat exchanger 2, the liquid/vapor material is transferred to line 6 (here below 172°F). temperature, preferably in the range of about 106°F to about 126°F, more preferably (at a temperature of approximately 116°F) to the lower region of distillation column 7. It's fried. The column 7 is constituted by a cylinder wall section. the inner part has a bottom opening, such as a plurality of distillation trays 8.8', 8'', 8''' extending out from it. 9. and an upper opening 10. This tower 7 depends on the size, shape, and size of the tray. and the number can be changed. However, the two inventors used a 316 stainless steel tower (which It has 6 trays.

It is 19 feet 1-8 inches tall and 6 feet in diameter).

It has been found that it works particularly well. These trays are located about 2 feet inside. place This column 7 may be maintained under vacuum. However, the inside and outside of this tower are A pressure difference is maintained between the opening 11 and the opening 11. That is, the internal pressure of column 7 teeth.

higher than the pressure at outlet 11. As a result, pure vaporized gas (acrylonitrile) ) flows freely from column 7 via outlet 10 into line 11. The inventors have determined that approximately At 320 mmHg, the internal temperature of the column is between about 110°F and about 140°F, more preferably This process works particularly well if the temperature is maintained at 120°F. I found out. This temperature and pressure range is preferred for a number of reasons. deer However, this temperature is below 172°F and the melting of acrylonitrile at atmospheric pressure. It should be noted that it is about a point.

Of the liquid/vapor material added to column 7 via line 6.

Almost all of the liquid part falls to the bottom of the column 7 and is discharged via the opening 9. Pure Pure acrylonitrile has a low boiling point.

It rises to the top of the column and is removed through an opening 10 leading to line 11. impurities and High boiling point acrylonitrile is also present in

It falls to the bottom of column 7 and is removed via line 12 through opening 9.

According to a first embodiment of the invention, almost all of the removal via line 12 The material is pumped into line 13, enters heat exchanger 3 and is therefore recycled. It will be done. A small amount of impure bottoms is removed from the bottom of column 7.

According to a second embodiment of the invention, the material removed via line 12 is divided Ru. Most of the material is in line 13 (this line 13 is directly connected to heat exchanger 2). (can be connected or feedbanked via supply line 1) Recirculated to heat exchanger 2. Then, a small portion of the material from the line 2 It is led to a thin film evaporator 15 through a tube 14. Also in the second embodiment. bottom of tower 7 The impure bottom is removed from the bottom of the thin film evaporator 15 via line 18 as well as from the bottom of the thin film evaporator 15. It includes leaving. The zero process of the present invention is economically advantageous in the following respects: heat without evaporating most of the liquid feed entering exchanger 3.

It becomes possible to economically recover a large amount of acrylonitrile. This process also . By keeping the temperature low and reducing the portion of the feed that has to be evaporated, greatly reduces the formation of polymeric substances at the site.

The evaporator 15 is operated at a temperature below 172°F, preferably at about 320 ml II Hg. more preferably in the range of about 120°F to about 145°F, more preferably about 120°F. maintained at temperature. This temperature is under atmospheric pressure.

The melting point of the related material (i.e. impurity acrylonitrile) is approximately 17 It is about 2°F. The inventors constructed a 53.8 square foot 316 stainless steel We have found that steel evaporators work particularly well. This evaporator is along the outer surface with fluid entering via in 16 and exiting via discharge line 17. This temperature is maintained by continuously circulating the fluid. line 16 The heating fluid entering and exiting via line 17 preferably enters the evaporator. rather, it is simply supplied to control the temperature within the evaporator. The inside of the evaporator is under reduced pressure will be maintained. High-boiling substances containing large amounts of impurities fall to the bottom of the evaporator7. It is removed via line 18 for further processing and/or removal. Partially The purified low boiling point acrylonitrile is connected to the upper opening 20 of the evaporator 15. It is taken out through a line 19. Partially purified acrylonitrile is in 19 and then returned to distillation column 7 and enters this column 7 at point 21. Ru. This point 21 is used for towers where the liquid/vapor material enters the tower from line 6. It is preferably above the lower region, but may be below or at the same height. Rai Many of the partially purified acrylonitrile products entering from boiling point and is therefore withdrawn from the top of the distillation column and discharged via line 11 . Purified product drawn out from the top of the distillation column 7 via the opening 10 and line 11 The quality is highly refined. This purified material has improved and unexpected superior properties (for example, molecular weight and storage stability of 9). This substance is 2-acrylamide- 2-Methylpropanesulfonic acid, which also has the desired average molecular weight and is modified have improved and unexpected storage stability).

The present invention is directed to what is considered to be the most preferred embodiment.

Disclosed and described herein. However, after reading this specification, a person skilled in the art will be able to It is contemplated that various modifications may be made and that such modifications may be encompassed by the present invention. I would like to point out that

international search report international search report

Claims (1)

[Claims] 1. Compound produced by reacting reactants with excess acrylonitrile A method for purifying unreacted and impure acrylonitrile used in the synthesis of The purification method includes the following steps: Treating the impure acrylonitrile with a base to remove the salts formed Obtaining acrylonitrile; the treated acrylonitrile is heated in a heat exchanger. , above the melting point of the treated acrylonitrile, but as low as about 172°F. heating under vacuum to a lower temperature and supplying a heated fluid substance; placing the fluid material in a distillation column maintained under vacuum; and Removing purified acrylonitrile with a low boiling point from the column. 2. Compound produced by reacting reactants with excess acrylonitrile A method for purifying unreacted and impure acrylonitrile used in the synthesis of The purification method includes the following steps: Impure acrylonitrile is treated with lime in the presence of a catalytic amount of water and shaped The neutral calcium salt produced is removed to provide the treated acrylonitrile. The treated acrylonitrile is transferred to the treated acrylonitrile in a heat exchanger. Heat to a temperature above the melting point of lonitrile, but below about 172°F. , supplying a heated fluid material; supplying the fluid material with the treated acrylonitrile; in a distillation column maintained at a temperature above the melting point of but below about 172°F. to be placed in; and To extract purified acrylonitrile with a low boiling point. 3. Used in the synthesis of 2-acrylamido-2-methylpropanesulfonic acid A method for purifying unreacted impure acrylonitrile, the method comprising: The purification method includes the following steps: Treating the impure acrylonitrile with a base to remove the salts formed supplying acrylonitrile; transferring the treated acrylonitrile to a heat exchanger; at a temperature higher than the melting point of the treated acrylonitrile, but about 172° heating under vacuum and supplying a heated fluid substance to a temperature below F; placing the fluid material in a distillation column maintained under vacuum; and Removing low boiling point fluid from the column. 4. Used in the synthesis of 2-acrylamido-2-methylpropanesulfonic acid A method for purifying unreacted impure acrylonitrile, the method comprising: The purification method includes the following steps: Treating the impure acrylonitrile with a base to remove the salts formed supplying acrylonitrile; transferring the treated acrylonitrile to a heat exchanger; heated under vacuum to a temperature in the range of about 110°F to about 140°F, and then supplying body substances; placing the fluid material in a distillation column maintained under vacuum; where the fluid material is In the lower region of the distillation column, the distillation column contains a plurality of distillation trays, purified An upper opening from which the acrylonitrile is drawn, and a lower opening from which the fluid substance is drawn. consisting of an opening; and While drawing out purified acrylonitrile from the upper opening, the lower opening removing high boiling point fluid from the mouth and returning the removed fluid material to the heat exchanger thing. 5. A method according to claim 1, which further comprises the following steps: Contains: placing a small portion of said removed fluid material in a thin film evaporator; The small portion of the evaporated fluid material enters the evaporator in the lower region of the evaporator and The vessel is maintained under vacuum at a temperature in the range of about 120°F to about 145°F; removing high boiling point impure fluid substances from the lower opening of the evaporator; removing a partially purified fluid material of low boiling point from the upper opening of the evaporator; and returning the partially purified fluid material to the upper region of the column; , fluid material enters the column from the heat exchanger; and While purified acrylonitrile is taken out and recovered from the column, it is vaporized in the column. To burn a knot. 6. The method according to any one of claims 1, 3, 4, or 5, The base is lime in the presence of a catalytic amount of water, and the salt removed is a calcium salt. It is. 7. The method according to any one of claims 1, 3, 4, or 5, The base is ammonia and the salt removed is an ammonium salt. 8. The method according to claim 7, wherein the ammonium salt is centrifuged. removed. 9. The method according to claim 7, wherein the ammonium salt is obtained by filtration. removed. 10. The method according to claim 7, wherein the ammonium salt is produced by precipitation. removed. 11. A method according to any one of claims 1, 2, 3, 4 or 5, , said salt is subjected to mechanical means selected from the group consisting of centrifugation, filtration and sedimentation. It is removed. 12. 4. The method according to claim 4, wherein the base is lime in water. , the lime is present in an amount of about 0.5 to about 0.5 equivalents per acid equivalent in the impure acrylonitrile. Present in an amount of 1.5 equivalents. 13. 13. The method according to claim 12, wherein the water is the acrylonitrile is present in an amount of about 1.0% to about 2.5% by weight, based on the weight of the sample. 14. 14. The method of claim 13, wherein the lime is about and the water is present in an amount of 1.1 equivalents, based on the weight of the acrylonitrile, Present in an amount of about 1.5% to about 2.0% by weight.