JPH0457663B2 - - Google Patents

Description

Claim 1 An amide of the formula RCONH ₂ (in the formula, R is an ethylenically unsaturated hydrocarbon group having 2 to 10 carbon atoms) is mixed with water of a solid catalyst for hydrolysis reaction and an oxidized catalytic compound on the catalyst. A process for producing a nitrile of the corresponding formula RCN by hydrolysis in a reaction mixture comprising an oxidizing agent and a polymerization inhibitor that enhance the activity of the catalyst by forming active sites in the reaction mixture, the method comprising: A method characterized in that the formation of by-products is reduced by adding reagents that degrade some, but not all, of the oxidized sites. 2. The method of claim 1, wherein said reagent is selected from acids and reducing agents, including non-interfering salts that are non-oxidizing to the oxidizing agent. 3 An amide of formula RCONH ₂ (wherein R is an ethylenically unsaturated hydrocarbon group having 2 to 10 carbon atoms) is mixed with a solid catalyst for hydrolysis reaction, water, and an oxidized catalytically active substance on the catalyst. A process for producing a nitrile of the corresponding formula RCN by hydrolysis in a reaction mixture comprising an oxidizing agent and a polymerization inhibitor that enhance the activity of the catalyst by forming sites, the method comprising: selected from acids that are non-oxidizing to the oxidizing agent, non-interfering salts thereof, and reducing agents, sufficient to suppress by-product formation but not sufficient to substantially reduce amide formation; A method characterized in that the formation of by-products is reduced by adding sufficient amounts of reagents. 4. Water, catalyst, oxidant, reagent, and nitrile are substantially continuously fed into the reaction vessel, amide is substantially continuously removed from the vessel, the amount of catalyst in the vessel is greatly increased during the process, and then Claim 3 carried out by discharging the catalyst from the container
the method of. 5. The method of claim 3, wherein said reagent is added substantially continuously or when by-products are formed above a predetermined level. 6. The catalyst is a substantially black copper catalyst, preferably Raney copper, the inhibitor contains dissolved copper, and the amount of reagent is insufficient to convert the black copper to pink, salmon pink or red copper. The method according to claim 3. 7. The method of claim 3, wherein the nitrile is acrylonitrile or methacrylonitrile and the amide is acrylamide or methacrylamide. 8. The method of claim 3, wherein the hydrolysis is carried out at a temperature exceeding 100°C. 9. The method of claim 3, wherein the oxidizing agent is a nitrate. 10 Claim 3 wherein the reagent is selected from weak reducing agents, non-polymerizable acidic buffers and non-interfering salts thereof.
the method of. 11 The reagent has a pKal of 2 to 7, preferably 4 to 6.
11. The method according to claim 10, which is a saturated aliphatic organic acid having the following: or a salt thereof with copper or aluminum. 12. The method of claim 10, wherein the reagent is acetic acid or copper acetate. 13. The method of claim 3, wherein the reagent is added only for a short time and only when more by-products are formed than desired, and the reagent is an acid or its salt with a weak base that is non-oxidizing to the oxidizing agent. . 14. The method of claim 3, wherein the catalyst introduced into the reaction mixture is a substantially black copper catalyst washed with an aqueous solution of an acidic buffer that is a non-polymerizable organic acid or a salt thereof. 15 The catalyst to be washed is fresh Raney copper, a catalyst used as a catalyst in a process for the hydrolysis of nitriles to amides in the presence of water and a catalyst and has become non-selective, and mixtures of said fresh and spent catalysts. 15. The method of claim 14 selected from. 16 An amide of the formula RCONH ₂ (wherein R is an ethylenically unsaturated hydrocarbon group having 2 to 10 carbon atoms),
A process for preparing a Raney catalyst, preferably a nitrile of the formula RCN, by hydrolysis in a reaction mixture consisting of a Raney copper catalyst and water, the process comprising: prior to introducing the Raney catalyst into the reaction mixture; A method characterized by washing with an aqueous solution of an acidic buffer. 17 The buffering agent is 2 to 7, preferably 4 to 6
The method according to claim 3 or claim 16, wherein the saturated fatty acid or its salt has a pKal. 18. The method of claim 14 or claim 16, wherein the catalyst is washed with acetic acid or an aqueous solution of copper acetate. Description US Application No. 28 October 1982, corresponding to EP78178
This is a continuation-in-part of application no. US SN437385. It is known to hydrolyze the corresponding nitriles RCN with water in the presence of a solid catalyst to produce amides of the formula RCONH ₂ , where R is a hydrocarbon radical having 1 to 10 carbon atoms. A wide variety of catalysts have been proposed and discussed, for example, in US Pat. No. 3,997,606. However, more recent literature has focused on the use of copper, usually Raney copper, as a catalyst. Throughout the literature, emphasis is placed on providing catalysts with maximum activity for high conversion of nitriles to amides. The literature also describes the desirability of including activators to improve the activity of the catalyst. For example, U.S. Pat. No. 3,381,034 uses a mixture of zero-valent, monovalent and divalent copper;
It is described that it is introduced as cupric sulfate or cupric cyanide, and two examples using acetic acid and cuprous chloride are shown. US Pat. No. 3,911,009 describes the use of Raney or other suitable copper in combination with a solubility promoter selected from copper sulfate, copper nitrate, copper chloride and copper salts of lower fatty acids. It has been found that copper nitrate is a very active activator and copper acetate is less effective. European Patent No. 78178 describes how the activity of Raney copper can be improved by partial oxidation by contacting it with oxygen, peroxides, iodates, chlorates, bromates or nitrates before introduction into the reactor. It is also described that the hydrolysis of the nitrile is preferably carried out in the presence of copper nitrate or other suitable promoters which increase the activity. Various other methods have also been described. For example, European Patent No. 37178 states that the activity of the copper catalyst is
It is stated that it is maintained by electrolysis under conditions with 0.75 to 12.5 monolayers of ionic copper on the surface of the catalyst. The specification indicates that increasing or decreasing the amount of ionic copper reduces the activity of the catalyst. It has been confirmed in the literature that catalyst activity is lost during long-term use and that this deactivation is due to oxidation. See, eg, US Pat. No. 3,886,213. It has also been confirmed that it is possible to regenerate deactivated catalysts. For example, US Pat. No. 3,642,894 describes that a deactivated catalyst is oxidized and then reduced. It has been considered possible to carry out the hydrolysis in the presence of a deactivated catalyst, provided that a new active catalyst also exists. In this case, fresh active Raney or other copper catalyst is introduced into the reactor continuously or intermittently over an extended period of time, and water, acrylonitrile and any dissolved promoter (e.g. copper nitrate) are continuously introduced into the reactor. to be introduced. Acrylamide is removed continuously. All or part of the catalyst remains in the reactor. Typically, the amount of spent or “stale” catalyst in the reactor becomes large enough to stop the reaction;
The spent catalyst is discharged from the reactor and the process continues until it is necessary to restart the process. Many hydrolysis methods are exemplified in the literature to be carried out at temperatures of eg 70°C, but of course hydrolysis proceeds faster at higher temperatures.
US3911009 proposes temperatures up to 150°C,
US3381034 exemplifies a temperature of 125°C. Although the known methods can perform the conversion well, they are encountered with the problem that they tend to form a large amount of by-products during long-term operation. For example, when acrylonitrile is used as the starting material, ethylene cyanohydrin and β-hydroxypropionamide begin to form in large quantities after long periods of operation. It is disadvantageous to remove these impurities from the final product. The causes of these are not known, but as soon as the amount of by-products in the reactor begins to reach an unacceptable level, the reactor must be closed, emptied, and then refilled. The problem of by-product formation or lack of catalyst selectivity is particularly important when the process is carried out under conditions where the catalyst is highly active, especially at elevated temperatures, typically above 110°C. At these high temperatures, the catalyst is more active and hydrolysis proceeds faster, but it is less selective and therefore more by-products are formed than at lower temperatures. Currently, the most reliable method of achieving high purity is using enzymes, but these methods are operationally inconvenient. Chemical Abstracts
Abstracts) Vol. 99, No. 22951g, states that the selectivity of reduced copper oxide catalysts can be increased by treating the catalysts with sulfuric acid or acrylic acid before use. In methods using Raney copper as a catalyst, the copper is conveniently made by treating the copper alloy with alkali and then washing the catalyst with water to remove free alkali from the catalyst. Therefore, in the current state of the art, many proposals have been made regarding how to prepare catalysts for use in hydrolyzing nitriles to amides, and how to carry out the hydrolysis while improving their activity. Increasing activity (especially when operating at temperatures above 110° C.) is always accompanied by increased formation of by-products. It is highly desirable to be able to achieve satisfactory activity while minimizing the formation of by-products. In the present invention, the formula RCONH ₂ (wherein R is an ethylenically unsaturated hydrocarbon group having 2 to 10 carbon atoms)
amide was made by hydrolyzing the corresponding nitrile RCN in a reaction mixture consisting of a solid catalyst for hydrolysis, water, an oxidizing agent, and a polymerization inhibitor, and the formation of by-products was oxidized in the reaction mixture. It is suppressed by adding reagents that degrade some (but not all) of the sites. The oxidizing agent has the effect of increasing the catalytic activity by forming oxidized catalytically active sites on the catalyst. The water therefore contains a dissolved reagent and a dissolved oxidant (which may be gaseous oxygen) to decompose some, but not all, of the oxidized sites. To obtain good catalytic activity in the process, many catalytically active sites must be present on the catalyst, but too many catalytically active sites on the catalyst will increase the formation of by-products. This is considered to indicate a tendency to Therefore, the active sites on the catalyst should not be in a continuous layer. The active sites to be oxidized are considered to be anionic salts. Prior to this invention, "over oxidised" catalyst had low activity, so it was not possible to leave this material in the reactor as a relatively inert material when new catalyst was introduced into the reactor. It was considered harmless. It is now recognized that this "over-oxidized" catalyst is not inert and on the contrary promotes the formation of by-products. Accordingly, the present invention forms sites by oxidation during the process and decomposes some of the sites formed to keep the number of sites below a level where by-product formation becomes significant. Rather than forming the desired number of sites without subsequently destroying the sites, it is necessary to form the sites and disassemble the sites. This is because sites are necessarily formed continuously during the process, so if the sites are not decomposed, it is inevitable that the number of sites on the catalyst surface will increase continuously in long-term batch or continuous processes. Because there is. The optimum degree of oxidation of the catalyst, and thus the relative proportions of oxidizing agent and site decomposition reagent, is determined by first operating the process with the oxidizing agent in the absence of decomposition reagent until optimal conversion is achieved, and at this level The process is continued until more product begins to form, at which point the decomposition reagent is gradually increased in small amounts until less by-product formation occurs and activity is substantially maintained. It can be set by adding up to The site-degrading reagent is preferably an acid (or a non-interfering salt thereof) that is non-oxidizing compared to the reducing agent or said oxidizing agent. It is water soluble. Regardless of the precise mechanism of operation of the present invention, the solid catalyst for the hydrolysis reaction of the present invention, water, an oxidizing agent that increases the activity of the catalyst by forming oxidized catalytically active sites on the catalyst, and the corresponding nitrile in a reaction mixture consisting of a polymerization inhibitor.
The method for producing an amide of the formula RCONH ₂ (wherein R has the same meaning as above) by hydrolyzing RCN is characterized by an acid that is non-oxidizing with respect to the oxidizing agent,
A reagent selected from a non-interfering salt thereof and a reducing agent is added to the reaction mixture in an amount sufficient to reduce by-product formation but insufficient to substantially reduce amide formation. The purpose of this is to suppress the formation of by-products. The invention is preferably carried out in the presence of an inactive catalyst that has remained in the reaction mixture and a newly introduced active catalyst. A preferred step for carrying out the process therefore comprises substantially continuously feeding water, catalyst, oxidizing agent, nitrile and certain reagents into a reaction vessel, substantially continuously removing the resulting amide from the vessel, and It consists of greatly increasing the amount of solid catalyst in the vessel during the process and discharging the catalyst from the vessel. The components of the reaction mixture may be introduced into the vessel individually or in combination in a truly continuous or discontinuous manner, and the reaction products may be removed from the vessel in a truly continuous or discontinuous manner. However, the catalyst is not removed from the container for a long time. Or, it is taken out at a lower rate than the introduction rate,
As a result, the amount of catalyst in the vessel increases significantly during the process, eg more than twice the weight of catalyst at the beginning of the process is finally discharged. Typically, the process is continued until the reaction vessel is filled with catalyst such that there is insufficient liquid phase volume, at which point the catalyst is discharged from the vessel. The reaction temperature in the container is preferably 100-150°C, most preferably 110-130°C. The inclusion of a site-degrading reagent in the reaction mixture allows the present invention to increase the overall activity of the catalyst, reaching an optimum temperature of 5 to 15 °C lower than the optimum in the absence of said reagent. Results can be obtained. Best results are usually
Obtained at a temperature of 115-125°C, preferably about 120°C. The hydrocarbon group R is preferably an olefin group having 2 to 8 carbon atoms. The process of the invention is most useful when applied to the production of acrylamide or methacrylamide from acrylonitrile or methacrylonitrile. The solid catalyst may be selected from any solid catalyst suitable for use in hydrolysis in the presence of an oxidizing agent, such as those described in US Pat. No. 3,997,606. Preferred catalysts are copper-containing catalysts. Best results are achieved using a substantially black copper catalyst. Red, pink or salmon colored copper does not appear to be useful as a catalyst in the present invention. However, they can be used, for example, as raw materials to make black copper catalysts by oxidation during the process. The reactor can therefore be filled with salmon, red or pink powdered copper and oxidized to a black state in the reactor, usually before passing the nitrile through the reactor. The catalyst may be true black, for example black-purple, but must not be pink, red or salmon colored. Suitable black copper catalysts are described in US 4,169,107. Black copper catalysts are made by reducing copper oxide and are generally Ullmann copper, preferably Raney copper. The exact chemical state of the black copper catalyst is unknown, but it probably consists of metallic copper supporting a partially oxidized surface layer. Preferred catalysts have extremely large surface areas;
A typical example is Raney copper. The black copper catalyst can be introduced into the reactor from the start of the process in a partially oxidized state to have optimal activity. For example Raney copper, e.g.
Oxygen, peroxides, as described in EP78178
Partial peroxidation may be achieved with a controlled oxidation system consisting of iodates, chlorates, bromates, nitrates, nitrites or other suitable oxidizing agents. Although it is not essential to slowly (carefully) add the oxidizing agent to the water used to hydrolyze the nitrile to the amide, in practice (unless excessive precautions are taken) the dissolved oxygen in This water will contain some oxidizing agent. When the oxidizing agent is not added slowly, it is useful to carry out the process using a weak reducing agent or acidic buffer to compensate for the inevitable gradual oxidation of the already oxidized catalyst. When the catalyst is introduced in partially overoxidized form, as mentioned above, or as e.g. Raney copper, Ullmann copper or reduced copper oxide, it is common to gradually add the oxidizing agent to the reaction water. It is true. Oxidizing agents include oxygen dissolved in the reaction water (either present as an incidental impurity or carefully metered into the water), iodates, chlorates, bromates,
Can be nitrates, nitrites. Very strong oxidizing agents such as permanganates and dichromates are generally unsatisfactory because they oxidize the catalyst very quickly and the formation of by-products is difficult to control. Oxidizing agents that generate free radicals, such as peroxides, persulfates, and perborates, are generally unsatisfactory because they can produce polymerization of unsaturated amides. Preferred oxidizing agents are nitrates. This and other oxidizing anions are introduced in convenient forms, for example as salts with sodium, potassium, lithium, zinc, preferably aluminum or copper. Particular preference is given to using copper salts, such as copper nitrate, whose introduction results in the dissolution of monovalent copper in solution, which acts as a polymerization inhibitor. If necessary, further monovalent copper or other conventional polymerization inhibitors may be added to prevent the unsaturated material from polymerizing during the process, especially during product withdrawal. A suitable mild reducing agent that may be added to prevent the formation of by-products is sodium borohydride.
However, the added reagent is preferably an acidic buffer. More preferred acidic buffers are water-soluble non-polymerizable organic carboxylic acids in free acid or salt form, especially aliphatic monocarboxylic acids having 2 to 8 carbon atoms, particularly preferably acetic acid. Polymerizable carboxylic acids such as acrylic acid are less suitable because they can react within the reaction mixture to form various by-products. Other organic acid buffers that can be used instead of using non-polymeric aliphatic monocarboxylic acids can include dicarboxylic acids such as succinic acid and aromatic acids such as benzoic acid and aminobenzoic acid. Acid dissociation constant
pKa ₁ is preferably 2 to 7, most preferably 4 to 7.
It is 6. Acidic buffers can be introduced in the form of free acids or water-soluble salts, preferably with weak bases. When the acidic buffer is introduced as a salt, the cations of the salt must not interfere with the hydrolysis or the use of the amide formed by subsequent hydrolysis. It is therefore best to avoid the use of many metal cations. Although alkali metals such as sodium are sometimes used, the presence of these or other undesirable cations when the final product is purified by ion exchange can result in unwanted loading of the ion exchanger. obtain. Preferably, the acidic buffer is introduced as the free acid (eg acetic acid) or a copper salt such as copper acetate; other possible salts include aluminum and sodium salts such as sodium acetate. The acidic buffer or weak reducing agent may be added at intervals from the beginning of the process or only after a long period of time, for example when by-products begin to form. Once the addition has begun, the addition may be continuous or intermittently, or the weak reducing agent or acidic buffer may be added for a short period of time, followed by further addition of the weak reducing agent or acidic buffer until by-products are formed again. The process may be continued without any modification. A surprising finding has been made that once an acidic buffer or reducing agent is added to a reactor, there is little tendency for subsequent additions of catalyst to lead to large amounts of by-products being produced. In preferred methods using copper nitrate and acetic acid or other carboxylic acids (often as copper salts), the preferred molar ratio of copper nitrate:acetate is from 2:1 to
1:50, preferably 1:5 to 1:30, at which time acetate is added continuously. The amount when added batchwise is typically 100-1000 ppm, preferably 300-600 ppm. The copper concentration in the solution in the reactor is generally 10~
1000 ppm, preferably 50 to 500 ppm.
The concentration of oxidizing agent and buffering agent/reducing agent (when present) each is generally 10-5000 ppm, preferably 100-1000 ppm. When a strong acid, a salt thereof, or a reducing agent is used in place of acetic acid, other weak reducing agents, or acidic buffers, the amount thereof is generally around the lower limit or below this range. This is because when the amount increases, the catalyst becomes totally inactive. For example, when using black Raney copper, do not use such amounts that the catalyst converts to the pink, red, or salmon state. This conversion results in insufficient activity to hydrolyze the nitrile to the amide. The strength of the reducing agent or acidic agent and the amount of reducing agent or acidic agent must be such that by-products are formed only as desired without substantially and unacceptably reducing amide formation. When a strong acid is used in carefully controlled amounts, it must be non-oxidizing with respect to the oxidizing agent. Therefore, in order to be able to control the effects caused by overoxidation of the catalyst, these anions must either be non-oxidizing or oxidize the catalyst weakly compared to the oxidizing agent. Acidic substances are free acids such as hydrochloric acid, hydrofluoric acid, sulfuric acid, phosphoric acid, phosphorous acid, sulfurous acid, sulfonic acid or sulfamic acid, including, for example, acrylamide methylpropanesulfonic acid, trichloroacetic acid. or their salts with weak bases, such as copper, aluminum or millet, such as copper sulfate or copper chloride. Salts of strong acids and strong bases are unsatisfactory. The amount of these strong acids and salts with strong acids must be very small. For example, the molar ratio of copper nitrate or other oxidizing anion to the anion of the strong acid is 1:1 or less. Setting high ratios, such as 1:2, for long periods of time is undesirable as it converts the black copper catalyst to the less active pink, salmon or red forms. When the molar amount of strong acid is very low, it is difficult to avoid deactivation of the catalyst when adding acid continuously, and therefore when strong acid has to be used it is added batchwise, preferably during the entire process. Add once. For example, if a gradual increase in the formation of by-products is observed in any process, the tendency to form by-products can be reduced or eliminated by adding a small amount of a strong acid or one of its salts. You may let them. The selectivity of the catalyst may be restored in the reaction mixture. Alternatively, the catalyst may be removed from the reaction mixture, treated with a strong acid or a suitable reducing agent or acidic buffer to restore selectivity, and then reintroduced into the reaction mixture. For example, a strong acid has a
The addition is continued for the time required for 0.2 to 2, preferably about 1, volume of liquid reaction mixture to pass through. The catalyst introduced into the reaction mixture is preferably a substantially black copper catalyst which has been washed with a reducing agent, strong acid or acid salt as described above. As described above, the washing liquid is preferably an aqueous solution of an acidic buffer or a salt thereof. Process for the hydrolysis of nitriles to amides, even if the catalyst is a virgin Raney or other black copper catalyst, which is washed before being introduced into the reaction mixture, and optionally with an oxidizing agent supplied to the reaction mixture. It may also be a catalyst that has been used as a catalyst and has become non-selective. The invention also relates to a process for preparing amides having a particular formula by hydrolysis of the corresponding nitrile in a reaction mixture consisting of a nitrile, water and a Raney catalyst, preferably a Raney copper catalyst. In said method, the Raney catalyst is washed with an aqueous solution of an acidic buffer, which is a non-polymerizable organic carboxylic acid or a salt thereof, before being introduced into the reaction mixture. The buffering agent is preferably an aliphatic monocarboxylic acid, generally acetic acid or copper acetate, with a preferred pKa of 2-7, more preferably 4-6. The Raney catalyst that undergoes this washing is usually prepared by conventional methods. For example, the alkali-soluble metal is leached from an alloy of the alkali-soluble metal with another metal, usually copper, iron, or nickel, with an alkali, such as sodium hydroxide, and then washed with water to a substantially constant pH, usually 7.5 to 10. Even if a conventional water washing process achieves a virtually constant pH, the catalyst may still contain undesirable basic sites in its structure, as basic materials likely remain from the leaching process. Probably. This washing step eliminates the problems that regularly occur when performing hydrolysis steps in the presence of Raney catalysts.
That is, an advantage is obtained that when adding new catalyst to the reaction mixture, the problem of heat generation always occurring with addition can be overcome. Therefore, when the reaction is running at a constant temperature, adding new catalyst will cause the temperature to rise and eventually return to the selected constant temperature. Although this temperature change is undesirable and promotes the formation of by-products, it has been accepted as inevitable. This temperature change is reduced or avoided by the cleaning method of the present invention. Washing with an acidic buffer neutralizes residual alkali that remains despite long conventional water wash treatments and deactivates excess active sites from the catalyst. Raney catalyst cleaning with acidic substances usually ranges from pH2 to
7, preferably using an aqueous cleaning solution of 3 to 7. substantially constant pH of the cleaning solution between 3 and 7.5;
It is preferred that the catalyst is stirred with the wash liquid until it has a PH, preferably below 7, for example between 5 and 7. When the acidic substance is a buffer or a weak acid, the wash duration and acid concentration are relatively unimportant; the acid concentration in the aqueous wash solution is typically 0.001-10%, preferably 0.01-1%. However, when using stronger acids, the acid concentration should be e.g.
It must be highly diluted, typically 5 to 50 ppm. If the concentration is too high or the period is too long, the activity of the catalyst in subsequent hydrolysis or other steps will be greatly reduced. The washing treatment can be applied to commercially available Raney catalysts before loading the catalyst into hydrolysis or other reaction mixtures, or as a final step during the production of Raney catalysts and then used in situ or separately. transport to the location. Acid cleaning is usually followed by water rinsing.
As described in European Patent Application No. 78178, the catalyst may be partially oxidized after acid washing and before use in the hydrolysis process. Typically, an alloy of copper and aluminum is
Leaching with sodium hydroxide at 50° C. and aging in solution in the usual manner yields granular Raney copper. Wash this with water and use 8 to 11.5
and then washing with acid according to the invention. Instead of copper-aluminum alloy as starting material,
For example, copper alloys with manganese or zinc can be used in the usual manner. By appropriate selection of the alloy, other Raney metals, such as Raney nickel or Raney iron, can be made in a conventional manner. The catalyst is preferably in particulate form, usually supplied as an aqueous slurry, and loaded into the hydrolysis or other reaction mixture to carry out the hydrolysis step at the desired, usually elevated, controlled temperature. The catalyst can be used at the beginning of the process. Charge of catalyst to the reaction mixture may be continuous or intermittent. The hydrolysis step may be carried out in the absence of a dissolved active agent as described in US Pat. No. 3,894,084 or in the presence of a dissolved active agent as described in US Pat. No. 3,911,009. It's good to wear. The method of the present invention, in which hydrolysis is carried out in the presence of reducing agents, buffers or other reagents, involves filling a reactor with a catalyst, feeding water, nitrile and nitrate or other oxidizing agent into the reactor, and discharging water from the reactor. The amide is removed continuously and, if necessary, a weak reducing agent or acidic buffer is supplied to the reactor to remove the amide when the activity eventually decreases and/or when spent catalyst accumulates in the reactor and/or by-products. This can be carried out to great advantage by draining the reactor when product formation becomes intense. Although the above evacuation is usually not necessary for at least 4 weeks after initiation, and often 88, 12, 16 or more weeks, conventional methods require reaction temperatures of 120-130
℃, it was necessary to discharge within 2 to 3 weeks from the start. The period before draining the catalyst can be extended by short-term addition of small amounts of strongly acidic substances when necessary to return the catalyst to a substantially by-product free state. Preferably, therefore, copper nitrate is added continuously, an acidic buffer such as copper acetate or acetic acid is added continuously or intermittently, and a small amount of a strongly acidic substance such as CuCl ₂ is added from time to time. The process of the invention has considerable advantages over processes carried out under substantially the same conditions except for the addition of acetic acid or other acidic substances or reducing agents. One of the advantages is that the quality of the amide obtained is very high and the degree of contamination is low. This is evident from the fact that when the amide is a polymerizable amide such as acrylamide, polymerization under standard conditions yields polymers with high intrinsic viscosity. Another advantage is that the formation of certain by-products such as ethylene cyanohydrin is reduced.
The reduced formation of by-products is particularly useful in large-scale industrial processes intended to produce high yields of amides. This is because, prior to the present invention, increasing the amide production rate tended to result in the formation of more by-products. Yet another advantage is that the method can be more accurately reproduced from one run to the next. Yet another advantage is reduced consumption of solid catalyst. For example, the amount of Raney copper required in the process of the invention using nitrates and acetates is less than 75% of the amount required when using nitrates alone;
For example, it can be 66%. Yet another advantage is that the method can be easily processed from 5 to 15 °C without the addition of specific reagents and without loss of selectivity or activity.
This can be done at a temperature of Below are examples of the invention. Example 1 shows a suitable method for preparing a Raney catalyst for hydrolysis reactions, Examples 2 and 3 show a hydrolysis process carried out by adding appropriate reagents, and Example 4 shows a method for preparing an overoxidized copper catalyst. It has been shown in a laboratory method that the drawbacks can be overcome by adding strong acids or acid salts, and Example 5 shows the advantages of the method when carried out industrially. Example 1 A Raney catalyst is produced by leaching aluminum from a copper-aluminum alloy using sodium hydroxide using a conventional method, and leaving the resulting slurry with a pH of about 11.
It can be prepared by washing with deoxygenated water for a long time until the A portion of this water-washed catalyst is then washed with an aqueous acetic acid solution for an extended period of time until the resulting slurry upon standing has a substantially constant pH of about 5.5. Contains a liquid fill of approximately 30% acrylamide, 10% acrylonitrile and 60% water and approximately 250 ppm dissolved copper at approximately 125°C
Acrylamide is prepared in a sealed reactor maintained at a temperature of . Approximately 1/4 of the reactor's volume is occupied by granular copper, which is a blend of active Raney copper and spent copper catalyst. According to conventional methods, acrylonitrile, water and dissolved copper are fed substantially continuously, the contents are stirred substantially continuously, and acrylamide is removed from the reaction tube using a draft tube. When Raney copper must be replenished in the reactor, 1 kg (dry weight) of water wash or pickling slurry is added to the reactor for every 20 kg of spent copper in the reactor. When the catalyst to be added is a water-washed catalyst, the temperature inside the reactor will temporarily rise to about 140-145°C, so it should be returned to the set point of about 125°C, and then the temperature in the reactor should be returned to the set point of about 125°C. Since impurities are temporarily generated in large quantities, they must be returned to the previous level.
However, when adding acid-washed catalyst,
There is no substantial increase in temperature and impurity levels. Example 2 A stirred closed vessel was filled with Raney copper (to about 5% by volume of the reactor), 42.5% acrylonitrile and 57.5% acrylonitrile.
% water feed was passed into the reactor at 125° C. with stirring. The effluent from the reactor consisted of approximately 30% acrylamide, 20% acrylonitrile and 50% water, from which the acrylamide was worked up in a conventional manner. The water charged to the reactor contained an amount of dissolved copper salts such that the concentration of dissolved copper in the effluent was maintained at about 250 ppm. At initial start-up, water was fed with copper nitrate as the added copper salt, and within a few hours the reactor was working satisfactorily. The concentration of ethylene cyanohydrin was approximately 0.1% based on acrylamide. The ethylene cyanohydrin concentration after approximately 8 days of operation is
It increased to about 0.6% based on acrylamide. The copper nitrate feed is then completely replaced with copper acetate and introduced into the reactor for the required time to be introduced with copper acetate at the same copper ion concentration as the copper nitrate was being introduced; The feed was reintroduced. Ethylene cyanohydrin concentration decreased to 0.10% of acrylamide. The rate of acrylamide production remained essentially unchanged. Raney copper was introduced into the reactor as needed during the process. The ethylene cyanohydrin concentration remained essentially constant in the range of 0.10-0.2% on acrylamide for 48 days, at which point the copper nitrate feed was replaced with copper acetate as described above. Again, the ethylene cyanohydrin concentration decreased, but the overall rate of acrylamide production remained essentially constant. Example 3 The experiment was repeated using the same reaction system and reactants as in Example 1. However, acetic acid was continuously supplied. When Cu(NO ₃ ) was added to the reactor continuously for 12 hours as in Example 1, acrylamide was produced at a constant rate. The ethylene cyanohydrin concentration at this time is based on acrylamide.
It was 0.32%. Acetic acid was then continuously fed into the reactor in a molar ratio of 3/1 to Cu(NO ₃ ) ₂ .
After 5 days beta-hydroxypropionamide rose to 0.23% and ethylene cyanohydrin rose to 0.45% based on acrylamide. No change was observed in the rate of acrylamide production. When the addition of the Raney copper catalyst was discontinued after 7 days, the rate of acrylamide production decreased to 55% of the initial value. After 9 days, the concentrations of ethylene cyanohydrin and beta-hydroxypropionamide were respectively
It rose to 1.1% and 0.5%. The addition rate of acetic acid was doubled to give an acid:Cu ²⁺ molar ratio of 6/1. After 10 days, the concentrations of ethylene cyanohydrin and beta-hydroxypropionamide were each 0.9%,
Once it was down to 0.35%, I started adding catalyst again. By day 13, the acrylamide rate increased to the initial value, and the two impurity concentrations were 0.39% and 0.39%, respectively.
It was 0.225%. Example 4 To investigate the effect of adding strongly acidic substances to very highly oxidized catalysts forming by-products,
Creates a highly oxidized catalyst, including copper chloride, hydrochloric acid,
It was used in the presence of added sodium chloride, copper sulfate, sulfuric acid and sodium sulfate without further deliberate oxidation.
This is a short-term laboratory method; comparable industrial methods would require the addition of copper nitrate or other oxidizing agents during the long-term process. In this example, Raney copper is used as Cu ²⁺ as nitrate.
at 60°C using 200ppm (for Raney copper)
Pre-treated for 18 hours. The catalyst was then washed with deoxygenated water to remove soluble ions. This material was compared with washed but untreated copper as a catalyst for the hydration of acrylonitrile to acrylamide as follows. 0.15 g of copper catalyst, 3.15 g of deoxygenated water, and 2 cm ³ of deoxygenated acrylonitrile were placed in a glass test tube, cooled in liquid nitrogen, and the tube was sealed. The tube and contents were heated to 130°C in an oil bath for 3 hours. The tube is then cooled to room temperature, opened, and the degree of conversion of the contents determined by GLC.
It was analyzed in The results are shown in Table 1.

[Table] Reserve
Reason
The above results show that pre-treatment of the copper catalyst with copper nitrate () increases the yield of acrylamide, but also significantly increases the impurity level. This overoxidized catalyst was used in three tests. In one test, various amounts of copper chloride, hydrochloric acid, or sodium chloride were added. In another test, a very small amount of copper chloride was added, and in a third test, various amounts of copper sulfate, sulfuric acid, and sodium sulfate were added. The results are shown in Tables 2, 3 and 4.

【table】

【table】

[Table] These results show that using a small amount of copper chloride suppresses the formation of impurities without reducing the amount of acrylamide produced, and that using a very small amount when starting from an excess oxidation catalyst increases the amount of acrylamide produced and It is found that the amount of impurities formed is also suppressed. It has been found that while hydrochloric acid can reduce the formation of by-products to some extent, the effect is small in the case of sodium chloride. It has also been found that increasing the amount of copper chloride can reduce the amount of impurities produced, but also reduces the amount of acrylamide formed. The above results show that copper sulfate and sulfuric acid have similar effects, but a salt of a strong acid and a strong base (sodium sulfate) causes significant deterioration. Example 5 A stirred closed reactor was charged with approximately 5% by volume Raney copper washed with aqueous acetic acid and a feed of 42.5% acrylonitrile and 57.5% water. Raney copper was added during this step. The starting water contained copper nitrate and acetic acid in a molar ratio of 1:2. During the first three weeks of operation, the ethylene cyanohydrin content was approximately
It changed from 0.06 to 0.14%. The amount of acetic acid also increases, the molar ratio of copper nitrate and acetic acid becomes 1:18, and the temperature becomes approximately
The temperature dropped to 120℃. Over the next three weeks the ethylene cyanohydrin content was maintained at a level of 0.02-0.05%. The yield of acrylamide was 99.8% based on acrylonitrile.

[Claims]

1 Structural formula below Physiologically active substance aldostatin or its non-toxic salt. 2 Belongs to the genus Pseudoeurotium and has the following structural formula The physiologically active substance aldostatin-producing bacteria expressed as