Organic compounds -- part of the class 532-570 series – Organic compounds – Amino nitrogen containing
Reexamination Certificate
1997-11-26
2001-09-18
Kumar, Shailendra (Department: 1621)
Organic compounds -- part of the class 532-570 series
Organic compounds
Amino nitrogen containing
C564S134000, C564S135000, C564S137000, C564S138000
Reexamination Certificate
active
06291712
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a process for producing a saturated aliphatic carboxylic acid amide (hereinafter often referred to simply as “carboxylic acid amide”) which is widely used as solvents, solubilizing agents, plasticizer stabilizing agents, dyes, drugs and materials for use in organic syntheses. More particularly, the present invention is concerned with a process for effectively producing a highly purified carboxylic acid amide with the formation of by-products suppressed, in which a dehydration reaction of an ammonium salt obtained from corresponding saturated aliphatic carboxylic acid (hereinafter often referred to simply as “carboxylic acid”) and ammonia is conducted while supplying water to the reaction system to thereby obtain a carboxylic acid amide.
Further, the present invention relates to a process in which part of water is separated and removed from a mixture of a saturated aliphatic ammonium carboxylate and water by distillation. More particularly, the present invention is concerned with a process for efficiently recovering a saturated aliphatic ammonium carboxylate by adding a saturated aliphatic carboxylic acid to a mixture of a saturated aliphatic ammonium carboxylate and water and thereafter conducting a distillation.
BACKGROUND OF THE INVENTION
It is known that the carboxylic acid amide can be produced by synthesizing an ammonium carboxylate salt from a carboxylic acid and ammonia and subjecting the salt to a dehydration reaction.
The carboxylic acid amide can be produced by a batch process or a continuous process. In an industrial process, conditions for separating and purifying the carboxylic acid amide as a product and conditions for removing and recycling by-products and unreacted raw materials are greatly influenced by, for example, the types and properties of desired carboxylic acid amide, individual starting materials and by-products. In particular, the cost and availability of raw materials, the final yield of desired product after separation and purification, the simplicity of entire production steps including a separation/purification system, the cost of production facility construction, the operation efficiency, the utility cost, etc. are extremely important factors, and an industrial process must be decided by collectively judging all of these. When the carboxylic acid amide is produced by, for example, a batch process, conventionally, the reaction temperature is set at 150 to 220° C. and the reaction time at 12 to 30 hr. and water formed as a by-product by the reaction is removed from the top of the reactor as a low boiling point fraction.
When the carboxylic acid amide is produced by this process, the conversion of the ammonium carboxylate can be 90% or higher. However, by-products such as nitrile compounds and carboxylic acid amide dimerization products are formed in relatively large amounts, so that the selectivity of carboxylic acid amide is as low as 90 to 95% and the final yield of carboxylic acid amide is also not satisfactory. Moreover, the production of carboxylic acid amide by the batch reaction prolongs the processing time and increases the formation of by-products, so that the above process cannot be regarded as an industrially advantageous process from a judgement of its productivity and economy.
For example, U.K. Patent No. 935,391 and Japanese Patent Laid-open Publication No. 57(1982)-38754 disclose a continuous process for producing a carboxylic acid amide, in which a carboxylic acid or an ammonium carboxylate is continuously fed into a reaction column through its top or its middle while ammonia is continuously fed into the reaction column through its lower part to thereby obtain a carboxylic acid amide.
In this process, with respect to reaction starting materials, ammonia is used in excess of the carboxylic acid. The excess ammonia is distilled out from the top of the reaction column together with water. For condensing the fraction from the top of the reaction column to thereby attain a recovery, a cooling medium of extremely low temperature must be used. Further, it is needed to install a separator for distilling water off recovered aqueous ammonia and install an absorption column for recovering ammonia gas obtained by this separation. Therefore, the above process cannot be regarded as a process which is satisfactory from the viewpoint of economy and operation efficiency.
In the process described in these published specifications, much of ammonia gas formed by a a decomposition reaction of ammonium carboxylate is distilled outside the system from the top of the reaction column. Therefore, the above process involves problems such that not only is the yield of carboxylic acid amide relative to the amount of ammonia added as a starting material unsatisfactory but also by-products such as nitrile compounds and carboxylic acid amide dimerization products (dimerized amide of carboxylic acid) are formed in relatively large amounts.
Therefore, there is a demand for the development of a process for producing a carboxylic acid amide, which enables producing a highly purified carboxylic acid amide at a high yield from a carboxylic acid and ammonia as raw materials.
In addition to the above processes, a process for producing a carboxylic acid amide has been proposed, in which the carboxylic acid amide is produced from an ammonium carboxylate in the presence of a dehydration catalyst. In this process, molybdenum oxide, an alkyltin catalyst, a mixture of silica gel and alumina or a titanium tetrachloride catalyst is used as the dehydration catalyst.
In this process, the dehydration reaction can be carried out at relatively low temperatures, so that not only can the formation of by-products such as nitrile compounds and carboxylic acid amide dimerization products be suppressed but also the reaction time can be shortened. However, when the carboxylic acid amide is produced with the use of the catalyst, it is apprehended that the catalyst be dissolved or otherwise contained in the obtained carboxylic acid amide and, hence, a step of separating or otherwise removing the catalyst from the carboxylic acid amide after the completion of the reactions becomes requisite. If costs of catalyst production and catalyst removal incurred by the use of the catalyst, etc. are taken into account, this process also cannot be regarded as a satisfactory process.
The applicant of the present patent application proposed in Japanese Patent Laid-open Publication No. 9(1997)-157233 a process for producing a carboxylic acid amide represented by the formula: RCONH
2
(wherein R represents a saturated alkyl group having 1 to 4 carbon atoms), comprising:
a first step comprising supplying, to a reactor consisting of a rectifying tower and a reaction vessel, a carboxylic acid represented by the formula RCOOH (wherein R is as defined above) and an ammonium salt thereof (provided that, in the total supply, the molar amount of the carboxylic acid is in the range of from 0.1 to 2.0 times that of the ammonium salt), which are fresh or recycled from the following second and third steps; conducting a dehydration reaction of the ammonium salt at 130 to 200° C.; and distilling mixture components consisting of formed water and the carboxylic acid and/or unreacted ammonium salt off the top of the rectifying tower to thereby obtain components containing the carboxylic acid amide from the reaction vessel;
a second step comprising distilling the components containing carboxylic acid amide obtained in the first step to thereby purify the carboxylic acid amide; and
a third step comprising distilling water off the mixture components consisting of water and carboxylic acid and/or unreacted ammonium salt recovered in the first step.
This process enables producing a highly purified saturated lower alkyl carboxylic acid amide simply at a high yield with an industrial advantage, as compared with the above prior art processes. However, this process has room for improvement because by-products such as dicarboxylic acid amides and carboxylic acid salt of amidine ar
Aizawa Toshiyuki
Katayama Masaaki
Nakamura Hitoshi
Saihata Shinya
Kumar Shailendra
Showa Denko K.K.
Sughrue Mion Zinn Macpeak & Seas, PLLC
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