CROSS-REFERENCE TO RELATED APPLICATIONS This application is a continuation of U.S. Application 15/644,708, filed on July 7, 2017, the contents of which are incorporated herein by reference.

TECHNICAL FIELD

The present invention relates to a method for the production of monomers for long chain nylons, more specifically, it relates to a process for the production of long chain amino acids and dibasic acids.

BACKGROUNDS OF THE INVENTION

Long chain saturated aliphatic amino acids, lactams, and dibasic acids are important monomers for long chain nylons and engineering plastics. Nylons are a class of polymers that contain amide bond on their backbone of chains. Nylons are one of the most widely used, most numerous in types, and most consumed class of engineering plastics.

Because of their unusual molecular structure, long chain nylons possess extraordinary physical properties, i.e., higher mechanical strength than metal, low hygroscopicity, excellent resistance to oil, low temperature, abrasion, and chemical corrosion, and most importantly, easy to fabricate. Long chain nylons are made into many kinds of plastics products, spun to fibers, and stretched to thin films. Long chain nylons are also used in paints and hot melt adhesives. Hence, long chain nylons find wide applications in automobile, electrical, electronic, telecommunications, petrochemical, and aerospace industries.

Long chain amino acids and lactams are used industrially as monomers to produce nylon- 9, nylon-11, and nylon-12.

Long chain dibasic acids are condensed with diamines industrially as starting materials to produce nylon-610, nylon-612, nylon-510, nylon-512, nylon-1010, and nylon-1212.

Among the current production technologies, the nylon-9 monomer, 9-aminononanoic acid is produced from oleic acid or oleonitrile by a series of chemical reactions (details are described in J. Am. Oil Chemist's Soc, 1975, Vol. 52, No. 11, pp 473-477).

For the nylon-11 monomer, 11-aminoundecanoic acid, is produced from castor oil through ester exchange with methanol, pyrolysis at high-temperature, free radical addition of anhydrous hydrogen bromide, and finally ammonolysis (detailed process is described by A. Chauvel & G. Lefebvfre, Petrochemical Processes 2: Major Oxygenated, Chlorinated and Nitrated Fatty acids, pp 274-278). The overall yield is not more than 55%.

The monomer of nylon-12, laurolactam, is produced from 1,3-butadiene through a series of reactions, i.e., trimerization to cyclododecatriene, hydrogenation to cyclododecane, oxidation to cyclododecanol or cyclododecanone, oximation, and Beckmann rearrangement (detailed process is described by A. Chauvel & G. Lefebvfre, Petrochemical Processes 2: Major Oxygenated, Chlorinated and Nitrated Fatty acids, pp 279-286).

In the industrial production of long chain dibasic acids, azelaic acid is produced from oleic acid by oxidation, while sebacic acid is produced by alkaline scission of castor oil or fatty acids at high temperature (200 °C to 250 °C), followed by purification and refining.

For the important dodecanedioic acid, there are two industrial processes of quite different nature. One is the chemical synthesis from 1,3-butadiene through catalyzed trimerization to cyclododecatriene, hydrogenation to cyclododecane, oxidation to cyclododecanol or cyclododecanone, and finally, oxidation by nitric acid. The other process is more preferable, i.e., biochemical oxidation of terminal methyl groups of high purity dodecane or lauric acid by fermentation.

In the production of these monomers by chemical synthesis, there exist problems for the current industrial processes, e.g., low overall yield (35% for 9-aminononanoic acid, 55% for 11- aminoundecanoic acid, 80% for sebacic acid), reaction conditions that are inherently dangerous and difficult to control. For example, the production of 9-aminononanoic acid requires the use of ozone, and the production of 11-aminoundecanoic acid requires a pyrolysis reaction at high temperature. Moreover, the production of laurolactam and dodecanedioic acid makes use of trimerization of 1,3-butadiene under inert reaction conditions with a flammable catalyst, while the production of sebacic acid requires a very corrosive alkaline scission of castor oil.

Although the reaction conditions are mild, fermentative oxidation of long chain alkanes or lauric acid via fermentation to produce dodecanedioic acid or other long chain dibasic acids, yields a crude product that contains a large amount of biomaterials and degraded short chain dibasic acids. To obtain a product suitable for the production of nylons, crude product must be subjected to complicated purification and refinement. Many methods to refine and purify the crude products are described in the literature. Detailed processes are disclosed in U.S. Pat. No. 6,218,574; U.S. Pat. No. 8,729,298; CN 104591998 A; CN 102476990A; CN 102329224A; CN 103497100A; CN 102795989A; CN 104447274A; CN 104447280A; CN 104496793 A; CN 104529741A; CN 104529747A.

WO 2017088218 by the present inventor discloses a novel process for the co-production of long chain amino acid and dibasic acid. According to the disclosed process, keto fatty acid ester or amide is reacted with hydroxylamine to form an oxime fatty acid derivative, which is subjected to the Beckmann rearrangement to form a mixture of two amide fatty acid derivatives. When the mixed amide derivatives are hydrolyzed, a mixture of long chain amino acid and dibasic acid is obtained and separated in high dilution.

The process according to WO 2017088218 starts from an inconvenient starting material, i.e., keto fatty acid ester or amide, which is not commercially available. Moreover, during the preparation of oxime, the ester is not stable and is hydrolyzed to produce a significant amount of an alkali salt of oxime fatty acid, which is soapy and renders processing difficult. Furthermore, this impurity interferes with the Beckman rearrangement and inactivates the catalyst.

During the hydrolysis of the mixed amide fatty acid derivatives, prepared according to WO 2017088218, to long chain amino acid and dibasic acid, a lower alcohol, i.e., methanol or ethanol, is released from the hydrolysis of ester group. This lower alcohol complicates the separation of alkylamine, particularly for hexylamine, which forms with an azeotrope with water The formation and separation of this azeotrope are greatly influenced by methanol or ethanol.

In addition, there is a need for the separation of short chain alkylamine and alkanoic acid, produced along with long chain amino acid and dibasic acid, for the process to be economically successful and environmentally safe.

It is an object of the present invention to overcome the disadvantages by disclosing a process for producing long chain amino acid and dibasic acid from hydroxy fatty acid, in particular, 12-hydroxy stearic acid, which is a commercially available, stable starting material.

DESCRIPTION OF THE DRAWING FIG. 1. Reaction scheme for producing long chain amino acid and dibasic acid from hydroxy fatty acid.

DESCRIPTION OF THE INVENTION It is an object of the present invention to overcome the disadvantages of current industrial processes and to disclose a process for the coproduction of long chain amino acids and dibasic acids. In comparison to current industrial processes, the process disclosed in the present invention utilizes mild reaction conditions, provides a high overall yield, and is particularly suitable for industrial production.

The present invention employs commercially available hydroxy fatty acid (I) as starting material to produce long chain dibasic acids (V) and amino acids (VI), according to the reaction scheme schematically illustrated in the FIG., wherein m is an integral of 0 to 10; n is an integral of 6 to 20. The process according to the present invention proceeds according to the following steps:

(1) oxidizing the starting material, hydroxy fatty acid (I), to keto fatty acid (II);

(2) reacting a keto fatty acid (II) with a solution of hydroxylamine to form an oxime fatty acid (III) or subjecting a keto fatty acid to an ammoximation reaction to form an oxime fatty acid (III) in the presence of an organic solvent;

(3) subjecting the oxime fatty acid (III) to the Beckmann rearrangement to form a mixture of amide fatty acids of the structure (IVa) and (IVb) in the presence of one or more catalysts;

(4) hydrolyzing the mixed amide fatty acids (IVa) and (IVb) to yield long chain dibasic acid (V), long chain amino acid (VI), short chain primary alkylamine (VII), and short chain alkanoic acid (VIII); and

(5) separating long chain amino acid (VI), long chain dibasic acid (V), and alkanoic acid (VIII) from their respective alkali salt by a step-wise neutralization or acidification.

It is noted that the starting material is 12-hydroxy stearic acid, when m=5, n=10. According to the process disclosed in the present invention, the monomer of nylon-11, 11- aminoundecanoic acid is coproduced along with dodecanedioic acid, an important monomer for the production of nylon 612 and nylon 1212.

When m=7, n=8, the starting material is 10-hydroxy stearic acid. According to the process disclosed in the present invention, 9-aminononanoic acid, the monomer for nylon-9 is coproduced along with sebacic acid, which is used in the production of nylon 610 and nylon 1010. When m=5, n=12, the starting material is 14-hydroxyarachidic acid. According to the process disclosed in the present invention, 13-aminotridecanoic acid, the monomer for nylon-13, is coproduced along with tetradecanedioic acid (i.e., brassylic acid).

Oxidation of hydroxy fatty acid (I) to keto fatty acid (II) can be performed with sodium hypochlorite or calcium hypochlorite in an aqueous acetic acid at a temperature from 0 °C to 40 °C, preferably, from 0 °C to 20 °C. After the oxidation reaction is completed, acetic acid is removed by distillation, and the residual is suspended with water to dissolve sodium chloride or calcium chloride. The keto fatty acid (III) is recovered by means of solid-liquid separation.

Oxidation of hydroxy fatty acid (I) to keto fatty acid (II) can also be carried out with hydrogen peroxide with a tungsten or a molybdenum compound as catalyst in the presence of a phase transfer catalyst. The oxidation of hydroxy fatty acid with hydrogen peroxide can be carried out in the presence of an organic solvent, more preferably in the absence of an organic solvent. After the oxidation is completed, molten keto fatty acid is separated from aqueous solution by a phase separation at a temperature from 50 °C to 90°C.

In order to obtain the oxime fatty acid (III), a keto fatty acid (II), is dissolved in an organic solvent, and reacted with aqueous solution of hydroxylamine salt with a basic agent to adjust the pH of the reaction mixture.

The organic solvent for the oximation reaction can be either water soluble or water insoluble. The requirement for a selected solvent is that the solvent can dissolve both the keto fatty acid (II) and oxime fatty acid (III), and does not react with starting material, product, and hydroxylamine. For example, aldehydes and ketones as solvents are not suitable for preparing oxime, because the solvents will react with hydroxylamine. Nitriles are also not suitable as the nitrile group can react with hydroxylamine. Amines will react with ketone to form Schiff base and are therefore not suitable solvents.

Suitable solvents belong to the classes of alcohols, esters, aliphatics, aromatics, ethers, and amides. Preferable solvents are, but not limited to, methanol, ethanol, propanol, isopropanol, n-butanol, isobutanol, sec-butanol, tert-butanol, amyl alcohols, hexanols, cyclohexanol, ethyl acetate, butyl acetate, isobutyl acetate, propyl acetate, isopropyl acetate, ethyl propionate, propyl propionate, isopropyl propionate, propyl formate, butyl formate, isobutyl formate, benzene, toluene, xylenes, cumene, trifluoromethylbenzene, diethyl ether, dipropyl ether, dibutyl ether, diisopropylether, tetrahydrofuran, methyltetrahydrofuran, dioxane, dimethyl formamide, dimethyl acetamide, N-methyl pyrrolidone, tetramethylurea, dichloromethane, dichloroethane, chloroform, and a mixture of two or more thereof.

The most preferable solvent is toluene.

The present inventor found that the oximation reaction can be performed in the absence of organic solvent. An oil phase of keto fatty acid is reacted with an aqueous solution of hydroxylamine salt with a basic agent to adjust the pH of aqueous reaction solution. After the reaction, the product is simply separated by a phase separation from aqueous phase and dehydrated for the next stage of the process.

An hydroxylamine salt is selected from the group consisting of hydroxylamine hydrochloride, hydroxylamine sulfate, and hydroxylamine acetate. An aqueous solution of hydroxylamine can also be used.

A basic agent, used to maintain pH of the oximation reaction, is selected from the group consisting of alkali and ammonium salts of hydroxide, bicarbonate, carbonate, sulfite, bisulfite, phosphate, and carboxylate. The alkali metals are lithium, sodium, potassium, or cesium.

Suitable basic agents are, but not limited to, sodium hydroxide, potassium hydroxide, sodium bicarbonate, sodium carbonate, potassium bicarbonate, potassium carbonate, ammonium hydroxide, ammonia, ammonium carbonate, ammonium bicarbonate, sodium formate, sodium acetate, potassium formate, potassium acetate, ammonium phosphate, sodium phosphate, and a mixture of two or more thereof.

The most preferable agent is ammonium hydroxide.

It is necessary to maintain a proper pH in order for the oximation to proceed to completion. Although oximation reaction can proceed at a pH in the range from 2 to 10. It is found that the reaction solution becomes soapy at a pH of 6 and above, so higher pH cannot be used. At a pH lower than 3, oximation reaction proceeds at a very low rate. Thus, it is preferable to maintain the pH in a range from 3 to 6, most preferably in a range of 3.5 to 5.5.

Oximation of a keto fatty acid can also be performed by an ammoximation reaction, i.e., the oxidation of ammonia by hydrogen peroxide in the presence of Ti-catalyst. Keto fatty acid is dissolved in an organic solvent, most preferably, toluene. Ammonia and hydrogen peroxide can be added concomitantly, sequentially, continuously, semi-continuously, or batch wise.

The oximation reaction is carried out at a temperature from 0 °C to 100 °C, but can also be carried out at higher temperature under pressure. This reaction is preferably carried out at a temperature from 40 °C to 100 °C under atmospheric pressure. If the temperature is low, the reaction rate is slow, and reaction time is unnecessarily prolonged. Preferably, the reaction temperature is selected to be 60 °C to 80 °C.

The oximation reaction is carried out in the air, but can also be carried out under the protection of inert atmosphere, i.e., nitrogen, argon, or helium.

Time for the completion of oximation is related to the reaction temperature, usually in about 0.5 to 24 hours. Preferably, the reaction time is maintained for 1 to 6 hours, and the reaction temperature is controlled at 0 °C to 100 °C. If the reaction time is too short, the residual content of keto fatty acid is too high, the yield will be reduced. Although the residual keto fatty acid can be recovered in the post treatment, additional equipment for recovery will be needed. Prolonged reaction can reduce the residual amount of keto fatty acid, but the volume of reactors becomes unnecessarily large.

Reactor for the oximation reaction can be any reactor conventionally used in the chemical processing, for example, batch stirred reactor, semi-continuous reactor, tubular reactor, or flow reactor. Preferable reactor is continuous stirred tank reactor (CSTR). If CSTR is adopted, an aqueous solution of hydroxylamine and a solution of a keto fatty acid in an organic solvent are simultaneously added in one reactor and then the reaction is completed in a cascade of reactors. On the other hand, the two solutions can be added to a stirred batch reactor concomitantly, sequentially, continuously, semi-continuously, or batch wise.

The molar ratio of hydroxylamine to a keto fatty acid (II) can be from 0.1 to 10.0, preferably 1.0 to 2.0, most preferably 1.05 to 1.1 to ensure that the keto fatty acid is completely converted to the oxime fatty acid (III).

After completion of the oximation reaction, the oxime fatty acid (III) remains dissolved in organic phase, and aqueous phase is separated. Although the solubility of water in organic phase is small, but the remaining trace amount of water will destroy the catalytic activity of the Beckmann rearrangement catalyst and must be removed. In order to remove trace amount of water from organic phase, a drying agent may be used. Preferably, the remaining water is removed by distilling part of the solvent. The distilled solvent can be used directly in the step of oximation without being dried. After distillation, the residual anhydrous solution of oxime fatty acid can be directly used for the Beckmann rearrangement. For the Beckmann rearrangement, the required solvents have to show good solubility towards both an oxime fatty acid (III) and mixed amide fatty acids, (IVa) and (IVb), and can dissolve catalyst for the Beckmann rearrangement and will not react with the catalyst.

A solvent for both the oximation and Beckmann rearrangement must be stable and amenable to recover. Different solvents can be used for the oximation reaction and the Beckmann rearrangement to satisfy the requirement of each reaction. Preferably, a single solvent is used to satisfy the requirement of both reactions in order to reduce the use and recycling of solvent. More preferably, the selected solvent is not water-soluble so that it can be easily separated after the oximation reaction and the Beckmann rearrangement. The amount of solvent used in both reactions is not particularly limited as the solvent only functions to dissolve the reactants and products.

Solvents that show the required properties for both the oximation and the Beckmann rearrangement belong to the classes of ester, aliphatics, aromatics, and ethers. Preferable solvents are, but not limited to, butyl acetate, ethyl acetate, benzene, toluene, xylene, cumene, anisole, diethyl ether, diisopropyl ether, dibutyl ether, methyl tert-butyl ether, ethyl tert-butyl ether, methyl tetrahydrofuran, petroleum ether, cyclohexane, dichloroethane, methylene chloride, chloroform, carbon tetrachloride, and trifluoromethylbenzene, and a mixture of two or more thereof.

The most preferable solvent is toluene.

After thorough drying, the oxime fatty acid (III) is subjected to the Beckmann rearrangement to a mixture of two amide fatty acids (IV) in the presence of one or more catalysts.

Suitable catalysts are, but not limited to, sulfuric acid, alkylsulfonic acid, arylsulfonic acid, perfluorocarboxylic acids, and trifluoroacetic acid.

Acetic acid containing hydrogen chloride, hydrogen bromide, or anhydride is also a suitable catalyst.

The free carboxylic acid in an oxime fatty acid (III) is expected to react with activated halogen compounds, thus these activated halogen compounds are not suitable catalyst for the Beckmann rearrangement of an oxime fatty acid. The present inventor surprisingly found that these activated halogen compounds are excellent catalyst alone or with a combination with a Lewis acid. Preferably, activated halogen compounds are activated chlorine compounds. Suitable activated chlorine compounds are, but not limited to, thionyl chloride, sulfuryl chloride, chlorosulfonic acid, various sulfonyl chlorides: i.e., methanesulfonyl chloride, toluenesulfonyl chloride, various carbonyl chlorides: i.e., formyl chloride, acetyl chloride, benzoyl chloride, oxalyl chloride, phosgene, diphosgene, triphosgene, boron trichloride, chlorine-containing phosphorus compounds: i.e., phosphorus trichloride, phosphorus pentachloride, oxyphosphoryl chloride, and chlorine-containing heterocycles: i.e., cyanuric chloride, phosphorazine. One or a combination of two or more compounds can be used as catalyst.

Suitable Lewis acids are metal halides, i.e., zinc chloride, ferric chloride, cobalt chloride, stannous chloride, aluminum chloride, titanium chloride, boron trichloride, and a mixture of two or more thereof.

In the Beckmann rearrangement as described above, activated chlorine-containing compound is used in catalytic amount, i.e., less than 10% of the molar amount of the oxime derivative, preferably in an amount of 0.1 to 5%. As with activated chlorine-containing compound, Lewis acid is also used in catalytic amount, i.e., less than 10% of the molar amount of the oxime derivative, preferably in an amount of 0.1 to 5%.

When sulfuric acid is used in the Beckmann rearrangement, the amount can be determined according to methods known in prior art for the Beckmann rearrangement.

The molar ratio of Lewis acid and activated chlorine-containing compound is 1 :0.01 to 1 : 100, preferably between 1 :0.3 to 1 : 1.5.

The amount of catalyst, reaction temperature, reaction pressure, and reaction time are related. Under certain temperature, reaction time can be shortened by increasing the amount of catalyst.

The temperature for the Beckmann rearrangement of an oxime fatty acid is not strictly limited, from room temperature to refluxing temperature. The reaction can also be performed at higher temperature under increased pressure. But if the temperature is too high, the color of rearranged products will darken, rendering post-treatment difficult.

The Beckmann rearrangement can be carried out in atmosphere, but also under inert gases, i.e., nitrogen, argon, or helium as protective atmosphere. This reaction is preferably carried out in dry air. The pressure for carrying out the rearrangement reaction is not limited, from standard normal pressure, to reduced, or increased pressure. The reactor for the Beckmann reaction is not limited. Reactors commonly used in chemical industry, and tubular reactors are suitable. The reaction can be carried out in batch, semi-continuously, or continuously.

After the Beckmann rearrangement, the product of an amide fatty acid is obtained as a mixture of two amides of the structure (IVa) and (IVb), in an almost equal molar ratio. After recovery of solvent, this mixture can be purified to obtain pure amide fatty acid before proceeding to a hydrolysis step. On the other hand, crude product of the rearrangement reaction can be directly subjected to hydrolysis, and the impurities can be removed after hydrolysis. In fact, if the purity of oxime fatty acid (III) is good, the rearrangement product is nearly pure.

The hydrolysis of the mixed amide fatty acids can be carried out with an acid. Suitable acids are sulfuric acid, hydrochloric acid, hydrobromic acid, hydroiodic acid, or nitric acid. One or a combination of two or more acids in any ratio can be used for the hydrolysis reaction. The amount of acid used in hydrolysis reaction and reaction conditions can be determined by those skilled in art. In order to increase the solubility of mixed amide fatty acids during the hydrolysis, the reaction system may be added some organic solvents. Suitable solvents are, but not limited to, methanol, ethanol, formic acid, and acetic acid.

After hydrolysis, long chain dibasic acid and short chain alkanoic acid are present in the form of carboxylic acid, while alkylamine and long chain amino acid are present as their acid salts. Preferably, water is introduced to dilute the hydrolysis suspension, and after cooling, long chain dibasic acid is crystallized and alkanoic acid is present in the form of an oil. After filtration and extensive washing first with water, then with a lower alcohol to remove alkanoic acid, long chain dibasic acid is isolated. Short chain alkanoic acid is isolated from the acidic mother liquor by a phase separation, since alkanoic acid, i.e., heptanoic acid, is insoluble in water.

The mother liquor is then neutralized with a basic agent to a pH in the range from 5.0 to 7.0 to precipitate the long chain amino acid. The precipitated long chain amino acid is isolated by means of solid-liquid separation and washed extensively with deionized water. The obtained long chain dibasic acid and amino acid can be purified by recrystallization to yield products of desired quality.

After the separation of long chain amino acid, the mother liquor is neutral and contains a neutral salt of alkylamine. In order to recover alkylamine, a basic agent is added to the mother liquor and alkylamine can be distilled from the strongly alkaline solution. A basic agent is selected from the group consisting of ammonia, ammonium hydroxide, lithium hydroxide, sodium hydroxide, potassium hydroxide, ammonium bicarbonate, ammonium carbonate, sodium bicarbonate, sodium carbonate, potassium bicarbonate, potassium carbonate, ammonium acetate, sodium acetate, potassium acetate, and a mixture of two or more thereof.

Preferable basic agent is selected from alkali salts of hydroxide. The most preferable basic agent is sodium hydroxide.

The mixed amide fatty acids of the formula (IVa) and (IVb) can also be hydrolyzed with a basic agent. The amount of base used in the reaction and reaction conditions can be determined by those skilled in art. Suitable base is selected from the group consisting of sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, barium hydroxide, and a mixture of two or more thereof. The most preferable base is sodium hydroxide.

Solvent for the hydrolysis reaction is water, or an aqueous mixture of organic solvents. Suitable organic solvents are, but not limited to, methanol, ethanol, isopropanol, tetrahydrofuran, dioxane, and a mixture of two or more thereof.

The temperature for the hydrolysis reaction is in the range of 50 °C to 200 °C, preferably from 100 °C to 150 °C. Pressure during the hydrolysis is from autogenous to increased pressure. The hydrolysis reaction can be carried out in atmosphere, but also under the protection of inert atmosphere.

The time for the hydrolysis reaction is determined by alkali hydroxide concentration, reaction temperature, from 1 to 24 hours. Preferably the reaction time is from 2 to 4 hours. If the reaction is too short, the hydrolysis is not complete. If the reaction time is too long, the volume of reactor becomes large, unnecessarily increasing capital investment.

After the hydrolysis, organic solvent if present, is removed by distillation. Alkylamine, i.e., hexylamine, is also recovered by distillation. The strongly alkaline solution contains alkali salts of long chain dibasic acid, alkanoic acid, and long chain amino acid. These three products are separated in a step-wise neutralization or acidification with an acid.

The acid is selected from the group consisting of sulfuric acid, hydrochloric acid, hydrobromic acid, nitric acid, phosphoric acid, formic acid, acetic acid, propionic acid, malic acid, glycolic acid, tartaric acid, citric acid, sulfamic acid, benzenesulfonic acid, toluenesulfonic acid, xylenesulfonic acid, methanesulfonic acid, ethanesulfonic acid, and a mixture of two or more thereof. Preferably, an inorganic acid is selected. The most preferable acid is sulfuric acid.

First, the solution is neutralized to a pH in the range of 7-8 to precipitate long chain amino acid, which is isolated by means of solid-liquid separation. The mother liquor is then adjusted to a pH in the range from 4-5 to precipitate long chain dibasic acid, which is isolated by means of solid-liquid separation. Finally, the mother liquor is acidified to a pH in the range of 1- 3 to yield alkanoic acid, which is isolated by a phase separation as alkanoic acid is insoluble in water. Optionally, the crude alkanoic acid is distilled to afford a product of desired purity.

It is particularly important to point out that long chain dibasic acid and long chain amino acid produced according to the present invention is of particularly high purity, containing no other long chain dibasic acid, nor long chain imino-dibasic acid.

EXAMPLES

The following examples illustrate the practice of this invention but are not intended to limit its scope.

EXAMPLE 1

This example relates to the production of 11-aminoundecanoic acid and dodecanedioic acid.

90 g of 12-ketostearic acid was mixed with 200 mL of water, followed by an aqueous solution of hydroxylamine sulfate (about 8%) containing 14.5 g of hydroxylamine. The mixture was vigorously stirred at 70-85 °C, while the pH of the solution was adjusted to 4.5 to 5.0 with aqueous ammonia. After reacting for 2 hours, the starting material was completely transformed to 12-oxime stearic acid as indicated by FIPLC analysis.

After the oximation reaction was complete, the mixture was settled to separate off aqueous phase and the upper oil phase was dried under vacuum. The product was dissolved in 500 mL of 98% methanesulfonic acid and heated to 140 °C for 4 hours to complete the Beckmann rearrangement. The reaction was terminated by adding 500 mL of water. The product of mixed amide fatty acids of reddish color was obtained after filtration and washing with deionized water.

The mixed amide fatty acids were dissolved in 500 mL of 10% sodium hydroxide, placed in an autoclave, and stirred at 150 °C for 4 hours under autogenous pressure. FIPLC analysis indicated that the hydrolysis proceeded to completion. The hydrolysis solution was distilled azeotropically to recover 12.8 g of hexylamine until no hexylamine came out the distillation head as indicated by a neutral pH at the head.

To the reaction solution were added 500 mL of water, 2 g of activated carbon to decolorize at 90 °C for 30 minutes. After filtration to remove activated carbon, sulfuric acid was added to the filtrate to adjust the pH to 7.5 to precipitate 11-aminoundecanoic acid. After cooling to room temperature, the precipitate was filtered, washed extensively with deionized water, and dried to yield 25.8 g of 11-aminoundecanoic acid.

The mother liquor after separating 11-aminoundecanoic acid was heated to 85 °C, acidified with sulfuric acid to a pH of 4.5, a large amount of solid precipitated. After cooling to room temperature, the solid was separated by filtration, washed with distilled water three times, methanol once. After drying, 29.4 g of dodecanedioic acid was obtained.

The mother liquor after separating dodecanedioic acid was concentrated to 200 mL and the precipitated sodium sulfate was removed by filtration. To the mother liquor was added sulfuric acid to a pH of 1.0, an oil phase was formed and separated to give 16.9 g of heptanoic acid.

EXAMPLE 2

This example relates to the production of 9-aminononanoic acid and sebacic acid.

90 g of 10-ketostearic acid was mixed with 200 mL of water, followed by an aqueous solution of hydroxylamine sulfate (about 8%) containing 12.5 g of hydroxylamine. The mixture was vigorously stirred for 2 hours at 70-80 °C, while the pH of the solution was adjusted to 4.5 to 5.0 with aqueous ammonia. HPLC analysis indicated that the starting material was completely transformed to 10-oxime stearic acid.

After aqueous phase was separated off, the oil phase was dried under vacuum and dissolved in a mixture of 100 g of trifluoroacetic acid and 100 g of acetonitrile. The solution was refluxed for 8 hours to complete the Beckmann rearrangement. After distilling off solvent, 300 mL of water was added to precipitate the product of the mixed amide fatty acids of an off-white color.

The solid material of mixed amide fatty acids was dissolved in 200 mL of acetic acid, followed by 200 mL of 30% hydrochloric acid. The solution was refluxed for 48 hours to complete the hydrolysis. To the hot solution was added 500 mL of water. After cooling to room temperature, crystalline material was obtained by filtration and washing with deionized water. After drying, 34.6 g of sebacic acid was obtained.

The mother liquor was distilled under vacuum to a residual oil, which was partitioned with water to give 21.8 g of pelargonic acid.

The mother liquor after the separation of pelargonic acid was diluted to 800 mL with water, and heated to 80 °C, slowly added a solution of sodium hydroxide to a pH of 6.5-7.0. After cooling, the precipitated solid was separated by filtration, washed with deionized water, and dried to yield 25.6 g of 9-aminononanoic acid.

The mother liquor after the separation of 9-aminononanoic acid was concentrated to 200 mL and the solid sodium chloride was removed by filtration. To the filtration mother liquor was added 20 mL of 50% sodium hydroxide, an oil layer was formed immediately. The oil layer was distilled to yield 14.6 g of octylamine.

EXAMPLE 3

This example relates to the production of 13-aminotridecanoic acid and brassylic acid.

100 g of 14-ketoarachidic acid was mixed with 200 mL of water, followed by an aqueous solution of hydroxylamine sulfate (about 8%) containing 16.5 g of hydroxylamine. The mixture was vigorously stirred for 2 hours at 75-85 °C, while the pH of the solution is adjusted to 4.5 to 5.0 with aqueous ammonia. HPLC analysis indicated that the starting material was completely transformed to 14-oxime arachidic acid.

After aqueous phase was separated off, the oil phase was dried in vacuum. The residual waxy solid was slowly added to 300 mL of 98% sulfuric acid at 100 °C. The solution was stirred at the same temperature for 2 hours to complete the Beckmann rearrangement, which was terminated by adding 800 g of ice. The product of the mixed amide fatty acids of dark color was obtained by filtration and washing with water.

The solid material was dissolved in 700 mL of 8% sodium hydroxide, placed into an autoclave and heated to 150 °C for 5 hours to complete the hydrolysis reaction. HPLC showed complete disappearance of the starting material.

The hydrolysis solution was distilled azeotropically to recover 13.4 g of hexylamine until no hexylamine came out the distillation head as indicated by a neutral pH at the head.

To the reaction solution were added 500 mL of water, 2 g of activated carbon to decolorize at 90 °C for 30 minutes. After filtration to remove activated carbon, sulfuric acid was added to the filtrate to adjust pH to 7.5. After cooling to room temperature, 13-aminotridecanoic acid crystallized. The solid was filtered, washed extensively with deionized water, and dried to yield 32.7 g of 13-aminotridecanoic acid.

The mother liquor after separating 13-aminotridecanoic acid was heated to 85 °C, acidified with sulfuric acid to a pH of 4.5, a large amount of solid precipitated. After cooling to room temperature, the solid was separated by filtration, washed with distilled water three times, methanol once. After drying, 40.6 g of brassylic acid was obtained.

The mother liquor after separating brassylic acid was concentrated to 200 mL and the precipitated sodium sulfate was removed by filtration. To the mother liquor is added sulfuric acid to a pH of 1.0, an oily phase was formed and separated to give 16.2 g of heptanoic acid.

EXAMPLE 4

This example relates to the ammoximation of 12-ketostearic acid

90 g of 12-ketostearic was dissolved in 500 mL of toluene, followed by 20 g of TS-1 catalyst. The mixture was vigorously stirred at 70 °C, while 50 mL of 27.5% hydrogen peroxide and 70 mL of 25% ammonia were added slowly at the same time. The stirring was continued for an additional 60 minutes at 75 °C after the addition of hydrogen peroxide and ammonia. HPLC analysis showed a complete conversion of starting material to 12-oxime stearic acid. Following the procedure in Example 1, 28.2 g of 11-aminoundecanoic acid and 31.9 g of dodecanedioic acid were obtained.

EXAMPLE 5

This example relates to the Beckmann rearrangement of 12-oxime stearic acid catalyzed by thionyl chloride-zinc chloride catalyst.

30 g of 12-oxime stearic acid was placed in 400 mL of acetonitrile, to which was added 0.4 g of zinc chloride and 1.2 g of thionyl chloride. The mixture was refluxed for 2 hours. HPLC analysis indicated complete conversion of the oxime stearic acid into the mixed amide fatty acid.

Acetonitrile was distilled and to the residual was added 200 mL of water. After being stirred for 30 minutes at room temperature, the mixed amide acid was recovered by filtration.

EXAMPLE 6

This example is related to the preparation of keto fatty acid by oxidizing hydroxy fatty acid in acetic acid. 30 g of 12-hydroxystearic acid was dissolved in 600 mL of 95% aqueous acetic acid and cooled on ice. To the stirred solution was added slowly 100 mL of 8.0% sodium hypochlorite, while the temperature was maintained at 5-10 °C. After the addition was completed, stirring was continued for 60 minutes. Acetic acid was recovered by distillation and 300 mL of water was added to the distillation residual. After filtration, 29.5 g of 12-ketostearic acid was obtained.

It will be understood that the foregoing examples, explanation, and drawing are for illustrative purpose only and that in view of the instant disclosure various modifications of the present invention will be self-evident to those skilled in the art and are to be included within the spirit and purview of this application and the scope of the appended claims.