Process for purification of 3,4,5,6-tetrahydrophthalic anhydride

Abstract: Disclosed is a process for purifying 3,4,5,6-tetrahydrophthalic anhydride, comprising the steps of bringing a crude 3,4,5,6-tetrahydrophthalic anhydride (comprising a 3,4,5,6-tetrahydrophthalic anhydride as the main component and an acid anhydride (a) as impurities which contains at least one of 1,2,3,6-tetrahydrophthalic anhydride, hexahydrophthalic anhydride, phthalic anhydride, and structural isomers of 3,4,5,6-tetrahydrophthalic anhydride) into contact with a medium comprising at least one of water and monohydric or polyhydric alcohols at a temperature in the range of room temperature to about 160°C so as to hydrolyze the acid anhydride (a) and/or convert it into a monoester; and separating the 3,4,5,6-tetrahydrophthalic anhydride in a solid state from the reaction mixture.

Description: The present invention relates to a process for highly purifying a 3,4,5,6-tetrahydrophthalic anhydride (hereinafter referred to as "Δ¹-THPA") which is an industrial material useful as an intermediate for preparation of insecticides, herbicides or the like. We have proposed a method for preparing Δ¹-THPA in which a 1,2,3,6-tetrahydrophthalic anhydride (hereinafter referred to as "Δ⁴-THPA") is isomerized (Japanese Examined Patent Publications Nos. 54144/1983 and 54148/1983). These methods, although commercially advantageous, give a crude Δ¹-THPA as a reaction product which contains about 1 to about 15% of Δ⁴-THPA or like structural isomers of Δ¹-THPA, hexahydrophthalic anhydride, phthalic anhydride, etc. (hereinafter generally referred to as "contaminating phthalic anhydrides"). It is very difficult to separate these contaminating phthalic anhydrides from Δ¹-THPA because of similarities therebetween in the boiling point, solubility in solvents and like physical properties. A high-purity Δ¹-THPA has not been efficiently produced on industrial basis by usual distillation, usual recrystallization or like purification procedures. An object of the present invention is to provide a process for producing a highly purified Δ¹-THPA on industrial basis from an acid anhydride mixture containing Δ¹-THPA as the main component. We conducted extensive research on the solubility of contaminating phthalic anhydrides in solvents, and the reactivity thereof with various compounds, wherein the contaminating phthalic anhydrides include unreacted Δ⁴-THPA and phthalic anhydride, hexahydrophthalic anhydride which are produced as by-products in the preparation of Δ¹-THPA by isomerization of Δ⁴-THPA. Our research revealed the following. The contaminating phthalic anhydrides are more easily hydrolyzed or converted into monoesters than Δ¹-THPA; the dicarboxylic acids obtained by the hydrolysis and the carboxyl-containing monoesters of carboxylic acids produced by the monoesterification are more soluble in water and/or an alcohol solvent than Δ¹-THPA; and Δ¹-THPA undergoes substantially no chemical change upon contact with water and/or an alcohol solvent. The present invention has been accomplished based on these novel findings. According to the present invention, there is provided a process for purifying 3,4,5,6-tetrahydrophthalic anhydride, the process comprising the steps of bringing a crude 3,4,5,6-tetrahydrophthalic anhydride (comprising 3,4,5,6-tetrahydrophthalic anhydride as the main component and an acid anhydride (a) as impurities which contains at least one of 1,2,3,6-tetrahydrophthalic anhydride, hexahydrophthalic anhydride, phthalic anhydride, and structural isomers of 3,4,5,6-tetrahydrophthalic anhydrides) into contact with a medium comprising at least one of water and monohydric or polyhydric alcohols at a temperature in the range of room temperature to 160°C so as to hydrolyze the acid anhydride (a) and/or convert it into the corresponding monoester; and separating the 3,4,5,6-tetrahydrophthalic anhydride in a solid state from the reaction mixture, the monohydric or polyhydric alcohols being selected from (i) an alcohol represented by the formula ROH (A) wherein R is an alkyl group having 1 to 22 carbon atoms, an alkenyl group having 3 to 18 carbon atoms, an aryl group, an aralkyl group or an alicyclic hydrocarbon group, (ii) an alcohol represented by the formula HO-R¹-OH (B) wherein R¹ is a group (wherein H ○ is an alicyclic hydrocarbon group having 6 carbon atoms), a group (wherein D is an alkylene group having 2 or 3 carbon atoms, and m is an integer of 0, 1 or 2), (iii) an alcohol represented by the formula wherein R² is a hydrogen atom or a group (wherein p is an integer of 1 or 2), and (iv) a mixture of such alcohols (i) to (iii). To be brief, the present invention has the feature that a crude Δ¹-THPA is purified by contacting the crude Δ¹-THPA as the starting material with water and/or said alcohol to convert the contaminating phthalic anhydrides into the corresponding dicarboxylic acids and/or monoesters and separating Δ¹-THPA therefrom. In other words, the process of the invention is characterized in that a crude Δ¹-THPA is purified by converting the contaminating acid anhydrides in the crude Δ¹-THPA into the corresponding dicarboxylic acids or monoesters which are soluble in water and/or the foregoing alcohol solvent, and removing the dicarboxylic acids and monoesters as dissolved in the solvent. The amount of the contaminating phthalic anhydrides to be acceptable in the crude Δ¹-THPA as the starting material is not specifically limited insofar as the intended effect is obtained. Usually the amount is about 1 to about 20% by weight, preferably about 3 to about 15% by weight. The kind of alcohols to be used in the invention are capable of forming the corresponding monoester by the reaction with the contaminating phthalic anhydrides and are represented by the formula (A), (B) or (C). These alcohols are usable singly, or at least two of them can be used in mixture. The monohydric or polyhydric alcohols include (i) an alcohol represented by the formula ROH (A) wherein R is an alkyl group having 1 to 22 carbon atoms, an alkenyl group having 3 to 18 carbon atoms, an aryl group, an aralkyl group or an alicyclic hydrocarbon group, (ii) an alcohol represented by the formula HO-R¹-OH (B) wherein R¹ is a group (wherein H ○ is an alicyclic hydrocarbon group having 6 carbon atoms), a group (wherein D is an alkylene group having 2 or 3 carbon atoms, and m is an integer of 0, 1 or 2), (iii) an alcohol represented by the formula wherein R² is a hydrogen atom or a group (wherein p is an integer of 1 or 2), and (iv) a mixture of such alcohols (i) to (iii). Examples of the alcohols of the formula (A) are as follows: (1) straight- or branched-chain aliphatic saturated or unsaturated monohydric alcohols having 1 to 22 carbon atoms, particularly aliphatic C₁-C₂₂ saturated or C₃-C₁₈ unsaturated monohydric alcohols, such as those containing groups including methyl, ethyl, propyl, butyl, isobutyl, amyl, hexyl, heptyl, octyl, 2-ethylhexyl, isooctyl, isononyl, decyl, isodecyl, undecyl, dodecyl, tridecyl, tetradecyl, hexadecyl, octadecyl, docosyl, allyl, octadecenyl, etc.; (2) benzyl alcohol, phenethyl alcohol and like aralkyl alcohols; and (3) cyclopentyl alcohol, cyclohexyl alcohol and like alicyclic monohydric alcohols. Examples of the alcohols of the formula (B) are cyclohexanediol, cyclohexanedimethanol, ethylene glycol, diethylene glycol, triethylene glycol and like polyethyelene glycols, propylene glycol, dipropylene glycol, tripropylene glycol and like polypropylene glycols. Examples of the alcohols of the formula (C) are aliphatic polyhydric alcohols such as glycerin, diglycerin, triglycerin and like polyglycerins. The water and/or the alcohol may be used in an amount effective to hydrolyze the contaminating phthalic anhydrides or to convert the contaminating phthalic anhydrides into the monoesters thereof. The amount is usually 0.1 to 50 moles, preferably 0.5 to 20 moles, per mole of the crude Δ¹-THPA (in terms of the mean molecular weight as calculated from the neutralization value). The process of the invention can be variously conducted. According to one preferred embodiment of the invention, a crude Δ¹-THPA and the above-specified amount of the solvent are mixed together and stirred with heating to dissolve the crude Δ¹-THPA in the solvent and to thereby effect the reaction and the reaction mixture is cooled, and the precipitated crystals are separated and dried under reduced pressure (hereinafter referred to as "method 1"). The heating in the method 1 is usually conducted at a temperature of 50 to 160°C, preferably 60 to 140°C, more preferably 70 to 140°C. If a temperature higher than 160°C is employed, the monoester is further esterified into a diester which is less soluble in water and/or alcohol solvents, and which consequently remains as mixed with Δ¹-THPA. If a temperature lower than 50°C is employed, the hydrolysis of contaminating phthalic anhydrides or the reaction thereof for conversion into monoesters slowly proceeds. When the crude Δ¹-THPA is brought into contact with the water and/or the alcohol solvent at a temperature of 50 to 160°C, substantially the entire amount of the contaminating phthalic anhydrides is hydrolyzed and/or converted into monoesters in about 5 to about 60 minutes, and the thus produced dicarboxylic acids and/or monoesters are dissolved in the water and/or the alcohol solvent. The Δ¹-THPA in the crude Δ¹-THPA is dissolved in the water and/or the alcohol solvent without chemical change. When the reaction mixture is subsequently cooled to a temperature of, e.g. 10 to 50 °C, the dicarboxylic acids and/or monoesters remain dissolved in the solvent while the Δ¹-THPA is precipitated as crystals. The crystals are separated by usual separating means such as filtration or the like and dried under reduced pressure, giving the desired highly purified Δ¹-THPA. According to another preferred embodiment of the invention, the process of the invention can be effected as follows. A crude Δ¹-THPA is mixed with the above-specified amount of water and/or an alcohol solvent with stirring for a period of time and at a temperature such that the Δ¹-THPA is not dissolved. Subsequently the reaction mixture is filtered, giving a highly purified Δ¹-THPA. This method is hereinafter referred to as "method 2". The temperature to be employed in the method 2 is in the range of room temperature to 70°C, preferably 40 to 60°C, and the period of time may range from 10 to 120 minutes under this temperature condition. This method 2 is characterized in that substantially all the Δ¹-THPA in the crude Δ¹-THPA remains as a solid and the contaminating phthalic anhydrides alone are hydrolyzed or converted into their monoesters. At a higher temperature than 70°C which exceeds the melting point of Δ¹-THPA, the Δ¹-THPA can not be retained in a solid state. On the other hand, at a temperature lower than room temperature, it is difficult to hydrolyze the contaminating phthalic anhydrides as impurities or to convert them into monoesters. In the purification of method 2, a crude Δ¹-THPA in the form of granules or powder is preferably used to efficiently remove the contaminating phthalic anhydrides as impurities. When stirred in water and/or alcohol solvent under the foregoing temperature conditions for about 10 to about 120 minutes such that the Δ¹-THPA can be retained in a solid state, the contaminating phthalic anhydrides present as impurities in the solid crude Δ¹-THPA are hydrolyzed or converted into monoesters, and the resulting hydrolyzates and monoesters are dissolved in water and/or alcohol solvent. In the meantime, substantially the whole of Δ¹-THPA remains as a solid without undergoing dissolution nor chemical change. Subsequently the reaction mixture is cooled to approximately room temperature when so required and filtered, and the obtained Δ¹-THPA is dried at atmospheric or reduced pressure, whereby a highly purified Δ¹-THPA can be obtained in a high yield. To improve the intended effect of the invention, an organic solvent which is unreactive with acid anhydrides can be used if so desired in the method 1 and method 2. Stated more specifically, the yield of Δ¹-THPA can be increased by use of such organic solvent which enables control of the solubility of dicarboxylic acids produced by the hydrolysis and/or monoesters of carboxylic acids produced by the monoesterification. Especially, when the water and/or alcohol is used in a small amount, the use of the organic solvent can increase the solubility of the dicarboxylic acids and/or monoesters. Examples of useful organic solvents which are unreactive with acid anydrides are given below in (I) to (IV). They are usable singly, or at least two of them can be used in mixture. (I) Hydrocarbons having 6 to 16 carbon atoms such as aliphatic hydrocarbons, alicyclic hydrocarbons and aromatic hydrocarbons, such as hexane, heptane, octane, decane, dodecane, cyclohexane, decalin, tetralin, toluene, xylene, ethyl benzene, butyl benzene, and mixed hydrocarbons produced in petroleum refining. (II) Chain or cyclic ethers such as diethyl ether, diisopropyl ether, dibutyl ether, tetrahydrofuran, dioxane, etc. (III) Chain or cyclic ketones such as acetone, methyl ethyl ketone, diethyl ketone, methyl isobutyl ketone, cyclopentanone, cyclohexanone, etc. (IV) Other unreactive organic solvents such as acetonitrile and like nitriles, ethyl acetate, propyl acetate, butyl acetate and like esters, ethyl cellosolve, butyl cellosolve, and like polyethers. The amount of the unreactive organic solvent to be used is not specifically limited. Yet the amount should not be excessive since an excessive amount tends to decrease the amount of obtained high-purity Δ¹-THPA. Thus the amount is usually 0 to 500% by weight, preferably 0 to about 200% by weight, based on the crude Δ¹-THPA. When required, the Δ¹-THPA in the reaction system can be decolorized using active carbon or like adsorbent in the method 1. This step renders Δ¹-THPA almost colorless. Useful active carbon can be any of those commonly used. Active carbon is added in an amount of about 0.2 to about 10% by weight based on the weight of the starting crude Δ¹-THPA. After dissolution of the starting materials in the solvent, the decolorization can be easily done by stirring the solution for about 10 to about 120 minutes and filtering the reaction mixture. Other adsorbents such as activated clay and acid clay are also as effective as active carbon. The present invention will be described below in greater detail with reference to the following examples and comparison examples. Example 1 A 1-liter four-necked flask equipped with a stirrer, a condenser, a thermometer and a nitrogen gas inlet was charged under nitrogen atmosphere with 300 g of isopropyl alcohol and 152 g of a crude Δ¹-THPA consisting of 90% by weight of Δ¹-THPA, 3% by weight of hexahydrophthalic anhydride, 1% by weight of phthalic anhydride, 2% by weight of a structural isomer of Δ¹-THPA and 4% by weight of other components (as assayed by GC-12A, trademark for a gas chromatography manufactured by Shimadzu Corp., the same hereinafter). The crude Δ¹-THPA was dissolved in the solvent with stirring and heating. The solution was stirred at 80°C for 30 minutes and then cooled to 25°C. The solution was filtered and dried under reduced pressure at 60°C at a pressure of 5 to 6 mmHg until no weight change occurred. The above procedure gave 132 g of Δ¹-THPA having a purity of 99.9% by weight in a yield of 97%. Examples 2 to 6 The same procedure as in Example 1 was conducted except that the amount of crude Δ¹-THPA, the kind of the solvent and the temperature were varied as shown in Table 1. Table 1 below shows the results. Example 7 The same procedure as in Example 1 was repeated although in a manner different in the following. To 300 g of isopropyl alcohol was added 152 g of powdery crude Δ¹-THPA consisting of 90% by weight of Δ¹-THPA, 3% by weight of hexahydrophthalic anhydride, 1% by weight of phthalic anhydride, 2% by weight of a structural isomer of Δ¹-THPA and 4% by weight of other components. The mixture was heated to 60°C and stirred for 10 minutes. The reaction product was filtered after cooling. The results are shown in Table 1. Example 8 The same procedure as in Example 7 was conducted with the exception of using 150 g of water and 150 g of isopropyl alcohol. Table 1 shows the results. Comparison Examples 1 and 2 The same procedure as in Example 1 was followed with the exception of using a solvent which is unreactive with acid anhydrides. Table 1 shows the results.

Claims: A process for purifying 3,4,5,6-tetrahydrophthalic anhydride, the process comprising the steps of bringing a crude 3,4,5,6-tetrahydrophthalic anhydride (comprising a 3,4,5,6-tetrahydrophthalic anhydride as the main component and an acid anhydride (a) as impurities which contains at least one of 1,2,3,6-tetrahydrophthalic anhydride, hexahydrophthalic anhydride, phthalic anhydride, and structural isomers of 3,4,5,6-tetrahydrophthalic anhydride) into contact with a medium comprising at least one of water and monohydric or polyhydric alcohols at a temperature in the range of room temperature to 160°C so as to hydrolyze the acid anhydride (a) and/or convert it into a monoester; and separating the 3,4,5,6-tetrahydrophthalic anhydride in a solid state from the reaction mixture, the monohydric or polyhydric alcohols being selected from (i) an alcohol represented by the formula ROH (A) wherein R is an alkyl group having 1 to 22 carbon atoms, an alkenyl group having 3 to 18 carbon atoms, an aryl group, an aralkyl group or an alicyclic hydrocarbon group, (ii) an alcohol represented by the formula HO-R¹-OH (B) wherein R¹ is a group (wherein H ○ is an alicyclic hydrocarbon group having 6 carbon atoms), a group (wherein D is an alkylene group having 2 or 3 carbon atoms, and m is an integer of 0, 1 or 2), (iii) an alcohol represented by the formula wherein R² is a hydrogen atom or a group (wherein p is an integer of 1 or 2), and (iv) a mixture of such alcohols (i) to (iii). A process according to claim 1 wherein the monohydric or polyhydric alcohol is at least one alcohol selected from the group consisting of straight- or branched-chain aliphatic saturated or unsaturated monohydric alcohols having 1 to 22 carbon atoms, benzyl alcohol, phenethyl alcohol, cyclopentyl alcohol, cyclohexyl alcohol, cyclohexanediol, cyclohexanedimethanol, ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, glycerin, diglycerin and triglycerin. A process according to claim 1 or 2, wherein 0.1 to 50 moles of the water and/or the alcohol is used per mole of the crude 3,4,5,6-tetrahydrophthalic anhydride in terms of the mean molecular weight as calculated from the neutralization value. A process according to claim 1 or 2, wherein 0.5 to 20 moles of the water and/or the alcohol is used per mole of the crude 3,4,5,6-tetrahydrophthalic anhydride in terms of the mean molecular weight as calculated from the neutralization value. A process according to any one of claims 1 to 4 which comprises the steps of bringing the crude 3,4,5,6-tetrahydrophthalic anhydride into contact with the medium comprising at least one of water and monohydric or polyhydric alcohols at a temperature of 50 to 160°C so as to hydrolyze the acid anhydride (a) and/or convert it into a monoester, dissolving the obtained hydrolyzate and/or the monoester and the 3,4,5,6-tetrahydrophthalic anhydride in the solvent, cooling the solution to precipitate only the 3,4,5,6-tetrahydrophthalic anhydride as crystals, and separating the crystals from the solution. A process according to any one of claims 1 to 4 which comprises the steps of bringing the crude 3,4,5,6-tetrahydrophthalic anhydride into contact with the medium comprising at least one of water and monohydric or polyhydric alcohols at a temperature of room temperature to 70°C so as to hydrolyze the acid anhydride (a) and/or convert it into a monoester, dissolving the obtained hydrolyzate and/or the monoester in the solvent, and separating the 3,4,5,6-tetrahydrophthalic anhydride remaining as a solid. A process according to any one of claims 1 to 6 wherein the medium further contains an organic solvent which is unreactive with acid anhydrides. A process according to claim 7 wherein the organic solvent is at least one solvent selected from the group consisting of hydrocarbons having 6 to 16 carbon atoms, chain or cyclic ethers, chain or cyclic ketones, nitriles, esters and polyethers. A process according to claim 7 or 8 wherein the organic solvent is used in an amount of 500% by weight or less based on the crude 3,4,5,6-tetrahydrophthalic anhydride.

Inventors: NISHIO KENJI, TANI SHOJI, NISHIO, KENJI, TANI, SHOJI
Applicants: NEW JAPAN CHEM CO LTD, NEW JAPAN CHEMICAL CO.,LTD.
Application year: 1990
Main classification: C07C61
IPC codes: C07C51, C07D209, C07D307