JPH08217771A - Production of 3-methyltetrahydrofuran - Google Patents

Abstract

PURPOSE: To obtain the subject compound suitably useful as a raw material component, etc., for spandex fiber in good selectivity at a low cost by producing an alkyl citraconate from citraconic anhydride and an alcohol and successively catalytically hydrogenating the resultant ester. CONSTITUTION: Citraconic anhydride of formula I and an alcohol (e.g. methanol) in amounts at 1/7 ratio (molar ratio) of the citraconic anhydride/alcohol are added to a reactional tube made of stainless steel and reacted in the presence of a heat-resistant ion exchange resin as a catalyst at 120 deg.C under <=5kg/cm<2> (gauge pressure) to provide a dialkyl citraconate, which is then catalytically hydrogenated in the presence of a CuO-Cr2 O3 -MnO-BaO catalyst at 210 deg.C reactional temperature under 160kg/cm<2> reactional pressure (gauge pressure) while supplying hydrogen to afford the objective 3-methyltetrahydrofuran of formula II useful as a comonomer, etc., for polyether fibers which are raw materials for spandex fibers.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a novel method for producing 3-methyltetrahydrofuran. 3-Methyltetrahydrofuran is used as a comonomer of polyether fiber which is a raw material of spandex fiber.

2. Description of the Related Art 3-Methyltetrahydrofuran can be produced by various methods. JP-A-63-218669
According to the publication, hydrogenation of citric acid produces 3-methyltetrahydrofuran with 3- and 4-methylbutyrolactone, the selectivity of which is about 70%. According to US Pat. No. 3,956,318, it is produced by catalytic hydrogenation of epoxide in the liquid phase in the presence of a protonic acid, but the raw material epoxide is expensive. According to JP-A-2-62835, the diol obtained by catalytic hydrogenation of 4-hydroxy-butyraldehyde or 2-hydroxy-tetrahydrofuran in the presence of an aldehyde is produced by cyclization, but the starting material is expensive, and the Accompanied by raw. Further, a method by hydrogenation of methylmaleic acid or methylsuccinic acid (JP-A-49-9463) is also disclosed. However, not only is it difficult to obtain starting materials, but also the hydrogenation conditions are harsh, so that industrial implementation Is obviously difficult.

According to Japanese Patent Laid-Open No. 48-22405, 1,4
-Butenediol is hydroformylated, and after the catalyst is separated, the hydroformylated product (2-formyl-1,
(Estimated to be 4-butanediol) is catalytically hydrogenated, and the obtained 2-methyl-1,4-butanediol is cyclized to obtain 3-methyltetrahydrofuran. According to JP-A-5-117258 and JP-B-4-55179, 1,4-butynediol or 1,4-butenediol is catalytically hydrogenated in the presence of an aldehyde, and the obtained diol is cyclized to give 3-methyltetrahydrofuran. It has gained. However, 1,4 used as a raw material in these methods
-Butenediol and 1,4-butynediol are expensive because they are obtained from acetylene, and they are also accompanied by the by-product of tetrahydrofuran. JP-A-6-2199
According to No. 81, catalytic hydrogenation of itaconic acid, 3-formyl-2-methylpropionic acid or their esters produces with 2-methyl-1,4-butanediol. 2-Methylpropionic acid is expensive. As described above, the conventional method for producing 3-methyltetrahydrofuran is not industrially satisfactory because the raw material is expensive and the selectivity to 3-methyltetrahydrofuran is low.

[0003]

An object of the present invention is to provide a method for producing 3-methyltetrahydrofuran having high selectivity by using an inexpensive raw material which does not have the above-mentioned drawbacks.

[0004]

Means for Solving the Problems The inventors of the present invention have conducted extensive studies to solve the above problems, and as a result, (1) a first step for producing an alkyl ester of citraconic acid from anhydrous citraconic acid and an alcohol, and ( 2) A method for producing 3-methyltetrahydrofuran, which comprises a second step of producing 3-methyltetrahydrofuran by catalytically hydrogenating the alkyl ester obtained in the first step, was found. Chemical formula 1 schematically shows all steps of the production method of the present invention.

[0005]

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The raw material citraconic acid in the present production method is present together with maleic anhydride in the high boiling point which is usually discarded during the production of phthalic acid by the oxidation of o-xylene. That is, when distilling and refining to recover maleic anhydride, it is concentrated in the distillation bottoms and is usually discarded, but simple distillative refining yields highly pure and inexpensive citraconic anhydride. This production method has extremely high industrial significance because it can inexpensively produce 3-methyltetrahydrofuran using inexpensive raw materials.

The method of the present invention will be described in detail below. The first step for producing an alkyl ester of citraconic acid in the present invention is citraconic anhydride and an alcohol in an amount of 2 times or more moles, usually 2 to 20 times moles, preferably 3 to 8 times moles of alcohol with respect to citraconic acid anhydride. Is carried out by heating reaction in the presence or absence of a catalyst. The reaction temperature varies depending on the type of alcohol, but is usually 80-180 ° C, preferably 100-150 ° C. Above 180 ° C, ether is by-produced by dehydration of alcohol, and below 80 ° C, the reaction rate is slow and not practical. This reaction can be carried out under any of reduced pressure, normal pressure and increased pressure, but it is preferably 5 kg / cm ² (gauge pressure) or less which can be carried out by an inexpensive apparatus.

Although this reaction proceeds without using a catalyst,
A catalyst is usually used in order to perform efficiently. When a catalyst is used, the catalyst may be a known one, for example p-
Toluene sulfonic acid, methane sulfonic acid, ion exchange resins and acidic catalysts such as sulfuric acid, titanium compounds such as tetraisopropyl titanate, tetrabutyl titanate and their polymers, tin compounds such as tin oxalate and tin tetrabutyrate are used. However, considering the effect on the catalytic hydrogenation catalyst in the next step, it is generally preferable to use a catalyst that does not contain halogen and sulfur elements, and it is preferable to use a strongly acidic ion exchange resin that is easy to separate and remove the catalyst. Is.

[0009] Normally, a strongly acidic ion exchange resin has a chemical structure in which a sulfonic acid group is introduced into a three-dimensional polymer substrate composed of a copolymer of styrene and divinylbenzene, and the sulfonic acid group is linked to the benzene nucleus. There is. For this reason, there is a problem with heat resistance, and it can be used at about 150 ° C for a short time, but if stable performance is required for a long time, 100
It is desirable to keep the temperature below about ℃. The heat-resistant ion-exchange resin in which a sulfonic acid group is introduced into a polymer substrate of polysiloxy acid through an alkylene group can be stably used for up to about 200 ° C. for a long time, so that the use thereof is optimal in the present invention.

As the alcohol used in the present esterification step, an alcohol having a carbon number of 8 or less is used, and it is generally preferred to use a primary aliphatic alcohol which is easy to produce an ester. Especially, considering the production amount per unit volume, it is preferable to use methanol having a small molecular weight.

When methanol is used as the alcohol and a strongly acidic ion exchange resin is used as the catalyst, the reaction is preferably a fixed bed system. The lower the reaction pressure is, the higher the yield is. However, from the viewpoint of economy, it is preferably 5 kg / cm ² (gauge pressure) or less, particularly around normal pressure. The hydrogenation of the ester in the present invention can be carried out in a batch system, but it is more preferable to carry out the reaction in a flow system using a fixed bed catalyst, in which case the amount of the catalyst used is per unit time of the ester. It is about 0.5 to 50 times the weight of the supplied amount.

The conditions of the catalytic hydrogenation reaction, which is the second step of the present invention, are generally 20 kg / cm ² at a temperature of 100-300 ° C., although it varies depending on the kinds of the starting ester and the catalyst.
(Gauge pressure) It is carried out under the above pressure. The hydrogen gas used in this reaction does not necessarily have to be of high purity and may be a substance containing an inert component such as nitrogen or methane, which does not adversely affect the catalytic hydrogenation reaction.

The catalyst used in the hydrogenation reaction of the second step in the present invention contains copper as a main component or an element belonging to Groups 7a and 8 of the periodic table. More specifically, copper,
Cobalt, nickel, iron, rhenium, palladium, ruthenium, platinum, and rhodium are effective as the main components of the catalyst for this reaction. In addition, as a component forming the promoter, chromium,
Solid acid components containing molybdenum, manganese, barium, magnesium, and silicon and aluminum are effective. A particularly suitable catalyst for this reaction is one containing copper as a main component and generally called copper-chromite, and one containing manganese, barium or the like as a promoter component. In the case of copper-chromite which is particularly suitable as the catalyst for this reaction, the reaction temperature is preferably 150 to 280 ° C., and the reaction pressure is preferably 50 to 200 kg / cm ² (gauge pressure).

The catalyst used in the catalytic hydrogenation reaction is preferably a copper-chromium-barium (or manganese) catalyst, which is prepared, for example, by the following method. (1) Solid cupric oxide (CuO), chromic oxide (Cr ₂
O ₃ ) and manganese dioxide (MnO ₂ ) (or barium oxide (B
aO)) is mixed, and graphite etc. are added as a lubricant and mixed well, followed by molding by a general method, crushing the molded product after high temperature firing and using it in an appropriate size. (2) Ammonia water is added to an aqueous solution in which ammonium dichromate is dissolved, and cupric nitrate (or cupric sulfate, etc.) and manganese nitrate (or manganese sulfate, etc.) or barium nitrate prepared separately are added to this aqueous solution. Is added dropwise with stirring. The precipitate formed is washed with water and dried, and then calcined in the air, for example, at a temperature of around 350 ° C. The powdery fired product thus obtained can be used for the reaction as it is, but it is also possible to add an appropriate binder and a lubricant to the fired product, mix them sufficiently, and use them after molding.

The weight ratio of each component contained in the copper-chromium-barium (or manganese) catalyst obtained by the above-mentioned methods (1), (2), etc. is CuO: Cr ₂ O ₃ : MnO ₂ (or BaO ₂ ). It is preferable that they are in the range of 20-85: 15-75: 1-15, respectively. The catalyst may be in the form of powder, tablet, or the like, and the most suitable one is used. Before being used, these catalysts are subjected to an appropriate activation treatment such as treatment in a hydrogen atmosphere at about 200 ° C. and then subjected to the reaction. The amount of hydrogen used is at least 5 mol per mol of ester, preferably 7.
5-75 mol is suitable.

The reaction can be carried out without using a solvent, but preferably a solvent is used. Any solvent that does not adversely affect this reaction can be used as the solvent. Examples thereof include alcohols and hydrocarbons. The catalytic hydrogenation reaction solution is usually subjected to distillation to separate the product 3-methyltetrahydrofuran.

[0017]

【Example】

Example 1 (1) First Step (Synthesis of Citraconic Acid Ester from Citraconic Anhydride and Alcohol) A stainless steel reaction tube having an inner diameter of 10 mm and a length of 150 mm, a commercially available catalyst, DELOXAN ASP 1/9 (DEG
3 g of USSA, water content 70-80%) was charged, and a raw material of citraconic anhydride / 1-butanol = 1/3 (molar ratio) was fed to this at atmospheric pressure and 120 g at a rate of 6 g / h. The conversion rate of citraconic anhydride was 78.4%, and dibutyl citraconic acid was obtained quantitatively with respect to the reacted citraconic anhydride. The reaction solution was distilled to obtain dibutyl citraconic acid.

(2) Second step (hydrogenation of citraconic acid ester) A commercially available catalyst manufactured by Nissan Gardler G99C (weight composition CuO 36%, Cr ₂ O ₃ 32%, MnO 2.4%, BaO 2.2%, shape)
1/4 inch x 1/4 inch pellet) is divided into 1/8 size, and 20.0 g is filled in a reaction tube with an inner diameter of 15 mm and a length of 300 mm (catalyst layer height is 97 mm) and activation by ordinary hydrogen reduction is performed. After treatment (reducing at 200 ° C. or lower in a nitrogen stream containing 1-10% hydrogen), it was subjected to a reaction. Reaction temperature 210 ℃, Reaction pressure 160kg / cm
² (gauge pressure), supply amount of hydrogen is 10 l at the reaction tube outlet
/ Hr, and a mesitylene solution of 10 wt% dibutyl citraconic acid as a raw material was supplied together with hydrogen from the upper part of the reaction tube at a rate of 15 g / hr (WHSV obtained by dividing the raw material supply weight rate by the catalyst weight was 0.075 hr ⁻¹ ). As a result of analyzing the obtained reaction liquid, unreacted dibutyl citraconic acid was not observed, and the yield of 3-methyltetrahydrofuran was 94.7% based on the supplied dibutyl citraconic acid.

Example 2 Example 1 was repeated except that methanol was used in place of 1-butanol in the first step and citraconic anhydride / methanol = 1/7 (molar ratio). The conversion rate of citraconic anhydride was 96.6%, and dimethyl citraconic acid was quantitatively obtained from the reacted citraconic anhydride.

Example 3 The reaction was carried out in the same manner as in Example 2 except that the reaction pressure in the first step was 5 kg / cm ² (gauge pressure). The conversion rate of citraconic anhydride was 88%, and dimethyl citraconic acid was obtained quantitatively with respect to the reacted citraconic anhydride.

[0021]

INDUSTRIAL APPLICABILITY According to the present invention, each step proceeds with high selectivity, and since inexpensive citraconic anhydride is used as a raw material, it has an extremely high industrial value.

Claims (4)

[Claims] 1. A first step for producing an alkyl ester of citraconic acid from citraconic anhydride and an alcohol, and (2) catalytic hydrogenation of the alkyl ester obtained in the first step to produce 3-methyltetrahydrofuran. A method for producing 3-methyltetrahydrofuran, which comprises the second step. 2. The production method according to claim 1, wherein the first step is carried out using an alcohol having 1 to 8 carbon atoms in the presence of an ion exchange resin. 3. The method according to claim 2, wherein a heat resistant ion exchange resin is used as the ion exchange resin. 4. Methanol is used as alcohol, 5
The manufacturing method according to claim 2 or 3, wherein the first step is performed at a pressure of not more than kg / cm ² (gauge pressure).