JP2001151715A - Method for producing alcohols - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing an alcohol by hydrogenating a carboxylic acid, by which the alcohol can efficiently and highly purely be recovered from the reaction mixture. SOLUTION: This method for producing the alcohol by hydrogenating a raw material compound consisting mainly of a carboxylic acid in the presence of a catalyst to produce the reaction mixture containing the alcohol, and then subjecting the reaction mixture to a distillation separation to recover the alcohol, is characterized by distilling the alcohol, while maintaining the content of the organic carboxylic acid to <=0.5 wt.% in the distillation tower.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a method for producing alcohols. More specifically, the present invention relates to a method for efficiently obtaining alcohols of interest from a hydrogenation reaction mixture when a carboxylic acid is subjected to a hydrogenation reaction in the presence of a hydrogenation catalyst to produce an alcohol, for example, a method for obtaining cyclohexanedicarboxylic acid from cyclohexanedicarboxylic acid. It is intended to provide a method for producing 1,6-hexanediol from methanol and adipic acid.

[0002]

2. Description of the Related Art The production of alcohols from carboxylic acids has long been widely practiced industrially. For example, monohydric aliphatic alcohols containing 6 to 11 carbon atoms are used as raw materials for plasticizer esters, and higher alcohols containing about 11 or more carbon atoms are mainly used in the production of synthetic detergents. is there. Diols produced from dicarboxylic acids having 4 to 10 carbon atoms are used in large amounts as polyester-based synthetic fibers, synthetic resins, and paints. In the prior art described in Japanese Patent Publication No. 27281272, Japanese Patent Publication No. Sho 53-33567, or Japanese Patent Publication No. Hei 8-510686, a fatty acid is once converted into a fatty acid ester and then converted to a target product by a hydrogenation reaction. A certain aliphatic alcohol is produced.

[0003]

However, in the prior art as described above, there is no hydrogenation catalyst having excellent acid resistance to the carboxylic acid used as a raw material. Was. In order to solve the problems of these hydrogenation catalysts, the present inventors have proposed Ru and S that can directly hydrogenate carboxylic acid.
and proposed a solid catalyst containing n (Japanese Patent Laid-Open No. 10-30604).
7, Japanese Patent Application No. 10-174386). Although these catalysts show excellent performance for the hydrogenation reaction of carboxylic acid, when unreacted carboxylic acid remains, alcohol is obtained by distillation separation with carboxylic acid and produced alcohol. The esterification reaction proceeds, and the yield of alcohols decreases. Further, when the boiling points of the unreacted carboxylic acid or by-produced organic acid and the alcohol as the target compound are close to each other, it is difficult to obtain high-purity alcohols. Furthermore, when a dicarboxylic acid is used as the carboxylic acid, there is a problem that an oligomer of an ester is generated, and there is a concern that the bottom pipe of the distillation column may be blocked. That is, it is necessary to remove organic carboxylic acids including unreacted carboxylic acids as much as possible before distilling and separating alcohols as objective substances.

[0004]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to solve the above problems, and as a result, have found that hydrogenation containing alcohols obtained by hydrogenating a starting compound mainly composed of carboxylic acid. In the method of recovering alcohols from the reaction mixture by distillation, the present inventors have found that the amount of organic carboxylic acid remaining in the distillation column is involved in side reactions and affects the purity of the target alcohol. did.

[0005] That is, the gist of the present invention is that a starting compound mainly composed of carboxylic acid is subjected to a hydrogenation reaction in the presence of a catalyst to produce a reaction mixture containing alcohols, which is separated by distillation from the reaction mixture. The method for producing alcohols by recovering alcohols is characterized in that distillation is performed while maintaining the amount of organic carboxylic acid in the distillation column at 0.5 wt% or less.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the present invention will be described below. (Raw material compound) The compound mainly containing a carboxylic acid, which is a raw material compound in the present invention, is usually 70% by weight of an aliphatic or alicyclic saturated, unsaturated or polyunsaturated carboxylic acid.
%, Preferably 80% by weight or more. The carboxylic acid is, for example, an aliphatic or cycloaliphatic alkyl, alkenyl, or hydroxyalkenyl carboxylic acid containing 1 to 26 carbon atoms, preferably 4 to 22 carbon atoms, wherein Means more than one compound. Further, ester compounds of these carboxylic acids and aliphatic alcohols may be mixed in the raw material compounds. As used herein, the aliphatic alcohol may be an alcohol obtained by a hydrogenation reaction of a fatty acid, or a lower alcohol such as methanol, ethanol, normal propanol, isopropanol, normal butanol, and isobutanol. Preferred carboxylic acid esters are carboxylic acid methyl esters.

Examples of the carboxylic acid of the present invention include monocarboxylic acids such as caproic acid, decanoic acid, dodecanoic acid, pentadecanoic acid, oleic acid, hydroxyoctadecenoic acid and hydroxycaproic acid, coconut oil, rapeseed oil, palm oil, A mixture of fatty acids obtained by the hydrolysis of naturally occurring triglycerides such as lard oil, maleic acid, succinic acid, glutaric acid, adipic acid, cyclohexanedicarboxylic acid, cyclohexanetricarboxylic acid, 1,
Examples thereof include polycarboxylic acids such as 2,4-butanetricarboxylic acid. In the present invention, it is preferable to use a dicarboxylic acid or an ester thereof as a raw material compound in that the effect of suppressing oligomerization is remarkable, and among them, maleic acid, succinic acid, adipic acid and 1,4-cyclohexane are particularly preferable. It is more preferable to use a raw material compound selected from dicarboxylic acids and esters thereof, and particularly preferable is adipic acid.

In the present invention, the above-mentioned raw material compound is subjected to a hydrogenation reaction in the presence of a catalyst to produce a reaction mixture containing alcohols. (Hydrogenation catalyst) As the hydrogenation catalyst, for example, a catalyst containing at least one kind of Group VIII element as an active component can be used, and among them, a catalyst containing Ru, particularly Ru and Sn as an active component can be used. preferable. When Pt coexists in addition to the Ru and Sn components, an improvement in the catalytic activity is observed. These active ingredients are preferably used by being supported on a porous carrier. Activated carbon, diatomaceous earth,
Many porous carriers such as alumina, silica and titania can be used alone or in combination of two or more. Among them, activated carbon is particularly preferable.

The method of supporting the metal component as the catalytically active component on the carrier is not particularly limited, and any of the methods usually employed in the preparation of supported catalysts, such as an immersion method, an ion exchange method, and a sol-gel method, can be applied. It is possible. Among them, the immersion method is adopted as a particularly simple method. When the immersion method is used, for example, a solvent capable of dissolving the raw material compound of the metal to be supported, for example, is dissolved in water to form an aqueous solution of the metal compound, and this solution is immersed in a separately prepared porous carrier to form a catalyst component on the carrier. Is carried. There is no particular limitation on the order in which the metal components are supported on the carrier.
The effect of the present invention can be achieved by simultaneously loading each component, loading each component individually one by one, or loading a plurality of components in combination. However, among them, particularly, first, Ru and Sn are first supported, dried and reduced, and then, if necessary, Pt is added to the carrier to further enhance the effect of the present invention.

After the metal component solution is immersed and supported on the carrier (each time when immersed and supported over a plurality of times),
Drying is usually performed. Dry at a temperature of 200 ° C or less
Alternatively, the drying is performed while passing a dry gas such as air or an inert gas. After that, firing and reduction are performed as necessary. When the calcination treatment is performed, the calcination is usually performed at a temperature in the range of 100 to 600 ° C. by passing an inert gas such as air or nitrogen. In the case of performing the reduction treatment, a known liquid-phase reduction method or a gas-phase reduction method is employed. In the case of the gas-phase reduction method, a temperature range of usually 100 to 600 ° C., preferably a temperature range of 200 to 500 ° C. Is selected.
As the reducing gas, hydrogen, hydrogen diluted with an inert gas, methanol, or the like is appropriately selected. The reduced catalyst can be stored after being passivated with diluted oxygen from the viewpoint of easy handling. The loadings of Ru and Sn are in the range of 0.5 to 50% by weight, preferably 1 to 20% by weight, respectively, based on the metal and the carrier. In addition, it is preferable that Pt is usually used in an amount of 0.1 to 5 times by weight with respect to Ru, from the viewpoint of improving the activity. The noble metal components of Ru and Pt and S
As the raw material compound of n, mineral salts of such metals such as nitric acid, sulfuric acid, and hydrochloric acid are generally used, and organic acid salts such as acetic acid, hydroxides, oxides, and generally known organic compounds are used. Metal compounds and complex salts can also be used.

(Hydrogenation reaction) Regarding the reaction conditions for the hydrogenation reaction, the temperature is usually 50 to 350 ° C, preferably 100 to 250 ° C.
° C, reaction pressure is usually 0.1-30MPa, preferably 1-25MPa.
a is adopted. The hydrogen used in the hydrogenation reaction does not need to be pure hydrogen, and may be hydrogen diluted with an inert gas such as nitrogen, helium, argon, or carbon dioxide. The reaction may be performed in a batch system or a continuous system, and the reactor may be of any type such as a stirred suspension bed system, a fixed bed system, and a fluidized bed system. Usually, it is industrially advantageous to carry out the reaction continuously using a fixed bed.

[0012] The hydrogenation reaction may be carried out without a solvent or, if necessary, a reaction solvent which does not adversely affect the reaction may be used. For example, water, alcohols such as methanol and ethanol, ethers such as tetrahydrofuran and dioxane, and hydrocarbons such as hexane and decalin can be exemplified. In the hydrogenation reaction of carboxylic acid, water is always produced as a by-product together with the corresponding alcohol, and thus water is particularly preferable among these solvents. There is no particular limitation on the concentration of the starting compound, and it can be appropriately determined in consideration of the reaction rate, heat of reaction, and the subsequent separation step. Usually, the concentration of the starting compound ranges from 5% by weight to 90% by weight, preferably 2% by weight.
A range of 0% to 50% by weight is employed. In particular, when a low-grade material such as a SUS material is used as the material of the reactor, since the material corrosion is reduced as the carboxylic acid concentration is lower, it is preferable to use a raw material concentration of 30% by weight or less, preferably 20% by weight or less. preferable.

The material of the apparatus used in the present invention includes not only the hydrogenation reaction apparatus but also all the steps before and after the apparatus, for example, the apparatus used in the alcohol recovery and purification steps such as a raw material dissolving tank and a distillation column. There is no particular limitation as long as the material can prevent corrosion, but the poisoning of the catalyst due to the eluted material can be avoided by forming the liquid contact portion of the portion where corrosion is particularly likely to occur with a nickel-based alloy. The nickel-based alloy is an alloy containing nickel in an amount of 45% by weight or more, such as a nickel-molybdenum alloy known as Hastelloy, a nickel-molybdenum-chromium alloy, and a nickel-copper alloy known as Monel steel. And the like.

The continuous hydrogenation reaction of adipic acid will be specifically described below with reference to examples, but other raw material compounds other than adipic acid can be similarly applied. [Summary of Reaction Format] The reaction format is arbitrary, but for example, when adipic acid is used as a starting compound, the following reaction format can be used. A fixed bed type reactor is provided with an immobilized catalyst, and water, adipic acid and a hydrogen-containing gas are continuously supplied to the reactor to simultaneously generate 1, 6
-Continuously remove the reaction mixture containing hexanediol and unreacted adipic acid. The removed reaction mixture is separated into gases in a gas separation tower, and the separated gases are recycled to the reactor. On the other hand, the reaction mixture taken out is led to a distillation step which is a feature of the present invention.

[Raw Material Supply Method] At the start of the reaction At least the gas containing the hydrogenation catalyst, water, adipic acid, and hydrogen is present in the reactor after the start of the reaction, but the order in which these raw materials are added during the initial filling stage of the reactor is particularly limited. There is no. However, in order to maintain the performance stability of the catalyst, it is preferable to avoid contact between adipic acid and the hydrogenation catalyst in the absence of hydrogen. It is preferable to use the following procedure as a specific order of addition. After putting the hydrogenation catalyst into the reactor, supply hydrogen containing gas,
Next, the temperature is raised to a predetermined reaction temperature while supplying water.
After reaching the predetermined temperature, adipic acid is supplied to start the reaction.

2. During the continuation of the reaction As the hydrogenation reaction proceeds, the amount of adipic acid and hydrogen in the reactor decreases. Therefore, it is preferable to carry out the reaction continuously while replenishing these. As a method of supplying these raw materials to the reactor, there is a method of (2-1): a method of continuously supplying the raw materials to the reactor without interruption (2-2): a method of supplying the raw materials intermittently at a certain interval time. In order to stabilize the reaction, it is preferable to use the method (2-1). The supply molar ratio of hydrogen to adipic acid is 4 to 5000, preferably 10 to 500, and more preferably 12 to 100. The feed rate of the raw material can be appropriately determined depending on the performance of the catalyst, the amount of unreacted material after separation of the target product circulated to the reactor, and the like. Generally, the feed rate of adipic acid is 0.1 to 1000 kg / (kg
-cat · hr), preferably 0.2 to 50 kg / (kg-cat · h)
r) The supply rate of hydrogen is 50 to 5 in GHSV.
000 / hr, preferably in the range of 100 to 2000 / hr.

As described above, the hydrogenation reaction solution from which the gas has been separated by the gas-liquid separation column is supplied to the distillation column as it is, and if unreacted carboxylic acid or the like remains, the hydrogenation reaction solution such as esterification is removed. There is a problem that the reaction proceeds and the yield of alcohols decreases, or a high-boiling oligomer of an ester is formed, which may cause clogging of the bottom piping of the distillation column. Further, when the boiling points of the unreacted carboxylic acid or by-produced organic acid and the alcohol as the target compound are close to each other, it is difficult to obtain high-purity alcohol. In the present invention, when distilling and separating the hydrogenation reaction mixture after gas separation in the gas-liquid separation column, distillation is performed while maintaining the amount of organic carboxylic acid in the distillation column at 0.5 wt% or less. In addition, it is possible to suppress the side reaction caused by the organic carboxylic acid as described above, and it is possible to obtain alcohols with high purity. Here, the organic carboxylic acid is
Unreacted starting carboxylic acid and organic carboxylic acid by-produced by hydrogenation reaction are exemplified. Examples of a method for controlling the amount of the organic carboxylic acid in the distillation column include a method for supplying an alkaline compound in the distillation column, a method for supplying a reaction mixture in which an alkaline compound is added in advance to the distillation column, and the like.
According to such a method, unreacted carboxylic acid and by-produced organic carboxylic acid in the reaction mixture are converted into alkali salts, and thus the above-described problem in the distillation step can be avoided.

As the alkaline compound, any compound can be used as long as it is a compound exhibiting alkalinity as an aqueous solution. Specifically, ammonia or LiO
Alkali salts such as H, NaOH, KOH, calcium hydroxide, sodium carbonate, NaOMe, etc., alkaline earth metal salts or organic amines such as triethylamine, tributylamine and pyridine can be used if necessary. Among them, ammonia water, NaOH or KOH is most preferable. It is preferable to add an alkaline compound having an alkali equivalent of at least the sum of the carboxylic acid groups calculated from the organic carboxylic acid remaining in the hydrogenated product. Specifically, 1 to 1000 equivalents, preferably 1 to 100 equivalents, of the alkaline compound is used based on the total acid value. In the present invention,
The alkaline compound may be supplied into the distillation column separately from the hydrogenation reaction mixture, or the hydrogenation reaction mixture to which the alkaline compound has been added in advance may be supplied to the subsequent distillation step.

(Distillation step) The distillation operation used to remove the alcohol as the target product may be any one of simple distillation and continuous distillation, and the hydrogenation reaction mixture is subjected to distillation by a reaction solvent such as water. And crude alcohol. The solvent such as water separated by the distillation operation is circulated to the hydrogenation reaction zone and reused. On the other hand, the crude alcohol is obtained as a product by further ordinary purification such as distillation. Part of the alkaline compound is removed from the bottom of the distillation column together with a high-boiling by-product of the hydrogenation reaction product as an alkaline salt with an organic acid.

[0020]

EXAMPLES Next, the method of the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to the following Examples as long as it does not exceed the gist.

Example 1 1.5 mm φ × 3 m in a 1-inch φ × 1 m fixed bed reactor
95 g of a catalyst composed of Ru, Pt and Sn supported on m-shaped activated carbon, a reaction pressure of 12 MPa and a reaction temperature of 2
Under a condition of 50 ° C., a hydrogenation reaction was carried out by supplying a 20 wt% aqueous solution of cyclohexanedicarboxylic acid at a rate of 250 g / h. After gas-liquid separation, the liquid composition of the reaction mixture taken out is 1
3.37 wt% cyclohexanedimethanol (CHD
M), 0.80 wt% cyclohexanehydroxymethylcarboxylic acid (CHMA) and 0.46 wt% cyclohexanedicarboxylic acid (CHDA). To this reaction mixture, NaOH equivalent to 1.2 equivalents of the remaining carboxylic acid was added and then supplied to a distillation column. At this time, no organic carboxylic acid exists in the distillation column. After distilling off water by simple distillation under the conditions of a bottom temperature of 51 to 107 ° C. and a distilling pressure of 100 mmHg, the bottom temperature is set to 159 to 206 ° C., and a distilling pressure of 9 mmHg is set for CHD.
M was distilled off. The recovery of CHDM was 89.3 wt% and the purity was 99.8 wt%. CHMA and CHDA all remained in the bottom, and these compounds could not be detected in the distillate.

Comparative Example 1 Using the same hydrogenation reaction solution as in Example 1 except that NaOH was not added, distillation was carried out under the same operating conditions. As a result, the recovery rate of the distilled CHDM was 92.5.
wt%, but the CHDM purity was 98.1 wt%. 1.88 wt% CHMA and 0.68 wt% CHDA were contaminated in the CHDM distillate.

Example 2 1.5 mmφ × 3 in a 1-inch φ × 1 m fixed bed reactor
95 g of a catalyst composed of Ru, Pt and Sn supported on activated carbon having a thickness of 20 mm and a reaction pressure of 12 MPa and a reaction temperature of 250 ° C., and a 20 wt% aqueous solution of adipic acid was added to 250 g of the catalyst.
The hydrogenation reaction was performed by feeding at a rate of g / h. After gas-liquid separation, the liquid composition of the reaction mixture taken out was 13.77% by weight of 1,6-hexanediol (1,6-HD), 1.29% by weight.
wt% oxycaproic acid (OCA) and 0.19 w
It contained t% pentanol, 0.35 wt% pentanol. The liquid composition of this hydrogenation reaction solution after removing water at a degree of vacuum of 100 mmHg and a kettle temperature of 50 to 128 ° C. is 86.39 wt% of 1,6-HD, 0.47 wt%.
Water, 0.53% adipic acid and 12.61 wt% OCA. To the reaction mixture, an equivalent amount of NaOH to the carboxylic acid group contained in the reaction mixture was added, and distillation under reduced pressure was performed under the following conditions. At this time, no organic carboxylic acid is present in the vacuum distillation. Bottom temperature 14
1,6-H under the conditions of 7 to 174 ° C and a degree of vacuum of 10 mmHg
D was distilled at 144 ° C. The recovery of 1,6-HD was 92.5% as a consistent recovery from the hydrogenation reaction, and the purity was 100%. All the OCA and adipic acid remained in the bottoms, and these compounds could not be detected in the distillate.

Comparative Example 2 The same operation was performed as in Example 2, except that NaOH was not added when the reaction mixture from which water had been removed was distilled under reduced pressure. As a result, the liquid composition of the distillate was 98.44 wt.
% 1,6-HD and 1.56 wt% OCA. The consistent recovery of 1,6-HD from the hydrogenation reaction was 96.4%, but the purity was 98.4%.

[0025]

According to the method of the present invention, a reaction mixture containing an alcohol obtained by hydrogenating a carboxylic acid can be obtained by
It is possible to efficiently obtain the target alcohols with high purity, and a side reaction such as esterification proceeds to lower the alcohol yield or to form a high-boiling oligomer of the ester. As a result, it is possible to avoid the problem that the piping at the bottom of the distillation column may be clogged, so that stable operation is possible and the industrial utility value is high.

Continued on the front page F term (reference) 4H006 AA02 AC41 AD11 BA02 BA06 BA11 BA23 BA26 BA29 BA32 BA51 BB31 BC37 BD20 BE20 FC22 FE11 FG29 4H039 CA60 CB40

Claims (9)

[Claims] 1. A raw material compound mainly composed of a carboxylic acid,
In a method for producing alcohols by performing a hydrogenation reaction in the presence of a catalyst to produce a reaction mixture containing alcohols, and recovering the alcohols by distillation separation from the reaction mixture, an organic carboxylic acid in a distillation column is used. A method for producing alcohols, wherein distillation is performed while maintaining the amount of acid at 0.5 wt% or less. 2. A raw material compound mainly composed of carboxylic acid,
In a method for producing alcohols by performing a hydrogenation reaction in the presence of a catalyst to produce a reaction mixture containing alcohols and recovering the alcohols by distillation separation from the reaction mixture, an alkaline compound is contained in a distillation column. A method for producing alcohols. 3. A starting compound mainly composed of carboxylic acid,
In a method for producing alcohols by performing a hydrogenation reaction in the presence of a catalyst to produce a reaction mixture containing alcohols and recovering the alcohols by distillation separation from the reaction mixture, an alkaline compound was added in advance. A method for producing alcohols, comprising supplying a reaction mixture to a distillation column. 4. The method for producing alcohols according to claim 1, wherein the raw material compound is mainly composed of an aliphatic carboxylic acid having 4 to 22 carbon atoms. 5. The method for producing alcohols according to claim 4, wherein the raw material compound is selected from maleic acid, succinic acid and adipic acid. 6. The method for producing alcohols according to claim 1, wherein the starting compound is 1,4-cyclohexanedicarboxylic acid. 7. The method for producing alcohols according to claim 1, wherein the catalyst is a heterogeneous catalyst containing Ru and Sn. 8. The hydrogenation reaction is carried out in the presence of a reaction solvent,
The method for producing alcohols according to any one of claims 1 to 7, wherein water is used as a reaction solvent. 9. The alcohol according to any one of claims 2 to 8, wherein the alkali compound is added to the hydrogenation reaction mixture in an alkali equivalent of at least a total of carboxylic acid groups derived from the organic carboxylic acid remaining in the hydrogenation reaction mixture. Manufacturing methods.