JPH04187654A - Production of aldehyde - Google Patents

Abstract

PURPOSE:To obtain an aldehyde in high selectivity by hydrogenation with H2 of a carboxylic acid or its alkyl ester using, as catalyst, chromium oxide carried on a specific aluminum oxide carrier. CONSTITUTION:Using, as catalyst, chromium oxide carried on an aluminum oxide carrier with a specific surface area of <=100m<2>/g determined by the BET method, an aliphatic, alicyclic, aromatic or heterocyclic carboxylic acid or its alkyl ester is hydrogenated by molecular hydrogen to directly obtain the objective corresponding aldehyde in high selectivity. The catalyst is excellent in terms of activity and working life, etc. The present production method is advantageous from an industrial point of view.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application) The present invention relates to a method for producing aldehydes that are valuable as intermediates in organic synthesis. Specifically, the present invention relates to an improvement in a method for producing aldehydes by hydrogenating carboxylic acids or alkyl esters thereof.

(Conventional technology) Aldehydes! ! Various methods have been reported to date. The most commonly used method using carboxylic acid or its derivatives as a raw material is the so-called Rosenmun method, which uses carboxylic acid chloride.
n+unt) reduction method, but it has the disadvantage of high manufacturing cost.

It would be most preferable if aldehydes could be efficiently produced by directly reducing carboxylic acids with molecular hydrogen, but this method has hitherto been considered extremely difficult. That is, in the hydrogenation reaction of carboxylic acids or derivatives thereof, a method using yttrium oxide as a catalyst (US Pat. No. 432
8373) or a method using aluminum oxide (
U.S. Patent No. 3,935,265) etc. have been reported,
These methods have problems with aldehyde selectivity.

The present inventors have previously reported a method for producing a corresponding aldehyde by hydrogenation reaction of a carboxylic acid or its ester using a catalyst containing zirconium oxide as a main component (for example, JP-A-60-152434; 1986-
No. 243037, JP-A-61-115043).

In this method, α- to carboxyl group is used as a raw material.
When using an aliphatic carboxylic acid or its ester in which two hydrogen atoms are bonded to the carbon position, a ketone body is generated as a by-product due to the decarboxylation condensation reaction, and the selectivity of the target aldehyde may not necessarily be sufficient. It was difficult. Also, when using a heterocyclic carboxylic acid or its ester containing a heteroatom such as N, S, or O in the heterocycle as a raw material,
Selectivity for aldehydes was insufficient.

On the other hand, it has been reported that when cycloalkyl esters of lower fatty acids such as acetic acid and n-butyric acid are hydrogenated using zinc oxide-chromium oxide as a catalyst, the corresponding acetaldehyde and n-butyraldehyde are produced, respectively, although in low yields. (Japanese Patent Publication No. 47-38410), and when methyl benzoate, pivalic acid, etc. are hydrogenated using iron oxide containing a small amount of chromium oxide as a catalyst, the corresponding aldehydes are produced with a certain degree of yield. It has been reported (European Patent No. 304,853) that, although the hydrogenation reaction progresses to some extent with these catalysts, it is difficult to obtain a yield that is sufficient for practical use, and the emergence of even higher performance catalysts is desired. There is.

As mentioned above, according to conventional reports, various carboxylic acids such as aliphatic, alicyclic, aromatic, and heterocyclic acids or their derivatives can be directly hydrogenated; A method for efficiently producing the catalyst has not yet been established, and there are many problems that need to be solved, such as improving the catalyst activity and selectivity of the target product, and extending the catalyst life.

(Problems to be Solved by the Invention) The present invention solves the problems of the conventional methods described above, and solves the problems of the conventional methods described above. , the objective is to provide a method for directly producing the respective corresponding aldehydes with excellent selectivity.

(Means for Solving the Problems) As a result of repeated studies to solve the above problems, the present inventors have found that the above objects can be achieved by using a specific catalyst supported on a specific carrier. The present invention was developed based on this knowledge.

That is, the gist of the present invention is to provide a method for producing an aldehyde by hydrogenating a carboxylic acid or its alkyl ester with molecular hydrogen in the presence of a catalyst, in which aluminum oxide having a specific surface area of 100 m2/g or less as measured by the BET method is used as a catalyst. A method for producing an aldehyde characterized by using chromium oxide supported on a carrier.

The present invention will be explained in detail below.

[Raw material] The starting materials used in the method of the present invention include various carboxylic acids such as aliphatic carboxylic acids, alicyclic carboxylic acids, aromatic carboxylic acids, and heterocyclic acids, or alkyl esters thereof. In particular, aliphatic carboxylic acids or alkyl esters thereof and alicyclic carboxylic acids or alkyl esters thereof are preferably used.

Examples of aliphatic carboxylic acids include acetic acid, propionic acid, butyric acid, isobutyric acid, pivalic acid, valeric acid, hexanoic acid, heptanoic acid, octanoic acid, 2-ethylhexanoic acid, nonanoic acid, decanoic acid, undecanoic acid, and lauric acid. Acid, tridecanoic acid, tetradecanoic acid, pentadecanoic acid, hexadecanoic acid, stearic acid, isostearic acid, nonadecanoic acid, tricosanoic acid, tetracosanoic acid, 1o-undecenoic acid, oleic acid, 1]-eicosenoic acid, etc. having 2 to 24 carbon atoms
Saturated or unsaturated aliphatic monocarboxylic acids: Aliphatic polycarboxylic acids such as oxalic acid, malonic acid, diethylmalonic acid, succinic acid, glutaric acid, adipic acid, decanedioic acid, and octadecanedioic acid.

Examples of the alicyclic carboxylic acids include cyclopentanecarboxylic acid, cyclohexanecarboxylic acid, and 1,4-cyclohexanedicarboxylic acid. These aliphatic carboxylic acids and alicyclic carboxylic acids contain substituents inert to the reaction, such as aryl groups, alkoxy groups, N,
It may have a heterocyclic group containing a heterocyclic group such as S, O, etc. Furthermore, as alkyl esters of aliphatic carboxylic acids and alicyclic carboxylic acids, lower alkyl esters having 1 to 4 carbon atoms such as methyl ester, ethyl ester, propyl ester, lobethyl ester, and isobutyl ester are preferable.

The aromatic carboxylic acid and its alkyl ester used as the raw material of the present invention have the following formula (1) Ar-(COO
R)n -----(1) (In the formula, R represents a hydrogen atom or an alkyl group, n represents I or the number of 2, and Ar is C
Examples include compounds represented by the aryl group which may have a substituent other than the 0OR group.

In the compound of formula (1), Ar is a phenyl group,
Examples include aryl groups such as naphthyl group and anthryl group, and c that Ar may have.

Examples of substituents other than the OR group include alkyl groups, cycloalkyl groups, alkoxy groups, aryloxy groups, halogen atoms, hydroxyl groups, formyl groups, and acyl groups. Furthermore, R includes, in addition to a hydrogen atom, an alkyl group such as a methyl group, an ethyl group, a propyl group, an n-butyl group, and an isobutyl group. Specific examples of the compound of formula (1) include benzoic acid, toluic acid, dimethylbenzoic acid, cyclohexylbenzoic acid, cumic acid, t
-Butylbenzoic acid, phenylbenzoic acid, anisic acid, phenoxybenzoic acid, chlorobenzoic acid, hydroquinebenzoic acid, acetylbenzoic acid, naphthoic acid, phthalic acid, anthracenecarboxylic acid, and the esters include the above-mentioned carboxylic acids. Lower alkyl esters having 1 to 4 carbon atoms such as methyl ester, ethyl ester, propyl ester, n-butyl ester, and isobutyl ester are preferred.

Furthermore, the heterocyclic carboxylic acid and its ester used as the raw material of the present invention have at least one N,
It is a carboxylic acid or its ester containing a hetero atom such as S or 0, and specific examples of the heterocycle include a pyrrole ring, a furan ring, a thiophene ring, an oxazole ring, a thiazole ring, an oxazoline ring, an imidazole ring, an imidasoline ring, Examples include a pyrazole ring, a pyran ring, a thiopyran ring, a pyridine ring, a quinoline ring, an oxazine ring, a thiazine ring, a pyrimidine ring, a pyrazine ring, a triazine ring, an azepine ring, and an oxepine ring. In addition, as the carboxylic acid ester group, lower alkyl esters having 1 to 4 carbon atoms such as methyl ester, ethyl ester, propyl ester, n-butyl ester, and isobutyl ester are preferable. Specific examples of heterocyclic carboxylic acids and esters thereof include nicotinic acid, furocarboxylic acid, thiazolecarboxylic acid, and alkyl esters thereof.

[Catalyst] In the present invention, as a catalyst for hydrogenating the above raw material, a catalyst having a specific surface area of 100 m2 measured by the BET method is used.
It is an essential requirement to use aluminum oxide supported on an aluminum oxide support of /g or less,
This point is an important feature of the present invention. A preferable specific surface area of the aluminum oxide support is 1 to 80II+278, and a particularly preferable specific surface area is 2 to 50II12/g. Note that all values of specific surface area described below indicate values measured by the BET method.

Examples of chromium oxide include commercially available chromium hydroxides, sulfates, nitrates, and halides; chromic anhydride; inorganic salts such as ammonium salts and alkali metal salts of dichromic acid; and chromium formates, acetates, and oxalates. Chromium hydroxide or nitrate, chromic anhydride, dichromium It is desirable to use thermally decomposed raw materials that decompose at relatively low temperatures and do not contain other poisonous elements, such as ammonium salts of acids or chromium formates, acetates, oxalates, and the like.

On the other hand, as the aluminum oxide carrier (hereinafter referred to as alumina carrier), commercially available gibbsite, vialite, hemite, norstrandite, diasbore, amorphous alumina gel, χ-1ρ-1η-1θ-5γ-5σ-1δ-1
α-alumina, or inorganic salts such as aluminum sulfates, nitrates, and halides, and organic salts such as acetates, oxalates, and aluminum alkoxides are used as raw materials, and these are treated by precipitation methods, thermal decomposition methods, etc. However, it is desirable to use raw materials that do not contain poisonous elements. Although the alumina carrier can be used in powder form, it is practically convenient to use it after molding it into a suitable shape. The specific surface area of the alumina support is 1! ! Although it is affected by the method, it can generally be controlled by changing the firing temperature. For example, the surface area is 270n2/g
When using γ-alumina, an alumina support having a specific surface area of 1OOII2/g or less can be obtained by firing at a temperature of 900°C or higher.

In order to support chromium oxide on an alumina carrier, known methods such as impregnation, adsorption, kneading, deposition, and evaporation to dryness are employed using the above-mentioned chromium raw material, and then heated at 400°C to
Calcining is carried out at a temperature of 1200°C, preferably 500°C to 1000°C. The catalyst can be shaped by known methods. For example, a tableting method, a method of spray drying and then calcination, or adding water to a chromium compound and an alumina carrier,
If necessary, a binder is added and kneaded, followed by extrusion molding, followed by drying and baking at a predetermined temperature.

[Hydrogenation reaction The hydrogenation reaction of cocarboxylic acid or its alkyl ester with molecular hydrogen is carried out in the presence of the above-mentioned catalyst in the gas phase at a temperature of 200°C to 500°C, preferably 250°C to 450°C.
It is advantageous to carry out the The reaction pressure may be normal pressure, but it may also be carried out under slightly increased pressure.

When the catalyst is used, for example, as a fixed bed catalyst, the space velocity of the raw material carboxylic acid or its alkyl ester is LH5V
as 0. About O1 to l hr-', preferably: 0.
Approximately 0.03 to 0.5 hr-' is appropriate. On the other hand, the space velocity of hydrogen is 100 to 20,000 h as GH5V
About r-1, preferably 500 to 5,000 hr-'
It is appropriate to set it as a degree. The hydrogen used may contain some inert residue such as nitrogen, water vapor, etc.

Note that the hydrogenation reaction of the present invention is not limited to a fixed bed method, and other reaction methods such as a fluidized bed method may also be employed.

(Examples) Next, the present invention will be explained in more detail with reference to Examples, but the present invention is not limited to the following Examples unless it exceeds the gist thereof.

Example 1 A commercially available spherical α-alumina carrier with a diameter of 5III11 and a specific surface area of 2.3 m2/g 44. An aqueous solution of 25.8 g of chromium nitrate nonahydrate dissolved in 1001 of water was added to Og, evaporated to dryness, and then calcined in air at 700°C for 3 hours to form a chromium oxide/α-alumina carrier catalyst (Cr
20. 10% by weight) was prepared.

Using the above catalyst, hydrogenation reaction of n-caprylic acid was carried out under normal pressure, acid space velocity: LHSV = 0.11 kg/l -C
at -hr, space velocity of hydrogen: (JSV=+250
It was carried out under the conditions of hr-'.

The conversion rate of n-caprylic acid at a reaction temperature of 380°C is 9
6.4%, and the selectivity of n-caprylaldehyde is 9.
It was 5.7%.

Example 2 A commercially available spherical γ-alumina carrier with a diameter of 4 im and a specific surface area of 273 II + 27 g was calcined in air at 1080°C for 3 hours to obtain a specific surface area of 27.3 m2/g.
An alumina support was prepared. The crystal form of the alumina after firing was confirmed to be α-alumina by X-ray diffraction.

Instead of the α-alumina support with a specific surface area of 2.3 m2/g used in Example 1, the specific surface area of 27.3 obtained by the above method was used.
1 m2/g of α-alumina carrier was used, others were as in Example]
A chromium oxide/α-alumina carrier catalyst (10% by weight as Cr20.) was prepared by mixing with an aqueous chromium nitrate solution, evaporating to dryness, and firing in the same manner as above.

Using the above catalyst and under the same conditions as shown in Example 1, n-
When the hydrogenation reaction of caprylic acid was carried out, the reaction temperature was 3.
The conversion rate of n-caprylic acid at 80°C was 97.4%, and the selectivity of n-caprylic aldehyde was 94.9%.

Example 3 The commercially available spherical γ-alumina carrier used in Example 2 was calcined in air at 1200° C. for 3 hours to prepare an alumina carrier having a specific surface area of 9.2 m 2 /g.

Instead of the alumina support with a specific surface area of 2.3 m2/g used in Example 1, the specific surface area of 9.2 w1 obtained by the above method was used.
A chromium oxide/α-alumina carrier catalyst (10 weight as Cr203) was prepared by mixing with an aqueous chromium nitrate solution, evaporating to dryness, and calcining using the same method as in Example 1 except for using an alumina support of 2/g. %) Sl! I! ! Shita.

Using the above catalyst and under the same conditions as shown in Example 1, n-
When the hydrogenation reaction of caprylic acid was carried out, the reaction temperature was 3.
The conversion rate of n-caprylic acid at 80°C was 57.0%, and the selectivity of n-caprylic aldehyde was 95.5%. Incidentally, the amount of by-products such as ketone bodies was extremely small.

Examples 4 to 7 Using the chromium oxide/α-alumina supported catalyst (10% by weight as Cr203) prepared by the method of Example 1, pivalic acid, cyclohexanecarboxylic acid, benzoic acid, and 3-nicotine were used as reaction substrates. A hydrogenation reaction was carried out using methyl acid under the conditions shown in Table 1.

The results are shown in Table 1.

Table 1 Water cyst formation reaction conditions Results 1 4 1 Hiba'J 7a! 7:1250
Shi-080: 410' 97.9 1 97.9
Comparative Example 1 The commercially available spherical γ-alumina carrier used in Example 2 was calcined in air at 900°C for 3 hours to prepare an alumina carrier having a specific surface area of 1311I12/8.

Instead of the alumina support with a specific surface area of 2.3 m2/g used in Example 1, the specific surface area of 31 m2/g obtained by the above method was used.
A chromium oxide/α-alumina carrier catalyst (
10% by weight as Cr203): Ai! T, ta.

Using the above catalyst and under the same conditions as shown in Example, n-
When the hydrogenation reaction of caprylic acid was carried out, the reaction temperature was 3.
The conversion rate of n-caprylic acid at 90°C was 60.0%, and the selectivity of n-caprylic aldehyde was 44.7%.

(Effects of the Invention) According to the method of the present invention, as specifically shown in the above examples, various carboxylic acids can be and their esters, the corresponding aldehydes can be obtained efficiently with excellent selectivity, and this greatly contributes to the industrial production of these aldehydes.

Claims (1)

[Claims] (1) In the method of hydrogenating a carboxylic acid or its alkyl ester with molecular hydrogen in the presence of a catalyst to produce an aldehyde, the catalyst is supported on an aluminum oxide carrier having a specific surface area of 100 m^2/g or less as measured by the BET method. A method for producing an aldehyde, characterized by using chromium oxide.