Method for producing saturated homoethers from carbonyl compounds

Abstract

To provide a method for efficiently producing, from a carbonyl compound, a saturated homoether having a carbon number four times the carbon number thereof.SOLUTION: The saturated homoether having carbon atoms of 4 times number of the raw material carbonyl compound is produced by using a carbonyl compound and hydrogen as raw material, and reacting both a dimerization of carbonyl compound by aldol condensation reaction and a subsequent coupling reaction of the dimerized carbonyl compound with a catalyst in which a metal is supported on an acidic catalyst carrier.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a method for producing saturated homoethers from carbonyl compounds via dimerized carbonyl compounds. [Background technology]

[0002] Higher saturated homoethers, like higher esters, have special properties not found in alkanes, such as low viscosity, high flash point, and low pour point, and are also used as base oils for hydraulic fluids, taking advantage of their characteristic of having little penetration into sealing rubber used in packings (Non-Patent Document 1). There are two common methods for producing saturated homoethers: the dehydration dimerization of alcohols using an acid catalyst, or a two-step reaction from an aldehyde via a (hemi)acetal. The dehydration dimerization of alcohols using an acid catalyst is generally carried out using an inorganic acid such as a protonic acid, such as sulfuric acid or hydrochloric acid, or a solid acid catalyst such as silica-alumina or Nafion (Non-Patent Document 2). Although the reaction is simple, there is a problem in that a large amount of olefin is produced as a by-product due to intramolecular dehydration, which hinders improvement of the selectivity for the target product. On the other hand, the method via an acetal uses two types of raw materials, namely, an aldehyde and an alcohol, and therefore, when producing an ether having different ends, the method via a (hemi)acetal is a preferable method. However, even when producing a homoether having the same groups at both ends, a (hemi)acetal is formed and converted into a vinyl ether, and then the vinyl group must be reacted under pressure in the presence of hydrogen and a hydrogenation catalyst, making the process complicated. In addition, two types of raw materials, namely, an aldehyde and an alcohol, must be prepared, which poses the problem of increased capital investment. For example, Patent Document 1 discloses a method for producing an ether compound, which is characterized by reacting a specific carbonyl compound with a specific hydroxy compound under a hydrogen atmosphere using a palladium catalyst supported on carbon powder. The examples in this document disclose the use of 5% Pd-zeolite (Example 5), 5% Pd-silica alumina (Example 6), and 5% Pd-alumina (Example 7) as catalysts, but none of these discloses homoethers, and the isolation yields are not satisfactory. Furthermore, Patent Document 2 discloses a method for producing an ether compound, which includes a step of reacting a hydroxy compound and / or a carbonyl compound in a hydrogen atmosphere using a catalyst to obtain a reaction product containing an ether compound, and in the examples, the production of a homoether is disclosed. For mass-produced chemical products, so-called general-purpose products, the manufacturing process and the number of raw materials used are directly reflected in the cost, so it is necessary to shorten the reaction process as much as possible. In other words, when a product is manufactured through a multi-step process, it is clearly extremely effective to use compounds from an earlier step as raw materials, and to produce it with fewer raw materials and in a shorter process in order to reduce production costs. In short, the market demands more efficient and lower cost manufacturing methods. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 09-87223 [Patent Document 2] Japanese Patent Application Laid-Open No. 2000-38364 [Non-patent literature]

[0004] [Non-Patent Document 1] Journal of the Petroleum Society, Vol. 31, p. 448 (1988) [Non-patent document 2] Catalysis Letters 46(1997) 1-4 DISCLOSURE OF THE INVENTION [Problem to be solved by the invention]

[0005] An object of the present invention is to solve the above-mentioned conventional technical problems and to provide a method for efficiently producing, from a carbonyl compound, a saturated homoether having four times the number of carbon atoms of the carbonyl compound. [Means for solving the problem]

[0006] As a result of extensive research, the present inventors have found that by using a carbonyl compound and hydrogen as raw materials in the presence of a bifunctional catalyst having both a metal catalytic function and an acid catalytic function, the carbonyl compound is dimerized by an aldol condensation reaction, and the dimerized carbonyl compound is then further hydrogenated and reacted directly over the same catalyst, it is possible to reduce the reaction steps and efficiently produce a saturated homoether having four times the carbon number of the original carbonyl compound, via the dimerized carbonyl compound, from the carbonyl compound, and have completed the present invention.

[0007] The present invention comprises a catalyst for producing saturated homoethers and a process for producing saturated homoethers. The catalyst for producing saturated homoether of the present invention is defined in the following items (1) to (7). (1) A method for producing saturated homoethers using carbonyl compounds and hydrogen as raw materials, in which the carbonyl compounds are dimerized by aldol condensation and the dimerized carbonyl compounds are subsequently coupled using a catalyst comprising a metal supported on an acidic catalyst carrier to produce saturated homoethers having four times the number of carbon atoms as the raw material carbonyl compound.

[0008] (2) The carbonyl compound is an aldehyde represented by formula (1), the dimerized carbonyl compound is an aldehyde represented by formula (2), and a saturated homoether compound represented by formula (3) is produced. A method for producing a saturated homoether according to item (1). TIFF0007740865000001.tif2049 (In formula (1), R 1 and R 2 are independently hydrogen, alkyl having 1 to 20 carbon atoms, alkenyl having 2 to 20 carbon atoms, alkynyl having 2 to 20 carbon atoms, cycloalkyl having 5 to 20 members, aryl having 5 to 20 members, or heterocyclic having 5 to 20 members. At least one hydrogen bonded to a carbon atom in these groups may be replaced with a halogen, a hydroxyl group, a carbonyl, or other substituent. TIFF0007740865000002.tif3164 (In formula (2), R 1 and R 2 are the same as in equation (1). TIFF0007740865000003.tif35116 (In formula (3), R 1 and R 2 are the same as in equation (1).

[0009] (3) In equation (1), R 1 and R 2 are independently hydrogen, alkyl having 1 to 20 carbon atoms, or alkenyl having 2 to 20 carbon atoms.

[0010] (4) The method for producing a saturated homoether according to any one of items (1) to (3), wherein the carbonyl compound is butanal, the dimerized carbonyl compound is 2-ethylhexanal, and the saturated homoether is bis-(2-ethylhexyl) ether.

[0011] (5) The method for producing a saturated homoether according to any one of items (1) to (3), wherein the carbonyl compound is propanal, the dimerized carbonyl compound is 2-methylpentanal, and the saturated homoether is bis-(2-methylpentyl) ether.

[0012] (6) The method for producing saturated homoethers according to item (1), wherein the supported metal is palladium.

[0013] (7) The method according to item (1), wherein the support is at least one selected from the group consisting of alumina, silica, and silica-alumina. DETAILED DESCRIPTION OF THE INVENTION

[0014] The present invention is a method for obtaining saturated homoethers from carbonyl compounds via dimerized carbonyl compounds in the presence of a catalyst in which a metal is supported on an acidic catalyst carrier and hydrogen.

[0015] (Catalyst carrier) The acidic catalyst support in the method for producing saturated homoether of the present invention can be a so-called solid acid, and examples of the solid acid include metal oxides such as alumina, silica, silica-alumina, titania, silica-titania, and zeolite, and cation exchange resins. Any form of solid acid can be used as the acidic catalyst support, such as a commercially available product, a calcined commercially available product, a metal hydroxide, or a product obtained by thermal decomposition of an organometallic compound.

[0016] (catalyst) The catalyst used in the present invention is a catalyst in which a metal is supported on an acidic catalyst carrier, and the metal is preferably palladium, platinum, ruthenium, etc., and more preferably palladium. The catalyst used in the present invention can be prepared by supporting these metals on an acidic catalyst carrier by a known method, such as impregnation or coprecipitation.

[0017] (Production method, reaction form) The method for producing saturated homoethers from carbonyl compounds of the present invention uses carbonyl compounds and hydrogen as raw materials. It is characterized by the dimerization of the carbonyl compounds by aldol condensation and the subsequent coupling reaction of the dimerized carbonyl compounds, both of which are carried out using a catalyst consisting of a metal supported on an acidic catalyst carrier. This means that saturated homoethers with four times the carbon number of the raw material carbonyl compounds can be obtained.

[0018] (Reaction Apparatus) The reaction apparatus used in the production of the saturated homoether of the present invention is not particularly limited. For example, a saturated homoether can be produced by placing the raw material carbonyl compound and a catalyst in a batch reactor, dimerizing them by an aldol condensation reaction, and then reacting them under hydrogen pressure. Alternatively, a saturated homoether can be produced by installing a catalyst layer in a fixed-bed reactor, setting the reactor at a reaction temperature, and then passing the raw material carbonyl compound and hydrogen through the reactor.

[0019] (Target raw materials) The carbonyl compound used as the raw material is not particularly limited, but an aldehyde having two hydrogen atoms at the second position relative to the carbonyl having 2 to 6 carbon atoms, i.e., two α-hydrogen atoms, is preferred. Examples include ethanal, propanal, butanal, pentanal, and hexanal.

[0020] (Target product) Saturated homoethers obtained from these raw materials include dibutyl ether, bis(2-methylpentyl) ether, bis(2-ethylhexyl) ether, bis(2-propylheptyl) ether, and bis(2-butyloctyl) ether.

[0021] (Reaction conditions and temperature) The reaction temperature in the method for producing saturated homoether of the present invention is preferably in the range of 100°C to 250°C. To ensure sufficient reaction, a temperature of 100°C or higher is preferred, while a temperature of 250°C or lower is preferred to maintain good product selectivity. A more preferred temperature range is 120°C to 200°C. [Example]

[0022] The effects of the present invention will be specifically explained below with reference to examples, but the present invention is not limited to these examples. (Reaction Apparatus) The reactor used was an autoclave (start-200) manufactured by Nitto Koatsu Co., Ltd. The reactor was equipped with a pipe for introducing hydrogen gas, and hydrogen gas was introduced into the reactor from here.

[0023] [Example 1] 22.14 g (1.25 mol%) of 5% palladium-supported alumina (palladium alumina manufactured by NE Chemcat) as a catalyst and 60.0 g of butanal (special grade reagent manufactured by Wako Pure Chemical Industries) were weighed into a 200 ml stainless steel autoclave (start-200, manufactured by Nitto Koatsu). After replacing the atmosphere inside the autoclave with nitrogen, the autoclave was sealed and heated to 150°C, maintained for 6 hours, and then sampled and analyzed by GC. The system was then pressurized to 4 MPa using hydrogen, and the temperature was then raised to 150°C and maintained for 6 hours. After cooling to room temperature, the pressure was reduced to atmospheric pressure, and the reaction liquid was collected and analyzed by GC. The reaction products were identified using a gas chromatograph mass spectrometer (Shimadzu GC / MS-TQ8040) and a nuclear magnetic resonance spectrometer (Agilent Technologies VARIAN NMR System 500 MHz). The reaction products were quantified using a gas chromatograph (Shimadzu GC2014 FID detector) equipped with a capillary column (Agilent Technologies DB-1 60 m). After calibration, the residual rate of butanal (nBA) and the selectivities of 2-ethylhexenal (2EH), 2-ethylhexanal (2EHA), 2-ethylhexanol (OA), bis(2-ethylhexyl) ether (DOE), and butanol (nBO) were determined. The results are shown in Tables 1 and 2.

[0024] [Example 2] Except for changing the amount of catalyst to 0.50 mol %, the same procedure as in Example 1 was followed. The results are shown in Tables 1 and 2.

[0025] [Example 3] Except for changing the amount of catalyst to 0.10 mol %, the same procedure as in Example 1 was followed. The results are shown in Tables 1 and 2.

[0026] [Example 4] The procedure was the same as in Example 2, except that the reaction temperature was changed to 120° C. The results are shown in Tables 1 and 2.

[0027] [Comparative Example 1] The procedure was the same as in Example 1, except that sponge nickel (sponge nickel manufactured by Tokyo Chemical Industry Co., Ltd.) was used as the catalyst. The results are shown in Tables 1 and 2.

[0028] Comparative Example 2 The procedure was the same as in Example 1, except that aluminum oxide (activated alumina manufactured by Wako Pure Chemical Industries, Ltd.) was used as the catalyst. The results are shown in Tables 1 and 2.

[0029] Table 1 TIFF0007740865000004.tif57149

[0030] Table 2 TIFF0007740865000005.tif57137

[0031] [Example 5] The procedure was the same as in Example 2, except that the raw material was changed to propanal. The results are shown in Tables 3 and 4. The residual rate of propanal (hereinafter abbreviated as nPA), and the selectivities of 2-methylpentenal (hereinafter abbreviated as 2MP), 2-methylpentanal (hereinafter abbreviated as 2MPA), 2-methylpentanol (hereinafter abbreviated as PO), bis(2-methylpentyl) ether (hereinafter abbreviated as DHE), and propanol (hereinafter abbreviated as nPO) were determined.

[0032] Table 3 TIFF0007740865000006.tif26145

[0033] Table 4 TIFF0007740865000007.tif26129

[0034] In all Examples, the composition of saturated homoethers containing four times as many carbon atoms as the carbonyl compounds, which are the target products after the second reaction, exceeded 25%, and in Example 1 the composition exceeded 50%. On the other hand, in the Comparative Examples, it can be seen that the target saturated homoethers were hardly produced at all. [Industrial Applicability]

[0035] The method of the present invention for producing a saturated homoether having four times the carbon number of the starting carbonyl compound uses only the carbonyl compound as a starting material, thereby contributing to shortening the process for producing a saturated homoether having four times the carbon number of the carbonyl compound, and is an industrially very effective production method.

Claims

1. A method for producing a saturated homoether represented by formula (3) using a carbonyl compound represented by formula (1) and hydrogen as raw materials, wherein all of the following reactions are carried out in the same reactor using the same catalyst comprising palladium supported on an acidic catalyst carrier: dimerization of the carbonyl compound represented by formula (1) by aldol condensation reaction, subsequent hydrogenation of the dimerized carbonyl compound to produce a carbonyl compound represented by formula (2), and a coupling reaction of the dimerized carbonyl compound represented by formula (2), thereby producing a saturated homoether having four times the number of carbon atoms as the raw material carbonyl compound. (In formula (1), R １ is hydrogen, and R ２ is hydrogen, methyl, or ethyl. (In formula (2), R １ and R ２ are the same as in formula (1). (In formula (3), R １ and R ２ are the same as in formula (1).

2. 2. The method for producing a saturated homoether according to claim 1, wherein the carbonyl compound is butanal, the dimerized carbonyl compound is 2-ethylhexanal, and the saturated homoether is bis-(2-ethylhexyl) ether.

3. 2. The method for producing a saturated homoether according to claim 1, wherein the carbonyl compound is propanal, the dimerized carbonyl compound is 2-methylpentanal, and the saturated homoether is bis-(2-methylpentyl) ether.

4. A manufacturing method described in any one of claims 1 to 3, wherein the support is one or more selected from alumina, silica, and silica-alumina.

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