Method and system for producing mid-branched saturated alcohol compound, and catalyst

Abstract

To provide a method and system for efficiently producing a mid-branched saturated alcohol via a novel synthetic reaction, a production reaction catalyst for a mid-branched saturated alcohol compound in the production method and production system.SOLUTION: There is provided a method for producing a mid-branched saturated alcohol compound, comprising reacting acetaldehyde and methanol in the presence of a metal oxide catalyst to produce a branched saturated alcohol compound having 3 to 10 carbon atoms. There is also provided a system for producing a mid-branched saturated alcohol compound, comprising: a reaction apparatus A for oxidizing ethanol to produce acetaldehyde; and a reaction apparatus B for reacting the acetaldehyde with methanol in the presence of a metal oxide catalyst to produce a branched saturated alcohol compound having 3 to 10 carbon atoms. There is also provided a metal oxide catalyst for catalyzing a reaction for producing a branched saturated alcohol compound with carbon numbers 3 to 10, using acetaldehyde and methanol as raw materials, wherein the metal oxide catalyst contains a metal oxide and does not contain a simple metal.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method and system for producing a mid-chain branched saturated alcohol compound, and also to a catalyst for a reaction for producing a mid-chain branched saturated alcohol compound in the method and system. [Background technology]

[0002] Mid-chain branched saturated alcohols, such as isobutanol (isobutyl alcohol, 2-methyl-1-propanol), are attracting attention as a raw material for sustainable aviation fuel (SAF) and as a drop-in fuel that can be used in existing infrastructure. Synthesizing isobutanol from, for example, bioethanol or green methanol can contribute to the realization of sustainable green energy.

[0003] There are known methods for producing isobutanol by catalytic reaction using lower alcohols, including methanol, as raw materials. For example, Patent Document 1 describes the production of isobutanol by reacting ethanol or propanol with methanol in the presence of a hydroxyapatite catalyst. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-79145 Summary of the Invention [Problem to be solved by the invention]

[0005] An object of the present invention is to provide an efficient method and system for producing mid-chain branched saturated alcohols by a novel synthesis reaction, and a catalyst for the reaction for producing mid-chain branched saturated alcohol compounds in the production method and production system. [Means for solving the problem]

[0006] In view of the above problems, the present inventors have conducted extensive research and have attempted to use acetaldehyde, an ethanol oxide, as a starting material to produce a mid-chain branched saturated alcohol by reacting this acetaldehyde with methanol. As a result, they have found that the target mid-chain branched saturated alcohol can be produced with high efficiency by reacting acetaldehyde with methanol in the presence of a metal oxide. The present invention was completed based on this finding and further research.

[0007] The above-mentioned object of the present invention is achieved by the following means. [1] A method for producing a mid-chain branched saturated alcohol compound, comprising reacting acetaldehyde with methanol in the presence of a metal oxide catalyst to produce a branched saturated alcohol compound having 3 to 10 carbon atoms. [2] The method for producing a mid-chain branched saturated alcohol compound according to [1], wherein the branched saturated alcohol compound having 3 to 10 carbon atoms produced by the reaction contains isobutanol. [3] The method for producing a mid-chain branched saturated alcohol compound according to [1] or [2], wherein the proportion of isobutanol in all alcohol-aldehyde compounds having 3 to 10 carbon atoms produced by the reaction is 50% or more based on the carbon amount. [4] The method for producing a mid-chain branched saturated alcohol compound according to any one of [1] to [3], wherein a mixed gas of the acetaldehyde and the methanol is contacted with the metal oxide catalyst. [5] A method for producing the mid-chain branched saturated alcohol compound according to any one of [1] to [4], comprising oxidizing ethanol to obtain the acetaldehyde. [6] [6] The method for producing a mid-chain branched saturated alcohol compound according to [5], wherein the ethanol includes bioethanol. [7] The method for producing a mid-chain branched saturated alcohol compound according to any one of [1] to [6], wherein the methanol includes green methanol. [8] A system for producing a medium-chain branched saturated alcohol compound, comprising: a reactor A for oxidizing ethanol to produce acetaldehyde; and a reactor B for reacting the acetaldehyde with methanol in the presence of a metal oxide catalyst to produce a branched saturated alcohol compound having 3 to 10 carbon atoms. [9] The system for producing a mid-chain branched saturated alcohol compound according to [8], wherein the branched saturated alcohol compound having 3 to 10 carbon atoms produced in the reaction device B includes isobutanol.

[10] The system for producing a mid-chain branched saturated alcohol compound according to [8] or [9], wherein the proportion of isobutanol in all alcohol-aldehyde compounds having 3 to 10 carbon atoms produced in the reaction apparatus B is 50% or more based on the carbon amount.

[11] A metal oxide catalyst containing metal oxides but not elemental metals, which is used to catalyze the reaction of producing branched saturated alcohol compounds having 3 to 10 carbon atoms using acetaldehyde and methanol as raw materials.

[12]

[12] The metal oxide catalyst according to

[11] , wherein the branched saturated alcohol compound having 3 to 10 carbon atoms includes isobutanol.

[13] The metal oxide catalyst according to

[11] or

[12] , wherein the proportion of isobutanol in all alcohol-aldehyde compounds having 3 to 10 carbon atoms produced in the production reaction is 50% or more based on the carbon amount. [Effects of the Invention]

[0008] According to the method and system for producing a mid-chain branched saturated alcohol compound of the present invention, the target mid-chain branched saturated alcohol can be efficiently obtained by a new synthesis reaction. [Brief explanation of the drawings]

[0009] [Figure 1]FIG. 1 is a diagram schematically illustrating a gas-phase flow reaction system for carrying out the production method of the present invention. [Figure 2] FIG. 2 shows the results of gas chromatography analysis of the reaction product of Example 1. [Figure 3] FIG. 3 shows the results of gas chromatography analysis of the reaction product of Reference Example 1. [Figure 4] FIG. 4 shows the results of gas chromatography analysis of the reaction product of Reference Example 2. [Figure 5] FIG. 5 shows the results of gas chromatography analysis of the reaction product of Reference Example 3. DETAILED DESCRIPTION OF THE INVENTION

[0010] A preferred embodiment of the present invention will be described below, but the present invention is not limited to the following embodiment except as defined by the present invention.

[0011] [Method of producing a medium-chain branched saturated alcohol compound] In the method for producing a mid-chain branched saturated alcohol compound of the present invention (hereinafter also referred to as "the production method of the present invention"), acetaldehyde and methanol are used as raw materials. By reacting acetaldehyde and methanol in the presence of a metal oxide catalyst, a mid-chain branched saturated alcohol compound can be efficiently obtained. In the present invention, a "medium chain" alcohol compound means an alcohol compound having 3 to 10 carbon atoms. Therefore, when simply referring to a "mid-chain branched saturated alcohol compound," it means a branched saturated alcohol compound having 3 to 10 carbon atoms. By the production method of the present invention, one or more branched saturated alcohol compounds having 3 to 10 carbon atoms can be obtained. A preferred embodiment of the manufacturing method of the present invention will be described.

[0012] <Raw materials> In the production method of the present invention, acetaldehyde and methanol are used as raw materials for the catalytic reaction carried out in the presence of a metal oxide catalyst. The acetaldehyde may be a commercially available product or may be synthesized by a conventional method. For example, acetaldehyde can be obtained by oxidizing ethanol. The reaction for producing acetaldehyde from ethanol is known per se, and reference can be made to the following literature, for example:

[0013] James M. Church and Hanamant K. Joshi, Acetaldehyde by dehydrogenation of ethyl alcohol., Industrial & Engineering Chemistry 43, 8, 1804-1811(1951); Giovanni Pampararo, Gabriella Garbarino, Paola Riani, Maria Villa Garcia, Vicente Sanchez, Escribano, Guido Busca, A study of ethanol dehydrogenation to acetaldehyde over supported copper catalysts: Catalytic activity, deactivation and regeneration, Applied Catalysis A: General, 602, 117710 (2020); Chongyang Wang, Gabriella Garbarino, Lawrence F. Allard, Faith Wilson, Guido Busca and Maria Flytzani-Stephanopoulos, Low-Temperature Dehydrogenation of Ethanol on Atomicly Dispersed Gold Supported on ZnZrOx, ACS Catalysis, 6, 210-218 (2016); Jifeng Pang, Ming Yin, Pengfei Wu, Xianquan Li, Haoyu Li, Mingyuan Zheng and Tao Zhang, Advances in catalytic dehydrogenation of ethanol to acetaldehyde., Green Chemistry, 23, 7902-7916 (2021)

[0014] Therefore, the production method of the present invention preferably includes a step of reacting acetaldehyde obtained by oxidizing ethanol with methanol in the presence of a metal oxide catalyst to produce a branched saturated alcohol compound having 3 to 10 carbon atoms. Alternatively, the production method of the present invention itself may include a step of oxidizing ethanol to obtain acetaldehyde, and a step of reacting the resulting acetaldehyde with methanol in the presence of a metal oxide catalyst to produce a branched saturated alcohol compound having 3 to 10 carbon atoms.

[0015] When the production method of the present invention uses acetaldehyde obtained by oxidizing ethanol as a raw material or includes a step of obtaining acetaldehyde by oxidizing ethanol, it is preferable to use bioethanol as the ethanol. Bioethanol is ethanol obtained by fermenting biomass (sugarcane, corn, wood, etc.). The use of bioethanol can contribute to the advancement of carbon neutrality. Therefore, the production method of the present invention preferably includes a step in which the raw material acetaldehyde includes acetaldehyde obtained by oxidizing bioethanol, and a step in which the acetaldehyde is reacted with methanol in the presence of a metal oxide catalyst to produce a branched saturated alcohol compound having 3 to 10 carbon atoms. Alternatively, the production method of the present invention itself may include a step of oxidizing bioethanol to obtain acetaldehyde and a step in which the obtained acetaldehyde is reacted with methanol in the presence of a metal oxide catalyst to produce a branched saturated alcohol compound having 3 to 10 carbon atoms.

[0016] The above-mentioned methanol may be a commercially available product or may be synthesized by a conventional method. Most methanol is produced from natural gas. Meanwhile, green methanol, which contributes to the development of a decarbonized society, has recently been attracting attention. Green methanol is methanol produced using hydrogen and carbon dioxide as raw materials. For example, methanol obtained by reacting hydrogen obtained by water electrolysis using renewable energy as a power source with carbon dioxide is particularly suitable as a raw material for the production method of the present invention. Therefore, in the production method of the present invention, it is preferable that the raw material methanol contains green methanol.

[0017] <Catalyst> In the production method of the present invention, the reaction of acetaldehyde with methanol is carried out in the presence of a metal oxide catalyst. One or more metal oxide catalysts are used as catalysts in the reaction. The metal oxide catalyst can be used in the reaction in the form of a powder or a molded product such as granules or pellets. The metal oxide catalyst is used as a solid catalyst (solid-phase catalyst) in the production method of the present invention.

[0018] In the present invention, the term "metal oxide catalyst" refers to any catalyst that contains a metal oxide and catalyzes the reaction of acetaldehyde with methanol to produce a branched saturated alcohol compound having 3 to 10 carbon atoms. For example, any metal oxide can function as a catalyst for the reaction of acetaldehyde with methanol. The metal oxide catalyst may be a metal oxide (basic metal oxide or amphoteric metal oxide) itself, or a chemically modified metal oxide. For example, a metal oxide with increased acid strength due to the introduction of acid sites (referred to as "acidified metal oxide" in the present invention) may be used. A composite of two or more metal oxides (referred to as "composite metal oxide" in the present invention) can also be preferably used as a catalyst. Here, a catalyst that contains both a metal oxide and an elemental metal is not a "metal oxide catalyst" in the present invention. For example, a catalyst in which copper (elemental copper) is supported on zirconia (ZrO2) is not a "metal oxide catalyst" in the present invention. That is, the metal contained in the metal oxide catalyst of the present invention exists in a state bound to oxygen.

[0019] Examples of basic metal oxides suitable as catalysts for use in the production method of the present invention include magnesium oxide, calcium oxide, barium oxide, and strontium oxide.

[0020] Examples of amphoteric metal oxides suitable as catalysts for use in the production method of the present invention include zirconia, ceria, lanthana, scandia, zinc oxide, aluminum oxide, tin oxide, lead oxide, cobalt oxide, chromium oxide, and molybdenum oxide.

[0021] Examples of acidified metal oxides suitable as catalysts for use in the production method of the present invention include sulfated zirconia, sulfated titania, sulfated alumina, sulfated cobalt oxide, phosphated zirconia, phosphated titania, and phosphated alumina.

[0022] Examples of composite metal oxides suitable as catalysts for use in the production method of the present invention include ceria-zirconia, silica-alumina, various zeolites, silica-zirconia, silica-titania, various heteropolyacids, alumina-magnesia, yttria-zirconia, magnesia-zirconia, zirconia-titania, titania-alumina, silica-magnesia, lanthana-zirconia, and scandia-zirconia.

[0023] <Reaction conditions> In the production method of the present invention, the molar ratio of acetaldehyde to methanol used as raw materials is preferably [acetaldehyde] / [methanol]=1 / 10 to 5 / 1, more preferably [acetaldehyde] / [methanol]=1 / 5 to 2 / 1, and even more preferably [acetaldehyde] / [methanol]=1 / 3 to 1 / 1.

[0024] In the production method of the present invention, the reaction temperature of acetaldehyde and methanol in the presence of a metal oxide catalyst is preferably 100 to 400°C, more preferably 150 to 350°C, and even more preferably 200 to 300°C.

[0025] In the production method of the present invention, the reaction between acetaldehyde and methanol is usually a gas reaction. For example, the target mid-chain branched saturated alcohol compound can be produced by passing a mixed gas obtained by vaporizing acetaldehyde and methanol through a column packed with a metal oxide catalyst (solid catalyst) to contact the mixed gas with the metal oxide catalyst (causing a catalytic reaction in a gas-phase flow reaction system). In the gas-phase flow reaction system, it is preferable to pass an inert gas such as a rare gas or nitrogen gas in addition to the mixed gas to react acetaldehyde and methanol under an inert atmosphere, but it is not necessary to pass an inert gas. A preferred embodiment of the gas-phase flow reaction system is described in the section "Examples" below.

[0026] [Mid-chain branched saturated alcohol compounds] The production method of the present invention can produce one or more branched saturated alcohol compounds having 3 to 10 carbon atoms. In the production method of the present invention, the branched saturated alcohol compound having 3 to 10 carbon atoms produced by the catalytic reaction preferably includes isobutanol (isobutyl alcohol). Furthermore, the proportion of isobutanol in all alcohol-aldehyde compounds having 3 to 10 carbon atoms produced by the catalytic reaction (all alcohol compounds having 3 to 10 carbon atoms and aldehyde compounds having 3 to 10 carbon atoms, regardless of whether they have a chemical structure such as saturated, unsaturated, linear, or branched, and regardless of whether they are monoalcohols, monoaldehydes, or polyhydric alcohols or polyaldehydes) is preferably 50% or more by carbon weight, more preferably 55% or more by carbon weight, even more preferably 60% or more by carbon weight, even more preferably 65% ​​or more by carbon weight, and even more preferably 70% or more by carbon weight. When the goal is to produce isobutanol, the higher this proportion, the better. The proportion of isobutanol in all alcohol / aldehyde compounds having 3 to 10 carbon atoms produced by the catalytic reaction may be 98% or less by carbon weight, 95% or less by carbon weight, 90% or less by carbon weight, or 85% or less by carbon weight. Preferred ranges for the proportion of isobutanol in all alcohol / aldehyde compounds having 3 to 10 carbon atoms produced by the catalytic reaction are 50 to 100% by carbon weight, 55 to 98% by carbon weight, 60 to 95% by carbon weight, 65 to 90% by carbon weight, and 70 to 85% by carbon weight. The term "% by carbon weight" refers to the percentage of the total number of carbon atoms in all isobutanol produced by the catalytic reaction relative to the total number of carbon atoms in all alcohol / aldehyde compounds having 3 to 10 carbon atoms produced by the catalytic reaction. Here, "all alcohols and aldehydes having 3 to 10 carbon atoms produced by the catalytic reaction" refers to all alcohols and aldehydes having 3 to 10 carbon atoms in the reaction product after the catalytic reaction using the metal oxide catalyst, but before the reaction product is subjected to separation and purification treatment, in the case where branched saturated alcohols having the desired carbon number are separated and purified as described below after the catalytic reaction using the metal oxide catalyst. In the production method of the present invention, in addition to the branched saturated alcohol compound having 3 to 10 carbon atoms, a certain amount of by-products (by-products) such as alcohol compounds other than the branched saturated alcohol compound having 3 to 10 carbon atoms, aldehyde compounds, ester compounds, etc. may be produced by the catalytic reaction. By separating and removing such by-products as necessary, the target mid-chain branched saturated alcohol compound can be obtained with high purity. Alternatively, a branched saturated alcohol compound having the target carbon number may be separated and purified from the multiple branched saturated alcohol compounds having 3 to 10 carbon atoms produced by the catalytic reaction. Therefore, the production method of the present invention may include a step of separating and purifying the target mid-chain branched saturated alcohol compound from the reaction product of the catalytic reaction after the catalytic reaction. The method for separating and purifying the target mid-chain branched saturated alcohol compound is not particularly limited, and any general separation and purification method can be appropriately adopted. Examples of such methods include fractional distillation, which utilizes differences in boiling points between alcohol compounds; liquid-liquid extraction, which selectively extracts a target alcohol compound into a solvent; crystallization, which precipitates a target alcohol compound as crystals; membrane separation, which uses a separation membrane to separate components by utilizing differences in molecular size, solubility, and chemical affinity; and preparative purification, which utilizes chromatography.

[0027] In the production method of the present invention, the higher the proportion of branched saturated alcohol compounds having 3 to 10 carbon atoms produced by the catalytic reaction in the total reaction products produced by the catalytic reaction, the better; however, a certain amount of by-products is usually produced. Therefore, this proportion is usually 10 to 90% by carbon weight, and 20 to 85% by carbon weight is more practical. Note that the "total reaction products produced by the catalytic reaction" used as the basis for calculating the above proportion includes by-products but does not include raw materials remaining after the catalytic reaction. The "% by carbon weight" refers to the proportion (%) of the total number of carbon atoms contained in the branched saturated alcohol compounds having 3 to 10 carbon atoms produced by the catalytic reaction to the total number of carbon atoms contained in all reaction products produced by the catalytic reaction. In addition to the branched saturated alcohol compound having 3 to 10 carbon atoms, the catalytic reaction in the production method of the present invention may produce, as by-products, for example, aldehyde compounds, saturated hydrocarbons, unsaturated hydrocarbons, and alcohol compounds other than the branched saturated alcohol compound having 3 to 10 carbon atoms. Furthermore, ester compounds such as ethyl acetate and methyl acetate may also be produced as by-products.

[0028] [Mid-chain branched saturated alcohol compound production system] The production system for a mid-chain branched saturated alcohol compound of the present invention (hereinafter also referred to as the "production system of the present invention") includes a reactor A that oxidizes ethanol to obtain acetaldehyde, and a reactor B that reacts the acetaldehyde with methanol in the presence of a metal oxide catalyst to obtain a branched saturated alcohol compound having 3 to 10 carbon atoms. That is, in the upstream stage of the reaction system, reactor A oxidizes ethanol to obtain acetaldehyde, and this acetaldehyde is supplied to reactor B in the downstream stage, where acetaldehyde and methanol are reacted in the presence of a metal oxide catalyst. The production system of the present invention is a reaction system suitable for carrying out the production method of the present invention in an embodiment in which the production method of the present invention includes a step of oxidizing ethanol to obtain acetaldehyde as described above.

[0029] The reactor A is not particularly limited as long as it can oxidize ethanol to obtain acetaldehyde. The reaction of oxidizing ethanol to obtain acetaldehyde is known as described above, and a known reactor A for oxidizing ethanol to obtain acetaldehyde can also be used as appropriate. For example, a reactor in which ethanol is continuously supplied and flows through a reaction tube filled with a solid catalyst can be used as the reactor A.

[0030] The reactor B is not particularly limited as long as it can react the acetaldehyde obtained in the reactor A with methanol in the presence of a metal oxide catalyst to produce a branched saturated alcohol compound having 3 to 10 carbon atoms. For example, the gas-phase flow reaction system described above is suitable as the reactor B.

[0031] The ethanol, methanol, and metal oxide catalyst used in the production system of the present invention have the same meanings as the ethanol, methanol, and metal oxide catalyst described in the production method of the present invention, and the preferred forms are also the same. Therefore, the branched saturated alcohol compounds having 3 to 10 carbon atoms produced in reactor B preferably contain isobutanol. Furthermore, the proportion of isobutanol in all alcohol-aldehyde compounds having 3 to 10 carbon atoms produced in reactor B is preferably 50% or more by carbon weight, more preferably 55% or more by carbon weight, even more preferably 60% or more by carbon weight, even more preferably 65% ​​or more by carbon weight, and even more preferably 70% or more by carbon weight. When the objective is to obtain isobutanol, the higher this proportion, the better. The proportion of isobutanol in all alcohol-aldehyde compounds having 3 to 10 carbon atoms produced by the catalytic reaction may be 98% or less by carbon weight, 95% or less by carbon weight, 90% or less by carbon weight, or 85% or less by carbon weight. The proportion of isobutanol in all alcohol-aldehyde compounds having 3 to 10 carbon atoms produced by the catalytic reaction is preferably in the range of 50 to 100% by carbon weight, more preferably 55 to 98% by carbon weight, even more preferably 60 to 95% by carbon weight, even more preferably 65 to 90% by carbon weight, and even more preferably 70 to 85% by carbon weight.

[0032] The proportion of branched saturated alcohol compounds having 3 to 10 carbon atoms in the total reaction products produced in the reactor B is usually 10 to 90% by carbon amount, and practically 20 to 85% by carbon amount.

[0033] The production system of the present invention may appropriately include other devices in addition to the reactor A and the reactor B. For example, a device for separating and purifying the target mid-chain branched saturated alcohol compound may be appropriately included downstream of the reactor B. [Example]

[0034] The present invention will be described in more detail based on examples. The present invention is not to be construed as being limited to the following examples except as defined in the present invention.

[0035] [Production of medium-chain branched saturated alcohol compounds] Example 1 Using the gas-phase flow reaction system shown in FIG. 1, a mid-chain branched saturated alcohol compound was produced as follows. A mixture of acetaldehyde and methanol ([acetaldehyde] / [methanol] = 1 / 2, molar ratio) was sent into the flow channel and vaporized by heating to 120°C in a vaporizer. Argon gas was introduced into another flow channel at a rate of 20 cm 3 The gas was introduced at a flow rate of 0.02g / min. Both flow paths were joined, and this gas (a mixture of acetaldehyde, methanol, and argon gas, also referred to as the feed gas) was passed through a column (300°C) packed with 0.8g of zirconia (ZrO2, sample name: JRC-ZRO-7, manufactured by Daiichi Kigenso Kagaku Kogyo Co., Ltd.) as a catalyst, causing a catalytic reaction. One hour after the start of the reaction, the gas that had passed through the column was analyzed directly by gas chromatography to determine the component composition of the reaction product. The time the mixed gas flowed through the column (contact time with the catalyst) was 0.02g-catalyst·min / ml-feed gas. The results of gas chromatography are shown in Figure 2. In Figure 2, the horizontal axis represents retention time (minutes). In Figure 2, "MeOH" represents methanol "C 2,ald " is acetaldehyde, " iso-C 4,alc " indicates isobutanol, and "MA" indicates by-product methyl acetate. As shown in Figure 2, it can be seen that isobutanol can be obtained highly efficiently and selectively by reacting acetaldehyde and methanol using zirconia as a catalyst. In Example 1, the proportion of isobutanol in all alcohol-aldehyde compounds having 3 to 10 carbon atoms produced by the catalytic reaction was approximately 75% by carbon weight. Furthermore, the proportion of branched saturated alcohol compounds having 3 to 10 carbon atoms produced by the catalytic reaction in all reaction products produced by the catalytic reaction was approximately 67% by carbon weight. The results of Example 1 are shown in the table below alongside the results of Examples 2 to 7.

[0036] <Reference example 1> A catalytic reaction was carried out in the same manner as in Example 1, except that ethanol was used instead of acetaldehyde. The results are shown in Figure 3. In Figure 3, "EtOH" represents ethanol. As shown in Figure 3, even when ethanol and methanol were reacted using zirconia as a catalyst, no mid-chain branched saturated alcohol compounds were produced.

[0037] <Reference example 2> A catalytic reaction was carried out in the same manner as in Reference Example 1, except that zirconia carrying copper (elementary copper) (copper-supported zirconia, copper content 2% by mass (product subjected to hydrogen reduction at 300°C)) was used as the catalyst instead of zirconia. The results are shown in Figure 4. In Figure 4, the three peaks of "C3" are, from the left, propionaldehyde, methyl acetate, and n-propanol. The four peaks of "C4" are, from the left, isobutyraldehyde, n-butyraldehyde, isobutanol, and n-butanol. 5+ The "C4" peak is a composite peak consisting of pentanol and other compounds. The largest of the four "C4" peaks is isobutanol. As shown in Figure 4, when ethanol is used instead of acetaldehyde and reacted with methanol, medium-chain alcohol compounds, including isobutanol, can be obtained by using copper-supported zirconia as a catalyst. However, this catalytic reaction had low selectivity for the reaction products, and many medium-chain alcohol compounds and medium-chain aldehyde compounds were produced in addition to isobutanol. In Reference Example 2, the proportion of isobutanol among all alcohols and aldehyde compounds with 3 to 10 carbon atoms produced by the catalytic reaction was approximately 44% by carbon weight.

[0038] <Reference example 3> A catalytic reaction was carried out in the same manner as in Example 1, except that zirconia carrying copper (elementary copper) (copper-supported zirconia, copper content 2 mass% (product subjected to hydrogen reduction at 300°C)) was used as the catalyst instead of zirconia. The results are shown in Figure 5. As shown in Figure 5, when acetaldehyde and methanol are reacted, a certain amount of medium-chain alcohol compounds, including isobutanol, can be obtained even when copper-supported zirconia is used as the catalyst instead of zirconia. However, the selectivity of the reaction product in this catalytic reaction was low, and many medium-chain alcohol compounds and medium-chain aldehyde compounds were produced in addition to isobutanol. In Reference Example 3, the proportion of isobutanol among all alcohols and aldehyde compounds with 3 to 10 carbon atoms produced by the catalytic reaction was approximately 31% by carbon weight.

[0039] <Examples 2 to 7> A catalytic reaction was carried out in the same manner as in Example 1, except that the metal oxide catalysts shown in the table below were used instead of zirconia as the catalyst. The results are shown in the table below. In Examples 2 to 7, the proportion of isobutanol in all alcohol-aldehyde compounds having 3 to 10 carbon atoms produced by the catalytic reaction was approximately 70% by carbon weight in Example 2, approximately 86% by carbon weight in Example 3, approximately 99% by carbon weight in Example 4, approximately 99% by carbon weight in Example 5, approximately 74% by carbon weight in Example 6, and approximately 99% by carbon weight in Example 7. The proportion of branched saturated alcohol compounds having 3 to 10 carbon atoms produced by the catalytic reaction in all reaction products produced by the catalytic reaction was approximately 60% by carbon weight in Example 2, approximately 83% by carbon weight in Example 3, approximately 24% by carbon weight in Example 4, approximately 85% by carbon weight in Example 5, approximately 20% by carbon weight in Example 6, and approximately 82% by carbon weight in Example 7.

[0040] [Table 1]

[0041] As shown in the table above, it was found that any type of metal oxide catalyst, whether basic metal oxide, amphoteric metal oxide, acidified metal oxide, or composite metal oxide, can be used to efficiently produce branched saturated alcohol compounds having 3 to 10 carbon atoms using acetaldehyde and methanol as raw materials. It was also shown that metal oxide catalysts selectively enhance the production of isobutanol among branched saturated alcohol compounds having 3 to 10 carbon atoms.

Claims

1. A method for producing a mid-chain branched saturated alcohol compound, comprising reacting acetaldehyde with methanol in the presence of a metal oxide catalyst to produce a branched saturated alcohol compound having 3 to 10 carbon atoms.

2. 2. The method for producing a mid-chain branched saturated alcohol compound according to claim 1, wherein the branched saturated alcohol compound having 3 to 10 carbon atoms produced by the reaction contains isobutanol.

3. 3. The method for producing a mid-chain branched saturated alcohol compound according to claim 2, wherein the proportion of isobutanol in all alcohol-aldehyde compounds having 3 to 10 carbon atoms produced by the reaction is 50% or more based on the carbon amount.

4. The method for producing a mid-chain branched saturated alcohol compound according to any one of claims 1 to 3, wherein a mixed gas of the acetaldehyde and the methanol is contacted with the metal oxide catalyst.

5. The method for producing a mid-chain branched saturated alcohol compound according to claim 4, comprising oxidizing ethanol to obtain the acetaldehyde.

6. The method for producing a mid-chain branched saturated alcohol compound according to claim 5 , wherein the ethanol includes bioethanol.

7. The method for producing a mid-chain branched saturated alcohol compound according to claim 4, wherein the methanol comprises green methanol.

8. A system for producing a mid-chain branched saturated alcohol compound, comprising: a reactor A for oxidizing ethanol to produce acetaldehyde; and a reactor B for reacting the acetaldehyde with methanol in the presence of a metal oxide catalyst to produce a branched saturated alcohol compound having 3 to 10 carbon atoms.

9. 9. The system for producing a mid-chain branched saturated alcohol compound according to claim 8, wherein the branched saturated alcohol compound having 3 to 10 carbon atoms produced in the reactor B includes isobutanol.

10. 10. The system for producing a mid-chain branched saturated alcohol compound according to claim 9, wherein a proportion of isobutanol in all alcohol / aldehyde compounds having 3 to 10 carbon atoms produced in the reaction apparatus B is 50% or more based on the carbon amount.

11. A metal oxide catalyst containing a metal oxide but not containing an elemental metal, for catalyzing a reaction for producing branched saturated alcohol compounds having 3 to 10 carbon atoms using acetaldehyde and methanol as raw materials.

12. 12. The metal oxide catalyst according to claim 11, wherein the branched saturated alcohol compound having 3 to 10 carbon atoms comprises isobutanol.

13. 13. The metal oxide catalyst according to claim 12, wherein the proportion of isobutanol in all alcohol / aldehyde compounds having 3 to 10 carbon atoms produced in the production reaction is 50% or more based on the carbon amount.

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