Method for producing aldehyde

Abstract

To provide a method for producing an aldehyde by reacting a raw material olefin with H2 and CO in the presence of an Rh complex catalyst having tris(2,4-di-tert-butylphenyl)phosphite as a ligand, where aldehyde is produced in high yield after reducing an amount of the catalyst used.SOLUTION: Provided is a method for producing an aldehyde by a hydroformylation reaction where a C2 or higher raw material olefin is reacted with hydrogen and carbon monoxide in the presence of a catalyst, where a rhodium complex catalyst having tris(2,4-di-tert-butylphenyl)phosphite as a ligand is used as the catalyst, and an H2 / CO molar ratio in a reactor is set larger than 1.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a method for producing an aldehyde by subjecting a raw material olefin to a hydroformylation reaction with hydrogen and carbon monoxide in the presence of a rhodium complex catalyst having a specific organophosphorus compound as a ligand.

Background Art

[0002] The hydroformylation reaction for producing an aldehyde by reacting a raw material olefin with hydrogen and carbon monoxide in the presence of a transition metal of Groups 8 to 10 of the periodic table and a ligand derived from an organophosphorus compound is widely known (for example, Patent Document 1). This hydroformylation reaction is also referred to as the "oxo reaction", and the mixed gas of hydrogen (H2) and carbon monoxide (CO) used in the reaction is called "oxo gas".

[0003] As ligands for the metal complex catalysts used in this reaction, various organophosphorus compounds have been proposed. For example, many compounds such as triphenylphosphine, tris(2,4-di-tert-butylphenyl) phosphite (hereinafter sometimes abbreviated as "DBPO"), and cyclodiphenylphosphine are known (Patent Document 2). Depending on the type of this ligand, the n / i ratio (linear aldehyde / branched aldehyde molar ratio) of the resulting aldehyde changes, and thus it is selectively used according to the purpose. For example, with triphenylphosphine, the n / i ratio is 10, and with DBPO, an aldehyde is produced in which the linear aldehyde and the branched aldehyde having an n / i ratio of about 1 to 2 are substantially equal. Therefore, when it is desired to produce an aldehyde having an n / i ratio of approximately 1, a metal complex catalyst having DBPO as a ligand, particularly a rhodium complex catalyst, is used from the viewpoint of catalytic activity.

[0004] In the hydroformylation reaction, since one mole each of H2 and CO is added to the double bond of the raw material olefin to form an aldehyde, as the oxo gas, a gas having H2:CO = 1:1 (molar ratio) is usually used.

Prior Art Documents

Patent Document

[0005]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0006] Not limited to a rhodium complex catalyst using DBPO as a ligand, no matter what ligand is used, since rhodium is an expensive metal, it is desired that the amount of catalyst used for the olefin as a substrate is small enough. Generally, in the hydroformylation reaction using a rhodium complex catalyst, in order to suppress the loss of the catalyst as much as possible, a rhodium recovery process is provided, and rhodium is recovered, regenerated, and reused after the reaction. However, by reducing the amount of catalyst used for the substrate, this rhodium recovery process can be omitted, and the labor, cost, and time required for recovery can be reduced. In addition, when the catalyst is recovered and reused, high-boiling by-products that are difficult to separate are also recycled, and these may accumulate in the reaction system and reduce the reaction activity. However, by eliminating the rhodium recovery process itself, such problems can also be avoided.

[0007] An object of the present invention is to provide a method for producing an aldehyde by subjecting a raw material olefin to a hydroformylation reaction with H2 and CO in the presence of a rhodium complex catalyst using DBPO as a ligand, while reducing the amount of catalyst used and producing the aldehyde in a high yield.

Means for Solving the Problems

[0008] As a result of repeated studies by the present inventors to solve the above problems, in the hydroformylation reaction using a rhodium complex catalyst having DBPO as a ligand, the reaction rate can be significantly improved by increasing the H2 concentration of the oxo gas, which has conventionally been H2:CO = 1:1 (molar ratio), and aldehydes can be produced in high yields while significantly reducing the amount of catalyst. That is, the gist of the present invention is as follows.

[0009] [1] In a method for producing an aldehyde by a hydroformylation reaction in which a raw material olefin having 2 or more carbon atoms is reacted with hydrogen and carbon monoxide in the presence of a catalyst, a rhodium complex catalyst having tris(2,4-di-tert-butylphenyl) phosphite as a ligand is used as the catalyst, and the hydrogen / carbon monoxide molar ratio in the reactor is made greater than 1. A method for producing an aldehyde, characterized by this.

[0010] [2] The method for producing an aldehyde according to [1], wherein the hydrogen / carbon monoxide molar ratio is 2 to 4.

[0011] [3] The method for producing an aldehyde according to [1] or [2], wherein the molar ratio of the linear aldehyde to the branched aldehyde in the produced aldehyde is 1.2 to 1.4. [Effect of the Invention]

[0012] According to the present invention, in a method for producing an aldehyde by subjecting a raw material olefin to a hydroformylation reaction with H2 and CO in the presence of a rhodium complex catalyst having DBPO as a ligand, aldehydes can be produced in high yields while reducing the amount of catalyst used. [Embodiments for Carrying Out the Invention]

[0013] Hereinafter, the present invention will be described in detail.

[0014] The method for producing an aldehyde according to the present invention is characterized in that, when producing an aldehyde by subjecting a raw material olefin to hydroformylation reaction with hydrogen (H2) and carbon monoxide (CO), which are oxo gases, in the presence of a rhodium (Rh) complex catalyst having tris(2,4-di-tert-butylphenyl) phosphite (DBPO) as a ligand, the H2 / CO molar ratio of the oxo gas in the reactor is made greater than 1.

[0015] <Mechanism> According to the present invention, the reason why an aldehyde can be produced in a high yield with a reduced amount of catalyst by making the H2 / CO molar ratio greater than 1 is presumably that, in the case of a rhodium complex catalyst having DBPO as a ligand, the addition of H2 to rhodium becomes the rate-determining step and dominates the reaction rate, and thus the reaction rate is greatly improved when the H2 concentration in the oxo gas is increased.

[0016] <Rh complex catalyst> The Rh complex catalyst used in the present invention may be any one having DBPO as a ligand. The ligand of the Rh complex catalyst may be only DBPO, or DBPO and other compounds may be used. There is no particular limitation on other ligands used together with DBPO, and examples thereof include cyclohexyldiphenylphosphine and tri-p-tolylphosphine. However, in order to more effectively obtain the effects according to the present invention, it is preferable to use only DBPO as the ligand.

[0017] In addition, as the raw material compound (Rh source) of the Rh complex catalyst, for example, rhodium acetate [Rh(OAc)3], rhodium acetylacetonate dicarbonyl [Rh(AcAc)(CO)2], rhodium acetylacetonate carbonyl triphenylphosphine [Rh(AcAc)(CO)(TPP)], hydrido carbonyl tri(triphenylphosphine) rhodium [HRh(CO)(TPP)3], one or more of these may be mentioned. Among these, raw material compounds that do not have phosphine or phosphite-based ligands, such as rhodium acetate [Rh(OAc)3] and rhodium acetylacetonate dicarbonyl [Rh(AcAc)(CO)2], are preferable because the effect of DBPO can be utilized when reacted with DBPO to form an Rh complex catalyst.

[0018] <Hydroformylation reaction> In the method for producing an aldehyde of the present invention, DBPO and the aforementioned raw material compound may be premixed and then supplied to the reactor, or DBPO and the aforementioned raw material compound may be separately supplied to the reactor. From these supplied compounds, a complex catalyst such as RhH(CO)(DBPO) is formed in the reactor. Further, in the presence of the catalyst, a raw material olefin, H2, and CO are supplied to the reactor, and an aldehyde is produced by performing a hydroformylation reaction.

[0019] As the raw material olefin of the present invention, usually, a linear or branched α-olefin or an internal olefin is used, preferably an olefin having 2 to 8 carbon atoms. Specifically, ethylene, propylene, 1-butene, 1-hexene, 1-octene, 1-dodecene, 1-tetradecene, etc. may be mentioned, and more preferably ethylene, propylene, or 1-butene. A particularly preferred olefin is propylene.

[0020] H2 and CO used in the present invention may be separately supplied to the reactor or may be supplied to the reactor together as a pre-mixed oxo gas before being supplied to the reactor. For example, a gas generated by a reformer or the like, or H2 and CO may be separated from these gases and supplied to the reactor.

[0021] In the present invention, it is characterized in that the H2 / CO molar ratio of the oxo gas in the reactor is made greater than 1. From the viewpoint of the effect of improving the reaction rate, the H2 / CO molar ratio is preferably 1.1 or more, more preferably 1.5 or more, and still more preferably 2 or more. On the other hand, if the H2 / CO molar ratio is too large, the hydrogen addition reaction to olefins proceeds and alkanes are generated, resulting in a decrease in the selectivity of the target product. Therefore, the H2 / CO molar ratio is preferably 8 or less, more preferably 6 or less, and still more preferably 4 or less.

[0022] Also, the oxo gas may contain substances other than H2 and CO. What may be contained is not particularly limited, but for example, nitrogen etc., and the amount thereof is about 1%.

[0023] The supply amount of the oxo gas is not particularly limited as long as it is an amount sufficient to convert the raw material olefin into an aldehyde by the hydroformylation reaction. For example, in the case of a completely mixed tank type reactor, 2.1 T / H may be supplied with respect to the feed amount of the raw material olefin to the reactor of 1 T / H.

[0024] In the present invention, the amount of the catalyst used in the hydroformylation reaction is about 0.1 to 50 weight ppm as the Rh concentration in the hydroformylation reaction solution, and it is also possible to carry out the reaction even at a low Rh concentration of 0.5 to 1 weight ppm. Also, the DBPO concentration is usually 10 to 500 mol / mol, preferably 25 to 300 mol / mol, and particularly preferably 50 to 250 mol / mol with respect to Rh.

[0025] Generally, when the amount of catalyst used is small, the reaction does not proceed. Therefore, in the conventional method, the Rh concentration in such a hydroformylation reaction solution is usually about 100 to 200 ppm by weight, and the ligand concentration is usually 10 to 500 mol / mol, preferably 25 to 300 mol / mol, particularly preferably 50 to 250 mol / mol with respect to Rh. However, in the present invention, due to the promoting effect of the hydroformylation reaction by making the H2 / CO molar ratio of the oxo gas in the reactor greater than 1, the amount of catalyst can be significantly reduced to 1 / 2000 to 1 / 2 of the conventional method, for example, the Rh concentration can be reduced to 0.1 to 50 ppm by weight. Further, the ligand concentration can also be reduced with the reduction of the Rh concentration. Due to the significantly smaller amount of Rh complex catalyst and ligand compared to the conventional method, the Rh recovery process after the reaction can be made unnecessary.

[0026] According to the present invention, even if the catalyst is not recovered, regenerated and reused by the Rh recovery process, since the amount of catalyst used is extremely small, almost no disadvantage due to catalyst loss occurs.

[0027] The temperature of the hydroformylation reaction is usually 20°C or higher, preferably 40°C or higher, more preferably 50°C or higher, and usually 300°C or lower, preferably 200°C or lower, more preferably 150°C or lower. If the reaction temperature is too low, the reaction rate becomes slow and the reaction does not proceed sufficiently. If the reaction temperature is too high, the formation of by-products is promoted and the catalyst may be deactivated.

[0028] The pressure of the hydroformylation reaction is usually 0.0001 MPaG or higher, preferably 0.01 MPaG or higher, more preferably 0.2 MPaG or higher, and usually 50 MPaG or lower, preferably 3 MPaG or lower, more preferably 20 MPaG or lower. If the reaction pressure is too low, the reaction rate becomes slow and the reaction does not proceed sufficiently. If the reaction pressure is too high, the design pressure of equipment such as the reactor increases and the equipment burden increases.

[0029] Since H2 and CO in the reactor are consumed as the reaction proceeds, in the present invention, during the reaction, H2 and / or CO are appropriately supplied so that the gas phase in the reactor always maintains the aforementioned H2 / CO molar ratio.

[0030] The reaction time of the hydroformylation reaction is usually 1 minute or more, preferably 10 minutes or more, more preferably 20 minutes or more, and usually 24 hours or less, preferably 10 hours or less, more preferably 5 hours or less. If the reaction time is too short, the reaction does not proceed sufficiently, and if it is too long, the formation of high-boiling substances progresses. In the present invention, in order to more effectively obtain the effects of the present invention, it is preferable to keep the H2 / CO molar ratio of the oxo gas in the reactor greater than 1 at 10% or more, preferably 30% or more, more preferably 50% or more, still more preferably 80%, particularly preferably 90% or more of the reaction time.

[0031] The hydroformylation reaction is usually carried out in the presence of a solvent that is inert to the starting olefin and the aldehyde produced in the reaction. Examples of solvents that can be used in the hydroformylation reaction include aromatic hydrocarbons such as benzene, toluene, and xylene, aliphatic hydrocarbons such as hexane and octane, alicyclic hydrocarbons such as cyclohexane, alcohols such as butanol, octanol, and polyethylene glycol, ethers such as triglyme, and esters such as dioctyl phthalate. In addition, aldehydes produced in the reaction, and aldehyde condensates such as trimers and tetramers thereof can also be used. Furthermore, paraffins having the same number of carbon atoms as the starting olefin can also be used. For example, in the hydroformylation of propylene, it is preferable to use a mixture with toluene or an aldehyde condensate such as butyraldehyde or trimers and tetramers.

[0032] The type of reactor used in the hydroformylation reaction is not particularly limited, and a stirred tank type, a bubble column type, a tray column type, a tubular type, a gas stripping type, etc. can be used. Usually, an olefin as a raw material, an oxo gas, and a catalyst solution are continuously supplied to a continuous reactor, and the reaction is carried out under the above hydroformylation reaction conditions, but a batch reactor can also be used. Further, in order to keep the reaction temperature constant, it may have an internal coil, a jacket, an external heat exchanger, etc.

[0033] The reaction solution containing the aldehyde produced in the hydroformylation reaction is withdrawn from the reactor. The separation of the produced aldehyde from the reaction solution withdrawn from the reactor can be carried out by selecting any separation operation and apparatus such as distillation, evaporation, gas stripping, gas absorption, or extraction. Among these, separation by distillation is preferably used. In this case, using a distillation column, a component containing the produced aldehyde as a main component can be distilled out and separated from the top of the column. The conditions for distillation are not particularly limited, but usually, the bottom temperature is preferably 50 to 150°C. Also, the pressure inside the column is not particularly limited, but usually, it is preferably 0.01 to 0.1 MPa.

[0034] In this separation step of the produced aldehyde, any means and apparatus for recovering unreacted olefin from the reaction solution may be added. In that case, preferably, a countercurrent contact column or the like is used. A gas-liquid separator or the like may be appropriately provided between each apparatus.

[0035] In the conventional hydroformylation reaction of the present invention using an Rh complex catalyst having DBPO as a ligand, when the Rh complex catalyst is RhH(CO)(DBPO), the n / i ratio becomes 1.2 to 1.4, and an aldehyde in which linear aldehyde:branched aldehyde is approximately 1:1 can be obtained.

[0036] In the hydroformylation reaction of the present invention using an Rh complex catalyst having DBPO as a ligand, when the Rh complex catalyst is RhH(CO)(DBPO), the n / i ratio becomes 1.2 to 1.4, and an aldehyde in which linear aldehyde:branched aldehyde is approximately 1:1 can be obtained.

Example

[0037] The present invention will be described more specifically with reference to the following examples.

[0038] [Example 1] 0.0026 mmol of acetylacetonato carbonyl rhodium (Rh(AcAc)(CO)2) and 0.26 mmol of tris(2,4-di-tert-butylphenyl) phosphite (DBPO) were dissolved in butyraldehyde as raw material compounds of the Rh complex catalyst to prepare 95 g of a solution with an Rh concentration of 5 ppm by weight and a DBPO concentration of 0.29% by weight. 95 g of this solution was placed in a 200 ml autoclave reactor, and 9.2 g of propylene and oxo gas (molar ratio of H2 / CO = 2) were injected. The pressure in the reactor was maintained at 2 MPaG and the molar ratio of H2 / CO was maintained at 2, and the reaction was carried out for 1 hour with stirring at 90°C. After the reaction, the conversion rate of propylene was examined by gas chromatography. The conversion rate of propylene was 98.1%. The time taken for the conversion rate of propylene to reach 90% was approximately 19 minutes, and the reaction rate was 0.121 [1 / min]. Also, by gas chromatography, the molar ratio of n-butyraldehyde to i-butyraldehyde in the produced butyraldehyde was examined. It was found that n-butyraldehyde:i-butyraldehyde = 1.27:1, and it was confirmed that the linear and branched forms were produced in a ratio of approximately 1:1.

[0039] [Example 2] As raw material compounds of the Rh complex catalyst, 0.0026 mmol of acetylacetonato carbonyl rhodium (Rh(AcAc)(CO)2) and 0.26 mmol of tris(2,4-di-tert-butylphenyl) phosphite (DBPO) were dissolved in butyraldehyde to prepare 95 g of a solution with an Rh concentration of 5 ppm by weight and a DBPO concentration of 0.29% by weight. 95 g of this solution was placed in a 200 ml autoclave reactor, and 8.9 g of propylene and oxo gas (molar ratio of H2 / CO = 4) were injected. The pressure in the reactor was maintained at 2 MPaG and the molar ratio of H2 / CO was maintained at 4, and the reaction was carried out for 1 hour with stirring at 90 °C. After the reaction, by analyzing with gas chromatography, when the conversion rate of propylene was examined, the conversion rate of propylene was 98.0%. The time for the conversion rate of propylene to reach 90% was approximately 12 minutes, and the reaction rate was 0.192 [1 / min]. Also, by gas chromatography, when the molar ratio of n-butyraldehyde to i-butyraldehyde in the produced butyraldehyde was examined, it was found that n-butyraldehyde:i-butyraldehyde = 1.42:1, and it was confirmed that the linear and branched forms were produced at approximately 1:1.

[0040] [Example 3] As raw material compounds of the Rh complex catalyst, 0.0003 mmol of acetylacetonato carbonyl rhodium (Rh(AcAc)(CO)2) and 0.0258 mmol of tris(2,4-di-tert-butylphenyl) phosphite (DBPO) were dissolved in butyraldehyde to prepare 51 g of a solution with an Rh concentration of 0.25 ppm by weight and a DBPO concentration of 0.03% by weight. 51 g of this solution was placed in a 200 ml autoclave reactor, and 4.47 g of propylene and oxo gas (molar ratio of H2 / CO = 4) were injected. The pressure in the reactor was maintained at 2 MPaG and the molar ratio of H2 / CO was maintained at 4, and the reaction was carried out for 4.7 hours with stirring at 90 °C. After the reaction, the conversion rate of propylene was examined by gas chromatography. As a result, the conversion rate of propylene was 97.3%. The time taken for the conversion rate of propylene to reach 90% was approximately 203 minutes, and the reaction rate was 0.011 [1 / min]. Also, by gas chromatography, the molar ratio of n-butylaldehyde to i-butylaldehyde in the produced butylaldehyde was examined. As a result, n-butylaldehyde:i-butylaldehyde = 1.48:1, and it was confirmed that the linear and branched forms were produced in a ratio of approximately 1:1.

[0041] [Comparative Example 1] 0.0026 mmol of acetylacetonato carbonyl rhodium (Rh(AcAc)(CO)2) and 0.26 mmol of tris(2,4-di-tert-butylphenyl) phosphite (DBPO) were dissolved in butylaldehyde as raw material compounds of the Rh complex catalyst to prepare 95 g of a solution with an Rh concentration of 5 ppm by weight and a DBPO concentration of 0.29% by weight. 95 g of this solution was placed in a 200 ml autoclave reactor, and 8.9 g of propylene and oxo gas (molar ratio of H2 / CO = 1) were injected. The pressure in the reactor was maintained at 2 MPaG, and the molar ratio of H2 / CO was maintained at 1. The reaction was carried out at 90 °C with stirring for 1 hour. After the reaction, the conversion rate of propylene was examined by gas chromatography. As a result, the conversion rate of propylene was 97.9%. The time taken for the conversion rate of propylene to reach 90% was approximately 31 minutes, and the reaction rate was 0.074 [1 / min]. Also, by gas chromatography, the molar ratio of n-butylaldehyde to i-butylaldehyde in the produced butylaldehyde was examined. As a result, n-butylaldehyde:i-butylaldehyde = 1.18:1, and it was confirmed that the linear and branched forms were produced in a ratio of approximately 1:1.

[0042] [Comparative Example 2] As raw material compounds of the Rh complex catalyst, 0.46 mmol of tris(triphenylphosphine)hydridorhodium (RhHCO(TPP)3) and 93 mmol of triphenylphosphine (TPP) were dissolved in butyraldehyde to prepare 150 g of a solution with an Rh concentration of 245 ppm by weight and a TPP concentration of 13% by weight. 150 g of this solution was placed in a 250 ml autoclave reactor, and 10 g of propylene and oxo gas (molar ratio of H2 / CO = 1) were injected. The pressure in the reactor was maintained at 2 MPaG and the molar ratio of H2 / CO was maintained at 1, and the reaction was carried out for 2 hours with stirring at 110 °C. After the reaction, the conversion rate of propylene was examined by gas chromatography, and the conversion rate of propylene was 98.8%. The time taken for the propylene conversion rate to reach 90% was approximately 31 minutes, and the reaction rate was 0.086 [1 / min]. Also, by gas chromatography, the molar ratio of n-butyraldehyde to i-butyraldehyde in the produced butyraldehyde was examined, and it was found that n-butyraldehyde:i-butyraldehyde = 2.88:1, confirming that the linear and branched forms were produced in a ratio of approximately 3:1.

Claims

**Claim 1** A method for producing an aldehyde by a hydroformylation reaction in which a raw material olefin having 2 or more carbon atoms is reacted with hydrogen and carbon monoxide in the presence of a catalyst, wherein a rhodium complex catalyst having tris(2,4-di-tert-butylphenyl) phosphite as a ligand is used as the catalyst, the Rh concentration in the hydroformylation reaction solution is 0.1 to 50 ppm by weight, the hydrogen / carbon monoxide molar ratio in the reactor is made greater than 1, and the molar ratio of the linear aldehyde to the branched aldehyde in the produced aldehyde is 1.2 to 1.

48. **Claim 2** The method for producing an aldehyde according to claim 1, wherein the hydrogen / carbon monoxide molar ratio is 2 to 4. **Claim 3** The method for producing an aldehyde according to claim 1 or 2, wherein the molar ratio of the linear aldehyde to the branched aldehyde in the produced aldehyde is 1.2 to 1.

4. **Claim 4** The method for producing an aldehyde according to any one of claims 1 to 3, wherein the hydrogen / carbon monoxide molar ratio is 1.1 or more. **Claim 5** The method for producing an aldehyde according to claim 4, wherein the hydrogen / carbon monoxide molar ratio is 1.5 or more. **Claim 6** The method for producing an aldehyde according to claim 5, wherein the hydrogen / carbon monoxide molar ratio is 2 or more. **Claim 7** The method for producing an aldehyde according to any one of claims 1 to 6, wherein the Rh concentration in the hydroformylation reaction solution is 0.5 to 1 ppm by weight. **Claim 8** The method for producing an aldehyde according to any one of claims 1 to 7, wherein the raw material olefin is ethylene or propylene.