JP4736392B2 - Method for producing aldehyde - Google Patents

Description

  The present invention relates to a method for producing an aldehyde.

  Production of aldehydes using olefinic unsaturated compounds as raw materials has been carried out industrially on a large scale. Specifically, an olefinic unsaturated hydrocarbon is reacted with carbon monoxide and hydrogen (hydroformylation reaction) in the presence of a rhodium catalyst to produce a hydroformylation reaction liquid containing the corresponding linear and branched aldehydes. obtain. Usually, the catalyst is recovered from this reaction solution, and the aldehyde-containing reaction solution from which the catalyst has been removed is distilled to separate it into a linear aldehyde and a branched aldehyde.

In general, when an aldehyde-containing reaction solution is distilled to separate a linear aldehyde and a branched aldehyde, their boiling points are very close to each other, and the process is very energy consuming. For example, in Japanese Translation of PCT International Application No. 2002-540181 (Patent Document 1), as a method for reducing the amount of steam consumed when separating into linear aldehydes and branched aldehydes, separation is performed with two distillation columns under certain conditions. A method is disclosed. Japanese Examined Patent Publication No. 7-39365 (Patent Document 2) discloses a method of separation in a single distillation column under certain conditions. However, in these methods, the effect of suppressing the steam consumption when separating into a linear aldehyde and a branched aldehyde was not sufficient.
JP-T-2002-540181 Japanese Examined Patent Publication No. 7-39365

  The subject of this invention is providing the manufacturing method of the aldehyde which can suppress the steam consumption at the time of isolate | separating into a linear aldehyde and a branched aldehyde.

  As a result of intensive studies to solve the above problems, the present inventors have found that alcohol is present in the aldehyde-containing reaction solution to be used in the distillation column, and that the above problems can be solved by reducing the concentration of the alcohol, The present invention has been completed. That is, the gist of the present invention resides in the following (1) to (3).

(1) An olefinic unsaturated compound is allowed to flow into a reactor at a flow rate of 1 t / h or more, and hydroformylation reaction is performed to obtain an aldehyde-containing reaction solution. a method of obtaining, aldehyde production method, which comprises the alcohol concentration of the aldehyde-containing reaction mixture to be fed to the distillation column and 200ppm or less.
(2) Between the hydroformylation step of obtaining an aldehyde-containing reaction solution by subjecting an olefinically unsaturated compound to a hydroformylation reaction, and the distillation step of purifying the obtained aldehyde-containing reaction solution in a distillation column to obtain an aldehyde. method for producing an aldehyde according to the above which Ru is provided a step of removing alcohol from an aldehyde-containing reaction solution (1).
(3) Said (1) or (2) which has the process of removing olefinic unsaturated compounds other than carbon number n-1 (n is carbon number of the aldehyde as a product) from the olefinic unsaturated compound as a raw material. A method for producing an aldehyde as described in 1. above.

  ADVANTAGE OF THE INVENTION By this invention, the manufacturing method of the aldehyde which can suppress the steam consumption at the time of isolate | separating into a linear aldehyde and a branched aldehyde can be provided.

The present invention will be described in detail below.
In the method for producing an alcohol of the present invention, an olefinically unsaturated compound is allowed to flow into a reactor at 1 t / h or more to cause a hydroformylation reaction to obtain an aldehyde-containing reaction solution, and the obtained aldehyde-containing reaction solution is obtained in a distillation column. In the method of obtaining aldehyde by purification, the alcohol concentration in the aldehyde-containing reaction solution to be used in the distillation tower is 200 ppm or less.

Examples of the olefinic unsaturated compound used in the present invention include olefinic unsaturated hydrocarbons having 2 to 4 carbon atoms, and specific examples include ethylene, propylene, 1-butene, 2-butene, and isobutylene. Particularly preferred is propylene.
In the present invention, it is essential that the olefinically unsaturated compound is allowed to flow into the reactor at 1 t / h or more. However, this numerical situation of “1 t / h or more” has no special critical significance. It is a numerical value indicating that the invention is intended to be implemented at the industrialization level.
The aldehyde in the present invention is an aldehyde obtained by a hydroformylation reaction of a raw material olefinic unsaturated compound, and is an olefin having a carbon number of n-1 (n is the carbon number of the raw material olefin, for example, an integer of 4 or more). An aldehyde having n carbon atoms is obtained by a hydroformylation reaction of an unsaturated compound. In particular, butyraldehyde obtained by hydroformylation of propylene is preferable.

  The catalyst used in the hydroformyl reaction is not particularly limited as long as it is a catalyst known to be used in this application. For example, an eighth catalyst such as Co, Rh, Ir, Pd, Pt, Os or Ru is used. A metal (in the present invention, an eighth metal is a group metal in the periodic table of 1983 and a metal of group 8 to 10 in the current periodic table), preferably Co, Ru, Rh, Pd, and Pt, more preferably Co, Rh, and particularly Rh. In particular, rhodium alone or a combination of rhodium and a complex-forming ligand is used.

  As the complex salt-forming ligand, an organic phosphorus compound is usually used, for example, tertiary alkyl or aryl phosphine, tertiary alkyl or aryl phosphite. Examples of the phosphine compound include trialkylphosphine such as trimethylphosphine, triethylphosphine, tripropylphosphine, tributylphosphine, and trioctylphosphine; triarylphosphine such as triphenylphosphine and tritolylphosphine; diphenylpropylphosphine, phenyldipropylphosphine And tertiary alkylaryl phosphine. Examples of the phosphite compound include triethyl phosphite and triphenyl phosphite. Further, phosphines or phosphites having a hydrophilic substituent such as triphenylphosphine trisulfonic acid and triphenylphosphine monosulfonic acid, and salts thereof can also be used. However, in the present invention, the types of these organic phosphorus compounds are not limited at all.

  The amount of catalyst used in the hydroformylation reaction is such that the rhodium concentration in the hydroformylation reaction solution (metal conversion) is usually 100 wtppm or more, preferably 200 wtppm or more, usually 1000 wtppm or less, preferably 500 wtppm or less, particularly preferably 350 wtppm or less. . If the amount of the catalyst is too small, the desired reaction results cannot be obtained, and if it is too large, it is economically disadvantageous such as an increase in catalyst loss.

  The hydroformylation reaction is usually performed in the presence of a solvent inert to the aldehyde produced by the reaction with the raw material olefinic unsaturated compound. Examples of the solvent include aromatic compounds such as benzene, toluene and xylene, aliphatic hydrocarbons such as hexane, octane and cyclohexane, alcohols such as butanol, octanol and polyethylene glycol, ethers such as triglyme, esters such as dioctyl phthalate, and the like. . Moreover, the aldehyde produced | generated by reaction and aldehyde condensates, such as its trimer and a tetramer, can also be used. Furthermore, paraffin corresponding to the raw material olefin can also be used. For example, in the case of hydroformylation of propylene, toluene, butyraldehyde, or a mixture of these with a high-boiling substance by-produced by the reaction can be used.

The hydroformylation reaction is preferably carried out at a total partial pressure of hydrogen, carbon monoxide and olefinically unsaturated compound of less than 500 kg / cm ² G, particularly less than 200 kg / cm ² G. The lower limit of pressure is limited by the partial pressure required to achieve the desired reaction rate. Specifically, atmospheric pressure or higher is preferable.
The carbon monoxide partial pressure in the hydroformylation reaction is preferably 0.1 to 100 kg / cm ² , more preferably 1 to 7 kg / cm ² . If the carbon monoxide partial pressure is too low, the reaction is stopped, and if it is too high, the reaction rate decreases.

The hydrogen partial pressure is preferably 0.1 to 100 kg / cm ² , more preferably 1 to 8 kg / cm ² . If the hydrogen partial pressure is too low, the reaction will be terminated, and if it is too high, the paraffinization of the raw material olefin will increase.
In general, the molar ratio of hydrogen to carbon monoxide (H ₂ : CO) is preferably 1:10 to 10: 1, more preferably 5: 1 to 1: 5. In the hydroformylation reaction, the olefin, hydrogen, and carbon monoxide react in an equimolar amount. Therefore, if the molar ratio of hydrogen to carbon monoxide deviates significantly from 1: 1, the unreacted raw material gas increases.

The reaction temperature is preferably from room temperature to 150 ° C, particularly from 50 ° C to 120 ° C. If the temperature is too high, the catalytic activity may decrease.
The hydroformylation reaction can be carried out by a conventionally known method. Usually, the raw material olefinic unsaturated hydrocarbon, hydrogen, carbon monoxide and a catalyst solution are continuously supplied to a continuous reactor, and the reaction solution is supplied. This is done by continuously extracting. The reaction type may be a catalyst solution circulation type in which the catalyst solution is discharged out of the reactor together with the product, or a so-called gas strike in which the product is distilled with gas while the catalyst solution is confined in the reactor. A ripping type may also be used.

  In the case of a gas / liquid mixture or gas strip type leaving the reactor, the gaseous product is cooled if necessary, then a stream containing unreacted olefin and another stream, ie a stream containing an aldehyde-containing reaction liquid. And separated. The separation method varies depending on the boiling point of the olefin, but is performed by a conventionally known method such as gas stripping or distillation. Part or all of the separated unreacted olefin can be recycled to the reactor.

The flow containing the aldehyde-containing reaction solution is separated from the aldehyde-containing reaction solution and other components by a known method such as distillation, and when the catalyst contains other components as in the catalyst solution circulation type, it reacts as a catalyst solution. It can also be recycled into a container.
As a method for distilling the aldehyde-containing reaction liquid taken out by the above method and separating it into a linear aldehyde and a branched aldehyde, conventionally known methods can be used.

A tray column or a packed column can be used as the distillation column. The theoretical stage of the tray tower is usually preferably 40 to 200. The packed length of the packed column is preferably 15 to 100 m. The top pressure of the distillation column is not particularly limited. However, when the vacuum pressure is set, aldehyde loss due to non-condensation occurs in the top condenser using cooling water of about 20 to 30 ° C., so that the atmospheric pressure or higher is desirable. In this case, in the separation of the branched chain aldehyde and the straight chain aldehyde, atmospheric pressure is most desirable because the lower the pressure, the higher the relative volatility and the smaller the number of required theoretical plates. However, considering the equipment cost, the tower top temperature is raised by pressurization, and as a result, the heat transfer area of the tower top condenser can be reduced by taking a large temperature difference from the cooling water, so about 1.0 kg / cm ² G Although there is a slight increase in the number of theoretical plates required due to the deterioration of separation, the equipment cost does not increase so much and it is economically feasible. Therefore, the tower top pressure is preferably 0.001 to 1.0 kg / cm ² G. The temperature in the distillation column varies depending on the column pressure determined by the number of carbons of the aliphatic aldehyde, the column top pressure, the type of the distillation column, etc., and is about 62 ° C. to about 115 ° C. at the column top. About 76 ° C. to about 145 ° C. at the bottom.

  Distillation may be performed using a single distillation column or a plurality of distillation columns. When distillation is performed in a single distillation column, a branched aldehyde can be obtained from the top of the column or from a position above the stage to which the aldehyde-containing reaction solution is supplied, and the bottom of the column or from the position to which the aldehyde-containing reaction solution is supplied. A linear aldehyde can be obtained from the position. It is also possible to take out a branched aldehyde from the tower top, a linear aldehyde from the side stream, and a mixture of the linear aldehyde and the high-boiling substance from the tower bottom.

  When using a plurality of distillation towers, for example, high boiling point substances are removed from the bottom of the first tower, the distillate from the top of the tower is supplied to the second tower, and linear aldehyde is fed from the bottom of the second tower. , A method for obtaining a branched aldehyde from the top of the column, distilling a low-boiling substance from the top of the first column, supplying the bottoms from the low column to the second column, and straight chain from the bottom of the second column A branched aldehyde from the top of the tower, a branched aldehyde is obtained from the top of the first tower, the bottoms from the bottom of the tower are fed to the second tower, and Examples include a method for obtaining a linear aldehyde.

  In the present invention, in the distillation step for separating the linear aldehyde and the branched aldehyde (necessary to specify which distillation step), the alcohol concentration in the aldehyde-containing reaction solution supplied to the distillation tower is 200 ppm or less, preferably 100 ppm or less, More preferably, it is 20 ppm or less. When the alcohol concentration is high, the amount of steam consumed when the linear aldehyde and the branched aldehyde are separated by distillation increases. The alcohol concentration is preferably as low as possible, but is usually 10 ppb or more.

In addition, although it does not specifically limit with alcohol in the aldehyde containing reaction liquid in this invention, Specifically, methanol, ethanol, propanol, etc. are mentioned.
As a method of setting the alcohol concentration in the aldehyde-containing reaction solution to be used for distillation or the like to 200 ppm or less, (i) a hydroformylation step for obtaining an aldehyde-containing reaction solution by hydroformylating an olefinic unsaturated compound, and the obtained aldehyde A method of providing a step of removing alcohol from the aldehyde-containing reaction solution between the distillation step of purifying the reaction solution in a distillation column and obtaining an aldehyde, (ii) carbon number from the olefinic unsaturated compound as a raw material a method of providing a step of removing olefinic unsaturated compounds other than n-1 (where n is the number of carbon atoms of the aldehyde as a product), (iii) a solvent for adjusting a hydroformylation catalyst, or a solvent for recovering a hydroformylation catalyst That the alcohol used in the above solvent is hydroformyl Like reducing the amount being fed are exemplified in the reaction system.

  (I) Between a hydroformylation step for obtaining an aldehyde-containing reaction solution by hydroformylating an olefinically unsaturated compound and a distillation step for obtaining an aldehyde by purifying the obtained aldehyde-containing reaction solution in a distillation column, When providing the process of removing alcohol from an aldehyde containing reaction liquid, alcohol can be isolate | separated by general distillation, for example. If the alcohol contained in the aldehyde-containing reaction solution is a light-boiling component relative to the aldehyde-containing reaction solution, it can be separated from the top of the distillation tower together with other light-boiling components. If the alcohol is a high boiling component with respect to the aldehyde-containing reaction solution, it can be separated from the bottom of the distillation column together with other high boiling components. In addition, when the alcohol forms an azeotropic composition with the aldehyde-containing reaction solution, it is necessary to find the optimum point of the operating pressure.

  (Ii) When providing a step of removing olefinic unsaturated compounds other than carbon number n-1 (n is the number of carbons of the aldehyde as a product) from the olefinic unsaturated compound as a raw material, for example, general distillation Or a method of changing to paraffin by hydrogenation reaction, a method of combining distillation and hydrogenation reaction, or the like. Although there are no particular restrictions on the distillation conditions, since the raw material olefin is a liquefied gas, distillation is generally performed by pressurization. The pressure is desirably 1 MPaA or more. The catalyst for selectively partially hydrogenating the olefin as an impurity is a transition metal of the eighth metal of the periodic table, and Ni, Pd, Pt, etc. are used, and Ni and Pd are particularly preferable. When the distillation and the hydrogenation reaction are combined, the order is not limited, and the olefin purified by distillation may be hydrogenated to remove the impurity olefin, or the impurity olefin may be hydrogenated and then purified by distillation.

  (Iii) In the case where no alcohol is used as a solvent for adjusting the hydroformylation catalyst or a solvent for recovering the hydroformylation catalyst, for example, a solvent for adjusting the hydroformylation catalyst that replaces the alcohol is disclosed in JP-A-8-10624. In, fatty acids such as formic acid, acetic acid and propionic acid, cyclic ethers such as tetrahydrofuran and dioxane, lactones such as propiolactone and γ-butyrolactone, lower alkyl ketones such as acetone and methyl ethyl ketone, amines such as ethylamine and propioamine, and aldehydes such as acetaldehyde Is listed. In addition to the above, JP-A-10-291996 discloses aliphatic saturated hydrocarbons such as hexane and heptane, aromatic hydrocarbons such as benzene, toluene and xylene, and aliphatic non-carbon such as hexene, octene and nonene. Listed are saturated hydrocarbons, esters such as ethyl acetate, and mixtures thereof. Further, as a solvent for recovering the hydroformylation catalyst instead of alcohol, for example, in JP 2001-114794 A, polar compounds such as acetonitrile, N-methylpiperidone, diethyl ether, pentane, hexane, heptane, octane, etc. Lists nonpolar compounds. As a method of reducing the amount of alcohol used for catalyst preparation, for example, there is a method of increasing the catalyst concentration in the hydroformylation catalyst. Thereby, even if the same catalyst amount is fed into the oxo reaction system, the amount of accompanying alcohol can be reduced.

  It is not theoretically known why the required amount of steam increases when alcohol is included, but in the actual operation of the distillation tower, the presence of alcohol in the feed increases the required amount of steam, leading to the invention. .

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to the following examples.
<Hydroformylation reaction>
A hydroformylation reaction was carried out by feeding 7.0 t / h of propylene to a fully mixed tank reactor. Further, synthesis gas of H ₂ / CO = 1 was fed to the reactor so as to keep the reaction pressure. The reaction conditions were a temperature of 100 ° C., a pressure of 17 kg / cm ² G, an Rh concentration of 330 mg / L, and a triphenylphosphine concentration of 21 wt%. The produced hydroformylation reaction solution was separated into a catalyst solution and an aldehyde-containing reaction solution in a distillation column. The ratio of butyraldehyde to isobutyraldehyde in the aldehyde-containing reaction solution was 10.

Comparative Example 1
A catalyst solution was prepared by diluting 4 kg of Rh acetate having an Rh concentration of 10 wt% (in terms of Rh metal) with 1140 L of methanol. The catalyst solution was fed into the reaction system so that the catalyst concentration in the hydroformylation reaction was constant. In order to purify the aldehyde-containing reaction solution obtained by the hydroformylation reaction to obtain an aldehyde, it was fed to a distillation column having a tray having 75 stages. The methanol concentration in the fed aldehyde-containing reaction solution was 300 ppm. The top pressure of the distillation column was normal pressure, the top temperature was 67 ° C., the bottom temperature was 90 ° C., and the external reflux ratio was 53.

Example 1
Comparative Example 1 was performed except that a catalyst solution was prepared by diluting 60 kg of acetic acid Rh having a Rh concentration of 10 wt% (in terms of Rh metal) with 1140 L of methanol. At this time, the methanol concentration in the aldehyde-containing reaction solution fed to the distillation column was 19 ppm.
Example 2
Comparative Example 1 was performed except that a catalyst solution was prepared by diluting 12 kg of acetic acid Rh having a Rh concentration of 10 wt% (in terms of Rh metal) with 1140 L of methanol. At this time, the methanol concentration in the aldehyde-containing reaction solution fed to the distillation column was 95 ppm.

Claims (3)

A method of obtaining an aldehyde by flowing an olefinically unsaturated compound into a reactor at a flow rate of 1 t / h or more , causing a hydroformylation reaction to obtain an aldehyde-containing reaction solution, and purifying the obtained aldehyde-containing reaction solution in a distillation column. The method for producing an aldehyde according to claim 1, wherein the alcohol concentration in the aldehyde-containing reaction solution supplied to the distillation tower is 200 ppm or less. An aldehyde-containing reaction between a hydroformylation step in which an olefinic unsaturated compound is hydroformylated to obtain an aldehyde-containing reaction solution and a distillation step in which the obtained aldehyde-containing reaction solution is purified by a distillation tower to obtain an aldehyde method for producing aldehydes according to claim 1, Ru provided a step of removing alcohol from the liquid. From olefinically unsaturated compound as starting material, the production of aldehydes according to claim 1 or 2 comprising a step of removing the olefinically unsaturated compound other than (the number of carbon atoms of the aldehyde as a product n) number n-1 carbon Method.