JP4779294B2 - Method for producing alcohol - Google Patents

Description

  The present invention relates to a method for producing alcohol, and more specifically, in an alcohol production method obtained by hydrogenating and purifying an aldehyde, the alcohol content which can significantly reduce the concentration of aldehyde contained in the product alcohol as compared with the prior art. It is related with the manufacturing method.

  As a method for producing alcohol, a method in which an aldehyde is hydrogenated and purified to obtain a saturated alcohol is conventionally known and commercially available worldwide. For example, for saturated aldehydes, butanol is hydrogenated to butanol, nonyl aldehyde is hydrogenated to nonanol, and for unsaturated aldehydes, for example, 2-ethylhexenal is hydrogenated to 2-ethylhexanol, 2-propyl heptane. Hydrogenation to tenal can give 2-propylheptanol and hydrogenation to decenal to give decanol.

As a form of the hydrogenation reaction, it is common to use a reactor in which a nickel-based or copper-based solid hydrogenation catalyst is usually filled, and a form in which a raw material aldehyde is vaporized and reacted in a gas phase. There is a form in which the raw material aldehyde is introduced into the reactor in a liquid state and reacted in the liquid phase.
However, regardless of the type of catalyst and the gas phase / liquid phase reaction type, any conventional reaction process may cause esterification, acetalization, etherification, etc. as undesirable side reactions, reducing the selectivity of the reaction. In addition, there is a problem that in the subsequent process, a satisfactory product alcohol cannot be obtained unless these by-products are separated and removed and purified by distillation operation or the like.

For example, the following method has been proposed as a method for distillation purification of the crude alcohol.
First, after the low-boiling product is separated in the first column, the top pressure is operated in the second column, alcohol is distilled from the high-boiling product, and the alcohol product is distilled off from the top of the column. In this method, the pressure at the top of the column is manipulated to recover useful products in the high-boiling components (three-column system).

Specifically, in Patent Document 1 (Japanese Patent Publication No. 49-11365), in the above-mentioned three-column system, the second column has a top pressure of 200 to 800 mmHg and an alcohol content in the column bottom of 50 wt% or more. And a method of obtaining purified 2-ethylhexanol by operating the third column under conditions where the top pressure is 70 to 300 mmHg.
Also, a method of performing the first tower in two stages by the above-mentioned three-column system (four-column system), that is, after distilling and separating low-boiling substances in the first column, product alcohol is distilled in the second column, In the bottom liquid, the high-boiling substances are further concentrated in the third tower and separated from the bottom, and then the active components are recovered by distillation. In the fourth tower, the low-boiling substances separated in the first tower are further concentrated. Then, a method of distilling and separating and recovering active ingredients from the bottom of the column is also known.

  Further, in the second column for obtaining product alcohol, high-boiling components in the bottom liquid, particularly low-boiling products generated by thermal decomposition of acetal components, ether components, etc. are included in the alcohol product distilled off from the column top. In order to avoid this, the high-boiling component is separated in the first column, and a fraction containing a low-boiling component and alcohol and substantially not containing a high-boiling component is distilled from the top of the second column. Is also known in which a low-boiling component is separated from alcohol by distillation and a fraction containing the low-boiling component as a main component is distilled from the top of the column, while purified alcohol is distilled as a side stream (Patent Document). 2).

Furthermore, in the above-described two-column system, in the first tower for separating the high-boiling components, the tower bottom temperature is maintained at a value higher than the prescribed value and the high-boiling component concentration in the tower bottom liquid is maintained at 30 wt% or higher. A method of actively pyrolyzing boiling components and recovering them as active components is also disclosed (see Patent Document 3).
On the other hand, in general, product alcohol is mainly used as a plasticizer for resins such as vinyl chloride, so extremely high purity is required, and there is little coloration, that is, the sample is heated with sulfuric acid, and the degree of coloration is measured. Therefore, it is required that the degree of coloring by a sulfuric acid coloring test performed is small.

An aldehyde can be mentioned as a component that has a very strong influence on the sulfuric acid coloring test and the like, because the aldehyde is an unsaturated hydrocarbon. Therefore, the aldehyde concentration in the product alcohol is one of the most important product alcohol quality items, and is desirably reduced.
However, although the product alcohol obtained by the above-described prior art method contains a relatively large amount of aldehydes and is not sufficiently satisfactory as a product, in the above prior art, No attention is paid to the concentration of aldehyde contained in the product alcohol, and therefore, no method for reducing the concentration of the aldehyde is disclosed. Even if there is no particular disclosed technique, this can be attributed to the fact that the following can be presumed easily based on the common knowledge of those skilled in the art and chemical engineering.

  That is, as a method of reducing the concentration of aldehyde contained in product alcohol, 1) a method of increasing the conversion rate of aldehyde to alcohol in the hydrogenation reaction and reducing the amount of unreacted aldehyde brought into the purification system 2) In the purification system, in the step of separating the low-boiling components, a method of increasing the degree of separation of the aldehyde, which is a low-boiling component, by increasing the number of distillation columns, increasing the reflux ratio, or the like can be considered.

  Even in actual commercial operation, by changing the reaction temperature and other operating conditions, the decrease in the conversion rate of the aldehyde accompanying the decrease in the activity of the hydrogenation reaction catalyst over time can be suppressed and the amount of unreacted aldehyde brought into the purification system can be reduced. (I.e., the measure of the above 1)), or by increasing the reflux amount of the low-boiling component separation tower of the purification system or increasing the amount of distillate extracted (i.e., the measure of the above-mentioned 2)), It seems that the quality of the product alcohol, that is, the concentration of aldehyde contained in the product is maintained to be below the standard value.

However, it is very difficult to obtain alcohol with a low aldehyde concentration.
On the other hand, in the distillation purification of C3 to C10 alcohol, the production of the corresponding aldehyde has been confirmed by the heat load at the bottom of the distillation tower, and a method of distillation in the presence of alkali metal hydroxide is disclosed as a suppression means. (See Patent Document 4).

However, in this method, there is a problem that an additional facility for adding the alkali metal hydroxide is required, and the possibility of the addition of the additive into the product alcohol cannot be denied.
Japanese Patent Publication No.49-11365 JP-A-6-122638 JP-A-7-278032 Special table 11-1150037

In the long-term commercial operation, the inventors tried various operation adjustments using the above-described chemical engineering technique in order to reduce the concentration of aldehyde contained. However, no matter how much the conversion rate is increased by the hydrogenation reaction, or even if the separation rate of the low boiling point component is increased by the low boiling point component separation column which is a distillation column for separating the aldehyde from the product alcohol in the purification system. We experienced the difficulty that the aldehyde concentration in the product alcohol could not be reduced below a certain level.

  Product quality must be observed in preference to anything, so the aldehyde concentration in the product alcohol must be maintained at a predetermined low concentration. As an operation adjustment for that purpose, for the purpose of increasing the aldehyde conversion rate in the hydrogenation reaction, for example, the reaction conditions must be changed such as changing the reaction temperature to a higher temperature side, and as a result, the aldehyde conversion rate may increase. Since the by-product rate of high-boiling components also increases, a decrease in alcohol yield and an increase in purification and separation costs for high-boiling components are inevitable.

In addition, in the purification system, that is, to increase the degree of distillation separation of low-boiling components, it means increasing the reflux amount, distillate extraction amount, or increasing the number of distillation column theoretical plates, and the operating cost and equipment of the reboiler heat source. This means an increase in costs. These are significant increases that cannot be ignored economically.
Furthermore, by distilling at a pressure below atmospheric pressure, the aldehyde concentration in the product alcohol is kept below a certain amount even if the temperature at the bottom of the distillation column is reduced to 150 ° C. or less to suppress the formation of aldehyde due to heat load. Could not be reduced.

  That is, the present invention solves the above-described problems, and an object of the present invention is to obtain a high-purity alcohol by reducing the aldehyde concentration in the product alcohol efficiently and inexpensively.

  The inventors of the present invention discovered a surprising result as a result of collecting and analyzing plant data of actual commercial operation and examining the material balance of the plant precisely in order to examine drastic measures against the above-mentioned problems. That is, although the distillation tower bottom temperature is low and the heat load is small, the amount of unreacted aldehyde contained in the hydrogenated product brought into the purification system from the hydrogenation reaction system is smaller than that from the purification system. It has always been found that the sum of the amount of aldehydes in all effluent streams discharged out, ie aldehydes in the product and aldehydes in the separated low boiling component stream, is always much higher.

  This indicates that aldehyde is produced for some reason other than heat load in the purification system. Further, as a result of examining in more detail where it is produced, for example, in a system using a low-boiling component separation tower as the first tower and a product tower as the second tower, the first tower, which is a low-boiling component separation tower, is large. Despite separation and removal of part of the aldehyde from the top of the column, it was not separated in the first column, which was brought into the second column from the first column into the second column distillate product alcohol. It was found that the amount of aldehyde was several times the amount of remaining aldehyde.

That is, it was discovered that aldehyde was produced even inside the product tower with a small heat load.
As a result of examining the cause of aldehyde formation in the purification system of this commercial plant from various angles, the analysis of the bottom liquid of the purification system and the hydrogenation reaction product liquid fed from the hydrogenation reactor to the purification system By discovering the presence of crushed powder of hydrogenation catalyst and removing most of the powder of hydrogenation catalyst, we gained knowledge as a method that does not substantially produce aldehyde in the purification system, The present invention has been completed.

That is, the gist of the present invention resides in the following (1) to (7) .
(1) In an alcohol production method in which an aldehyde is hydrogenated using a hydrogenation reactor filled with a hydrogenation catalyst and the resulting hydrogenation reaction product is purified by distillation to obtain a product alcohol, the content in the product alcohol The aldehyde concentration is 0.05 wt% or less, and a process for removing the hydrogenation catalyst powder from the hydrogenation reaction product with a filter is provided between the hydrogenation process and the distillation purification process, and the hydrogenation after the catalyst removal process A method for producing an alcohol, wherein the concentration of the hydrogenation catalyst in the reaction product is 500 ppm or less.

(2) The alcohol production method according to (1), wherein the hydrogenation reaction is performed in a liquid phase.
(3) The aldehyde is a dimerized aldehyde obtained by further subjecting an aldehyde having 3 to 10 carbon atoms produced by the hydroformylation reaction or an aldehyde having 3 to 10 carbon atoms produced by the hydroformylation reaction to aldol condensation dehydration. (1) The manufacturing method of alcohol as described in (2).
(4) The method for producing an alcohol according to any one of (1) to (3), wherein the concentration of the hydrogenation catalyst in the hydrogenation reaction product supplied to the distillation purification step is 100 ppm or less.
(5) The hydrogenation reaction product is subjected to distillation purification using a distillation column, and the column bottom temperature of the distillation column is 150 ° C. or lower, according to any one of (1) to (4) Alcohol production method.

(6) The method for producing alcohol according to any one of (1) to (5), wherein the filter has a mesh size of 0.1 μm.
(7) The method for producing an alcohol according to any one of (1) to (6), wherein the hydrogenation catalyst is supported by using diatomaceous earth as a carrier and nickel and / or chromium as an active ingredient.

  According to the present invention, aldehyde production in a purification system can be remarkably reduced, and high-quality product alcohol can always be produced stably.

Hereinafter, the present invention will be described in more detail.
The aldehyde that is a raw material of the alcohol used in the present invention is not particularly limited, and is a saturated aldehyde having at least 3 carbon atoms and usually having 3 to 10 carbon atoms, or an aldol condensation dehydration thereof. An unsaturated aldehyde dimerized by reaction, a mixture thereof, and the like are used.

Saturated aldehydes include linear and side chain aldehydes, such as propionaldehyde, butyraldehyde, heptylaldehyde, nonylaldehyde, undecylaldehyde, tridecylaldehyde, hexadecylaldehyde, heptadecylaldehyde, and the like. It is done.
Examples of the unsaturated aldehyde include 2-ethylhexenal, 2-propylheptenal, and decenal.

Of these, butyraldehyde, nonylaldehyde, 2-ethylhexenal, and 2-propylheptenal are preferable.
In the present invention, the above-described method for producing an aldehyde is not limited. For example, in the case of a saturated aldehyde, a hydroformylation reaction of an olefin that is widely commercialized, more specifically, an organic phosphorus compound is coordinated. Examples thereof include a method in which an aldehyde is produced by hydroformylation of an olefin and an oxo gas under a group VIII metal complex catalyst or the like.

In the case of an unsaturated aldehyde, it can be obtained by subjecting a saturated aldehyde to an aldol condensation dehydration reaction. As the aldol condensation dehydration reaction, an alkali aqueous solution such as sodium hydroxide is used as a catalyst, and the hydroformylation reaction is performed. A method of dimerizing the produced aldehyde to obtain an unsaturated aldehyde can be mentioned.
In the present invention, it is of course possible to use a commercially available aldehyde.

In the method of the present invention, the above aldehyde is first hydrogenated using a hydrogenation catalyst (hereinafter sometimes referred to as a hydrogenation step).
As the hydrogenation catalyst, any conventionally known catalyst can be used, for example, a solid hydrogenation catalyst in which an active component such as nickel, chromium, copper is supported on a carrier such as diatomaceous earth or celite. It is done. In particular, it is preferable in the present invention to support diatomaceous earth as a carrier and nickel and / or chromium as an active ingredient. In the hydrogenation reaction of the aldehyde, the corresponding alcohol is produced by performing the reaction under the reaction conditions of normal pressure to 150 atm and 40 to 200 ° C. using the hydrogenation catalyst.

The reaction can be carried out in the gas phase by vaporizing the raw aldehyde, or it can be carried out in the liquid phase by introducing the raw aldehyde into the reactor as a liquid, but in the present invention, it is preferably carried out in the liquid phase. .
In the present invention, the conversion rate of the aldehyde in the hydrogenation step is not limited, but if the conversion rate is too low, the amount of aldehyde contained in the product alcohol will increase, so 80 to 99.99% It is desirable to set it as a range, and more preferably 98% or more.

In the present invention, in a process based on such a high conversion rate of aldehyde, it is possible to stably produce high-purity alcohol without increasing the scale and load of the purification equipment more than necessary. is there.
Next, in the present invention, it is essential to distill and purify the hydrogenation reaction product obtained in the absence of the hydrogenation catalyst or in the presence of a hydrogenation catalyst that does not cause a dehydrogenation reaction. As one form for that purpose, a step of removing the hydrogenation catalyst from the hydrogenation reaction product may be provided between the hydrogenation step and the distillation purification step.

  Note that. “In the presence of a hydrogenation catalyst that does not cause a dehydrogenation reaction” means that the concentration of aldehyde contained in the product alcohol does not deteriorate the quality of the product in the distillation column in which the product alcohol is distilled, preferably in the product alcohol. In the presence of an amount of hydrogenation catalyst that can be suppressed to a dehydrogenation reaction that does not result in a concentration of aldehyde of 0.05 wt% or more. Specifically, the concentration of the hydrogenation catalyst in the hydrogenation reaction product is preferably 500 ppm or less, more preferably 100 ppm or less, and particularly preferably 50 ppm or less. If the concentration of the hydrogenation catalyst is too high, an aldehyde is produced in the distillation production step.

Next, a step of removing the hydrogenation catalyst from the hydrogenation reaction product (hereinafter sometimes referred to as a catalyst removal step) before the purification step by distillation or the like will be described.
The method for removing the solid hydrogenation catalyst is not limited, but it can be carried out with a filter, a centrifugal separator, a simple distillation facility, etc., and is preferably carried out with a filter.

The concentration of the hydrogenation catalyst in the hydrogenation reaction product after the catalyst removal step is preferably 500 ppm or less, more preferably 100 ppm or less, and particularly preferably 50 ppm or less. If the concentration of the hydrogenation catalyst is too high, an aldehyde is produced in the distillation production step.
Next, in the present invention, the crude alcohol obtained by hydrogenation is purified (hereinafter referred to as “the crude alcohol”).
Sometimes referred to as a purification system or a purification process. )
In the present invention, the purification of the crude alcohol is usually performed using a distillation column. As by-products to be separated, high-boiling components such as esters, acetals, ethers, etc. produced by esterification, acetalization, etherification, etc., which are side reactions during the hydrogenation reaction, and their decomposition products, There are light boiling components such as unreacted aldehyde and isomer alcohol. However, some ethers azeotrope with alcohol and behave as light boiling components.

In the present invention, although distillation is not limited, it is usually carried out under atmospheric pressure or reduced pressure, and preferably carried out under reduced pressure. This is to reduce the heat load at the bottom of the distillation column and lower the temperature level of the reboiler heat source.
Specifically, it is preferable to operate under the condition that the tower bottom temperature is 150 ° C. or less.
In the present invention, the distillation column is not limited, but a distillation column which may optionally have a reflux drum, a condenser, a reboiler and / or a preheater can be used, and of course, other auxiliary equipment is also necessary. It may have according to. Moreover, the number of stages of the distillation column can be determined as appropriate.

  In the present invention, since the crude alcohol is usually dissolved in dissolved gases such as hydrogen, methane and nitrogen, it is preferable to separate the crude alcohol before distillation. And after isolate | separating dissolved gas, product alcohol is taken out using a distillation tower. In addition to distillation for taking out the final product alcohol, distillation for removing light boiling components, distillation for removing high boiling components, etc. may be combined, and light distillation is performed before obtaining final product alcohol. It is particularly preferred to carry out distillation to remove the boiling components, and distillation to remove the high boiling components after distillation to obtain the alcohol.

Below, the specific example of the manufacturing method of alcohol of this invention is demonstrated using FIG.
Hydrogen gas and aldehyde are supplied from the pipes 7 and 8 to the hydrogenation reactor 1 filled with a hydrogenation reaction catalyst to cause a hydrogenation reaction. The product liquid is sent to the gas-liquid separator 2 through the pipe 9 and is separated from the dissolved gas in the gas-liquid separator 2. The dissolved gas is discharged out of the system through the pipe 11.

After separating the dissolved gas, the product liquid is sent to the catalyst powder removing device 3 through the pipe 10 where the catalyst powder is removed. Then, it is supplied to the light boiling component separation distillation column 4 where the light boiling component is separated. The separated light boiling component passes through the pipeline 13 and is usually stored as fuel oil in a tank or the like and burned, but it is also possible to recover the effective component by distillation.
The bottoms after separation of the light boiling component is supplied to the product purification distillation column 5 from the pipe 12, and after separation from the high boiling component, product alcohol is obtained from the top of the distillation column. The high-boiling components are sent to the high-boiling component separation / distillation column 6 through the line 14 together with the product alcohol that could not be separated in the product purification distillation column 5, and the high-boiling components passed through the line 16 from the bottom of the distillation column. Withdrawn, the alcohol is withdrawn from the line 17.

  As described above, by providing the catalyst removal step between the hydrogenation step and the distillation production step, in the present invention, in the process in which the conversion rate of aldehyde in the hydrogenation reaction is 98% or more, A highly pure alcohol having an aldehyde concentration of 500 wtppm or less, preferably 100 wtppm or less, more preferably 50 wtppm or less can be obtained stably.

Hereinafter, specific embodiments of the present invention will be described in more detail with reference to examples. However, the present invention is not limited to the following examples unless it exceeds the gist.
Example 1
Crude nonyl alcohol containing catalyst powder obtained by hydrogenating nonyl aldehyde using a solid catalyst was collected from a nonyl alcohol plant, and the catalyst powder was removed using a filter having a mesh size of 0.1 μm. (The catalyst concentration after removal was 10 wtppm). Next, in a nitrogen atmosphere, 200 mL of crude nonyl alcohol was charged into a 1 L round bottom flask, and a heating test was performed at a pressure of 60 mmHgA and a temperature of 136 ° C. for 7 hours.

The results are shown in Table 1.
Comparative Example 1
Except for adding a powder of a solid hydrogenation catalyst (supporting nickel and chromium as active components on a diatomaceous earth support) to a crude nonyl alcohol collected from the same nonyl alcohol plant as in Example 1 to a catalyst concentration of 1160 ppm Conducted a heating test for 7 hours in the same manner as in Example 1.

The results are shown in Table 1.
Comparative Example 2
It implemented similarly to the comparative example 1 except having changed the heating time into 14 hours.
The results are shown in Table 1.

In Table 1, high boiling components 1 to 4 mean the following substances.
High boiling point component 1: C18 ether high boiling point component 2: C8 aldol high boiling point component 3: C20 acetal high boiling point component 4: C9 aldehyde trimer Hydrogenated catalyst powder is removed from Example 1 and Comparative Examples 1 and 2 above. It can be seen that the production of aldehyde can be significantly suppressed.
Example 2
Under an air atmosphere, a 100 cc 2-ethylhexanol sample was charged in a 200 cc round bottom flask, and a powder of nickel, chromium supported as an active ingredient on a diatomaceous earth carrier as a hydrogenation catalyst was added to a catalyst concentration of 14 wtppm. . The temperature was raised in about 5 minutes, and sampling was performed after 0 minutes, 10 minutes, and 60 minutes from the time when the temperature rose to 140 ° C., and concentration analysis of 2-ethylhexanal, which is an aldehyde, was performed.

The results are shown in Table 2.
Comparative Example 3
The same operation as in Example 2 was performed except that the hydrogenation catalyst was added to 0.3 wt%.
The results are shown in Table 2.

From the above Example 2 and Comparative Example 3, it can be seen that if the hydrogenation catalyst powder is removed, the generation of aldehyde can be remarkably suppressed even in an air atmosphere.

It is the schematic of an alcohol manufacturing process.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Hydrogenation reactor 2 Gas-liquid separator 3 Catalyst powder removal apparatus 4 Light boiling component separation distillation column 5 Product refinement distillation column 6 High boiling component separation distillation column

Claims (6)

In a method for producing an alcohol in which an aldehyde is hydrogenated using a hydrogenation reactor filled with a hydrogenation catalyst and the resulting hydrogenation reaction product is purified by distillation to obtain a product alcohol, the concentration of aldehyde contained in the product alcohol is A process for removing hydrogenated catalyst powder from the hydrogenation reaction product with a filter is provided between the hydrogenation step and the distillation purification step, and is provided for the distillation purification step after the catalyst removal step. A method for producing an alcohol, wherein the concentration of the hydrogenation catalyst in the hydrogenation reaction product is 100 ppm or less . The method for producing alcohol according to claim 1, wherein the hydrogenation reaction is performed in a liquid phase. The aldehyde is a dimerized aldehyde obtained by further subjecting an aldehyde having 3 to 10 carbon atoms produced by a hydroformylation reaction or an aldehyde having 3 to 10 carbon atoms produced by a hydroformylation reaction to aldol condensation dehydration. Or the manufacturing method of alcohol of 2. The method for producing an alcohol according to any one of claims 1 to 3 , wherein the hydrogenation reaction product is purified by distillation using a distillation column, and the bottom temperature of the distillation column is 150 ° C or lower. . Method for producing an alcohol according to any one of claims 1 to 4, wherein the mesh size of the filter is 0.1 [mu] m. The method for producing an alcohol according to any one of claims 1 to 5 , wherein the hydrogenation catalyst comprises diatomaceous earth as a carrier and nickel and / or chromium as an active ingredient.

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