JP2004196778A - Method for producing alcohol - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a high-purity alcohol by efficiently and inexpensively lowering the aldehyde concentration of a product alcohol. <P>SOLUTION: The method for producing an alcohol by hydrogenating an aldehyde in the presence of a hydrogenation catalyst and purifying the obtained product by distillation, wherein the hydrogenation product obtained in the absence of a hydrogenation catalyst or in the presence of a hydrogenation catalyst in such an amount as to inhibit a dehydrogenation reaction. Alternatively, the method for producing an alcohol by hydrogenating an aldehyde in the presence of a hydrogenation catalyst and purifying the obtained product by distillation, wherein the step of removing the hydrogenation catalyst from the hydrogenation catalyst is interposed between the step of hydrogenation and the step of purification by distillation. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

  The present invention relates to a method for producing an alcohol, and more particularly, to a method for producing an alcohol obtained by hydrogenating and refining an aldehyde, wherein the concentration of an aldehyde contained in a product alcohol is significantly reduced. And a method for producing the same.

  As a method for producing an alcohol, a method for obtaining a saturated alcohol by subjecting an aldehyde to a hydrogenation reaction and purifying the alcohol is conventionally known, and is commercially available worldwide. For example, for saturated aldehyde, butanol is hydrogenated to give butanol, to nonyl aldehyde is hydrogenated to nonanol, and to unsaturated aldehyde, for example, 2-ethylhexenal is hydrogenated to 2-ethylhexanol and 2-propylheptanol. Hydrogen can be added to tenal to obtain 2-propylheptanol, and hydrogen can be added to decenal to obtain decanol.

As a form of the hydrogenation reaction, it is general to use a reactor in which a nickel-based or copper-based solid hydrogenation catalyst is usually filled, and a method in which a raw aldehyde is vaporized and reacted in a gas phase. There is a type in which the raw aldehyde is introduced into a reactor in a liquid state and reacted in a liquid phase.
However, irrespective of the type of catalyst or gas / liquid phase reaction, in any of the conventional reaction processes, undesired side reactions such as esterification, acetalization, and etherification occur to reduce the selectivity of the reaction. At the same time, there is a problem that in the subsequent step, a satisfactory product alcohol cannot be obtained unless these byproducts are separated and removed and purified by a distillation operation or the like.

As a method for purifying the crude alcohol by distillation, for example, the following method has been proposed.
First, low-boiling substances are separated in the first column, then the pressure at the top is controlled in the second column, and alcohol is distilled off from the high-boiling substances to obtain an alcohol product by distillation from the top of the column. In this method, the pressure at the top of the column is controlled to recover useful products in the high-boiling components (three-column system).

Specifically, Patent Document 1 (Japanese Patent Publication No. 49-11365) discloses that, in the above three-column system, the second column is prepared under the condition that the top pressure is 200 to 800 mmHg and the alcohol content in the bottom is 50 wt% or more. And a method for obtaining purified 2-ethylhexanol by operating the third column under the condition of a top pressure of 70 to 300 mmHg.
In addition, a method in which the first column is performed in two stages in the 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 column and separated from the bottom, and then the active ingredient is distilled and recovered. In the fourth column, the low-boiling substances separated in the first column are further concentrated. There is also known a method in which the active ingredient is recovered by distillation from the bottom of the column.

  Further, in the second column for obtaining the product alcohol, high-boiling components in the bottom liquid, particularly low-boiling products generated by thermal decomposition of an acetal component, an ether component, etc., are contained in the alcohol product distilled off from the top of the column. In order to avoid this, a high-boiling component is separated in the first column, and a fraction containing a low-boiling component and alcohol and containing substantially no high-boiling component is distilled off from the top of the column. To separate a low-boiling component from alcohol by distillation and distill a fraction having a low-boiling component as a main component from the top of the column, while distilling purified alcohol as a side stream. 2).

Further, in the above-mentioned two-column system, in the first column for separating high-boiling components, the bottom temperature is maintained at a value calculated by a prescribed formula and the high-boiling component concentration in the bottom liquid is maintained at 30 wt% or more. There is also disclosed a method in which a boiling point component is actively pyrolyzed and recovered as an active component (see Patent Document 3).
On the other hand, in general, product alcohol is often used as a plasticizer mainly for resins such as vinyl chloride, and therefore requires extremely high purity and has little coloring, that is, heat-treats a sample with sulfuric acid, and then measures the degree of coloring. It is required that the degree of coloring in a sulfuric acid coloring test performed by the method be small.

Aldehydes can be mentioned as components that have a very strong effect on the sulfuric acid coloring test and the like, because aldehydes are unsaturated hydrocarbons. Therefore, the concentration of the aldehyde contained in the product alcohol is one of the most important items of the product alcohol quality item, and it is desirable that the concentration be reduced.
However, despite the fact that the product alcohol obtained by the above-mentioned prior art method contains a relatively large amount of aldehyde and is not sufficiently satisfactory as a product, in the above prior art, No attention is paid to the concentration of the aldehyde contained in the product alcohol, and no method for reducing the concentration is disclosed. This may be due to the fact that the following can be easily presumed even if there is no disclosed technology, given the common knowledge of those skilled in the art and chemical engineering.

  That is, the method of reducing the concentration of aldehyde contained in the product alcohol includes: 1) a method of increasing the conversion rate of aldehyde to alcohol in the hydrogenation reaction to reduce the amount of unreacted aldehyde brought into the purification system itself; 2) In the purification system, in the step of separating low-boiling components, a method of increasing the separation degree of aldehydes, which are low-boiling components, by increasing the number of stages in a distillation column, increasing the reflux ratio, or the like can be considered.

  In actual commercial operation, by changing the reaction temperature and other operating conditions, the decrease in the conversion of aldehydes due to the decrease in the activity of the hydrogenation catalyst over time is suppressed, and the amount of unreacted aldehydes brought into the purification system is reduced. (Ie, the above-mentioned measure (1)), or by increasing the reflux amount of the low-boiling component separation column of the purification system or increasing the amount of distillate withdrawn, thereby increasing the aldehyde separation efficiency (ie, the above-mentioned measure (2)) It is considered that the quality of the product alcohol, that is, the concentration of the aldehyde contained in the alcohol, is being maintained so as to be kept below the standard value.

However, at present, it is very difficult to obtain an alcohol having a low aldehyde concentration.
On the other hand, in the distillation purification of C3 to C10 alcohols, generation of the corresponding aldehyde has been confirmed by the heat load at the bottom of the distillation column, and a method of distilling in the presence of an alkali metal hydroxide as a suppression means is disclosed. (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 that the additive is mixed in the product alcohol cannot be denied.
Japanese Patent Publication No. 49-11365 JP-A-6-122638 JP-A-7-278032 Tokiohei 11-500377

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

  Product quality must be followed first and foremost, and the aldehyde concentration in the product alcohol must be maintained at a predetermined low level. As an operation adjustment for that purpose, for the purpose of increasing the aldehyde conversion in the hydrogenation reaction, it is necessary to change the reaction conditions such as changing the reaction temperature to a higher temperature side. Since the by-product ratio of the high-boiling components also increases, the reduction of the alcohol yield and the increase in the cost of purification and separation of the high-boiling components are unavoidable.

In the purification system, that is, to increase the distillation separation of low-boiling components means to increase the amount of reflux, the amount of distillate extracted, or the number of theoretical plates in the distillation column. This means higher costs. These are significant burdens that cannot be ignored economically.
Furthermore, by distilling at a pressure lower than the atmospheric pressure, even if the temperature at the bottom of the distillation column is set to 150 ° C. or lower to suppress the generation of aldehyde due to heat load, the aldehyde concentration in the product alcohol is reduced to a certain level or less. Could not be reduced.

  That is, an object of the present invention is to solve the above-mentioned problems, and it is an object of the present invention to efficiently and inexpensively reduce the aldehyde concentration in product alcohol to obtain high-purity alcohol.

  The present inventors have collected and analyzed plant data of actual commercial operation and studied the material balance of the plant in detail in order to study a drastic countermeasure for the above-mentioned problems, and have found a surprising result. That is, although the bottom temperature of the distillation column is low and the heat load is small, the amount of unreacted aldehyde contained in the hydrogenated product brought from the hydrogenation reaction system to the purification system is smaller than that of the unreacted aldehyde. It has been found that the sum of the amounts of aldehydes in all effluent streams, such as aldehydes discharged out, ie in the product and in separated low boiler streams, is always much higher.

  This indicates that aldehyde is generated in the purification system for some reason other than heat load. Furthermore, as a result of a detailed examination of where it is formed, for example, in a system using a low-boiling component separation column as the first column and a product column as the second column, the first column, which is a low-boiling component separation column, is largely used. Although part of the aldehyde was separated and removed from the top of the column, it was carried into the second column from the first column in the distillate product alcohol of the second column, which was a product column, and was not separated by the first column. It was found that the aldehyde content was several times that of the remaining aldehyde content.

That is, it was discovered that aldehyde was generated even in the product tower with a small heat load.
As a result of examining the causes of aldehyde formation in the purification system of this commercial plant from various angles, the bottom solution of the purification system and the hydrogenation reaction product fed from the hydrogenation reactor to the purification system were analyzed. By discovering that a crushed powder of the hydrogenation catalyst is present, and removing most of the powder of the hydrogenation catalyst, in a purification system, the knowledge as a method of substantially not generating aldehydes was obtained. The present invention has been completed.

That is, the gist of the present invention resides in the following (1) to (7).
(1) In a method for producing an alcohol by hydrogenating an aldehyde using a hydrogenation catalyst and distilling and purifying the obtained product, a hydrogenation catalyst in the absence of a hydrogenation catalyst or of such an extent that a dehydrogenation reaction does not occur. A method for producing an alcohol, comprising purifying a hydrogenation reaction product obtained in the presence by distillation.

(2) A method for producing an alcohol by hydrogenating an aldehyde using a hydrogenation catalyst and distilling and purifying the obtained product, comprising the steps of: A method for producing alcohol, comprising a step of removing an added catalyst.
(3) The method for producing an alcohol according to the above (1) or (2), wherein the hydrogenation reaction is performed in a liquid phase.

(4) The production method according to (2) or (3), wherein the removal of the hydrogenation catalyst is performed by a filter.
(5) The aldehyde is an aldehyde having 3 to 10 carbon atoms generated by a hydroformylation reaction or a dimerized aldehyde obtained by further subjecting an aldehyde having 3 to 10 carbon atoms generated by a hydroformylation reaction to an aldol condensation dehydration reaction. The production method according to any one of the above (1) to (4).

(6) The method according to any one of (1) to (5) above, wherein, in the hydrogenation step, the conversion of the aldehyde is 98% or more, and the concentration of the aldehyde contained in the product alcohol is 0.05 wt% or less. Production method.
(7) The production method according to any one of (1) to (6), wherein the concentration of the hydrogenation catalyst in the hydrogenation reaction product supplied to the distillation refiner is 100 ppm or less.

  ADVANTAGE OF THE INVENTION According to this invention, aldehyde production | generation in a refinement | purification system can be reduced remarkably, and a high-quality product alcohol can always be manufactured stably.

Hereinafter, the present invention will be described in more detail.
The aldehyde which 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 further comprising an aldol condensation dehydration. Unreacted unsaturated aldehydes reacted, and mixtures thereof are used.

Saturated aldehydes include linear and side-chain aldehydes, and specific examples include propionaldehyde, butyraldehyde, heptylaldehyde, nonylaldehyde, undecylaldehyde, tridecylaldehyde, hexadecylaldehyde, heptadecylaldehyde and the like. Can be
Examples of the unsaturated aldehyde include 2-ethylhexenal, 2-propylheptenal, and decenal.

Of these, butyraldehyde, nonylaldehyde, 2-ethylhexenal and 2-propylheptenal are preferred.
In the present invention, the method for producing the aldehyde described above is not limited. For example, in the case of a saturated aldehyde, a widely commercially available olefin hydroformylation reaction, more specifically, coordination of an organic phosphorus compound A method of producing an aldehyde by subjecting an olefin and an oxo gas to a hydroformylation reaction in the presence of a group VIII metal complex catalyst or the like as a catalyst.

In the case of an unsaturated aldehyde, it is obtained by subjecting a saturated aldehyde to an aldol condensation dehydration reaction.The aldol condensation dehydration reaction is carried out by the above-mentioned hydroformylation reaction or the like using an aqueous alkali solution such as sodium hydroxide as a catalyst. There is a method of dimerizing the generated aldehyde to obtain an unsaturated aldehyde.
In the present invention, a commercially available aldehyde can of course be used.

In the method of the present invention, the above-mentioned aldehyde is first hydrogenated using a hydrogenation catalyst (hereinafter sometimes referred to as a hydrogenation step).
As the hydrogenation catalyst, any conventionally known one can be used.Examples include a solid hydrogenation catalyst in which an active component such as nickel, chromium, and copper is supported on a carrier such as diatomaceous earth and celite. Can be Particularly, in the present invention, diatomaceous earth as a carrier and nickel and / or chromium as an active ingredient are preferred. In the hydrogenation reaction of the aldehyde, the corresponding alcohol is produced by using the hydrogenation catalyst under the reaction conditions usually at normal pressure to 150 atm and 40 to 200 ° C.

The reaction can be carried out in the gas phase by vaporizing the raw aldehyde, or 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 preferable to carry out the reaction in the liquid phase .
In the present invention, the conversion of the aldehyde in the hydrogenation step is not limited, but if the conversion is too low, the amount of the aldehyde contained in the product alcohol will increase. It is desirable to set it within the range, more preferably 98% or more.

In the present invention, in a process based on such a high aldehyde conversion, it is possible to stably produce a 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 that the hydrogenation reaction product obtained in the absence of a hydrogenation catalyst or in the presence of a hydrogenation catalyst that does not cause a dehydrogenation reaction be purified by distillation. As one mode for this, a step of removing the hydrogenation catalyst from the hydrogenation reaction product is provided between the hydrogenation step and the distillation purification step.

  In addition. `` In the presence of a hydrogenation catalyst that does not cause a dehydrogenation reaction '' means, in a distillation column for distilling product alcohol, such that the concentration of aldehyde in the product alcohol does not deteriorate the quality of the product, preferably in the product alcohol. In the presence of a hydrogenation catalyst in an amount sufficient to suppress the dehydrogenation reaction so that the aldehyde concentration contained does not become 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, aldehyde will be generated in the distillation production step.

Next, a step of removing the hydrogenation catalyst from the hydrogenation reaction product before the purification step by distillation or the like (hereinafter, may be referred to as a catalyst removal step) will be described.
The method for removing the solid hydrogenation catalyst is not limited, but can be carried out using a filter, a centrifuge, a simple distillation facility, or the like, and is particularly preferably carried out using 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, aldehyde is generated 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).
It may be called a purification system or a purification step. )
In the present invention, the crude alcohol is usually purified using a distillation column. As by-products to be separated, high-boiling components such as esters, acetals, and ethers generated by esterification, acetalization, and etherification, which are side reactions during the hydrogenation reaction, and their decomposed products, There are low boiling components such as unreacted aldehydes and isomeric alcohols. However, some ethers behave azeotropically with the alcohol and act as light boiling components.

In the present invention, distillation is not particularly limited, but is usually performed under atmospheric pressure or reduced pressure, and is preferably performed under reduced pressure. This is to reduce the heat load at the bottom of the distillation column and to lower the temperature level of the reboiler heat source.
Specifically, it is preferable to operate the column at a temperature of 150 ° C. or lower.
In the present invention, the distillation column is not limited, but a distillation column optionally having a reflux drum, a condenser, a reboiler and / or a pre-heater can be used. May also be provided. The number of stages in the distillation column can be determined as appropriate.

  In the present invention, the crude alcohol is usually dissolved in a dissolved gas such as hydrogen, methane, or nitrogen, and thus is preferably separated before distillation. After separating the dissolved gas, the product alcohol is taken out using a distillation column. In addition, in addition to distillation for removing alcohol as a final product, distillation for removing light-boiling components, distillation for removing high-boiling components, and the like may be performed in combination. It is particularly preferred to carry out the distillation to remove the boiling components and the distillation to remove the high-boiling components after the distillation to obtain the alcohol.

Hereinafter, a specific example of the alcohol production method of the present invention will be described with reference to FIG.
Hydrogen gas and aldehyde are supplied to the hydrogenation reactor 1 filled with the hydrogenation reaction catalyst from the pipes 7 and 8 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 through a line 10 to a catalyst powder removing device 3, where the catalyst powder is removed. Thereafter, the mixture is supplied to the light-boiling component separation distillation column 4, where the light-boiling component is separated. The separated light-boiling components are usually stored in a tank or the like as fuel oil through a pipe 13 and burned, but it is also possible to recover effective components by distillation.
The bottom product after the separation of the low-boiling components is supplied to the product purification distillation column 5 through a pipe 12 and separated from the high-boiling components, after which the 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 from a pipe 14 together with the product alcohol that could not be separated in the product refining distillation column 5, and the high-boiling components pass through a pipe 16 from the bottom of the distillation column. It is withdrawn and the alcohol is withdrawn from line 17.

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

Hereinafter, specific embodiments of the present invention will be described in more detail with reference to Examples, but the present invention is not limited to the following Examples as long as the gist is not exceeded.
Example 1
Nonyl aldehyde was obtained by hydrogenation using a solid catalyst, and crude nonyl alcohol containing catalyst powder 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). Then, under 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.

Table 1 shows the results.
Comparative Example 1
Except that powder of a solid hydrogenation catalyst (a diatomaceous earth carrier carrying nickel and chromium as an active ingredient) powder was added to crude nonyl alcohol obtained from the same nonyl alcohol plant as in Example 1 so that the catalyst concentration became 1160 ppm. Conducted a heating test for 7 hours in the same manner as in Example 1.

Table 1 shows the results.
Comparative Example 2
The operation was performed in the same manner as in Comparative Example 1 except that the heating time was changed to 14 hours.
Table 1 shows the results.

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

Table 2 shows the results.
Comparative Example 3
The same operation as in Example 2 was carried out except that the hydrogenation catalyst was added so as to be 0.3 wt%.
Table 2 shows the results.

From the above Example 2 and Comparative Example 3, it can be seen that removal of the hydrogenation catalyst powder can significantly suppress the generation of aldehyde even under an air atmosphere.

It is a schematic diagram of an alcohol production process.

Explanation of reference numerals

REFERENCE SIGNS LIST 1 hydrogenation reactor 2 gas-liquid separator 3 catalyst powder removal device 4 light-boiling component separation distillation column 5 product purification distillation column 6 high-boiling component separation distillation column

Claims (7)

  In the method for producing an alcohol by hydrogenating an aldehyde using a hydrogenation catalyst and distilling and purifying the obtained product, in the absence of a hydrogenation catalyst or in the presence of a hydrogenation catalyst that does not cause a dehydrogenation reaction. A method for producing an alcohol, wherein the obtained hydrogenation reaction product is purified by distillation.   In a method for producing an alcohol by hydrogenating an aldehyde using a hydrogenation catalyst and distilling and purifying the obtained product, a hydrogenation catalyst is separated from the hydrogenation reaction product between the hydrogenation step and the distillation purification step. A method for producing alcohol, comprising a step of removing the alcohol.   The method for producing an alcohol according to claim 1 or 2, wherein the hydrogenation reaction is performed in a liquid phase.   The production method according to claim 2 or 3, wherein the removal of the hydrogenation catalyst is performed by a filter.   The aldehyde is an aldehyde having 3 to 10 carbon atoms formed by a hydroformylation reaction or a dimerized aldehyde obtained by further subjecting an aldehyde having 3 to 10 carbon atoms formed by a hydroformylation reaction to an aldol condensation dehydration reaction. 5. The method according to any one of items 1 to 4.   The production method according to any one of claims 1 to 5, wherein in the hydrogenation step, the conversion of the aldehyde is 98% or more, and the concentration of the aldehyde contained in the product alcohol is 0.05 wt% or less. The production method according to any one of claims 1 to 6, wherein the concentration of the hydrogenation catalyst in the hydrogenation reaction product supplied to the distillation refiner is 100 ppm or less.

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