JP2001031600A - Production of highly pure monoethylene glycol - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a process for producing a highly pure monoethylene glycol by which the simplification of production step and operation, the energy saving and the low cost are achieved, the contamination of impurities such as glycol aldehyde in the monoethylene glycol product is suppressed, and a product standard value required for the highly pure monoethylene glycol of a fiber grade can be satisfied in the process for producing the monoethylene glycol. SOLUTION: This process for producing a highly pure monoethylene glycol by using an unrefined crude ethylene oxide as a raw material for a hydration reaction is characterized by introducing a side-cut technique into a monoethylene glycol rectifier 101, and taking out the monoethylene glycol from a side-cut part.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing high-purity monoethylene glycol.

[0002]

2. Description of the Related Art Conventionally, as shown in FIG. 2, in a method of producing monoethylene glycol by using purified ethylene oxide as a raw material for a hydrolysis reaction, a monoethylene glycol rectification column is substantially used without using a side cut method. A water-free ethylene glycol liquid (for example, a bottom liquid of a dehydration tower) is passed through a pipe 203 through a monoethylene glycol rectification column 2
01, a distillation operation is performed in the rectification column 201, and the entire amount of the monoethylene glycol vapor distilled out from the top of the rectification column 201 is passed through a condenser 207 provided on the path of a pipe 205. Condensed and liquefied into monoethylene glycol liquid,
A part of this monoethylene glycol liquid is refluxed back to the monoethylene glycol rectification column 201 through the branch pipe 209, and all the remaining monoethylene glycol liquid is obtained as a high-purity monoethylene glycol product through the pipe 208, A method was used in which the kettle liquid of a high boiling component such as diethylene glycol remaining at the bottom of the column 201 was sent to a diethylene glycol treatment step outside the system through a pipe 211.

[0003]

DISCLOSURE OF THE INVENTION The present inventors have studied various processes for producing monoethylene glycol in order to simplify the production process, save energy, and reduce costs. In the conventional production technology for producing monoethylene glycol by using the above, the above-mentioned object is achieved by changing the raw material for the hydrolysis reaction from purified ethylene oxide to unpurified crude ethylene oxide.
It has been found that the concentration of heavy aldehydes, particularly glycol aldehyde, produced by the hydrolysis reaction and entrained in the monoethylene glycol product is insufficiently reduced, and further, the thermal stability of the product monoethylene glycol deteriorates.
This deterioration in thermal stability is caused not only by glycol aldehyde but also by the use of crude ethylene oxide.Organic chlorine compounds, aldehydes and organic acids are changed during the hydrolysis reaction, and the boiling point is close to that of monoethylene glycol. Substances or impurities generated during the purification and purification of monoethylene glycol (eg, ethylene chlorohydrin, diethylene glycol monochlorohydrin, etc.)
It is thought to be due to.

[0004] Therefore, an object of the present invention is to achieve simplification of production steps and operations, energy saving and cost reduction in a process for producing monoethylene glycol, and reduction and reduction of glycolaldehyde in monoethylene glycol products. It is an object of the present invention to provide a method for producing high-purity monoethylene glycol which can reduce the above-mentioned substances causing deterioration of thermal stability and satisfy the quality required for high-purity monoethylene glycol of fiber grade.

[0005]

Means for Solving the Problems The present inventors have conducted intensive studies on a method for producing high-purity monoethylene glycol in order to achieve the above objects, and have found that unpurified ethylene oxide is used as a raw material for a hydrolysis reaction. The monoethylene glycol rectification column can be simplified without simplifying the manufacturing process and operation, saving energy, and reducing costs, and without adding or improving equipment for removing impurities or adding new processes. Surprisingly, it is possible to obtain a high-purity monoethylene glycol product with extremely low concentration of glycolaldehyde and high thermal stability from the side cut part by extremely simple means of introducing side cut technology to
Sufficient simplification of manufacturing process and operation, energy saving,
The inventors have found that cost reduction can be achieved, and have completed the present invention.

That is, the object of the present invention is to provide the following (1) to
This is achieved by (5).

(1) In a method for producing high-purity monoethylene glycol using unpurified crude ethylene oxide as a raw material for a hydrolysis reaction, a side cut technique is introduced into a monoethylene glycol rectification column, and A method for producing high-purity monoethylene glycol, comprising obtaining monoethylene glycol.

(2) The cut rate at the top of the monoethylene glycol rectification column is 0.01% by weight or more based on the feed amount to the monoethylene glycol rectification column. The method according to 1).

(3) The crude crude ethylene oxide is obtained by condensing part or all of the ethylene oxide-containing vapor obtained from the top of the ethylene oxide stripping tower by cooling and / or absorbing the condensate. The method according to the above (1) or (2), wherein the method is ethylene oxide.

(4) Condensate obtained by condensing part or all of the ethylene oxide-containing vapor obtained from the top of the ethylene oxide stripping tower with the crude crude ethylene oxide is refluxed to the stripping tower. (1) to (1), which are obtained without
The method according to any one of (3).

(5) The unpurified crude ethylene oxide partially condenses a vapor containing ethylene oxide obtained from the top of the ethylene oxide stripping tower to obtain a first condensate, and further condenses the remaining uncondensed gas. (1) to (1) to (1) to (4), wherein the obtained dehydrated ethylene oxide is mixed with the first condensate.
The method according to any one of (4).

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION The method for producing high-purity monoethylene glycol according to the present invention uses a crude ethylene oxide crude as a raw material for a hydrolysis reaction. It is characterized by introducing a side cut technology into the distillation tower and obtaining monoethylene glycol from the side cut portion.

As shown in FIG. 1, in the present invention, when ethylene oxide containing unpurified crude ethylene oxide is used as a raw material for a hydrolysis reaction to produce monoethylene glycol, a side cut technique is applied to a monoethylene glycol rectification column. And an ethylene glycol liquid substantially free of water (for example, a bottom liquid of a dehydration tower) is fed to a monoethylene glycol rectification column 101 through a pipe 103 for ethylene glycol liquid feed, and the rectification column 101 A distillation operation is carried out, and the monoethylene glycol vapor distilled out from the top of the rectification column 101 is condensed and liquefied in its entirety by a condenser (condenser) 107 provided on a path of a pipe 105 on the top side, and is then liquefied. Ethylene glycol liquid, a part of this monoethylene glycol liquid is refluxed back to the rectification column 101 through the branch pipe 109 for reflux on the top side, The concentrated liquid at the top of the column containing the other impurities is discharged out of the system through the pipe 108, and high-purity monoethylene glycol refluxed to the rectification column 101 is obtained as a product through a pipe 113 for side cutting, High boiling components such as diethylene glycol remaining at the bottom of the rectification column 101 are sent to a diethylene glycol treatment step outside the system through a pipe 111 at the bottom of the column. As a result, an overhead concentrate containing impurities such as glycolaldehyde, which is a relatively low-boiling component (light fraction), a high-purity monoethylene glycol side-cut solution and a high-boiling component having an intermediate boiling component (middle distillate) It can be separated into three components of a bottom liquid such as diethylene glycol (a heavy fraction).

Here, the crude crude ethylene oxide that can be used in the production method of the present invention is obtained in the process of purifying ethylene oxide by catalytic gas phase oxidation of ethylene with molecular oxygen in the presence of a silver catalyst. The crude ethylene oxide is not particularly limited as long as it is obtained. (1) Unrefined crude ethylene oxide generated in the conventional production process of ethylene oxide, for example,
No. 3772, US Pat. No. 3,904,656, Japanese Patent Publication No. 54-
Unrefined crude ethylene oxide used in the method described in JP-A-882 No. 882, specifically, B. overhead fraction of ethylene oxide stripping tower; B. overhead fraction of ethylene oxide dehydration tower, B. bottom liquid of ethylene oxide dehydration tower; A bottom liquid of an ethylene oxide rectification column, and E. Examples thereof include a bottom liquid of a reabsorption tower, and these may be used alone or in a combination of two or more.

Further, the present inventors have made intensive studies from the viewpoints of simplification of the process, reduction of the size of equipment such as a condenser and a reflux pump for the top distillate, and reduction of steam input to the stripping tower. And unpurified crude ethylene oxide shown in the following (2) to (4). The crude crude ethylene oxide shown in the following (2) to (4) can reduce the steam coming out from the top of the ethylene oxide stripping tower without diluting the crude crude ethylene oxide aqueous solution sent to the hydrolysis reactor. preferable.

(2) Ethylene oxide in a condensate obtained by condensing part or all of the ethylene oxide-containing vapor obtained from the top of the ethylene oxide stripping tower by cooling and / or absorption, and (3) ethylene oxide stripping tower The condensate obtained by condensing part or all of the ethylene oxide-containing vapor obtained from the top of the column without refluxing the stripping tower; and (4) the condensate obtained from the top of the ethylene oxide stripping tower The resulting ethylene oxide-containing vapor is partially condensed to obtain a first condensate, and the remaining uncondensed gas is further condensed or led as it is to an ethylene oxide dehydration column, and the obtained dehydrated ethylene oxide is subjected to the above-mentioned method. At least one of the mixture with the first condensate is used as a suitable raw material for a hydrolysis reaction. It can be used.

In the present invention, crude crude ethylene oxide can be used as a raw material for the hydrolysis reaction as described above. However, from the viewpoint of simplification of the production process and operation, energy saving and cost reduction, it is preferable. By using the unpurified crude ethylene oxide shown in (3) above as the raw material for the hydrolysis reaction, the heating amount of the ethylene oxide stripping tower can be reduced to 5%.
-10% can be reduced, and the subsequent purification step is not required.

In the present invention, crude ethylene oxide is used as a raw material for the hydrolysis reaction to produce monoethylene glycol. However, as described above, the process up to the monoethylene glycol rectification column is particularly limited. Instead, a conventionally known manufacturing method can be used. For example, a conventionally known manufacturing technique described in “Chemical Process”, edited by the Society of Chemical Engineers, page 121, etc. can be appropriately used. That is, the raw material for the hydrolysis reaction is subjected to a hydrolysis reaction in a reactor, and the reaction product is subjected to a distillation operation in a plurality of distillation columns to sequentially remove water and low-boiling components from monoethylene glycol. The present invention can utilize the production technique in a conventional production method for distilling glycol to obtain high-purity monoethylene glycol.

In the present invention, preferably, the bottom liquid of the monoethylene glycol dewatering column is fed to the monoethylene glycol rectification column, and the cut rate at the top of the monoethylene glycol rectification column is adjusted to the monoethylene glycol rectification column. It is desirable to carry out the distillation in an amount of 0.01% by weight or more, more preferably 0.1 to 2% by weight, based on the feed amount to the column. Monoethylene glycol obtained from the side cut section is obtained as a product, and the concentrated liquid coming out of the tower top containing impurities such as glycol aldehyde is discharged outside the system, so that the contamination of the side cut section with these impurities is extremely effective Can be prevented. If the cut rate at the top of the monoethylene glycol rectification column is less than 0.01% by weight with respect to the feed amount to the monoethylene glycol rectification column, the outside of the system is removed from the top of the monoethylene glycol rectification column. Due to the decrease in the amount of the concentrated liquid discharged to, the impurities such as glycolaldehyde are sufficiently transferred to the concentrated liquid side and are not eliminated, and the contamination of the reflux liquid refluxed from the top of the column with the impurities increases, It is not preferable because it is mixed in the monoethylene glycol liquid extracted from the side cut portion and leads to a decrease in the purity of the monoethylene glycol product. When the cut rate at the top of the monoethylene glycol rectification column exceeds 2% by weight with respect to the feed amount to the monoethylene glycol rectification column, the concentration of the concentrated liquid discharged outside the system from the top of the column is The amount of monoethylene glycol increases, which leads to a decrease in the acquisition rate of the monoethylene glycol product extracted from the side cut portion, which is not preferable. Here, the cut rate at the top of the monoethylene glycol rectification column refers to the amount fed to the column,
It is defined as the weight percentage of the amount discharged out of the system from the top of the tower. Further, in this specification, the side cut technique generally refers to a three-component system as a light fraction, an intermediate fraction,
This is a technique applied to a distillation column for separating by distillation into a heavy fraction, and the operation is as described in detail below.

Next, a monoethylene glycol rectification column which can be used in the present invention and which incorporates a side-cut technique, and its operation and conditions will be described below.

(1) Monoethylene glycol rectification column (hereinafter, also simply referred to as MEG rectification column) The type of the monoethylene glycol rectification column is not particularly limited, and may be a general distillation column. However, a packed tower with a small pressure loss is preferred. Further, in the conventional purification method, usually, a composite column including one or two MEG rectification columns and a MEG recovery column is used.
The G rectification column had only the enrichment section in the bottom feed, and the MEG recovery column in the subsequent stage had a middle feed structure having an enrichment section and a recovery section. In the MEG rectification column of the present invention, as shown in FIG. 3, in addition to the structure having the enrichment section and the recovery section in the middle stage feed, an enrichment section for side cutting may be provided on the enrichment section. Further, as described above, when the reaction is carried out in the composite tower, the enrichment section for side cut may be installed on the enrichment section for at least one or more columns.

The operating pressure of the monoethylene glycol rectification column is appropriately determined depending on the temperature of a heating source or a cooling source, and is not particularly limited.
00 mmHg.

(2) Feed solution to the monoethylene glycol rectification column In the present invention, the feed solution to be fed to the monoethylene glycol rectification column is the ethylene glycol solution fed to the monoethylene glycol rectification column. Is not particularly limited as long as it has a water content of substantially zero (specifically, 0.1% by weight or less). Bottom liquid of the monoethylene glycol dehydration column having a water content of substantially zero can be preferably used, but is not particularly limited thereto. Further, these are alkali-treated for the purpose of removing impurities in the prior art. It may be something like that.

The impurities contained in the crude crude ethylene oxide used as the raw material for the hydrolysis reaction include:
Depending on its manufacturing history, aldehydes, organic chlorines,
Contains inorganic chlorines, organic acids, etc. However,
Many of these impurities are removed in the course of conducting a normal dehydration operation after the raw material for the hydrolysis reaction is subjected to a hydrolysis reaction, and the ethylene glycol solution finally fed to the monoethylene glycol rectification column contains a normal distillation solution. In operation, glycolaldehyde, which is extremely difficult to separate from monoethylene glycol, and other unspecified trace amounts of impurities that deteriorate thermal stability are mixed. Therefore,
According to the present invention, impurities such as glycolaldehyde, which are extremely difficult to separate from monoethylene glycol by such a normal distillation operation, are to be separated in a monoethylene glycol rectification column obtained by introducing a side cut technique ( Impurities).

(3) Operating conditions of the monoethylene glycol rectification column Since the top temperature of the monoethylene glycol rectification column varies depending on the operating pressure, it should not be specified uniquely. In addition, in consideration of the operating pressure range specified above, the temperature range of the tower top must be very wide, but if specified, the temperature of the tower top is 30 to 160
° C.

The operating pressure of the monoethylene glycol rectification column is as already defined above.

The cut rate at the top of the monoethylene glycol rectification column is also as described above.

The reflux ratio (R / D; see FIG. 3) at the top of the monoethylene glycol rectification column is 10 to 50.
0, preferably 100 to 400. It is preferable to appropriately determine the number of theoretical plates in the side cut enrichment section and the amount of impurities.

The reflux ratio (R '/ D'; see FIG. 3) of the side cut of the monoethylene glycol rectification column is as follows:
It is 0.5 to 3, preferably 0.8 to 1.4. This R '/ D' also depends on the number of stages in the enrichment section,
The concentration may be determined so as to be within the specified value.

The number of theoretical stages of the enrichment section (see FIG. 3) of the monoethylene glycol rectification column is 5 to 30, preferably 7 to 15. The number of theoretical plates may be determined in consideration of the composition of the feed and the like so that the DEG concentration in the product is within a specified value.

The number of theoretical stages of the side cut enrichment section (see FIG. 3) of the monoethylene glycol rectification column is 3
10 to 10, preferably 5 to 10. It is good to determine appropriately according to the amount of impurities brought into the column.

In the present invention, by introducing the side cut technology, as described above, impurities such as glycolaldehyde are contained in the concentrated liquid (top liquid) discharged from the top of the monoethylene glycol rectification column. Can also be concentrated (concentration can be 200- to 1000-fold depending on the operating conditions specified above). This overhead liquid may be appropriately disposed of outside the system. However, it is preferable that the present inventors separately invent the invention and apply for a patent-pending method for producing monoethylene glycol (specifically, the recovered ethylene glycol). The high-purity monoethylene glycol is characterized by purifying the monoethylene glycol after adding alkali to the recovered ethylene glycol-containing liquid, subjecting it to a heat treatment, and then performing crude distillation. In the production method), it is desirable to reuse the overhead liquid as a recovered ethylene glycol-containing liquid. Thereby, the acquisition rate of monoethylene glycol produced from the entire plant can be further increased.

On the other hand, in the present invention, by introducing the side cut technology, all the side cut liquid of the monoethylene glycol rectification column can be recovered in high yield as a high-purity monoethylene glycol product. is there.

[0034]

EXAMPLES The present invention will be described below in detail with reference to examples, but the present invention is not limited to these examples.

Example 1 As a crude crude ethylene oxide, a gas obtained without condensing the entire top gas of a stripping tower and refluxing was used as a raw material for a hydrolysis reaction. Water is added to the water for the hydrolysis reaction to cause a hydrolysis reaction in a water reactor, and the reaction product is sequentially distilled in a plurality of distillation columns to distill water and components having a lower boiling point than monoethylene glycol. A dewatering tower bottom liquid substantially free of water was obtained. The bottom liquid is fed to the middle stage of a monoethylene glycol rectification column incorporating a side cut technology, and the top temperature of the rectification column is 127 ° C., the operation pressure of the rectification column is 60 mmHg, and the column of the rectification column is Distillation was performed under the condition that the cut rate at the top was 0.56% by weight based on the amount of feed to the monoethylene glycol rectification column. The reflux ratio (R / D) at the top of the rectification column was 144.9, and the reflux ratio (R '/ D') at the side cut portion of the rectification column was 1.
6. Further, the enrichment section of the rectification column (see FIG. 3)
The theoretical plate number was 7 and the theoretical plate number of the enrichment section for side cut of the rectification column (see FIG. 3) was 5. Monoethylene glycol obtained from the side cut portion was obtained as a product, and the concentrated liquid discharged from the top of the column was discharged outside the system. The glycol aldehyde concentration in the obtained monoethylene glycol product was measured by liquid phase chromatography (LC-10, manufactured by Shimadzu Corporation). The results obtained are shown in Table 1 below.

The obtained monoethylene glycol product was heated at 260 ° C. for 1 hour and 10 minutes. When the ultraviolet (UV220nm) transmittance of the monoethylene glycol product was measured before and after heating, the transmittance was 85% before heating → 84% after heating, and the transmittance hardly changed before and after heating, and thermal stability like glycol aldehyde It was confirmed that the deteriorating substances were sufficiently removed.

Comparative Example 1 The same bottom water of the dehydration tower substantially free of water as that used in Example 1 was fed to the middle stage of a monoethylene glycol rectification column in which the side cut technology was not introduced. The top temperature of the column is 127 ° C., the operating pressure of the rectification column is 60 mmHg
Distillation was carried out. A part of the monoethylene glycol obtained from the top of the rectification column refluxed at a reflux ratio of 1.6,
All the rest were obtained as monoethylene glycol products. The number of theoretical plates in the enrichment section of the rectification column was 7. The concentration of glycolaldehyde in the obtained monoethylene glycol product was measured, and the obtained results are shown in Table 1 below.

The obtained monoethylene glycol product was heated at 260 ° C. for 1 hour and 10 minutes. When the ultraviolet (UV220 nm) transmittance of the monoethylene glycol product was measured before and after heating, the transmittance was 85% before heating → 74% after heating, and the transmittance after heating was significantly reduced. It was confirmed that the removal was insufficient.

[0039]

[Table 1]

In Table 1, MEG represents monoethylene glycol, and GA represents glycol aldehyde.

[0041]

According to the present invention, a side cut technique is introduced into a monoethylene glycol rectification column when a crude ethylene oxide is used as a raw material for a hydrolysis reaction and monoethylene glycol is produced. Because glycol is obtained, the original purpose of the manufacturing process
Operation can be simplified, energy savings and cost reductions can be achieved.Furthermore, impurities such as glycol aldehyde and other substances with thermal stability that are extremely difficult to separate from monoethylene glycol by conventional distillation operations alone are extremely difficult. It can be concentrated from the top of the monoethylene glycol rectification column and discharged out of the system, and the amount (concentration) of these impurities mixed into the monoethylene glycol extracted from the side cut section can be kept extremely low. As a result, the obtained monoethylene glycol has extremely high purity and high yield, and can realize high added value as a fiber grade product having high heat stability.

[Brief description of the drawings]

FIG. 1 is a schematic view of a monoethylene glycol rectification column incorporating a side cut technique used in the method for producing high-purity monoethylene glycol according to the present invention.

FIG. 2 is a schematic diagram of a process including a monoethylene glycol rectification column in which a side cut technique used in a conventional method for producing monoethylene glycol has not been introduced.

FIG. 3 is a simplified explanatory view of a monoethylene glycol rectification column obtained by introducing the side cut technique of FIG. 1;

[Explanation of symbols]

 101, 201… Monoethylene glycol rectification column, 103, 203… Pipe for feeding ethylene glycol liquid, 105, 205… Piping on top side, 108… Piping for collecting impurities from condenser, 208… Condenser 107, 207: condenser (condenser), 109, 209: branch piping for reflux from the condenser, 111, 211: piping at the bottom of the tower, 113: piping for side cut.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Kenji Suzuki 14-1 Chidoricho, Kawasaki-ku, Kawasaki, Kanagawa Prefecture Nippon Shokubai Co., Ltd. (72) Inventor Hironori Horie 14-1 Chidoricho, Kawasaki-ku, Kawasaki-shi, Kanagawa Co., Ltd. Within Nippon Shokubai (72) Inventor Makoto Furukawa 14-1 Chidoricho, Kawasaki-ku, Kawasaki-shi, Kanagawa F-term (reference) 4H006 AA02 AC42 AD11 BC50 BD82 BN10 FE11

Claims (5)

[Claims] 1. A method for producing high-purity monoethylene glycol by using unpurified crude ethylene oxide as a raw material for a hydrolysis reaction, comprising introducing a side cut technique into a monoethylene glycol rectification column, A method for producing high-purity monoethylene glycol, comprising obtaining ethylene glycol. 2. The cut rate at the top of the monoethylene glycol rectification column is set to 0.01% by weight or more based on the amount of feed to the monoethylene glycol rectification column. The method described in. 3. The ethylene oxide in a condensate obtained by condensing part or all of the crude ethylene oxide by cooling and / or absorbing the ethylene oxide-containing vapor obtained from the top of the ethylene oxide stripping tower. The method according to claim 1 or 2, wherein 4. A condensate obtained by condensing a part or all of the ethylene oxide-containing vapor obtained from the top of the ethylene oxide stripping tower with the crude crude ethylene oxide without refluxing the condensate to the stripping tower. 3. The method according to claim 1, wherein the method is obtained. 5. The crude crude ethylene oxide partially condenses a vapor containing ethylene oxide obtained from the top of the ethylene oxide stripping tower to obtain a first condensate, and further condenses the remaining uncondensed gas. The process according to claim 1 or 2, wherein the process is conducted to an ethylene oxide dehydration column in an as-is or as it is form, and the obtained dehydrated ethylene oxide is mixed with the first condensate.