JPH02200649A - Deodorization of ethylene glycol - Google Patents

Abstract

PURPOSE:To effectively deodorize ethylene glycol(EG) by treating a by-produced bred EG with a volatile hydrocarbon substantially immiscible with the EG to extract odorant components. CONSTITUTION:When ethylene oxide is hydrated to prepare ethylene glycol(EG), a by-produced bred EG is treated with a volatile hydrocarbon (e.g. hexane, heptane, benzene, toluene or xylene) substantially immiscible with EG to extract odorant components, thereby deodorizing the EG. The by-produced EG is especially subjected to desalting and dehydrating treatments and subsequently distilled to recover monoethylene glycol. The recovered ethylene glycol is subjected to an extraction treatment using a volatile hydrocarbon substantially immiscible with the EG to provide deodorized monoethylene glycol.

Description

Detailed Description of the Invention [Industrial Field of Application] The present invention relates to a method for deodorizing ethylene glycol (hereinafter abbreviated as EG), and in particular, to a method for deodorizing ethylene glycol (hereinafter abbreviated as EG), and in particular to a method for deodorizing ethylene glycol (hereinafter abbreviated as EG).
The present invention relates to the removal of odor components in recovered EG such as ethylene glycols recovered from bleed EG that is produced as a by-product in the process of producing G.

The method of the present invention can also be applied to improve the odor of monoethylene glycol (MEG), diethylene glycol (DEC), triethylene glycol (TEG), etc. obtained in an EG production plant.

[Conventional technology 1] Currently, EG is produced by hydration of ethylene oxide, which is obtained by reacting excess water at high temperature and pressure without a catalyst, concentrating the resulting aqueous solution, and then rectifying it. In the hydration reaction of ethylene, diethylene glycol (which is a mixture of monoethylene glycol and ethylene oxide) is usually used.
DEC), triethylene glycol (TEG), etc. are produced as by-products.In the ethylene oxide manufacturing process, the produced ethylene oxide is absorbed by alkaline water in an absorption tower and separated from unreacted gas, and the unreacted gas is converted into ethylene oxide. When ethylene oxide is absorbed into water in this absorption tower, E
G is produced as a by-product. The liquid discharged from the ethylene oxide absorption tower passes through an ethylene oxide stripper, a stripping tower, etc., and ethylene oxide is recovered.
G is called bleed EG.

MEG obtained from by-product bleed EG (abbreviated as recovered MEG) is produced by distilling the bleed EG after desalting and dehydrating it. However, the recovered MEG obtained in this manner has a pronounced burnt odor accompanied by a pungent odor, and thus requires deodorization.

For this reason, deodorizing methods using activated carbon or deodorizing methods using hydrogenation are generally practiced, but these two deodorizing methods hardly remove odor components, so ME
This method was unsatisfactory as a method for removing odor components of ethylene glycols such as G. For example, deodorizing recovery M by activated carbon treatment
For EG, in order to pass odor standards, it is necessary to further dilute it with fiber grade (abbreviated as odorless grade) MEG, and the necessary dilution ratio is 50 to 100 times.

[Problem to be solved by the invention 1 The above recovered MEG has an MEG purity of 99.5% by weight or more,
In addition, the composition has a DEG impurity concentration of 0.5% by weight or less, and there is no problem with the quality as determined by instrumental analysis and chemical analysis such as purity and impurities, but it does not have a burnt odor accompanied by a pungent odor. It is not suitable for general grades such as antifreeze and textiles, and its applications are extremely limited.
Effective use is hindered.

The present invention provides an effective method for deodorizing odorized EG such as recovered MEG.

[Means for Solving the Problems] The present invention has surprisingly found that the odorous substances dissolved in these hydrophilic IEGs are lipophilic, and the present invention extracts the odorous substances with a lipophilic solvent and deodorizes them. It was very successful.

That is, the present invention provides E by the hydration reaction of ethylene oxide.
In the process of manufacturing G, the by-product bleed EG is
This method of deodorizing EG is characterized by extracting and removing odor components using volatile hydrocarbons that do not substantially mix with EG.

The deodorizing method of the present invention is applied to the dehydrated bleed EG itself before recovering MEG by distillation.
G mixture can be obtained, especially by-product bleed EG
After desalination and dehydration treatment, MEG is recovered by distillation, and the recovered MEG is deodorized by extraction treatment using volatile hydrocarbons that are substantially immiscible with ethylene glycol. is obtained.

The extraction solvent used in the present invention is a volatile hydrocarbon that does not substantially mix with EG.

"Substantially not mixed" means that the compatibility with EG is low, and even if mixed and shaken and stirred, they will separate when left still. Therefore, it is acceptable that a part of the extraction solvent is dissolved in the EG, and a small amount of EG is dissolved in the extraction solvent.

In addition, volatility is to facilitate the recovery of the extraction solvent, and in addition to recovering the solvent from the separated extraction solvent layer after the extraction process, it is also used to store the extraction solvent dissolved in the separated EG layer. Facilitates removal by ripping. therefore,
The extraction solvent has a higher vapor pressure than MEG, and preferably has a higher vapor pressure as long as it is liquid at least at room temperature.

Specifically, highly volatile hydrocarbons such as hexane, heptane, benzene, toluene, and xylene are used as such extraction solvents.

The recovered EG to be deodorized is preferably one that has been demineralized and dehydrated as much as possible.

In the ethylene oxide absorption tower in the ethylene oxide production process, alkaline water is used to absorb only ethylene oxide into water and separate it from unreacted gas. However, during the synthesis of ethylene oxide, oxidation products such as formaldehyde, carbon dioxide, formic acid, acetic acid, and oxalic acid are generated in addition to ethylene oxide. come. Since these organic salts and inorganic salts worsen the hue of the recovered EG produced from the bleed EG, it is preferable to remove them in advance by desalting treatment. In particular, this desalting treatment is necessary when MEG is not isolated from the bleed EG but is recovered as mixed EG.

Desalination treatment is performed under reduced pressure of 40 to 70 mmHg and at a temperature of 150 to
Salts are removed by flushing at 170°C.

In the dehydration treatment, the product specifications specify a water content of 0.1% by weight or less, and to satisfy this specification, vacuum distillation is performed at a temperature of 150° C. under a reduced pressure of 120 mmHg to remove water from the top of the column.

The amount of extraction solvent added for extraction and removal of odor components is arbitrary, but for example, 0.2 to 2 parts by volume of extraction solvent is added to the volume of recovered EGI.

After the addition, vigorous fluid contact mixing is carried out for 5 to 20 minutes by stirring or shaking, and then the mixture is allowed to stand still. Two layers are formed, consisting of the extraction solvent in the soil layer and the EG in the lower layer, and the odor components are separated into the extraction solvent layer of the soil layer. The extraction solvent dissolved in the lower layer of EG is completely evaporated by gas stripping or distillation using an inert gas such as N2 at approximately 80°C to 120°C.
removed from G.

The deodorizing effect of the recovered EG from which odor components were removed by such extraction and removal method was evaluated as follows.

Put 30n+j of the sample into a 50mj Erlenmeyer flask and let it cool at room temperature (
After leaving it at 30℃ for 30 minutes or more, take it out and check the smell (5℃).
The odor was evaluated based on the criteria of 0 to 8 grades, and the average value was used as the average value.

Here, the criteria for judgment were as follows.

0: Odorless, 2: Slight odor. 4: There is a distinct smell. 6: Strong smell. 8: The smell is unbearable.

Odd values indicate odors in between.

When hexane, benzene, toluene, or the like is used as an extraction solvent, an improvement in odor level of 2 to 4 can be expected compared to activated carbon-treated EG. On the other hand, the odor level of the component obtained by evaporating and removing the extraction solvent from the extraction solvent layer from which the odor component has been separated is 2 to 4 times higher than that of the raw material.

From these odor level evaluations, it is clear that a deodorizing method by extraction and removal using volatile hydrocarbons is very effective as a method for improving the odor of recovered MEG.

When we measured the infrared absorption spectrum of the odor component concentrate separated in the extraction solvent layer, carbonyl groups (ketones, esters) were confirmed as functional groups, and it was confirmed that hydrocarbons were used as the extraction solvent. Taking this into account, the odor components of recovered EG are mainly lipophilic compounds having carbonyl groups.

From this result, it is presumed that the odor components were generated due to oxidative heating deterioration. Moreover, gas chromatographic analysis shows that these odor components exist in large quantities in the boiling point range from MEG to triethylene glycol. Therefore, as a method for removing odorous substances caused by oxidative deterioration of EG such as MEG, DEG, and TEG produced from an MEG production plant, the deodorizing method based on the nature can be applied.

[Example] The present invention will be explained in more detail below using Examples.

Example 1 50 mj of MEG (purity 99.5% by weight) recovered from bleed EG was placed in a 200a+1 separatory funnel, 50 mj of extraction solvent benzene was added, and the mixture was shaken vigorously for 10 min.
After shaking for a minute, the mixture was left to stand and separated. The lower MEG layer was extracted, 50 mj of benzene was added, and extraction and separation were carried out in the same manner as above. After separation into two layers, 30 mj of the upper layer and lower layer were each collected in a 50 m Erlenmeyer flask.

Transfer to a hot plate at a temperature of 100℃ and add 50mj of nitrogen.
The extraction solvent was removed by gas stripping. Note that all experiments were conducted at room temperature (25 to 30°C). The odor level of the MEG obtained by this method was evaluated by a predetermined method.

The evaluation results are shown in Table 1.

In order to estimate the concentration of odor components and the structure of the compound in the upper extraction solvent layer, the extraction solvent was removed in the same manner as described above, the layer was smelled, and the infrared absorption vector was measured. The odor of the material obtained from the extraction solvent layer was intolerable with an odor level of 8. The obtained infrared absorption spectrum is shown in FIG. A characteristic absorption band of carbonyl group, which is not seen in EGs, was detected in the 1700-1800 cm-' region.

Comparative Example 1 The same sample as in Example 1 was treated with activated carbon (Shirasagi A manufactured by Narita Pharmaceutical Co., Ltd.).
) 10 to 20 kg and MEG61-ton were put into the stirring tank,
After performing batch processing for 1 hour, activated carbon was separated using a filter press, and the resulting MEG was evaluated for odor level.

The evaluation results are shown in Table 1.

Example 2 Odor components were removed by the same experimental method as in Example 1 using toluene as an extraction solvent, and the odor level was evaluated. The results are shown in Table 1.

Example 3 Odor components were removed by the same experimental method as in Example 1 using hexane as an extraction solvent, and the odor level was evaluated and shown in Table 1.

Example 4 EG (MEG:
68% by weight, DEG: 25% by weight, TEG: 3% by weight,
Table 1 shows the evaluation of the odor level of the samples in which odor components were removed using the same experimental method as in Example 1 using water (4% by weight).

Comparative Example 2 The same sample as Example 4 was prepared using nickel as a catalyst.
Table 1 shows the results of evaluating the odor level of the deodorized product obtained by performing deodorizing treatment by hydrogenating at a temperature of 90 to 110° C. and a pressure of 22 kg/cm 2 .

[Effects of the Invention] It is possible to improve the odor level of the recovered MEG obtained by the present invention by 2 or more without impairing the purity of MEG.

As a result, odorless grade MEG can be obtained from conventionally recovered MEG.
odorless grade MEG to obtain at least 50
It is necessary to dilute ~100 times, for example, the current MEG
Assuming that approximately 1% of recovered MEG can be obtained based on the production capacity, it is practically difficult to make all recovered MEG into odorless grade, but by using the deodorizing method of the present invention, dilution of 5 to 10 times That is, it is possible to obtain odorless grade MEG with a dilution amount of 1/10, and odorless grade MEG can be easily achieved.

[Brief explanation of the drawing]

FIG. 1 shows the infrared absorption spectrum of the separated odor components.

Claims (2)

[Claims] (1) In the process of producing ethylene glycol by the hydration reaction of ethylene oxide, the by-product bleed EG is
A method for deodorizing ethylene glycol, which comprises extracting and removing odor components using volatile hydrocarbons that are substantially immiscible with ethylene glycol. (2) In the process of producing ethylene glycol by the hydration reaction of ethylene oxide, the by-product bleed EG is
After desalination and dehydration treatment, monoethylene glycol recovered by distillation is extracted and removed to remove odor components using volatile hydrocarbons that do not substantially mix with ethylene glycol. Deodorization method.