JPH11349512A - Production of (poly)alkylene glycol monoalkyl ether - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce a (poly)alkylene glycol monoalkyl ether in high selectivity and yield advantageously on an industrial scale with little activity loss of a catalyst under suppression of alcohol by-production by reacting an olefin with a (poly)alkylene glycol under controlling the concentration of water in the reaction liquid below a specific level. SOLUTION: The reaction of (A) an olefin with (B) a (poly)alkylene glycol in the presence of (C) a catalyst (preferably, a crystalline metallosilicate) is carried out under controlling the concentration of water in the reaction liquid below 15 wt.% based on the total of the weights of the component B and water in the reaction liquid. Preferably, the component A is a 6-30C olefin, e.g. hexene, and a part or the whole part of unreacted component B is recycled as a raw material (poly)alkylene glycol.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing a (poly) alkylene glycol monoalkyl ether. More specifically, the present invention relates to a method for producing a (poly) alkylene glycol monoalkyl ether by reacting an olefin with a (poly) alkylene glycol.

[0002] (Poly) alkylene glycol monoalkyl ethers are useful as solvents, surfactants or intermediates for their production. In particular, (poly) alkylene glycol monoalkyl ethers obtained from long-chain olefins having a large number of carbon atoms generally have good wettability and solubility, and low pour points, and have extremely useful functions as surfactants. Have.

[0003]

2. Description of the Related Art A method for producing a (poly) alkylene glycol monoalkyl ether by reacting an olefin with a (poly) alkylene glycol relates to a method for producing a olefin and a (poly) alkylene in the presence of a strongly acidic cation exchange resin as a catalyst. A method of producing a (poly) alkylene glycol monoalkyl ether by reacting a glycol is disclosed in, for example, JP-A-2-295941.

A method for producing a (poly) alkylene glycol monoalkyl ether by reacting an olefin with a (poly) alkylene glycol in the presence of a heteropolyacid as a catalyst is disclosed in, for example, JP-A-3-148233. ing.

A method for producing a (poly) alkylene glycol monoalkyl ether by reacting an olefin with a (poly) alkylene glycol in the presence of benzene sulfonic acid or toluene sulfonic acid as a catalyst is disclosed, for example, in Japanese Patent Publication No. 61-1986. No. 51570.

A method for producing a (poly) alkylene glycol monoalkyl ether by reacting an olefin with a (poly) alkylene glycol in the presence of a crystalline metallosilicate as a catalyst is disclosed in JP-A-9-52856. ing.

[0007]

However, in the reaction of an olefin with a (poly) alkylene glycol, a conventional method using the catalyst has been proposed.
There is a problem that the activity of the catalyst decreases as the reaction is continued.

Further, unreacted (poly)
When (poly) alkylene glycol monoalkyl ether is continuously produced by recycling alkylene glycol, there is a problem that a large amount of alcohol is produced as a by-product.

When the alcohol by-produced in this manner is mixed into the product (poly) alkylene glycol monoalkyl ether, there is a problem that it causes odor or irritation. In the case of producing various derivatives of (poly) alkylene glycol monoalkyl ether, for example, in the case of producing a surfactant by adding ethylene oxide to (poly) alkylene glycol monoalkyl ether, the by-product alcohol is generally used. Since a simple alkali catalyst does not add ethylene oxide, it remains in the final product, causing a problem of odor and irritation.

The problem to be solved by the present invention is to solve the problems of the above-mentioned conventional method, to reduce the activity of the catalyst little, to suppress the by-product of alcohol, to obtain a high selectivity and a high yield of (poly). It is to produce an alkylene glycol monoalkyl ether industrially advantageously.

[0011]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to solve these problems, and as a result, it has been found that the problems of the conventional methods, such as the decrease in the activity of the catalyst and the by-product of alcohol, occur. It was found that one of the causes was water in the liquid.

That is, when a reaction solution contains a large amount of water when an olefin is reacted with a (poly) alkylene glycol in the presence of a catalyst to produce a (poly) alkylene glycol monoalkyl ether, the water is removed from the catalyst. It turned out that it became a poisoning substance and the production activity of (poly) alkylene glycol monoalkyl ether was significantly reduced. At the same time, water was added to the olefin, and it was found that undesirable alcohol was produced as a by-product. Further, generally, the olefin and the (poly) alkylene glycol as raw materials dissolve only in a small amount to each other, and the catalyst is contained in the (poly) alkylene glycol phase as the product (poly) alkylene glycol monoalkyl ether. Is often distributed to the olefin phase. In such a case, after the reaction is completed, the olefin phase and the (poly) alkylene glycol phase are separated, and the unreacted (poly) alkylene glycol phase containing the catalyst is replenished with the (poly) alkylene glycol consumed by the reaction. It is possible to set up a process of recycling to the next reaction and recovering the unreacted olefin and the product (poly) alkylene glycol monoalkyl ether from the olefin phase by a separation method such as distillation.
When (poly) alkylene glycol monoalkyl ether is produced by such a process, (poly)
It was found that the water concentration of the alkylene glycol phase gradually increased. This is because when the olefin reacts with the (poly) alkylene glycol, as a side reaction, the (poly) alkylene glycol undergoes a dehydration condensation reaction or a dehydration cyclization reaction to generate a small amount of water, and the generated water is converted to the (poly) alkylene glycol. Unreacted (poly) as it mainly partitions to the glycol phase
This is because water is accumulated in the (poly) alkylene glycol phase while the alkylene glycol phase is being recycled to produce the (poly) alkylene glycol. Therefore, it was found that, when the reaction was continued, the catalytic activity was reduced, the production rate of the (poly) alkylene glycol monoalkyl ether was reduced, and more alcohol was by-produced.

Therefore, the present inventors restricted the water concentration in the reaction solution to a specific concentration or less, and caused the reaction to proceed.
The present invention was found to suppress the decrease in the activity of the catalyst and the production of alcohol, to achieve a high reaction rate between the olefin and the (poly) alkylene glycol, to provide a high selectivity, and to efficiently produce the (poly) alkylene glycol monoalkyl ether. completed.

That is, the present invention provides a method for producing a (poly) alkylene glycol monoalkyl ether by reacting an olefin with a (poly) alkylene glycol in the presence of a catalyst. Wherein the reaction is carried out at 15% by weight or less with respect to the total weight of the (poly) alkylene glycol and water.

It is preferable to use a crystalline metallosilicate as the catalyst.

In the present invention, the starting olefin has 6 carbon atoms.
This is particularly effective when the olefin is at least 30 and at most 30.

The present invention is particularly effective when a part or all of the unreacted (poly) alkylene glycol is reused as a raw material (poly) alkylene glycol to carry out the reaction.

[0018]

DETAILED DESCRIPTION OF THE INVENTION The olefin used in the present invention has 6 carbon atoms having an ethylenically unsaturated bond.
And C30 to C30 hydrocarbons, preferably C10 to C20 hydrocarbons having an ethylenically unsaturated bond. Such an olefin may be a branched olefin, a linear olefin, an acyclic olefin, a cyclic olefin, or a mixture thereof without any particular limitation. . Considering the surfactant application, it is preferably an acyclic olefin,
It is more preferable that it is a linear olefin, and among them, an olefin having 6 to 30 carbon atoms is particularly preferable. Specific examples include hexene, octene, decene, dodecene, tetradecene, hexadecene, octadecene, eicosene, dococene and the like. These may be used alone or as a mixture of two or more. These olefins can be used without particular limitation, even when the position of the unsaturated bond is α-position, at the inner position, or at both the α-position and the inner position.
Of course, two or more of these olefins having different unsaturated bond positions can be used in combination.

The (poly) alkylene glycol used in the present invention includes monoethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, monopropylene glycol, dipropylene glycol, tripropylene glycol, polypropylene glycol and 1,3-propanediol. 1,2
-Butanediol, 2,3-butanediol, 1,4-butanediol, 1,6-hexanediol, 1,4-cyclohexanemethanediol and the like. These may be used alone or as a mixture of two or more.

The catalyst used in the present invention is not particularly limited, but a strong acidic cation exchange resin, heteropoly acid, benzenesulfonic acid, toluenesulfonic acid, crystalline metallosilicate, etc. can be used. Particularly, a crystalline metallosilicate is preferable. The use of crystalline metallosilicate as a catalyst is advantageous in that side reactions such as a dehydration-condensation reaction and a dehydration-cyclization reaction of (poly) alkylene glycol are suppressed, thereby suppressing the generation of water.

The crystalline metallosilicate is a regular porous material having a certain crystal structure, in other words, a solid material having a large specific surface area having a large number of regular voids and pores in the structure. The crystalline metallosilicate is a crystalline aluminosilicate (generally referred to as zeolite) and a compound in which another metal element is introduced into the crystal lattice in place of the Al atom of the crystalline aluminosilicate. Specific examples of such other metals include:
B, Ga, In, Ge, Sn, P, As, Sb, Sc,
Y, La, Ti, Zr, V, Cr, Mn, Fe, Co,
At least one of metals such as Ni, Cu, and Zn is used. In terms of catalytic activity and synthesis and availability,
Crystalline aluminosilicate, crystalline ferrosilicate,
Preferred are crystalline borosilicates and crystalline gallosilicates.

As a specific example of the above-mentioned crystalline metallosilicate, when described using an IUPAC code, MFI
(ZSM-5 etc.), MEL (ZSM-11 etc.), BEA
(Β-type zeolite, etc.), FAU (Y-type zeolite, etc.),
MOR (Mordenite, etc.), MTW (ZSM-12, etc.),
Those having a structure such as LTL (Linde L etc.) can be mentioned. In addition to these, "ZEOLITES, Vol. 1
2, No. 5, 1992 "and" HANDBOK OF M
OLECULAR SIEVES, R. Szostak
Author, VAN NOSTRAND REINHOLD Publishing "
And the like. These may be used alone or in combination of two or more. Among them, those having a structure such as MFI or MEL called a pentasil type or a structure of BEA are preferable from the viewpoint of excellent catalytic activity.

The crystalline metallosilicate has an atomic ratio of silicon atoms to metal atoms constituting the metallosilicate of 5 or more and 1 or more.
Those having a range of 500 or less, particularly 10 to 500 are preferable. When the atomic ratio of the silicon atom to the metal atom is too small or too large, the catalytic activity is low,
Not preferred.

Many of these crystalline metallosilicates have ion-exchangeable cations outside the crystal lattice. Specific examples of these cations include H ⁺ , Li ⁺ , Na ⁺ , R
b ⁺ , Cs ⁺ , Mg ²⁺ , Ca ²⁺ , Sr ²⁺ , Ba ²⁺ , S
c ³⁺ , Y ³⁺ , La ³⁺ , R ₄ N ⁺ , R ₄ P ⁺ (R is H or an alkyl group) and the like. Among them, those obtained by replacing all or a part of the cations with hydrogen ions are suitably used as the catalyst of the present invention.

The crystalline metallosilicate can be synthesized by a generally used synthesis method, for example, a hydrothermal synthesis method. Specifically, Japanese Patent Publication No. 46-10064, U.S. Pat. No. 3,965,207, "Journal of Molecular Catalysis" (Journal
of Molecular Catalysis) 3rd
1, 355-370 (1985). These crystalline metallosilicates are prepared, for example, by mixing a composition comprising a silica source, a metal source, and a quaternary ammonium salt such as a tetrapropylammonium salt until a crystal is formed at a temperature of about 100 to 175 ° C. After heating, the solid product is filtered, washed with water, dried, and then calcined at 350 to 600 ° C. to be synthesized. As the silica source,
Water glass, silica sol, silica gel, alkoxysilane and the like can be used. As the metal source, various inorganic or organic metal compounds can be used.
Preferred examples of such metal compounds include metal sulfates [eg Al ₂ (SO ₄ ) ₃ ] and metal nitrates [eg Fe
(NO ₃ ) ₃ ], alkali metal salts of metal oxides [eg N
metal salts such as aAlO ₂ ]; metal halides such as metal chlorides [eg TiCl ₄ ], metal bromides [eg MgBr ₂ ]; metal alkoxides [eg Ti (OC ₂ H ₅ ) ₄ ] And the like. The obtained crystalline metallosilicate can be ion-exchanged to a target cation. For example, H ⁺ -type cations are obtained by converting crystalline metallosilicate into HCl, NH ₄ Cl, N
By mixing and stirring in an aqueous solution such as H ₃ to exchange the cationic species to H ⁺ type or NH 4 ⁺ type, then filter, wash and dry the solid product, and then calcine at 350 to 600 ° C. Can be prepared. Part of the cationic species is H
Those substituted with ⁺ can be prepared by partially exchanging the H ⁺ type cation form with the desired cation form by performing the same operation using an aqueous solution containing the desired cation.

In this reaction, the catalyst may be used in any form. When a solid catalyst is used,
Powders, granules, molded articles having a specific shape and the like can be used. When a molded body is used, alumina, silica, titania or the like can be used as a carrier or a binder.

In the present invention, the reaction is preferably carried out in the absence of a solvent, but a solvent can be added if necessary. As the solvent, nitromethane, nitroethane, nitrobenzene, dioxane, ethylene glycol dimethyl ether, sulfolane, benzene, toluene, xylene, hexane, cyclohexane, decane, paraffin and the like can be used.

In the present invention, the water concentration in the reaction solution is defined by the weight percent of water based on the weight of (poly) alkylene glycol and water present in the reaction solution. In the case where the solvent or the like is not used, the olefin and the (poly) alkylene glycol as raw materials generally dissolve each other with only a slight solubility, and water is mainly used as the (poly).
In the alkylene glycol phase, the product (poly) alkylene glycol monoalkyl ether and by-product alcohol are mainly distributed to the olefin phase. In such a case, the water concentration in the reaction solution can be substantially regarded as the water concentration in the solution excluding the catalyst in the (poly) alkylene glycol phase.

In the present invention, the water concentration in the reaction solution is 15
The amount of the olefin is not particularly limited, but the lower the water concentration is, the more preferable it is. It is preferably more than 0 to 10% by weight, more preferably 5% by weight or less, and particularly preferably 3% by weight or less. When the water concentration in the reaction solution is 1
If it exceeds 5% by weight, the (poly) alkylene glycol monoalkyl ether forming activity of the catalyst is significantly reduced,
It is not preferable because the production of alcohol increases.

In the present invention, the method for limiting the water concentration to the above range is not particularly limited, but methods such as separation and removal of water in the raw material to be subjected to the reaction by distillation and removal by a desiccant or an adsorbent are used. Can be employed. The reaction solution is an olefin phase and (poly)
When two phases of the alkylene glycol phase are formed and the unreacted (poly) alkylene glycol phase is recycled and used for the next reaction, the water in the (poly) alkylene glycol phase is reduced during the reaction by the (poly) alkylene glycol. Is mainly mixed due to side reactions such as dehydration condensation reaction and dehydration cyclization reaction, and if the unreacted (poly) alkylene glycol phase is recycled, water may accumulate. A method of removing and recycling water in the unreacted (poly) alkylene glycol phase by means of separation and removal by distillation, removal with a desiccant or an adsorbent, or the like can be employed. At this time, the (poly) alkylene glycol phase may be treated entirely or partially. A method of partially discarding to remove other heavy components together with water can also be adopted. Further, a method of removing water during the reaction can also be employed. Since water may be mixed in the catalyst to be used, it can also be adjusted by dehydrating and drying these.

The method for measuring the water concentration is not particularly limited.
For example, it can be measured using a gas chromatograph measuring device, a liquid chromatograph measuring device, a Karl Fischer moisture meter, or the like.

In the present invention, the reaction may be carried out by a commonly used method such as a batch reaction or a flow reaction, and is not particularly limited.

The molar ratio of the olefin and the (poly) alkylene glycol, which are the starting materials for the reaction, is not particularly limited.
0.05 to 200, preferably 0.1 to 10 is used.

The reaction temperature is 50 to 250 ° C., preferably 100 to 200 ° C. The reaction pressure can be reduced, normal pressure or increased pressure.
/ Cm 2 is preferably performed.

When a batch reactor is used, the catalyst and the raw material of the present invention are charged into the reactor, and the mixture containing the desired (poly) alkylene glycol monoalkyl ether is stirred at a predetermined temperature and a predetermined pressure. Is obtained. The amount of the catalyst used is not particularly limited, but is 0.1 to 100% by weight, preferably 0.5 to 100% by weight, based on the starting olefin.
50% by weight are used. The reaction time varies depending on the reaction temperature, the type and amount of the catalyst, the raw material composition ratio, and the like.
To 100 hours, preferably 0.5 to 30 hours. After the reaction, the catalyst is separated by a method such as distillation, centrifugation, or filtration, and can be recycled for the next reaction. From the reaction solution from which the catalyst has been separated and removed, the desired (poly) alkylene glycol monoalkyl ether can be recovered by extraction or distillation, and the unreacted raw material can be recycled for the next reaction.

When a flow reactor is used, it can be carried out in any of a fluidized bed system, a fixed bed system and a stirred tank system. The reaction conditions at this time vary depending on the raw material composition, the catalyst concentration, and the reaction temperature, but are preferably 0.01 to 50 hr ^-1 as a liquid hourly space velocity (LHSV) obtained by dividing the volume flow rate of the flowing raw material by the volume of the reactor. Is 0.1-20 Hr ^-1
Range. After completion of the reaction, the desired (poly) alkylene glycol monoalkyl ether can be recovered by the same operation as in the batch reaction.

[0037]

The present invention will be described below in more detail with reference to Examples and Comparative Examples. However, this embodiment is one aspect of the present invention, and the present invention is not limited to this.

In the examples, the yields of products and by-products are calculated according to the following equations.

Yield of monoethylene glycol monododecyl ether (abbreviated as YE (mol%)) = (number of moles of monoethylene glycol monododecyl ether produced /
Number of moles of dodecene supplied) x 100 Yield of dodecyl alcohol (abbreviated as YA (mol%))
= (Mol number of generated dodecyl alcohol / mol number of supplied dodecene) × 100 Reference Example 1 (Preparation of catalyst (1)) BEA type zeolite manufactured by Zeolyst (trade name: CP)
811E) was used as catalyst (1). The atomic ratio of Si to Al in the catalyst (1) was 13.0, and the specific surface area was 65.
It was 6 m ² / g.

Reference Example 2 (Preparation of Catalyst (2)) The catalyst (1) in Example 1 was treated with 15 ml of 0.4N hydrochloric acid per gram at 40 ° C. for 2 hours, and A
After removing a part of l, the resultant was washed with distilled water and washed. The catalyst is then dried overnight at 120 ° C.
The mixture was calcined at 0 ° C. for 3 hours to obtain a catalyst (2).

When the composition of the obtained catalyst (2) was analyzed by X-ray fluorescence, the atomic ratio of Si to Al was 40.3. X-ray diffraction analysis of the obtained catalyst (2) revealed that the catalyst had the BEA type.

Example 1 270 g (1.60 mol) of 1-dodecene, 298.69 g (4.81 mol) of monoethylene glycol and 33.18 g of the catalyst (1) obtained in Reference Example 1 were stirred with a stirring blade and reflux cooled. The reactor was charged into a 1000-ml glass reactor equipped with a vessel, and the gas phase was replaced with nitrogen, and then kept in a nitrogen atmosphere at normal pressure. The raw materials dodecene and monoethylene glycol were sufficiently dehydrated, and the catalyst was used at 300 ° C before use.
Used for 3 hours. The inside of the reactor was separated into two phases, a dodecene phase and a glycol phase, and the catalyst was dispersed in the glycol phase.

Next, the temperature was raised to 150 ° C. while stirring at a rotation speed of 500 rpm, and the reaction was carried out at the same temperature for 1 hour. Thereafter, the reaction solution was cooled to room temperature, and products of an olefin phase and a glycol phase were analyzed by gas chromatography. The glycol phase was obtained by filtering the catalyst using a membrane filter and then analyzing the water concentration using a Karl Fischer moisture meter (before and after the reaction). The olefin phase mainly contained unreacted dodecene, monoethylene glycol monododecyl ether and dodecanol, and the glycol phase mainly contained unreacted monoethylene glycol, diethylene glycol and water. The analysis results are shown in Table 1.

Example 2 A reaction and analysis were carried out in the same manner as in Example 1 except that 6.10 g of water (corresponding to a water concentration of 2% by weight of the monoethylene glycol phase before the reaction) was added. went. The results are shown in Table 1.

Example 3 A reaction and analysis were carried out in the same manner as in Example 1 except that 15.72 g of water (corresponding to 5% by weight of the water content of the monoethylene glycol phase before the reaction) was added. went. The results are shown in Table 1.

Example 4 A reaction and analysis were carried out in the same manner as in Example 1 except that 33.19 g of water (equivalent to 10% by weight of the water content of the monoethylene glycol phase before the reaction) was added. went. The results are shown in Table 1.

Example 5 The reaction and analysis were carried out in the same manner as in Example 1 except that 52.71 g of water (corresponding to 15% by weight in terms of the water concentration of the monoethylene glycol phase before the reaction) was added. went. The results are shown in Table 1.

Comparative Example 1 The reaction and analysis were performed in the same manner as in Example 1 except that 74.67 g of water (corresponding to a water concentration of 20% by weight of the monoethylene glycol phase before the reaction) was added. went. The results are shown in Table 1.

Example 6 A reaction and analysis were carried out in the same manner as in Example 1 except that the catalyst (2) obtained in Reference Example 2 was used instead of the catalyst (1). The results are shown in Table 1.

Example 7 A reaction and analysis were carried out in the same manner as in Example 2 except that the catalyst (2) was used instead of the catalyst (1). The results are shown in Table 1.

Example 8 A reaction and analysis were carried out in the same manner as in Example 3 except that the catalyst (2) was used instead of the catalyst (1). The results are shown in Table 1.

Example 9 A reaction and analysis were carried out in the same manner as in Example 4 except that the catalyst (2) was used instead of the catalyst (1). The results are shown in Table 1.

[0053]

[Table 1]

"YE" in Table 1 represents the yield of monoethylene glycol monododecyl ether.
“A” represents the yield of dodecyl alcohol.

In the above examples, the glycol phase was mainly composed of monoethylene glycol, diethylene glycol and water, and these components were hardly dissolved in the dodecene phase. The dodecene phase was mainly composed of dodecene, monoethylene glycol monododecyl ether and dodecanol, and these components were hardly dissolved in the glycol phase. Therefore, the water concentration of the glycol phase obtained by filtering the catalyst can be regarded as the water concentration based on the sum of the weight of the (poly) alkylene glycol and water in the reaction solution. According to the example, it is found that the higher the water concentration of the glycol phase is, the lower the amount of monoethylene glycol monododecyl ether (YE) is decreased and the amount of dodecyl alcohol (YA) is increased. Therefore, the water concentration relative to the weight of the (poly) alkylene glycol and water in the reaction solution is 15% by weight or less, preferably 10% by weight or less,
More preferably 5% by weight or less, particularly preferably 3% by weight.
By setting it as follows, the (poly) alkylene glycol monoalkyl ether generating activity of the catalyst can be kept high and the generation of alcohol can be suppressed.

Further, the water concentration after the reaction is increased as compared with before the reaction. Therefore, if the unreacted (poly) alkylene glycol phase is recycled to the next reaction without removing the water, the water gradually accumulates and exceeds the water concentration in the above range specified by the present invention. It is clear that this will lead to an increase in by-product alcohol.

[0057]

According to the present invention, the activity of the catalyst is less reduced, the by-product of the alcohol is suppressed, the olefin and the (poly) alkylene glycol can be stably produced at a high selectivity and a high yield. Alkylene glycol monoalkyl ethers can be produced industrially advantageously.

Since unreacted (poly) alkylene glycol can be recycled and used again as a raw material,
It can be manufactured with high productivity in a continuous process.

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Yukio Sumino 14-1 Chidoricho, Kawasaki-ku, Kawasaki-shi, Kanagawa Prefecture Nippon Shokubai Co., Ltd.

Claims (4)

[Claims] 1. A method for producing a (poly) alkylene glycol monoalkyl ether by reacting an olefin with a (poly) alkylene glycol in the presence of a catalyst, wherein the water concentration in the reaction solution is adjusted by adjusting the (poly) A process for producing a (poly) alkylene glycol monoalkyl ether, wherein the reaction is carried out at 15% by weight or less based on the total weight of the alkylene glycol and water. 2. The method according to claim 1, wherein a crystalline metallosilicate is used as the catalyst. 3. The method according to claim 1, wherein the olefin is an olefin having 6 to 30 carbon atoms. 4. The process according to claim 1, wherein part or all of the unreacted (poly) alkylene glycol is reused as a raw material (poly) alkylene glycol.