[DESCRIPTION]

[invention Title] PROCESS FOR PREPARATION OF AN OXIRANE

[Technical Field]

The present invention relates to a process for preparing an oxirane compound. More specifically, it relates to a solvent extraction process which comprises extracting with an organic solvent the reaction mixture of an oxirane compound, olefin, water and alcohol produced by reaction of an olefin with a peroxide in the presence of a catalyst and alcohol solvent, to recover the oxirane compound and the olefin in the extract and the alcohol and water in the extraction residue, wherein water together with the organic solvent is employed as additional extraction solvent. For example, allyl chloride and hydrogen peroxide are diluted with alcohol and contacted with a catalyst to obtain the product containing epichlorohydrin via epoxidation.

[Background Art]

Olefin and hydrogen peroxide solution, which is usually supplied as an aqueous solution on economic grounds, have very low compatibility. Thus the mixture is diluted and mixed with an organic solvent which has excellent compatibility with an aqueous solution and excellent compatibility with the olefin

at the same time. An alcoholic organic solvent such as methanol, ethanol, propanol and butanol is used for this purpose, with methanol being preferred.

The reaction of olefin and hydrogen peroxide to produce an oxirane compound via epoxidation is generally represented by following reaction formula:

For instance, epichlorohydrin is produced by epoxidation of allyl chloride and hydrogen peroxide, which is an exothermic reaction represented by following reaction formula:

/S/I ₊ H ₂ O ₂ ^CatalySt » ° _[ >^C\ ₊ H ₂ O

Thus, the main components of the reaction product from the epoxidation of allyl chloride and hydrogen peroxide are epichlorohydrin, water, allyl chloride and methanol. The reaction products, epichlorohydrin and allyl chloride, are recovered as an extract, via solvent extraction using an organic compound or a halogenated organic compound as an extraction solvent, while methanol and water are recovered as the extraction residue (USP 6,288,248, USP 6,350,888, Korean Patent Laid-Open No. 1999-45646) .

When using the solvent extraction process which comprises contacting the reaction product with extraction solvent in an

extraction device, at least a part of methanol is extracted as an extract owing to its chemical affinity with main components of the extract such as epichlorohydrin, allyl chloride and the extraction solvent. Moreover, water is accompanied with the extract owing to mutual affinity between methanol and water. Methanol in the extract forms a mixture that cannot be easily isolated from epichlorohydrin by means of fractional distillation. When a fractional distillation of the extract containing water is tried, phase separation between the liquids occurs inside the distillation tower, so that the design and operation of a distillation tower is difficult. Further, when the extract is heated for fractional distillation, methanol and water react with epichlorohydrin, thereby the epoxy ring of epichlorohydrin is open and the compound is converted to chlorinated impurities such as 1- chloro-3 -methoxy-2-propanol, 1-chloro-2-methoxy-3-propanol , 1, 3-dichloro-2-propanol, 2, 3-dichloro-propanol, l-chloro-2, 3- dihydroxy-propane .

[Disclosure]

[Technical Problem]

The object of the present invention is to provide an efficient solvent extraction process which comprises extracting with an organic solvent the reaction mixture of an oxirane compound, olefin, water and alcohol produced by reaction of an olefin

with a peroxide in the presence of a catalyst and alcohol solvent, to recover the oxirane compound and the olefin in the extract and the alcohol and water in the extraction residue.

[Technical Solution]

The present invention relates to a process for preparing an oxirane compound. More specifically, it relates to a solvent extraction process which comprises extracting with an organic solvent the reaction mixture of an oxirane compound, olefin, water and alcohol produced by reaction of an olefin with a peroxide in the presence of a catalyst and alcohol solvent, to recover the oxirane compound and the olefin in the an extract and the alcohol and water in the extraction residue, wherein water together with the organic solvent is employed as additional extraction solvent.

The olefin is represented by allyl chloride; the oxirane compound produced by the reaction of allyl chloride and peroxide is epichlorohydrin; peroxide is aqueous hydrogen peroxide solution from the economical viewpoint; and the alcohol may be a lower alcohol such as methanol, ethanol, n- propanol, i-propanol and butanol, with methanol being preferred.

As a catalyst for preparing an oxirane, employed can be a titanium silicalite catalyst having similar structure to zeolite ZSM-5, commonly known as TS-I.

Olefin and hydrogen peroxide as the main substances for the reaction for producing oxirane compound via epoxidation are mixed in a molar ratio of wide range to carry out the epoxidation. The molar ratio is from at least 0.1 to not more than 10. Since it is difficult to establish a process for recovering unreacted hydrogen peroxide from the reaction product, it is preferable to exhaust hydrogen peroxide as much as possible. Thus the molar ratio of olefin to hydrogen peroxide is preferably not less than 1.0, but not more than 5.0 as considering the operation cost for olefin recovery.

When olefin and aqueous hydrogen peroxide solution as the reactant material of epoxidation to produce oxirane compound are diluted with an alcohol such as methanol, the amount of alcohol can be selected in a wide range, but alcohol is preferably employed at least in an amount to mix up olefin and aqueous hydrogen peroxide solution in a single liquid phase. As considering the cost for equipment to recover alcohol and the operation cost, it is preferable that the the amount of alcohol does not exceed five times of the minimum amount required for mixing in a single liquid phase, more preferably it does not exceed twice. Within the range of molar ratio of olefin/hydrogen peroxide from 1 to 5, the molar amount of alcohol required for mixing olefin and aqueous hydrogen peroxide solution in a single liquid phase, on the basis of 1 mole of hydrogen peroxide, usually increases as the molar

ratio of olefin/hydrogen peroxide increases, and the molar ratio of water/hydrogen peroxide increases.

As the aqueous hydrogen peroxide solution, a solution containing at least 20% by weight of hydrogen peroxide is preferable. As described above, the less the water content of the aqueous solution, that is the higher content of hydrogen peroxide in the aqueous solution, the less the amount of methanol required for diluting the reactant material in a single liquid phase. Thus, aqueous hydrogen peroxide solution containing at least 35% by weight of hydrogen peroxide is more preferably used. The upper limit of hydrogen peroxide content suitable for epoxidation in the aqueous hydrogen peroxide solution should be determined as considering the cost and safety of handling. In particular, anhydrous or nearly anhydrous hydrogen peroxide has poor safety of handling.

In order to mix and dilute allyl chloride and aqueous hydrogen peroxide solution, as the reactant material of epoxidation to produce epichlorohydrin, in a single liquid phase, an alcohol such as methanol is used as the diluent, and the amount of methanol required for single liquid phase is determined depending on the molar ratio of allyl chloride/hydrogen peroxide and that of water/hydrogen peroxide . For example, when the molar ratio of allyl chloride/hydrogen peroxide is from 1 to 5, minimum moles of methanol required for mixing up 35% by weight of aqueous hydrogen peroxide

solution with allyl chloride in a single liquid phase is about 6 to 10 times of the moles of hydrogen peroxide.

In the epoxidation reaction of olefin and hydrogen peroxide, water in the reaction product is originated from water produced by conversion from hydrogen peroxide via epoxidation and water contained in the aqueous hydrogen peroxide solution. The alcohol such as methanol in the reaction product comes from the alcohol such as methanol that was mixed with the reactant material in a required amount or more in order to mix up the reactant materials in a single liquid phase.

Water used as additional extraction solvent according to the present invention means water additionally incorporated in the organic solvent extraction stage, excluding the water existing in the reactant of olefin and hydrogen peroxide or in the reaction product. In the meanwhile, in the epoxidation reaction of allyl chloride, the amount of methanol is determined by liquid-liquid phase equilibrium, and the minimum amount of methanol is determined depending on the ratio of allyl chloride/hydrogen peroxide and the ratio of water/hydrogen peroxide. Eventually, the amount of methanol in the reaction product also reflects the amount of water, thereby the amount of water as additional extraction solvent can be determined in response to the amount of methanol in the reaction product. Water used as additional extraction solvent

is preferably employed in a molar ratio from 0.05 to 50, and more preferably in a molar ratio from 0.1 to 10 with respect to alcohol existing in the reaction product .

The extraction solvent employed in the process according to the present invention is preferably selected from organic compounds or halogenated organic compounds having excellent compatibility with epichlohydrin and allyl chloride, but low compatibility with water, and those having at least 5°C of difference of boiling point from that of epichlorohydrin in order to effectively isolate the final product from the extract of the reaction product. For efficient phase separation of the reaction product, the organic solvent is selected from those resulting in at least 0.01 g/cc of difference, and particularly at least 0.1 g/cc of difference in density between the extract and the extraction residue. The amount of organic extraction solvent supplied in the organic solvent extraction stage is preferably proportional to the amount of methanol in the reaction product. The amount of organic extraction solvent with respect to 1 mole of methanol is at least from 0.05 to about 50 moles, preferably from about 0.1 mole to 10 moles.

The organic solvent employed as the extraction solvent may be selected from (C1-C5) alkylbenzene, halogenated benzene, nitrobenzenes, halogenated (C3-C9) alkane, (C7-C15) alkane, halogenated (C3-C9) alkene, (C7-C15) alkene and mixtures

thereof. Said organic solvent is exemplified by o-xylene, m- xylene, p-xylene, ethylbenzene, 1, 3 , 5-trimethylbenzene, o- dichlorobenzene, m-dichlorobenzene, p-dichlorobenzene, 1,3,5- trichlorobenzene, o-chlorotoluene, m-chlorotoluene, p- chlorotoluene, 1, 2, 3-trichloropropane, nitrobenzene, n-nonane, n-decane, allyl chloride and mixtures thereof.

The solvent extraction process according to the present invention can be carried out in an extraction device consisting of at least one extraction stage (s), and the organic solvent and water used as additional extraction solvent are supplied in opposite directions to the extraction device to which the reaction product is supplied. Particularly, it is most preferable that water used as additional extraction solvent is supplied to the extract as a countercurrent , while the extraction solvent is supplied to the extraction residue as a countercurrent .

The operation temperature of said extraction device preferably is a temperature at which water as additional extraction solvent is not vaporized even in a small amount, commonly lower than 100 ^° C . The operation temperature of said extraction device preferably is a temperature at which water as additional extraction solvent is not frozen even in a small amount, commonly higher than 0°C. In order to inhibit decomposition of the reaction products, particularly to inhibit ring opening of epichlorohydrin, the extraction device

is operated preferably at a temperature not exceeding 80°C .

The operation pressure of the solvent extraction device preferably is higher than atmospheric pressure, but not exceeding 10 bar, though it may be operated under atmospheric pressure, or more or less.

As a separation method suitable for separating the extract from the extract residue, employed can be distillation, azeotropic distillation, extraction distillation or the like. After the extract is obtained from the reaction product according to the extraction process according to the invention, the extraction residue is separated into alcohol mixture having the main component of alcohol and aqueous mixture having the main component of water by means of fractional distillation, or the like. The alcohol mixture is recycled to the reaction process of allyl chloride and peroxide, while a part of the mixture having the main component of water is recycled to said extraction device to be employed as additional extraction solvent. After epichlorohydrin and allyl chloride are separated from the extract from the reaction product, allyl chloride is recycled to the reaction process, and the extraction solvent is recovered and returned to the extraction process, while the isolated epichlorohydrin is purified to provide pure epichlorohydrin.

Now the separation of the extract from the extraction residue is specifically described by referring to Fig. 3, but

the invention is not restricted thereto.

The extract (11) obtained from the solvent extraction process according to the present invention is subjected to fractional distillation in a device (20) for recovering allyl chloride, so that a mixture (12) having the main component of allyl chloride is recovered from the upper effluence of the tower for the first time. The mixture (12) having the main component of allyl chloride thus obtained is recycled to the reaction stage. If the allyl chloride mixture has much impurities, it is purified through a distillation tower for removing hard impurities and a distillation tower for removing intermediate impurities, and then returned to the reaction stage.

In the lower effluence of the device (20) for recovering allyl chloride, obtained is a mixture (13) having the main components of epichlorohydrin and the extraction solvent . The lower effluence (13) is subjected to fractional distillation in a device (30) for recovering the extraction solvent to provide a mixture (14) having the main component of epichlorohydrin as the upper effluence of the tower, as well as a mixture (15) having the main component of the extraction solvent as the lower effluence of the tower. At this time, it is preferable to maintain the operation pressure lower than atmospheric pressure so that the operation temperature at the lower part of the tower is not exceedingly raised.

The mixture (14) recovered from the device (30) for recovering the extraction solvent, which has the main component of epichlorohydrin, may comprise hard impurities and water. In order to remove the hard impurities and water, in a device (40) for removing hard impurities, the hard impurities

(16) and water are removed at the upper part of tower, while recovering epichlorohydrin (17) at the lower part of the tower.

The mixture (17) obtained from the device (40) for removing hard impurities, which has the main component of epichlorohydrin, is subjected to distillation in a device (50) for removing intermediate impurities, to obtain epichlorohydrin product (18) having the epichlorohydrin purity of at least 99% by weight as the upper effluence of the tower. As the lower effluence of the tower, intermediate impurities (19) are exhausted as the by-products. The extraction solvent (15) recovered as the lower effluence of the tower of the device (30) for recovering the extraction solvent is recycled to the solvent extraction device. At this time, in order to prevent accumulation of pollute in the extraction solvent, a part of the extraction solvent is discharged outward.

The extraction residue (21) is subjected to fractional distillation in a device (60) for recovering methanol, to recover a mixture (22) having the main component of methanol as the upper effluence of the tower, as well as a mixture (23) having the main component of water with organic compounds or

chlorinated organic compounds contained as the by-products, as the lower effluence of the tower. Methanol (22) recovered from the device (60) for recovering methanol is returned to the reaction process. The mixture (23) having the main component of water, which is recovered from the device (60) for recovering methanol is cooled and subjected to liquid-liquid phase separation in a decanter into an organic layer having the main components of organic compounds or chlorinated organic compounds and an aqueous layer having the main component of water. The organics are discharged as by-products, supplied to the device (30) for recovering the extraction solvent in order to recover epichlorohydrin contained in a trace amount or the extraction solvent, or supplied to the device (10) for solvent extraction. The aqueous layer having the main component of water can be separated into water and organic by-products by means of extraction distillation, solvent extraction or azeotropic distillation. A part of the water can be returned to the solvent extraction process and supplied to the solvent extraction device as additional extraction solvent.

[Description of Drawings]

Fig. 1 is a structural diagram of single stage extraction device according to the present invention, Fig. 2 is a structural diagram of multistage extraction

device according to the present invention, and

Fig. 3 is a process block diagram explaining the extraction process according to the present invention. description of the symbols of important parts in drawings>

1. original solution

2. extraction solvent

3. water as additional extraction solvent

4. extract 5. extraction residue

6. single stage extraction device

7. multistage extraction device

10. organic solvent extraction device

11. extract 12. mixture having the main component of allyl chloride

13. mixture having the main components of epichlorohydrin and extraction solvent

14. mixture having the main component of epichlorohydrin

15. mixture having the main component of extraction solvent

16. hard impurities in epichlorohydrin

17. mixture having the main component of epichlorohydrin with the hard impurities removed

18. epichlorohydrin product with intermediate impurities removed

19. intermediate impurities in epichlorohydrin

20. device for recovering allyl chloride

21. extraction residue

22. mixture having the main component of methanol 23. mixture having the main component of water

30. device for recovering extraction solvent

40. device for removing hard impurities

50. device for removing intermediate impurities

60. device for recovering methanol

Other and further objects, features and advantages of the invention will appear more fully from the following description.

Examples

Examples are described for more specific explanation of the present invention, but the invention is not limited to those Examples .

[Best Mode]

[Examples 1 to 5]

To the reaction product having the main components of epichlorohydrin, allyl chloride, water and methanol,

extraction solvent comprised of organic compound or halogenated organic compound is added. Then, liquid-liquid phase separation occurs into an extract having the main components of extraction solvent, epichlorohydrin and allyl chloride, and an extraction residue having the main components of methanol and water. The extract comprises some portion of methanol due to chemical affinity of methanol with the main components of the extract, while the extraction residue comprises some portion of extraction solvent due to chemical affinity between the main component of the extraction residue and the extraction solvent. In order to confirm the phenomenon of methanol extracted in the extract, a solvent extraction process was performed in an extraction device consisting of one extraction stage. To the product, 5 kinds of extraction solvents were added, respectively, and contents of the main components of the extract and the extraction residue were analyzed to calculate the extraction proportions. The results are reported in Table 1, wherein the extraction proportion is defined as a ratio of the weight of a certain component in the extract to the weight of the same in the reaction product.

An exemplary composition of the reaction product obtained via epoxidation by diluting allyl chloride and hydrogen peroxide with methanol, and mixing with TS-I catalyst (a titanium-containing silicalite compound) was 75%: 13%: 12% by

weight of methanol: epichlorohydrin: water. To the reaction product, twice the amount (by volume) of extraction solvent to the reaction product was added at room temperature. The resultant mixture was vigorously stirred to achieve complete mixing. After standing the mixture for a sufficient time, the contents of main components of the extract and the extraction residue thus obtained were analyzed to calculate the extraction proportions . The extraction solvent employed was o- dichlorobenzene, o-xylene, 1, 2, 3-trichloropropane, 1,3,5- trimethylbenzene and n-decane, respectively. The results are summarized in Table 1.

[Table 1] Extraction proportions of main components in Examples 1 to 5 (unit: kg/kg)

As can be seen from Table 1, in Examples 1, 2, 3 and 4 wherein the extraction proportion of epichlorohydrin was not less than 0.5, the extraction proportion of methanol was observed as not less than 0.07. Such a phenomenon that

methanol is accompanied with the extract occurs because some of methanol is dissolved in the extract due to chemical affinity of methanol with the extraction solvent and epichlorohydrin as the main components of the extract. The extraction proportion of methanol in Example 5 is lower than that of Examples 1, 2, 3 or 4. But since the extraction proportion of epichlorohydrin is also low in Example 5, n- decane is an extraction solvent having low practicality.

It can be seen from Examples 1 to 5 that organic compounds or halogenated organic compounds having good chemical affinity with epichlorohydrin and thus being suitable for extracting epichlorohydrin have some chemical affinity with methanol also, thereby at least a portion of methanol in the reaction product is extracted as the extract.

[Example 6 and 7]

An exemplary composition of the reaction product obtained by diluting the reactant containing allyl chloride and hydrogen peroxide in a molar ratio of 1:1 with methanol, and mixing and reacting with TS-I catalyst is epichlorohydrin 1.00 mole, water 2.68 moles and methanol 8.16 moles. To the reaction product, the same molar amount of o-dichlorobenzene or 1, 2, 3-trichloropropane as that of methanol is added at room temperature. The resultant mixture is vigorously stirred and stood for a sufficient time, the contents of main components

of the extract and the extraction residue thus obtained were analyzed to calculate the extraction proportions according to the same method as in Examples 1 to 5. The amount of water added as additional extraction solvent was adjusted in a molar ratio with respect to the amount of methanol in the reaction product. The experimental results are summarized in Tables 2 and 3.

[Table 2] Example 6: Results of solvent extraction with o-dichlorobenzene, extraction proportions (unit: kg/kg)

[Table 3] Example 7: Results of solvent extraction with 1, 2, 3-trichloropropane, extraction proportions (unit: kg/kg)

From the results of Examples 6 and 7 shown in Tables 2 and 3, it is found that the extraction proportion of methanol accompanied with the extract noticeably increases, as the

proportions of water as additional solvent and methanol in the reaction product increase, and accordingly, the extraction proportions of epichlorohydrin and the extraction solvent increases . From those results, it is confirmed that using o- dichlorobenzene or 1, 2, 3-trichloropropane as extraction solvent and adding water as additional extraction solvent can inhibit the phenomenon of accompanied extraction of methanol .

[Example 8]

Countercurrent multi-stage extraction using an extraction device consisting of three extraction stage

Though the solvent extraction was applied to the reaction product in an extraction device consisting of one extraction stage in Examples 1 to 7, a device for solvent extraction consisting of multiple extraction stage should be used so as to increase the extraction proportion of epichlorohydrin and allyl chloride into the extract. Thus, as a method to inhibit the phenomenon that methanol and water are accompanied with the extract in a solvent extraction device consisting of multiple stages, a solvent extraction process using water as additional solvent was simulated by using an extraction device consisting of three extraction stage according to a countercurrent multi-stage extraction process, and the extraction proportions were compared. The chemical process

simulator used for the simulating experiments was Aspen Plus 2004 from Aspen Tech (U.S.A.), and UNIQUAC model for physical property of phase equilibrium was used as a model explaining the behavior of liquid/liquid phase equilibrium. The parameters of UNIQUAC phase equilibrium model were obtained from optimization technique by using the results of various liquid/liquid phase separation experiments performed by the Applicants .

The composition of the main components of the reaction product obtained by diluting the reactant containing allyl chloride and hydrogen peroxide in a molar ratio of 2:1 with methanol, and mixing and reacting with TS-I catalyst is allyl chloride 1.00 mole, epichlorohydrin 1.00 mole, water 2.89 moles and methanol 5.91 moles. As the extraction solvent, 1, 2, 3-trichloropropane was used in the same molar amount as methanol in the reaction product. The method and results of the simulation experiment are shown in Table 4.

In the extraction device, relatively light extraction residue was discharged from the first stage among the three, while relatively heavy extract was discharged from the third stage. The operation temperature was 25 ^° C. The extraction solvent was supplied as a countercurrent to the extraction residue, while water as additional extraction solvent as a countercurrent to the extract .

[Table 4] Example 8: Results of countercurrent multistage extraction using an extraction device consisting of three extraction stage

[Example 9]

Example 9 was carried out according to the process described in Example 8, but using an extraction device with seven extraction stage in the countercurrent multi-stage extraction process.

Relatively light extraction residue was discharged from the first, while relatively heavy extract was discharged from

the seventh stage. The operation temperature was 25°C . The extraction solvent was supplied as a countercurrent to the extraction residue, while water as additional extraction solvent as a countercurrent to the extract .

[Table 5] Example 9: Results of countercurrent multistage extraction using an extraction device consisting of seven extraction stage

In Example 8, when water as additional solvent was not added in the solvent extraction device consisting of three

extraction stages, the extraction proportion of methanol was 0.503, while it was lowered to 0.039 when supplying water as additional solvent. When water was added as additional solvent, the extraction proportion of water contained in the reaction product was also lowered from 0.169 to 0.046. As a secondary- effect of adding water as additional solvent, it is found that the extraction proportion of the extraction solvent increases from 0.971 to 0.986. In the solvent extraction device consisting of seven extraction layer according to Example 9, when water as additional extraction solvent was not added, the extraction proportion of methanol was 0.505. When water was added as additional extraction solvent as a countercurrent with the extract, the extraction proportion of methanol was lowered to 0.003. When water was supplied as additional extraction solvent, the extraction proportion of water from the reaction product was lowered from 0.170 to 0.040.

From the results of Examples 8 and 9, it is confirmed that the phenomenon of methanol and water from the reaction product accompanied with the extract can be inhibited by supplying the extraction solvent as a countercurrent with the extraction solvent and by supplying water as additional extraction solvent as a countercurrent with the extract . When water is not supplied as additional solvent, the extraction proportions of methanol and water is not lowered if the number of extraction stages increased from 3 stages to 7. However,

when water was supplied as additional solvent, the extraction proportion of methanol was lowered from 0.039 to 0.003 as the number of extraction stages increases from 3 stages to 7.

From Examples 6 and 7, it is confirmed that the extraction proportion of methanol can be controlled by- adjusting the molar ratio of water as additional extraction solvent to methanol in the reaction product, in order to lower the extraction proportion of methanol into the extract . From Examples 8 and 9, it is confirmed that the extraction proportion of methanol can be controlled according to the same method in a solvent extraction device consisting of multiple extraction stages.

[industrial Applicability] As described above, the solvent extraction process according to the invention using water as additional extraction solvent can noticeably lower the extraction proportion of alcohol into the extract, as compared to the solvent extraction process using only the extraction solvent. Thus, the difficulties in designing and operation during the separation of olefin, oxirane, and extraction solvent in the extract, owing to alcohol and water contained in the extract, can be advantageously overcome. By means of a series of separation of the extract having low content of alcohol and water that was recovered by solvent extraction process, from

the extraction residue having main components of alcohol and water, according to the present invention, high purity of oxirane compound can be obtained. At least a part of olefin, extraction solvent, alcohol and water can be advantageously reused during the process of preparing the oxirane compound.