Method and system for producing epoxyalkane

Abstract

A method for producing an epoxyalkane includes the step of separating a stream containing an epoxyalkane and an extracting agent in a separation column having a column kettle reboiler. A part of a stream in the column kettle of the separation column enters an extracting agent purifier and is treated to obtain a gas phase light fraction that returns to the separation column and a liquid phase heavy fraction that is subjected to a post-treatment. The method can be used in the industrial production of an epoxyalkane.

Claims

1. A method for producing an epoxyalkane, comprising: 1) sending a crude product stream containing an epoxyalkane and an extractant to an extractive rectification column for extractive distillation, obtaining a crude epoxyalkane stream containing the epoxyalkane and the extractant; 2) introducing the crude epoxyalkane stream into a separation column, obtaining an epoxyalkane stream from a top of the separation column and an extractant stream from a bottom of the separation column; 3) dividing the extractant stream into a first stream, a second stream, and a third stream, heating the first stream in a column reboiler connected to the separation column and returning the heated first stream to the separation column, purifying the third stream to remove heavy components having boiling points higher than that of the extractant in an extractant purifier, and obtaining a vapor phase or a vapor-liquid mixture, wherein the column reboiler is a thermosyphon reboiler, a kettle-type reboiler, and a forced circulation type reboiler; and 4) returning the vapor phase or the vapor-liquid mixture to the separation column and feeding the second stream to the extractive rectification column, wherein the third stream accounts for 2-20% by weight of a total amount of the extractant stream, the epoxyalkane stream contains not less than 99.95% by weight of the epoxyalkane and not higher than 0.05% by weight of the extractant, and the extractant stream contains not less than 99% by weight of the extractant and not higher than 1% by weight of the epoxyalkane.

2. The method according to claim 1, wherein the extractant purifier is a distillation column or a second reboiler.

3. The method according to claim 2, wherein the extractant purifier is the second reboiler.

4. The method according to claim 3, wherein the second reboiler is a kettle-type reboiler.

5. The method according to claim 3, wherein the second reboiler is located at a middle part or the bottom of the separation column.

6. The method according to claim 1, wherein a temperature difference between the first stream and the third stream is ≤5° C.

7. The method according to claim 1, wherein a temperature difference between the first stream and the third stream is ≤3° C.

8. The method according to claim 1, wherein, in the separation column, a temperature of a vapor phase at the top of the separation column is within a range of 60-130° C., a pressure is 0.04-0.40 MPaG, and a number of theoretical plates is within a range of 15-80.

9. The method according to claim 1, wherein a ratio of the extractant to the epoxyalkane in a stream containing epoxyalkane and extractant is (2-15): 1, based on a mole percent.

10. The method according to claim 1, wherein a ratio of the extractant to the epoxyalkane a stream containing epoxyalkane and extractant is (3-10): 1, based on a mole percent.

11. The method according to claim 1, wherein a ratio of the extractant to the epoxyalkane a stream containing epoxyalkane and extractant is (5-7): 1, based on a mole percent.

12. The method according to claim 1, wherein the epoxyalkane is selected from propylene oxide, butylene oxide, and isomers of butylene oxide.

13. The method according to claim 1, wherein the epoxyalkane is butylene oxide.

14. The method according to claim 1, wherein the epoxyalkane is 1,2-butylene oxide.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a schematic flowchart of a preferred embodiment of the method according to the present disclosure.

(2) FIG. 2 is a schematic flowchart of a method provided in the prior art document U.S. Pat. No. 4,402,794.

(3) In the drawings, the same components are represented with the same reference signs. The drawings are not necessarily illustrated according to the actual scale.

DESCRIPTION OF THE REFERENCE SIGNS

(4) 1. Feed stream 2. Extractant stream 3. Epoxyalkane product stream 4. Column kettle reboiler feed stream 5. Column kettle reboiler discharge stream 6. Extractant purifier feed stream 7. Heavy component impurity stream-effluent stream 8. Extractant purifier discharge stream 31. 1,2-butylene oxide product stream A. Column kettle reboiler B. Extractant purifier C. Separation column

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

(5) The entirety of publications, patent applications, patents and other reference literatures mentioned in the description is hereby incorporated by reference herein. Unless otherwise defined, each of the technologies and scientific terminologies used in the description has meanings as commonly understood by those skilled in the art. In case of conflict, the definitions in the description shall prevail.

(6) When the description uses the prefix “well-known among those skilled in the art”, “prior art” or similar terms to define materials, substances, methods, steps, devices or components, the objects defined by the prefix cover those routinely used in the technical field when the invention is presented, but also cover those which are not commonly used at present and will become generally recognized in the art for being suitable for the similar purposes.

(7) Apart from the content which is explicitly stated in the context of the description, any matter or item not mentioned herein is directly applied to those well-known in the art without a need of making any change. Moreover, any embodiment described herein can be freely combined with one or more other embodiments described herein, any of the thereby formed technical solutions or ideas shall be regarded as a part of the original disclosure or original record of the present invention, instead of being considered as the new content which has not been disclosed or anticipated herein, unless those skilled in the art believe that the combination is obviously unreasonable.

(8) The terminals and any value of the ranges disclosed herein are not limited to the precise ranges or values, such ranges or values shall be comprehended as comprising the values adjacent to the ranges or values. As for numerical ranges, the endpoint values of the various ranges, the endpoint values and the individual point value of the various ranges, and the individual point values may be combined with one another to yield one or more new numerical ranges, which should be considered as specifically disclosed herein.

(9) Unless explicitly stated in the present disclosure, the expressions “first”, “second” and “third” do not represent the order of priority, they are only used for the distinguishing purpose, for example, the expressions “first”, “second” and “third” in the terms “first stream”, “second stream” and “third stream” are only used for distinguishing the three parts of the same streams which will be sent to different places.

(10) It should be noted that the production process of epoxyalkane includes units such as reaction, separation and refining of epoxyalkane. The present disclosure mainly relates to an epoxyalkane refining unit, and particularly relates to a purification process of an extractant therein. The invention involves with an epoxyalkane refining unit in an epoxyalkane production process, and particularly involves with an epoxyalkane refining unit adopting an extractive rectification mode.

(11) In general, the crude epoxyalkane product and the extractant are subjected to extractive rectification in an extractive rectification column, and a column kettle liquid containing the epoxyalkane and the extractant is discharged from the rectification column, preferably discharging from the rectification column kettle and entering the separation column thereby obtaining an epoxyalkane product and an extractant, wherein a part of the extractant is returned to the separation column through a column kettle reboiler, a majority of the extractant may be determined that the extractant is directly recycled or purified (regenerated) based on the purity of the extractant or the concentration of impurities in the extractant. The diols and alcohol ethers will continuously generate and accumulate in cycles during the extractive distillation process in the presence of water and methanol. It is generally believed that the extraction capacity will decrease when the concentration of impurities in the extractant reaches 10% by weight. In order to ensure the separation effect of extractive rectification and reduce energy consumption in the separation process, the concentration of impurities in the extractant is generally controlled to be less than 2% by weight, that is, when the concentration of impurities exceeds 2% by weight, the extractant shall not be directly recycled and reused, but subjecting to the purification treatment. As for the general industrial installations at present, the extractants are replenished in batches for about 2-3 years.

(12) The inventors of the present disclosure have discovered that due to an addition of a small extractant purifier, a part of the extractant is purified and returned to the separation column, thereby improving purity of the circulating extractant and reducing loss of the extractant and the energy consumption of the separation process. The extractant purifier may be a distillation column or a reboiler. Preferably, the extractant purifier is a reboiler, and further preferably a kettle-type reboiler. The purified extractant may return to the separation column without requiring a further power device such as a power pump, such that the economic efficiency is significantly improved.

(13) The preferred embodiment of the present disclosure is to additionally arrange one or more small reboiler at the bottom of a conventional separation column provided with a reboiler, that is, two or more reboilers are disposed in the kettle part of the separation column, which is suitable for the construction of a new device and for the upgrading and reconstruction of old equipment. For new device, such an arrangement can save equipment investment, reduce the loss of extractant and improve product quality; it is also particularly suitable for the upgrading and renovation of old devices, it generates obvious effects in term of minor modification, small land occupation, low investment and reduced loss of extractant.

(14) Preferably, the extractant purifier is disposed between the lower part of an inlet of the separation column for introducing the stream containing epoxyalkane and extractant and the column kettle of the separation column. When the position is closer to the column kettle, the lower is the content of epoxyalkane, the higher is the content of the extractant and the impurities such as diols and alcohol ether, it is more beneficial to improve purity of the extractant, thus it is preferable that the extractant purifier is arranged underneath the feed position of the separation column. Preferably, the heights of the column kettle reboiler and the extractant purifier relative to the column kettle of the separation column are arranged such that the temperature difference between the column kettle reboiler and the extractant purifier is 5° C. In the present disclosure, the main function of the extractant purifier is to purify the extractant. The ideal condition resides in that there is no temperature difference between the column kettle reboiler and the extractant purifier relative to the column kettle of the separation column, however, in view of various influencing factors in the actual industrial production process, the present disclosure allows the temperature difference between the column kettle reboiler and the extractant purifier to be ≤5° C., preferably ≤3° C.

(15) According to a particularly preferred embodiment, both the column kettle reboiler and the extractant purifier of the present disclosure are arranged at the column kettle of the separation column. Such an arrangement can significantly improve purity of the extractant, reduce loss of the extractant and increase yield of the epoxyalkane.

(16) Preferably, the number of theoretical plates in the separation column is within a range of 15-80, when the number of theoretical plates is counted from the column top to the column kettle, the feed position of the extractant purifier is located at the zero to 4.sup.th plates from the bottom, preferably the zero to 2.sup.nd plates from the bottom.

(17) Preferably, the ratio of the heat transfer area of the column kettle reboiler and the boiler serving as the extractant purifier is within a range of (2-5):1. That is, the ratio of the flow rate of material entering the column kettle reboiler to the flow rate of material entering the reboiler serving as the extractant purifier is within a range of (2-5):1.

(18) The embodiment only needs to add one or more reboiler on the basis of the existing epoxyalkane production device, and the reboiler may be connected with the separation column through a simple pipeline, an additional power pump is not required for returning the purified extractant to the separation column, thus it is easy to rebuild, and requires small land occupation, low investment and reduced energy consumption.

(19) The additionally arranged reboiler divides the third stream into the low-boiling components, and the high-boiling components with a boiling point higher than the extractant. The low-boiling components are mainly extractants, which are returned to the separation column for recycling in the form of vapor phase or vapor-liquid mixture; the high-boiling components with a boiling point higher than the extractant are mainly impurities such as diols and alcohol ethers, and are discharged from the system.

(20) In order to further improve purity of the extractant in a method of the present disclosure, it is preferable that the first stream accounts for 2-20% by weight of the total amount of the column kettle stream of the separation column.

(21) Preferably, the content of epoxyalkane in the stream which is obtained from the column top and mainly consisting of epoxyalkane is not less than 99.95% by weight, and the content of extractant is not higher than 0.05% by weight; the content of extractant in the stream which is obtained from the column kettle and mainly consisting of extractant is not less than 99% by weight, and the content of epoxyalkane is not higher than 1% by weight.

(22) Preferably, the operating conditions of the separation column include: the temperature of the vapor phase at the column top is within a range of 60-130° C., the temperature at the column top is 30-80° C., and the pressure is 0.04-0.40 MPaG.

(23) Preferably, the ratio of the extractant to the epoxyalkane in a stream containing epoxyalkane and extractant is (2-15):1, more preferably (3-10):1, and further preferably (5-7):1, based on the mole percent.

(24) The column kettle reboiler is preferably any one of the group consisting of a thermosyphon reboiler, a kettle-type reboiler and a forced circulation type reboiler.

(25) Preferably, the epoxyalkane is propylene oxide, butylene oxide or isomers of butylene oxide; more preferably, the epoxyalkane is butylene oxide; particularly preferably, the epoxyalkane is 1,2-butylene oxide.

(26) In the present disclosure, the stream containing epoxyalkane and extractant may be derived from the extraction product stream obtained by extractive rectification of the olefin epoxidation reaction product. Preferably, the content of epoxyalkane in the stream is 5-25% by weight.

(27) The extractants used for the purification of epoxyalkanes are well known in the art. Generally, C7-C20 straight and branched hydrocarbons and/or diols are used as the extractant. From an economic point of view, a mixture of C8 straight and branched alkanes is used as the extractant, and the C8 straight and branched alkanes may be N-octane, isooctane, and 2-methylheptane for example. From the sake of reducing cost of the extractant, it is preferable to select a mixture.

(28) According to the present disclosure, after the stream containing epoxyalkane and extractant is rectified in the separation column, the column kettle stream of the separation column contains the extractant and heavy components. Taking butylene oxide as an example, the heavy components include 1,2-butanediol, 1-butanediol monomethyl ether, 2-butanediol monomethyl ether, dimer butylene oxide, (poly)butylene oxide, poly-1,2-butanediol ether and derivatives thereof, or mixtures thereof. Taking propylene oxide as an example, the heavy components include 1,2-propylene glycol, propylene glycol monomethyl ether, dimeric propylene oxide, (poly)propylene oxide, polypropylene glycol ether and derivatives thereof, or mixtures thereof.

(29) It should be noted that the separation efficiency of extractive distillation is constant when the purity of the extractant is unchanged. However, the present disclosure emphasizes that during the refining process, side reactions may occur to generate impurities diol and its derivatives, and the production of the impurities is unavoidable, and the impurities will accumulate and circulate in the system. The impurities have an adverse effect on extractive rectification and reduce extraction efficiency of the extractant. If the extractant is directly discharged to the outside, when the heavy component impurities in the extractant are as low as 2%, the effluent extractant accounts for 98%, thus the loss of extractant is large; when the content of heavy component impurities is as high as 10%, the effluent extractant still accounts for 90%, the loss of extractant is slightly reduced, but the extraction efficiency of the extractant has decreased significantly, resulting in an increased solvent ratio of the extractive rectification column and an increase in energy consumption. In the present disclosure, merely by adding a small extractant purifier, the concentration of heavy components in the effluent stream (that is, the liquid-phase heavy component obtained in the extractant purifier) can be increased by 1 time or more, the amount of effluent extractant loss is reduced by more than half. By adopting the present disclosure, under the condition that the external discharge amount of the extractant is the same, the content of heavy component impurities in the circulating extractant is 50% of the direct external discharge scheme after a long period of operation. If the direct external discharge scheme is adopted, the yield of the epoxyalkane must be reduced in order to improve the product quality of the epoxyalkane, otherwise the product quality cannot be guaranteed.

(30) The present disclosure is described in detail below with reference to the drawings, it should be noted that the protection scope of the present disclosure is not limited thereto, but being determined by the appended claims.

(31) As illustrated in FIG. 1 of the present disclosure, the crude epoxyalkane product and the extractant are pumped to an extractive rectification column for carrying out the extractive rectification, and the raffinate is discharged from the top of the column, and the feed stream 1 containing epoxyalkane and extractant is discharged from the column kettle into the separation column C, the epoxyalkane product stream 3 is removed from the top of the separation column, the extractant stream 2 is removed from the kettle section of the separation column, the bottom of the separation column C is provided with a column kettle reboiler A and an extractant purifier B, the column kettle reboiler feed stream 4 sends a part of the column kettle stream to the column kettle reboiler A and obtain the column kettle reboiler discharge stream 5 after heating, the column kettle reboiler discharge stream 5 is recycled to the lower part of separation column C; the extractant purifier feed stream 6 sends a part of the column kettle stream to the extractant purifier B and heats it to obtain the extractant purifier discharge stream 8 as the vapor phase light component and the heavy component impurity stream-effluent stream 7 as the heavy component impurity stream, wherein the extractant purifier discharge stream 8 returns to the lower part of the separation column C, and the heavy component impurity stream-effluent stream 7 is discharged from the bottom of the extractant purifier B.

(32) In contrast, as illustrated in FIG. 2, the feed stream 1 containing 1,2-butylene oxide and extractant is sent to the separation column C, and the 1,2-butylene oxide product stream 31 is removed from the top of the separation column, the extractant stream 2 is removed from the kettle part of the separation column, the bottom of the separation column C is provided with a column kettle reboiler A, the column kettle reboiler feed stream 4 sends the column kettle liquid to the column kettle reboiler A and sends the column kettle reboiler discharge stream 5 obtained after heating to the lower part of the separation column C, a stream is divided from the extractant stream 2 as the heavy component impurity stream-effluent stream 7 and is discharged from the separation system. Because a part of the extractant and heavy components are discharged to reduce accumulation of the reaction by-products and derivatives in the extractant, a large amount of the extractant will be lost.

(33) The present disclosure has no particular restrictions on the specific operating conditions for the crude product stream containing epoxyalkane and the extractant stream entering the first rectification column for performing rectification. For example, it can be carried out with the method provided in the document CN108017598A. The content will not be repeated here.

(34) The present disclosure will be further described below through specific examples. The results in the following examples and comparative examples are taken from the results after 800 hours of stable operation of the system. The purity of materials is measured by the Chinese national standard gas chromatography GB/T9722-2006 method. The following term “wtppm” refers to the concentration of ppm by weight.

Example 1

(35) According to the process flow shown in FIG. 1, the operating conditions of the separation column comprise: the vapor phase temperature at the top of the column is 72° C., the temperature at the column top is 33° C., the pressure is 0.04 MPaG, and the number of theoretical plates in separation column is 65; the extractant is N-octane, the molar ratio of extractant to 1,2-butylene oxide in the feed stream containing 1,2-butylene oxide and extractant is 8:1; the column kettle reboiler A of the separation column is a thermosyphon reboiler located below the last column plate, the extractant purifier B is a kettle-type reboiler located on the 66.sup.th column plate; the ratio of the heat transfer area of the column kettle reboiler A to that of the extractant purifier B is 5:1; the ratio of the part entering the extractant purifier relative to the column kettle stream of the separation column is 3% by weight. The temperature difference between the column kettle reboiler A and the extractant purifier B during the whole process is ≤3° C.

(36) The 1,2-butylene oxide stream at the top of the separation column has a purity of 99.99%, a content of water ≤10 wtppm, a content of acetaldehyde+propionaldehyde ≤10 wtppm, a content of acid ≤5 wtppm and a recovery rate of 99.80%; the extractant in the kettle part of the separation column has a purity of 99.5%, the loss rate of the extractant is 0.020%.

Example 2

(37) According to the process flow shown in FIG. 1, the operating conditions of the separation column comprise: the vapor phase temperature at the top of the column is 80° C., the temperature at the column top is 35° C., the pressure is 0.08 MPaG, and the number of theoretical plates in separation column is 60; the extractant is N-octane, the molar ratio of extractant to 1,2-butylene oxide in the feed stream containing 1,2-butylene oxide and extractant is 7:1; the column kettle reboiler A of the separation column is a thermosyphon reboiler located below the last column plate, the extractant purifier B is a kettle-type reboiler located on the 61.sup.st column plate; the ratio of the heat transfer area of the column kettle reboiler A to that of the extractant purifier B is 5:1; the ratio of the part entering the extractant purifier relative to the column kettle stream of the separation column is 5% by weight. The temperature difference between the column kettle reboiler A and the extractant purifier B during the whole process is ≤2.4° C.

(38) The 1,2-butylene oxide stream at the top of the separation column has a purity of 99.98%, a content of water ≤10 wtppm, a content of acetaldehyde+propionaldehyde ≤10 wtppm, a content of acid ≤5 wtppm and a recovery rate of 99.82%; the extractant in the kettle part of the separation column has a purity of 99.5%, the loss rate of the extractant is 0.025%.

Example 3

(39) According to the process flow shown in FIG. 1, the operating conditions of the separation column comprise: the vapor phase temperature at the top of the column is 89° C., the temperature at the column top is 40° C., the pressure is 0.12 MPaG, and the number of theoretical plates in separation column is 60; the extractant is N-octane, the molar ratio of extractant to 1,2-butylene oxide in the feed stream containing 1,2-butylene oxide and extractant is 6:1; the column kettle reboiler A of the separation column is a thermosyphon reboiler located below the last column plate, the extractant purifier B is a kettle type reboiler located on the 61.sup.st column plate; the ratio of the heat transfer area of the column kettle reboiler A to that of the extractant purifier B is 5:1; the ratio of the part entering the extractant purifier relative to the column kettle stream of the separation column is 8% by weight. The temperature difference between the column kettle reboiler A and the extractant purifier B during the whole process is ≤2° C.

(40) The 1,2-butylene oxide stream at the top of the separation column has a purity of 99.95%, a content of water ≤10 wtppm, a content of acetaldehyde+propionaldehyde ≤10 wtppm, a content of acid ≤5 wtppm and a recovery rate of 99.85%; the extractant in the kettle part of the separation column has a purity of 99.5%, the loss rate of the extractant is 0.028%.

Example 4

(41) According to the process flow shown in FIG. 1, the operating conditions of the separation column comprise: the vapor phase temperature at the top of the column is 96° C., the temperature at the column top is 45° C., the pressure is 0.16 MPaG, and the number of theoretical plates in separation column is 55; the extractant is N-octane, the molar ratio of extractant to 1,2-butylene oxide in the feed stream containing 1,2-butylene oxide and extractant is 5:1; the column kettle reboiler A of the separation column is a thermosyphon reboiler located below the last column plate, the extractant purifier B is a kettle-type reboiler located on the 56.sup.th column plate; the ratio of the heat transfer area of the column kettle reboiler A to that of the extractant purifier B is 5:1; the ratio of the part entering the extractant purifier relative to the column kettle stream of the separation column is 10% by weight. The temperature difference between the column kettle reboiler A and the extractant purifier B during the whole process is ≤1.6° C.

(42) The 1,2-butylene oxide stream at the top of the separation column has a purity of 99.95%, a content of water ≤10 wtppm, a content of acetaldehyde+propionaldehyde ≤10 wtppm, a content of acid ≤5 wtppm and a recovery rate of 99.89%; the extractant in the kettle part of the separation column has a purity of 99.5%, the loss rate of the extractant is 0.029%.

Example 5

(43) According to the process flow shown in FIG. 1, the operating conditions of the separation column comprise: the vapor phase temperature at the top of the column is 101° C., the temperature at the column top is 50° C., the pressure is 0.20 MPaG, and the number of theoretical plates in separation column is 50; the extractant is N-octane, the molar ratio of extractant to 1,2-butylene oxide in the feed stream containing 1,2-butylene oxide and extractant is 4:1; the column kettle reboiler A of the separation column is a thermosyphon reboiler located below the last column plate, the extractant purifier B is a kettle-type reboiler located on the 51.sup.st column plate; the ratio of the heat transfer area of the column kettle reboiler A to that of the extractant purifier B is 5:1; the ratio of the part entering the extractant purifier relative to the column kettle stream of the separation column is 13% by weight. The temperature difference between the column kettle reboiler A and the extractant purifier B during the whole process is ≤1.2° C.

(44) The 1,2-butylene oxide stream at the top of the separation column has a purity of 99.98%, a content of water ≤0.02%, a content of acetaldehyde+propionaldehyde ≤0.005%, a content of acid ≤0.003% and a recovery rate of 99.86%; the extractant in the kettle part of the separation column has a purity of 99.5%, the loss rate of the extractant is 0.032%.

Example 6

(45) According to the process flow shown in FIG. 1, the operating conditions of the separation column comprise: the vapor phase temperature at the top of the column is 106° C., the temperature at the column top is 55° C., the pressure is 0.24 MPaG, and the number of theoretical plates in separation column is 45; the extractant is C8 alkane mixture, the molar ratio of extractant to 1,2-butylene oxide in the feed stream containing 1,2-butylene oxide and extractant is 4:1; the column kettle reboiler A of the separation column is a thermosyphon reboiler located below the last column plate, the extractant purifier B is a kettle-type reboiler located on the 46.sup.th column plate; the ratio of the heat transfer area of the column kettle reboiler A to that of the extractant purifier B is 5:1; the ratio of the part entering the extractant purifier relative to the column kettle stream of the separation column is 15% by weight. The temperature difference between the column kettle reboiler A and the extractant purifier B during the whole process is ≤1° C.

(46) The 1,2-butylene oxide stream at the top of the separation column has a purity of 99.99%, a content of water ≤10 wtppm, a content of acetaldehyde+propionaldehyde ≤10 wtppm, a content of acid ≤5 wtppm and a recovery rate of 99.85%; the extractant in the kettle part of the separation column has a purity of 99.5%, the loss rate of the extractant is 0.035%.

Example 7

(47) According to the process flow shown in FIG. 1, the operating conditions of the separation column comprise: the vapor phase temperature at the top of the column is 111° C., the temperature at the column top is 60° C., the pressure is 0.28 MPaG, and the number of theoretical plates in separation column is 40; the extractant is N-octane, the molar ratio of extractant to 1,2-butylene oxide in the feed stream containing 1,2-butylene oxide and extractant is 6:1; the column kettle reboiler A of the separation column is a thermosyphon reboiler located below the last column plate, the extractant purifier B is a kettle-type reboiler located on the 41.sup.st column plate; the ratio of the heat transfer area of the column kettle reboiler A to that of the extractant purifier B is 4:1; the ratio of the part entering the extractant purifier relative to the column kettle stream of the separation column is 7% by weight. The temperature difference between the column kettle reboiler A and the extractant purifier B during the whole process is ≤1.8° C.

(48) The 1,2-butylene oxide stream at the top of the separation column has a purity of 99.98%, a content of water ≤10 wtppm, a content of acetaldehyde+propionaldehyde ≤10 wtppm, a content of acid ≤5 wtppm and a recovery rate of 99.85%; the extractant in the kettle part of the separation column has a purity of 99.5%, the loss rate of the extractant is 0.034%.

Example 8

(49) According to the process flow shown in FIG. 1, the operating conditions of the separation column comprise: the vapor phase temperature at the top of the column is 111° C., the temperature at the column top is 65° C., the pressure is 0.32 MPaG, and the number of theoretical plates in separation column is 30; the extractant is N-octane, the molar ratio of extractant to 1,2-butylene oxide in the feed stream containing 1,2-butylene oxide and extractant is 6:1; the column kettle reboiler A of the separation column is a thermosyphon reboiler located below the last column plate, the extractant purifier B is a kettle-type reboiler located on the 31.sup.st column plate; the ratio of the heat transfer area of the column kettle reboiler A to that of the extractant purifier B is 3:1; the ratio of the part entering the extractant purifier relative to the column kettle stream of the separation column is 6% by weight. The temperature difference between the column kettle reboiler A and the extractant purifier B during the whole process is ≤1.7° C.

(50) The 1,2-butylene oxide stream at the top of the separation column has a purity of 99.98%, a content of water ≤10 wtppm, a content of acetaldehyde+propionaldehyde ≤10 wtppm, a content of acid ≤5 wtppm and a recovery rate of 99.86%; the extractant in the kettle part of the separation column has a purity of 99.5%, the loss rate of the extractant is 0.033%.

Example 9

(51) According to the process flow shown in FIG. 1, the operating conditions of the separation column comprise: the vapor phase temperature at the top of the column is 119° C., the temperature at the column top is 70° C., the pressure is 0.36 MPaG, and the number of theoretical plates in separation column is 25; the extractant is N-octane, the molar ratio of extractant to 1,2-butylene oxide in the feed stream containing 1,2-butylene oxide and extractant is 6:1; the column kettle reboiler A of the separation column is a thermosyphon reboiler located below the last column plate, the extractant purifier B is a kettle-type reboiler located on the 26.sup.th column plate; the ratio of the heat transfer area of the column kettle reboiler A to that of the extractant purifier B is 2:1; the ratio of the part entering the extractant purifier relative to the column kettle stream of the separation column is 6% by weight. The temperature difference between the column kettle reboiler A and the extractant purifier B during the whole process is ≤1.8° C.

(52) The 1,2-butylene oxide stream at the top of the separation column has a purity of 99.95%, a content of water ≤0.02%, a content of acetaldehyde+propionaldehyde ≤0.005%, a content of acid ≤0.003% and a recovery rate of 99.87%; the extractant in the kettle part of the separation column has a purity of 99.5%, the loss rate of the extractant is 0.035%.

Example 10

(53) The example is performed using a process similar to that of [Example 9], except that the column kettle reboiler A of this example uses a kettle-type reboiler, specifically:

(54) According to the process flow shown in FIG. 1, the operating conditions of the separation column comprise: the vapor phase temperature at the top of the column is 119° C., the temperature at the column top is 70° C., the pressure is 0.36 MPaG, and the number of theoretical plates in separation column is 25; the extractant is N-octane, the molar ratio of extractant to 1,2-butylene oxide in the feed stream containing 1,2-butylene oxide and extractant is 6:1; the column kettle reboiler A of the separation column is a kettle-type reboiler located below the last column plate, the extractant purifier B is a kettle-type reboiler located on the 26.sup.th column plate; the ratio of the heat transfer area of the column kettle reboiler A to that of the extractant purifier B is 2:1; the ratio of the part entering the extractant purifier relative to the column kettle stream of the separation column is 3% by weight. The temperature difference between the column kettle reboiler A and the extractant purifier B during the whole process is ≤1.8° C.

(55) The 1,2-butylene oxide stream at the top of the separation column has a purity of 99.95%, a content of water ≤0.02%, a content of acetaldehyde+propionaldehyde ≤0.005%, a content of acid ≤0.003% and a recovery rate of 99.87%; the extractant in the kettle part of the separation column has a purity of 99.5%, the loss rate of the extractant is 0.035%.

Example 11

(56) The example is performed using a process similar to that of [Example 9], except that the column kettle reboiler A of this example uses a forced circulation type reboiler, specifically:

(57) According to the process flow shown in FIG. 1, the operating conditions of the separation column comprise: the vapor phase temperature at the top of the column is 119° C., the temperature at the column top is 70° C., the pressure is 0.36 MPaG, and the number of theoretical plates in separation column is 25; the extractant is N-octane, the molar ratio of extractant to 1,2-butylene oxide in the feed stream containing 1,2-butylene oxide and extractant is 6:1; the column kettle reboiler A of the separation column is a forced circulation type reboiler located below the last column plate, the extractant purifier B is a kettle-type reboiler located on the 26.sup.th column plate; the ratio of the heat transfer area of the column kettle reboiler A to that of the extractant purifier B is 2:1; the ratio of the part entering the extractant purifier relative to the column kettle stream of the separation column is 6% by weight. The temperature difference between the column kettle reboiler A and the extractant purifier B during the whole process is ≤1.8° C.

(58) The 1,2-butylene oxide stream at the top of the separation column has a purity of 99.95%, a content of water ≤0.02%, a content of acetaldehyde+propionaldehyde ≤0.005%, a content of acid ≤0.003% and a recovery rate of 99.87%; the extractant in the kettle part of the separation column has a purity of 99.5%, the loss rate of the extractant is 0.035%.

Example 12

(59) This example is performed using a process similar to that of [Example 9], except that the column kettle reboiler A of this example uses a forced circulation type reboiler, specifically:

(60) According to the process flow shown in FIG. 1, the operating conditions of the separation column comprise: the vapor phase temperature at the top of the column is 119° C., the temperature at the column top is 70° C., the pressure is 0.36 MPaG, and the number of theoretical plates in separation column is 26; the extractant is N-octane, the molar ratio of extractant to 1,2-butylene oxide in the feed stream containing 1,2-butylene oxide and extractant is 6:1; the column kettle reboiler A of the separation column is a forced circulation type reboiler located below the last column plate, the extractant purifier B is a kettle-type reboiler located on the 24.sup.th column plate; the ratio of the heat transfer area of the column kettle reboiler A to that of the extractant purifier B is 2:1; the ratio of the part entering the extractant purifier relative to the column kettle stream of the separation column is 6% by weight. The temperature difference between the column kettle reboiler A and the extractant purifier B during the whole process is ≤1.8° C.

(61) The 1,2-butylene oxide stream at the top of the separation column has a purity of 99.95%, a content of water ≤0.02%, a content of acetaldehyde+propionaldehyde ≤0.005%, a content of acid ≤0.003% and a recovery rate of 99.85%; the extractant in the kettle part of the separation column has a purity of 99.5%, the loss rate of the extractant is 0.037%.

Comparative Example 1

(62) According to the process flow shown in FIG. 2, the operating conditions of the separation column comprise: the temperature of vapor phase at the column top is 103° C., and the pressure is 0.22 MPaG, the number of theoretical plates in separation column is 60; the extractant is N-octane, and a ratio of the extractant and 1,2-butylene oxide is 8:1 in a feed stream containing 1,2-butylene oxide and extractant based on the percentage by weight; the separation column reboiler A is a forced circulation type reboiler.

(63) The 1,2-butylene oxide stream at the top of the separation column has a purity of 99.95%, the recovery rate is 96.38%; the extractant in the kettle part of the separation column has a purity of 99.0%, and the loss rate of the extractant is 2.02%.

(64) When compared with the [Example 1], the separation energy consumption for purifying 1,2-butylene oxide per ton in the Comparative Example 1 is increased by 4.5%.

Comparative Example 2

(65) According to the process flow shown in FIG. 2, the operating conditions of the separation column comprise: the temperature of vapor phase at the column top is 103° C., and the pressure is 0.22 MPaG, the number of theoretical plates in separation column is 50; the extractant is N-octane, and a ratio of the extractant and 1,2-butylene oxide is 6:1 in a feed stream containing 1,2-butylene oxide and extractant based on the percentage by weight; the separation column reboiler A is a forced circulation type reboiler.

(66) The 1,2-butylene oxide stream at the top of the separation column has a purity of 99.95%, the recovery rate is 98.50%; the extractant in the kettle part of the separation column has a purity of 99.0%, and the loss rate of the extractant is 2.20%.

Comparative Example 3

(67) According to the process flow shown in FIG. 2, the operating conditions of the separation column comprise: the temperature of vapor phase at the column top is 103° C., and the pressure is 0.22 MPaG, the number of theoretical plates in separation column is 45; the extractant is N-octane, and a ratio of the extractant and 1,2-butylene oxide is 4:1 in a feed stream containing 1,2-butylene oxide and extractant based on the percentage by weight; the separation column reboiler A is a forced circulation type reboiler.

(68) The 1,2-butylene oxide stream at the top of the separation column has a purity of 99.95%, the recovery rate is 98.88%; the extractant in the kettle part of the separation column has a purity of 99.0%, and the loss rate of the extractant is 2.45%.

Comparative Example 4

(69) According to the process flow shown in FIG. 2, the operating conditions of the separation column comprise: the temperature of vapor phase at the column top is 103° C., and the pressure is 0.22 MPaG, the number of theoretical plates in separation column is 40; the extractant is N-octane, and a ratio of the extractant and 1,2-butylene oxide is 3:1 in a feed stream containing 1,2-butylene oxide and extractant based on the percentage by weight; the separation column reboiler A is a forced circulation type reboiler.

(70) The 1,2-butylene oxide stream at the top of the separation column has a purity of 99.95%, the recovery rate is 97.13%; the extractant in the kettle part of the separation column has a purity of 99.0%, and the loss rate of the extractant is 2.62%.

Comparative Example 5

(71) According to the process flow shown in FIG. 2, the operating conditions of the separation column comprise: the temperature of vapor phase at the column top is 103° C., and the pressure is 0.22 MPaG, the number of theoretical plates in separation column is 35; sending the heavy component impurity stream-effluent stream to be washed with water and then recycling the stream back so as to reduce the loss of the extractant; the extractant is N-octane, and a ratio of the extractant and 1,2-butylene oxide is 6:1 in a feed stream containing 1,2-butylene oxide and extractant based on the percentage by weight; the separation column reboiler A is a forced circulation type reboiler.

(72) The 1,2-butylene oxide stream at the top of the separation column has a purity of 99.95%, the recovery rate is 97.58%; the extractant in the kettle part of the separation column has a purity of 99.00%, and the loss rate of the extractant is 1.72%.

(73) When compared with the [Example 1], the separation energy consumption for purifying 1,2-butylene oxide per ton in the Comparative Example 5 is increased by 6.8%.