WO2013146609A1 - アセトニトリルの精製方法 - Google Patents
アセトニトリルの精製方法 Download PDFInfo
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- WO2013146609A1 WO2013146609A1 PCT/JP2013/058368 JP2013058368W WO2013146609A1 WO 2013146609 A1 WO2013146609 A1 WO 2013146609A1 JP 2013058368 W JP2013058368 W JP 2013058368W WO 2013146609 A1 WO2013146609 A1 WO 2013146609A1
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- acetonitrile
- reboiler
- column
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- distillation column
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D3/00—Distillation or related exchange processes in which liquids are contacted with gaseous media, e.g. stripping
- B01D3/007—Energy recuperation; Heat pumps
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- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C253/00—Preparation of carboxylic acid nitriles
- C07C253/32—Separation; Purification; Stabilisation; Use of additives
- C07C253/34—Separation; Purification
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D3/00—Distillation or related exchange processes in which liquids are contacted with gaseous media, e.g. stripping
- B01D3/14—Fractional distillation or use of a fractionation or rectification column
- B01D3/143—Fractional distillation or use of a fractionation or rectification column by two or more of a fractionation, separation or rectification step
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D3/00—Distillation or related exchange processes in which liquids are contacted with gaseous media, e.g. stripping
- B01D3/42—Regulation; Control
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07B—GENERAL METHODS OF ORGANIC CHEMISTRY; APPARATUS THEREFOR
- C07B63/00—Purification; Separation; Stabilisation; Use of additives
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C255/00—Carboxylic acid nitriles
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C255/00—Carboxylic acid nitriles
- C07C255/01—Carboxylic acid nitriles having cyano groups bound to acyclic carbon atoms
- C07C255/02—Carboxylic acid nitriles having cyano groups bound to acyclic carbon atoms of an acyclic and saturated carbon skeleton
- C07C255/03—Mononitriles
Definitions
- the present invention relates to a method for purifying acetonitrile.
- acetonitrile mainly recovers and purifies crude acetonitrile obtained as a by-product when producing acrylonitrile or methacrylonitrile by catalytic ammoxidation reaction of propylene or isobutene with ammonia and oxygen. It is a thing.
- Acetonitrile is used as a solvent for chemical reaction, particularly as a solvent for synthesis and purification of pharmaceutical intermediates, a moving bed solvent for high performance liquid chromatography, and the like.
- Recently, it has also been used as a solvent for synthesizing and purifying DNA, a solvent for synthesizing organic EL materials, a cleaning solvent for electronic parts, etc., and in such applications, it is required to be purified to a particularly high purity.
- Crude acetonitrile obtained as a by-product when producing acrylonitrile or methacrylonitrile includes allyl alcohol, oxazole, water, acetone, hydrocyanic acid, acrylonitrile, methacrylonitrile, propionitrile, cis- and trans-crotononitrile, Impurities such as acrylic acid, methyl acrylate, methacrylic acid, methyl methacrylate, acetic acid, acrolein, methacrolein, acetone, ammonia, impurities that cannot be analyzed, and the like are included.
- Patent Document 1 discloses a method for dehydrating acetonitrile, in which a sufficient amount of alkali is added to water-containing acetonitrile and mixed, and then the separated aqueous phase is removed.
- Patent Document 2 describes a method for increasing the production of acetonitrile, and discloses a method of coexisting acetone or ethyl alcohol or both in a reaction system when producing unsaturated nitrile and acetonitrile by ammoxidation. Yes.
- an object of the present invention is to provide a method for purifying high-purity acetonitrile by a process with low energy consumption.
- the present inventors have refined crude acetonitrile recovered in the step of producing acrylonitrile or methacrylonitrile by an ammoxidation method using two or more distillation columns.
- the top stream of the second distillation column can be used as a heat source for the reboiler of the first distillation column.
- purification can be provided by utilizing this heat source, and completed this invention.
- the present invention is as follows. [1] After reacting by adding alkali to water-containing acetonitrile produced by the ammoxidation reaction, the reaction mixture was supplied to the first distillation column, and the distillate obtained was further mixed with alkali to prepare an acetonitrile phase.
- a method for purifying acetonitrile comprising the step of removing the aqueous phase and supplying the acetonitrile phase to a second distillation column after separation into a water phase and a water phase, A method for purifying acetonitrile, wherein distillate vapor from the second distillation column is used as a heat source for the reboiler of the first distillation column.
- FIG. 1 shows a schematic view of an apparatus for supplying at least a part of steam distilled from the top of a product column as a heat source to a reboiler of a high-boiling separation column.
- 1 is a schematic view of an apparatus for supplying at least a part of steam distilled from the top of a low-boiling separation tower to a reboiler of a high-boiling separation tower as a heat source.
- FIG. 2 shows a schematic view of an apparatus for supplying at least a part of the bottom liquid of the low boiling separation tower as a heat source to the reboiler of the high boiling separation tower.
- the present embodiment a mode for carrying out the present invention (hereinafter simply referred to as “the present embodiment”) will be described in detail.
- the following embodiments are examples for explaining the present invention, and are not intended to limit the present invention to the following contents.
- the present invention can be implemented with appropriate modifications within the scope of the gist thereof.
- the same elements are denoted by the same reference numerals, and redundant description is omitted.
- the positional relationship such as up, down, left and right is based on the positional relationship shown in the drawings unless otherwise specified.
- the dimensional ratios of the devices and members are not limited to the illustrated ratios.
- the method for purifying acetonitrile in the present embodiment is as follows: After reacting by adding alkali to water-containing acetonitrile produced by the ammoxidation reaction, the reaction mixture was supplied to the first distillation column, and the distillate obtained was further mixed with alkali to prepare an acetonitrile phase.
- a method for purifying acetonitrile comprising the step of removing the aqueous phase and supplying the acetonitrile phase to a second distillation column after separation into a water phase and a water phase, It is a purification method of acetonitrile using the distillate vapor from the second distillation column as a heat source for the reboiler of the first distillation column.
- the method for purifying acetonitrile in the present embodiment can be performed using, for example, the following acetonitrile purifier.
- a reaction tank, a first distillation tower, a dehydration tower, and a second distillation tower are provided in this order, After acetonitrile and water containing water react in the reaction vessel, the reaction mixture is flowed into the first distillation column, the distillate from the first distillation column is flowed into the dehydration column, The resulting acetonitrile phase is made to flow into the second distillation column, A purification apparatus for acetonitrile in which the distillate vapor of the second distillation column is used as a heat source for the reboiler of the first distillation column.
- FIG. 1 shows an example of a schematic diagram of an apparatus for purifying acetonitrile in the present embodiment.
- the apparatus shown in FIG. 1 has a concentration tower 1 into which crude acetonitrile is introduced, and a high-boiling separation tower 3, a dehydration tower 4, a low-boiling separation tower 5, and a product tower 6 are connected to the concentration tower 1 via a reaction tank 2. They are connected in this order.
- Crude acetonitrile is obtained as a by-product when acrylonitrile or methacrylonitrile is produced from propylene, propane, isobutene and isobutane by a catalytic ammoxidation reaction.
- the product of the ammoxidation reaction is subjected to extractive distillation, and crude acetonitrile is recovered as a fraction separate from the fraction containing acrylonitrile or methacrylonitrile as a main component.
- crude acetonitrile refers to a fraction having the highest content of acetonitrile among fractions obtained by extractive distillation of a product of an ammoxidation reaction.
- Crude acetonitrile is generally separated from a distillation column that recovers most of the acrylonitrile, and is usually 5 to 40% by weight acetonitrile, 50 to 95% by weight water, hydrogen cyanide, allyl alcohol, oxazole, propio. It contains many kinds of impurities such as nitrile and ammonia.
- Crude acetonitrile is sent from line 7 to the middle stage of acetonitrile concentration tower 1.
- the acetonitrile concentration column 1 is an upright distillation column, and has a reboiler (not shown) at the bottom and a condenser (not shown) at the top. While removing hydrogen cyanide from the top of the column (line 8) and water from the bottom of the column (line 9), concentrated gaseous acetonitrile (hereinafter also referred to as “concentrated acetonitrile”) was extracted from the middle of the column (line 10). .
- the line 10 is provided with a side cut condenser (not shown). The side cut condenser condenses gaseous concentrated acetonitrile.
- the concentration of acetonitrile in the concentrated acetonitrile supplied from the concentrating tower 1 to the reaction tank 2 is usually 50 to 70% by mass, and additionally contains other impurities such as 25 to 70% by mass of water, hydrogen cyanide, and allyl alcohol.
- an alkaline aqueous solution for example, a sodium hydroxide aqueous solution or a potassium hydroxide aqueous solution is added from the line 11, and acrylonitrile or hydrogen cyanide contained as impurities in the concentrated acetonitrile is changed to a polymer such as succinonitrile or dimer.
- the temperature of the reaction vessel 2 is preferably 20 to 80 ° C., more preferably 60 to 75 ° C. for 1 to 15 hours, still more preferably 60 to 75 ° C. for 3 to 10 Let react for hours.
- the high boiling separation tower 3 is preferably a vacuum distillation tower.
- Acetonitrile is recovered from the top of the high boiling separation tower 3 as an azeotropic composition mixture with water or a composition mixture close thereto, and liquefied with a condenser (not shown).
- a part of the condensate is refluxed to the high boiling separation tower 3 through a line (not shown), and the remainder is sent to the dehydration tower 4 through the line 14.
- Polymers such as succinonitrile and dimer, alkali, allyl alcohol, propionitrile, water and a small amount of acetonitrile produced in the reaction tank 2 are separated from the line 13 at the bottom of the column and sent to a wastewater treatment facility or the like.
- a reboiler (not shown) that provides heat necessary for distillation is installed at the bottom of the column and supplies heat necessary for distillation.
- the high-boiling separation column 3 it is important to supply the amount of heat necessary for distillation constantly and stably in order to stably separate and remove allyl alcohol and propionitrile. Allyl alcohol and propionitrile are particularly difficult to separate, and it is preferable to separate and remove as much as possible in the high boiling point separation tower 3.
- the pressure in the high boiling separation column 3 is from 80 to 80 in terms of absolute pressure from the viewpoint of separating high boiling substances such as allyl alcohol and propionitrile, and suppressing decomposition of succinonitrile, dimer and the like produced in the reaction tank 2. It is preferably 300 mmHg, more preferably 100 to 250 mmHg.
- the tower bottom temperature is preferably 45 to 65 ° C., more preferably 50 to 60 ° C.
- the tower top temperature is preferably 35 to 60 ° C., more The temperature is preferably 40 to 50 ° C.
- a sufficient amount of alkali is added from the line 15 to extract the water present therein, and mixed, and then the separated aqueous phase is added to the line. By removing from 16, the acetonitrile phase is obtained from line 17.
- the alkali it is preferable to use an aqueous solution or solid of sodium hydroxide and / or potassium hydroxide, and more preferably an aqueous solution thereof.
- the extraction temperature in the dehydration tower 4 is preferably 5 ° C. to 60 ° C., more preferably 10 ° C. to 35 ° C.
- the extraction temperature indicates the temperature in the dehydration tower 4, and more specifically, the internal liquid at the alkali feed position from the top liquid feed position of the high boiling separation tower 3 in the dehydration tower 4. Indicates temperature.
- the amount of alkali used varies depending on the water content in acetonitrile, but is usually in the range of 10 to 90% by weight, preferably 30 to 60% by weight, based on the water content in acetonitrile.
- the amount of moisture in acetonitrile is preferably 10% by mass or less, more preferably 3% by mass or less by a method of extracting moisture with an alkali.
- the low boiling point compound is first separated and removed from the top of the low boiling separation column 5 through the line 18, and the bottom liquid of the low boiling separation column 5 is sent to the product column 6 through the line 19. It is preferable to separate high-boiling compounds from the bottom of the column through line 20 and to obtain purified acetonitrile from line 21 at the top of the column.
- the reflux ratio and the amount of low-boiling compounds and high-boiling compounds extracted can be determined as appropriate so as to achieve a purification degree suitable for the purpose.
- the reflux ratio of the low-boiling separation column 5 and the product column 6 is preferably 1 to 50, more preferably 2 to 30.
- the reflux ratio is defined as a value obtained by dividing the mass refluxed to the distillation column by the mass discharged outside the distillation column. From the viewpoint of efficiently separating and removing impurities by distillation, it is preferable that the reflux ratio is stably maintained at a predetermined value during operation in purifying high-purity acetonitrile.
- the top pressures of the low-boiling separation column 5 and the product column 6 are set near normal pressure from the viewpoint of energy efficiency and impurity separation.
- the lower limit of the tower top pressure is preferably 0.090 MPa or more in absolute pressure, more preferably 0.095 MPa or more, still more preferably 0.100 MPa or more, and the upper limit is 0.180 MPa or less in absolute pressure. It is preferably 0.150 MPa or less, more preferably 0.130 MPa or less.
- the column bottom temperatures of the low boiling separation column 5 and the product column 6 are preferably 80 to 95 ° C., more preferably 80 to 88 ° C., and the column top temperature is It is preferably 70 to 90 ° C, more preferably 70 to 85 ° C.
- FIG. 2 is a schematic view of an apparatus for supplying at least a part of the vapor distilled from the top of the product column 6 to the reboiler 3b of the high-boiling separation column 3 as a heat source.
- the reboiler 3b is a shell tube type, and the distillate vapor from the top of the product column 6 is supplied to the shell side, and the bottom liquid of the high boiling separation column 3 flowing through the tube side is used. Heat.
- the high boiling separation tower 3 is provided with a plurality of reboilers (3a and 3b).
- the distillate vapor of the product tower 6 is introduced into the reboiler 3b of the high boiling separation tower 3 dedicated to the steam, and the other reboiler 3a. It is preferable that another heat source is supplied. Heat exchange is performed with the bottom liquid of the high-boiling separation tower 3, and the steam drain discharged from the reboiler of the high-boiling separation tower 3 passes through a heat exchanger such as a condenser, if necessary, and is cooled with water or the like. , Refluxed and / or withdrawn to the product column 6.
- FIG. 3 shows a schematic view of an apparatus for supplying at least a part of the vapor distilled from the top of the low boiling separation tower 5 to the reboiler 3c of the high boiling separation tower 3 as a heat source.
- the apparatus shown in FIG. 3 is the same as the example shown in FIG. 2 except that the steam distilled from the low boiling separation tower 5 is supplied to the reboiler 3c of the high boiling separation tower 3, and therefore the difference is shown. Only the point will be described below.
- the top temperature of the low boiling separation tower 5 may be lower than the top temperature of the product tower 6. If it is higher than the tower bottom temperature, it can be used as a heat source.
- the top vapor of the low boiling separation column 5 contains a low boiling point component at a high concentration, it may be difficult to condense in the reboiler 3c as compared with that of the product column 6, so that the composition of the top flow is also It is a preferred embodiment to set the reboiler temperature in consideration.
- the preferred pressure and the top temperature of the low boiling separation column 5 and the product column 6 have been described above, they also affect the use of the distillate steam, and therefore there are preferred pressures and top temperatures from that viewpoint.
- the temperature of the distillate in order to use the distillate steam as a heat source, the temperature of the distillate must be higher than the temperature of the bottom liquid of the distillation column leading to the reboiler to be supplied. It is preferable to set the pressure of the distillation column in consideration of the column top temperature. Of course, it is also effective to adjust the pressure of the distillation column to which the reboiler is connected because the distilled steam can be used by lowering the temperature on the bottom liquid side of the distillation column.
- the low-boiling separation column 5 and / or the product column 6 is operated at or near atmospheric pressure, and the high-boiling separation column 3 is subjected to distillation under reduced pressure because the distillation steam temperature is the bottom liquid temperature of the high-boiling separation column 3. This is a preferred embodiment from the viewpoint of making it higher.
- U may be estimated by a chemical engineering method or using a reboiler performance value generally used in a chemical plant.
- ⁇ T is the temperature difference between the temperature of the distilled steam and the bottom liquid of the high boiling separation tower 3.
- ⁇ T results from the difference in operating conditions between the first distillation column and the second distillation column. Since this embodiment is intended to purify acetonitrile containing water produced by an ammoxidation reaction, the component ratio in the first distillation column and the second distillation column does not vary greatly. Therefore, the conditions of each distillation column are controlled to be substantially constant.
- the temperature of the first distillation column and the temperature of the second distillation column are preferably the bottom temperature of the first distillation column from the viewpoint of impurity separation and energy efficiency.
- the top temperature of the second distillation column is preferably 70 to 90 ° C, more preferably 70 to 85 ° C. Therefore, ⁇ T is preferably 10 to 35 ° C., more preferably 15 to 25 ° C. Accordingly, the heat transfer area A is inevitably determined within a specific range.
- the distillate from the second distillation column is used as a heat source for the reboiler of the first distillation column. As a result, stable operation becomes possible.
- the heat transfer area A becomes a specified value, but if the reboiler has a heat transfer area A that can cover the amount of heat q required for distillation when ⁇ T is in the range of 10 to 35 ° C., Stable operation is possible by using the distillate vapor from the second distillation column as a heat source for the reboiler of the first distillation column.
- the low boiling point separation column 5 and the product column 6 are apparatuses for accurately distilling liquids having acetonitrile concentrations of 95% by mass or more and 99% by mass or more, respectively.
- An adverse effect on the accuracy of the distillation is that, for example, disturbance of the low boiling separation column 5 and / or the product column 6 that provides the distillate vapor leads to disturbance of the high boiling separation column 3 that uses the distillate vapor.
- disturbance of the high-boiling separation tower 3 may lead to disturbance of the low-boiling separation tower 5 and / or the product tower 6.
- the mechanism by which the “turbulence” of one distillation column is transmitted to the other distillation column will be explained in detail.
- the temperature and / or pressure of the low boiling separation column 5 and / or the product column 6 may be reduced from the target value during steady operation.
- the amount of steam distilled from the distillation column fluctuates.
- the amount of steam supplied as a heat source to the reboiler of the high boiling separation tower 3 fluctuates, so that fluctuation in the amount of heat supplied to the high boiling separation tower 3 is caused in a chain.
- the distillation operation becomes unstable due to the occurrence of fluctuations in the reflux ratio in the high boiling separation column 3, and the accuracy of distillation is adversely affected. If the distillation in the high boiling separation column 3 becomes unstable, allyl alcohol and propionitrile are not sufficiently separated and removed, which has a fatal effect on the quality of high purity acetonitrile. Conversely, when the temperature and / or pressure of the high boiling separation column 3 is disturbed, the amount of distillate vapor condensed on the reboiler shell side of the high boiling separation column 3 varies. The distillate vapor is condensed by the reboiler and then introduced into the condenser of the low boiling separation column 5 and / or the product column 6 to be refluxed.
- the low-boiling separation column 5 and the product column 6 are distillation columns for precision distillation of acetonitrile, and adversely affect the separation of impurities in high-purity acetonitrile such as oxazole, hydrogen cyanide, water, ammonia, and other trace impurities due to distillation disturbance. Occurs.
- the reboiler of the product column 6 includes other distillations. It is preferable to stabilize the amount of heat supplied by passing steam at a constant flow rate from utility supply equipment which is equipment that exclusively generates and supplies steam without using distillate steam or the like in a tower.
- the pressure of the vapor supplied from the utility supply facility is preferably 1.0 MPaG or less, more preferably 0.6 MPaG or less, from the viewpoint of making the temperature difference from the liquid to be heated appropriate.
- the present inventors have improved the precision of distillation purification by adjusting the relationship between the top pressure of the distillation column supplying distilled steam and the pressure of the high-boiling separation tower reboiler through the distilled steam to a specific range. It was found that it can be maintained well.
- the amount of steam distilled from the second distillation column (low boiling separation column 5 and product column 6) supplied to the reboiler 3b of the first distillation column (high boiling separation column 3) is the reboiler of the first distillation column. It is preferably determined based on the pressure (distilled steam side, gauge pressure) and the top pressure (gauge pressure) of the second distillation column. In general, the gauge pressure indicates a relative value of the pressure with the atmospheric pressure set to 0. Therefore, when all of the distilled steam is condensed in the reboiler shell, the gauge pressure of the reboiler shell becomes zero. Depending on the fluid temperature on the reboiler tube side (distillation tower bottom liquid temperature), it can be negative.
- the pressure (gauge pressure) measured by the pressure gauge attached to the reboiler shell side of the first distillation column is the top pressure (gauge pressure) of the second distillation column.
- the branch valve 6v is adjusted so that it is preferably 0.90 times or less, more preferably 0.50 times or less, and still more preferably 0.20 times or less.
- the lower limit value is not particularly limited, but assuming a case where all of the distilled steam is condensed, a practical value is -0.1 times or more or 0 times or more.
- the tower top pressure (gauge pressure) of the product tower 6 is denoted as A
- the shell pressure (gauge pressure) of the reboiler 3b is denoted as B
- the pressure ratio B / A was evaluated.
- ⁇ A decrease in the magnification means an increase in the pressure difference.
- the pressure difference increases, the flow of steam from the top of the second distillation column to the reboiler of the first distillation column tends to stabilize.
- the steam flow is stabilized, the supply of heat is stabilized, and the amount of evaporation in the reboiler of the first distillation column is stabilized. This stabilizes the amount of steam rising in the first distillation column.
- the gas-liquid contact is repeated with the tray in the tower, and the vapor emitted from the top of the tower is condensed by the condenser, and a part of it is refluxed to the tower.
- the stability of gas-liquid contact in the distillation column appears in the pressure and temperature in the column, and can be understood by looking at the fluctuations in pressure.
- the fluctuation in the pressure value of the first distillation column is within ⁇ 7% of the median value.
- it is preferably controlled within ⁇ 5%, more preferably within ⁇ 3%.
- the pressure fluctuation is controlled within ⁇ 5%, heat exchange between the steam rising up the tray and the liquid going down the tray in the first distillation column is appropriately performed.
- impurities such as allyl alcohol and propionitrile to be separated in the first distillation column are concentrated on the bottom of the column by gas-liquid contact, and the amount distilled from the top of the column is significantly reduced.
- the shell pressure of the reboiler 3b of the high boiling separation tower 3 depends on the steam condensing performance in the shell, and the shell pressure tends to decrease as the heat transfer area of the reboiler 3b increases.
- the heat transfer area of the reboiler 3b of the high boiling separation tower 3 is preferably calculated by the above-described calculation and a new facility is preferably installed, but an idle facility may be diverted.
- the reboiler 3b Since the reboiler 3b stably condenses the distillate and returns it to the condenser of the product tower 6 at a constant gas / liquid ratio contributes to the stabilization of the entire system, the reboiler 3b stably condenses the distillate. It is preferable to adopt the reboiler 3b pressure as an operation index to be operated.
- the reboiler pressure is lower than the top pressure of the product column 6 for supplying the distillate vapor from the viewpoint of fluid flow, and the pressure value needs to be stable from the viewpoint of stable operation. Suitable for doing.
- the pressure (gauge pressure) measured by a pressure gauge attached to the shell side of the reboiler 3 c of the high boiling separation tower 3 is the top pressure (gauge pressure) of the low boiling separation tower 5.
- the branch valve 5v is adjusted so that it is preferably 0.90 times or less, more preferably 0.50 times or less, and still more preferably 0.20 times or less.
- the steam drain generated by the reboiler 3b is stored in a steam drain drum (not shown) installed as necessary, and sent to a condenser of the product tower 6 by a pump (not shown). It is preferable to provide a vent line in the vapor phase part of the steam drain drum as necessary to return the uncondensed gas to the condenser of the product column 6.
- the steam drain, uncondensed gas, and distilled steam flowing from the product tower 6 via the branch valve 6v flow into the condenser of the product tower 6.
- a refrigerant for the condenser of the product tower 6 water of 35 ° C. or lower is used, and the fluid is condensed and cooled.
- the condensate flows down to the reflux drum, a part is returned to the product tower 6 as reflux, and the other is extracted as a product through the line 21.
- a vent line 21a is installed in the reflux drum to extract uncondensed gas.
- the uncondensed gas is preferably guided to a scrubber, absorbed with water or the like, and then released to the atmosphere.
- the steam drain generated by the reboiler 3c is stored in a steam drain drum (not shown) installed as necessary, and sent to the condenser of the low boiling point separation tower 5 by a pump (not shown). It is preferable to provide a vent line in the vapor phase part of the steam drain drum as necessary so as to return the uncondensed gas to the condenser of the low boiling separation column 5.
- the steam drain, uncondensed gas, and distillate steam flowing from the low boiling point separation tower 5 via the branch valve 5v flow into the condenser of the low boiling point separation tower 5.
- a refrigerant of the condenser of the low boiling separation tower 5 water of 35 ° C. or less is used, and the fluid is condensed and cooled.
- the condensate flows down to the reflux drum, a part of the condensate is returned to the low boiling separator 5 as reflux, and the other is withdrawn as a low boiling point compound through the line 18.
- the reflux drum is provided with a vent line 18a for extracting uncondensed gas.
- the uncondensed gas is preferably guided to a scrubber, absorbed with water or the like, and then released to the atmosphere.
- the amount of reboiler steam used in the high boiling separation tower 3 can be reduced, and the low boiling separation tower 5 and / or energy efficiency associated with the reduction of the amount of condenser cooling water used in the product tower 6 can be achieved, and the condenser of the low boiling separation tower 5 and / or the product tower 6 can be reduced in size.
- the steam distilled from the low boiling separation column 5 and / or the product column 6 is passed through a dedicated reboiler and then refluxed and extracted.
- each column can independently and stably supply heat to the high boiling separation column 3, and can be refluxed to the low boiling separation column 5 and / or the product column 6 without contamination. Moreover, the reflux amount can be stabilized, and it is difficult to lead to disturbance of the entire purification process of acetonitrile.
- Each distillation column is preferably a plate column or a packed column each having a condenser at the top and a reboiler at the bottom.
- the plate tower include a cross flow contact type having a downcomer and a countercurrent contact type having no downcomer.
- a bubble bell type, a perforated plate type, a valve type, or the like can be used as the opening of the tray.
- the number of stages of the distillation column is not particularly limited as long as it is 10 or more, but is preferably 30 to 80.
- a column packed with an irregular packing and / or a regular packing can be used as the packing.
- the irregular filling for example, Raschig ring, Lessing ring, Pole ring, Berle saddle, Interlock saddle, Terrarette packing, Dixon ring or McMahon packing can be used.
- regular packing for example, a mesh-structured packing can be used.
- materials for these irregular and regular packing materials those made of magnetism, metal, plastic or carbon can be used.
- the packed tower can be provided with a liquid redistribution plate at an appropriate height to improve the gas-liquid contact efficiency.
- the total of 32% by mass of water, 1.6% by mass of hydrogen cyanide, acrylonitrile, allyl alcohol, oxazole, propionitrile, and the like was 1.4% by mass.
- the obtained liquid was supplied to the reaction tank 2 through the line 10.
- 48 mass% sodium hydroxide aqueous solution was added to the reaction tank 2 from the line 11, and it was made to react at 73 degreeC for 8 hours.
- the liquid 2810 kg / h in the reaction tank 2 was sent to the high boiling separation tower 3 through the line 12. Distillation was performed by flowing 0.4 MPaG of steam 2.8 t / h through a reboiler installed at the bottom of the tower.
- the tower top pressure and tower bottom pressure were 235 mmHg and 255 mmHg in absolute pressure, respectively, and the tower top temperature and tower bottom temperature were 41.5 ° C. and 58.9 ° C., respectively.
- the pressure fluctuation of the high-boiling separation column was ⁇ 1% of the numerical value as a median value.
- a liquid 770 kg / h containing allyl alcohol, propionitrile, sodium hydroxide, water and the like was extracted from the bottom of the column and treated with waste water. Vapor distilled from the top of the column was condensed with a condenser.
- the condensate 3940 kg / h was refluxed to the high boiling separation tower 3, and 2040 kg / h was supplied to the lower part of the dehydration tower 4 from the line 14.
- a 48% by mass aqueous sodium hydroxide solution 300 kg / h was supplied from the line 15 at the top of the dehydration tower 4 and brought into liquid-liquid contact with the hydrous crude acetonitrile supplied from the line 14.
- the aqueous phase was extracted from line 16.
- An acetonitrile phase of 1850 kg / h was extracted from the line 17 and supplied to the low boiling point separation tower 5.
- the reboiler of the low boiling separation column 5 was subjected to distillation by flowing a steam of 0.4 MPaG at 2.6 t / h.
- the tower top pressure and tower bottom pressure were 0.1172 MPa and 0.1181 MPa in absolute pressure, respectively, and the tower top temperature and tower bottom temperature were 78.8 ° C. and 86.4 ° C., respectively.
- the pressure fluctuation of the low-boiling separation column was ⁇ 1% of the numerical value as a median value.
- Vapor distilled from the top of the column was condensed with a condenser. Water at 28 ° C. was used as the condenser refrigerant. 4150 kg / h of the condensate was refluxed to the low boiling separation column 5, 300 kg / h was withdrawn from the line 18, and oxazole and low boiling point substances were removed. The liquid in the line 18 was treated with waste water.
- a liquid of 1550 kg / h extracted from the line 19 was sent to the product tower 6. Distillation was performed by flowing 1.6 t / h of 0.4 MPaG of steam through the reboiler of the product tower 6.
- the tower top pressure and the tower bottom pressure were respectively 0.1100 MPa and 0.1112 MPa in absolute pressure, and the tower top temperature and the tower bottom temperature were 81.2 ° C. and 82.2 ° C., respectively.
- the pressure fluctuation of the product tower was ⁇ 1% of the above numerical value as a median value.
- a 70 kg / h liquid containing propionitrile and a high boiling point substance was extracted from the line 20 and treated with waste water.
- Example 1 As shown in FIG. 2, one reboiler 3 b was added to the high-boiling separation tower 3 and was used as a heat source through the distillate vapor of the product tower 6. Further, a steam drain drum (not shown) for storing the steam drain generated by the reboiler 3b and a pump (not shown) for sending the steam drain in the drum to the condenser of the product tower 6 were installed. Except for these, acetonitrile was purified using the same equipment as in Comparative Example 1. Initially, the condenser valve 6v of the product tower 6 was fully opened. Over a week, the valve 6v was gradually closed to increase the amount of heat supplied to the reboiler 3b of the high boiling point separation tower 3.
- the vapor of the reboiler 3a of the high boiling separation tower 3 was reduced.
- the valve 6v was fully closed.
- the top pressure of the product tower 6 (denoted as gauge pressure “A”) is 0.0100 MPaG
- the shell pressure of the reboiler 3 b (denoted as gauge pressure “B”) is 0.0002 MPaG.
- Each variation was ⁇ 1%.
- the distillate vapor of the product column 6 was 81.2 ° C.
- the bottom liquid of the high boiling separation column 3 was 58.9 ° C.
- the median value of the pressure ratio B / A was 0.020, and the variation was ⁇ 3%.
- Example 2 Acetonitrile was purified by the same equipment as in Example 1 except that the distillate vapor of the low boiling separation column 5 was further used as a heat source for the reboiler 3c of the high boiling separation column 3 in addition to the distillate vapor of the product column 6. .
- the flow of the distillate vapor in the low boiling separation column 5 was as shown in FIG. Initially, the condenser valve 5v of the low boiling separator 5 was fully opened. While the valve 5v was fully open, there was no process disturbance, and there was no problem with the quality of the obtained acetonitrile. Over a week, the valve 5v was gradually closed and finally 10% closed (90% open state).
- the column top pressure (referred to as gauge pressure “A”) of the low boiling separation column 5 was 0.0172 MPaG, and the column top temperature and the column bottom temperature were 78.8 ° C. and 86.4 ° C., respectively.
- the shell pressure (referred to as gauge pressure “B”) of the reboiler 3c of the high boiling separation tower 3 was 0.0032 MPaG, and the tower top temperature and tower bottom temperature were 41.5 ° C. and 58.9 ° C., respectively.
- the median value of the pressure ratio B / A was 0.19.
- the fluctuation of the pressure at the top of the high boiling separation tower was ⁇ 1%.
- the top pressure of the product tower 6 (denoted as gauge pressure “A ′”) is 0.0100 MPaG, and the shell pressure of the reboiler 3 b (denoted as gauge pressure “B ′”) is 0.0002 MPaG. 'Each variation was ⁇ 1%.
- Table 5 shows the amount of reboiler steam and condenser cooling water used.
- Comparative Example 2 As shown in FIG. 4, acetonitrile was used in the same equipment as in Comparative Example 1 except that one reboiler 3 c was added to the high boiling separation tower 3 and the bottom liquid of the low boiling separation tower 5 was used as a heat source. Purified. Initially, the bypass valve 51v of the reboiler 3c with the high boiling separation tower was fully opened. The bypass valve 51v was gradually closed to increase the amount of heat supplied to the reboiler 3b of the high boiling point separation tower 3. Eventually, the valve 51v was fully closed. During this time, the temperature and pressure fluctuations of the high-boiling separation column 3 and the low-boiling separation column 5 were ⁇ 1%.
- Example 3 Acetonitrile was purified by the same equipment and method as in Example 2 except that the valve 5v was finally closed 50%.
- the tower top pressure (gauge pressure) of the low boiling separation tower 5 was 0.0172 MPaG
- the tower top temperature and the tower bottom temperature were 78.8 ° C. and 86.4 ° C., respectively.
- the shell pressure (gauge pressure) of the reboiler 3c of the high boiling separation tower 3 was 0.0168 MPaG
- the tower top temperature and tower bottom temperature were 41.5 ° C. and 58.9 ° C., respectively.
- Table 9 shows the amount of reboiler steam and condenser cooling water used.
- the pressure in the low-boiling separation column 5 and the high-boiling separation column 3 was maintained at ⁇ 10% for a while from the start of purification, but after about one day, the shell pressure (gauge pressure) of the reboiler 3c in the high-boiling separation column 3 was Hunting between 0.0071 MPaG and 0.0170 MPaG. Along with this, hunting was started in the high-boiling separation column 3 and the low-boiling separation column 5 within a range of about ⁇ 20%. When impurities of acetonitrile purified after the start of hunting were analyzed, the results shown in Table 11 were obtained.
- Example 12 The valve 5v was gradually closed from the state of Example 2.
- Table 12 shows the degree of closing of the valve 5v (closed state), the top pressure of the low boiling separation tower 5, and the shell pressure of the high boiling separation reboiler 3b.
- Table 12 also shows the impurity concentration of the valve 5v.
- the amounts of reboiler steam and condenser cooling water used are as shown in Table 13.
- Example 10 A liquid containing 12% by mass of acetonitrile, which is a byproduct of the propane ammoxidation reaction, was supplied to the same equipment as in Example 2 to purify acetonitrile.
- a liquid containing 12% by mass of acetonitrile was supplied from the line 7 to the acetonitrile concentration tower 1.
- Hydrogen cyanide was separated from line 8 and a part of water was separated from line 9.
- Vapor was extracted from the line 10 and condensed with a condenser (not shown) installed in the line 10 to obtain a liquid containing 64% by mass of acetonitrile.
- the total of 33% by mass of water, 1.7% by mass of hydrogen cyanide, acrylonitrile, allyl alcohol, propionitrile and the like was 1.3% by mass.
- the liquid obtained above was supplied to the reaction tank 2 through the line 10.
- 48 mass% sodium hydroxide aqueous solution was added to the reaction tank 2 from the line 11, and it was made to react at 73 degreeC for 8 hours.
- the liquid 2810 kg / h in the reaction tank 2 was sent to the high boiling separation tower 3 through the line 12. Distillation was performed by flowing 0.4 MPaG of steam 2.8 t / h through a reboiler installed at the bottom of the tower.
- the tower top pressure and tower bottom pressure were 235 mmHg and 255 mmHg in absolute pressure, respectively, and the tower top temperature and tower bottom temperature were 41.5 ° C. and 58.9 ° C., respectively.
- the pressure fluctuation of the high-boiling separation column was ⁇ 1% of the numerical value as a median value.
- a liquid 770 kg / h containing allyl alcohol, propionitrile, sodium hydroxide, water and the like was extracted from the bottom of the column and treated with waste water. Vapor distilled from the top of the column was condensed with a condenser.
- the condensate 3940 kg / h was refluxed to the high boiling separation tower 3, and 2040 kg / h was supplied to the lower part of the dehydration tower 4 from the line 14.
- a 48% by mass aqueous sodium hydroxide solution 300 kg / h was supplied from the line 15 at the top of the dehydration tower 4 and brought into liquid-liquid contact with the hydrous crude acetonitrile supplied from the line 14.
- the aqueous phase was extracted from line 16.
- An acetonitrile phase of 1850 kg / h was extracted from the line 17 and supplied to the low boiling point separation tower 5.
- the reboiler of the low boiling separation column 5 was subjected to distillation by flowing a steam of 0.4 MPaG at 2.6 t / h.
- the tower top pressure and tower bottom pressure were 0.1172 MPa and 0.1181 MPa in absolute pressure, respectively, and the tower top temperature and tower bottom temperature were 78.8 ° C. and 86.4 ° C., respectively.
- the pressure fluctuation of the low-boiling separation column was ⁇ 1% of the numerical value as a median value. Vapor distilled from the top of the column was condensed with a condenser. Water at 28 ° C. was used as the condenser refrigerant. 4150 kg / h of the condensate was refluxed to the low-boiling separation tower 5, 300 kg / h was extracted from the line 18, and low-boiling substances were removed. The liquid in the line 18 was treated with waste water.
- a liquid of 1550 kg / h extracted from the line 19 was sent to the product tower 6. Distillation was performed by flowing 1.6 t / h of 0.4 MPaG of steam through the reboiler of the product tower 6.
- the tower top pressure and the tower bottom pressure were respectively 0.1100 MPa and 0.1112 MPa in absolute pressure, and the tower top temperature and the tower bottom temperature were 81.2 ° C. and 82.2 ° C., respectively.
- the pressure fluctuation of the product tower was ⁇ 1% of the above numerical value as a median value.
- a 70 kg / h liquid containing propionitrile and a high boiling point substance was extracted from the line 20 and treated with waste water.
- Reboilers 3b and 3c as shown in FIGS. 2 and 3 were added to the high boiling separation column 3 in the above process.
- the valve 6v was gradually closed to increase the amount of heat supplied to the reboiler 3b of the high boiling point separation tower 3.
- the valve 6v was fully closed.
- the top pressure of the product column 6 (referred to as gauge pressure “A”) is 0.0100 MPaG
- the shell pressure of the reboiler 3 b (referred to as gauge pressure “B”) is 0.0020 MPaG
- the pressure ratio B / A was 0.020.
- the fluctuation of the pressure at the top of the high boiling separation tower was ⁇ 0%.
- the valve 5v was gradually closed and finally 35% closed.
- the top pressure of the low boiling separation tower 5 (denoted as gauge pressure “A ′”) is 0.0172 MPaG
- the shell pressure of the reboiler 3 c of the high boiling separation tower 3 (denoted as gauge pressure “B ′”) is It was 0.0108 MPaG
- the median value of the pressure ratio B ′ / A ′ was 0.63
- the fluctuation of the pressure at the top of the high boiling separation tower was ⁇ 1%.
- the distillate vapor from the product column 6 and / or the low-boiling separation column 5 is used as a heat source for the reboiler of the high-boiling point separation column 3. This shows that the energy consumption during the process can be significantly reduced.
- the present invention is a process in which the amount of energy used for refining is small and the refining equipment and processes are simple. Therefore, it can be used for applications such as pharmaceutical intermediate synthesis and purification solvents, DNA synthesis and purification solvents, organic EL material synthesis solvents, and electronic component cleaning solvents while minimizing cost increases. Purity acetonitrile can be purified efficiently.
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Abstract
Description
アセトニトリルは、化学反応用の溶媒、特には医薬中間体の合成や精製における溶媒や、高速液体クロマトグラフィーの移動層溶媒などに用いられている。また、最近はDNA合成・精製溶媒、有機EL材料合成用溶媒、電子部品の洗浄溶剤などにも用いられるようになってきており、そうした用途の場合、特に高純度に精製されることが要求されてきている。
アクリロニトリル又はメタクリロニトリルを製造する際に副生成物として得られる粗アセトニトリルには、アリルアルコールやオキサゾール、水、アセトン、青酸、アクリロニトリル、メタクリロニトリル、プロピオニトリル、cis-及びtrans-クロトンニトリル、アクリル酸、アクリル酸メチル、メタクリル酸、メタクリル酸メチル、酢酸、アクロレイン、メタクロレイン、アセトン、アンモニア等の不純物や、分析不能な不純物等が含まれている。
特許文献1には、含水アセトニトリルに、その中に存在する水を抽出するのに十分な量のアルカリを加えて混合し、次いで分離した水性相を除去するアセトニトリルの脱水方法が開示されている。また、特許文献2には、アセトニトリルの増産に関して記載されており、アンモオキシデーションにより不飽和ニトリル及びアセトニトリルを製造する際に、反応系にアセトン又はエチルアルコール若しくはその両者を共存させる方法が開示されている。
上記事情に鑑み、本発明は、エネルギー消費量の少ないプロセスにより、高純度のアセトニトリルを精製する方法を提供することを目的とする。
[1]
アンモ酸化反応により生成した、水を含有するアセトニトリルにアルカリを加えて反応させた後、反応混合物を第一の蒸留塔に供給し、得られた留出液をさらにアルカリと混合したものをアセトニトリル相と水相とに分離した後、前記水相を除去し、前記アセトニトリル相を第二の蒸留塔に供給する工程を含むアセトニトリルの精製方法であって、
前記第二の蒸留塔からの留出蒸気を前記第一の蒸留塔のリボイラーの熱源とするアセトニトリルの精製方法。
[2]
前記留出蒸気の一部を前記リボイラーに供給し、残部を前記第二の蒸留塔に接続されたコンデンサーに供給する、上記[1]記載のアセトニトリルの精製方法。
[3]
前記第一の蒸留塔のリボイラー圧力(留出蒸気側、ゲージ圧)及び前記第二の蒸留塔の塔頂圧力(ゲージ圧)を基準として、前記リボイラーへの前記留出蒸気の供給量を決定する、上記[1]又は[2]記載のアセトニトリルの精製方法。
[4]
前記第一の蒸留塔のリボイラー圧力を、前記第二の蒸留塔の塔頂圧力の0.90倍以下にする、上記[3]記載のアセトニトリルの精製方法。
[5]
反応槽、第一の蒸留塔、脱水塔、及び第二の蒸留塔がこの順に設けられており、
水を含有するアセトニトリルとアルカリが前記反応槽で反応した後、反応混合物が第一の蒸留塔に流入され、前記第一の蒸留塔の留出液は前記脱水塔に流入され、前記脱水塔で得られるアセトニトリル相が第二の蒸留塔に流入されるようになっており、
前記第二の蒸留塔の留出蒸気が、前記第一の蒸留塔のリボイラーの熱源とされるアセトニトリルの精製装置。
[6]
前記留出蒸気の一部が前記リボイラーに供給され、残部は前記第二の蒸留塔に接続されたコンデンサーに供給される、上記[5]記載のアセトニトリルの精製装置。
[7]
前記第一の蒸留塔のリボイラー圧力(留出蒸気側、ゲージ圧)及び前記第二の蒸留塔の塔頂圧力(ゲージ圧)を基準として、前記リボイラーへの前記留出蒸気の供給量が決定される、上記[5]又は[6]記載のアセトニトリルの精製装置。
[8]
前記第一の蒸留塔のリボイラー圧力が、前記第二の蒸留塔の塔頂圧力の0.90倍以下である、上記[7]記載のアセトニトリルの精製装置。
アンモ酸化反応により生成した、水を含有するアセトニトリルにアルカリを加えて反応させた後、反応混合物を第一の蒸留塔に供給し、得られた留出液をさらにアルカリと混合したものをアセトニトリル相と水相とに分離した後、前記水相を除去し、前記アセトニトリル相を第二の蒸留塔に供給する工程を含むアセトニトリルの精製方法であって、
前記第二の蒸留塔からの留出蒸気を前記第一の蒸留塔のリボイラーの熱源とするアセトニトリルの精製方法である。
反応槽、第一の蒸留塔、脱水塔、及び第二の蒸留塔がこの順に設けられており、
水を含有するアセトニトリルとアルカリが前記反応槽で反応した後、反応混合物が第一の蒸留塔に流入され、前記第一の蒸留塔の留出液は前記脱水塔に流入され、前記脱水塔で得られるアセトニトリル相が第二の蒸留塔に流入されるようになっており、
前記第二の蒸留塔の留出蒸気が、前記第一の蒸留塔のリボイラーの熱源とされるアセトニトリルの精製装置。
図2は、製品塔6の塔頂から留出する蒸気の少なくとも一部を高沸分離塔3のリボイラー3bに熱源として供給する装置の概略図を示す。図2に示す例では、リボイラー3bはシェルチューブ型であって、製品塔6の塔頂からの留出蒸気はシェル側に供給され、チューブ側を流通する高沸分離塔3の塔底液を加熱する。高沸分離塔3には複数のリボイラー(3a及び3b)が設けられており、製品塔6の留出蒸気は、当該蒸気専用の高沸分離塔3のリボイラー3bに導入され、他方のリボイラー3aには別の熱源が供給されるのが好ましい。高沸分離塔3の塔底液と熱交換が行われ、高沸分離塔3のリボイラーから排出される蒸気ドレンは、必要に応じてコンデンサーなどの熱交換器を通過し、水等で冷却後、製品塔6に還流及び/又は抜き出される。
先ず、留出蒸気の流量と該蒸気が全凝縮した場合のエンタルピーから、該リボイラーを通じて高沸分離塔3に供給可能な熱量qを計算する。続いて、リボイラーの大きさを決めるため伝熱面積の計算を行う。熱量qは、総括伝熱係数U、伝熱面積A及び温度差ΔTの積、すなわちq=U・A・ΔTである。Uは、一般に化学プラントで使用されるリボイラーの実績値を用いても、化学工学的な手法で推定してもよい。本実施形態において、ΔTは、留出蒸気の温度と高沸分離塔3の塔底液の温度差である。ΔTは第一の蒸留塔と第二の蒸留塔の運転条件の差から生じる。本実施形態はアンモ酸化反応により生成した、水を含有するアセトニトリルの精製を目的とするものであるから、第一の蒸留塔及び第二の蒸留塔における成分比は大きく変動することはない。したがって、各蒸留塔の条件は概ね一定になるよう制御される。
アセトニトリル中の不純物濃度測定には、ガスクロマトグラフィーを用い、そのときの条件は以下のとおりであった。
ガスクロマトグラフィーは、ヒューレッドパッカード社製HP-6890を用い、カラムは、アジレントテクノロジーズ社製DB-624(長さ60m×内径0.32mm、膜厚5.0μm)を用いた。検出器としてはFIDを用い、キャリヤーガスにはヘリウムを用いた。
カラム温度条件は、以下のとおりであった。
初期温度: 70℃
初期時間: 10分
昇温速度: 5.0℃/分
中間温度: 120℃
ポストタイム: 10分
最終温度: 220℃
図1に示す精製装置を用いてアセトニトリルの精製を行った。
プロピレンのアンモキシデーション反応の副生物であるアセトニトリルを15質量%含有する液をライン7よりアセトニトリル濃縮塔1に供給した。ライン8よりシアン化水素、ライン9より水の一部を分離除去した。ライン10より蒸気を抜き出して、ライン10に設置されているコンデンサー(図示せず)で凝縮させ、アセトニトリルを65質量%含む液を得た。その他の組成としては、水32質量%、シアン化水素1.6質量%、アクリロニトリル、アリルアルコール、オキサゾール及びプロピオニトリル等の合計が1.4質量%であった。
得られた液を、ライン10を通じて反応槽2に供給した。反応槽2には、ライン11より48質量%水酸化ナトリウム水溶液を加え、73℃において8時間反応させた。
反応槽2の液2810kg/hを、ライン12を通じて、高沸分離塔3に送った。塔底に設置されているリボイラーに、0.4MPaGの蒸気2.8t/hを流し、蒸留を行った。塔頂圧及び塔底圧は、それぞれ絶対圧で235mmHg及び255mmHg、塔頂温度及び塔底温度は、それぞれ41.5℃及び58.9℃であった。高沸分離塔の圧力変動は、前記数値を中央値として、その±1%であった。塔底よりアリルアルコール、プロピオニトリル、水酸化ナトリウム及び水などを含有する液770kg/hを抜き出し、廃水処理した。塔頂から留出する蒸気をコンデンサーで凝縮させた。凝縮液3940kg/hを高沸分離塔3に還流し、2040kg/hをライン14から脱水塔4の下部に供給した。
脱水塔4の上部のライン15から48質量%水酸化ナトリウム水溶液300kg/hを供給し、ライン14から供給した含水粗アセトニトリルと液-液接触させた。ライン16から水相を抜き出した。ライン17からアセトニトリル相1850kg/hを抜き出し、低沸分離塔5に供給した。
低沸分離塔5のリボイラーに、0.4MPaGの蒸気2.6t/hを流し、蒸留を行った。塔頂圧及び塔底圧は、それぞれ絶対圧で0.1172MPa及び0.1181MPa、塔頂温度及び塔底温度は、それぞれ78.8℃及び86.4℃であった。低沸分離塔の圧力変動は、前記数値を中央値として、その±1%であった。塔頂から留出する蒸気をコンデンサーで凝縮させた。コンデンサーの冷媒としては、28℃の水を用いた。凝縮液4150kg/hを低沸分離塔5に還流し、300kg/hをライン18から抜き出し、オキサゾール及び低沸点物質を除去した。ライン18の液は、廃水処理した。ライン19から抜き出した1550kg/hの液を製品塔6に送った。
製品塔6のリボイラーに、0.4MPaGの蒸気1.6t/hを流し、蒸留を行った。塔頂圧及び塔底圧は、それぞれ絶対圧で0.1100MPa及び0.1112MPa、塔頂温度及び塔底温度は、それぞれ81.2℃及び82.2℃であった。製品塔の圧力変動は、前記数値を中央値として、その±1%であった。ライン20からプロピオニトリルや高沸点物質を含む液70kg/hを抜き出し、廃水処理した。塔頂から留出する蒸気をコンデンサーで凝縮させ、還流ドラムに流下させた。コンデンサーの冷媒としては、28℃の水を用いた。還流ドラム内の凝縮液4380kg/hを、ポンプを用いて製品塔6に還流し、1480kg/hをライン21から抜き出し、精製したアセトニトリルを得た。
精製アセトニトリル中の不純物を分析したところ、表1に示す結果を得た。
リボイラー蒸気及びコンデンサー冷却水の使用量は、表2のとおりであった。
図2に示すように、高沸分離塔3にリボイラー3bを1基追加し、製品塔6の留出蒸気を通じ、熱源として利用した。また、リボイラー3bで生成した蒸気ドレンを貯える蒸気ドレンドラム(図示せず)と、ドラム内の蒸気ドレンを製品塔6のコンデンサーに送液するポンプ(図示せず)を設置した。これら以外は、比較例1と同様の設備でアセトニトリルを精製した。
初期、製品塔6のコンデンサー行き弁6vを全開にしていた。1週間をかけ徐々に弁6vを閉止し、高沸分離塔3のリボイラー3bへの熱量供給を増加させていった。同時に、高沸分離塔3のリボイラー3aの蒸気を減少させていった。最終的には、弁6vを全閉にした。この時、製品塔6の塔頂圧(ゲージ圧「A」と記す。)は0.0100MPaG、リボイラー3bのシェル圧(ゲージ圧「B」と記す。)は0.0002MPaGであり、A、Bそれぞれの変動は±1%であった。製品塔6の留出蒸気は81.2℃であり、高沸分離塔3の塔底液は58.9℃であった。また、圧力比B/Aの中央値は0.020であり、その変動は±3%であった。弁6vの全閉期間中、プロセスの乱れはなく、また得られたアセトニトリルの品質にも問題はなかった。弁6vの全閉後は、製品塔6の留出蒸気は全て高沸分離塔3のリボイラー3bに流された後、リボイラー3bから排出されるドレンをドラム(図示せず)に流下させた。ドラム内の蒸気ドレンは、ポンプ(図示せず)で製品塔コンデンサーに流入させた。
精製したアセトニトリルの不純物を分析したところ、表3に示す結果を得た。
リボイラー蒸気及びコンデンサー冷却水の使用量は、表4のとおりであった。
製品塔6の留出蒸気に加えて低沸分離塔5の留出蒸気を高沸分離塔3のリボイラー3cの熱源として更に利用したこと以外は、実施例1と同様の設備でアセトニトリルを精製した。低沸分離塔5の留出蒸気の流れは、図3に示すとおりであった。
初期、低沸分離塔5のコンデンサー行き弁5vを全開にしていた。弁5vが全開の間、プロセスの乱れはなく、また得られたアセトニトリルの品質にも問題はなかった。1週間をかけ徐々に弁5vを閉じ、最終的には10%閉じた(90%開いている状態)。この時、低沸分離塔5の塔頂圧(ゲージ圧「A」と記す。)は0.0172MPaG、塔頂温度及び塔底温度は、それぞれ78.8℃及び86.4℃であった。高沸分離塔3のリボイラー3cのシェル圧(ゲージ圧「B」と記す。)は0.0032MPaGで、塔頂温度及び塔底温度は、それぞれ41.5℃及び58.9℃であった。また、圧力比B/Aの中央値は0.19であった。また、高沸分離塔塔頂の圧力の変動は±1%であった。
製品塔6の塔頂圧(ゲージ圧「A’」と記す。)は0.0100MPaG、リボイラー3bのシェル圧(ゲージ圧「B’」と記す。)は0.0002MPaGであり、A’、B’それぞれの変動は±1%であった。
精製したアセトニトリルの不純物を分析したところ、表5に示す結果を得た。
リボイラー蒸気及びコンデンサー冷却水の使用量は、表6のとおりであった。
図4に示すように、高沸分離塔3にリボイラー3cを1基追加し、低沸分離塔5の塔底液を通じ、熱源として利用したこと以外は、比較例1と同様の設備でアセトニトリルを精製した。
初期、高沸分離塔追加リボイラー3cのバイパス弁51vを全開にしていた。徐々に前記バイパス弁51vを閉じ、高沸分離塔3のリボイラー3bへの熱量供給を増加させていった。最終的には、弁51vを全閉にした。この間、高沸分離塔3及び低沸分離塔5それぞれの温度及び圧力の変動は、±1%であった。
精製したアセトニトリルの不純物を分析したところ、表7に示す結果を得た。
リボイラー蒸気及びコンデンサー冷却水の使用量は、表8のとおりで、それぞれの総使用量は、比較例1と差異がなかった。
弁5vを最終的に50%閉じたこと以外は、実施例2と同様の設備及び方法でアセトニトリルを精製した。初期、低沸分離塔5の塔頂圧(ゲージ圧)は0.0172MPaG、塔頂温度及び塔底温度はそれぞれ78.8℃及び86.4℃であった。高沸分離塔3のリボイラー3cのシェル圧(ゲージ圧)は0.0168MPaG、塔頂温度及び塔底温度はそれぞれ41.5℃及び58.9℃であった。
精製したアセトニトリルの不純物を分析したところ、表9に示す結果を得た。
リボイラー蒸気及びコンデンサー冷却水の使用量は、表10のとおりであった。
ハンチング開始後に精製されたアセトニトリルの不純物を分析したところ、表11に示す結果を得た。
実施例2の状態から弁5vを徐々に閉じていった。その際の弁5vの閉じている度合(閉止状況)と低沸分離塔5の塔頂圧及び高沸分離塔リボイラー3bのシェル圧を表12に示す。また、弁5vの不純物濃度についても、表12に示す。
リボイラー蒸気及びコンデンサー冷却水の使用量については、表13に示すとおりであった。
プロパンのアンモキシデーション反応の副生物であるアセトニトリルを12質量%含有する液を実施例2と同様の設備に供給し、アセトニトリルの精製を行った。
アセトニトリルを12質量%含有する液をライン7よりアセトニトリル濃縮塔1に供給した。ライン8よりシアン化水素、ライン9より水の一部を分離除去した。ライン10より蒸気を抜き出して、ライン10に設置されているコンデンサー(図示せず)で凝縮させ、アセトニトリルを64質量%含む液を得た。その他の組成としては、水33質量%、シアン化水素1.7質量%、アクリロニトリル、アリルアルコール及びプロピオニトリル等の合計が、1.3質量%であった。
前記で得た液を、ライン10を通じて反応槽2に供給した。反応槽2には、ライン11より48質量%水酸化ナトリウム水溶液を加え、73℃において8時間反応させた。
反応槽2の液2810kg/hを、ライン12を通じて、高沸分離塔3に送った。塔底に設置されているリボイラーに、0.4MPaGの蒸気2.8t/hを流し、蒸留を行った。塔頂圧及び塔底圧は、それぞれ絶対圧で235mmHg及び255mmHg、塔頂温度及び塔底温度は、それぞれ41.5℃及び58.9℃であった。高沸分離塔の圧力変動は、前記数値を中央値として、その±1%であった。塔底よりアリルアルコール、プロピオニトリル、水酸化ナトリウム及び水などを含有する液770kg/hを抜き出し、廃水処理した。塔頂から留出する蒸気をコンデンサーで凝縮させた。凝縮液3940kg/hを高沸分離塔3に還流し、2040kg/hをライン14から脱水塔4の下部に供給した。
脱水塔4の上部のライン15から48質量%水酸化ナトリウム水溶液300kg/hを供給し、ライン14から供給した含水粗アセトニトリルと液-液接触させた。ライン16から水相を抜き出した。ライン17からアセトニトリル相1850kg/hを抜き出し、低沸分離塔5に供給した。
低沸分離塔5のリボイラーに、0.4MPaGの蒸気2.6t/hを流し、蒸留を行った。塔頂圧及び塔底圧は、それぞれ絶対圧で0.1172MPa及び0.1181MPa、塔頂温度及び塔底温度は、それぞれ78.8℃及び86.4℃であった。低沸分離塔の圧力変動は、前記数値を中央値として、その±1%であった。塔頂から留出する蒸気をコンデンサーで凝縮させた。コンデンサーの冷媒としては、28℃の水を用いた。凝縮液4150kg/hを低沸分離塔5に還流し、300kg/hをライン18から抜き出し、低沸点物質を除去した。ライン18の液は、廃水処理した。ライン19から抜き出した1550kg/hの液を製品塔6に送った。
製品塔6のリボイラーに、0.4MPaGの蒸気1.6t/hを流し、蒸留を行った。塔頂圧及び塔底圧は、それぞれ絶対圧で0.1100MPa及び0.1112MPa、塔頂温度及び塔底温度は、それぞれ81.2℃及び82.2℃であった。製品塔の圧力変動は、前記数値を中央値として、その±1%であった。ライン20からプロピオニトリルや高沸点物質を含む液70kg/hを抜き出し、廃水処理した。塔頂から留出する蒸気をコンデンサーで凝縮させ、還流ドラムに流下させた。コンデンサーの冷媒としては、28℃の水を用いた。還流ドラム内の凝縮液4380kg/hを、ポンプを用いて製品塔6に還流し、1480kg/hをライン21から抜き出し、精製したアセトニトリルを得た。精製アセトニトリル中の不純物の分析結果を表14に示す。リボイラー蒸気及びコンデンサー冷却水の使用量は、比較例1と同等であった。
弁6vを徐々に閉じ、高沸分離塔3のリボイラー3bへの熱量供給を増加させていった。最終的には、弁6vを全閉した。この時、製品塔6の塔頂圧(ゲージ圧「A」と記す。)は0.0100MPaG、リボイラー3bのシェル圧(ゲージ圧「B」と記す。)は0.0020MPaGであり、圧力比B/Aは0.020であった。また、高沸分離塔塔頂の圧力の変動は±0%であった。
続いて、弁5vを徐々に閉じ、最終的には35%閉じた。この時、低沸分離塔5の塔頂圧(ゲージ圧「A’」と記す。)は0.0172MPaG、高沸分離塔3のリボイラー3cのシェル圧(ゲージ圧「B’」と記す)は0.0108MPaGであり、圧力比B’/A’の中央値は0.63であった。また、高沸分離塔塔頂の圧力の変動は±1%であった。
精製したアセトニトリルの不純物を分析したところ、表15に示す結果を得た。
リボイラー蒸気及びコンデンサー冷却水の使用量は、表16のとおりであった。
2 反応槽
3 高沸分離塔
4 脱水塔
5 低沸分離塔
6 製品塔
7~21 ライン
18a ライン
21a ライン
3a 高沸分離塔リボイラー
3b 高沸分離塔追加リボイラー(製品塔用)
3c 高沸分離塔追加リボイラー(低沸分離塔用)
5v 低沸分離塔コンデンサー行き分岐弁
6v 製品塔コンデンサー行き分岐弁
51v 高沸分離塔追加リボイラーバイパス弁(低沸分離塔塔底液用)
Claims (8)
- アンモ酸化反応により生成した、水を含有するアセトニトリルにアルカリを加えて反応させた後、反応混合物を第一の蒸留塔に供給し、得られた留出液をさらにアルカリと混合したものをアセトニトリル相と水相とに分離した後、前記水相を除去し、前記アセトニトリル相を第二の蒸留塔に供給する工程を含むアセトニトリルの精製方法であって、
前記第二の蒸留塔からの留出蒸気を前記第一の蒸留塔のリボイラーの熱源とするアセトニトリルの精製方法。 - 前記留出蒸気の一部を前記リボイラーに供給し、残部を前記第二の蒸留塔に接続されたコンデンサーに供給する、請求項1記載のアセトニトリルの精製方法。
- 前記第一の蒸留塔のリボイラー圧力(留出蒸気側、ゲージ圧)及び前記第二の蒸留塔の塔頂圧力(ゲージ圧)を基準として、前記リボイラーへの前記留出蒸気の供給量を決定する、請求項1又は2記載のアセトニトリルの精製方法。
- 前記第一の蒸留塔のリボイラー圧力を、前記第二の蒸留塔の塔頂圧力の0.90倍以下にする、請求項3記載のアセトニトリルの精製方法。
- 反応槽、第一の蒸留塔、脱水塔、及び第二の蒸留塔がこの順に設けられており、
水を含有するアセトニトリルとアルカリが前記反応槽で反応した後、反応混合物が第一の蒸留塔に流入され、前記第一の蒸留塔の留出液は前記脱水塔に流入され、前記脱水塔で得られるアセトニトリル相が第二の蒸留塔に流入されるようになっており、
前記第二の蒸留塔の留出蒸気が、前記第一の蒸留塔のリボイラーの熱源とされるアセトニトリルの精製装置。 - 前記留出蒸気の一部が前記リボイラーに供給され、残部は前記第二の蒸留塔に接続されたコンデンサーに供給される、請求項5記載のアセトニトリルの精製装置。
- 前記第一の蒸留塔のリボイラー圧力(留出蒸気側、ゲージ圧)及び前記第二の蒸留塔の塔頂圧力(ゲージ圧)を基準として、前記リボイラーへの前記留出蒸気の供給量が決定される、請求項5又は6記載のアセトニトリルの精製装置。
- 前記第一の蒸留塔のリボイラー圧力が、前記第二の蒸留塔の塔頂圧力の0.90倍以下である、請求項7記載のアセトニトリルの精製装置。
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- 2013-03-22 CN CN201380014926.XA patent/CN104203909B/zh active Active
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- 2013-03-22 WO PCT/JP2013/058368 patent/WO2013146609A1/ja active Application Filing
- 2013-03-22 KR KR1020147020166A patent/KR101648653B1/ko active IP Right Grant
- 2013-03-25 TW TW102110542A patent/TWI453185B/zh active
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WO2015055843A1 (en) * | 2013-10-18 | 2015-04-23 | Arkema France | Unit and process for purification of crude methyl methacrylate |
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US10793505B2 (en) | 2013-10-18 | 2020-10-06 | Arkema France | Unit and process for purification of crude methyl methacrylate |
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US10336690B2 (en) | 2014-02-24 | 2019-07-02 | Honeywell International Inc. | Methods and systems for processing an acetonitrile waste stream |
CN104193651A (zh) * | 2014-08-15 | 2014-12-10 | 江苏九天高科技股份有限公司 | 一种用于醋酸氨化合成乙腈的精制方法及装置 |
CN107812393A (zh) * | 2017-10-27 | 2018-03-20 | 烟台国邦化工机械科技有限公司 | 一种甲醇三效精馏系统及工艺 |
CN115180756A (zh) * | 2022-06-10 | 2022-10-14 | 武汉北湖云峰环保科技有限公司 | 一种乙腈废液的纯化回收装置及方法 |
Also Published As
Publication number | Publication date |
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SG11201405296QA (en) | 2014-11-27 |
CN104203909A (zh) | 2014-12-10 |
TW201343616A (zh) | 2013-11-01 |
CN104203909B (zh) | 2016-07-20 |
IN2014DN07599A (ja) | 2015-05-15 |
KR20140112522A (ko) | 2014-09-23 |
JP6143744B2 (ja) | 2017-06-07 |
JPWO2013146609A1 (ja) | 2015-12-14 |
TWI453185B (zh) | 2014-09-21 |
KR101648653B1 (ko) | 2016-08-16 |
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