CN109851579B - Process for producing alkylene oxide - Google Patents
Process for producing alkylene oxide Download PDFInfo
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- CN109851579B CN109851579B CN201810153539.9A CN201810153539A CN109851579B CN 109851579 B CN109851579 B CN 109851579B CN 201810153539 A CN201810153539 A CN 201810153539A CN 109851579 B CN109851579 B CN 109851579B
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Abstract
The invention relates to a method for producing alkylene oxide, which mainly solves the problems of the prior art that the purity of an extracting agent is reduced, the loss is increased, the yield of the alkylene oxide is reduced and the energy consumption is increased due to the accumulation of heavy component impurities. The process comprises the steps of separating a stream comprising alkylene oxide and extractant in a separation column having a first reboiler; the method is characterized in that a part of material flow in the bottom of the separation tower enters an extractant purifier for treatment, the obtained gas-phase light component returns to the separation tower, and the liquid-phase heavy component is subjected to post-treatment. The method can be used in the industrial production of alkylene oxide.
Description
Technical Field
The present invention relates to a process for producing alkylene oxide.
Background
Propylene Oxide (PO) is mainly used for the production of polyether polyols, propylene glycol and propylene glycol ethers, the second largest propylene derivatives being produced next to polypropylene in propylene derivatives. It was calculated that in 2011, about 66% of the total consumption of propylene oxide was used globally for polyether polyol production, about 17% for propylene glycol production, and about 6% for propylene oxide for propylene glycol ether production. In 2011, the global propylene oxide production capacity is 882.2 ten thousand tons, and in 2016, 1000 ten thousand tons are broken through. By 2020, propylene oxide production capacity is expected to reach 1200 ten thousand tons/year and demand is expected to reach 1000 ten thousand tons/year. In the long term, the market prospect of propylene oxide is still optimistic worldwide.
1, 2-ringsThe family of homologues of oxybutane (BO), Ethylene Oxide (EO) and Propylene Oxide (PO), the molecular formula of which is C4H8O (CAS number: 106-88-7), a substance with a three-membered ring structure, is chemically active and is mainly used as an intermediate for polyether polyol monomers and other synthetic materials. The 1, 2-butylene oxide can also be used for preparing foam plastics, synthetic rubber, nonionic surfactants and the like, can also be used as a diluent of nitrolacquer instead of acetone, and can also be used as a standard substance for chromatographic analysis.
As the olefin epoxide, butylene oxide has a larger amount of-CH in its molecular structure than ethylene oxide and propylene oxide2Functional groups, which, when used as monomers for the synthesis of polyether polyols, give products with excellent hydrophobic properties, and are particularly suitable for the outer surface waterproofing of certain demanding buildings and equipment. Meanwhile, the polyurethane material synthesized by copolymerization with the butylene oxide as a monomer has excellent cold resistance, and is particularly suitable for cold climate areas.
The alkylene oxide product has strict requirements on water, aldehyde and isomers, the water can influence the hydroxyl value and the foaming performance of a polymer, the aldehyde can cause the product to emit peculiar smell and influence the health of people, and the isomers are end capping agents of a polymerized long chain, so that the product purity is strictly required in national standards and enterprise standards.
The quality and purity requirements of the high-class products of the propylene oxide in the national standard are as follows: more than or equal to 99.95 percent of propylene oxide, less than or equal to 0.02 percent of water, less than or equal to 0.005 percent of acetaldehyde and propionaldehyde, and less than or equal to 0.003 percent of acid.
The quality and purity requirements of the qualified 1, 2-butylene oxide product in BASF enterprise standards are as follows: more than or equal to 99.5 percent of butylene oxide, less than or equal to 0.2 percent of butylene oxide isomer, less than or equal to 0.05 percent of total aldehyde and less than or equal to 0.03 percent of water.
The quality and purity requirements of the 1, 2-epoxybutane superior products are as follows: more than or equal to 99.9 percent of butylene oxide, less than or equal to 0.1 percent of butylene oxide isomer, less than or equal to 0.015 percent of total aldehyde and less than or equal to 0.005 percent of water.
The crude alkylene oxide produced by the reaction usually contains impurities such as water, methanol, acetone, methyl formate and the like, and because the impurities form an azeotrope with the alkylene oxide or the relative volatility is close to 1, the common rectification can not reach the standards of the alkylene oxide product. In order to obtain high-purity alkylene oxide satisfying the polymerization requirements, impurities contained in the alkylene oxide must be separated and removed.
The purification of alkylene oxide generally uses C7-C20 straight-chain and branched-chain hydrocarbons and/or glycols as extractant. For economic reasons, the purification of alkylene oxides uses a mixture of linear and branched alkanes of C8 as extractant. The addition of the extracting agent increases the relative volatility of acetaldehyde, water, methanol and methyl formate to the alkylene oxide, the acetaldehyde, water, methanol and methyl formate are removed from the top of the tower, and the extracting agent is recycled.
Since the crude butylene oxide contains water and methanol, and water is added during the separation, the following reaction occurs during the purification of butylene oxide:
the 1, 2-butylene oxide is hydrolyzed to generate 1, 2-butylene glycol. The solubility of 1, 2-butanediol in water is less than 1, 2-butylene oxide.
Reaction of 1, 2-epoxybutane with methanol produces 1-butanediol monomethyl ether (ether bond formed on carbon atom of terminal epoxy group) and 2-butanediol monomethyl ether (ether bond formed on carbon atom of 2-position epoxy group). Both 1-butanediol monomethyl ether and 2-butanediol monomethyl ether are sparingly soluble in water.
The 1, 2-butylene oxide is polymerized to form polymers, such as butylene oxide dimer and butylene oxide.
The 1, 2-butylene oxide reacts with water, dihydric alcohol or polyhydric alcohol and other compounds containing active hydrogen to generate poly 1, 2-butylene glycol ether and derivatives thereof. The poly 1, 2-butylene glycol ether and the derivatives thereof are non-volatile viscous liquid, colorless to brown, and mostly soluble in ketone, alcohol, ester, hydrocarbon and halogenated hydrocarbon; lower molecular weight is soluble in water, and water solubility decreases with increasing molecular weight and decreases with increasing temperature.
Most of the above reaction by-products and derivatives are hardly soluble in water and are hardly removed by a water washing method. When the epoxybutane is refined by adopting an extractive distillation method, the byproducts and derivatives can be accumulated in the extractant, so that the extraction effect of the extractant is reduced. Therefore, it is highly desirable to reduce the concentration of these by-products and derivatives in the extractant. For example, document US4402794 discloses a single extractive rectification separation of impurities such as water, methanol, acetone, methyl formate and the like contained in a crude 1, 2-butylene oxide solution using C7-C9 hydrocarbons, preferably n-octane, as an extractant, without involving the separation of impurity aldehydes. The organic layer obtained after layering by the phase separator at the top of the extractive distillation tower is sent to a rectifying tower to distill and separate methanol, acetone and the like; feeding the material flow in the bottom of the extractive distillation tower into an extractive distillation tower; and discharging the tower bottom liquid of the extraction and rectification tower. The method reduces the accumulation of reaction byproducts and derivatives in the extractant by discharging part of the tower bottoms containing the extractant and heavy components. Because the heavy component content in the discharged part of the material flow at the bottom of the tower is low, a large amount of extractant needs to be discharged to ensure the purity of the extractant, and a large amount of extractant is lost.
Document US4772732 discloses a process for purifying butene oxide by using an anion exchange resin and an adsorbent. The anion exchange resin removes acid and dehydrogenation impurities, while the adsorbent removes water from impurities of butylene oxide. The purification steps may be carried out individually or in combination, depending on the impurity content, and the process may be carried out batchwise in a reactor or continuously in a column or column. The ion exchange resin selected is a sulfonated macroreticular anion exchange resin and the adsorbent is a molecular sieve. The method has high cost, troublesome adsorption and analysis process and low treatment capacity.
Also, in propylene oxide systems, propylene oxide is hydrolyzed to produce 1, 2-propanediol. 1, 2-propanediol has a lower solubility in water than propylene oxide.
Propylene oxide reacts with methanol to produce propylene glycol monomethyl ether.
The propylene oxide is polymerized to form polymers, such as dimeric propylene oxide and polypropyleneoxide.
Propylene oxide reacts with active hydrogen-containing compounds such as water, diols or polyols to produce polypropylene glycol ethers and derivatives thereof. The solubility of the polypropylene glycol ether and its derivatives in water and in the organic phase is not great.
The current situation of the prior art is that a method for producing alkylene oxide with low loss of an extracting agent, high purity, high yield of alkylene oxide and low energy consumption is urgently needed.
Disclosure of Invention
The present inventors have assiduously studied a system based on the prior art and found that at least one of the aforementioned problems can be solved by additionally providing an extractant purifier at the bottom of a conventional separation column equipped with a reboiler, and thus completed the present invention.
In particular, the present invention relates to a process for the production of alkylene oxides. The process comprises the steps of separating a stream comprising alkylene oxide and extractant in a separation column having a first reboiler; it is characterized in that a part of the material flow in the bottom of the separation tower enters an extractant purifier.
According to one aspect of the invention, the gas phase light components obtained after the extraction agent purifier treatment are returned to the separation tower, and the liquid phase heavy components are subjected to post-treatment.
According to an aspect of the invention, the first reboiler is any one of a thermosiphon reboiler, a kettle reboiler or a forced circulation reboiler.
According to one aspect of the invention, the extractant purifier is a distillation column or a second reboiler, preferably a second reboiler.
According to an aspect of the invention, the second reboiler is any one of a thermosyphon reboiler, a kettle reboiler or a forced circulation reboiler, preferably a kettle reboiler.
According to one aspect of the invention, the ratio of the heat exchange area of the first reboiler to the heat exchange area of the second reboiler is (5-2): 1.
According to one aspect of the invention, the portion of the bottom stream of the separation column entering the extractant purifier is 2-20% of the weight of the bottom stream of the separation column.
According to one aspect of the invention, the operating conditions of the separation column include: the temperature at the top of the tower is 30-80 ℃, and the pressure is 0.04-0.40 MPaG.
According to one aspect of the invention, the alkylene oxide is propylene oxide, butylene oxide, or an isomer thereof.
According to one aspect of the invention, the stream comprising alkylene oxide and extractant is derived from an extract product stream obtained after extractive distillation of an olefin epoxidation reaction product.
According to one aspect of the invention, the ratio of the extracting agent to the alkylene oxide in the alkylene oxide and extracting agent-containing stream is (2-15): 1, preferably (3-10): 1, more preferably (5-7): 1, in mole percent.
The invention has the beneficial effects that: the invention adds an extracting agent purifier at the bottom of a conventional separation tower provided with a reboiler, and the preferable scheme is that the reboiler is added at the bottom of the separation tower, and part of the tower bottom product which is directly discharged is treated by the extracting agent purifier to separate heavy component impurities, so that the purity of the extracting agent is improved, the loss and the energy consumption of the extracting agent are reduced, the yield of the epoxyalkane is improved, the purity of the extracting agent is improved by 0.1-2%, the loss of the extracting agent is 0.1-1.0%, the energy consumption is reduced by 1-10%, and the yield of the epoxyalkane is improved by 0.5-5%.
Drawings
FIG. 1 is a schematic flow diagram of the process of the present invention.
Fig. 2 is a schematic flow diagram of a process described in prior art document US 4402794.
In the drawings, like parts are provided with like reference numerals. The drawings are not to scale.
Description of reference numerals:
1 feed stream
2 column bottom stream of separation column
3 alkylene oxide product stream
4 first reboiler feed stream
5 first reboiler discharge stream
6 extractant purifier feed stream
7 heavy ends contaminant stream-efflux stream
8 extractant clarifier discharge stream
9 extractant stream
A first reboiler
Purifier for B extracting agent
C separating tower
The invention is described in detail below with reference to the drawings, but it is to be noted that the scope of the invention is not limited thereto, but is defined by the appended claims.
All publications, patent applications, patents, and other references mentioned in this specification are herein incorporated by reference in their entirety. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. In case of conflict, the present specification, including definitions, will control.
When the specification concludes with claims with the heading "known to those skilled in the art", "prior art", or the like, to derive materials, substances, methods, procedures, devices, or components, etc., it is intended that the subject matter derived from the heading encompass those conventionally used in the art at the time of filing this application, but also include those that are not currently in use, but would become known in the art to be suitable for a similar purpose.
In the context of the present specification, anything or things which are not mentioned, except where explicitly stated, are directly applicable to those known in the art without any changes. Moreover, any embodiment described herein may be freely combined with one or more other embodiments described herein, and the technical solutions or concepts resulting therefrom are considered part of the original disclosure or original disclosure of the invention, and should not be considered as new matters not disclosed or contemplated herein, unless a person skilled in the art would consider such a combination to be clearly unreasonable.
Unless otherwise expressly indicated, all percentages, parts, ratios, etc. mentioned in this specification are by weight unless otherwise not in accordance with the conventional knowledge of those skilled in the art.
The feedstock for the production process of the present invention is a stream comprising alkylene oxide and an extractant. The material flow is derived from an extraction product flow obtained by extracting and rectifying an olefin epoxidation reaction product. The alkylene oxide content of the material flow is 5-25 wt%.
The use of extractive agents for the purification of alkylene oxides is well known. Generally, C7-C20 straight-chain and branched-chain hydrocarbons and/or glycols are used as the extractant. For economic reasons, mixtures of C8 linear and branched alkanes are used as extractants, for example n-octane, isooctane, 2-methyl-heptane. From the viewpoint of reducing the cost of the extractant, it is preferable to select a mixture.
According to the invention, after the stream containing the alkylene oxide and the extractant is rectified in the separation tower, the bottom stream of the tower contains the extractant and heavy components. In the case of butylene oxide, these heavy components include 1, 2-butanediol, 1-butanediol monomethyl ether, 2-butanediol monomethyl ether, butylene oxide dimer, butylene oxide, poly-1, 2-butanediol ether and derivatives thereof, or mixtures thereof. In the case of propylene oxide, these heavy components include 1, 2-propylene glycol, propylene glycol monomethyl ether, dipropylene glycol, polypropylene oxide, polypropylene glycol ethers and derivatives thereof, or mixtures thereof.
According to the invention, in FIG. 1, a stream 1 containing alkylene oxide and an extractant is fed to a separation column C, an alkylene oxide product stream 3 is removed from the top of the separation column, and a stream 2 is obtained at the bottom of the separation column. The bottom of the separation tower C is provided with a first reboiler A and an extractant purifier B. And the first reboiler feed stream 4 feeds the tower bottom liquid into the first reboiler A to be heated to obtain a first reboiler discharge stream 5, and the first reboiler discharge stream 5 enters the lower part of the separation tower C. And part of the material flow 2 is used as an extractant purifier feed material flow 6, the tower bottom liquid is sent to an extractant purifier B, a material flow 8 discharged from the extractant purifier B is obtained after heating, the material flow 8 discharged from the extractant purifier B is sent to the lower part of a separation tower C, and a heavy component impurity material flow 7 is discharged from the bottom of the extractant purifier B. And part of the material flow 9 which does not enter the extractant purifier B in the material flow 2 in the tower bottom of the separation tower is removed as an extractant material flow and can be recycled to the alkylene oxide extraction and rectification process. In the material flow 2 at the bottom of the separation tower, part of the material flow 6 entering the extractant purifier is 2-20% of the material flow 2 at the bottom of the separation tower by weight.
The preferred scheme of the invention is to add a reboiler at the bottom of the conventional separation tower provided with one reboiler, namely to arrange two reboilers at the bottom of the separation tower. For a newly-built device, the equipment investment can be saved, the loss amount of the extracting agent is reduced, and the product quality is improved; the method is particularly suitable for the transformation and upgrading of the old device, has small modification amplitude and low investment, reduces the loss of the extracting agent and has obvious effect.
It should be noted that, under the condition that the purity of the extracting agent is not changed, the separation effect of the extraction and rectification is certain. However, the present invention emphasizes that the diol and the derivative thereof are inevitably produced as impurities by side reactions in the reaction or separation and purification processes, and the impurities are cumulatively circulated in the system. These impurities are adverse to extractive distillation, and reduce the extraction effect of the extractant. If the extractant is directly discharged outside, the extractant is directly discharged outside because of low content of heavy component impurities in the extractant, and the loss amount of the extractant is large. According to the invention, only one small-sized extractant purifier is added, so that the concentration of heavy components in the discharged material flow 7 can be improved by more than 1 time, and the loss of the discharged extractant is reduced by more than half. By adopting the invention, under the condition of the same discharge amount of the extracting agent, the content of heavy component impurities in the circulating extracting agent is 50 percent of that of a direct discharge scheme after long-period operation. If a direct discharge scheme is adopted, in order to improve the product quality of the alkylene oxide, the yield of the alkylene oxide must be reduced, otherwise, the product quality cannot be ensured.
Fig. 2 shows the prior art, a feed stream 1 containing 1, 2-butylene oxide and an extractant is fed into a separation column C, a 1, 2-butylene oxide product stream 3 is removed from the top of the separation column, an extractant stream 2 is removed from the bottom of the separation column C, a reboiler a is arranged at the bottom of the separation column C, a reboiler a feed stream 4 feeds a tower bottom liquid into the reboiler a for heating to obtain a reboiler a discharge stream 5, the reboiler a discharge stream is fed into the lower part of the separation column C, and one stream separated from the extractant stream 2 is discharged out of a separation system as a heavy component impurity stream 7. A greater amount of extractant is lost due to the reduced accumulation of reaction by-products and derivatives in the extractant by venting a portion of the extractant and heavies.
The invention is further illustrated by the following specific embodiments.
Detailed Description
[ example 1 ]
According to the process flow shown in fig. 1, the extractant is n-octane, the ratio of the extractant to 1, 2-butylene oxide is 8:1 in mol percent in the feed stream containing 1, 2-butylene oxide and the extractant, the separating tower reboiler a adopts a thermosyphon reboiler, the extractant purifier B is a thermosyphon reboiler, the ratio of the heat exchange areas of the reboiler a and the reboiler B is 5:1, and the part entering the extractant purifier accounts for 3% of the bottom stream of the separating tower in weight percent.
The purity of the 1, 2-epoxybutane material flow at the top of the separation tower is 99.95 percent, the recovery rate is 99.80 percent, the purity of the extractant at the bottom of the separation tower is 99.0 percent, and the loss of the extractant is 0.70 percent.
[ example 2 ]
According to the process flow shown in fig. 1, the extractant is n-octane, the ratio of the extractant to 1, 2-butylene oxide is 7:1 in mol percent in the feed stream containing 1, 2-butylene oxide and the extractant, the separating tower reboiler a adopts a thermosyphon reboiler, the extractant purifier B is a kettle reboiler, the heat exchange area ratio of the reboiler a to the reboiler B is 5:1, and the part entering the extractant purifier accounts for 5 wt% of the bottom stream of the separating tower.
The purity of the 1, 2-epoxybutane material flow at the top of the separation tower is 99.95 percent, the recovery rate is 99.82 percent, the purity of the extractant at the bottom of the separation tower is 99.0 percent, and the loss of the extractant is 0.75 percent.
[ example 3 ]
According to the process flow shown in fig. 1, the extractant is n-octane, the ratio of the extractant to 1, 2-butylene oxide is 6:1 in mol percent in the feed stream containing 1, 2-butylene oxide and the extractant, the separating tower reboiler a adopts a thermosyphon reboiler, the extractant purifier B is a kettle reboiler, the heat exchange area ratio of the reboiler a to the reboiler B is 5:1, and the part entering the extractant purifier accounts for 8% in weight percent of the kettle stream of the separating tower.
The purity of the 1, 2-epoxybutane material flow at the top of the separation tower is 99.95 percent, the recovery rate is 99.85 percent, the purity of the extractant at the bottom of the separation tower is 99.0 percent, and the loss of the extractant is 0.78 percent.
[ example 4 ]
According to the process flow shown in fig. 1, the extractant is n-octane, the ratio of the extractant to 1, 2-butylene oxide is 5:1 in mol percent in the feed stream containing 1, 2-butylene oxide and the extractant, the separating tower reboiler a adopts a thermosyphon reboiler, the extractant purifier B is a kettle reboiler, the heat exchange area ratio of the reboiler a to the reboiler B is 5:1, and the part entering the extractant purifier accounts for 10% of the kettle stream of the separating tower in weight percent.
The purity of the 1, 2-epoxybutane material flow at the top of the separation tower is 99.95%, the recovery rate is 99.89%, the purity of the extractant at the bottom of the separation tower is 99.0%, and the loss of the extractant is 0.79%.
[ example 5 ]
According to the process flow shown in fig. 1, the extractant is n-octane, the ratio of the extractant to 1, 2-butylene oxide is 4:1 in mol percent in the feed stream containing 1, 2-butylene oxide and the extractant, the separating tower reboiler a adopts a thermosyphon reboiler, the extractant purifier B is a kettle reboiler, the heat exchange area ratio of the reboiler a to the reboiler B is 5:1, and the part entering the extractant purifier accounts for 13% in weight percent of the kettle stream of the separating tower.
The purity of the 1, 2-epoxybutane material flow at the top of the separation tower is 99.95 percent, the recovery rate is 99.86 percent, the purity of the extractant at the bottom of the separation tower is 99.0 percent, and the loss of the extractant is 0.82 percent.
[ example 6 ]
According to the process flow shown in fig. 1, the extractant is a C8 alkane mixture, the ratio of the extractant to 1, 2-butylene oxide is 4:1 in mol percent in the feed stream containing 1, 2-butylene oxide and the extractant, the reboiler a of the separation column adopts a thermosyphon reboiler, the purifier B of the extractant is a kettle reboiler, the ratio of the heat exchange areas of the reboiler a and the reboiler B is 5:1, and the part entering the purifier of the extractant accounts for 15 wt% of the kettle stream of the separation column.
The purity of the 1, 2-epoxybutane material flow at the top of the separation tower is 99.95 percent, the recovery rate is 99.85 percent, the purity of the extractant at the bottom of the separation tower is 99.0 percent, and the loss of the extractant is 0.85 percent.
[ example 7 ]
According to the process flow shown in fig. 1, the extractant is n-octane, the ratio of the extractant to 1, 2-butylene oxide is 6:1 in mol percent in the feed stream containing 1, 2-butylene oxide and the extractant, the separating tower reboiler a adopts a thermosyphon reboiler, the extractant purifier B is a kettle reboiler, the heat exchange area ratio of the reboiler a to the reboiler B is 4:1, and the part entering the extractant purifier accounts for 7% in weight percent of the bottom stream of the separating tower.
The purity of the 1, 2-epoxybutane material flow at the top of the separation tower is 99.95 percent, the recovery rate is 99.85 percent, the purity of the extractant at the bottom of the separation tower is 99.0 percent, and the loss of the extractant is 0.74 percent.
[ example 8 ]
According to the process flow shown in fig. 1, the extractant is n-octane, the ratio of the extractant to 1, 2-butylene oxide is 6:1 in mol percent in the feed stream containing 1, 2-butylene oxide and the extractant, the separating tower reboiler a adopts a thermosyphon reboiler, the extractant purifier B is a kettle reboiler, the heat exchange area ratio of the reboiler a to the reboiler B is 3:1, and the part entering the extractant purifier accounts for 6% in weight percent of the kettle stream of the separating tower.
The purity of the 1, 2-epoxybutane material flow at the top of the separation tower is 99.95 percent, the recovery rate is 99.86 percent, the purity of the extractant at the bottom of the separation tower is 99.0 percent, and the loss of the extractant is 0.73 percent.
[ example 9 ]
According to the process flow shown in fig. 1, the extractant is n-octane, the ratio of the extractant to 1, 2-butylene oxide is 6:1 in mol percent in the feed stream containing 1, 2-butylene oxide and the extractant, the separating tower reboiler a adopts a thermosyphon reboiler, the extractant purifier B is a kettle reboiler, the ratio of the heat exchange areas of the reboiler a and the reboiler B is 2:1, and the part entering the extractant purifier accounts for 6% in weight percent of the bottom stream of the separating tower.
The purity of the 1, 2-epoxybutane material flow at the top of the separation tower is 99.95 percent, the recovery rate is 99.87 percent, the purity of the extractant at the bottom of the separation tower is 99.0 percent, and the loss of the extractant is 0.75 percent.
[ example 10 ]
According to the process flow diagram shown in fig. 1, the extractant is n-octane, the ratio of the extractant to 1, 2-butylene oxide is 6:1 in mol percent in the feed stream containing 1, 2-butylene oxide and the extractant, the separating tower reboiler a adopts a kettle reboiler, the extractant purifier B is a kettle reboiler, the heat exchange area ratio of the reboiler a to the reboiler B is 2:1, and the part entering the extractant purifier accounts for 6% of the bottom stream of the separating tower in weight percent.
The purity of the 1, 2-epoxybutane material flow at the top of the separation tower is 99.95 percent, the recovery rate is 99.87 percent, the purity of the extractant at the bottom of the separation tower is 99.0 percent, and the loss of the extractant is 0.75 percent.
[ example 11 ]
According to the process flow shown in fig. 1, the extraction agent is n-octane, the ratio of the extraction agent to 1, 2-butylene oxide is 6:1 in mol percent in the feed stream containing 1, 2-butylene oxide and the extraction agent, the separation tower reboiler a adopts a forced circulation reboiler, the extraction agent purifier B is a kettle reboiler, the ratio of the heat exchange areas of the reboiler a and the reboiler B is 2:1, and the part entering the extraction agent purifier accounts for 6% in weight percent of the separation tower kettle stream.
The purity of the 1, 2-epoxybutane material flow at the top of the separation tower is 99.95 percent, the recovery rate is 99.87 percent, the purity of the extractant at the bottom of the separation tower is 99.0 percent, and the loss of the extractant is 0.75 percent.
[ COMPARATIVE EXAMPLE 1 ]
According to the process shown in FIG. 2, the extractant is n-octane, the ratio of the extractant to 1, 2-butylene oxide is 8:1 in mole percent in the feed stream containing 1, 2-butylene oxide and the extractant, and a forced circulation reboiler is used as the reboiler A of the separation column.
The purity of the 1, 2-epoxybutane material flow at the top of the separation tower is 99.95 percent, the recovery rate is 96.38 percent, the purity of the extractant at the bottom of the separation tower is 98.0 percent, and the loss of the extractant is 2.02 percent. Compared with [ example 1 ], the energy consumption for separation is increased by 4.5%.
[ COMPARATIVE EXAMPLE 2 ]
According to the process shown in FIG. 2, the extractant is n-octane, the ratio of the extractant to 1, 2-butylene oxide is 6:1 in mole percent in the feed stream containing 1, 2-butylene oxide and the extractant, and a forced circulation reboiler is used as the reboiler A of the separation column.
The purity of the 1, 2-epoxybutane material flow at the top of the separation tower is 99.95 percent, the recovery rate is 98.50 percent, the purity of the extractant at the bottom of the separation tower is 97.0 percent, and the loss of the extractant is 2.20 percent.
[ COMPARATIVE EXAMPLE 3 ]
According to the process shown in FIG. 2, the extractant is n-octane, the ratio of the extractant to 1, 2-butylene oxide is 4:1 in mole percent in the feed stream containing 1, 2-butylene oxide and the extractant, and a forced circulation reboiler is used as the reboiler A of the separation column.
The purity of the 1, 2-epoxybutane material flow at the top of the separation tower is 99.95 percent, the recovery rate is 98.88 percent, the purity of the extractant at the bottom of the separation tower is 97.5 percent, and the loss of the extractant is 2.45 percent.
[ COMPARATIVE EXAMPLE 4 ]
According to the process shown in FIG. 2, the extractant is n-octane, the ratio of the extractant to 1, 2-butylene oxide is 3:1 in mole percent in the feed stream containing 1, 2-butylene oxide and the extractant, and a forced circulation reboiler is used as the reboiler A of the separation column.
The purity of the 1, 2-epoxybutane material flow at the top of the separation tower is 99.95 percent, the recovery rate is 97.13 percent, the purity of the extractant at the bottom of the separation tower is 98.0 percent, and the loss of the extractant is 2.62 percent.
[ COMPARATIVE EXAMPLE 5 ]
According to the process flow shown in fig. 2, the heavy component impurity stream 7 is recycled after being washed, so as to reduce the loss of the extractant, the extractant is n-octane, the ratio of the extractant to the 1, 2-butylene oxide in the feed stream containing the 1, 2-butylene oxide and the extractant is 6:1 in mole percent, and the reboiler a of the separation tower adopts a forced circulation reboiler.
The purity of the 1, 2-epoxybutane material flow at the top of the separation tower is 99.95 percent, the recovery rate is 97.58 percent, the purity of the extractant at the bottom of the separation tower is 97.50 percent, and the loss of the extractant is 1.72 percent. Compared with [ example 1 ], the energy consumption for separation is increased by 6.8%.
Claims (11)
1. A process for producing alkylene oxide, comprising the step of separating a stream containing alkylene oxide and an extractant in a separation column having a first reboiler; the method is characterized in that a part of material flow at the bottom of a separation tower enters an extractant purifier; the stream containing the olefin oxide and the extracting agent is derived from an extraction product stream obtained by extracting and rectifying an olefin epoxidation reaction product; returning the gas-phase light component obtained after the treatment of the extractant purifier to the separation tower, and performing post-treatment on the liquid-phase heavy component;
the extractant purifier is a second reboiler.
2. The process for producing an alkylene oxide according to claim 1, wherein the first reboiler is any one of a thermosiphon reboiler, a tank reboiler, or a forced circulation reboiler.
3. The process for producing an alkylene oxide according to claim 1, wherein the second reboiler is any one of a thermosyphon reboiler, a kettle reboiler, or a forced circulation reboiler.
4. The alkylene oxide production process of claim 1, wherein the second reboiler is a kettle reboiler.
5. The process for producing an alkylene oxide according to claim 1, wherein the ratio of the heat exchange area of the first reboiler to the heat exchange area of the second reboiler is (5 to 2): 1.
6. The process for producing alkylene oxide according to claim 1, wherein the amount of the extractant purifier introduced into the bottom stream of the separation column is 2 to 20% by weight of the bottom stream of the separation column.
7. The olefin oxide production process according to claim 1, wherein the operating conditions of the separation column include: the temperature at the top of the tower is 30-80 ℃, and the pressure is 0.04-0.40 MPaG.
8. The alkylene oxide production method according to claim 1, wherein the alkylene oxide is propylene oxide, butylene oxide, or an isomer thereof.
9. The alkylene oxide production process according to claim 1, wherein the ratio of the extractant to the alkylene oxide in the stream comprising the alkylene oxide and the extractant is (2-15): 1 in mole percent.
10. The alkylene oxide production process of claim 1, wherein the ratio of extractant to alkylene oxide in the alkylene oxide and extractant containing stream is (3-10): 1, in mole percent.
11. The alkylene oxide production process of claim 1, wherein the ratio of extractant to alkylene oxide in the alkylene oxide and extractant containing stream is (5-7): 1 in mole percent.
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| CN106397363A (en) * | 2015-08-03 | 2017-02-15 | 中国石油化工股份有限公司 | Purifying method for 1,2-epoxybutane |
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| US4772732A (en) * | 1986-05-08 | 1988-09-20 | Basf Corporation | Method for purification of butylene oxide |
| US5453160A (en) * | 1994-05-31 | 1995-09-26 | Texaco Chemical Inc. | Use of mixed polyoxypropylene glycols in the extractive distillation of propylene oxide |
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| US8389750B2 (en) * | 2010-09-28 | 2013-03-05 | Lyondell Chemical Technology, L.P. | Purification of propylene oxide |
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