CN107501096A - Rectifying couples the method for preparing electron level dimethyl carbonate with crystallization - Google Patents
Rectifying couples the method for preparing electron level dimethyl carbonate with crystallization Download PDFInfo
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- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C68/00—Preparation of esters of carbonic or haloformic acids
- C07C68/06—Preparation of esters of carbonic or haloformic acids from organic carbonates
- C07C68/065—Preparation of esters of carbonic or haloformic acids from organic carbonates from alkylene carbonates
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- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
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Abstract
The invention belongs to chemical production technical field, is related to a kind of rectifying and couples the method for preparing electron level dimethyl carbonate with crystallization.A kind of rectifying provided by the invention couples the method for preparing electron level dimethyl carbonate with crystallization, comprises the following steps：Reactive distillation：Using methanol and ethylene carbonate as raw material, in the presence of a catalyst, ester exchange reaction is carried out by reactive distillation column, ethylene glycol solution is obtained at rectifying tower bottom, rectifying column tower top obtains the dimethyl carbonate that mass fraction is 98%~99.5%；Film-falling crystallization：The dimethyl carbonate that rectifying column tower top is obtained is delivered in falling-film crystallizer, is crystallized with progressively cooling method, is cooled to 5 DEG C~2 DEG C stoppings, then by sweating and the whole fusing modes of progressively heating up, obtain the dimethyl carbonate that mass fraction is more than 99.99%.The present invention is simple to operate, easily controllable, and obtained product purity is high, high income, and product quality is stable, and cost is low, and energy consumption is low.
Description
Technical field
The invention belongs to chemical production technical field, is related to the preparation of dimethyl carbonate, in particular to rectifying and knot
The method that brilliant coupling prepares electron level dimethyl carbonate.
Background technology
Dimethyl carbonate, molecular formula C3H5OH, is the liquid of colorless and odorless under normal temperature, 4 DEG C of fusing point, 90.3 DEG C of boiling point, energy
Dissolved each other with organic solvent alcohol, ester, ketone etc..Dimethyl carbonate is listed in nonpoisonous chemicla in Europe within 1992, have it is safe to use,
Conveniently, the advantages that polluting less, easily transporting.Especially, due to its hypotoxicity and hypoergia, it can need the presence of solvent
It is used as the fluid with low environmental impact in a variety of applications, such as the replacement containing fluorous solvent used in electronics industry
Thing.
With the continuous improvement on the booming and electronic component technology of electronic industry, for electronic grade chemicals
Quality requirement more and more higher.And electron level dimethyl carbonate is as the important organic solvent in electronics industry, specifically as life
Produce the important organic solvent of lithium cell electrolyte.Because electrolyte is the critical material in lithium ion battery, the performance of electrolyte
Depending on the quality of various solvents in formula, the water content of high purity carbon dimethyl phthalate product, total alcohol content and other impurities into
The content divided will directly affect the performance of electrolysis liquid product, and then influence the index of battery.Therefore, for electron level carbonic acid diformazan
The quality requirement of ester also more and more higher.
Purification for dimethyl carbonate at present is refined mainly by adsorbing and distill or rectifying, or absorption and rectifying
Combination, but purification mode of the prior art also there is it is certain the problem of, that is, it is low yield to be present, product purity
The problems such as low, unstable product quality and impurity remain, it is impossible to meet growing lithium battery industry for electron level carbon
The demand of dimethyl phthalate solvent.
In consideration of it, special propose the present invention.
The content of the invention
It is an object of the invention to provide a kind of rectifying the method for preparing electron level dimethyl carbonate, the party are coupled with crystallization
Method has that product quality is stable, and purity is high, and the advantages that high income, and method is simple to operate, and energy consumption is low, has good economy
Benefit.
To achieve the above object, the technical solution adopted by the present invention is：
A kind of rectifying couples the method for preparing electron level dimethyl carbonate with crystallization, comprises the following steps：
(a) reactive distillation：Using methanol and ethylene carbonate as raw material, in the presence of a catalyst, by reactive distillation column
Carry out ester exchange reaction, obtain ethylene glycol solution at rectifying tower bottom, rectifying column tower top obtain mass fraction for 98%~
99.5% dimethyl carbonate；
(b) film-falling crystallization：The dimethyl carbonate that rectifying column tower top is obtained is delivered in falling-film crystallizer, progressively to cool
Mode is crystallized, and is cooled to -5 DEG C~2 DEG C stoppings, then by sweating and the whole fusing modes of progressively heating up, obtain quality point
Dimethyl carbonate of the number more than 99.99%.
As further preferred technical scheme, in step (b) film-falling crystallization, comprise the following steps：
(b1) biofilm：The dimethyl carbonate crude product that the mass fraction that rectifying column tower top is obtained is 98%~99.5% adds
At the top of to falling-film crystallizer, dimethyl carbonate crude product is circulated with given pace, dimethyl carbonate crude product is in crystallizer with liquid film
Mode flows down；
(b2) decrease temperature crystalline：Crystallized with progressively cooling method so that dimethyl carbonate forms crystalline substance in crystallizer wall
Layer, -5 DEG C~2 DEG C are cooled to, stop charging, constant temperature 1h~2h, uncrystallized mother liquor is discharged from falling-film crystallizer bottom, and
It is recycled at the top of crystallizer and continues to crystallize；
(b3) heat up sweating：Melted in a manner of the sweating that progressively heats up, be warming up to 4 DEG C~6 DEG C, constant temperature 0.5h~2h,
Sweating is discharged；
(b4) all fusings：Continue to raise temperature, crystalline solid is all melted, products obtained therefrom is arranged from falling-film crystallizer bottom
Enter into products pot, that is, obtain the dimethyl carbonate that mass fraction is more than 99.99%.
As further preferred technical scheme, in described step (b1) biofilm, the cycle rate of dimethyl carbonate crude product
For 0.5L/h~5L/h.
As further preferred technical scheme, in described step (b1) biofilm, using double down film pattern, in film-falling crystallization
Liquid distributor and cooling medium distribution plate are provided with device, dimethyl carbonate crude product is in crystallizer from liquid distributor stream in a manner of liquid film
Under；Cooling medium is outside Crystallizer tube in a manner of liquid film under cooling medium distribution plate stream.
As further preferred technical scheme, in described step (b2) decrease temperature crystalline, cooling step-length is 0.5 DEG C/h~2
℃/h。
As further preferred technical scheme, described step (b3) heating sweating in, heating step-length for 1 DEG C/h~5 DEG C/
h。
As further preferred technical scheme, in step (a) reactive distillation, in addition to pre-reaction, by ethylene carbonate
Ester and methanol mix according to the ratio that mol ratio is 1: 5~1: 10, are sent into the reactor equipped with catalyst and carry out pre-reaction, in advance
Obtained mixture is reacted to be re-fed into reactive distillation column.
As further preferred technical scheme, the catalyst includes alkali metal hydroxide, alkali metal oxide, alkali gold
Belong to the one or more in alcoholates or carbonate.
As further preferred technical scheme, in step (a) reactive distillation, described reactive distillation column is pressurization essence
Tower is evaporated, the operating pressure of compression rectification tower is 8Mpa~12Mpa, and operation temperature is 150 DEG C~200 DEG C.
As further preferred technical scheme, the reflux ratio of the reactive distillation column is 15~25, number of theoretical plate is 30~
60。
Compared with prior art, the beneficial effects of the present invention are：
1st, rectifying provided by the invention couples the method for preparing electron level dimethyl carbonate with crystallization, first with methanol and carbonic acid
Vinyl acetate is the dimethyl carbonate that raw material is made that purity is 98%~99.5% by reaction rectification method, then passes through film-falling crystallization
The dimethyl carbonate product that purity is more than 99.99% is made in technology, realizes the industrial production of serialization, and obtained product
Purity is high, high income, and product quality is stable, and cost is low, alleviates and prepares in the prior art existing for high purity carbon dimethyl phthalate
High energy consumption, high cost, the problem of product quality is difficult to control.
2nd, present invention process is simple, easy to operate, easily controllable, and energy consumption is low, and equipment investment is few, and operating cost is low, stable,
Reliably, it is safe；And it is simple in construction, easily realize, there is considerable economic benefit, be adapted to large-scale production.
Brief description of the drawings
, below will be to specific in order to illustrate more clearly of the specific embodiment of the invention or technical scheme of the prior art
The required accompanying drawing used is briefly described in embodiment or description of the prior art, it should be apparent that, in describing below
Accompanying drawing is some embodiments of the present invention, for those of ordinary skill in the art, before creative work is not paid
Put, other accompanying drawings can also be obtained according to these accompanying drawings.
Fig. 1 is rectifying provided in an embodiment of the present invention with crystallizing the technique for coupling the method for preparing electron level dimethyl carbonate
Schematic flow sheet.
Icon：100- pre-reactors；200- reactive distillation columns；201- condensers；202- reboilers；300- dimethyl carbonates
Crude product storage tank；301- feed liquid delivery pumps；400- ethylene glycol storage tanks；500- falling-film crystallizers；600- crystalline mother solution storage tanks；601- is female
Liquid delivery pump；700- products pots.
Embodiment
Technical scheme is clearly and completely described below in conjunction with embodiment and embodiment,
Obviously, described embodiment is part of the embodiment of the present invention, rather than whole embodiments.Based on the implementation in the present invention
Example, the every other embodiment that those of ordinary skill in the art are obtained under the premise of creative work is not made, is belonged to
The scope of protection of the invention.Unreceipted actual conditions person, the condition suggested according to normal condition or manufacturer are carried out.Agents useful for same
Or the unreceipted production firm person of instrument, it is the conventional products that can be obtained by commercially available purchase.
A kind of rectifying couples the method for preparing electron level dimethyl carbonate with crystallization, comprises the following steps：
(a) reactive distillation：Using methanol and ethylene carbonate as raw material, in the presence of a catalyst, by reactive distillation column
Carry out ester exchange reaction, obtain ethylene glycol solution at rectifying tower bottom, rectifying column tower top obtain mass fraction for 98%~
99.5% dimethyl carbonate；
(b) film-falling crystallization：The dimethyl carbonate that rectifying column tower top is obtained is delivered in falling-film crystallizer, progressively to cool
Mode is crystallized, and is cooled to -5 DEG C~2 DEG C stoppings, then by sweating and the whole fusing modes of progressively heating up, obtain quality point
Dimethyl carbonate of the number more than 99.99%.
To alleviate, energy consumption present in the purification preparation method of dimethyl carbonate in the prior art is big, product quality is unstable
Calmly, the problems such as cost is high, the method for preparing electron level dimethyl carbonate is coupled the invention provides rectifying with film-falling crystallization.The party
Method carries out ester exchange reaction first using methanol and ethylene carbonate as raw material, by reactive distillation, wherein, reaction rectification technique is
It is a kind of to combine reaction and rectifying, carry out simultaneously within one device, the product for reacting generation is separated in time, then can be carried
The yield of high product, and separate product using reaction heat, so as to reach the purpose of energy-conservation.Further, ester exchange is using anti-
The method for answering rectifying, can greatly improve the conversion per pass of ester exchange reaction, at the same whole flow process by reactive distillation column and
The energy of crystallizer integrates, and can greatly reduce energy consumption.In addition, film-falling crystallization technology is a kind of new organic system separation skill
Art, belong in fusion-crystallization technology and chromatograph one kind of fusion-crystallization, film-falling crystallization technology collects crystallization, centrifugation, dried in one
Body, it is particularly suitable for separating azeotrope system, heat sensitive material and isomer, there are efficiency high, low power consumption and other advantages.
Dimethyl carbonate is prepared by the way of reactive distillation couples with film-falling crystallization, with other existing mode of operation phases
Than not only with simple to operate, high income, product purity is high, and product purity has reached more than 99.99%, disclosure satisfy that high-purity
The indices requirement of the dimethyl carbonate of electron level is spent, and energy consumption is low, it is easy to accomplish industrialized large-scale production, it is economical
It is profitable.
It should be noted that in the present invention, dimethyl carbonate mass fraction that rectifying column tower top obtains for 98%~
99.5%, such as can be 98%, 98.2%, 98.4%, 98.5%, 98.6%, 98.8%, 99%, 99.2% or 99.5%.
In practical application, micro change can be done according to specific operating condition, as long as in this interval range.
In described film-falling crystallization step, be cooled to -5 DEG C~2 DEG C stoppings, for example, can be -5 DEG C, -4 DEG C, -3 DEG C, -2
DEG C, -1 DEG C, 0 DEG C, 1 DEG C or 2 DEG C., can by cooling outlet temperature control in the framework of the present definition in actual production
Ensure certain product purity, and can ensures certain percent crystallization in massecuite.
In a kind of optional embodiment, in step (b) film-falling crystallization, comprise the following steps：
(b1) biofilm：The dimethyl carbonate crude product that the mass fraction that rectifying column tower top is obtained is 98%~99.5% adds
At the top of to falling-film crystallizer, dimethyl carbonate crude product is circulated with given pace, dimethyl carbonate crude product is in crystallizer with liquid film
Mode flows down；
(b2) decrease temperature crystalline：Crystallized with progressively cooling method so that dimethyl carbonate forms crystalline substance in crystallizer wall
Layer, -5 DEG C~2 DEG C are cooled to, stop charging, constant temperature 1h~2h, uncrystallized mother liquor is discharged from falling-film crystallizer bottom, and
It is recycled at the top of crystallizer and continues to crystallize；
(b3) heat up sweating：Melted in a manner of the sweating that progressively heats up, be warming up to 4 DEG C~6 DEG C, constant temperature 0.5h~2h,
Sweating is discharged；
(b4) all fusings：Continue to raise temperature, crystalline solid is all melted, products obtained therefrom is arranged from falling-film crystallizer bottom
Enter into products pot, that is, obtain the dimethyl carbonate that mass fraction is more than 99.99%.
Described dimethyl carbonate crude product is 98%~99.5% dimethyl carbonate obtained by rectifying column tower top.
The purity of product is helped to ensure that by the way of progressively cooling method, and by the way of Recycling Mother Solution, can
To improve the utilization rate of raw material, the waste of resource is reduced, and energy consumption is low, and easy to operate, obtained product quality is also higher.Its
Constant temperature 1h~2h again after cooling stops, optionally, constant temperature 1h, 1.5h or 2h.
Suitable sweating temperature and sweating sessions, it can cause under the conditions of certain percent crystallization in massecuite is ensured, ensure product
Purity.The temperature of sweating terminal is 4 DEG C~6 DEG C, such as can be 4 DEG C, 4.5 DEG C, 5 DEG C, 5.5 DEG C or 6 DEG C；Again constant temperature 0.5h~
2h, such as can be 0.5h, 1h, 1.5h or 2h.
In a kind of optional embodiment, in described step (b1) biofilm, the cycle rate of dimethyl carbonate crude product is
0.5L/h~5L/h.
The internal circulating load of material is fewer during film-falling crystallization, and circulation time is longer, and its distribution coefficient is bigger, and makes product pure
Degree reduces, while percent crystallization in massecuite increase, therefore need to keep certain internal circulating load., can be big according to the volume of crystallizer in practical application
It is small to determine internal circulating load.Cycle rate in present embodiment for example can be 0.5L/h, 1L/h, 1.5L/h, 2L/h, 2.5L/
H, 3L/h, 3.5L/h, 4L/h, 4.5L/h or 5L/h.
In a kind of optional embodiment, in described step (b1) biofilm, using double down film pattern, in falling-film crystallizer
Liquid distributor and cooling medium distribution plate are inside provided with, dimethyl carbonate crude product is in crystallizer from liquid distributor stream in a manner of liquid film
Under；Cooling medium is outside Crystallizer tube in a manner of liquid film under cooling medium distribution plate stream.
Using the pattern of double down film, i.e., raw material in crystallization Bottomhole pressure and cooling medium flows outside crystallizer, crystallization effect
Fruit is more preferable, easy to operate, easily controllable, and product quality is stable.
In a kind of optional embodiment, in described step (b2) decrease temperature crystalline, cooling step-length be 0.5 DEG C/h~2 DEG C/
h。
The step-length that cools is that rate of temperature fall has a certain impact to the purity and yield of crystal.The reduction of one side rate of temperature fall
Make crystal growth rate slack-off, be advantageous to impurity at solid-liquid two-phase interface and transmitted into liquid phase, improve crystal purity；The opposing party
Face, with the raising of rate of temperature fall, impurity content more and more higher in liquid phase so that the Crystal impurity content increase of precipitation, and tie
Brilliant rate increases on the contrary.Therefore, the separating capacity i.e. purity of product that suitable rate of temperature fall should be in crystallization process be met, simultaneously
Certain production capacity should also be taken into account.The typical but non-limiting step-length that cools is, for example, 0.5 DEG C/h, 1 DEG C/h, 1.5 DEG C/h or 2
℃/h。
In a kind of optional embodiment, in described step (b3) heating sweating, heating step-length is 1 DEG C/h~5 DEG C/h.
It is too fast that heating step-length is that heating rate is not easy, too fast mass crystallization to be caused to melt so that product yield declines；
It was not easy to that slowly, the operation cycle can be extended slowly excessively, it is also unhelpful to improving production capacity.So the sweating heating step-length of the present invention is
1 DEG C/h~5 DEG C/h, its it is typical but non-limiting be, for example, 1 DEG C/h, 1.5 DEG C/h, 2 DEG C/h, 2.5 DEG C/h, 3 DEG C/h, 3.5 DEG C/
H, 4 DEG C/h, 4.5 DEG C/h or 5 DEG C/h.
In a kind of optional embodiment, in step (a) reactive distillation, in addition to pre-reaction, by ethylene carbonate
Mixed with methanol according to the ratio that mol ratio is 1: 5~1: 10, be sent into the reactor equipped with catalyst and carry out pre-reaction, it is pre- anti-
The mixture that should be obtained is re-fed into reactive distillation column.
Raw material first carries out pre-reaction before into reactive distillation column, is then squeezed into mixture in rectifying column with pump, rectifying column
By the way of midsection continuous feed, the energy consumption of rectifying column can be saved, saves equipment investment, improves production efficiency, is shortened
Production cycle.The mol ratio of its ethylene carbonate and methanol can be configured according to practical operation condition.
In a kind of optional embodiment, the catalyst includes alkali metal hydroxide, alkali metal oxide, alkali metal
One or more in alcoholates or carbonate.
It should be noted that the catalyst can be sodium hydroxide, potassium hydroxide, sodium methoxide, caustic alcohol or potassium carbonate,
But this is not limited to, other kinds of catalyst can also be used.
In a kind of optional embodiment, in step (a) reactive distillation, described reactive distillation column is compression rectification
Tower, the operating pressure of compression rectification tower is 8Mpa~12Mpa, and operation temperature is 150 DEG C~200 DEG C.
In a kind of optional embodiment, the reflux ratio of the reactive distillation column is 15~25, and number of theoretical plate is 30~60.
Under conditions of reactive distillation column operation temperature, operating pressure, reflux ratio and the number of theoretical plate that the present invention recommends, tower
It is more than 98% to push up obtained product purity, and yield is up to more than 99.5%.
Below in conjunction with embodiment and accompanying drawing, the present invention will be further described in detail.
Embodiment 1
The present embodiment provides a kind of rectifying and couples the method for preparing electron level dimethyl carbonate with crystallization, and its technological process is such as
Shown in Fig. 1.
In Fig. 1, including pre-reactor 100, reactive distillation column 200, dimethyl carbonate crude product storage tank 300, ethylene glycol storage tank
400th, feed liquid delivery pump 301, falling-film crystallizer 500, crystalline mother solution storage tank 600, mother liquor delivery pump 601 and products pot 700.Its
In, the tower top of reactive distillation column 200 is provided with condenser 201, and bottom of towe is provided with reboiler 202, pre-reactor 100 and reaction essence
The charging aperture for evaporating tower 200 is connected, and the tower top outlet of reactive distillation column 200 is connected with dimethyl carbonate crude product storage tank 300, carbonic acid two
Methyl esters crude product storage tank 300 is connected with its top feed mouth of falling-film crystallizer 500, the discharging opening of falling-film crystallizer 500 respectively with knot
Brilliant mother liquor holding tank 600 is connected with products pot 700, and the charging aperture that crystalline mother solution storage tank 600 also has falling-film crystallizer 500 is connected
To carry out Recycling Mother Solution；The bottom of towe outlet of reactive distillation column 200 is connected with ethylene glycol storage tank 400.
The rectifying that the present embodiment provides couples the method for preparing electron level dimethyl carbonate with crystallization, specifically includes following step
Suddenly：
(1) reactive distillation：Using methanol and ethylene carbonate as raw material, its ethylene carbonate and methanol are 1 according to mol ratio:
5, it is sent into the pre-reactor 100 equipped with catalyst sodium methoxide and carries out pre-reaction, the mixture that pre-reaction obtains is re-fed into reaction
In rectifying column 200, reactive distillation column 200 is compression rectification tower, and the operating pressure of compression rectification tower is 8Mpa~9Mpa, operation temperature
Spend for 180 DEG C~200 DEG C, reflux ratio 20, number of theoretical plate 40.
Ethylene glycol solution is obtained in the bottom of towe of reactive distillation column 200；Tower top obtains the dimethyl carbonate that mass fraction is 99%
Crude product.
(2) biofilm：The dimethyl carbonate crude product that mass fraction in dimethyl carbonate crude product storage tank 300 is 99% is passed through
Feed liquid delivery pump 301 is delivered in falling-film crystallizer 500, circulates dimethyl carbonate crude product with given pace, dimethyl carbonate is thick
Product in crystallizer in a manner of liquid film under liquid distributor stream, cooling medium is outside Crystallizer tube from cooling medium point in a manner of liquid film
Flowed down with disk, wherein the cycle rate of dimethyl carbonate crude product is 2L/h.
(3) decrease temperature crystalline：Crystallized with progressively cooling method so that dimethyl carbonate forms crystalline substance in crystallizer wall
Layer, cooling step-length be 1 DEG C/h, crystallization time 6h, is cooled to 1 DEG C, and stopping is fed, constant temperature 1h, by uncrystallized mother liquor from drop
The bottom of membrane crystallizer 500 is expelled in crystalline mother solution storage tank 600, and mother liquor is recycled into falling liquid film knot by mother liquor delivery pump 601
The brilliant its top feed mouth of device 500 continues to crystallize.
(4) heat up sweating：Melted in a manner of the sweating that progressively heats up, heating step-length is 3.5 DEG C/h, is warming up to 5 DEG C, perseverance
Warm 1h, sweating is discharged；
(b4) all fusings：Continue to raise temperature, crystalline solid is all melted, products obtained therefrom is from the bottom of falling-film crystallizer 500
Portion is discharged into products pot 700, obtains the dimethyl carbonate that mass fraction is 99.9991%, yield 99.8%.
Embodiment 2
The rectifying that the present embodiment provides couples the method for preparing electron level dimethyl carbonate with crystallization, specifically includes following step
Suddenly：
(1) reactive distillation：Using methanol and ethylene carbonate as raw material, its ethylene carbonate and methanol are 1 according to mol ratio:
8, it is sent into the pre-reactor 100 equipped with catalyst sodium methoxide and carries out pre-reaction, the mixture that pre-reaction obtains is re-fed into reaction
In rectifying column 200, reactive distillation column 200 is compression rectification tower, and the operating pressure of compression rectification tower is 10Mpa~12Mpa, operation
Temperature is 160 DEG C~190 DEG C, reflux ratio 25, number of theoretical plate 50.
Ethylene glycol solution is obtained in the bottom of towe of reactive distillation column 200；Tower top obtains the carbonic acid diformazan that mass fraction is 99.5%
Ester crude product.
(2) biofilm：The dimethyl carbonate crude product that mass fraction in dimethyl carbonate crude product storage tank 300 is 99.5% is led to
Cross feed liquid delivery pump 301 to be delivered in falling-film crystallizer 500, dimethyl carbonate crude product, dimethyl carbonate are circulated with given pace
Crude product in crystallizer in a manner of liquid film under liquid distributor stream, cooling medium is outside Crystallizer tube from cooling medium in a manner of liquid film
Distribution plate flows down, and wherein the cycle rate of dimethyl carbonate crude product is 4L/h.
(3) decrease temperature crystalline：Crystallized with progressively cooling method so that dimethyl carbonate forms crystalline substance in crystallizer wall
Layer, cooling step-length be 2 DEG C/h, crystallization time 4h, is cooled to -2 DEG C, and stopping is fed, constant temperature 1.5h, by uncrystallized mother liquor from
The bottom of falling-film crystallizer 500 is expelled in crystalline mother solution storage tank 600, and mother liquor is recycled into falling liquid film by mother liquor delivery pump 601
Its top feed mouth of crystallizer 500 continues to crystallize.
(4) heat up sweating：Melted in a manner of the sweating that progressively heats up, heating step-length is 3 DEG C/h, is warming up to 6 DEG C, constant temperature
1.5h, sweating is discharged；
(5) all fusings：Continue to raise temperature, crystalline solid is all melted, products obtained therefrom is from the bottom of falling-film crystallizer 500
It is discharged into products pot 700, obtains the dimethyl carbonate that mass fraction is 99.9995%, yield 99.7%.
Embodiment 3
The rectifying that the present embodiment provides couples the method for preparing electron level dimethyl carbonate with crystallization, specifically includes following step
Suddenly：
(1) reactive distillation：Using methanol and ethylene carbonate as raw material, its ethylene carbonate and methanol are 1 according to mol ratio:
10, it is sent into the pre-reactor 100 equipped with catalyst sodium methoxide and carries out pre-reaction, the mixture that pre-reaction obtains is re-fed into reaction
In rectifying column 200, reactive distillation column 200 is compression rectification tower, and the operating pressure of compression rectification tower is 8Mpa~12Mpa, operation
Temperature is 150 DEG C~200 DEG C, reflux ratio 15, number of theoretical plate 30.
Ethylene glycol solution is obtained in the bottom of towe of reactive distillation column 200；Tower top obtains the carbonic acid diformazan that mass fraction is 98.5%
Ester crude product.
(2) biofilm：The dimethyl carbonate crude product that mass fraction in dimethyl carbonate crude product storage tank 300 is 98.5% is led to
Cross feed liquid delivery pump 301 to be delivered in falling-film crystallizer 500, dimethyl carbonate crude product, dimethyl carbonate are circulated with given pace
Crude product in crystallizer in a manner of liquid film under liquid distributor stream, cooling medium is outside Crystallizer tube from cooling medium in a manner of liquid film
Distribution plate flows down, and wherein the cycle rate of dimethyl carbonate crude product is 0.5L/h.
(3) decrease temperature crystalline：Crystallized with progressively cooling method so that dimethyl carbonate forms crystalline substance in crystallizer wall
Layer, cooling step-length be 0.5 DEG C/h, crystallization time 8h, is cooled to 2 DEG C, and stopping is fed, constant temperature 2h, by uncrystallized mother liquor from
The bottom of falling-film crystallizer 500 is expelled in crystalline mother solution storage tank 600, and mother liquor is recycled into falling liquid film by mother liquor delivery pump 601
Its top feed mouth of crystallizer 500 continues to crystallize.
(4) heat up sweating：Melted in a manner of the sweating that progressively heats up, heating step-length is 1 DEG C/h, is warming up to 4 DEG C, constant temperature
2h, sweating is discharged；
(b4) all fusings：Continue to raise temperature, crystalline solid is all melted, products obtained therefrom is from the bottom of falling-film crystallizer 500
Portion is discharged into products pot 700, obtains the dimethyl carbonate that mass fraction is 99.9987%, yield 99.9%.
Finally it should be noted that：Various embodiments above is merely illustrative of the technical solution of the present invention, rather than its limitations；To the greatest extent
The present invention is described in detail with reference to foregoing embodiments for pipe, it will be understood by those within the art that：Its according to
The technical scheme described in foregoing embodiments can so be modified, either which part or all technical characteristic are entered
Row equivalent substitution；And these modifications or replacement, the essence of appropriate technical solution is departed from various embodiments of the present invention technology
The scope of scheme.
Claims (10)
1. a kind of rectifying couples the method for preparing electron level dimethyl carbonate with crystallization, it is characterised in that comprises the following steps：
(a) reactive distillation：Using methanol and ethylene carbonate as raw material, in the presence of a catalyst, carried out by reactive distillation column
Ester exchange reaction, ethylene glycol solution is obtained at rectifying tower bottom, it is 98%~99.5% that rectifying column tower top, which obtains mass fraction,
Dimethyl carbonate；
(b) film-falling crystallization：The dimethyl carbonate that rectifying column tower top is obtained is delivered in falling-film crystallizer, with progressively cooling method
Crystallized, be cooled to -5 DEG C~2 DEG C stoppings, then by sweating and the whole fusing modes of progressively heating up, it is big to obtain mass fraction
In 99.99% dimethyl carbonate.
2. rectifying according to claim 1 couples the method for preparing electron level dimethyl carbonate with crystallization, it is characterised in that
In step (b) film-falling crystallization, comprise the following steps：
(b1) biofilm：The dimethyl carbonate crude product that the mass fraction that rectifying column tower top is obtained is 98%~99.5% is added to drop
At the top of membrane crystallizer, dimethyl carbonate crude product is circulated with given pace, dimethyl carbonate crude product is in crystallizer in a manner of liquid film
Flow down；
(b2) decrease temperature crystalline：Crystallized with progressively cooling method so that dimethyl carbonate forms crystal layer, drop in crystallizer wall
Temperature stops charging, constant temperature 1h~2h, uncrystallized mother liquor discharged from falling-film crystallizer bottom, and be recycled to -5 DEG C~2 DEG C
Continue to crystallize at the top of crystallizer；
(b3) heat up sweating：Melted in a manner of the sweating that progressively heats up, be warming up to 4 DEG C~6 DEG C, constant temperature 0.5h~2h, will send out
Sweat is discharged；
(b4) all fusings：Continue raise temperature, make crystalline solid all melt, products obtained therefrom from falling-film crystallizer bottom be discharged into
In products pot, that is, obtain the dimethyl carbonate that mass fraction is more than 99.99%.
3. rectifying according to claim 2 couples the method for preparing electron level dimethyl carbonate with crystallization, it is characterised in that
In described step (b1) biofilm, the cycle rate of dimethyl carbonate crude product is 0.5L/h~5L/h.
4. rectifying according to claim 2 couples the method for preparing electron level dimethyl carbonate with crystallization, it is characterised in that
In described step (b1) biofilm, using double down film pattern, liquid distributor and cooling medium distribution are provided with falling-film crystallizer
Disk, dimethyl carbonate crude product is in crystallizer in a manner of liquid film under liquid distributor stream；Cooling medium is outside Crystallizer tube with liquid film
Mode flows down from cooling medium distribution plate.
5. rectifying according to claim 2 couples the method for preparing electron level dimethyl carbonate with crystallization, it is characterised in that
In described step (b2) decrease temperature crystalline, cooling step-length is 0.5 DEG C/h~2 DEG C/h.
6. rectifying according to claim 2 couples the method for preparing electron level dimethyl carbonate with crystallization, it is characterised in that
In described step (b3) heating sweating, heating step-length is 1 DEG C/h~5 DEG C/h.
7. the rectifying according to claim any one of 1-6 couples the method for preparing electron level dimethyl carbonate with crystallization, its
It is characterised by, according to mol ratio is 1: 5 by ethylene carbonate and methanol in step (a) reactive distillation, in addition to pre-reaction
~1: 10 ratio mixing, is sent into the reactor equipped with catalyst and carries out pre-reaction, and the mixture that pre-reaction obtains is re-fed into
In reactive distillation column.
8. rectifying according to claim 7 couples the method for preparing electron level dimethyl carbonate with crystallization, it is characterised in that
The catalyst includes the one or more in alkali metal hydroxide, alkali metal oxide, alkali alcoholate or carbonate.
9. the rectifying according to claim any one of 1-6 couples the method for preparing electron level dimethyl carbonate with crystallization, its
It is characterised by, in step (a) reactive distillation, described reactive distillation column is compression rectification tower, the operation of compression rectification tower
Pressure is 8Mpa~12Mpa, and operation temperature is 150 DEG C~200 DEG C.
10. the rectifying according to claim any one of 1-6 couples the method for preparing electron level dimethyl carbonate with crystallization, its
It is characterised by, the reflux ratio of the reactive distillation column is 15~25, and number of theoretical plate is 30~60.
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