Disclosure of Invention
The first purpose of the invention is to provide a micro-interface preparation system of cyclic carbonate, which is based on a micro-interface reaction strengthening technology, carbon dioxide is efficiently crushed into micron-sized bubbles by a micro-interface generator and is dispersed into a liquid raw material to form a micro-interface system, so that the gas-liquid phase interface area in a carboxylation reaction kettle is increased by tens of times, the mass transfer rate and the macroscopic hydrogenation rate of gas phase to reaction liquid are greatly increased, the cyclic carbonate is directly synthesized from olefin and carbon dioxide, and the problem of low efficiency of the reaction system caused by insufficient mixing of carbon dioxide and the liquid raw material in the reaction kettle in the prior art is solved.
The second purpose of the invention is to provide a method for preparing cyclic carbonate by using the micro-interface preparation system, the cyclic carbonate obtained by the reaction has high purity and wide application, the application range of the cyclic carbonate is improved, and the method is worthy of wide popularization and application.
In order to achieve the above purpose of the present invention, the following technical solutions are adopted:
the invention provides a micro-interface preparation system of cyclic carbonate, which comprises a stirring kettle and a carboxylation reaction kettle, wherein ionic liquid catalysts are filled in the stirring kettle and the carboxylation reaction kettle;
a micro-interface unit is arranged on the side surface of the stirring kettle, the micro-interface unit is composed of a plurality of external micro-interface generators, a main pipeline which is introduced into the micro-interface unit is simultaneously connected with an oxidant conveying pipeline and two branch pipelines of an olefin conveying pipeline, carbon dioxide is introduced into the micro-interface unit from the gas source conveying pipeline, and the carbon dioxide, the oxidant and the olefin enter the micro-interface unit to be used for crushing the carbon dioxide gas into micro-bubbles at the micron level;
a reaction material liquid inlet is formed in the bottom of the carboxylation reaction kettle and is communicated with the stirring kettle through an overflow pipe, a built-in micro-interface generator is arranged in the carboxylation reaction kettle, and a carbon dioxide feed inlet is formed in the built-in micro-interface generator and is used for dispersing and crushing carbon dioxide into micro bubbles under the condition that the reaction material liquid is used as a medium;
and purifying the oxidized carboxylation reaction liquid reacted in the carboxylation reaction kettle by a flash tank, a dehydration tower and a rectifying tower in sequence to obtain a cyclic carbonate product.
According to the micro-interface preparation system of the cyclic carbonate, the micro-interface unit is arranged in front of the stirring kettle, the micro-interface generator is arranged in the carboxylation reaction kettle, and the entering carbon dioxide gas is dispersed and crushed into micro bubbles, so that the mass transfer effect is improved.
Preferably, the external micro-interface generators are sequentially arranged from top to bottom along the vertical direction.
Preferably, the number of the external micro-interface generators is 3, and a connecting rod is connected between the bottom surface and the top surface between the adjacent micro-interface generators.
The micro interface unit of the invention is arranged at the outer side of the stirring kettle and is arranged in a mode of being sequentially arranged from top to bottom, and the oxidant, the olefin and the carbon dioxide are collected and then enter the micro-interface unit through the main pipeline, because the raw materials are added in a summarized mode, the fusion effect among the raw materials is improved, the carbon dioxide is added into each micro-interface generator in parallel, namely, a micro-interface system is formed in each micro-interface generator, so as to realize that the gas phase is fully dispersed and crushed in the micro interface generator on the premise of taking the liquid phase as a medium, the micro interface generator at the middle part is closest to the gas phase feed inlet, therefore, the micro-interface system is used as a micro-interface system for mainly dispersing and crushing, and then the two micro-interface generators on the upper part and the lower part form a secondary micro-interface system and a tertiary micro-interface system, and the effect of strengthening the carboxylation reaction is also achieved.
In addition, in order to play a good role in fixing, a connecting rod is specially arranged between the micro-interface generators so as to play a role in strengthening the fixing.
The reaction liquid after the addition reaction is carried out from the stirred tank enters the carboxylation reaction kettle from the overflow pipe through the inlet of the reaction liquid after the liquid level reaches the kettle top, the carboxylation oxidation reaction is further carried out in the carboxylation reaction kettle, a carbon dioxide feed inlet is arranged on the side surface of the built-in micro-interface generator in the carboxylation reaction kettle, and in order to enable the built-in micro-interface generator to be more stable, supports are specially arranged on two sides of the built-in micro-interface generator and are fixed in the carboxylation reaction kettle.
The micro-interface unit and the built-in micro-interface generator crush the carbon dioxide into micro-bubbles with the diameter of more than or equal to 1 mu m and less than 1mm, so that the carbon dioxide contacts with the epoxy compound generated in situ in the state of the micro-bubbles to increase the phase boundary mass transfer area between the carbon dioxide and the epoxy compound generated in situ in the carboxylation reaction process, and the carbon dioxide and the epoxy compound are fully mixed and then subjected to carboxylation reaction, thereby solving the problem that the reaction efficiency of the system is reduced because the carbon dioxide and the epoxy compound cannot be fully mixed in a stirring kettle and a carboxylation reaction kettle in the prior art.
The external micro-interface generator and the internal micro-interface generator are of a pneumatic type, and carbon dioxide, olefin solution and oxidant solution are introduced into the micro-interface generator and then dispersed and crushed, so that the subsequent hydrogenation reaction is enhanced, impurities such as sulfur, nitrogen and the like are removed, and the mass transfer effect is improved.
Preferably, the oxidant conveying pipeline is connected with an oxidant storage tank, and tert-butyl hydroperoxide or hydrogen peroxide is stored in the oxidant storage tank. The first delivery pump is preferably arranged on the oxidant delivery line.
Preferably, the olefin conveying pipeline is connected with an olefin storage tank, and is used for conveying the olefin solution in the olefin storage tank to the micro interface unit through the olefin conveying pipeline. The olefin transfer line is preferably provided with a second transfer pump.
It will be appreciated by those skilled in the art that the micro-interface generator used in the present invention is described in the prior patents of the present inventor, such as the patents of application nos. CN201610641119.6, 201610641251.7, CN201710766435.0, CN106187660, CN105903425A, CN109437390A, CN205833127U and CN 207581700U. The detailed structure and operation principle of the micro bubble generator (i.e. micro interface generator) is described in detail in the prior patent CN201610641119.6, which describes that "the micro bubble generator comprises a body and a secondary crushing member, wherein the body is provided with a cavity, the body is provided with an inlet communicated with the cavity, the opposite first end and second end of the cavity are both open, and the cross-sectional area of the cavity decreases from the middle of the cavity to the first end and second end of the cavity; the secondary crushing member is disposed at least one of the first end and the second end of the cavity, a portion of the secondary crushing member is disposed within the cavity, and an annular passage is formed between the secondary crushing member and the through holes open at both ends of the cavity. The micron bubble generator also comprises an air inlet pipe and a liquid inlet pipe. "the specific working principle of the structure disclosed in the application document is as follows: liquid enters the micro-bubble generator tangentially through the liquid inlet pipe, and gas is rotated at a super high speed and cut to break gas bubbles into micro-bubbles at a micron level, so that the mass transfer area between a liquid phase and a gas phase is increased, and the micro-bubble generator in the patent belongs to a pneumatic micro-interface generator.
In addition, the first patent 201610641251.7 describes that the primary bubble breaker has a circulation liquid inlet, a circulation gas inlet and a gas-liquid mixture outlet, and the secondary bubble breaker communicates the feed inlet with the gas-liquid mixture outlet, which indicates that the bubble breakers all need to be mixed with gas and liquid, and in addition, as can be seen from the following drawings, the primary bubble breaker mainly uses the circulation liquid as power, so that the primary bubble breaker belongs to a hydraulic micro-interface generator, and the secondary bubble breaker simultaneously introduces the gas-liquid mixture into an elliptical rotating ball for rotation, thereby realizing bubble breaking in the rotating process, so that the secondary bubble breaker actually belongs to a gas-liquid linkage micro-interface generator. In fact, the micro-interface generator is a specific form of the micro-interface generator, whether it is a hydraulic micro-interface generator or a gas-liquid linkage micro-interface generator, however, the micro-interface generator adopted in the present invention is not limited to the above forms, and the specific structure of the bubble breaker described in the prior patent is only one of the forms that the micro-interface generator of the present invention can adopt.
Furthermore, the prior patent 201710766435.0 states that the principle of the bubble breaker is that high-speed jet flows are used to achieve mutual collision of gases, and also states that the bubble breaker can be used in a micro-interface strengthening reactor to verify the correlation between the bubble breaker and the micro-interface generator; moreover, in the prior patent CN106187660, there is a related description on the specific structure of the bubble breaker, see paragraphs [0031] to [0041] in the specification, and the accompanying drawings, which illustrate the specific working principle of the bubble breaker S-2 in detail, the top of the bubble breaker is a liquid phase inlet, and the side of the bubble breaker is a gas phase inlet, and the liquid phase coming from the top provides the entrainment power, so as to achieve the effect of breaking into ultra-fine bubbles, and in the accompanying drawings, the bubble breaker is also seen to be of a tapered structure, and the diameter of the upper part is larger than that of the lower part, and also for better providing the entrainment power for the liquid phase. Since the micro-interface generator was just developed in the early stage of the prior patent application, the micro-interface generator was named as a micro-bubble generator (CN201610641119.6), a bubble breaker (201710766435.0) and the like in the early stage, and is named as a micro-interface generator in the later stage along with the continuous technical improvement, and the micro-interface generator in the present invention is equivalent to the micro-bubble generator, the bubble breaker and the like in the prior art, and has different names.
In summary, the micro-interface generator of the present invention belongs to the prior art, although some bubble breakers belong to the type of pneumatic bubble breakers, some bubble breakers belong to the type of hydraulic bubble breakers, and some bubble breakers belong to the type of gas-liquid linkage bubble breakers, the difference between the types is mainly selected according to the different specific working conditions, and in addition, the connection between the micro-interface generator and the reactor and other equipment, including the connection structure and the connection position, is determined according to the structure of the micro-interface generator, which is not limited.
The liquid catalyst is a bifunctional catalyst of imidazole bicarbonate ionic liquid, the type of the oxidizing agent is t-butyl peroxygen aqueous solution (the mass fraction of t-butyl hydroperoxide is 70%), and the type of the catalyst is not limited as long as the oxidative carboxylation reaction can be smoothly performed.
Preferably, the oxidation carboxylation reaction liquid enters from the side wall of the flash tank, a flash product outlet is arranged at the top of the flash tank, a catalyst outlet is arranged at the bottom of the flash tank, the catalyst outlet is connected with the side wall of the carboxylation reaction kettle and used for returning the ionic liquid catalyst, and the flash product outlet is connected with the dehydration tower and used for dehydrating the flash product.
The oxidation carboxylation reaction liquid is conveyed to the inside of the flash tank for flash evaporation treatment, the ionic liquid catalyst after flash evaporation treatment is circularly returned to the inside of the carboxylation reaction kettle for being used for the oxidation carboxylation reaction in the reaction kettle again, and flash evaporation products obtained by flash evaporation are conveyed to the product purification unit (a dehydration tower and a rectification tower). And the product purification unit is used for sequentially dehydrating and rectifying other products obtained by flash evaporation to finally obtain the product cyclic carbonate.
Preferably, the dehydration product from the dehydration tower enters the rectification tower for rectification, the obtained product is stored in a finished product tank, the finally obtained product is collected and stored in the finished product tank, and the product is generally extracted from the side line of the rectification tower. And other components generated in the reaction process are removed from the system. For example, the gas phase from the top of the rectifying tower returns to the gas source conveying pipeline again to be used as raw materials.
The invention also provides a preparation method of the cyclic carbonate micro-interface preparation system, which comprises the following steps:
and (3) dispersing and crushing a mixed micro interface of the olefin solution and the carbon dioxide, performing carboxylation reaction, and performing flash evaporation, dehydration and rectification to obtain a product for collection.
Preferably, the temperature of the carboxylation reaction is 50-80 ℃, and the pressure of the carboxylation reaction is 0.1-1 MPa.
Specifically, the preparation method comprises the steps of smashing carbon dioxide into micro-bubbles with micron scale through a micro interface, releasing the micro-bubbles into the carboxylation reaction kettle, so as to increase the mass transfer area of a phase boundary between the carbon dioxide and the in-situ generated cyclic carbonate in the carboxylation reaction process, fully contacting the carbon dioxide with the in-situ generated epoxy compound in a micro-bubble state, and carrying out carboxylation reaction.
The product obtained by the cyclic carbonate reaction has good quality and high yield. The preparation method of the cyclic carbonate has low reaction temperature, greatly reduced pressure and high liquid hourly space velocity, which is equivalent to improving the productivity.
Before starting the system, firstly, filling an ionic liquid catalyst into a stirring kettle and a carboxylation reaction kettle, filling olefin into an olefin storage tank, filling tert-butyl hydroperoxide/hydrogen peroxide into an oxidant storage tank, feeding carbon dioxide into the system from a gas source conveying pipeline, starting the system, and quantitatively conveying the olefin, the oxidant and the carbon dioxide into a micro-interface unit.
After the olefin and the oxidant are dispersed and crushed by the micro interface unit, the olefin and the oxidant are subjected to oxidation reaction in the stirring kettle to generate an epoxy compound, the epoxy compound and carbon dioxide are subjected to carboxylation reaction to generate cyclic carbonate, in addition, a built-in micro interface generator positioned in the carboxylation reaction kettle is used for crushing the carbon dioxide into micro bubbles with a micron scale and releasing the micro bubbles into the reaction kettle so as to increase the mass transfer area of a phase boundary between the carbon dioxide and the epoxy compound in the carboxylation reaction process, so that the carbon dioxide is fully contacted with the epoxy compound in a micro bubble state and subjected to carboxylation reaction.
Compared with the prior art, the invention has the beneficial effects that:
(1) according to the micro-interface preparation system of the cyclic carbonate, before the carboxylation reaction of the carbon dioxide and the epoxy compound generated in situ is carried out, the micro-interface generator breaks the carbon dioxide into micro bubbles with the diameter of more than or equal to 1 mu m and less than 1mm, so that the carbon dioxide is contacted with the cyclic carbonate generated in situ in the state of the micro bubbles to increase the phase boundary mass transfer area between the carbon dioxide and the cyclic carbonate generated in situ in the carboxylation reaction process, and the carbon dioxide and the cyclic carbonate are fully mixed and then subjected to the carboxylation reaction, thereby solving the problem that the reaction efficiency of the system is reduced because the carboxylation reaction of the carbon dioxide and the cyclic carbonate cannot be fully mixed in a reaction kettle in the prior art;
(2) the micro-interface preparation system of the invention returns the carbon dioxide and the catalyst obtained by final separation to be recycled, thereby further saving the production cost;
(3) according to the reinforced reaction process for preparing the cyclic carbonate through the oxidation carboxylation reaction of the low-pressure olefin and the carbon dioxide, the imidazole bicarbonate ionic liquid is used as the bifunctional catalyst, so that the olefin and the carbon dioxide are directly subjected to the oxidation carboxylation reaction to prepare the cyclic carbonate, the raw material cost is reduced, the separation and storage of epoxy compounds are avoided, and the production flow is simplified.
Examples
Referring to fig. 1, the system for preparing a micro-interface of cyclic carbonate according to an embodiment of the present invention mainly includes a stirring tank 20 and a carboxylation reaction tank 14, a micro-interface unit is disposed on a side surface of the stirring tank 20, the micro-interface unit is composed of a plurality of external micro-interface generators 19, the external micro-interface generators 19 are sequentially disposed from top to bottom along a vertical direction, a connecting rod for fixing is connected between a bottom surface and a top surface between adjacent external micro-interface generators 19, and the number of the external micro-interface generators 19 is preferably 3.
A main pipeline 25 which is led into the micro-interface unit is simultaneously connected with two branch pipelines of an oxidant conveying pipeline 24 and an olefin conveying pipeline 23 and is simultaneously connected with a gas source conveying pipeline 13, carbon dioxide, oxidant and olefin enter the interior of the micro-interface generator to be used for breaking carbon dioxide gas into micro-bubbles with micron level, and 200g of imidazole bicarbonate ionic liquid catalyst is filled in the stirring kettle 20 and the carboxylation reaction kettle 14; the olefin storage tank 11 is connected to an olefin transfer pipe 23 for transferring 1kg of styrene stored in the olefin storage tank 11 into the stirred tank 20 through the olefin transfer pipe 23, and a second transfer pump 29 is provided in the olefin transfer pipe 23 for transferring the styrene by a second circulation pump in order to increase the transfer power. The oxidizer storage tank 12 is connected to an oxidizer delivery pipe 24 for delivering 2kg of a tert-butyl hydroperoxide aqueous solution (the mass fraction of tert-butyl hydroperoxide is 70%) in the oxidizer storage tank 12 into the stirred tank 20 through the oxidizer delivery pipe 24, and in order to improve the power transmission, a first delivery pump 28 is provided in the oxidizer delivery pipe 24 for delivering the aqueous solution by a first circulation pump. In addition, the gas source conveying pipeline 13 ensures that a sufficient amount of carbon dioxide gas source exists, the system is started, the temperature of the system is set to be 50 ℃, and the pressure is set to be 1.0 MPa.
In the stirring kettle 20, the gas phase dispersed and crushed by the micro interface unit is easier to perform cycloaddition reaction with the raw material and the oxidant, the stirring kettle 20 is provided with a condensing coil of a speed-adjustable motor, and the condensing coil is heated by a jacket. The reaction liquid level reaches an overflow pipe 27, and the overflow pipe 27 enters the interior of the carboxylation reaction kettle 14 from a reaction liquid inlet 26 at the bottom of the carboxylation reaction kettle 14 through a pipeline, so that the reaction is further completed.
In the carboxylation reaction kettle 14, styrene is oxidized by tert-butyl hydroperoxide to generate styrene oxide under the catalysis of imidazole bicarbonate ionic liquid, meanwhile, the built-in micro-interface generator 21 breaks carbon dioxide into micro-bubbles with micron scale, and releases the micro-bubbles into the carboxylation reaction kettle 14, so that the carbon dioxide fully contacts with the in-situ generated styrene oxide in the micro-bubbles state, and carboxylation reaction is carried out.
The oxidation carboxylation reaction liquid which is subjected to carboxylation reaction is conveyed to a flash tank 15, a flash product outlet is formed in the top of the flash tank 15, a catalyst outlet is formed in the bottom of the flash tank 15, the oxidation carboxylation reaction liquid is subjected to flash evaporation treatment, after the flash evaporation is finished, the ionic liquid catalyst in the flash product is discharged through the catalyst outlet and then circulated to the interior of the carboxylation reaction kettle 14 for the oxidation carboxylation reaction in the interior of the carboxylation reaction kettle 14 again, and the flash product except the catalyst is conveyed to a subsequent product purification unit.
The flash evaporation product conveyed to the product purification unit is sequentially dehydrated and rectified through a dehydrating tower 16 and a rectifying tower 17, the dehydrating tower 16 is used for dehydrating the flash evaporation product, the rectifying tower 17 is used for rectifying the dehydration product, and finally the styrene cyclic carbonate product is obtained and collected and stored in a finished product tank 18. Other components generated in the reaction process are removed by a system, the yield of the styrene cyclic carbonate is about 85 percent when the styrene cyclic carbonate is detected, and the gas phase discharged from the top of the rectifying tower 17 is returned to the gas source conveying pipeline 13 for recycling.
In the above embodiment, the micro-interface generator converts the pressure energy of the gas and/or the kinetic energy of the liquid into the surface energy of the bubbles and transmits the surface energy of the bubbles to the bubbles, so that the bubbles are broken into micro-bubbles with a diameter of more than or equal to 1 μm and less than 1mm, and the micro-bubbles are divided into a pneumatic micro-interface generator, a hydraulic micro-interface generator and a gas-liquid linkage micro-interface generator according to an energy input mode or a gas-liquid ratio, wherein the pneumatic micro-interface generator is driven by gas, and the input gas amount is far greater than the liquid amount; the hydraulic micro-interface generator is driven by liquid, and the input air quantity is generally smaller than the liquid quantity; the gas-liquid linkage type micro-interface generator is driven by gas and liquid at the same time, and the input gas amount is close to the liquid amount. The micro-interface generator is one or more of a pneumatic micro-interface generator, a hydraulic micro-interface generator and a gas-liquid linkage micro-interface generator.
In order to increase the dispersion and mass transfer effects, an additional micro-interface generator can be additionally arranged, the installation position is not limited actually, the micro-interface generator can be arranged externally or internally, and the micro-interface generator can be arranged on the side wall in the kettle in a relative mode when the micro-interface generator is arranged internally so as to realize the opposite flushing of micro-bubbles discharged from the outlet of the micro-interface generator.
In the above embodiment, the number of the pump bodies is not specifically required, and the pump bodies may be arranged at corresponding positions as required.
In the above examples, other operating conditions were unchanged, and when the reaction temperature was set to 65 ℃ and the pressure was set to 0.5MPa, the yield was 88%.
In the above examples, other operating conditions were unchanged, and when the reaction temperature was set at 80 ℃ and the pressure was set at 0.1MPa, the yield was 92%.
In addition, the pressure and the temperature in the carboxylation reaction kettle 14 are reduced by laying the micro-interface generator, and the energy consumption is sufficiently reduced.
In a word, compared with the micro-interface preparation system of the cyclic carbonate in the prior art, the micro-interface preparation system of the cyclic carbonate has the advantages of fewer equipment components, small occupied area, low energy consumption, low cost, high safety, controllable reaction and high raw material conversion rate, is equivalent to providing a micro-interface preparation system with stronger operability for the field of the cyclic carbonate, and is worthy of wide popularization and application.
Finally, it should be noted that: the above embodiments are only used to illustrate the technical solution of the present invention, and not to limit the same; while the invention has been described in detail and with reference to the foregoing embodiments, it will be understood by those skilled in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; and the modifications or the substitutions do not make the essence of the corresponding technical solutions depart from the scope of the technical solutions of the embodiments of the present invention.