CN111943849A - High-efficiency energy-saving ethyl lactate reaction rectification production method and device - Google Patents
High-efficiency energy-saving ethyl lactate reaction rectification production method and device Download PDFInfo
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Abstract
The invention relates to a high-efficiency energy-saving ethyl lactate reaction rectification production method and a device, which are composed of a reaction rectification tower and a product refining tower or a reaction rectification complete thermal coupling tower, wherein lactic acid and ethanol enter the reaction rectification tower from the top and the bottom of a reaction section, tower kettle materials enter a product refining tower again, a high-purity ethyl lactate product is obtained at the top of the product refining tower, lactic acid is extracted from the tower kettle and circulated to the reaction rectification tower, and product water is discharged from the top of the reaction rectification tower. The invention realizes that the steady-state feeding molar ratio of lactic acid and ethanol is 1:1, increases the molar ratio of lactic acid and ethanol through the reaction rectification reaction zone, promotes the complete conversion of ethanol, and avoids the difficult problem of azeotropic separation of ethanol and product water which are not completely reacted. The quality purity of the product reaches more than 99 percent, and the yield reaches more than 98 percent. The invention has the advantages that the reaction rectifying tower and the product refining tower are coupled and integrated by a complete thermal coupling method, thereby further realizing the great saving of production energy consumption and saving the equipment investment cost.
Description
Technical Field
The invention relates to the technical field of synthesis of an organic solvent ethyl lactate in the field of chemical industry, in particular to a high-efficiency energy-saving ethyl lactate reaction rectification production method and a device; a method and a device for producing ethyl lactate with high efficiency and energy saving by utilizing a reactive distillation technology under the condition of lactic acid circulation.
Background
Solvents are widely used in almost all production and process industries. The common solvent is mainly produced by using non-renewable petroleum as a raw material, a large amount of carbon dioxide and volatile organic pollutants (VOCs) are released in the production process, and the ethyl lactate organic solvent replaces the traditional solvent (such as halogenated solvents, ethers, chlorofluorocarbon solvents and the like) to play a vital role in reducing carbon/pollution emission in China.
Ethyl lactate, also known as alpha-hydroxypropionic acid ethyl ester, has a molecular formula of C5H10O3The melting point is 26 ℃, the boiling point is 154.5 ℃, the solvent is a green environment-friendly solvent, has good biodegradability, and can be widely applied to different chemical fields such as spices, solvents, lubricants, plasticizers and the like. The ethyl lactate is colorless and slightly odorous liquid, naturally exists in fruits such as pineapples, oranges, apples and the like, has good solubility, is miscible with water, and can be dissolved in alcohol, aromatic hydrocarbon, ester, hydrocarbon and oil. According to the reports of the U.S. department of energy, more than 80% of conventional solvents (especially halogenated hydrocarbons) will be replaced by ethyl lactate in the world in the future, and the production method has high energy consumption and high cost, so that the wide application in industry is limited, and the development of energy-saving, low-cost and environment-friendly ethyl lactate production method is urgent.
At present, the traditional process for producing ethyl lactate mainly adopts lactic acid and ethanol as raw materials, firstly generates ethyl lactate through catalytic reaction, and then purifies the ethyl lactate in the reaction product and recovers unreacted raw materials through rectification or flash separation procedures after the reaction is finished. The traditional production has the problems of longer process route, higher investment cost and the like, so the reactive distillation process is generated successively, the catalytic reaction and the distillation separation are integrated in the same equipment, the cost is reduced, in order to improve the conversion rate of the reaction, the excessive ethanol and water are adopted to form an azeotrope to be extracted from the top of the tower to promote the forward reaction, and the residual ethanol is recycled by the distillation mode. The ethanol residue in the process results in long subsequent separation flow, high energy consumption for separating the ethanol and water azeotrope and low yield of ethyl lactate. Patents and literature on ethyl lactate reaction processes are reported below:
patent CN100427453C proposes a new process for synthesizing ethyl lactate by a catalytic distillation method, lactic acid and ethanol react in a catalytic section of a catalytic distillation tower filled with a strong acid ion exchange resin catalyst to generate ethyl lactate, and tower bottoms are subjected to impurity removal by a flash tower to obtain an ethyl lactate product. According to the method, the molar ratio of ethanol to lactic acid is 3: 1-5: 1, the temperature of a reboiler at a tower kettle is 80-90 ℃, so that the tower kettle liquid still contains water and unreacted ethanol, the separation of the water and the ethanol from ethyl lactate is not realized, and the yield of subsequent separation products is reduced.
Patent CN1110698340A provides a process method for producing ethyl lactate by utilizing a reactive distillation dividing wall tower technology, wherein the whole tower is divided into seven areas, a whole tower rectifying section, a middle section feeding side reaction section, a middle section feeding side stripping section, a middle section extraction side rectifying section, a middle section extraction side stripping section and a tower kettle are arranged, ethyl lactate and water are generated in the middle section feeding side reaction section, the middle section extraction side rectifying section completes the separation of ethanol and esterified product water, products are purified in the two stripping sections of the feeding side and the extraction side, and ethyl lactate products are obtained at the bottom of the tower. The tower has more areas and more complex design, the molar ratio of fresh ethanol to lactic acid is 1.05-1.3: 1, and the energy consumption for separating the ethanol from the water azeotrope is higher.
Patent CN109438228A proposes that energy consumption is reduced by using reaction-pervaporation membrane-distillation technology, product quality is guaranteed, and lactic acid and ethyl acetateAlcohol in concentrated H2SO4The method is characterized in that a catalyst is heated and pressurized under a stirring state to esterify and synthesize ethyl lactate, mixed steam of ethanol, water and a small amount of ethyl lactate output by an esterification reaction is fractionated by a fractionating tower, the mixed steam of the ethanol and the water is input into a pervaporation membrane to carry out water separation, and the separated ethanol steam is output from the pervaporation membrane to continuously participate in the reaction. After the esterification reaction is finished, sodium carbonate is added to neutralize concentrated H2SO4And cooling the esterification liquid and then carrying out reduced pressure distillation to obtain the ethyl lactate product. The catalyst is concentrated H2SO4Side reactions are easy to occur, the product yield is reduced, more three wastes are generated, the recycling is difficult, the process flow is complex, and the investment and operation cost is high.
Patent CN107032984A discloses a continuous ethyl lactate synthesis method, which comprises two working sections of reaction and separation, wherein the molar ratio of ethanol to lactic acid is 2: 1-4: 1, the raw material is pumped into a fixed bed reactor to perform catalytic esterification reaction to obtain an ethyl lactate crude product, and then the ethyl lactate crude product sequentially enters a rough separation tower, an ethanol tower, a lactic acid tower and an ethyl lactate tower to obtain food-grade ethyl lactate. The method has the advantages of longer process flow, higher equipment investment and operation cost, azeotropic formation of ethanol and water, and higher recovery energy consumption caused by excessive ethanol.
J.Gao, X.M.ZHao, L.Y.ZHou, Z.H.Huang, invasion of Ethyl Lactate Reactive Distillation Process, Chemical Engineering Research and Design,2007,85(4):525 and 529. Synthesis of Ethyl Lactate by catalytic Reactive Distillation technique with ultra-fine magnetic solid super acid SO4 2-/ZrO2–Fe3O4The method for simulating and experimentally comparing the catalyst is used for verifying the feasibility of producing ethyl lactate by a reactive distillation method, water and ethanol are extracted from the top of the tower in an azeotrope form, and the product ethyl lactate is obtained from the bottom of the tower. The yield of the ethyl lactate is improved by 82 percent compared with that of a simple esterification reactor, but the conversion rate of raw materials and the yield of products are still lower.
In order to further reduce energy consumption, improve product yield and reduce cost, the feeding molar ratio is 1:1, reactants are utilized to the maximum extent, and the significance of saving energy is great by adopting high-efficiency energy-saving ethyl lactate to produce ethyl lactate through reaction and rectification.
Disclosure of Invention
The invention aims to provide a reactive distillation method and a device suitable for efficient and energy-saving production of ethyl lactate.
The invention relates to a high-efficiency energy-saving ethyl lactate reaction rectification production method and a device, wherein a lactic acid feed port is arranged at the top of a reaction section of a reaction rectification tower, an ethanol feed port is arranged at the bottom of the reaction section of the reaction rectification tower, product water is discharged from the top of the reaction rectification tower, a high-purity ethyl lactate product is obtained at the top of a product refining tower, lactic acid is extracted from a tower kettle and circulated to the reaction rectification tower, and the lactic acid is taken as a raw material to be converged with a fresh raw material and then returned to the reaction rectification tower.
The method and the device are characterized in that a structure-activity relationship between a catalytic filler structure and catalytic performance, matching of reaction and separation, optimization of theoretical plate number and retention time are studied in detail through a method combining experiments and numerical simulation, the initial feeding molar ratio of lactic acid to ethanol is 2-4: 1, lactic acid and product ethyl lactate which are not completely reacted are separated through a product refining process through the design of a reaction rectification process, the recovery and circulation of reactant lactic acid to a reaction rectification area are realized, the molar ratio of lactic acid to ethanol is increased in the reaction area, the complete reaction is realized under the condition that the steady feeding molar ratio of lactic acid to ethanol is 1:1, and the problem of azeotropic separation of the ethanol and product water which are not completely reacted is solved. Further, the reaction rectifying tower and the product refining tower are thermally coupled and integrated, so that the aim of saving energy is fulfilled.
The technology of the invention is as follows:
the high-efficiency energy-saving ethyl lactate reaction rectification production method comprises the following steps: production raw materials of lactic acid and ethanol respectively enter a reaction rectification zone from the top and the bottom of a reaction section, and the product water and ethyl lactate are rapidly moved out of the reaction rectification zone while esterification is carried out in a catalytic separation inner member of the reaction rectification zone, so that reactant ethanol is completely converted; the unreacted lactic acid and the product ethyl lactate are separated by a product refining process, so that the reactant lactic acid is recycled to the reaction rectification zone, and the molar ratio of the lactic acid to the ethanol in the reaction rectification zone is ensured to be at a higher value; and finally discharging the water product from the top of the reactive distillation tower, and obtaining a high-purity ethyl lactate product at the top of the product refining unit tower.
The operating process conditions of the high-efficiency energy-saving ethyl lactate reaction rectification production method are as follows:
the operating pressure of the reactive distillation process is 40-101 kPa; the reflux ratio of the reactive distillation process is 1-10.
The operating pressure of the product refining process is 100 Pa-5 kPa; the reflux ratio is 0.5 to 3.
The residence time of each theoretical stage of reaction materials in the reaction zone is 20-70 seconds.
The catalyst loading on each theoretical plate of the reaction rectification zone is 0.1-0.6 cm3Catalyst/cm3A catalytic filler.
The feeding molar ratio of the initial lactic acid to the ethanol is 2-4: 1, when the process reaches a stable state, the lactic acid which is not completely reacted circulates in the reaction rectifying tower, the stable feeding molar ratio of the lactic acid to the ethanol is 1:1, and the molar ratio of the reactant lactic acid to the ethanol in the reaction rectifying zone is 2-4: 1.
The device for realizing the high-efficiency energy-saving ethyl lactate reaction rectification production method can be independently realized by a reaction rectification tower and a product refining tower or a reaction rectification completely thermally coupled partition wall tower.
The production device of the high-efficiency energy-saving ethyl lactate reaction rectification production device can consist of a reaction rectification tower (3) and a product refining tower (17); the reactive distillation tower (3) consists of a reactive distillation tower rectifying section (4), a reactive distillation tower reaction section (5) and a reactive distillation tower stripping section (6); the product refining tower (17) consists of a product refining tower rectifying section (18) and a product refining tower stripping section (19). The two-tower device comprises a reaction rectifying tower (3), a product refining tower (17), a tower top water condenser (8), a tower top ethyl lactate condenser (21), a tower bottom crude product reboiler (14), a tower bottom lactic acid reboiler (27), related feeding pipelines and pipelines for connecting the devices; a fresh lactic acid (1) feeding pipeline is connected to the top of a reaction section (5) of a reaction rectifying tower (3), an ethanol (2) feeding pipeline is connected to the bottom of the reaction section (5) of the reaction rectifying tower (3), tower top steam (7) of the reaction rectifying tower (3) is connected with a gas phase inlet of a tower top water condenser (8) through a pipeline, a condensed liquid phase water (9) material extraction pipeline is connected with a liquid phase outlet of the tower top water condenser (8), meanwhile, one part of the liquid phase outlet of the tower top water condenser (8) is connected with the tower top of the reaction rectifying tower (3) through a pipeline (10), and the other part (11) is extracted for removed light components; the bottom of the reaction rectifying tower (3) is connected with the inlet of the product refining tower (17) through a crude product extraction (16) pipeline, the steam at the top of the product refining tower (17) is connected with the gas phase inlet of the ethyl lactate condenser (21) at the top of the tower through a pipeline (20), one part (23) of the condensed steam flows back to the top of the product refining tower (17), the other part (24) of the condensed steam is extracted from the top of the tower as a high-purity ethyl lactate product, and one part (29) of the liquid phase product at the bottom of the product refining tower (17) is extracted and returned to the top of the reaction section (5) of the reaction rectifying tower (3).
Wherein the reaction rectifying tower (3) consists of a rectifying section (4) of the reaction rectifying tower, a reaction section (5) of the reaction rectifying tower and a stripping section (6) of the reaction rectifying tower, internal parts of the rectifying section and the stripping section are both fillers or trays, and the internal parts of the reaction section are regular load molecular sieve type catalytic separation internal components or catalytic fillers or a combination form of the regular load molecular sieve type catalytic separation internal components or the catalytic fillers; the product refining tower (17) consists of a product refining tower rectifying section (18) and a product refining tower stripping section (19), and all the tower internals are fillers or trays. The number of tower plates of the reactive distillation tower is 20-50, wherein the number of tower plates of the distillation section is 5-15, the number of tower plates of the reaction section is 10-40, and the number of tower plates of the stripping section is 2-15; the number of tower plates of the product refining tower is 10-20, wherein the number of tower plates of the rectifying section is 5-9, and the number of tower plates of the stripping section is 7-15. The reaction rectification complete thermal coupling partition wall tower (30) is divided into five areas, which are a main tower rectification section (31), a main tower reaction section (32), a main tower stripping section (33), an auxiliary tower rectification section (34) and an auxiliary tower stripping section (35), the middle part of the tower is provided with a partition plate, the upper part of the tower is sealed, the tower body is divided into a main tower and an auxiliary tower, the reaction area is positioned in the main tower, the product refining area is positioned in the auxiliary tower, the tower needs two condensers, namely a tower top water condenser (8), a tower top ethyl lactate condenser (21) and a tower bottom lactic acid reboiler (27).
The production device of the high-efficiency energy-saving ethyl lactate reaction rectification production device is independently realized by a reaction rectification complete thermal coupling bulkhead tower (30), and the reaction rectification complete thermal coupling bulkhead tower (30) consists of a main tower rectification section (31), a main tower reaction section (32), a main tower stripping section (33), an auxiliary tower rectification section (34) and an auxiliary tower stripping section (35). The tower device comprises a reaction rectification fully thermally coupled bulkhead tower (30), an overhead water condenser (8), an overhead ethyl lactate condenser (21), a tower bottom lactic acid reboiler (27), related feed pipelines and pipelines for connecting the devices; a fresh lactic acid (1) feeding pipeline is connected to the top of a reaction section (32) of a reaction rectification complete thermal coupling bulkhead tower (30), a fresh ethanol (2) feeding pipeline is connected to the bottom of the reaction section (32) of the reaction rectification complete thermal coupling bulkhead tower (30), steam (7) at the top of a main tower of the reaction rectification complete thermal coupling bulkhead tower (30) is connected with a gas phase inlet of a tower top water condenser (8) through a pipeline, a material extraction pipeline (9) is connected with a liquid phase outlet of the tower top water condenser (8), meanwhile, one part of the liquid phase outlet of the tower top water condenser (8) is connected with the top of the main tower of the reaction rectification complete thermal coupling bulkhead tower (30) through a pipeline (10), and the other part (11) is discharged for removed light components; the gas phase ethyl lactate (20) at the top of the auxiliary tower of the reactive distillation complete thermal coupling partition tower (30) is connected with a gas phase inlet of an ethyl lactate condenser (21) at the top of the tower through a pipeline, a material extraction pipeline (22) is connected with a liquid phase outlet of the ethyl lactate condenser (21) at the top of the tower, meanwhile, one part of the liquid phase outlet of the ethyl lactate condenser (21) at the top of the tower is connected with the top of the auxiliary tower of the reactive distillation complete thermal coupling partition tower (30) through a pipeline (23), and the other part (24) is extracted from the top of the tower as a high-purity; the liquid in the bottom of the reaction rectification complete thermal coupling bulkhead tower (30) is connected with the liquid phase inlet of a tower bottom lactic acid reboiler (27) through a pipeline (26), meanwhile, the gas phase outlet of the tower bottom lactic acid reboiler (27) is also connected with the tower bottom of the reaction rectification complete thermal coupling bulkhead tower (30) through a pipeline (28), and the other part of material (29) is taken as a raw material, taken out and converged with a fresh raw material (1) and then returned to the top of the reaction section (32) of the reaction rectification complete thermal coupling bulkhead tower (30).
The reaction rectification complete thermal coupling bulkhead column (30) is divided into five areas, namely a main column rectification section (31), a main column reaction section (32), a main column stripping section (33), an auxiliary column rectification section (34) and an auxiliary column stripping section (35), wherein the middle part of the column is provided with a baffle, the upper part of the baffle is sealed, the column body is divided into a main column and an auxiliary column, the reaction area is positioned in the main column, the product refining area is positioned in the auxiliary column, and the column needs two condensers which are respectively a column top water condenser (8), a column top ethyl lactate condenser (21) and a column bottom lactic acid reboiler (27); the internal parts of the main tower rectifying section (31), the main tower stripping section (33), the auxiliary tower rectifying section (34) and the auxiliary tower stripping section (35) are all packing or trays, and the internal parts of the main tower reaction section (32) are regular load molecular sieve type catalytic separation internal components or catalytic packing or a combination form of the regular load molecular sieve type catalytic separation internal components or the catalytic packing; the internal parts of the main tower rectifying section (31), the main tower stripping section (33), the auxiliary tower rectifying section (34) and the auxiliary tower stripping section (35) are all packing or trays, and the internal parts of the main tower reaction section (32) are regular load molecular sieve type catalytic separation internal components or catalytic packing or a combination form of the regular load molecular sieve type catalytic separation internal components or the catalytic packing. The total number of the tower plates of the reaction distillation complete thermal coupling dividing wall tower is 40-80, wherein the number of the tower plates of the distillation section of the main tower is 5-10, the number of the tower plates of the reaction section of the main tower is 10-40, the number of the tower plates of the stripping section of the main tower is 5-13, the number of the tower plates of the distillation section of the auxiliary tower is 10-20, and the number of the tower plates of the stripping section of the auxiliary tower is 10-15.
The high-efficiency energy-saving ethyl lactate reaction rectification production device is characterized in that: the production raw material lactic acid pipeline is connected to the upper part of the reaction section, the production raw material ethanol pipeline is connected to the bottom of the reaction section, the top of the product refining tower is provided with an extracted ethyl lactate pipeline, the bottom of the product refining tower is provided with an extracted circulating lactic acid pipeline, and the circulating lactic acid pipeline is connected with the production raw material lactic acid pipeline.
The invention relates to a method and a device for producing ethyl lactate by using an efficient energy-saving reaction rectification technology. Lactic acid and ethanol enter a product refining unit after the reaction and rectification process, so that a high-purity ethyl lactate product is obtained, and the lactic acid is extracted from a tower kettle and circulated to the reaction and rectification unit. The invention has the advantages that the quality purity of the product can reach more than 99 percent, and the yield can reach more than 98 percent. The reaction rectifying tower and the product refining tower are coupled and integrated by a complete thermal coupling method, so that the production energy consumption is saved by more than 30%, and the equipment investment cost is saved.
Drawings
FIG. 1 is a schematic diagram of a process flow of high-efficiency energy-saving ethyl lactate reaction rectification production, which consists of a reaction rectification tower (3) and a product refining tower (17).
FIG. 2 is a schematic diagram of the process flow of the high-efficiency energy-saving ethyl lactate reaction distillation production, which consists of a reaction distillation complete thermal coupling bulkhead tower (30).
Wherein: 1-lactic acid; 2-ethanol; 3-a reactive distillation column; 4-a rectifying section of a reactive rectifying tower; 5-reaction section of reaction rectifying tower; 6-stripping section of reactive distillation column; 7-gas phase water; 8-tower top water condenser; 9-liquid phase water; 10-refluxing water; 11-distilling off water; 12-crude product at the bottom of the tower; 13-returning the crude product to the tower; 14-bottom crude product reboiler; 15-returning to the tower to obtain a gas-phase crude product; 16-extracting a crude product; 17-a product refining column; 18-a rectification section of a product refining tower; 19-a stripping section of a product refining tower; 20-gas phase ethyl lactate; 21-overhead ethyl lactate condenser; 22-liquid phase ethyl lactate; 23-refluxing ethyl lactate; 24-high purity ethyl lactate; 25-liquid phase lactic acid at the bottom of the tower; 26-reflux liquid phase lactic acid; 27-bottom lactic acid reboiler; 28-refluxing the column with the gas phase lactic acid; 29-recycle lactic acid; 30-reactive distillation fully thermally coupled dividing wall column; 31-a main column rectification section; 32-a main column reaction section; 33-main column stripping section; 34-a rectifying section of a side column; 35-side column stripping section.
Detailed Description
The method and the device provided by the invention are further explained in the following with the attached drawings.
The invention is realized by the following technical scheme:
as shown in figure 1, fresh lactic acid (1) is fed from the top of a reaction section (5) in a reaction rectifying tower (3), fresh ethanol (2) is fed from the bottom of the reaction section (5) in the reaction rectifying tower (3), liquid-phase lactic acid and ethanol steam entering the tower carry out esterification reaction in the reaction section (5), generated water enters a tower top water condenser (8) from a tower top gas phase outlet (7) of the reaction rectifying tower (3) for condensation, the condensed material flows out from a tower top water condenser (8) liquid phase outlet, one part of liquid-phase water (9) flows into the reaction rectifying tower (3) as tower top reflux water (10), the other part of fractionated effluent water (11) is discharged as removed light components, unreacted lactic acid and generated ethyl lactate enter a crude product reboiler (14) from a tower bottom liquid phase outlet (12) of the reaction rectifying tower (3) and one part (13), the other part is taken as a crude product to be extracted (16), the liquid phase material (16) extracted from the tower bottom of the reaction rectifying tower (3) enters a product refining tower (17), a gas phase product (20) at the tower top of the product refining tower (17) is condensed by a tower top ethyl lactate condenser (21) and then flows out, one part of the liquid phase ethyl lactate (22) is taken as tower top reflux ethyl lactate (23) and returns to the tower top of the product refining tower (17), the other part of high purity ethyl lactate (24) is taken as a product to be extracted, one part (26) of the liquid phase lactic acid (25) at the tower bottom returns to the tower bottom of the product refining tower (17) through a tower bottom lactic acid reboiler (27), and the other part of the material (29) is taken as a raw material and is converged with the fresh raw material (1) and then returns to the top.
As shown in fig. 2, fresh lactic acid (1) is fed from the top of a reaction section (32) in a reaction rectification complete thermal coupling bulkhead column (30), fresh ethanol (2) is fed from the bottom of the reaction section (2) in the reaction rectification complete thermal coupling bulkhead column (30), liquid-phase lactic acid and ethanol vapor entering the column are subjected to esterification reaction in the reaction section (2), generated water enters a column top water condenser (8) from a column top gas phase outlet (7) of a main column of the reaction rectification complete thermal coupling bulkhead column (30) for condensation, the condensed material flows out from a liquid phase outlet of the column top water condenser (8), a part of liquid-phase water (9) flows into the main column of the reaction rectification complete thermal coupling bulkhead column (30) as column top reflux water (10), and the other part of fractionated effluent (11) is discharged as a removed light component; the product ethyl lactate enters an ethyl lactate condenser (21) at the top of the tower from a gas phase outlet (20) at the top of the auxiliary tower of the reactive distillation complete thermal coupling partition tower (30) for condensation, the condensed material flows out from a liquid phase outlet of the ethyl lactate condenser (21) at the top of the tower, one part of the liquid phase ethyl lactate (22) flows into the auxiliary tower of the reactive distillation complete thermal coupling partition tower (30) as reflux ethyl lactate (23) at the top of the tower, and the other part of high-purity ethyl lactate (24) is taken as the product ethyl lactate and is extracted from the top of the auxiliary tower of the reactive distillation complete thermal coupling partition tower (30); one part of material (26) of liquid phase lactic acid (25) at the bottom of the reactive distillation complete thermal coupling bulkhead tower (30) returns to the bottom of the reactive distillation complete thermal coupling bulkhead tower (30) through a tower bottom lactic acid reboiler (27), and the other part of material (29) is collected as a raw material and is merged with a fresh raw material (1) and then returns to the top of a reaction section (32) of the reactive distillation complete thermal coupling bulkhead tower (30).
The operating process conditions of the high-efficiency energy-saving ethyl lactate reaction rectification production method are as follows: the operating pressure of the reactive distillation process is 40-101 kPa; the reflux ratio of the reactive distillation process is 1-10. The operating pressure of the product refining process is 100 Pa-5 kPa; the reflux ratio is 0.5 to 3. The residence time of each theoretical stage of reaction materials in the reaction zone is 20-70 seconds. The molar ratio of the reactant lactic acid to the ethanol in the reaction rectification zone is 2-4: 1.
If the device consists of two towers, namely a reaction rectifying tower (3) and a product rectifying tower (17), the reaction rectifying tower (3) consists of a reaction rectifying tower rectifying section (4), a reaction rectifying tower reaction section (5) and a reaction rectifying tower stripping section (6); the product refining tower (17) consists of a product refining tower rectifying section (18) and a product refining tower stripping section (19). The two-tower device comprises a reaction rectifying tower (3), a product refining tower (21), an overhead water condenser (8), an overhead ethyl lactate condenser (25), a tower bottom crude product reboiler (14), a tower bottom lactic acid reboiler (27), related feeding pipelines and pipelines for connecting the devices; a fresh lactic acid (1) feeding pipeline is connected to the top of a reaction section (5) of a reaction rectifying tower (3), an ethanol (2) feeding pipeline is connected to the bottom of the reaction section (5) of the reaction rectifying tower (3), gas phase water (7) at the top of the reaction rectifying tower (3) is connected with a gas phase inlet of a tower top water condenser (8) through a pipeline, a liquid phase water (9) material pipeline is connected with a liquid phase outlet of the tower top water condenser (8), meanwhile, one part of the liquid phase outlet of the tower top water condenser (8) is connected with the top of the reaction rectifying tower (3) through a pipeline (10), and the other part (11) is extracted for removed light components. The bottom of the reaction rectifying tower (3) is connected with the inlet of the product refining tower (17) through a crude product extraction (16) pipeline, the steam at the top of the product refining tower (17) is connected with the gas phase inlet of the ethyl lactate condenser (21) at the top of the tower through a pipeline (20), one part (23) of the condensed steam flows back to the top of the product refining tower (17), the other part (24) of the condensed steam is extracted from the top of the tower as a high-purity ethyl lactate product, and one part (29) of the liquid phase product at the bottom of the product refining tower (17) is extracted and returned to the top of the reaction section (5) of the reaction rectifying tower (3).
If the device is realized by a reaction rectification complete thermal coupling bulkhead column (30) and a column independently, the reaction rectification complete thermal coupling bulkhead column (30) consists of a main column rectification section (31), a main column reaction section (32), a main column stripping section (33), an auxiliary column rectification section (34) and an auxiliary column stripping section (35). The tower device comprises a reaction rectification fully thermally coupled bulkhead tower (30), an overhead water condenser (8), an overhead ethyl lactate condenser (25), a tower bottom lactic acid reboiler (27), related feed pipelines and pipelines for connecting the devices; a fresh lactic acid (1) feeding pipeline is connected to the top of a reaction section (32) of a reaction rectification complete thermal coupling bulkhead tower (30), a fresh ethanol (2) feeding pipeline is connected to the bottom of the reaction section (32) of the reaction rectification complete thermal coupling bulkhead tower (30), gas phase water (7) at the top of a main tower of the reaction rectification complete thermal coupling bulkhead tower (30) is connected with a gas phase inlet of a tower top water condenser (8) through a pipeline, a liquid phase water (9) material pipeline is connected with a liquid phase outlet of the tower top water condenser (8), meanwhile, one part of the liquid phase outlet of the tower top water condenser (8) is connected with the top of the main tower of the reaction rectification complete thermal coupling bulkhead tower (30) through a pipeline (10), and the other part (11) is discharged for removed light components. The gas phase ethyl lactate (20) at the top of the auxiliary tower of the reactive distillation complete thermal coupling partition tower (30) is connected with a gas phase inlet of an ethyl lactate condenser (21) at the top of the tower through a pipeline, a material pipeline of liquid phase ethyl lactate (22) is connected with a liquid phase outlet of the ethyl lactate condenser (21) at the top of the tower, meanwhile, one part of the liquid phase outlet of the ethyl lactate condenser (21) at the top of the tower is connected with the top of the auxiliary tower of the reactive distillation complete thermal coupling partition tower (30) through a pipeline (23), and the other part (24) is taken as a high-purity ethyl lactate product. The liquid in the bottom of the reaction rectification complete thermal coupling bulkhead tower (30) is connected with the liquid phase inlet of a tower bottom lactic acid reboiler (27) through a pipeline (26), meanwhile, the gas phase outlet of the tower bottom lactic acid reboiler (27) is also connected with the tower bottom of the reaction rectification complete thermal coupling bulkhead tower (30) through a pipeline (28), and the other part of material (29) is taken as a raw material, taken out and converged with a fresh raw material (1) and then returned to the top of the reaction section (32) of the reaction rectification complete thermal coupling bulkhead tower (30).
The high-efficiency energy-saving ethyl lactate reaction rectification production device is characterized in that: the production raw material lactic acid pipeline is connected to the upper part of the reaction section, the production raw material ethanol pipeline is connected to the bottom of the reaction section, the top of the product refining tower is provided with an extracted ethyl lactate pipeline, the bottom of the product refining tower is provided with an extracted circulating lactic acid pipeline, and the circulating lactic acid pipeline is connected with the production raw material lactic acid pipeline.
As shown in fig. 1, the reactive distillation column (3) is applied to examples 1 and 2, and comprises a rectifying section (4) of the reactive distillation column, a reaction section (5) of the reactive distillation column, and a stripping section (6) of the reactive distillation column, wherein internals of the rectifying section and the stripping section are both packing or trays, and internals of the reaction section are regular-load molecular sieve type catalytic separation internals or catalytic packing or a combination form of the regular-load molecular sieve type catalytic separation internals or the catalytic packing; the product refining tower (17) consists of a product refining tower rectifying section (18) and a product refining tower stripping section (19), and all the tower internals are fillers or trays. The number of tower plates of the reactive distillation tower is 20-50, wherein the number of tower plates of the distillation section is 5-15, the number of tower plates of the reaction section is 10-40, and the number of tower plates of the stripping section is 2-15; the number of tower plates of the product refining tower is 10-20, wherein the number of tower plates of the rectifying section is 5-9, and the number of tower plates of the stripping section is 7-15. Or as shown in fig. 2, applied to examples 3 and 4, the reactive distillation fully thermally coupled dividing wall column (30) is divided into five regions, namely a main column rectifying section (31), a main column reaction section (32), a main column stripping section (33), an auxiliary column rectifying section (34) and an auxiliary column stripping section (35), the middle part of the column is provided with a dividing wall, the upper part of the dividing wall is sealed, the column body is divided into a main column and an auxiliary column, the reaction section is positioned in the main column, the product refining section is positioned in the auxiliary column, and the column needs two condensers, namely a top water condenser (8), a top ethyl lactate condenser (21) and a bottom lactic acid reboiler (27). The internal parts of the main tower rectifying section (31), the main tower stripping section (33), the auxiliary tower rectifying section (34) and the auxiliary tower stripping section (35) are all packing or trays, and the internal parts of the main tower reaction section (32) are regular load molecular sieve type catalytic separation internal components or catalytic packing or a combination form of the regular load molecular sieve type catalytic separation internal components or the catalytic packing. The total number of the tower plates of the reaction distillation complete thermal coupling dividing wall tower is 40-80, wherein the number of the tower plates of the distillation section of the main tower is 5-10, the number of the tower plates of the reaction section of the main tower is 10-40, the number of the tower plates of the stripping section of the main tower is 5-13, the number of the tower plates of the distillation section of the auxiliary tower is 10-20, and the number of the tower plates of the stripping section of the auxiliary tower is 10-15. The catalyst loading on each theoretical plate of the reaction rectification zone is 0.1-0.6 cm3Catalyst/cm3A catalytic filler.
The technology and equipment of the invention are widely applied to the process of preparing ethyl lactate by esterifying lactic acid and ethanol, and in order to better illustrate the advantages of the invention in terms of product purity and yield, the invention is compared with the process described in patent CN 100427453C. Four of these examples of applications were chosen for illustration, but are not intended to limit the scope of applicability of the present techniques and apparatus.
Example 1
The method is used for the process of preparing ethyl lactate by esterifying lactic acid and ethanol, is the same as the process of the invention, and comprises a reaction rectifying tower, a product refining tower, a tower top water condenser, a tower top ethyl lactate condenser, a tower bottom crude product reboiler and a tower bottom lactic acid reboiler, wherein the operating pressure of the reaction rectifying tower is 101kPa, the reflux ratio is 9, the feeding amount of fresh lactic acid is 50kmol/h, the reaction molar ratio of biomass-based lactic acid to ethanol is 2, and the loading amount of a catalyst is 0.1cm3Catalyst/cm3The operation pressure of the catalytic filler and the product refining tower is 5kpa, and the reflux ratio is 0.5.
After the process, the purity of the main product ethyl lactate can reach 99%, the yield can reach 98.2%, and compared with the conventional reaction rectification process, the energy consumption can be reduced by more than 30%.
Example 2
The method is used for the process of preparing ethyl lactate by esterifying lactic acid and ethanol, is the same as the process of the invention, and comprises a reaction rectifying tower, a product refining tower, a tower top water condenser, a tower top ethyl lactate condenser, a tower bottom crude product reboiler and a tower bottom lactic acid reboiler, wherein the operating pressure of the reaction rectifying tower is 40kPa, the reflux ratio is 10, the feeding amount of fresh lactic acid is 15kmol/h, the reaction molar ratio of biomass-based lactic acid to ethanol is 3, and the loading amount of a catalyst is 0.1cm3Catalyst/cm3The catalytic packing, the operating pressure of the product refining tower is 100pa, and the reflux ratio is 1.
After the process, the purity of the main product ethyl lactate can reach 99.2%, the yield can reach 98.3%, and compared with the conventional reaction rectification process, the energy consumption can be reduced by more than 30%.
Example 3
The method is used for the process of preparing ethyl lactate by esterifying lactic acid and ethanol, is the same as the process of the invention, and comprises a reaction rectification complete thermal coupling bulkhead tower, a tower top water condenser, a tower top ethyl lactate condenser and a tower bottom lactic acid reboiler, wherein the operation pressure of the reaction rectification complete thermal coupling bulkhead tower is 50kPa, the reflux ratio of a main tower is 2, the reflux ratio of an auxiliary tower is 3, the feeding amount of fresh lactic acid is 30kmol/h, the reaction molar ratio of biomass-based lactic acid and ethanol is 4, and the loading amount of a catalyst is 0.1cm3Catalyst/cm3A catalytic filler.
After the process, the purity of the main product ethyl lactate can reach 99.7%, the yield can reach 98.6%, and compared with the conventional reaction rectification process, the energy consumption can be reduced by more than 40%.
Example 4
The method is used for the process of preparing ethyl lactate by esterifying lactic acid and ethanol, is the same as the process of the invention, and comprises a reaction rectification complete thermal coupling bulkhead tower, a tower top water condenser, a tower top ethyl lactate condenser and a tower bottom lactic acid reboiler, wherein the operation pressure of the reaction rectification complete thermal coupling bulkhead tower is 40kPa, the reflux ratio of a main tower is 1.5, the reflux ratio of an auxiliary tower is 2.5, the feeding amount of fresh lactic acid is 15kmol/h, the reaction molar ratio of biomass-based lactic acid and ethanol is 3, and the loading amount of a catalyst is 0.1cm3Catalyst/cm3A catalytic filler.
After the process, the purity of the main product ethyl lactate can reach 99.3%, the yield can reach 98.2%, and compared with the conventional reaction rectification process, the energy consumption can be reduced by more than 30%.
The efficient and energy-saving ethyl lactate reaction rectification production method and device provided by the invention have been described through the preferred embodiments, and it is obvious for related technical personnel to change or properly change and compose the equipment and the process flow described herein to realize the technology of the invention without departing from the content, the spirit and the scope of the invention. It is expressly intended that all such similar substitutes and modifications apparent to those skilled in the art are deemed to be within the spirit, scope and content of the invention.
Claims (10)
1. A high-efficiency energy-saving ethyl lactate reaction rectification production method; the method is characterized in that raw materials of lactic acid and ethanol respectively enter a reaction rectification zone from the top and the bottom of a reaction section, and product water and ethyl lactate are moved out of the reaction rectification zone while esterification is carried out under catalysis of the reaction rectification zone, so that reactant ethanol is completely converted; the unreacted lactic acid and the product ethyl lactate are separated by a product refining process, so that the reactant lactic acid is recycled to the reaction rectification zone, and the molar ratio of the lactic acid to the ethanol in the reaction rectification zone is ensured to be at a higher value; and finally discharging the water product from the top of the reactive distillation tower, and obtaining a high-purity ethyl lactate product at the top of the product refining unit tower.
2. The method as set forth in claim 1, wherein the reactive distillation process is operated at a pressure of 40 to 101 kPa; the reflux ratio of the reactive distillation process is 1-10; the operating pressure of the product refining process is 100 Pa-5 kPa; the reflux ratio is 0.5 to 3.
3. The process of claim 1, wherein the residence time of the reaction mass in each theoretical stage of the reaction zone is 20 to 70 seconds; the catalyst loading on each theoretical plate of the reaction rectification zone is 0.1-0.6 cm3Catalyst/cm3A catalytic filler.
4. The method as set forth in claim 1, characterized in that the feeding molar ratio of the initial lactic acid to the ethanol is 2-4: 1, when the process reaches a steady state, the lactic acid which is not completely reacted circulates in the reactive distillation column to realize the steady feeding molar ratio of the lactic acid to the ethanol of 1:1, and the molar ratio of the reactant lactic acid to the ethanol in the reactive distillation zone is 2-4: 1.
5. The high-efficiency energy-saving ethyl lactate reaction rectification production device is characterized in that the production device consists of a reaction rectification tower (3) and a product refining tower (17); the reactive distillation tower (3) consists of a reactive distillation tower rectifying section (4), a reactive distillation tower reaction section (5) and a reactive distillation tower stripping section (6); the product refining tower (17) consists of a product refining tower rectifying section (18) and a product refining tower stripping section (19); the two-tower device comprises a reaction rectifying tower (3), a product refining tower (17), a tower top water condenser (8), a tower top ethyl lactate condenser (21), a tower bottom crude product reboiler (14), a tower bottom lactic acid reboiler (27), related feeding pipelines and pipelines for connecting the devices; a fresh lactic acid (1) feeding pipeline is connected to the top of a reaction section (5) of a reaction rectifying tower (3), an ethanol (2) feeding pipeline is connected to the bottom of the reaction section (5) of the reaction rectifying tower (3), tower top steam (7) of the reaction rectifying tower (3) is connected with a gas phase inlet of a tower top water condenser (8) through a pipeline, a condensed liquid phase water (9) material extraction pipeline is connected with a liquid phase outlet of the tower top water condenser (8), meanwhile, one part of the liquid phase outlet of the tower top water condenser (8) is connected with the tower top of the reaction rectifying tower (3) through a pipeline (10), and the other part (11) is extracted for removed light components; the bottom of the reaction rectifying tower (3) is connected with the inlet of the product refining tower (17) through a crude product extraction (16) pipeline, the steam at the top of the product refining tower (17) is connected with the gas phase inlet of the ethyl lactate condenser (21) at the top of the tower through a pipeline (20), one part (23) of the condensed steam flows back to the top of the product refining tower (17), the other part (24) of the condensed steam is extracted from the top of the tower as a high-purity ethyl lactate product, and one part (29) of the liquid phase product at the bottom of the product refining tower (17) is extracted and returned to the top of the reaction section (5) of the reaction rectifying tower (3).
6. The device as claimed in claim 5, characterized in that the reactive distillation column (3) consists of a rectifying section (4) of the reactive distillation column, a reaction section (5) of the reactive distillation column and a stripping section (6) of the reactive distillation column, the internals of the rectifying section and the stripping section are all packing or trays, and the internals of the reaction section are regular-load molecular sieve type catalytic separation internals or catalytic packing or a combination thereof; the product refining tower (17) consists of a product refining tower rectifying section (18) and a product refining tower stripping section (19), and all the tower internals are fillers or trays.
7. The apparatus as claimed in claim 5, wherein the number of reaction-rectification column plates is 20 to 50, wherein the number of rectification stage plates is 5 to 15, the number of reaction stage plates is 10 to 40, and the number of stripping stage plates is 2 to 15; the number of tower plates of the product refining tower is 10-20, wherein the number of tower plates of the rectifying section is 5-9, and the number of tower plates of the stripping section is 7-15.
8. The high-efficiency energy-saving ethyl lactate reaction rectification production device is characterized in that the production device is independently realized by a reaction rectification complete thermal coupling bulkhead tower (30), and the reaction rectification complete thermal coupling bulkhead tower (30) consists of a main tower rectification section (31), a main tower reaction section (32), a main tower stripping section (33), an auxiliary tower rectification section (34) and an auxiliary tower stripping section (35); comprises a reaction rectification fully thermally coupled dividing wall column (30), an overhead water condenser (8), an overhead ethyl lactate condenser (21), a tower bottom lactic acid reboiler (27), related feed pipelines and pipelines for connecting the above devices; a fresh lactic acid (1) feeding pipeline is connected to the top of a reaction section (32) of a reaction rectification complete thermal coupling bulkhead tower (30), a fresh ethanol (2) feeding pipeline is connected to the bottom of the reaction section (32) of the reaction rectification complete thermal coupling bulkhead tower (30), steam (7) at the top of a main tower of the reaction rectification complete thermal coupling bulkhead tower (30) is connected with a gas phase inlet of a tower top water condenser (8) through a pipeline, a material extraction pipeline (9) is connected with a liquid phase outlet of the tower top water condenser (8), meanwhile, one part of the liquid phase outlet of the tower top water condenser (8) is connected with the top of the main tower of the reaction rectification complete thermal coupling bulkhead tower (30) through a pipeline (10), and the other part (11) is discharged for removed light components; the gas phase ethyl lactate (20) at the top of the auxiliary tower of the reactive distillation complete thermal coupling partition tower (30) is connected with a gas phase inlet of an ethyl lactate condenser (21) at the top of the tower through a pipeline, a material extraction pipeline (22) is connected with a liquid phase outlet of the ethyl lactate condenser (21) at the top of the tower, meanwhile, one part of the liquid phase outlet of the ethyl lactate condenser (21) at the top of the tower is connected with the top of the auxiliary tower of the reactive distillation complete thermal coupling partition tower (30) through a pipeline (23), and the other part (24) is extracted from the top of the tower as a high-purity; the liquid in the bottom of the reaction rectification complete thermal coupling bulkhead tower (30) is connected with the liquid phase inlet of a tower bottom lactic acid reboiler (27) through a pipeline (26), meanwhile, the gas phase outlet of the tower bottom lactic acid reboiler (27) is also connected with the tower bottom of the reaction rectification complete thermal coupling bulkhead tower (30) through a pipeline (28), and the other part of material (29) is taken as a raw material, taken out and converged with a fresh raw material (1) and then returned to the top of the reaction section (32) of the reaction rectification complete thermal coupling bulkhead tower (30).
9. The apparatus as claimed in claim 8, characterized in that the reactive distillation fully thermally coupled dividing wall column (30) is divided into five sections, namely a main column rectification section (31), a main column reaction section (32), a main column stripping section (33), an auxiliary column rectification section (34) and an auxiliary column stripping section (35), a dividing wall is arranged in the middle of the column, the upper part of the column is sealed, the column body is divided into a main column and an auxiliary column, the reaction section is located in the main column, the product refining section is located in the auxiliary column, and the column requires two condensers, namely an overhead water condenser (8), an overhead ethyl lactate condenser (21) and a bottom reboiler (27); the internal parts of the main tower rectifying section (31), the main tower stripping section (33), the auxiliary tower rectifying section (34) and the auxiliary tower stripping section (35) are all packing or trays, and the internal parts of the main tower reaction section (32) are regular load molecular sieve type catalytic separation internal components or catalytic packing or a combination form of the regular load molecular sieve type catalytic separation internal components or the catalytic packing.
10. The apparatus according to claim 8, wherein the total number of plates in the reactive distillation fully thermally coupled dividing wall column is 40 to 80, wherein the number of plates in the rectifying section of the main column is 5 to 10, the number of plates in the reaction section of the main column is 10 to 40, the number of plates in the stripping section of the main column is 5 to 13, the number of plates in the rectifying section of the sub-column is 10 to 20, and the number of plates in the stripping section of the sub-column is 10 to 15.
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