CN111943849B - Efficient energy-saving ethyl lactate reactive distillation production method and device - Google Patents
Efficient energy-saving ethyl lactate reactive distillation production method and device Download PDFInfo
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Abstract
The invention relates to a high-efficiency energy-saving ethyl lactate reactive distillation production method and a device, which consists of a reactive distillation tower and a product refining tower or a reactive distillation complete thermal coupling tower, wherein lactic acid and ethanol enter the reactive distillation tower from the top and the bottom of a reaction section, materials at the tower bottom enter the 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 bottom and circulated to the reactive distillation tower, and product water is discharged from the top of the reactive distillation tower. The invention realizes that the steady-state feeding mole ratio of lactic acid to ethanol is 1:1, increases the mole ratio of lactic acid to ethanol through the reaction rectification reaction zone, promotes the complete conversion of ethanol, and avoids the difficult problem of azeotropic separation of unreacted complete ethanol and product water. 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 simultaneously saving equipment investment cost.
Description
Technical Field
The invention relates to the technical field of organic solvent ethyl lactate synthesis in the chemical field, in particular to a high-efficiency energy-saving ethyl lactate reaction rectification production method and device; a method and a device for producing ethyl lactate by utilizing a reaction rectification technology under the lactic acid circulation condition with high efficiency and energy saving.
Background
Solvents are widely used in almost all production and process industries. The common solvent is mainly produced by taking nonrenewable petroleum as a raw material, a large amount of carbon dioxide and volatile organic pollutants (VOCs) can be released in the production process, and the ethyl lactate organic solvent can play a vital role in reducing carbon/pollution emission in China by replacing the traditional solvents (such as halogenated solvents, ethers solvents, fluorocarbon solvents and the like).
Ethyl lactate is also called alpha-hydroxy ethyl propionate, and the molecular formula is C 5 H 10 O 3 The solvent has a melting point of 26 ℃ and a boiling point of 154.5 ℃, is environment-friendly, has good biodegradability, and is widely applied to different chemical fields such as perfume, solvent, lubricant, plasticizer and the like. Ethyl lactate is colorless slightly odorous liquid, naturally exists in fruits such as pineapple, orange, apple, etc., has good solubility, is miscible with water, and can be miscible with alcohols, aromatic hydrocarbons, esters, hydrocarbons, and oils. According to the report of the United states department of energy, more than 80% of conventional solvents (particularly halogenated hydrocarbons) in the world in the future are replaced by ethyl lactate, and the production method of the ethyl lactate has high energy consumption and high cost and is limited to be widely applied in industry, so the development of an 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, the ethyl lactate is produced through catalytic reaction, and after the reaction is finished, the ethyl lactate in the reaction product is purified through a rectification or flash separation process, and unreacted raw materials are recovered. The traditional production has the problems of longer process route, higher investment cost and the like, so that the reactive distillation process is sequentially carried out, the catalytic reaction and the distillation separation are integrated into the same equipment, and the cost is reduced, but in order to improve the conversion rate of the reaction, excessive ethanol and water form an azeotrope to be extracted from the top of the tower, so that the forward progress of the reaction is promoted, and the residual ethanol is recycled in a distillation mode. The residual ethanol in the process leads to long subsequent separation flow, the separation energy consumption of the ethanol and water azeotrope is higher, and the yield of ethyl lactate is not high. The patents and literature relating to ethyl lactate reaction processes are reported as follows:
patent CN100427453C proposes a new technology for synthesizing ethyl lactate by catalytic distillation, wherein 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 impurities in tower bottom liquid are removed 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, and the temperature of a tower kettle reboiler is 80-90 ℃, so that water and unreacted ethanol are still contained in tower kettle liquid, separation of water, ethanol and ethyl lactate is not realized, and the yield of a product separated from the tower kettle liquid is reduced.
Patent CN1110698340a proposes a process for producing ethyl lactate by using a reactive distillation bulkhead column technique, wherein the whole column is divided into seven regions, a whole column rectifying section, a middle feeding side reacting section, a middle feeding side stripping section, a middle extraction side rectifying section, a middle extraction side stripping section and a column bottom, ethyl lactate and water are produced in the middle feeding side reacting section, the middle extraction side rectifying section is used for separating 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 column. 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 to utilize the reaction-pervaporation membrane-distillation technology to reduce energy consumption, ensure product quality and concentrate lactic acid and ethanol into H 2 SO 4 The catalyst is heated and pressurized under stirring to synthesize ethyl lactate, the mixed vapor of ethanol, water and small amount of ethyl lactate, which is output from the esterification reaction, is fractionated by a fractionating tower, the mixed vapor of ethanol and water is input into a pervaporation membrane for water separation, and the separated ethanol vapor is output from the pervaporation membrane to continuously participate in the reaction. After the esterification reaction is completed, sodium carbonate is added to neutralize concentrated H 2 SO 4 And cooling the esterified liquid, and performing reduced pressure distillation to obtain an ethyl lactate product. The catalyst is concentrated H 2 SO 4 Side 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 the operation cost are high.
Patent CN107032984A discloses a method for synthesizing continuous ethyl lactate, 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 materials are pumped into a fixed bed reactor for catalytic esterification reaction to obtain crude ethyl lactate, and then the crude ethyl lactate is sequentially fed into 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, investigation of Ethyl Lactate Reactive Distillation Process, chemical Engineering Research and Design,2007,85 (4): 525-529, synthesizing ethyl lactate by catalytic reaction distillation technique, and adding superfine magnetic solid super acid SO 4 2- /ZrO 2 –Fe 3 O 4 The feasibility of producing ethyl lactate by using a reaction rectification method is verified by using a method of comparing simulation with experiment as a catalyst, water and ethanol are extracted from the top of the tower in the form of azeotrope, and the ethyl lactate product is obtained from the bottom of the tower. The yield of ethyl lactate is 82% higher than 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, realize that the feeding mole ratio is 1:1, furthest utilize reactants, and realize that the efficient energy-saving ethyl lactate is used for producing the ethyl lactate by reaction and rectification has great significance in energy saving.
Disclosure of Invention
The invention aims at a reaction rectifying method and a device suitable for efficient energy-saving production of ethyl lactate, and the efficient energy-saving reaction rectifying method provided by the invention is used for producing ethyl lactate, and has the advantages of simple process flow, equipment investment cost saving, convenient operation, lower production energy consumption, very high purity and reaction conversion rate of the target product ethyl lactate, and the like.
The invention relates to a high-efficiency energy-saving ethyl lactate reactive distillation production method and a device, wherein a lactic acid feed inlet is arranged at the top of a reactive section of a reactive distillation tower, an ethanol feed inlet is arranged at the bottom of the reactive section of the reactive distillation tower, product water is discharged from the top of the reactive distillation tower, a high-purity ethyl lactate product is obtained from the top of the product refining tower, lactic acid is extracted from a tower kettle and circulated to the reactive distillation tower, and the lactic acid is returned to the reactive distillation tower after being used as a raw material and a fresh raw material are combined.
The method and the device are characterized in that the structure-activity relationship between the catalytic filler structure and the catalytic performance, the matching of reaction and separation, the optimization of theoretical plate number and residence time are studied in detail by combining experiments and numerical simulation, the feeding mole ratio of initial lactic acid to ethanol is 2-4:1, the unreacted complete lactic acid and the product ethyl lactate are separated by the product refining process through the design of the reaction rectification process, the recycling of reactant lactic acid to the reaction rectification zone is realized, and the mole ratio of lactic acid to ethanol is further increased in the reaction zone, so that the reaction is complete under the condition that the steady feeding mole ratio of lactic acid to ethanol is 1:1, and the problem of azeotropic separation of the unreacted complete ethanol and product water is avoided. And the reaction rectifying tower and the product refining tower are further integrated in a thermal coupling way, so that the aim of saving energy is fulfilled.
The technology of the invention is as follows:
the invention relates to a high-efficiency energy-saving ethyl lactate reaction rectification production method which comprises the following steps: the method comprises the steps that the lactic acid and the ethanol which are raw materials for production respectively enter a reaction rectifying zone from the top and the bottom of a reaction section, esterification is carried out in catalytic separation inner components of the reaction rectifying zone, and meanwhile, product water and ethyl lactate are rapidly removed from the reaction rectifying zone, so that reactant ethanol is completely converted; the unreacted complete lactic acid and the product ethyl lactate are separated through a product refining process, so that the reactant lactic acid is recycled to the reaction rectifying area, and the molar ratio of the lactic acid to the ethanol in the reaction rectifying area is ensured to be at a higher value; and discharging the final product water from the top of the reactive rectifying tower, and obtaining a high-purity ethyl lactate product at the top of the product refining unit tower.
The high-efficiency energy-saving ethyl lactate reaction rectification production method has the following operation process conditions:
the operation pressure of the reactive distillation process is 40-101 kPa; the reflux ratio of the reactive distillation process is 1-10.
The operation pressure of the product refining process is 100 Pa-5 kPa; the reflux ratio is 0.5-3.
The residence time of the reaction materials in each theoretical stage of the reaction zone is 20-70 seconds.
The catalyst loading capacity on each theoretical plate of the reactive distillation zone is 0.1-0.6 cm 3 Catalyst/cm 3 And (3) a catalytic filler.
The initial feeding mole ratio of lactic acid to ethanol is 2-4:1, unreacted complete lactic acid circulates in the reactive rectifying tower when the process reaches a steady state, the steady state feeding mole ratio of lactic acid to ethanol is 1:1, and the mole ratio of reactant lactic acid to ethanol is 2-4:1 in the reactive rectifying area.
The device for realizing the efficient energy-saving ethyl lactate reaction rectification production method can be independently realized by two towers, namely a reaction rectification tower and a product refining tower or by a reaction rectification complete thermal coupling partition tower.
The invention relates to a high-efficiency energy-saving ethyl lactate reaction rectification production device, which can be composed of a reaction rectification tower (3) and a product refining tower (17); 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; 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) and related feed pipelines and pipelines connected with the above devices; the fresh lactic acid (1) feed line is connected to the top of the reaction section (5) of the reaction rectifying tower (3), the ethanol (2) feed line is connected to the bottom of the reaction section (5) of the reaction rectifying tower (3), the top steam (7) of the reaction rectifying tower (3) is connected with the gas phase inlet of the top water condenser (8) through a pipeline, the condensed liquid phase water (9) material extraction pipeline is connected with the liquid phase outlet of the top water condenser (8), meanwhile, one part of the liquid phase outlet of the 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 the light component removed; the tower kettle 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 product refining tower through a pipeline (20), a part (23) after condensation flows back to the top of the product refining tower (17), the other part (24) is extracted from the top of the product refining tower as a high-purity ethyl lactate product, and a part (29) of the liquid-phase product at the tower kettle of the product refining tower (17) is extracted and returned to the top of the reaction section (5) of the reaction rectifying tower (3).
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, wherein the rectifying section and the stripping section are filled or trays, and the inner parts of the reaction section are regular supported molecular sieve type catalytic separation inner members or catalytic filling or a combination form of the regular supported molecular sieve type catalytic separation inner members or the catalytic filling; the product refining tower (17) consists of a product refining tower rectifying section (18) and a product refining tower stripping section (19), and tower internals are all fillers or trays. The number of the tower plates of the reactive rectifying tower is 20-50, wherein the number of the tower plates of the rectifying section is 5-15, the number of the tower plates of the reactive section is 10-40, and the number of the tower plates of the stripping section is 2-15; the number of the tower plates of the product refining tower is 10-20, wherein the number of the tower plates of the rectifying section is 5-9, and the number of the tower plates of the stripping section is 7-15. The reaction rectification complete thermal coupling bulkhead tower (30) is divided into five areas, namely a main tower rectifying section (31), a main tower reaction section (32), a main tower stripping section (33), an auxiliary tower rectifying section (34) and an auxiliary tower stripping section (35), wherein a partition plate is arranged in the middle of the tower, the upper part of the partition plate is capped, 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, and 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 invention relates to a high-efficiency energy-saving ethyl lactate reactive distillation production device, which is independently realized by a reactive distillation complete thermal coupling bulkhead tower (30), wherein the reactive distillation complete thermal coupling bulkhead tower (30) consists of a main tower rectifying section (31), a main tower reacting section (32), a main tower stripping section (33), a secondary tower rectifying section (34) and a secondary tower stripping section (35). The one-tower device comprises a reaction rectification complete thermal coupling bulkhead tower (30), a tower top water condenser (8), a tower top ethyl lactate condenser (21), a tower bottom lactic acid reboiler (27), related feed pipelines and pipelines for connecting the above devices; the fresh lactic acid (1) is connected to the top of a reaction section (32) of a reaction distillation complete thermal coupling bulkhead column (30), the fresh ethanol (2) is connected to the bottom of the reaction section (32) of the reaction distillation complete thermal coupling bulkhead column (30), the main column top steam (7) of the reaction distillation complete thermal coupling bulkhead column (30) is connected with a gas phase inlet of a top water condenser (8) through a pipeline, a material extraction pipeline (9) is connected with a liquid phase outlet of the top water condenser (8), a part of the liquid phase outlet of the top water condenser (8) is connected with the main column top of the reaction distillation complete thermal coupling bulkhead column (30) through a pipeline (10), and the other part (11) is discharged as a removed light component; the reaction rectification complete thermal coupling bulkhead column (30) is connected with a gas phase inlet of a gas phase ethyl lactate condenser (21) at the top of the auxiliary column 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 column, meanwhile, one part of the liquid phase outlet of the ethyl lactate condenser (21) at the top of the column is connected with the auxiliary column top of the reaction rectification complete thermal coupling bulkhead column (30) through a pipeline (23), and the other part (24) is extracted from the top of the column as a high-purity ethyl lactate product; the liquid at the bottom of the reaction rectification complete thermal coupling partition wall tower (30) is connected with the liquid phase inlet of a tower bottom lactic acid reboiler (27) through a pipeline (26), 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 partition wall tower (30) through a pipeline (28), and the other part of the material (29) is extracted as a raw material, is converged with the fresh raw material (1) and returns to the top of a reaction section (32) of the reaction rectification complete thermal coupling partition wall tower (30).
The reaction rectification complete thermal coupling bulkhead tower (30) is divided into five areas, namely a main tower rectifying section (31), a main tower reaction section (32), a main tower stripping section (33), a secondary tower rectifying section (34) and a secondary tower stripping section (35), wherein a partition plate is arranged in the middle of the tower, the upper part of the partition plate is capped, the tower body is divided into a main tower and a secondary tower, the reaction area is positioned in the main tower, the product refining area is positioned in the secondary tower, and 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 tower internals 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 fillers or trays, and the tower internals of the main tower reaction section (32) are regular load molecular sieve type catalytic separation internals or catalytic fillers or a combination form thereof; the tower internals 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 tower internals of the main tower reaction section (32) are regular load molecular sieve type catalytic separation internals or catalytic packing or a combination form thereof. The total tray number of the reaction distillation complete thermal coupling partition wall tower is 40-80, wherein the tray number of the rectifying section of the main tower is 5-10, the tray number of the reacting section of the main tower is 10-40, the tray number of the stripping section of the main tower is 5-13, the tray number of the rectifying section of the auxiliary tower is 10-20, and the tray number of the stripping section of the auxiliary tower is 10-15.
The invention relates to a high-efficiency energy-saving ethyl lactate reaction rectification production device which 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 a produced ethyl lactate pipeline, the bottom of the product refining tower is provided with a produced 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 and energy-saving reactive distillation technology. Lactic acid and ethanol enter a product refining unit after the reaction rectification process, so that a high-purity ethyl lactate product is obtained, and the lactic acid is extracted from a tower kettle and recycled to the reaction 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 efficient energy-saving ethyl lactate reactive distillation production, and the process flow consists of a reactive distillation column (3) and a product refining column (17).
Fig. 2 is a schematic diagram of a process flow of efficient energy-saving ethyl lactate reactive distillation production, which consists of a reactive distillation complete thermal coupling bulkhead column (30).
Wherein: 1-lactic acid; 2-ethanol; 3-a reactive rectifying tower; 4-a rectifying section of the reactive rectifying tower; 5-a reaction section of the reactive rectifying tower; 6-stripping section of the reactive rectifying tower; 7-gas phase water; 8-an overhead water condenser; 9-liquid phase water; 10-reflux water; 11-distilling off water; 12-crude bottom product; 13-returning the liquid phase crude product; 14-a bottom crude reboiler; 15-returning the tower gas phase crude product; 16-crude product extraction; 17-a product refining tower; 18-rectifying section of product refining tower; 19-a stripping section of a product refining tower; 20-gaseous ethyl lactate; 21-ethyl lactate condenser at the top of the tower; 22-ethyl lactate in liquid phase; 23-refluxing ethyl lactate; 24-high purity ethyl lactate; 25-bottom liquid lactic acid; 26-returning to the tower liquid phase lactic acid; 27-a bottom lactic acid reboiler; 28-returning tower gas phase lactic acid; 29-circulating lactic acid; 30-reaction rectification is complete and thermally coupled with a bulkhead tower; 31-a main column rectifying section; 32-a main tower reaction section; 33-a stripping section of the main tower; 34-a rectifying section of the auxiliary tower; 35-a stripping section of the auxiliary tower.
Detailed Description
The method and apparatus provided by the present invention are further described below with reference to the accompanying drawings.
The invention is realized by the following technical scheme:
as shown in fig. 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 vapor entering the tower are subjected to esterification reaction in the reaction section (5), the generated water enters a top water condenser (8) from a top gas-phase outlet (7) of the reaction rectifying tower (3) to be condensed, the condensed material flows out from a liquid-phase outlet of the top water condenser (8), a part of liquid-phase water (9) is used as top reflux water (10) to flow into the reaction rectifying tower (3), the other part of fractionated water (11) is used as a removed light component to be discharged, unreacted lactic acid and generated ethyl lactate enter a bottom crude product reboiler (14) from a part (13) of a tower bottom liquid-phase outlet (12) of the reaction rectifying tower (3), the other part is used as a crude product to be extracted (16), the liquid-phase material (16) extracted from the reaction rectifying tower (3) enters a product refining tower top (17) from a liquid-phase outlet of the top water condenser (8), a part of liquid-phase material (17) is used as a top ethyl lactate reflux product (20) is extracted from a top ethyl lactate (20) of the top of the reaction rectifying tower (17), and a part of the ethyl lactate (20) is used as a reflux ethyl lactate (23) is extracted from the top of the ethyl lactate (20) of the top of the product, part (26) of the liquid phase lactic acid (25) at the bottom of the tower returns to the bottom of the product refining tower (17) through a reboiler (27) at the bottom of the tower, and the other part of the material (29) is taken as a raw material to be combined with the fresh raw material (1) and then returns to the top of the reaction section (5) of the reaction rectifying tower (3).
As shown in fig. 2, fresh lactic acid (1) is fed from the top of a reaction section (32) in a reaction distillation complete thermal coupling partition wall tower (30), fresh ethanol (2) is fed from the bottom of a reaction section (2) in the reaction distillation complete thermal coupling partition wall tower (30), liquid-phase lactic acid and ethanol vapor entering the tower undergo esterification reaction in the reaction section (2), generated water enters a top water condenser (8) from a top gas phase outlet (7) of a main tower of the reaction distillation complete thermal coupling partition wall tower (30) to be condensed, the condensed material flows out from a liquid phase outlet of the top water condenser (8), a part of liquid-phase water (9) flows into the main tower of the reaction distillation complete thermal coupling partition wall tower (30) as top reflux water (10), and the other part of fractional effluent (11) is discharged as removed light components; the product ethyl lactate enters a tower top ethyl lactate condenser (21) from a gas phase outlet (20) at the tower top of a reaction rectification complete thermal coupling partition wall tower (30) and is condensed, condensed materials flow out from a liquid phase outlet of the tower top ethyl lactate condenser (21), one part of liquid phase ethyl lactate (22) is taken as tower top reflux ethyl lactate (23) to flow into the reaction rectification complete thermal coupling partition wall tower (30) and the other part of high-purity ethyl lactate (24) is taken as product ethyl lactate to be extracted from the tower top of the reaction rectification complete thermal coupling partition wall tower (30); a part of material (26) of liquid phase lactic acid (25) at the bottom of the reaction rectification complete thermal coupling partition wall tower (30) returns to the bottom of the reaction rectification complete thermal coupling partition wall tower (30) through a bottom lactic acid reboiler (27), and the other part of material (29) is taken as a raw material to be combined with the fresh raw material (1) and then returns to the top of a reaction section (32) of the reaction rectification complete thermal coupling partition wall tower (30).
The high-efficiency energy-saving ethyl lactate reaction rectification production method has the following operation process conditions: the operation pressure of the reactive distillation process is 40-101 kPa; the reflux ratio of the reactive distillation process is 1-10. The operation pressure of the product refining process is 100 Pa-5 kPa; the reflux ratio is 0.5-3. The residence time of the reaction materials in each theoretical stage of the reaction zone is 20-70 seconds. The mol ratio of the reactant lactic acid to the ethanol in the reaction rectifying area is 2-4:1.
If the device consists of a reaction rectifying tower (3) and a product refining tower (17), the reaction rectifying tower (3) consists of a reaction rectifying tower rectifying section (4), a reaction rectifying tower reacting 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), a tower top water condenser (8), a tower top ethyl lactate condenser (25), a tower bottom crude product reboiler (14), a tower bottom lactic acid reboiler (27) and related feed pipelines and pipelines connected with the above devices; fresh lactic acid (1) feed line is connected to the top of reaction section (5) of reaction rectifying column (3), ethanol (2) feed line is connected to the bottom of reaction section (5) of reaction rectifying column (3), reaction rectifying column (3) top gas phase water (7) is connected with top water condenser (8) gas phase import through the pipeline, liquid phase water (9) material pipeline links to each other with top water condenser (8) liquid phase export, top water condenser (8) liquid phase export is connected with reaction rectifying column (3) top through pipeline (10) simultaneously one portion, another portion (11) are the light component of desorption is taken out. The tower kettle 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 product refining tower through a pipeline (20), a part (23) after condensation flows back to the top of the product refining tower (17), the other part (24) is extracted from the top of the product refining tower as a high-purity ethyl lactate product, and a part (29) of the liquid-phase product at the tower kettle 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 distillation complete thermal coupling bulkhead column (30) and a column is independent, the reaction distillation complete thermal coupling bulkhead column (30) consists of a main column rectifying section (31), a main column reaction section (32), a main column stripping section (33), a secondary column rectifying section (34) and a secondary column stripping section (35). The one-tower device comprises a reaction rectification complete thermal coupling bulkhead tower (30), a tower top water condenser (8), a tower top ethyl lactate condenser (25), a tower bottom lactic acid reboiler (27), related feed pipelines and pipelines for connecting the above devices; the fresh lactic acid (1) feed line is connected to the top of the reaction section (32) of the reaction distillation complete thermal coupling bulkhead column (30), the fresh ethanol (2) feed line is connected to the bottom of the reaction section (32) of the reaction distillation complete thermal coupling bulkhead column (30), the gas phase water (7) at the top of the main column of the reaction distillation complete thermal coupling bulkhead column (30) is connected with the gas phase inlet of the top water condenser (8) through a pipeline, the liquid phase water (9) feed line is connected with the liquid phase outlet of the top water condenser (8), at the same time, one part of the liquid phase outlet of the top water condenser (8) is connected with the top of the main column of the reaction distillation complete thermal coupling bulkhead column (30) through a pipeline (10), and the other part (11) is discharged as the removed light component. The reaction rectification complete thermal coupling bulkhead column (30) is connected with a gas phase inlet of a gas phase ethyl lactate condenser (21) at the top of a secondary column 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 column, meanwhile, one part of the liquid phase outlet of the ethyl lactate condenser (21) at the top of the column is connected with the top of the secondary column of the reaction rectification complete thermal coupling bulkhead column (30) through a pipeline (23), and the other part (24) is taken out of the top of the column as a high-purity ethyl lactate product. The liquid at the bottom of the reaction rectification complete thermal coupling partition wall tower (30) is connected with the liquid phase inlet of a tower bottom lactic acid reboiler (27) through a pipeline (26), 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 partition wall tower (30) through a pipeline (28), and the other part of the material (29) is extracted as a raw material, is converged with the fresh raw material (1) and returns to the top of a reaction section (32) of the reaction rectification complete thermal coupling partition wall tower (30).
The invention relates to a high-efficiency energy-saving ethyl lactate reaction rectification production device which 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 a produced ethyl lactate pipeline, the bottom of the product refining tower is provided with a produced 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, in embodiments 1 and 2, the reaction rectifying tower (3) is composed 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, wherein the internal parts of the rectifying section and the stripping section are all 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 thereof; the product refining tower (17) consists of a product refining tower rectifying section (18) and a product refining tower stripping section (19), and tower internals are all fillers or trays. The number of the tower plates of the reaction rectifying tower is 20-50, wherein the number of the tower plates of the rectifying section is 5-15, and the number of the tower plates of the reaction section is 10-40The number of the stripping section tower plates is 2-15; the number of the tower plates of the product refining tower is 10-20, wherein the number of the tower plates of the rectifying section is 5-9, and the number of the tower plates of the stripping section is 7-15. Or as shown in fig. 2, in embodiments 3 and 4, the reaction rectification fully thermally coupled bulkhead column (30) is divided into five areas, namely a main column rectifying section (31), a main column reacting section (32), a main column stripping section (33), a secondary column rectifying section (34) and a secondary column stripping section (35), a partition plate is arranged in the middle of the column, the upper part of the column is capped, the column body is divided into a main column and a secondary column, the reaction area is positioned in the main column, the product refining area is positioned in the secondary 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 tower internals 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 tower internals of the main tower reaction section (32) are regular load molecular sieve type catalytic separation internals or catalytic packing or a combination form thereof. The total tray number of the reaction distillation complete thermal coupling partition wall tower is 40-80, wherein the tray number of the rectifying section of the main tower is 5-10, the tray number of the reacting section of the main tower is 10-40, the tray number of the stripping section of the main tower is 5-13, the tray number of the rectifying section of the auxiliary tower is 10-20, and the tray number of the stripping section of the auxiliary tower is 10-15. The catalyst loading capacity on each theoretical plate of the reactive distillation zone is 0.1-0.6 cm 3 Catalyst/cm 3 And (3) a catalytic filler.
The technique and apparatus of the present invention are widely applicable to the process of preparing ethyl lactate from lactic acid and ethanol esterification, and in order to better illustrate the advantages of the present invention in terms of product purity and yield, are compared with the procedure described in patent CN 100427453C. Four of these examples are chosen for illustration, but are not limiting the scope of applicability of the present technology and apparatus.
Example 1
The method is used for the process of preparing the ethyl lactate by esterifying the lactic acid and the ethanol, and has the same flow as the flow of the method, 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 operation pressure of the reaction rectifying tower is 101kPa, the reflux ratio is 9, the fresh lactic acid feeding amount is 50kmol/h, and the method is biologicalThe molar ratio of the reaction of the plasma lactic acid and the ethanol is 2, and the loading capacity of the catalyst is 0.1cm 3 Catalyst/cm 3 The catalytic packing, the operating pressure of the product refining column 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 reactive distillation process, the energy consumption can be reduced by more than 30%.
Example 2
The method is used for the process of preparing the ethyl lactate by esterifying the lactic acid and the ethanol, and has the same flow as the method, 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 operation pressure of the reaction rectifying tower is 40kPa, the reflux ratio is 10, the fresh lactic acid feeding amount is 15kmol/h, the reaction mole ratio of biomass-based lactic acid and the ethanol is 3, and the catalyst loading capacity is 0.1cm 3 Catalyst/cm 3 The catalytic packing, the operating pressure of the product refining column 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 reactive distillation 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, and has the same flow as the flow of the method, and comprises a reaction rectification complete thermal coupling partition wall 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 partition wall tower is 50kPa, the reflux ratio of a main tower is 2, the reflux ratio of a subsidiary tower is 3, the fresh lactic acid feeding amount is 30kmol/h, the reaction mole ratio of biomass-based lactic acid and ethanol is 4, and the catalyst loading capacity is 0.1cm 3 Catalyst/cm 3 And (3) a 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 reactive distillation process, the energy consumption can be reduced by more than 40%.
Example 4
The method is used for the process of preparing the ethyl lactate by esterifying the lactic acid and the ethanol, and has the same flow as the method, and comprises a reaction rectification complete thermal coupling partition wall 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 partition wall tower is 40kPa, the reflux ratio of a main tower is 1.5, the reflux ratio of a subsidiary tower is 2.5, the fresh lactic acid feeding amount is 15kmol/h, the reaction mole ratio of biomass-based lactic acid and the ethanol is 3, and the catalyst loading amount is 0.1cm 3 Catalyst/cm 3 And (3) a 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 reactive distillation process, the energy consumption can be reduced by more than 30%.
The invention provides a high-efficiency energy-saving ethyl lactate reactive distillation production method and device, which are described by a preferred embodiment, and related technicians can obviously change or appropriately change and make up the equipment and the process flow described herein without departing from the content, spirit and scope of the invention so as to realize the technology 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 included within the spirit, scope and content of the invention.
Claims (3)
1. An efficient energy-saving ethyl lactate reaction rectification production method; the method is characterized in that raw materials ethanol and lactic acid respectively enter a reaction rectifying zone from the bottom and the top of a reaction section, and product water and ethyl lactate are removed while the esterification reaction is catalyzed by a regular supported molecular sieve type catalytic separation inner member or catalytic filler or a combination form of the regular supported molecular sieve type catalytic separation inner member or the catalytic filler to form the reaction rectifying zone, so that reactant ethanol is completely converted; the unreacted complete lactic acid and the product ethyl lactate are separated through a product refining process, so that the reactant lactic acid is recycled to the reaction rectifying area, and the molar ratio of the lactic acid to the ethanol in the reaction rectifying area is ensured to be at a higher value; the final product water is discharged from the top of the reactive rectifying tower, and a high-purity ethyl lactate product is obtained at the top of the product refining unit tower; the initial feeding mole ratio of lactic acid to ethanol is 2-4:1, unreacted complete lactic acid circulates in the reactive rectifying tower when the process reaches a steady state, the steady state feeding mole ratio of lactic acid to ethanol is 1:1, and the mole ratio of reactant lactic acid to ethanol is 2-4:1 in the reactive rectifying area; the production device consists of a reaction rectifying tower (3) and a product refining tower (17); 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; 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) and related feed pipelines and pipelines connected with the above devices; the fresh lactic acid (1) feed line is connected to the top of the reaction section (5) of the reaction rectifying tower (3), the ethanol (2) feed line is connected to the bottom of the reaction section (5) of the reaction rectifying tower (3), the top steam (7) of the reaction rectifying tower (3) is connected with the gas phase inlet of the top water condenser (8) through a pipeline, the condensed liquid phase water (9) material extraction pipeline is connected with the liquid phase outlet of the top water condenser (8), meanwhile, one part of the liquid phase outlet of the 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 the light component removed; the tower kettle 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 tower top of the product refining tower (17) is connected with the gas phase inlet of the ethyl lactate condenser (21) at the tower top through a pipeline (20), a part (23) after condensation flows back to the tower top of the product refining tower (17), the other part (24) is extracted from the tower top as a high-purity ethyl lactate product, and a part (29) of the liquid-phase product at the tower kettle of the product refining tower (17) is extracted and returned to the top of the reaction section (5) of the reaction rectifying tower (3); the number of the tower plates of the reactive rectifying tower is 20-50, wherein the number of the tower plates of the rectifying section is 5-15, the number of the tower plates of the reactive section is 10-40, and the number of the tower plates of the stripping section is 2-15; the number of the tower plates of the product refining tower is 10-20, wherein the number of the tower plates of the rectifying section is 5-9, and the number of the tower plates of the stripping section is 7-15.
2. The method of claim 1, wherein the reactive distillation process is operated at a pressure of 40 to 101kPa; the reflux ratio of the reactive distillation process is 1-10; the operation pressure of the product refining process is 100 Pa-5 kPa; the reflux ratio is 0.5-3.
3. The process of claim 1 wherein the residence time of the reaction mass per theoretical stage in the reaction zone is from 20 to 70 seconds; the catalyst loading capacity on each theoretical plate of the reactive distillation zone is 0.1-0.6 cm 3 Catalyst/cm 3 And (3) a catalytic filler.
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