CN101898965A - Two-step method for producing propyl lactate with high content and high optical purity - Google Patents
Two-step method for producing propyl lactate with high content and high optical purity Download PDFInfo
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Abstract
The invention relates to a method for producing propyl lactate with high content and high optical purity through a two-step method of ester exchange reaction of lactide and propyl alcohol. The method comprises the steps of: adding a catalyst in lactic acid to carry out polycondensation to obtain lactic acid oligomer with the molecular weight of 1000 to 2500; adding the catalyst in the lactic acid oligomer to carrying out depolymerisation to obtain crude lactide; and refining the crude lactide, and carrying out total reflux reaction on the refined lactide and anhydrous propyl alcohol to obtain the propyl lactate. The invention has simple technology. The content of the combined propyl lactate is more than 99.5%, and the optical purity can reach more than 99%.
Description
Technical field
The invention belongs to field of chemical technology, being specifically related to a kind of is direct material by rac-Lactide and absolute alcohol, produces the method for high-content and high-optical-purity propyl lactate by the transesterification reaction two step method.
Background technology
Lactate has special Rum, fruit and cream fragrance, is a kind of important fine chemical material.Because lactate contains unsymmetrical carbon, therefore have two kinds of optical isomers, it also is a kind of optically active essential industry solvent that has, can be used as the solvent of nitrocotton, acetate fiber, Synolac, shell pine ester, Manila resin, rosin, shellac, ethenoid resin, paint etc., still is the senior solvent of olivet class simultaneously.Also be used as softening agent at other industrial circle, in asymmetric synthesis, be used for synthetic having optically active carboxylicesters, be used as the lubricant, medicine pindolol intermediate of slugging etc. in the pharmacy.Therefore has extensive use in industries such as food, wine brewing, chemical industry, medicine.
Simultaneously since lactate have nontoxic, solvability good, little volatile, characteristics such as fruital smell are arranged, have biodegradable again, so lactate is to have that exploitation is worth and " green solvent " of application prospect again.Along with improving constantly of people's living standard, more and more higher to environment requirement, and mostly be deleterious solvent at the solvent of industrial use at present, the environment and the mankind have been caused great harm, as halo class, ethers, chloro-fluorocarbon kind solvent etc., so lactate has broad application prospects as " green solvent ".
Present homemade lactate can only be used for industries such as food as additive because content is not high and optical purity is not high.And fine chemistry industry industries such as medicine and agricultural chemicals need the lactate of high-optical-purity as intermediate feed, the lactate of high-optical-purity also is used in the cleaning of electronic product as solvent, so the lactate of high-optical-purity has more vast market prospect.High-content, the exploitation of high-optical-purity lactate Study on Production Technology at present be the progress of making a breakthrough property never.
The lactate synthetic technology, Chinese patent CN1229790A discloses a kind of method with natural materials for synthetizing ethyl lactate, CN1720215A discloses a kind of ethyl lactate method of preparation continuously, CN1438213A discloses a kind of technology for preparing ethyl lactate with the DL-Lactic acid ammonium salt for raw material reaction rectifying, CN1102180A discloses a kind of new technology for producing ethyl lactate, CN1114035 discloses a kind of technology of rectifying process for preparing ethyl lactate, CNCN1290686 is by the method for DL-Lactic acid ammonium salt catalysis Synthesis of ethyl lactate, CN1594585 discloses a kind of solution method of middle lactate synthesis enzyme catalysis ethyl ester mutually, and CN1613842 discloses a kind of novel process of catalytic distillation Synthesis of ethyl lactate.Chinese patent CN1450046 discloses the L-n-Butyl lactate synthetic method of a kind of high yield, high-optical-purity.All not adopting rac-Lactide and anhydrous propyl alcohol in all disclosed patents is raw material, produces lactate by transesterification reaction.
Summary of the invention
The objective of the invention is to overcome the existing existing defective of lactate production technology, provide a kind of two step method to produce the method for high-content and high-optical-purity propyl lactate, this method technology is simple, operates simple and easy, be fit to suitability for industrialized production and use, and do not have " three wastes " discharging.It is the raw material synthesis of lactide from that this method at first adopts lactic acid, is raw material synthesizing lactic acid ester with refined lactide and absolute alcohol again, and the whole piece operational path can be divided into lactide production and propyl lactate is produced two flow processs, so we are referred to as " two step method ".
Technical solution of the present invention is achieved in that it may further comprise the steps:
A, lactic acid polycondensation: add catalyzer in lactic acid, the weight ratio of catalyzer and lactic acid is 0.1/10000～10/10000, preferred 1/10000; Carry out polycondensation after adding, sustained reaction is 1～4 hour under the condition of 80～180 ℃ of temperature, vacuum tightness 20000～2000Pa, promptly obtains molecular weight at 1000～2500 lactic acid oligomer.
B, oligopolymer depolymerization: add catalyzer in lactic acid oligomer, the weight ratio of catalyzer and lactic acid oligomer is 0.1/10000～10/10000, preferred 1/10000; Add the back in depolymerizing reactor, successive reaction under the condition of 200～250 ℃ of temperature, vacuum tightness 3000～50Pa, the promptly sustainable content that obtains is in 80%～95% crude product of lactide.
C, rac-Lactide purifying: crude product of lactide is made with extra care, obtain content more than 99.5%, optical purity is in the refined lactide more than 99%;
D, lactate are synthetic: with refined lactide and the ratio adding reactor of anhydrous propyl alcohol by weight 1: 0.9～1: 8.3, be that 10/1000～100/1000 ratio adds catalyzer then by weight, preferred 50/1000, continuously stirring is carried out total reflux reaction, obtains propyl lactate;
E, lactate purifying: lactate is carried out purifies and separates.
The present invention's technical solution preferably is: before the lactic acid polycondensation, under vacuum tightness 10000～500Pa condition, under the condition that distillation temperature is 40～90 ℃ lactic acid is carried out vacuum distilling earlier, remove free-water wherein.
Wherein: the catalyzer that adds in lactic acid polycondensation and oligopolymer depolymerization is at least a in zinc class catalyzer, tin class catalyzer or the organic catalyst, and the weight ratio of its adding is 0.1/10000～5/10000, preferred 1/10000.The composite catalyst of one or more in preferred zinc lactate, zinc oxide, zinc powder, zinc ethyl, lactic acid tin, stannic oxide, tindioxide, tin protoxide, the inferior tin of lactic acid, stannous octoate, tin protochloride, glass putty, propionic acid or the butyl (tetra) titanate.Preferred catalyzer is that zinc oxide, stannic oxide and butyl (tetra) titanate are 1: 1: 1 mixture by weight.
Wherein: the catalyzer that adds in lactate is synthetic is one or both in exchange resin or the high strong acid catalyst of solid, and the weight ratio of its adding is 10/1000～100/1000.Preferred hydrogen type cation exchange resin or SO
4 2-The composite catalyst of one or both in the high strong acid catalyst of/TiO2 solid.More preferably hydrogen type cation exchange resin and SO
4 2-The high strong acid of/TiO2 solid is 1: 1 composite catalyst by weight.
Wherein: among the step C crude product of lactide being carried out the purified method is recrystallization, rectification under vacuum or fusion-crystallization, or two kinds and two or more combinations in the above-mentioned process for purification.Preferred first recrystallization is fusion-crystallization again.
Wherein: in the step e lactate being carried out purifies and separates is lactate to be joined rectifying tower carry out rectifying; the rectifying tower atmospheric operation; cat head and tower still pressure reduction are 1.5～3KPa; tower still temperature is 145 ℃～165 ℃; tower top temperature is 75～78 ℃; the tower side outlet obtains content at the propyl lactate product more than 99.5%, and cat head obtains the alcohol of content more than 99.5%, overflows content at the bottom of the tower at the lactoyl propyl lactate more than 99.5%.The lactoyl lactate that overflows at the bottom of the tower can return and participate in the propyl lactate building-up reactions in the reactor of step D.The propyl alcohol that cat head obtains can return and participate in the propyl lactate building-up reactions in the reactor of step D.
Compared with prior art, technical superiority of the present invention is:
1, the present invention produces the central refined lactide and the absolute alcohol of adopting of operational path of lactate as direct material, being different from traditional technology adopts lactic acid and alcohol as direct material, comparatively speaking, this technology has following characteristics: one, be raw material production reaction intermediate rac-Lactide with lactic acid, as everyone knows, lactic acid has two kinds of isomerss, the physicochemical characteristic of D-lactic acid and dextrolactic acid is very approaching, adopt common separating technology to be difficult to it is separated, and the optics content of lactic acid will directly influence the optics content of product methyl lactate.Rac-Lactide has two kinds of isomerss, four kinds of different existing waies: left-handed type, dextrorotatory form, racemize type and meso-form, left-handed and the fusing point dextrorotation rac-Lactide is 95 ℃～98 ℃, the fusing point of rac-lactide is 124 ℃～126 ℃, and the fusing point of Study of Meso-Lactide is 50 ℃～52 ℃, four under same temperature in the same solvent solubleness very big difference is also arranged, mesomeric maximum, left-handed and dextrorotation rac-Lactide takes second place, and the rac-Lactide minimum is revolved in export trade, and it is also bigger that four boiling point differs.So just it can be separated by common separate mode, this operational path adopts is one or both and two or more coupling purifies and separates modes in solvent recrystallization, rectification under vacuum, the fusion-crystallization, rac-Lactide after refining, content can reach more than 99.5%, optical purity can reach more than 99%, and water content is below 0.05%.Two, because extremely low as the moisture content of the absolute alcohol of raw material and refined lactide, and the transesterification reaction of being carried out can not produce reaction water, so entire reaction course need not to be with aqua, and reaction can carry out very thorough.Water content in the product lactate can be accomplished very low.Three, the optical purity of refined lactide can reach more than 99.5%, and the upset of configuration can not take place transesterification reaction, so synthetic ethyl lactate optical purity can reach more than 99.5%.
2, the present invention adopts hydrogen type cation exchange resin and SO
4 2-The high strong acid of/TiO2 solid wherein a kind of as catalyzer or two kinds with certain proportion blended composite catalyst, use the vitriol oil to compare with traditional technology as catalyzer, have following advantage: one, efficient, only need to add 10/1000～100/1000 of rac-Lactide weight and can reach the effect that improves speed of reaction.Two, can reuse, through using for a long time, the catalytic effect of catalyzer can reduce, and only needs this moment catalyzer to be taken out by filtering mode, handles through super-dry and simple the activation again, and catalyzer just can be reused.Three, can not cause corrosion, can significantly reduce investment cost of equipment equipment.Four, this type of catalyzer is in the middle of entire reaction course; only play the effect that accelerated reaction is carried out; and can not make reactant and product that other side reaction takes place; basically the unreacted alcohol that only exists in the lactate mother liquor, reaction product lactate, reaction carry out not thoroughly and the lactoyl lactate that produces, reduce the difficulty of rectifying separation greatly.Five, no spent acid discharging can not cause environmental pollution.
3, separation and purification lactate of the present invention can adopt the mode of atmospheric distillation or rectification under vacuum.Because mention in the above-mentioned advantage introduction that component has only three kinds in the lactate mother liquor; excessive alcohol, reaction product propyl lactate and unreacted be the lactoyl lactate completely; and three's separation factor is very big; so only need a rectifying tower just can reach isolating purpose; tower side discharge port obtains the lactate product; alcohol excess, overflow lactoyl lactate at the bottom of the tower are reclaimed in the cat head cooling.
4, operational path of the present invention is an environmental protection, pollution-free green route.One, the distilled water of lactic acid polycondensation process generation can satisfy the workshop ordinary production fully, cleaning is required, and the whole piece operational path does not have the demand of clean water substantially; Two, catalyzer can be reused, and not can with reactant generation side reaction, do not have the discharging of spent catalyst and byproduct of reaction; Three, three kinds of components are through after the rectifying separation in the reacted mother liquor, and lactate is sold as product, reclaim pure and mild lactoyl lactate and can return the participation reaction of transesterify workshop section, so not waste of raw material can all be converted into product.Just there is not the discharging of waste water,waste gas and industrial residue yet.
Embodiment
Below in conjunction with embodiment the present invention is described in further detail.
Example one:
Raw material is the lactic acid of 87% content of outsourcing, adopts falling-film evaporator that material acid is carried out vacuum distilling, and the temperature of charge of keeping in the falling-film evaporator reaches 50 ℃, and vacuum tightness maintains 8000Pa, the lactic acid after concentrating wherein monomer content more than 99%.Lactic acid 500Kg after concentrating is conveyed into polycondensation vessel by transferpump; in the weight ratio of zinc lactate and lactic acid is that 5/10000 ratio adds zinc lactate as catalyzer; in 2 hours; material is risen to 120 ℃ from 80 ℃; vacuum tightness maintains 5000Pa; entire reaction is carried out having under the condition of stirring; detect the viscosity of lactic acid oligomer by in-line viscometer; according to the viscosity molecular weight contrast relationship; determine that its molecular weight is whether between 1000～2500; if molecular weight is within this scope; by height pressure difference and vacuum pressure reduction lact-acid oligomer is conveyed into the depolymerization still; in the weight ratio of zinc lactate and lactic acid is that 5/10000 ratio adds zinc lactate as catalyzer; entire reaction is carried out having under the condition of stirring; material is warming up to 180 ℃ rapidly; vacuum tightness maintains 1000Pa; after the rac-Lactide vapor condensation that continues to obtain; enrichment in holding tank, in the depolymerization still material depolymerization complete, rac-Lactide go out that speed becomes very slowly the time; depolymerization reaction stops; liquid lactide in the holding tank enters purifying workshop section by transferpump, by recrystallization purifying process, obtains refined lactide 370Kg; content reaches 99.7%, and optical purity reaches 99.7%.Again refined lactide 370Kg is added esterifying kettle by handling equipment, in esterifying kettle, add anhydrous propyl alcohol 500Kg simultaneously, according to the weight ratio of hydrogen type cation exchange resin and rac-Lactide is that 60/1000 ratio adds hydrogen type cation exchange resin as catalyzer, 85 ℃ of temperature of charge, under the condition of normal pressure, continuously stirring total reflux transesterification reaction 3 hours, the mother liquor that reaction is finished enters surge tank by height pressure difference, by transferpump mother liquor is imported rectifying tower continuously again, control the rectifier bottoms temperature of charge at 155 ℃～160 ℃, 78 ℃ of tower top temperatures, cat head tower bottom pressure difference is 1.8KPa, cat head continues the recovery propyl alcohol, continue the overflow heavy constituent at the bottom of the tower, the tower side outlet continues the ethyl lactate product, and rectifying finishes, obtain content 99.5% altogether, optical purity is 99.7% propyl lactate 600Kg.The lactoyl propyl lactate that overflows at the bottom of the tower can return and participate in the propyl lactate building-up reactions in the lactate synthetic reactor.The propyl alcohol that cat head obtains can return and participate in the propyl lactate building-up reactions in the propyl lactate synthetic reactor.
Example two:
Lactic acid 500Kg after concentrating is conveyed into polycondensation vessel by transferpump; in the weight ratio of zinc oxide and lactic acid is that 10/10000 ratio adds zinc oxide as catalyzer; in 2 hours; material is risen to 120 ℃ from 80 ℃; vacuum tightness maintains 4000Pa; entire reaction is carried out having under the condition of stirring; detect the viscosity of lactic acid oligomer by in-line viscometer; according to the viscosity molecular weight contrast relationship; determine that its molecular weight is 1600; polycondensation is finished; by height pressure difference and vacuum pressure reduction lact-acid oligomer is conveyed into the depolymerization still; in the weight ratio of zinc oxide and lactic acid is that 10/10000 ratio adds zinc oxide as catalyzer; entire reaction is carried out having under the condition of stirring; material is warming up to 185 ℃ rapidly; vacuum tightness maintains 1500Pa; after the rac-Lactide vapor condensation that continues to obtain; enrichment in holding tank, in the depolymerization still material depolymerization complete, rac-Lactide go out that speed becomes very slowly the time; depolymerization stops; liquid lactide in the holding tank enters purifying workshop section by transferpump, by the fusion-crystallization purifying technique, obtains refined lactide 350Kg; content reaches 99.6%, and optical purity reaches 99.6%.Again refined lactide 350Kg is added esterifying kettle by handling equipment, in esterifying kettle, add anhydrous propyl alcohol 600Kg simultaneously, according to the weight ratio of hydrogen type cation exchange resin and rac-Lactide is that 80/1000 ratio adds hydrogen type cation exchange resin as catalyzer, 80 ℃ of temperature of charge, under the condition of normal pressure, continuously stirring total reflux transesterification reaction 4 hours, the mother liquor that reaction is finished enters surge tank by height pressure difference, by transferpump mother liquor is imported rectifying tower continuously again, control the rectifier bottoms temperature of charge at 155 ℃～165 ℃, 78 ℃ of tower top temperatures, cat head tower bottom pressure difference is 2.0KPa, cat head continues the recovery propyl alcohol, continue the overflow heavy constituent at the bottom of the tower, the tower side outlet continues the propyl lactate product, and rectifying finishes, obtain content 99.6% altogether, optical purity is 99.8% propyl lactate 565Kg.The lactoyl propyl lactate that overflows at the bottom of the tower can return and participate in the propyl lactate building-up reactions in the lactate synthetic reactor.The propyl alcohol that cat head obtains can return and participate in the propyl lactate building-up reactions in the propyl lactate synthetic reactor.
Example three:
With the content of outsourcing is that 95% lactic acid 500Kg is conveyed into polycondensation vessel by transferpump, in the weight ratio of catalyzer and lactic acid is that 8/10000 ratio adds mixed catalyst, and mixed catalyst is that zinc oxide, stannic oxide and butyl (tetra) titanate are 1: 1: 1 mixture by weight.In 2 hours, material is risen to 120 ℃ from 80 ℃, vacuum tightness maintains 5000Pa～4000Pa, entire reaction is carried out having under the condition of stirring, detect the viscosity of lactic acid oligomer by in-line viscometer, according to the viscosity molecular weight contrast relationship, determine that its molecular weight is 2000, polycondensation is finished, by height pressure difference and vacuum pressure reduction lact-acid oligomer is conveyed into the depolymerization still, in the weight ratio of catalyzer and lactic acid is that 8/10000 ratio adds mixed catalyst, and mixed catalyst is that zinc oxide, stannic oxide and butyl (tetra) titanate are 1: 1: 1 mixture by weight.Entire reaction is carried out having under the condition of stirring, material is warming up to 190 ℃ rapidly, vacuum tightness maintains 1600Pa, after the rac-Lactide vapor condensation that continues to obtain, and enrichment in holding tank, after depolymerization stops, liquid lactide in the holding tank enters purifying workshop section by transferpump, by the rectification under vacuum purifying technique, obtains refined lactide 320Kg, content reaches 99.8%, and optical purity reaches 99.8%.Again refined lactide 320Kg is added esterifying kettle by handling equipment, in esterifying kettle, add anhydrous propyl alcohol 400Kg simultaneously, according to SO
4 2-The weight ratio of high strong acid of/TiO2 solid and rac-Lactide is that 70/1000 ratio adds SO
4 2-/ M
2O
4The high strong acid of solid is as catalyzer, 90 ℃ of temperature of charge, under the condition of normal pressure, continuously stirring total reflux transesterification reaction 2.5 hours, the mother liquor that reaction is finished enters surge tank by height pressure difference, by transferpump mother liquor is imported rectifying tower continuously again, control the rectifier bottoms temperature of charge at 160 ℃～165 ℃, 78 ℃ of tower top temperatures, cat head tower bottom pressure difference is 2.0KPa, cat head continues the recovery propyl alcohol, continue the overflow heavy constituent at the bottom of the tower, the tower side outlet continues the propyl lactate product, and rectifying finishes, obtain content 99.6% altogether, optical purity is 99.9% propyl lactate 500Kg.The lactoyl propyl lactate that overflows at the bottom of the tower can return and participate in the lactate building-up reactions in the lactate synthetic reactor.The propyl alcohol that cat head obtains can return and participate in the propyl lactate building-up reactions in the lactate synthetic reactor.
Example four:
The preparation method of refined lactide is with example three, again refined lactide 320Kg is added esterifying kettle by handling equipment, in esterifying kettle, add anhydrous propyl alcohol 400Kg simultaneously, according to the weight ratio of composite catalyst is that 70/1000 ratio adds composite catalyst, and wherein composite catalyst is hydrogen type cation exchange resin and SO
4 2-The high strong acid of/TiO2 solid is 1: 1 mixture by weight; 90 ℃ of temperature of charge, under the condition of normal pressure, continuously stirring total reflux transesterification reaction 2.5 hours, the mother liquor that reaction is finished enters surge tank by height pressure difference, by transferpump mother liquor is imported rectifying tower continuously again, control rectifier bottoms temperature of charge is at 160 ℃～165 ℃, 78 ℃ of tower top temperatures, cat head tower bottom pressure difference is 2.0KPa, and cat head continues the recovery propyl alcohol, continues the overflow heavy constituent at the bottom of the tower, the tower side outlet continues the propyl lactate product, rectifying finishes, and obtains content 99.6% altogether, and optical purity is 99.9% propyl lactate 500Kg.The lactoyl propyl lactate that overflows at the bottom of the tower can return and participate in the lactate building-up reactions in the lactate synthetic reactor.The propyl alcohol that cat head obtains can return and participate in the propyl lactate building-up reactions in the propyl lactate synthetic reactor.
Claims (10)
1. a two step method is produced the method for high-content and high-optical-purity propyl lactate, and it may further comprise the steps:
A, lactic acid polycondensation: add catalyzer in lactic acid, the weight ratio of catalyzer and lactic acid is 0.1/10000～10/10000, carries out polycondensation after adding, and obtains molecular weight at 1000～2500 lactic acid oligomer;
B, oligopolymer depolymerization: add catalyzer in lactic acid oligomer, the weight ratio of catalyzer and lactic acid oligomer is 0.1/10000～10/10000, carries out depolymerization reaction after adding, and obtains content in 80%～95% crude product of lactide;
C, rac-Lactide purifying: crude product of lactide is made with extra care, obtain content more than 99.5%, optical purity is in the refined lactide more than 99%;
D, propyl lactate are synthetic: with refined lactide and the ratio adding reactor of anhydrous propyl alcohol by weight 1: 0.9～1: 8.3, be that 10/1000～100/1000 ratio adds catalyzer then by weight, continuously stirring is carried out total reflux reaction, obtains propyl lactate;
E, propyl lactate purifying: propyl lactate is carried out purifies and separates.
2. two step method according to claim 1 is produced the method for high-content and high-optical-purity propyl lactate, it may further comprise the steps: before the lactic acid polycondensation, earlier under vacuum tightness 10000～500Pa condition, under the condition that distillation temperature is 40～90 ℃ lactic acid is carried out vacuum distilling, remove free-water wherein.
3. two step method according to claim 1 is produced the method for high-content and high-optical-purity propyl lactate, wherein: the catalyzer that adds in lactic acid polycondensation and oligopolymer depolymerization is at least a in zinc class catalyzer, tin class catalyzer or the organic catalyst, and the weight ratio of its adding is 0.1/10000～5/10000.
4. the method for producing high-contents and high-optical-purity propyl lactate according to claim 1 or 3 described two step methods, wherein: the catalyzer that adds in lactic acid polycondensation and oligopolymer depolymerization is one or more the composite catalyst in zinc lactate, zinc oxide, zinc powder, zinc ethyl, lactic acid tin, stannic oxide, tindioxide, tin protoxide, the inferior tin of lactic acid, stannous octoate, tin protochloride, glass putty, propionic acid or the butyl (tetra) titanate.
5. two step method according to claim 1 is produced the method for high-content and high-optical-purity propyl lactate, wherein: the catalyzer that adds in propyl lactate is synthetic is one or both in exchange resin or the high strong acid catalyst of solid, and the weight ratio of its adding is 10/1000～100/1000.
6. the two step method method of producing high-content and high-optical-purity propyl lactate according to claim 1 or 5, wherein: the catalyzer of adding is hydrogen type cation exchange resin or SO in propyl lactate is synthetic
4 2-The composite catalyst of one or both in the high strong acid catalyst of/TiO2 solid.
7. two step method according to claim 1 is produced the method for high-content and high-optical-purity propyl lactate, it is characterized in that: among the step C crude product of lactide being carried out the purified method is recrystallization, rectification under vacuum or fusion-crystallization, or two kinds and two or more combinations in the above-mentioned process for purification.
8. two step method according to claim 1 is produced the method for high-content and high-optical-purity propyl lactate, and wherein: what in the step e propyl lactate is carried out the purifies and separates employing is rectification process, and rectifying tower is atmospheric operation or decompression operation; Cat head and tower still pressure reduction are 1.5～3KPa during atmospheric operation; tower still temperature is 165 ℃～175 ℃; tower top temperature is 82～98 ℃; the tower side outlet obtains content at the propyl lactate product more than 99.5%; cat head obtains the propyl alcohol of content more than 99.5%, overflows content at the bottom of the tower at the lactoyl propyl lactate more than 99.5%.
9. two step method according to claim 8 is produced the method for high-content and high-optical-purity propyl lactate, wherein: the lactoyl propyl lactate that overflows at the bottom of the rectifying Tata is returned in the reactor of step D and participate in the propyl lactate building-up reactions.
10. two step method according to claim 8 is produced the method for high-content and high-optical-purity propyl lactate, and wherein: the recovery propyl alcohol that the rectifying tower cat head is obtained returns in the reactor of step D and participates in the propyl lactate building-up reactions.
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| CN114957197A (en) * | 2022-05-11 | 2022-08-30 | 普立思生物科技有限公司 | Preparation method of lactide |
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