CN102675102A - Continuous production method of high-content high-optical-purity lactate - Google Patents
Continuous production method of high-content high-optical-purity lactate Download PDFInfo
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Abstract
The invention relates to a continuous production method of high-content high-optical-purity lactate. The continuous production method of high-content high-optical-purity lactate includes the steps of adding catalyst in lactic acid to allow for polycondensation to obtain lactic acid oligomer with 1000-2500 molecular weight; adding catalyst into the lactic acid oligomer to allow for depolymerization to obtain crude lactide; and refining the crude lactide, and subjecting the refined lactide and organic alcohol to full-reflux reaction to obtain lactate. The continuous production method is simple in process, easy and simple to operate and suitable for industrial production and application. The materials can all be utilized. No 'three wastes' emission occurs. Content of the synthetized lactate is more than 99.5%, and optical purity of the lactate can reach more than 99%.
Description
Technical field
The invention belongs to field of chemical technology, being specifically related to a kind of is raw material by purified grade rac-Lactide and absolute alcohol, through the method for direct continuous production high-content of transesterification reaction and high-optical-purity lactate.
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 synthesizing and have optically active carboxylicesters; Be used as lubricant, medicine pindolol midbody of slugging etc. in the pharmacy; That the lactate of some higher alcoholss because have stimulates is little, not volatile, spreadability good, good water solubility, can with characteristic such as other water soluble component compatibility, often be used in the makeup.Therefore lactate 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.Improving constantly of Along with people's standard of living; Increasingly high to environment requirement; And the solvent that in industry, uses at present mostly is deleterious solvent, the environment and the mankind has been caused great harm, like halo class, ethers, chloro-fluorocarbon kind solvent etc.; Therefore lactate has broad application prospects as " green solvent ", and wherein the ethyl lactate of electronic-grade is widely used at the electronics cleaning industry.
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, and CN1114035 discloses a kind of technology of rectifying process for preparing ethyl lactate, and 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.CN1740331 discloses a kind of biorefinery and has produced the extremely process method of joint product of ethyl lactate; CN101575622 discloses a kind of process method of being produced ethyl lactate by DL-Lactic acid ammonium salt; CN1290686A discloses a kind of method by DL-Lactic acid ammonium salt catalysis Synthesis of ethyl lactate; Chinese patent CN101759559A discloses a kind of method for preparing low water content, the low high-load newborn n-propyl of acidity, and Chinese patent CN1450046 discloses the L-n-Butyl lactate compound method of a kind of high yield, high-optical-purity.
All not adopting rac-Lactide and absolute alcohol in all disclosed patents is raw material, produces high-optical-purity lactate through transesterification reaction, and also not adopting rac-Lactide purifying mother liquor and absolute ethyl alcohol is the ethyl lactate of raw material production electronic-grade.
Summary of the invention
The objective of the invention is to overcome the existing existing defective of lactate production technology, the method for a kind of continuous production high-content and high-optical-purity lactate is provided.The present invention also provides a kind of method of electronic-grade ethyl lactate.The inventive method technology is simple, operates simple and easyly, is fit to suitability for industrialized production and uses, and raw material can all utilize, and does not have " three wastes " discharging.It is the raw material synthesis of lactide from that the present invention at first adopts lactic acid; Be raw material synthesizing lactic acid ester with refined lactide and absolute alcohol again; With rac-Lactide purifying mother liquor and absolute ethyl alcohol is the raw material Synthesis of ethyl lactate, and the whole piece operational path can be divided into lactide production and lactate is produced two flow processs.
Technical solution of the present invention is achieved in that it may further comprise the steps:
A, lactic acid polycondensation: in lactic acid, add catalyzer, 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: in lactic acid oligomer, add catalyzer, 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 at refined lactide more than 99.5% and acyl lactylates purifying mother liquor;
D, high-optical-purity lactate are synthetic: with refined lactide and the ratio adding dissolution kettle of anhydrous organic alcohol by weight 1: 0.7～1: 5; Preferred 1: 3 ratio; Rac-Lactide is dissolved in organic alcohol fully; Then with the alcoholic solution of rac-Lactide through the fixed-bed reactor of catalyzer are housed, transesterification reaction takes place in rac-Lactide and organic alcohol, obtains lactate.
E, electronic-grade ethyl lactate synthetic: with acyl lactylates purifying mother liquor and absolute ethyl alcohol by weight 1: 0.7～1: 5 mixed even, through the fixed-bed reactor of catalyzer are housed, obtain ethyl lactate then.
F, 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 in lactic acid polycondensation and oligopolymer depolymerization, adds is at least a in zinc class catalyzer, tin class catalyzer, titanium class catalyzer or the organic acid catalyzer, and the weight ratio of its adding is 0.1/10000～50/10000.The composite catalyst of one or more in preferred zinc lactate, zinc oxide, zinc powder, zinc ethyl, lactic acid tin, White tin 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, White tin oxide and butyl(tetra)titanate are by weight the mixture that is 1: 1: 1.Another preferred catalyzer is that zinc lactate, propionic acid and butyl(tetra)titanate are by weight the mixture that is 1: 1: 1.
Wherein: the catalyzer that in fixed bed, adds is one or both in exchange resin or the high strong acid catalyst of solid.Preferred hydrogen type cation exchange resin or SO
4 2-/ TI
2O
4The composite catalyst of one or both in the high strong acid catalyst of solid.More preferably hydrogen type cation exchange resin and SO
4 2-/ TI
2O
4The high strong acid of solid is by weight the mixture that is 1: 2.
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 rectification under vacuum is fusion-crystallization again.
Wherein: being used for lactate synthetic fixed-bed reactor among step D and the E is calandria type fixed bed reactors, can be that single slage fixed bed reactor drum also can be the multi-stage type fixed-bed reactor that formed by two or more calandria type fixed bed reactor series connection.
Wherein: what lactate carried out the purifies and separates employing in the step F is rectification process; Mainly be made up of three grades of rectifying tower, first step rectifying tower removes most alcohol excess, and second stage rectifying tower removes heavy constituent such as acyl lactylates; Third stage rectifying tower removes remaining alcohol, obtains product.First step rectifying tower is a decompression operation, operation vacuum tightness is-0.02～-0.08MPa, the pure content in the bottoms material is 1～5%; Second stage rectifying tower is a decompression operation, operation vacuum tightness is-0.086～-0.098MPa, the lactate content in the bottoms material is 5%～20%; Third stage rectifying tower is an atmospheric operation, and the pure content at the bottom of the still in the product is below 0.1%.After three grades of rectifying, the content of product lactate can reach more than 99.8%.
Material acid among the present invention can be that the lactic acid of L type also can be the lactic acid of D type.If the lactic acid that adopts the L type is as raw material, what obtain is the purified grade rac-Lactide of L type, and the finished product are lactates of L type; If the lactic acid that adopts the D type is as raw material, what obtain is the purified grade rac-Lactide of D type, and the finished product are lactates of D type.
Anhydrous organic alcohol among the present invention is anhydrous organic alcohol that methyl alcohol, ethanol, propyl alcohol, butanols, amylalcohol, hexanol, enanthol, octanol, nonyl alcohol, certain herbaceous plants with big flowers alcohol, hendecanol, dodecanol, tridecyl alcohol, cetyl alcohol, Stearyl alcohol, lauryl alcohol, Therapeutic Mineral Ice or glyceryl alcohol etc. have reactive behavior.
Compared with prior art, technical superiority of the present invention is:
1, the present invention adopts refined lactide and absolute alcohol as direct material in the middle of producing the operational path of high-optical-purity lactate; 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, and well-known; 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, and the left-handed and 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 can it be separated through 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%, and optical purity can reach more than 99.5%, and water cut 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.Therefore the water cut 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 lactate optical purity can reach more than 99.5%.
2, adopt the purifying mother liquor of rac-Lactide and the ethyl lactate that absolute ethyl alcohol is produced electronic-grade; Have following characteristics: one, purifying mother liquor and absolute ethyl alcohol are not moisture; And the transesterification reaction of being carried out can not produce reaction water; So entire reaction course need not to be with aqua, the moisture content in the product can be accomplished below the 200ppm; Two, rac-Lactide is used for the production of high-optical-purity lactate, and the purifying mother liquor is used for the production of ethyl lactate, we can say that all raw materials have all obtained effectively utilizing.
3, the present invention adopts hydrogen type cation exchange resin and SO
4 2-/ TI
2O
4The high strong acid of 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 can catalyzer be taken out through 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.
4, the present invention adopts the synthesis reactor of fixed bed as lactate, whole production can be carried out continuously, has improved the unit production capacity, and the difference between having reduced batch has guaranteed the stable of product quality.
5, separation and purification lactate of the present invention can adopt the mode of three tower continuous rectifications.Preceding two towers adopt the mode of decompression to carry out, and reduce the production temperature, have reduced side reaction odds in the more material of impurity, and the 3rd tower adopts the mode of atmospheric distillation further to remove alcohol in the product.Through three grades of rectification and purification, the content of lactate can reach more than 99.8%, and pure content can be reduced to below 0.1%.
6, operational path of the present invention is an environmental protection, pollution-free green route.One, the zero(ppm) 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 basically; 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 done further detailed description.
Embodiment one:
Raw material is that the mass content of outsourcing is 88% L-lactic acid; Adopt falling-film evaporator that material acid is carried out vacuum distilling; 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 through transferpump, in the weight ratio of zinc lactate and lactic acid be 5/10000 ratio adding zinc lactate as catalyzer, in 2 hours, material is risen to 120 ℃ from 80 ℃; Vacuum tightness maintains 5000Pa, and entire reaction is carried out having under the condition of stirring, detects the viscosity of lactic acid oligomer through in-line viscometer; According to the viscosity molecular weight contrast relationship, confirm that its molecular weight is whether between 1000～2500, if molecular weight is within this scope; Through height pressure difference and vacuum pressure reduction lact-acid oligomer being conveyed into the depolymerization still, is that 5/10000 ratio adds zinc lactate as catalyzer in the weight ratio of zinc lactate and lactic acid, and entire reaction is carried out having under the condition of stirring; Material is warming up to 180 ℃ rapidly, and 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, and the liquid lactide in the holding tank gets into purifying workshop section through transferpump, through recrystallization purifying process; Obtain refined lactide 385Kg, content reaches 99.7%, and optical purity reaches 99.7%.To make with extra care L-rac-Lactide 385Kg again and add dissolution kettle, in dissolution kettle, add anhydrous methanol 500Kg simultaneously, material will be heated to 75 ℃ through handling equipment; After treating that material dissolves fully, the operation transferpump carries out transesterification reaction with the methanol solution of rac-Lactide through the fixed-bed reactor that Zeo-karb is housed; The mother liquor that reaction is accomplished gets into surge tank, through transferpump mother liquor is imported rectifying tower continuously again, and control one-level rectifier bottoms temperature of charge is at 140 ℃～141 ℃; 65～65.5 ℃ of tower top temperatures, cat head tower bottom pressure difference is 1.8KPa, cat head continues extraction and reclaims methyl alcohol; Bottom product gets into the two-stage rectification tower, and control two-stage rectification tower bottom temperature of charge is 90～95 ℃, and tower top temperature is 65～70 ℃; Vacuum tightness-0.09MPa continues the extraction heavy constituent at the bottom of the tower, overhead product gets into third stage rectifying tower; Control tower substrate material temperature is 144～146 ℃, and cat head continues extraction and reclaims methyl alcohol, continues extraction L-methyl lactate at the bottom of the tower; Rectifying finishes, and obtains content 99.85% altogether, and optical purity is 99.9% L-methyl lactate 600Kg.The lactoyl methyl lactate can return with recovery methyl alcohol and participate in the methyl lactate building-up reactions in the methyl lactate synthesis system
Embodiment two:
D-lactic acid 5000Kg after concentrating is conveyed into polycondensation vessel through transferpump, in the weight ratio of zinc oxide and lactic acid be 10/10000 ratio adding zinc oxide as catalyzer, in 2 hours, material is risen to 120 ℃ from 80 ℃; Vacuum tightness maintains 4000Pa, and entire reaction is carried out having under the condition of stirring, detects the viscosity of lactic acid oligomer through in-line viscometer; According to the viscosity molecular weight contrast relationship, confirm that its molecular weight is 1600, polycondensation is accomplished; Through height pressure difference and vacuum pressure reduction lact-acid oligomer being conveyed into the depolymerization still, is that 10/10000 ratio adds zinc oxide as catalyzer in the weight ratio of zinc oxide and lactic acid, and entire reaction is carried out having under the condition of stirring; Material is warming up to 185 ℃ rapidly, and 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, and the liquid lactide in the holding tank gets into purifying workshop section through transferpump, through the fusion-crystallization purifying technique; Obtain refining D-rac-Lactide 3800Kg, content reaches 99.6%, and optical purity reaches 99.6%.Again refined lactide 3800Kg is added dissolution kettle through handling equipment, interpolation dry isobutanol 10000Kg in the dissolution kettle simultaneously, treat that material dissolves fully after; The operation transferpump carries out transesterification reaction with the isobutanol solution of rac-Lactide through the fixed-bed reactor that Zeo-karb is housed, and the mother liquor that reaction is accomplished gets into surge tank; Through transferpump mother liquor is imported rectifying tower continuously again, control one-level rectifier bottoms temperature of charge at 140 ℃～141 ℃, 85～85.5 ℃ of tower top temperatures; Vacuum tightness is-0.086MPa in the tower, and cat head continues extraction and reclaims isopropylcarbinol, and bottom product gets into the two-stage rectification tower; Control two-stage rectification tower bottom temperature of charge is 90～95 ℃, and tower top temperature is 65～70 ℃, vacuum tightness-0.095MPa; Continue the extraction heavy constituent at the bottom of the tower, overhead product gets into third stage rectifying tower, and control tower substrate material temperature is 160～162 ℃; Cat head continues extraction and reclaims isopropylcarbinol, continues extraction D-isobutyl lactate at the bottom of the tower, and rectifying finishes; Obtain content 99.8% altogether, optical purity is 99.9% D-isobutyl lactate 7000Kg.The lactoyl isobutyl lactate can return with the recovery isobutyl lactate and participate in the synthetic of isobutyl lactate in the isobutyl lactate synthesis system.
Embodiment three:
Rac-Lactide is reclaimed mother liquor and absolute ethyl alcohol added in the dissolution kettle, mix by weight 1: 1.6, the operation transferpump, with mixed solution with the flow velocity of 600L/h through SO is housed
4 2-/ TI
2O
4The fixed-bed reactor of the high strong acid catalyst of solid carry out transesterification reaction, and the mother liquor that reaction is accomplished gets into surge tank, through transferpump mother liquor is imported rectifying tower continuously with the flow velocity of 600L/h again; Control one-level rectifier bottoms temperature of charge at 140 ℃～141 ℃, 70～75.5 ℃ of tower top temperatures, vacuum tightness is-0.04MPa in the tower; Cat head continues extraction and reclaims ethanol, and bottom product gets into the two-stage rectification tower, and control two-stage rectification tower bottom temperature of charge is 90～95 ℃; Tower top temperature is 65～70 ℃, and vacuum tightness-0.093MPa continues the extraction heavy constituent at the bottom of the tower; Overhead product gets into third stage rectifying tower; Control tower substrate material temperature is 150～155 ℃, and cat head continues extraction and reclaims ethanol, and the flow velocity with 500L/h at the bottom of the tower continues the ethyl lactate of extraction content more than 99.85%.The lactoyl ethyl lactate can return with recovery ethanol and participate in the ethyl lactate building-up reactions in the ethyl lactate synthesis system.
Embodiment four:
Raw material is that the mass content of outsourcing is 85% L-lactic acid; Adopt falling-film evaporator that material acid is carried out vacuum distilling; 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 through transferpump, is 50/10000 ratio adding catalyzer in the weight ratio of catalyzer and lactic acid, and catalyzer is that zinc oxide, White tin oxide and butyl(tetra)titanate are by weight the mixture that is 1: 1: 1.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 through in-line viscometer,, confirm that its molecular weight is whether between 1000～2500 according to the viscosity molecular weight contrast relationship; If molecular weight is within this scope; Through height pressure difference and vacuum pressure reduction lact-acid oligomer being conveyed into the depolymerization still, is that 50/10000 ratio adds catalyzer in the weight ratio of catalyzer and lactic acid, and catalyzer is that zinc oxide, White tin oxide and butyl(tetra)titanate are by weight the mixture that is 1: 1: 1.Entire reaction is carried out having under the condition of stirring, and material is warming up to 180 ℃ rapidly, and 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, and the liquid lactide in the holding tank gets into purifying workshop section through transferpump, through recrystallization purifying process; Obtain refined lactide 385Kg, content reaches 99.7%, and optical purity reaches 99.7%.To make with extra care L-rac-Lactide 385Kg again and add dissolution kettle through handling equipment; In dissolution kettle, add anhydrous methanol 500Kg simultaneously; Material is heated to 75 ℃, treat that material dissolves fully after, the operation transferpump; The methanol solution of rac-Lactide is carried out transesterification reaction through the fixed-bed reactor that composite catalyst is housed, and composite catalyst is hydrogen type cation exchange resin and SO
4 2-/ TI
2O
4The high strong acid of solid is by weight the mixture that is 1: 2.The mother liquor that reaction is accomplished gets into surge tank, through transferpump mother liquor is imported rectifying tower continuously again, and control one-level rectifier bottoms temperature of charge is at 140 ℃～141 ℃; 65～65.5 ℃ of tower top temperatures, cat head tower bottom pressure difference is 1.8KPa, cat head continues extraction and reclaims methyl alcohol; Bottom product gets into the two-stage rectification tower, and control two-stage rectification tower bottom temperature of charge is 90～95 ℃, and tower top temperature is 65～70 ℃; Vacuum tightness-0.09MPa continues the extraction heavy constituent at the bottom of the tower, overhead product gets into third stage rectifying tower; Control tower substrate material temperature is 144～146 ℃, and cat head continues extraction and reclaims methyl alcohol, continues extraction L-methyl lactate at the bottom of the tower; Rectifying finishes, and obtains content 99.85% altogether, and optical purity is 99.9% L-methyl lactate 600Kg.The lactoyl methyl lactate can return with recovery methyl alcohol and participate in the methyl lactate building-up reactions in the methyl lactate synthesis system.
Embodiment five:
Raw material is that the mass content of outsourcing is 85% D-lactic acid; Adopt falling-film evaporator that material acid is carried out vacuum distilling; 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 through transferpump, is 20/10000 ratio adding catalyzer in the weight ratio of catalyzer and lactic acid, and catalyzer is that zinc lactate, propionic acid and butyl(tetra)titanate are by weight the mixture that is 1: 1: 1.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 through in-line viscometer,, confirm that its molecular weight is whether between 1000～2500 according to the viscosity molecular weight contrast relationship; If molecular weight is within this scope; Through height pressure difference and vacuum pressure reduction lact-acid oligomer being conveyed into the depolymerization still, is that 50/10000 ratio adds catalyzer in the weight ratio of catalyzer and lactic acid, and catalyzer is that zinc lactate, propionic acid and butyl(tetra)titanate are by weight the mixture that is 1: 1: 1.Entire reaction is carried out having under the condition of stirring, and material is warming up to 180 ℃ rapidly, and 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, and the liquid lactide in the holding tank gets into purifying workshop section through transferpump, through recrystallization purifying process; Obtain refined lactide 385Kg, content reaches 99.7%, and optical purity reaches 99.7%.To make with extra care L-rac-Lactide 385Kg again and add dissolution kettle through handling equipment; In dissolution kettle, add anhydrous methanol 500Kg simultaneously; Material is heated to 75 ℃, treat that material dissolves fully after, the operation transferpump; The methanol solution of rac-Lactide is carried out transesterification reaction through the fixed-bed reactor that composite catalyst is housed, and composite catalyst is hydrogen type cation exchange resin and SO
4 2-/ TI
2O
4The high strong acid of solid is by weight the mixture that is 1: 2.The mother liquor that reaction is accomplished gets into surge tank, through transferpump mother liquor is imported rectifying tower continuously again, and control one-level rectifier bottoms temperature of charge is at 140 ℃～141 ℃; 65～65.5 ℃ of tower top temperatures, cat head tower bottom pressure difference is 1.8KPa, cat head continues extraction and reclaims methyl alcohol; Bottom product gets into the two-stage rectification tower, and control two-stage rectification tower bottom temperature of charge is 90～95 ℃, and tower top temperature is 65～70 ℃; Vacuum tightness-0.09MPa continues the extraction heavy constituent at the bottom of the tower, overhead product gets into third stage rectifying tower; Control tower substrate material temperature is 144～146 ℃, and cat head continues extraction and reclaims methyl alcohol, continues extraction L-methyl lactate at the bottom of the tower; Rectifying finishes, and obtains content 99.85% altogether, and optical purity is 99.9% L-methyl lactate 600Kg.The lactoyl methyl lactate can return with recovery methyl alcohol and participate in the methyl lactate building-up reactions in the methyl lactate synthesis system.
Claims (13)
1. the method for continuous production high-content and high-optical-purity lactate, it may further comprise the steps:
A, lactic acid polycondensation: in lactic acid, add catalyzer, the weight ratio of catalyzer and lactic acid is 0.1/10000～100/10000, carries out polycondensation after adding, and obtains viscosity molecular weight at 1000～2500 lactic acid oligomer;
B, oligopolymer depolymerization: in lactic acid oligomer, add catalyzer, the weight ratio of catalyzer and lactic acid oligomer is 0.1/10000～100/10000, 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 at refined lactide more than 99.5% and acyl lactylates purifying mother liquor;
D, high-optical-purity lactate are synthetic: with refined lactide and the ratio adding dissolution kettle of anhydrous organic alcohol by weight 1: 0.7～1: 5; Rac-Lactide is dissolved in organic alcohol fully; Then with the alcoholic solution of rac-Lactide through the fixed-bed reactor of catalyzer are housed; Transesterification reaction takes place in rac-Lactide and organic alcohol, obtains lactate.
2. the method for a kind of continuous production high-content according to claim 1 and high-optical-purity lactate, it may further comprise the steps:
E, electronic-grade ethyl lactate synthetic: with acyl lactylates purifying mother liquor and absolute ethyl alcohol by weight 1: 0.7～1: 5 mixed even, through the fixed-bed reactor of catalyzer are housed, obtain ethyl lactate then.
F, lactate purifying: lactate is carried out purifies and separates.
3. the method for a kind of continuous production high-content according to claim 1 and high-optical-purity 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.
4. the method for a kind of continuous production high-content according to claim 1 and high-optical-purity lactate; Wherein: the catalyzer that in lactic acid polycondensation and oligopolymer depolymerization, adds is at least a in zinc class catalyzer, tin class catalyzer, titanium class catalyzer or the organic acid catalyzer, and the weight ratio of its adding is 50/10000.
5. according to the method for claim 1 or 4 described a kind of continuous production high-contents and high-optical-purity lactate, wherein: the catalyzer that in lactic acid polycondensation and oligopolymer depolymerization, adds is one or more the composite catalyst in zinc lactate, zinc oxide, zinc powder, zinc ethyl, lactic acid tin, White tin oxide, tindioxide, tin protoxide, the inferior tin of lactic acid, stannous octoate, tin protochloride, glass putty, propionic acid or the butyl(tetra)titanate.
6. the method for a kind of continuous production high-content according to claim 5 and high-optical-purity lactate, wherein: the catalyzer that in lactate synthetic fixed-bed reactor, adds is hydrogen type cation exchange resin or SO
4 2-/ TI
2O
4The composite catalyst of one or both in the high strong acid catalyst of solid.
7. the method for a kind of continuous production high-content according to claim 1 and high-optical-purity lactate, wherein: be used for lactate synthetic fixed-bed reactor and be single slage fixed bed reactor drum or by two and two multi-stage type fixed-bed reactor that above calandria type fixed bed reactor series connection forms.
8. the method for a kind of continuous production high-content according to claim 1 and high-optical-purity lactate; 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.
9. the method for a kind of continuous production high-content according to claim 1 and high-optical-purity lactate; Wherein: in the step F lactate is carried out purifies and separates and adopt three grades of rectification process, first step rectifying tower removes alcohol excess, and second stage rectifying tower removes acyl lactylates; Third stage rectifying tower removes remaining alcohol; First step rectifying tower is a decompression operation, operation vacuum tightness is-0.02～-0.08MPa, the pure content in the bottoms material is 1～5%; Second stage rectifying tower is a decompression operation, operation vacuum tightness is-0.086～-0.098MPa, the lactate content in the bottoms material is 5%～20%; Third stage rectifying tower is an atmospheric operation, and the pure content at the bottom of the still in the product is below 0.1%, and after three grades of rectifying, the content of product lactate reaches more than 99.8%.
10. the method for a kind of continuous production high-content according to claim 9 and high-optical-purity lactate, wherein: the lactoyl lactate that overflows at the bottom of the second stage rectifying Tata is returned participate in the lactate building-up reactions in the reaction kettle of step D.
11. the method for a kind of continuous production high-content according to claim 9 and high-optical-purity lactate, wherein: the recovery alcohol that the first step and second stage rectifying tower cat head are obtained returns the dissolving of participating in rac-Lactide in the dissolution kettle of step D.
12. the method for a kind of continuous production high-content according to claim 1 and high-optical-purity lactate, wherein: described material acid is the lactic acid of L type or the lactic acid of D type.
13. the method for a kind of continuous production high-content according to claim 1 and high-optical-purity lactate, wherein: described anhydrous organic alcohol is methyl alcohol, ethanol, propyl alcohol, butanols, amylalcohol, hexanol, enanthol, octanol, nonyl alcohol, certain herbaceous plants with big flowers alcohol, hendecanol, dodecanol, tridecyl alcohol, cetyl alcohol, Stearyl alcohol, lauryl alcohol, Therapeutic Mineral Ice or glyceryl alcohol.
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