CN113677689A

CN113677689A - Method for purifying sucralose-6-ester

Info

Publication number: CN113677689A
Application number: CN202180002111.4A
Authority: CN
Inventors: 杨志健; 陈永乐; 慈昊; 仇鑫
Original assignee: Anhui Jinhe Industrial Co Ltd
Current assignee: Anhui Jinhe Industrial Co Ltd
Priority date: 2021-07-07
Filing date: 2021-07-07
Publication date: 2021-11-19
Anticipated expiration: 2041-07-07
Also published as: WO2023279278A1; CN113677689B

Abstract

The application provides a method for purifying sucralose-6-ester, which comprises the following steps: a concentration step: concentrating the mother liquor to be purified to remove the organic solvent, and after the concentration is finished, adding water into the mother liquor to form an aqueous solution to be purified; an oxidation step: sequentially adding an oxidant and a decolorizing agent into the aqueous solution to be purified to perform oxidation and decolorization reaction, and then adding an alkaline hydrolysis agent to oxidize target impurities into sucralose-6-ester and remove colored impurities; after reacting for a period of time, carrying out solid-liquid separation to obtain solid waste and first filtrate; and a crystallization step: and adjusting the first filtrate to be neutral, adding an extracting agent, and simultaneously extracting and crystallizing to obtain a sucralose-6-ester crude product and a second filtrate. The method has the advantages that the impurity content is effectively removed, and meanwhile, the yield of the target product is greatly improved; the integral treatment process is simple, the economic cost is low, and the practicability is strong; and can obviously reduce the COD content of the wastewater.

Description

Method for purifying sucralose-6-ester

Technical Field

The invention belongs to the technical field of fine chemical engineering, and particularly relates to a method for purifying sucralose-6-ester.

Background

Sucralose-6-ester is one of the main intermediates for synthesizing sucralose, and can be obtained by esterifying, chlorinating and removing ester group from sucrose. The traditional green chlorination process is that sucrose-6-ester is prepared by chlorination at high temperature by thionyl chloride under the condition that N, N-Dimethylformamide (DMF) and trichloroethane are taken as solvents. The dosage of thionyl chloride which is a chlorination reagent is far higher than the equimolar dosage of theoretical chlorination, and the chlorination temperature is higher (higher than 100 ℃), so that the obtained chlorination liquid has more impurities. Taking the esterifying agent as acetic acid as an example, besides the target product of the tri-filtered sucrose-6-ethyl ester, a large amount of sucralose diester, tetrachlorosucrose-6-ethyl ester, a small amount of monochloro sucrose-6-ethyl ester, dichlorosucrose-6-ethyl ester and the like exist. In order to prepare pure sucralose, it is often necessary to purify sucralose-6-ethyl ester by multiple steps to obtain a refined sucralose-6-ethyl ester product, then hydrolyze the refined sucralose-6-ethyl ester product with methanol/sodium methoxide, and then purify the refined sucralose product.

In the prior art, the purification method of sucralose-6-ethyl ester belongs to a conventional purification mode. For example, CN 11056780, which uses organic base as neutralizer, and after concentrating to prepare aqueous solution, it uses solvents such as ethyl acetate, butyl acetate, methyl chloride, chlorobenzene, etc. to perform extraction crystallization. On one hand, the weak-alkaline long-chain organic alkali is not suitable for neutralizing the chlorination solution, on the other hand, the extraction is carried out by adopting dichloromethane, trichloromethane, chlorobenzene or methyl tert-butyl ether, and the sucralose-6-ethyl ester has low solubility in the above solvents and low extraction efficiency, so the application prospect is small.

For another example, the method is disclosed in Chinese patent CN108191927, in which organic solvent I is adopted for dissolution and crystallization, then organic solvent II is adopted for dissolution and crystallization, and concentrated dilute sulfuric acid is added for carbonization treatment. In the first crystallization process, because the coating property of the concentrated viscous sugar liquid is strong, the sucralose-6-ethyl ester cannot be efficiently dissolved by simply adding the organic solvent I, and the sugar residue is carbonized by adopting concentrated dilute sulfuric acid and the organic solvent II, the residual sucralose-6-ethyl ester in the sugar residue and impurities capable of being converted into the sucralose-6-ethyl ester are wasted, which has an influence on the economic value of the process.

Patent CN103012509 carries out salting-out purification of sucralose-6-ethyl ester by adding inorganic salt, the addition is 6-12 wt% of mother liquor, and no matter whether the process can take out sucralose-6-ethyl ester from chlorination reaction neutralization solution completely, high-salinity wastewater with extremely high salt content which needs to be treated subsequently seriously affects the practical value of the patent.

In addition, the purification methods of sucralose-6-ethyl ester, as reported in Chinese patent CN101941995, Chinese patent CN106589013 and the like, are conventional extraction and crystallization.

In summary, in the prior art, the purification of sucralose-6-ester is the traditional concept of separating impurities from a chlorination solution, and this method has the defects of high energy consumption, low efficiency, large amount of waste liquid generation, low economic value and the like, and the yield of sucralose-6-ester is low, so a method for purifying sucralose-6-ester is urgently needed to solve the above problems.

Disclosure of Invention

In view of the prior art, the present application is proposed to provide a method for purifying sucralose-6-ester, which overcomes the above problems or at least partially solves the above problems, such as high energy consumption, low efficiency, large amount of waste liquid generation, low economic value, and low yield of sucralose-6-ester.

According to a first aspect of the present application, there is provided a method of purifying sucralose-6-ester, comprising:

a concentration step: concentrating the mother liquor to be purified to remove the organic solvent, and after the concentration is finished, adding water into the mother liquor to form an aqueous solution to be purified; wherein, mother liquor to be purified is obtained by preparing reaction liquid of sucralose-6-ester through esterification and chlorination reaction of neutralized sucralose;

an oxidation step: sequentially adding an oxidant and a decolorizing agent into the aqueous solution to be purified to perform oxidation and decolorization reaction, and then adding an alkaline hydrolysis agent into the aqueous solution to be purified to oxidize target impurities into sucralose-6-ester and remove colored impurities; after reacting for a period of time, carrying out solid-liquid separation to obtain solid waste and first filtrate; and

a crystallization step: and adjusting the first filtrate to be neutral, adding an extracting agent, and simultaneously extracting and crystallizing to obtain a sucralose-6-ester crude product and a second filtrate.

Optionally, the method further includes:

a filtrate recovery step: layering the second filtrate to obtain a first organic phase and a first water phase, evaporating the first organic phase to remove the extracting agent to obtain sugar residue, adding water for dissolution, and performing solid-liquid separation to obtain a sugar residue aqueous solution;

mixing the aqueous solution of the sugar residues with the first aqueous phase, adding an extracting agent for extraction, and recycling a second organic phase obtained by extraction into the first filtrate to be subjected to the crystallization step.

Optionally, in the method, in the step of recovering the filtrate, the ratio of the mass of the added water to the mass of the first organic phase is 0.5-2: 1, the dissolving temperature of the solution is 40-70 ℃, and the dissolving time is 0.5-2 hours;

the ratio of the volume usage of the extracting agent to the total volume of the sugar residue water solution and the first water phase is 0.1-1: 1.

Optionally, the method further includes:

refining: dissolving the obtained crude sucralose-6-ester product in an extracting agent, and performing primary crystallization and separation to obtain an intermediate crystal and a third filtrate;

dissolving the obtained intermediate crystal in water, and performing secondary crystallization and separation to obtain a sucralose-6-ester refined product and a fourth filtrate.

Optionally, the method further includes:

recovering the third filtrate into the second filtrate to be subjected to the filtrate recovery step;

the fourth filtrate is recycled to the mother liquor to be purified which is to be subjected to the concentration step.

Optionally, in the method, in the refining step, the mass ratio of the mass usage of the extracting agent to the mass of the sucralose-6-ester crude product is 2-5: 1; the crystallization temperature of the first crystallization is-5-10 ℃, and the crystallization time is 0.5-3 h;

the mass ratio of the water to the intermediate crystals is 2-5: 1; the crystallization temperature of the second crystallization is 0-30 ℃, and the crystallization time is 1-5 h.

Optionally, in the above method, in the concentration step, the concentration temperature is 60-80 ℃, and the vacuum degree is-0.1 to-0.05 Mpa;

the preparation volume of the aqueous solution to be purified is 0.5-1 time of the volume of the mother liquor to be purified.

Optionally, in the above method, in the oxidizing step, the oxidizing agent is one of sodium hypochlorite, sodium chlorate and calcium hypochlorite, preferably sodium hypochlorite;

the dosage of the oxidant is 1-1.5 times of the total mass of the target impurities in the mother liquor to be purified.

Optionally, in the above method, in the oxidation step, the decolorizing agent is one or more of activated carbon, attapulgite, diatomaceous earth and activated clay, preferably activated carbon;

the dosage of the decoloring agent is 0.05-0.2 wt% of the aqueous solution to be purified;

the temperature of the oxidation decoloration reaction is 40-60 ℃, and the reaction time is 1-4 h.

Optionally, in the above method, in the oxidizing step, the alkaline hydrolysis agent is ammonia water or NaOH, preferably ammonia water;

the amount of alkaline hydrolysis agent is based on the adjustment of the pH value of the aqueous solution to be purified to 8.5-10.5.

Optionally, in the above method, adjusting the first filtrate to neutrality in the crystallization step comprises:

adjusting the pH value of the first filtrate to 6.5-8.0 by adopting an acidic substance; wherein the acidic substance is dilute hydrochloric acid or dilute sulfuric acid, preferably dilute hydrochloric acid.

Optionally, in the above method, in the crystallization step, the extractant is one or more of methyl acetate, ethyl acetate, propyl acetate, isopropyl acetate, butyl acetate and isobutyl acetate, preferably ethyl acetate;

the volume ratio of the volume usage of the extracting agent to the volume of the aqueous solution to be purified is 1: 1-3;

the crystallization temperature is-10 ℃, and the crystallization time is 6-12 h.

The method has the beneficial effects that the chlorination reaction neutralizing liquid for preparing the sucralose-6-ester is treated by combining the oxidant and the alkaline hydrolysis agent so as to convert impurities of the sucralose diester and the tetrachlorosucrose-6-ester into the target product sucralose-6-ester, so that the impurity content is effectively removed, and the yield of the target product is greatly improved; the whole treatment process is simple and smooth, the economic cost is low, and the practicability is strong; the purity of the obtained sucralose-6-ester is high, and the production activity of sucralose can be directly carried out; the method can obviously reduce the impurity content of the wastewater, relieves the pressure of subsequent wastewater treatment, is environment-friendly and has extremely high application and economic values.

The foregoing description is only an overview of the technical solutions of the present application, and the present application can be implemented according to the content of the description in order to make the technical means of the present application more clearly understood, and the following detailed description of the present application is given in order to make the above and other objects, features, and advantages of the present application more clearly understandable.

Drawings

The accompanying drawings, which are included to provide a further understanding of the application and are incorporated in and constitute a part of this application, illustrate embodiment(s) of the application and together with the description serve to explain the application and not to limit the application. In the drawings:

FIG. 1 shows a schematic flow diagram of a method for purifying sucralose-6-ester according to one embodiment of the present application;

FIG. 2 shows a schematic diagram of an apparatus for purifying sucralose-6-ester according to one embodiment of the present application;

wherein V-1 is a desolventizing kettle; v-2 is an oxidation kettle; v-3 is a neutralization kettle; v-4 is a crystallization kettle; v-5 is a phase splitter; v-6 is a deesterification kettle; v-7 is an extraction kettle; v-8 is an ester crystallization kettle; v-9 is a water crystallization kettle; e-1, E-2, E-3 and E-4 are plate and frame filter presses.

Detailed Description

Exemplary embodiments of the present application will be described in more detail below. While exemplary embodiments of the present application have been illustrated, it should be understood that the present application may be embodied in various forms and should not be limited by the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art.

The conception of the application lies in that aiming at the technical defects that in the prior art, the sucralose-6-ethyl ester purification process has high energy consumption, low efficiency, large amount of waste liquid generation, high difficulty in waste liquid treatment, low economic value and the like, and the yield of the sucralose-6-ethyl ester is low, the method for converting the sucralose diester and the tetrachlorosucrose-6-ester in the chlorination neutralization solution into the sucralose-6-ester so as to improve the yield of the target product is provided.

Fig. 1 shows a schematic flow diagram of a method for purifying sucralose-6-ester according to an embodiment of the present application, and as can be seen from fig. 1, the present application at least includes steps S110 to S130.

A concentration step S110: concentrating the mother liquor to be purified to remove the organic solvent, and after the concentration is finished, adding water into the mother liquor to form an aqueous solution to be purified; wherein, the mother liquor to be purified is obtained by preparing reaction liquid of sucralose-6-ester through esterification and chlorination reaction of neutralized sucralose.

The mother liquor to be purified in the application refers to chlorination reaction liquid of sucrose-6-ester, namely reactant mixed solution obtained by chlorination reaction of sucrose-6-carboxylate and a chlorination reagent, and further, the reactant mixed solution can be adjusted to be neutral by adopting the reagent, and is called chlorination reaction neutralization liquid. The method is suitable for reaction liquid generated in the chlorination reaction stage in the preparation of sucralose by various methods in the prior art, such as a single-group protection method, a multi-group protection method and the like, the source of the sucrose-6-carboxylate chlorination reaction liquid is not limited by the method, and the method can be used for the reaction liquid generated in the chlorination reaction stage in the preparation of sucralose in a laboratory or industrial production.

Since strong chlorinating agents such as thionyl chloride and phosgene are used in the chlorination reaction process, a series of byproducts such as monochlorosucrose-6-carboxylate, dichlorosucrose-6-carboxylate, tetrachlorosucrose-6-carboxylate, sucralose diester and the like are generated due to high temperature in the chlorination incubation stage, and organic impurities such as N, N-Dimethylformamide (DMF) and trichloroethane are also contained, and a large amount of water is also contained. At present, in the prior art, sodium hydroxide, ammonia water or ammonia gas is generally adopted for neutralizing the sucrose-6-carboxylate chlorination reaction liquid, but the product sucralose-6-carboxylate in an alkaline solution not only causes the hydrolysis reaction of the sucralose-6-carboxylate to generate byproducts, but also reduces the yield of the sucralose-6-carboxylate; and the process is complex, the energy consumption is high, the efficiency is low, a large amount of waste liquid is generated, and the economic value is low.

Firstly, the mother liquor to be purified is concentrated to remove the organic solvent, and after the concentration is finished, water is added into the mother liquor to be purified to form the aqueous solution to be purified.

The concentration can be carried out by any of the techniques known in the art, such as distillation, in which part of the water, organic impurities, such as DMF and trichloroethane, etc., can be evaporated and the evaporated material can be recovered as solvent.

After the mother liquor to be purified is concentrated, the viscosity of the mother liquor to be purified is relatively high, and the mother liquor to be purified is preferably prepared into an aqueous solution for facilitating subsequent treatment.

An oxidation step S120: sequentially adding an oxidant and a decolorizing agent into the aqueous solution to be purified to perform oxidation and decolorization reaction, and then adding an alkaline hydrolysis agent into the aqueous solution to be purified to oxidize target impurities into sucralose-6-ester and remove colored impurities; after reacting for a period of time, performing solid-liquid separation to obtain solid waste and a first filtrate.

The applicant finds that the chlorination reaction neutralization solution contains more sucralose diester, tetrachlorosucrose-6-ethyl ester and less monochloro sucrose-6-ethyl ester and dichlorosucrose-6-ethyl ester besides the target product sucralose-6-ethyl ester through component analysis of the chlorination reaction neutralization solution. Researches show that the sucralose diester and the tetrachlorosucrose-6-ethyl ester can be selectively oxidized to obtain the target product sucralose-6-ethyl ester, so that the impurities are removed, and the yield of the target product sucralose-6-ethyl ester is improved.

After the oxidant is added, a decolorizing agent can be added, the oxidation reaction and the decolorizing reaction can be carried out simultaneously, the sucralose-6-ethyl ester is prepared by adopting sucrose as a raw material, side reaction can occur among the sucrose in the reaction process, sucrose molecules can be polymerized and coked to form colored impurities, and the colored impurities can be removed by the decolorizing agent.

After the oxidative decoloring reaction is performed for a certain period of time, an alkaline hydrolyzing agent is added thereto. After the oxidant is added, on one hand, the pH value of the whole aqueous solution to be purified can be changed, and particularly, an acid environment can be formed; on the other hand, the target impurities sucralose diester and tetrachlorosucrose-6-ester and hypochlorite will form corresponding complex intermediates. At this time, alkaline substances such as ammonia water are adopted to adjust the pH value to 8.5-10.5, because the compound intermediate formed by the oxidant and the target impurities of the sucralose diester and the tetrachlorosucrose-6-ester needs the alkaline substances to neutralize the groups to be removed, and then the target product of the sucralose-6-ester can be formed.

Taking sodium hypochlorite as an oxidant and ammonium hydroxide as an alkaline hydrolysis agent as an example, the chemical reaction formulas of impurities of sucralose diester and tetrachlorosucrose-6-ester and hypochlorite to be converted into the target product of sucralose-6-ester are as follows:

as can be seen from the chemical reaction formula, the reaction of the oxidizing agent to the sucralose diester in the presence of the alkaline hydrolysis agent is to selectively remove ester groups to generate sucralose-6-ester; the reaction of the oxidant to the tetrachloro sucrose-6-ester is to selectively remove one chlorine atom to generate the trichlorosucrose-6-ester.

After reacting for a period of time, performing solid-liquid separation to obtain solid waste and a first filtrate. If the filtrate is subjected to vacuum filtration, the decolorizing agent is separated from the filtrate, colored impurities are adsorbed in the decolorizing agent, the decolorizing agent can be regenerated and the waste can be treated, and the obtained filtrate is recorded as first filtrate.

And a crystallization step S130: and adjusting the first filtrate to be neutral, adding an extracting agent, and simultaneously extracting and crystallizing to obtain a sucralose-6-ester crude product and a second filtrate.

After the oxidative decoloration reaction in the aqueous solution to be purified, the acidity or basicity thereof is affected, and the obtained first filtrate is basic and is preferably adjusted to be neutral before the crystallization. In the present application, the term "neutral" is not a condition that the pH is absolutely equal to 7, but is considered to be neutral when the pH is about 7, for example, the pH is in the range of 6 to 8.

In the present application, during crystallization, an extractant is added, i.e. crystallization is carried out while extraction, and the extractant is mainly used for extracting organic esters which can not be converted into target products, and mainly comprises monochloro sucrose-6-ester and dichloro sucrose-6-ester. If extraction is performed before crystallization, the extractant can bring out part of the target product sucralose-6-ester, and the yield of the sucralose-6-ester is influenced.

And after the crystallization is finished, carrying out solid-liquid separation to obtain a sucralose-6-ester crude product and a filtrate, and marking the filtrate as a second filtrate.

As can be seen from the method shown in FIG. 1, the chlorination neutralizing solution of sucralose-6-ester is treated by combining an oxidizing agent and an alkaline hydrolysis agent to convert the impurities of sucralose diester and tetrachlorosucrose-6-ester into the target product sucralose-6-ester, so that the yield of the target product is greatly improved while the impurity content is effectively removed; the integral treatment process is simple, the economic cost is low, and the practicability is strong; and the COD (chemical oxygen demand) content of the wastewater can be obviously reduced, the pressure of subsequent wastewater treatment is relieved, and the method has extremely high application and economic values.

In some embodiments of the present application, the method further comprises: a filtrate recovery step: layering the second filtrate to obtain a first organic phase and a first water phase, evaporating the first organic phase to remove the extracting agent to obtain sugar residue, adding water for dissolution, and performing solid-liquid separation to obtain a sugar residue aqueous solution; mixing the aqueous solution of the sugar residues with the first aqueous phase, adding an extracting agent for extraction, and recycling a second organic phase obtained by extraction into the first filtrate to be subjected to the crystallization step.

In the second filtrate, a part of the target product is remained and not crystallized, and the part of the filtrate can be recovered and reprocessed to improve the yield of the sucralose-6-ester.

Specifically, the second filtrate can be subjected to layering to be divided into a first organic phase and a first water phase, most of the sucrose-6-ester is dissolved in the water phase, a small part of the sucrose-6-ester is distributed in the organic phase, the first organic phase is evaporated to remove the extracting agent, the extracting agent can be recycled, the evaporated organic phase forms sugar residue, the sugar residue is a relatively viscous but still fluid mixture, and the mixture contains a small amount of water, DMF, trichloroethane, the target product sucralose-6-ester, organic ester impurities with a structure similar to that of the sucralose-6-ester, some insoluble substances and the like.

Dissolving the sugar residue in water under stirring, performing solid-liquid separation after dissolution, and treating insoluble substance as waste. Mixing the sugar residue aqueous solution and the first water, adding an extracting agent, dissolving most of the target product sucralose-6-ester and organic ester impurities with a structure similar to that of the sucralose-6-ester by the extracting agent, further, independently crystallizing the part of extract to obtain the target product sucralose-6-ester, or mixing the part of extract into the first filtrate to be subjected to the crystallization step, and extracting and crystallizing the first filtrate together with the original first filtrate to obtain the sucralose-6-ester.

In some embodiments of the present application, the method further comprises: refining: dissolving the obtained crude sucralose-6-ester product in an extracting agent, and performing primary crystallization and separation to obtain an intermediate crystal and a third filtrate; dissolving the obtained intermediate crystal in water, and performing secondary crystallization and separation to obtain a sucralose-6-ester refined product and a fourth filtrate.

Through the primary crystallization step, the obtained sucralose-6-ester has low purity, and the sucralose-6-ester with higher purity can be obtained through a recrystallization method.

The application recommends a method for combining extraction crystallization and water crystallization, and specifically, dissolving an obtained sucralose-6-ester crude product in an extracting agent, carrying out primary crystallization, and carrying out solid-liquid separation after crystallization to obtain an intermediate crystal and a third filtrate; and dissolving the obtained intermediate crystal in water, performing secondary crystallization, and performing solid-liquid separation after crystallization to obtain a sucralose-6-ester refined product and a fourth filtrate.

The solubility of the sucralose-6-ester in the extractant is greater than that in water, so that the purity of the sucralose-6-ester can be obviously improved by extraction crystallization, and then the purity of the sucralose-6-ester can be further improved by water crystallization, and the yield of the sucralose-6-ester can be maintained. The sucralose-6-ester refined product with high purity is obtained by recrystallizing the crude sucralose-6-ester product.

In some embodiments of the present application, the method further comprises: recovering the third filtrate into the second filtrate to be subjected to the filtrate recovery step; the fourth filtrate is recycled to the mother liquor to be purified which is to be subjected to the concentration step.

Since sucralose-6-ester has a high solubility in the extractant, part of the sucralose-6-ester still remains in the third filtrate, and therefore it is necessary to recover the sucralose-6-ester, and the third filtrate can be directly fed into the second filtrate of the filtrate recovery step to be extracted and recovered together with the second filtrate.

The fourth filtrate, commonly called the mother liquor of water crystallization, likewise, in which a portion of sucralose-6-ester still remains, is necessarily recovered, and since the mother liquor of water crystallization is an aqueous solution, it can be directly recovered into the mother liquor to be purified which enters the concentration step.

By recycling the second filtrate, the third filtrate and the fourth filtrate, a circulating closed loop is formed in the whole treatment process, and the filtrates of the target product which may be contained are recycled, so that the treatment process is greatly simplified, the loss of the target product sucralose-6-ester is avoided, and the yield of the sucralose-6-ester is improved.

Since the processes such as distillation and extraction according to the present application require time and energy, and the addition of a solvent affects the effect of crystallization, conditions of each step of purification are searched below.

Conditions for treating the second filtrate

In some embodiments of the application, in the filtrate recovery step, the sugar residue dissolution condition is not limited, and it is only required to ensure that the sugar residue is completely dissolved; in other embodiments of the present application, the dissolving temperature of the sugar residue can be set to 40-70 ℃, and the dissolving time can be set to 0.5-2 hours, under which the soluble part in the sugar residue can be completely dissolved.

In some embodiments of the present application, the ratio of the added mass of water to the mass of the first organic phase is 0.5-2: 1, if the added mass of water is less than 0.5 times the mass of the first organic phase, the added mass of water is too small, and sugar residue is difficult to dissolve, and if the added mass of water is more than 2.0 times the mass of the first organic phase, the added mass of water is too large, which is not favorable for subsequent extraction and crystallization.

In some embodiments of the present application, the ratio of the volume usage of the extraction agent to the total volume of the aqueous bagasse solution and the first aqueous phase is 0.1-1: 1. If the volume consumption of the extracting agent is less than 0.1 time of the total volume of the sugar residue aqueous solution and the first water phase, a good extracting effect cannot be achieved; if the volume consumption of the extracting agent is more than 1 time of the total volume of the sugar residue aqueous solution and the first water phase, the extracting effect cannot be further improved, the waste of the extracting agent is caused, and other beneficial effects cannot be brought.

Conditions of the refining step

In some embodiments herein, the conditions in the refining step are not limited as long as sucralose-6-ester can be crystallized out.

In other embodiments, in the extraction crystallization process, the mass ratio of the mass usage of the extracting agent to the mass of the sucralose-6-ester crude product is 2-5: 1; the crystallization temperature of the first crystallization is-5-10 ℃, and the crystallization time is 0.5-3 h; under the above conditions, a relatively desirable crystallization effect can be achieved.

In the water crystallization process, the mass ratio of the water to the mass of the intermediate crystals is 2-5: 1; the crystallization temperature of the second crystallization is 0-30 ℃, and the crystallization time is 1-5 h; under the above conditions, a relatively desirable crystallization effect can be achieved.

Conditions of the concentration step

In some embodiments of the present application, the concentration conditions of the aqueous solution to be purified are not limited, and in other embodiments, the concentration temperature is 60 to 80 ℃ and the vacuum degree is-0.1 to-0.05 Mpa in the concentration step, considering economic and time factors.

In addition, the configuration volume of the aqueous solution to be purified is 0.5-1 time of the volume of the mother solution to be purified, namely, the volume of the aqueous solution to be purified is preset in advance, and the volume of the mother solution to be purified is supplemented to the configuration volume value of the aqueous solution to be purified by adding water no matter how much liquid is evaporated from the mother solution to be purified in the concentration step, so that ideal extraction and crystallization effects can be achieved.

The type and amount of the oxidizing agent

In some embodiments of the application, the oxidant is screened, and when the oxidant is screened, it is found that when two conventional oxidants including hydrogen peroxide and ozone are selected for oxidation, if the addition amount is unreasonable to control, the target product sucralose-6-ethyl ester is easily oxidized. In addition, peroxide is easily formed in the system due to the addition of hydrogen peroxide, and the explosion danger is easily caused under the conditions that the peroxide is more and the stirring and the temperature reduction cannot be ensured.

Through repeated researches, the inventor finds that when the oxidant is one of sodium hypochlorite, sodium chlorate and calcium hypochlorite, the selective oxidation is better, and particularly, the sodium hypochlorite can achieve the optimal selective oxidation effect, namely, sucralose diester and tetrachlorosucrose-6-ester can be oxidized into sucralose-6-ester, and the sucralose-6-ester can be further oxidized. The inventor also finds that when the using amount of the oxidant is 1-1.5 times of the total mass of the sucralose diester and the tetrachlorosucrose-6-ester in the mother liquor to be purified, a more ideal effect can be achieved.

The kind and amount of decolorizing agent

In some embodiments of the present application, the type and amount of the decolorizing agent is not limited, in other embodiments, the decolorizing agent is one or more of activated carbon, attapulgite, diatomaceous earth, and activated clay, and in still other embodiments, the decolorizing agent is activated carbon. The decolorant is a solid decolorant and can well adsorb colored impurities formed by polymerization of sucrose.

In some embodiments of the present application, the amount of the decoloring agent is not limited, and in other embodiments, the amount of the decoloring agent is 0.05 to 0.2 wt% of the aqueous solution to be purified. Because the content of colored impurities is relatively low, the usage of the decoloring agent is recommended to be 0.05-0.2 wt% of the aqueous solution to be purified from the economic point of view.

In some embodiments of the present application, the temperature and time of the oxidation decoloring reaction are not limited, and the range of the oxidation reaction in the prior art can be referred to ensure that the reaction is complete; in other embodiments, the temperature of the oxidation decoloring reaction is 40-60 ℃, and the reaction time is 1-4 h; if the reaction temperature is less than 40 ℃ and the reaction time is shorter than 1h, the reaction conditions are mild, and the problem of incomplete oxidation reaction is easy to occur; if the reaction temperature is higher than 60 ℃ and the reaction time is longer than 4 hours, excessive reaction may occur, and even sucralose-6-ester may be oxidized together.

The kind and amount of alkaline hydrolysis agent

In some embodiments of the present application, the alkaline hydrolysis agent is not limited, and any alkaline substance may be used, in other embodiments, the alkaline hydrolysis agent is ammonia water or NaOH, and in still other embodiments, the alkaline hydrolysis agent is ammonia water.

In some embodiments of the present application, the amount of alkaline hydrolysis agent is not limited and may be used to achieve an alkaline environment, and in other embodiments, the amount of alkaline hydrolysis agent is used to adjust the pH of the aqueous solution to be purified to 8.5 to 10.5.

pH value adjusting conditions

In some embodiments of the present application, the condition for adjusting the first filtrate to be neutral is not limited, and the first filtrate is neutralized by an acidic substance.

The acidic substance is a common agent for adjusting pH, such as dilute hydrochloric acid or dilute sulfuric acid, and in some embodiments, dilute hydrochloric acid can be used.

The kind and amount of the extractant

In some embodiments of the present application, the type and amount of the extractant is not limited, and any extractant can be used as long as it can effectively dissolve esters such as monochlorosucrose-6-ester, dichlorosucrose-6-ester, and the like. In other embodiments of the present application, the extractant is one or a mixture of methyl acetate, ethyl acetate, propyl acetate, isopropyl acetate, butyl acetate, and isobutyl acetate, and in still other embodiments is ethyl acetate. The sucralose-6-ester as the target product and the monochloro sucrose-6-ester, dichlorosucrose-6-ester, sucralose diester and tetrachlorosucrose-6-ester as impurities can be dissolved in the esters and water, but the solubility in the extractant is higher than that in water, so that part of organic ester impurities in the target product can be extracted from the target product to improve the purity of the sucralose-6-ester as the target product. It should be noted here that during the extraction process, a very small portion of the target sucralose-6-ester is also carried away by the extractant.

In some embodiments of the present application, the amount of the extractant is not limited, and the extraction requirement can be satisfied, and in other embodiments, the ratio of the volume amount of the extractant to the volume of the aqueous solution to be purified is 1: 1-3 for economic reasons.

Conditions of crystallization

In the present application, extraction and crystallization are performed simultaneously, and sucralose-6-ester is an intermediate for the preparation of sucralose, and since the purity of the final product sucralose is required to be high, the purity of sucralose-6-ester is required to be high, so in the present application, crystallization is performed while extraction is performed to remove organic ester impurities similar to the structure of sucralose-6-ester.

In some embodiments of the present application, the crystallization conditions are not limited, and all that is needed is to effectively crystallize sucralose-6-ester, in other embodiments of the present application, the crystallization temperature of the crystallization is-10 to 10 ℃ and the crystallization time is 6 to 12 hours in the crystallization step, which are selected by taking extraction and crystallization into consideration. In the condition range, not only can the impurities be effectively removed through extraction, but also the sucralose-6-ester can reach a relatively ideal yield, and the loss of the sucralose-6-ester is not caused.

In order to implement the above method for purifying sucralose-6-ester, the present application designs a set of equipment for purifying sucralose-6-ester, as shown in fig. 2, fig. 2 shows a schematic structural diagram of a device for purifying sucralose-6-ester according to an embodiment of the present application, and as can be seen from fig. 2, the device 200 includes:

a desolventizing kettle V-1; an oxidation kettle V-2; a neutralization kettle V-3; a crystallization kettle V-4; a phase splitter V-5; a deesterification kettle V-6; an extraction kettle V-7; an ester crystallization kettle V-8; a water crystallization kettle V-9, and plate and frame filter presses E-1, E-2, E-3 and E-4.

Wherein, the outlet of the desolventizing kettle V-1 is connected with the inlet of the oxidation kettle V-2; the outlet of the oxidation kettle V-2 is connected with the inlet of the neutralization kettle V-3, and the outlet of the neutralization kettle V-3 is connected with the inlet of the plate-and-frame filter press E-1; a liquid outlet of the plate-and-frame filter press E-1 is connected with an inlet of a crystallization kettle V-4; the outlet of the crystallization kettle V-4 is connected with the inlet of the plate-and-frame filter press E-2; the solid substance outlet of the plate-and-frame filter press E-2 is connected with an ester crystallization kettle V-8; the outlet of the ester crystallization kettle V-8 is connected with the inlet of the plate-and-frame filter press E-3; a solid substance outlet of the plate-and-frame filter press E-3 is connected with a water crystallization kettle V-9; the outlet of the water crystallization kettle V-9 is connected with a plate-and-frame filter press E-4; a liquid substance outlet of the plate-and-frame filter press E-2 is connected with a phase separator V-5; the upper end outlet of the phase separator V-5 is connected with a deesterification kettle V-6; the lower outlet of the phase separator V-5 is connected with an extraction kettle V-7. It should be noted that the above description is only the main connection relationship of the purification apparatus 200, the direct connection relationship of each kettle or plate-and-frame filter press can be adaptively adjusted according to the requirement, and the type of each kettle can be selected according to the respective functional requirement, which is not limited in this application, for example, the desolventizing kettle V-1 can be an evaporation type reaction kettle, and a vacuum pump can be provided if necessary; in addition, the number of tanks or plate and frame filter presses in the purification apparatus 200 may be increased or decreased as necessary.

The purification method of the sucrose-6-ester by three-filtration implemented by the device can be briefly described as follows:

and (3) inputting the chlorination neutralization solution, namely the mother solution to be purified, into a desolventizing kettle V-1 for concentration to remove most of DMF and trichloroethane, and then adding pure water (and/or water crystallization mother solution) to prepare the aqueous solution to be purified.

Inputting the aqueous solution to be purified into an oxidation kettle V-2, sequentially adding an oxidant and a decolorizing agent, reacting for a period of time under a certain condition, adding an alkaline hydrolysis agent until the pH value of the aqueous solution to be purified reaches a preset value, such as 8.5-10.5, and continuously keeping reacting for a period of time.

After the reaction is finished, the mixture enters a plate-and-frame filter press E-1 for filter pressing separation to obtain a solid and a first filtrate; and (3) treating the separated solid waste, feeding the first filtrate into a neutralization kettle V-3, adjusting the pH value, feeding the first filtrate into a crystallization kettle V-4, adding an organic ester extracting agent (and a second organic phase) into the crystallization kettle V-4, mixing the organic ester extracting agent with the first filtrate, simultaneously performing extraction crystallization, feeding the mixture into a plate-and-frame filter press E-2 for filter pressing separation after the crystallization is finished, obtaining solid crystals and second filtrate, wherein the separated solid is a crude product of sucralose-6-ethyl ester, and the second filtrate enters a phase separator V-5.

A first water phase is separated from the lower end of the phase separator V-5 and enters an extraction kettle V-7; separating out an organic ester phase (a first organic phase) from the upper end of the phase separator V-5, feeding the organic ester phase (the first organic phase) into a de-esterification kettle V-6, evaporating to remove organic ester, adding water to the residual sugar residues to dissolve the sugar residues, treating the water-insoluble sugar residues as waste after the dissolution is finished, forming a sugar residue aqueous solution by the water-soluble sugar residues, and feeding the sugar residue aqueous solution into an extraction kettle V-7 to be mixed with the first water phase.

And (3) adding an organic ester extractant into the extraction kettle V-7, after extraction is finished, enabling the upper phase to be an organic ester phase (a second organic phase), sending the second organic phase into the crystallization kettle V-3 to participate in crystallization, enabling the lower phase to be a second water phase, and treating the second water phase as high-salinity wastewater.

Inputting the sucralose-6-ethyl ester crude product separated from the plate-and-frame filter press E-2 into an ester crystallization kettle V-8, adding an organic ester extractant for ester crystallization, and sending the product into a plate-and-frame filter press E-3 after the crystallization is finished; and (3) obtaining ester crystallization crude products (intermediate crystals) after filter pressing by a filter press, sending the ester crystallization crude products (intermediate crystals) into a water crystallization kettle V-9, adding pure water into the water crystallization kettle V-9, sending the crystallized product into a plate-and-frame filter press E-4 for filter pressing and separation to obtain sucralose-6-ethyl ester fine products and a fourth filtrate, wherein the fourth filtrate is water crystallization mother liquor and can be sent into a desolventizing kettle V-1 for preparing aqueous solution to be purified.

Source of mother liquor to be purified

And (3) neutralizing the mother liquor to be purified, also called chlorination reaction neutralizing liquid, with ammonia water, and then adjusting the pH to 6-8 with hydrochloric acid to obtain chlorination liquid generated in a chlorination section in the sucralose production process, wherein the target component of sucralose-6-ethyl ester, and the contents of the components to be oxidized, namely sucralose diester and tetrachlorosucrose-6-ethyl ester, are detected by a liquid chromatograph, and other embodiments or comparative examples are the same and are not repeated.

Example 1

The chlorination neutralization solution components are shown in table 1.

TABLE 1 Chlorination neutralization solution composition Table

Components	Sucralose-6-ethyl ester	Sucralose diester	Tetrachlorosucrose-6-ethyl ester
				Mass concentration/g/L	53.87	5.34	4.85

Will be 7m³The neutralization solution of the chlorination reaction is fed into a concentration kettle V-1 for concentration at the concentration temperature of 80 ℃ and the vacuum degree of-0.05 Mpa, and after the concentration is finished, water crystallization mother liquor and pure water are added to prepare a concentrated aqueous solution with the volume of 4.9m³(ii) a Inputting the concentrated aqueous solution into an oxidation kettle V-2, sequentially adding 78.46kg of sodium hypochlorite serving as an oxidant (based on the volume of a neutralization solution) and 3.5kg of activated carbon serving as a decolorizer (based on the volume of the neutralization solution), reacting at 40 ℃ for 4 hours, pressing the material into the neutralization kettle V-3 after the reaction is finished, adding ammonia water, adjusting the pH of the system to 8.5, adding dilute sulfuric acid, adjusting the pH to 8, and after the adjustment is finished, performing filter pressing separation on the material by using a plate and frame filter press E-1; the separated solid is treated as solid waste, and the filtrate enters a crystallization kettle V-4; adding ethyl acetate and ester phase extraction liquid into a crystallization kettle, mixing and crystallizing, wherein the total volume of the ethyl acetate and the ester phase extraction liquid is 1.5 times of the volume of the filtrate, the crystallization temperature is 0 ℃, and the crystallization time is 12 hours. After crystallization, inputting the materials into a plate-and-frame filter press E-2 for filter pressing separation; the separated solid is a crude product of sucralose-6-ethyl ester, and the yield and purity of the obtained crude product are shown in Table 2.

TABLE 2 sucralose-6-ethyl ester fine product purity and yield

Example 2

The chlorination neutralization solution composition is shown in table 3.

TABLE 3 Chlorination neutralization solution composition Table

Components	Sucralose-6-ethyl ester	Sucralose diester	Tetrachlorosucrose-6-ethyl ester
				Mass concentration/g/L	54.03	4.28	5.11

Will be 5m³The neutralization solution of the chlorination reaction is fed into a concentration kettle V-1 for concentration at 85 ℃ and the vacuum degree of-0.07 Mpa, and after the concentration is finished, water crystallization mother liquor and pure water are added to prepare a concentrated aqueous solution with the volume of 3.5m³(ii) a Inputting the concentrated aqueous solution into an oxidation kettle V-2, sequentially adding 56.04kg of sodium hypochlorite serving as an oxidant (taking the volume of a neutralization solution as a reference) and 2.5kg of activated carbon serving as a decolorizer (taking the volume of the neutralization solution as a reference), reacting at 45 ℃ for 3.5h, and after the reaction is finished, feeding the materials into a plate-and-frame filter press E-1 for filter pressing and separation; treating the separated solid waste, feeding the filtrate into a neutralization kettle V-3, adding ammonia water, adjusting the pH of the system to 9.5, then adding dilute sulfuric acid, adjusting the pH to 7.5, and inputting the material into a crystallization kettle V-4 after the adjustment is finished; adding ethyl acetate and ester phase extraction liquid into a crystallization kettle, mixing and crystallizing, wherein the total volume of the ethyl acetate and the ester phase extraction liquid is 1.5 times of the volume of the filtrate, the crystallization temperature is 0 ℃, and the crystallization time is 10 hours. After crystallization, inputting the materials into a plate-and-frame filter press E-2 for filter pressing separation; the isolated solid was a crude sucralose-6-ethyl ester, and the yield and purity of the crude product were as shown in Table 4.

TABLE 4 sucralose-6-ethyl ester fine product purity and yield

Example 3

The chlorination neutralization solution composition is shown in Table 5.

TABLE 5 Chlorination neutralization solution composition Table

Components	Sucralose-6-ethyl ester	Sucralose diester	Tetrachlorosucrose-6-ethyl ester
				Mass concentration/g/L	55.90	4.27	5.23

1m is³The neutralization solution of the chlorination reaction is fed into a concentration kettle V-1 for concentration at the temperature of 60 ℃ and the vacuum degree of-0.1 Mpa, and after the concentration is finished, water crystallization mother liquor and pure water are added to prepare a concentrated aqueous solution with the volume of 0.5m³(ii) a Inputting the concentrated aqueous solution into an oxidation kettle V-2, sequentially adding 19kg of sodium hypochlorite serving as an oxidant (based on the volume of a neutralization solution) and 2kg of activated carbon serving as a decolorizer (based on the volume of the neutralization solution), reacting at 60 ℃ for 1h, pressing the material into a neutralization kettle V-3 after the reaction is finished, adding ammonia water, adjusting the pH of the system to 10.5, adding hydrochloric acid, adjusting the pH to 6.5, and after the adjustment is finished, performing filter pressing separation on the material by using a plate and frame filter press E-1; the separated solid is treated as solid waste, and the filtrate enters a crystallization kettle V-4; adding methyl acetate and ester phase extraction liquid into a crystallization kettle, mixing and crystallizing, wherein the total volume of the methyl acetate and the ester phase extraction liquid is the filtrate3 times of the volume, the crystallization temperature is-10 ℃, and the crystallization time is 6 hours. After crystallization, inputting the materials into a plate-and-frame filter press E-2 for filter pressing separation; the separated solid is a crude product of sucralose-6-ethyl ester, and the filtrate enters a phase separator V-5; separating out organic ester phase from the upper end of the phase separator, feeding into a de-esterification kettle V-6, evaporating to remove organic ester, adding water to dissolve sugar residue, wherein the water addition amount is 0.5 times of the volume of the ester, the dissolving temperature is 70 ℃, and the time is 0.5 h. After the dissolution is finished, inputting the aqueous solution into an extraction kettle V-7, and performing waste treatment on insoluble sugar residues; separating out a water phase from the lower end of the phase separator, feeding the water phase into an extraction kettle V-7, adding methyl acetate into the extraction kettle V-7 for extraction, wherein the extraction ratio of methyl acetate to an aqueous solution is 0.1:1, feeding an upper-phase ester phase extraction liquid into a crystallization kettle V-3 for crystallization after extraction is finished, and treating a lower-phase water phase as high-salinity wastewater; inputting the crude sucralose-6-ethyl ester 1 separated from the plate-and-frame filter press E-2 into an ester crystallization kettle V-8, adding methyl acetate for ester crystallization, wherein the adding amount is 1:2, the crystallization temperature is-5 ℃, and the crystallization time is 0.5 h. After crystallization is finished, feeding the mixture into a plate-and-frame filter press E-3; carrying out filter pressing by a filter press to obtain an ester crystallization crude product 2, and feeding the ester crystallization crude product into a water crystallization kettle V-9; adding pure water into a water crystallization kettle V-9, wherein the adding amount of the pure water is 1:2 relative to the crude product 2, the crystallization temperature is 0 ℃, and the crystallization time is 1 h. And (3) after crystallization, sending the mixture into a plate-and-frame filter press E-4 for filter pressing separation, obtaining a refined sucralose-6-ethyl ester product after separation, and sending the water crystallization mother liquor into a concentration kettle V-1 for preparing a concentrated aqueous solution. The crude product yield and purity obtained are shown in table 6.

TABLE 6 sucralose-6-ethyl ester fine product purity and yield

Note: the yield was calculated as the initial amount of sucralose-6-ethyl ester in the neutralization solution of the chlorination reaction (same as in other examples).

Example 4

The chlorination neutralization solution composition is shown in Table 7.

TABLE 4 Chlorination neutralization solution composition Table

Components	Sucralose-6-ethyl ester	Sucralose diester	Tetrachlorosucrose-6-ethyl ester
				Mass concentration/g/L	60.37	3.21	6.73

2m is³The neutralization solution of the chlorination reaction is fed into a concentration kettle V-1 for concentration at the concentration temperature of 80 ℃ and the vacuum degree of-0.05 Mpa, and after the concentration is finished, water crystallization mother liquor and pure water are added to prepare a concentrated aqueous solution with the volume of 2m³(ii) a Inputting the concentrated aqueous solution into an oxidation kettle V-2, sequentially adding 27.83kg of sodium hypochlorite serving as an oxidant (based on the volume of a neutralization solution) and 3.8kg of activated carbon serving as a decolorizer (based on the volume of the neutralization solution), reacting at 55 ℃ for 1.5h, pressing the material into the neutralization kettle V-3 after the reaction is finished, adding 20 wt% of sodium hydroxide, adjusting the pH of the system to 10.5, then adding hydrochloric acid, adjusting the pH to 6.5, and after the adjustment is finished, performing filter pressing separation on the material by using a plate and frame filter press E-1; the separated solid is treated as solid waste, and the filtrate enters a crystallization kettle V-4; adding ethyl acetate and ester phase extraction liquid into a crystallization kettle, mixing and crystallizing, wherein the total volume of the ethyl acetate and the ester phase extraction liquid is 1 time of the volume of the filtrate, the crystallization temperature is-5 ℃, and the crystallization time is 7 hours. After crystallization, inputting the materials into a plate-and-frame filter press E-2 for filter pressing separation; the separated solid is a crude product of sucralose-6-ethyl ester, and the filtrate enters a phase separator V-5; separating organic ester phase from the upper end of the phase separator, feeding into a deesterification kettle V-6, evaporating to remove organic ester, addingDissolving sugar residue with water 2 times of the volume of ester at 40 deg.C for 2 hr. After the dissolution is finished, inputting the aqueous solution into an extraction kettle V-7, and performing waste treatment on insoluble sugar residues; separating out a water phase from the lower end of the phase separator, feeding the water phase into an extraction kettle V-7, adding ethyl acetate into the extraction kettle V-7 for extraction, wherein the extraction ratio of ethyl acetate to an aqueous solution is 0.5:1, feeding an upper-phase ester phase extraction liquid into a crystallization kettle V-3 for crystallization after extraction is finished, and treating a lower-phase water phase as high-salinity wastewater; inputting the crude sucralose-6-ethyl ester 1 separated from the plate-and-frame filter press E-2 into an ester crystallization kettle V-8, adding ethyl acetate for ester crystallization, wherein the adding amount of the ethyl acetate is 1:2.5 of the crude sucralose-6-ethyl ester, the crystallization temperature is 0 ℃, and the crystallization time is 1.5 h. After crystallization is finished, feeding the mixture into a plate-and-frame filter press E-3; carrying out filter pressing by a filter press to obtain an ester crystallization crude product 2, and feeding the ester crystallization crude product into a water crystallization kettle V-9; adding pure water into a water crystallization kettle V-9, wherein the adding amount of the pure water is 2: 1:3 of the crude product, the crystallization temperature is 5 ℃, and the crystallization time is 2 h. And (3) after crystallization, sending the mixture into a plate-and-frame filter press E-4 for filter pressing separation, obtaining a refined sucralose-6-ethyl ester product after separation, and sending the water crystallization mother liquor into a concentration kettle V-1 for preparing a concentrated aqueous solution. The crude yields and purities obtained are shown in table 8.

TABLE 8 sucralose-6-ethyl ester fine product purity and yield

Example 5

The chlorination neutralization solution composition is shown in Table 9.

TABLE 9 Chlorination neutralization Components

Components	Sucralose-6-ethyl ester	Sucralose diester	Tetrachlorosucrose-6-ethyl ester
				Mass concentration/g/L	50.39	6.82	4.71

Mixing 3m³The neutralization solution of the chlorination reaction is fed into a concentration kettle V-1 for concentration at 70 ℃ and the vacuum degree of-0.07 Mpa, and after the concentration is finished, water crystallization mother liquor and pure water are added to prepare a concentrated aqueous solution with the volume of 2.1m³(ii) a Inputting the concentrated aqueous solution into an oxidation kettle V-2, sequentially adding 51.89kg of sodium hypochlorite serving as an oxidant (based on the volume of a neutralization solution) and 5.4kg of activated carbon serving as a decolorizer (based on the volume of the neutralization solution), reacting at 45 ℃ for 3 hours, pressing the material into a neutralization kettle V-3 after the reaction is finished, adding ammonia water, adjusting the pH of the system to 10, adding dilute sulfuric acid, adjusting the pH to 7.5, and after the adjustment is finished, performing pressure filtration and separation on the material by using a plate and frame filter press E-1; the separated solid is treated as solid waste, and the filtrate enters a crystallization kettle V-4; adding isobutyl acetate and ester phase extract into a crystallization kettle, mixing and crystallizing with the filtrate, wherein the total volume of the isobutyl acetate and the ester phase extract is 1.5 times of the volume of the filtrate, the crystallization temperature is 0 ℃, and the crystallization time is 8 hours. After crystallization, inputting the materials into a plate-and-frame filter press E-2 for filter pressing separation; the separated solid is a crude product of sucralose-6-ethyl ester, and the filtrate enters a phase separator V-5; separating out organic ester phase from the upper end of the phase separator, feeding into a de-esterification kettle V-6, evaporating to remove organic ester, adding water to dissolve sugar residue, wherein the adding amount of water is 1.5 times of the volume of the ester, the dissolving temperature is 50 ℃, and the time is 1.5 h. After the dissolution is finished, inputting the aqueous solution into an extraction kettle V-7, and performing waste treatment on insoluble sugar residues; separating out a water phase from the lower end of the phase separator, feeding the water phase into an extraction kettle V-7, adding isobutyl acetate into the extraction kettle V-7 for extraction, wherein the extraction ratio is that the ratio of isobutyl acetate to an aqueous solution is 0.7:1, feeding an upper-phase ester phase extraction liquid into a crystallization kettle V-3 for crystallization after extraction is finished, and treating a lower-phase water phase as high-salt wastewater; filter pressing from plate frameInputting the crude sucralose-6-ethyl ester 1 separated by the machine E-2 into an ester crystallization kettle V-8, adding isobutyl acetate for ester crystallization, wherein the addition amount of the crude sucralose-6-ethyl ester 1 is 1:3.5, the crystallization temperature is 10 ℃, and the crystallization time is 3 hours. After crystallization is finished, feeding the mixture into a plate-and-frame filter press E-3; carrying out filter pressing by a filter press to obtain an ester crystallization crude product 2, and feeding the ester crystallization crude product into a water crystallization kettle V-9; adding pure water into a water crystallization kettle V-9, wherein the adding amount of the pure water is crude product 2: 1:4, the crystallization temperature is 15 ℃, and the crystallization time is 3 h. And (3) after crystallization, sending the mixture into a plate-and-frame filter press E-4 for filter pressing separation, obtaining a refined sucralose-6-ethyl ester product after separation, and sending the water crystallization mother liquor into a concentration kettle V-1 for preparing a concentrated aqueous solution. The crude product yield and purity obtained are shown in table 10.

TABLE 10 sucralose-6-ethyl ester fine product purity and yield

Example 6

The chlorination neutralization solution composition is shown in Table 11.

TABLE 11 Chlorination neutralization Components

Components	Sucralose-6-ethyl ester	Sucralose diester	Tetrachlorosucrose-6-ethyl ester
				Mass concentration/g/L	51.88	5.88	5.97

Will be 4m³The neutralization solution of the chlorination reaction is fed into a concentration kettle V-1 for concentration at 65 ℃ and the vacuum degree of-0.08 Mpa, and after the concentration is finished, water crystallization mother liquor and pure water are added to prepare a concentrated aqueous solution with the volume of 3.2m³(ii) a Inputting the concentrated aqueous solution into an oxidation kettle V-2, sequentially adding 61.62kg of sodium hypochlorite serving as an oxidant (based on the volume of a neutralization solution) and 6.4kg of activated carbon serving as a decolorizer (based on the volume of the neutralization solution), reacting at 60 ℃ for 1h, pressing the material into a neutralization kettle V-3 after the reaction is finished, adding 20 wt% of sodium hydroxide, adjusting the pH of the system to 8.5, then adding dilute sulfuric acid, adjusting the pH to 6.5, and after the adjustment is finished, performing pressure filtration and separation on the material by using a plate and frame filter press E-1; the separated solid is treated as solid waste, and the filtrate enters a crystallization kettle V-4; adding butyl acetate and ester phase extraction liquid into a crystallization kettle, mixing and crystallizing with the filtrate, wherein the total volume of the butyl acetate and the ester phase extraction liquid is 2 times of the volume of the filtrate, the crystallization temperature is 5 ℃, and the crystallization time is 10 hours. After crystallization, inputting the materials into a plate-and-frame filter press E-2 for filter pressing separation; the separated solid is a crude product of sucralose-6-ethyl ester, and the filtrate enters a phase separator V-5; separating out organic ester phase from the upper end of the phase separator, feeding into a de-esterification kettle V-6, evaporating to remove organic ester, adding water to dissolve sugar residue, wherein the water addition amount is 0.5 times of the volume of the ester, the dissolving temperature is 70 ℃, and the time is 0.5 h. After the dissolution is finished, inputting the aqueous solution into an extraction kettle V-7, and performing waste treatment on insoluble sugar residues; separating out a water phase from the lower end of the phase separator, feeding the water phase into an extraction kettle V-7, adding butyl acetate into the extraction kettle V-7 for extraction, wherein the extraction ratio of butyl acetate to an aqueous solution is 0.3:1, feeding an upper-phase ester phase extraction liquid into a crystallization kettle V-3 for crystallization after extraction is finished, and treating a lower-phase water phase as high-salinity wastewater; inputting the crude sucralose-6-ethyl ester 1 separated from the plate-and-frame filter press E-2 into an ester crystallization kettle V-8, adding butyl acetate for ester crystallization, wherein the addition amount of the butyl acetate is 1:4.5, the crystallization temperature is 5 ℃, and the crystallization time is 2 hours. After crystallization is finished, feeding the mixture into a plate-and-frame filter press E-3; carrying out filter pressing by a filter press to obtain an ester crystallization crude product 2, and feeding the ester crystallization crude product into a water crystallization kettle V-9; adding pure water into a water crystallization kettle V-9, wherein the adding amount of the pure water is crude product 2: 1:5, the crystallization temperature is 30 ℃, and the crystallization time is 5 h. Crystallization ofAnd (3) after the reaction is finished, sending the reaction product into a plate-and-frame filter press E-4 for filter pressing separation, obtaining a refined sucralose-6-ethyl ester product after the separation, and sending the water crystallization mother liquor into a concentration kettle V-1 for preparing a concentrated aqueous solution. The crude product yields and purities obtained are shown in table 12.

TABLE 12 sucralose-6-ethyl ester fine product purity and yield

Example 7

The chlorination neutralization solution composition is shown in Table 13.

TABLE 13 Chlorination neutralization solution composition Table

Components	Sucralose-6-ethyl ester	Sucralose diester	Tetrachlorosucrose-6-ethyl ester
				Mass concentration/g/L	54.31	4.29	6.76

Will be 5m³The neutralization solution of the chlorination reaction is fed into a concentration kettle V-1 for concentration at the concentration temperature of 75 ℃ and the vacuum degree of-0.06 Mpa, and after the concentration is finished, water crystallization mother liquor and pure water are added to prepare a concentrated aqueous solution with the volume of 4.5m³(ii) a The concentrated aqueous solution is input into an oxidation kettle V-2, and 71.83kg of sodium hypochlorite (based on the volume of the neutralization solution) as an oxidant is sequentially added) Reacting with 7.5kg of decolorizing agent active carbon (taking the volume of a neutralization solution as a reference) at 50 ℃ for 2 hours, after the reaction is finished, pressing the materials into a neutralization kettle V-3, adding ammonia water, adjusting the pH of the system to 8.5, then adding dilute sulfuric acid, adjusting the pH to 7.5, and after the adjustment is finished, performing filter pressing separation on the materials by using a plate and frame filter press E-1; the separated solid is treated as solid waste, and the filtrate enters a crystallization kettle V-4; adding isopropyl acetate and ester phase extraction liquid into a crystallization kettle, mixing and crystallizing, wherein the total volume of the isopropyl acetate and the ester phase extraction liquid is 2.5 times of the volume of the filtrate, the crystallization temperature is 10 ℃, and the crystallization time is 12 hours. After crystallization, inputting the materials into a plate-and-frame filter press E-2 for filter pressing separation; the separated solid is a crude product of sucralose-6-ethyl ester, and the filtrate enters a phase separator V-5; separating out organic ester phase from the upper end of the phase separator, feeding into a de-esterification kettle V-6, evaporating to remove organic ester, adding water to dissolve sugar residue, wherein the adding amount of water is 1 time of the volume of the ester, the dissolving temperature is 60 ℃, and the time is 1 h. After the dissolution is finished, inputting the aqueous solution into an extraction kettle V-7, and performing waste treatment on insoluble sugar residues; separating out a water phase from the lower end of the phase separator, feeding the water phase into an extraction kettle V-7, adding isopropyl acetate into the extraction kettle V-7 for extraction, wherein the extraction ratio is that the isopropyl acetate is 1:1 to obtain an aqueous solution, feeding an upper-phase ester phase extraction liquid into a crystallization kettle V-3 for crystallization after extraction is finished, and treating a lower-phase water phase as high-salinity wastewater; inputting the sucralose-6-ethyl ester crude product 1 separated from the plate-and-frame filter press E-2 into an ester crystallization kettle V-8, adding isopropyl acetate for ester crystallization, wherein the addition amount of the isopropyl acetate is 1:5 of the crude product, the crystallization temperature is 10 ℃, and the crystallization time is 3 hours. After crystallization is finished, feeding the mixture into a plate-and-frame filter press E-3; carrying out filter pressing by a filter press to obtain an ester crystallization crude product 2, and feeding the ester crystallization crude product into a water crystallization kettle V-9; adding pure water into a water crystallization kettle V-9, wherein the adding amount of the pure water is crude product 2: 1:3, the crystallization temperature is 25 ℃, and the crystallization time is 4 h. And (3) after crystallization, sending the mixture into a plate-and-frame filter press E-4 for filter pressing separation, obtaining a refined sucralose-6-ethyl ester product after separation, and sending the water crystallization mother liquor into a concentration kettle V-1 for preparing a concentrated aqueous solution. The crude yields and purities obtained are shown in table 14.

TABLE 14 sucralose-6-ethyl ester fine product purity and yield

Example 8

The chlorination reaction neutralized liquid composition is shown in Table 15.

TABLE 15 Chlorination neutralization solution composition Table

Components	Sucralose-6-ethyl ester	Sucralose diester	Tetrachlorosucrose-6-ethyl ester
				Mass concentration/g/L	52.99	3.99	6.12

Will be 6m³The neutralization solution of the chlorination reaction is fed into a concentration kettle V-1 for concentration at the temperature of 60 ℃ and the vacuum degree of-0.1 Mpa, and after the concentration is finished, water crystallization mother liquor and pure water are added to prepare a concentrated aqueous solution with the volume of 3.6m³(ii) a Inputting the concentrated aqueous solution into an oxidation kettle V-2, sequentially adding 72.79kg of sodium hypochlorite serving as an oxidant (based on the volume of a neutralization solution) and 6kg of activated carbon serving as a decolorizer (based on the volume of the neutralization solution), reacting at 50 ℃ for 3 hours, pressing the material into the neutralization kettle V-3 after the reaction is finished, adding 20 wt% of sodium hydroxide, adjusting the pH of the system to 9.5, then adding hydrochloric acid, adjusting the pH to 8, and after the adjustment is finished, performing pressure filtration and separation on the material by using a plate and frame filter press E-1; the separated solid is treated as solid waste, and the filtrate enters a crystallization kettle V-4; adding propyl acetate and ester phase extract into crystallization kettle, mixing with filtrate, crystallizing, and adding methyl acetateThe total volume of the ester phase extraction liquid is 1 time of the volume of the filtrate, the crystallization temperature is-8 ℃, and the crystallization time is 7 hours. After crystallization, inputting the materials into a plate-and-frame filter press E-2 for filter pressing separation; the separated solid is a crude product of sucralose-6-ethyl ester, and the filtrate enters a phase separator V-5; separating out organic ester phase from the upper end of the phase separator, feeding into a de-esterification kettle V-6, evaporating to remove organic ester, adding water to dissolve sugar residue, wherein the adding amount of water is 1.5 times of the volume of the ester, the dissolving temperature is 50 ℃, and the time is 1.5 h. After the dissolution is finished, inputting the aqueous solution into an extraction kettle V-7, and performing waste treatment on insoluble sugar residues; separating out a water phase from the lower end of the phase separator, feeding the water phase into an extraction kettle V-7, adding propyl acetate into the extraction kettle V-7 for extraction, wherein the extraction ratio of the propyl acetate to an aqueous solution is 0.9:1, feeding an upper-phase ester phase extraction liquid into a crystallization kettle V-3 for crystallization after extraction is finished, and treating a lower-phase water phase as high-salinity wastewater; inputting the sucralose-6-ethyl ester crude product 1 separated from the plate-and-frame filter press E-2 into an ester crystallization kettle V-8, adding propyl acetate for ester crystallization, wherein the addition amount is 1:4, the crystallization temperature is 5 ℃, and the crystallization time is 2 h. After crystallization is finished, feeding the mixture into a plate-and-frame filter press E-3; carrying out filter pressing by a filter press to obtain an ester crystallization crude product 2, and feeding the ester crystallization crude product into a water crystallization kettle V-9; adding pure water into a water crystallization kettle V-9, wherein the adding amount of the pure water is crude product 2: 1:5, the crystallization temperature is 30 ℃, and the crystallization time is 5 h. And (3) after crystallization, sending the mixture into a plate-and-frame filter press E-4 for filter pressing separation, obtaining a refined sucralose-6-ethyl ester product after separation, and sending the water crystallization mother liquor into a concentration kettle V-1 for preparing a concentrated aqueous solution. The crude product yield and purity obtained are shown in table 16.

TABLE 16 sucralose-6-ethyl ester fine product purity and yield

Example 9

The chlorination neutralization solution composition is shown in Table 17.

TABLE 17 Chlorination neutralization solution Components TABLE

Will be 7m³The neutralization solution of the chlorination reaction is fed into a concentration kettle V-1 for concentration at the concentration temperature of 80 ℃ and the vacuum degree of-0.05 Mpa, and after the concentration is finished, water crystallization mother liquor and pure water are added to prepare a concentrated aqueous solution with the volume of 4.9m³(ii) a Inputting the concentrated aqueous solution into an oxidation kettle V-2, sequentially adding 78.46kg of sodium hypochlorite serving as an oxidant (based on the volume of a neutralization solution) and 3.5kg of activated carbon serving as a decolorizer (based on the volume of the neutralization solution), reacting at 40 ℃ for 4 hours, pressing the material into the neutralization kettle V-3 after the reaction is finished, adding ammonia water, adjusting the pH of the system to 8.5, adding dilute sulfuric acid, adjusting the pH to 8, and after the adjustment is finished, performing filter pressing separation on the material by using a plate and frame filter press E-1; the separated solid is treated as solid waste, and the filtrate enters a crystallization kettle V-4; adding ethyl acetate and ester phase extraction liquid into a crystallization kettle, mixing and crystallizing, wherein the total volume of the ethyl acetate and the ester phase extraction liquid is 1.5 times of the volume of the filtrate, the crystallization temperature is 0 ℃, and the crystallization time is 12 hours. After crystallization, inputting the materials into a plate-and-frame filter press E-2 for filter pressing separation; the separated solid is a crude product of sucralose-6-ethyl ester, and the filtrate enters a phase separator V-5; separating out organic ester phase from the upper end of the phase separator, feeding into a de-esterification kettle V-6, evaporating to remove organic ester, adding water to dissolve sugar residue, wherein the adding amount of water is 2 times of the volume of the ester, the dissolving temperature is 40 ℃, and the time is 2 h. After completion of the dissolution, the solution was dissolved in waterInputting the liquid into an extraction kettle V-7, and performing waste treatment on insoluble sugar residues; separating out a water phase from the lower end of the phase separator, feeding the water phase into an extraction kettle V-7, adding ethyl acetate into the extraction kettle V-7 for extraction, wherein the extraction ratio of ethyl acetate to an aqueous solution is 0.2:1, feeding an upper-phase ester phase extraction liquid into a crystallization kettle V-3 for crystallization after extraction is finished, and treating a lower-phase water phase as high-salinity wastewater; inputting the crude sucralose-6-ethyl ester 1 separated from the plate-and-frame filter press E-2 into an ester crystallization kettle V-8, adding ethyl acetate for ester crystallization, wherein the adding amount is 1:3, the crystallization temperature is 0 ℃, and the crystallization time is 1 h. After crystallization is finished, feeding the mixture into a plate-and-frame filter press E-3; carrying out filter pressing by a filter press to obtain an ester crystallization crude product 2, and feeding the ester crystallization crude product into a water crystallization kettle V-9; adding pure water into a water crystallization kettle V-9, wherein the adding amount of the pure water is crude product 2: 1:3.5, the crystallization temperature is 5 ℃, and the crystallization time is 5 h. And (3) after crystallization, sending the mixture into a plate-and-frame filter press E-4 for filter pressing separation, obtaining a refined sucralose-6-ethyl ester product after separation, and sending the water crystallization mother liquor into a concentration kettle V-1 for preparing a concentrated aqueous solution. The crude product yield and purity obtained are shown in table 18.

TABLE 18 sucralose-6-ethyl ester fine purity and yield

Example 10

The chlorination neutralization solution composition is shown in Table 19.

TABLE 19 Chlorination neutralization solution composition Table

Components	Sucralose-6-ethyl ester	Sucralose diester	Tetrachlorosucrose-6-ethyl ester
				Mass concentration/g/L	58.59	5.38	6.97

Mixing 3m³The neutralization solution of the chlorination reaction is input into a concentration kettle V-1 for concentration, the concentration temperature is 60 ℃, the vacuum degree is-0.1 Mpa, and after the concentration is finished, water crystallization mother liquor and pure water are added to prepare a concentrated aqueous solution, wherein the volume of the concentrated aqueous solution is 1 time of that of the neutralization solution of the original chlorination reaction; the concentrated aqueous solution is fed into an oxidation vessel V-2. Adding 55.57kg of oxidant sodium hypochlorite (based on the volume of the neutralization solution) and 4kg of decolorizing agent active carbon (based on the volume of the neutralization solution) in sequence; reacting for 2 hours at 60 ℃, after the reaction is finished, pressing the materials into a neutralization kettle V-3, adding ammonia water, adjusting the pH of the system to 9.5, then adding dilute hydrochloric acid, adjusting the pH to 7.5, and after the adjustment is finished, performing filter pressing separation on the materials by using a plate and frame filter press E-1; the separated solid is treated as solid waste, and the filtrate enters a crystallization kettle V-4; adding ethyl acetate and ester phase extract into crystallization kettle, mixing with filtrate, and crystallizing, wherein the total volume of ethyl acetate and ester phase extract is 2.5 times of the filtrate volume, the crystallization temperature is-5 deg.C, and the crystallization time is 8 hr. After crystallization, inputting the materials into a plate-and-frame filter press E-2 for filter pressing separation; the separated solid is a crude product of sucralose-6-ethyl ester, and the filtrate enters a phase separator V-5; separating out organic ester phase from the upper end of the phase separator, feeding into a de-esterification kettle V-6, evaporating to remove organic ester, adding water to dissolve sugar residue, wherein the adding amount of water is 1 time of the volume of the ester, the dissolving temperature is 60 ℃, and the time is 2 h. After the dissolution is finished, inputting the aqueous solution into an extraction kettle V-7, and performing waste treatment on insoluble sugar residues; separating out a water phase from the lower end of the phase separator, feeding the water phase into an extraction kettle V-7, adding ethyl acetate into the extraction kettle V-7 for extraction, wherein the extraction ratio of ethyl acetate to an aqueous solution is 0.2:1, feeding an upper-phase ester phase extraction liquid into a crystallization kettle V-3 for crystallization after extraction is finished, and treating a lower-phase water phase as high-salinity wastewater; inputting the sucralose-6-ethyl ester crude product 1 separated from the plate-and-frame filter press E-2 into an ester crystallization kettle V-8, adding ethyl acetate for ester crystallization,the amount of crude 1: methyl acetate added was 1:2.5, the crystallization temperature was 0 ℃ and the crystallization time was 2 h. After crystallization is finished, feeding the mixture into a plate-and-frame filter press E-3; carrying out filter pressing by a filter press to obtain an ester crystallization crude product 2, and feeding the ester crystallization crude product into a water crystallization kettle V-9; adding pure water into a water crystallization kettle V-9, wherein the adding amount of the pure water is 2: 1:3 of the crude product, the crystallization temperature is 5 ℃, and the crystallization time is 2 h. And (3) after crystallization, sending the mixture into a plate-and-frame filter press E-4 for filter pressing separation, obtaining a refined sucralose-6-ethyl ester product after separation, and sending the water crystallization mother liquor into a concentration kettle V-1 for preparing a concentrated aqueous solution. The crude product yield and purity obtained are shown in table 20.

TABLE 20 comparison of sucralose-6-ethyl ester quality purity and yield

Comparative example 1

To further demonstrate that the yield of sucralose-6-ethyl ester after the addition of the oxidizing agent is higher than that of the conventional purification operation, the same sample as that used in example 10 was selected and the purification of sucralose-6-ethyl ester was performed in the same operation, except that the oxidizing agent was added in example 10 and the oxidizing agent was not added in comparative example 1. The chlorination neutralization solution composition is shown in Table 21.

TABLE 21 Chlorination neutralization solution composition Table

Mixing 3m³The neutralization solution of the chlorination reaction is input into a concentration kettle V-1 for concentration, the concentration temperature is 60 ℃, the vacuum degree is-0.1 Mpa, and after the concentration is finished, water crystallization mother liquor and pure water are added to prepare a concentrated aqueous solution, wherein the volume of the concentrated aqueous solution is 1 time of that of the neutralization solution of the original chlorination reaction; the concentrated aqueous solution is fed into an oxidation vessel V-2. The method comprises the following steps: adding 55.57kg of oxidant sodium hypochlorite (based on the volume of the neutralization solution) and 4kg of decolorizing agent active carbon (based on the volume of the neutralization solution) in sequence; the second method comprises the following steps: adding 4kg of decolorizing agent active carbon (based on the volume of the neutralization solution), reacting for 2h at 60 ℃, pressing the materials into a neutralization kettle V-3 after the reaction is finished, adding ammonia water, adjusting the pH of the system to 9.5, then adding hydrochloric acid, adjusting the pH to 7.5, and after the adjustment is finished, feeding the materials into a plate and frame filter press E-1 for filter pressing separation; the separated solid is treated as solid waste, and the filtrate enters a crystallization kettle V-4; adding ethyl acetate and ester phase extract into crystallization kettle, mixing with filtrate, and crystallizing, wherein the total volume of ethyl acetate and ester phase extract is 2.5 times of the filtrate volume, the crystallization temperature is-5 deg.C, and the crystallization time is 8 hr. After crystallization, inputting the materials into a plate-and-frame filter press E-2 for filter pressing separation; the separated solid is a crude product of sucralose-6-ethyl ester, and the filtrate enters a phase separator V-5; separating out organic ester phase from the upper end of the phase separator, feeding into a de-esterification kettle V-6, evaporating to remove organic ester, adding water to dissolve sugar residue, wherein the adding amount of water is 1 time of the volume of the ester, the dissolving temperature is 60 ℃, and the time is 2 h. After the dissolution is finished, inputting the aqueous solution into an extraction kettle V-7, and performing waste treatment on insoluble sugar residues; separating out a water phase from the lower end of the phase separator, feeding the water phase into an extraction kettle V-7, adding ethyl acetate into the extraction kettle V-7 for extraction, wherein the extraction ratio of ethyl acetate to an aqueous solution is 0.2:1, feeding an upper-phase ester phase extraction liquid into a crystallization kettle V-3 for crystallization after extraction is finished, and treating a lower-phase water phase as high-salinity wastewater; inputting the crude sucralose-6-ethyl ester 1 separated from the plate-and-frame filter press E-2 into an ester crystallization kettle V-8, adding ethyl acetate for ester crystallization, wherein the adding amount is 1:2.5 of the crude sucralose-6-ethyl ester, the crystallization temperature is 0 ℃, and the crystallization is carried outThe crystallization time is 2 h. After crystallization is finished, feeding the mixture into a plate-and-frame filter press E-3; carrying out filter pressing by a filter press to obtain an ester crystallization crude product 2, and feeding the ester crystallization crude product into a water crystallization kettle V-9; adding pure water into a water crystallization kettle V-9, wherein the adding amount of the pure water is 2: 1:3 of the crude product, the crystallization temperature is 5 ℃, and the crystallization time is 2 h. And (3) after crystallization, sending the mixture into a plate-and-frame filter press E-4 for filter pressing separation, obtaining a refined sucralose-6-ethyl ester product after separation, and sending the water crystallization mother liquor into a concentration kettle V-1 for preparing a concentrated aqueous solution. The crude product yield and purity obtained are shown in table 22.

TABLE 22 comparison of sucralose-6-ethyl ester fine purity and yield

As can be seen from tables 20 and 22, the addition of the oxidant oxidizes the byproducts sucralose diester and tetrachlorosucrose-6-ethyl ester into the target product sucralose-6-ethyl ester, which can significantly improve the yield of sucralose-6-ethyl ester.

In summary, according to the method for purifying sucralose-6-ethyl ester, the oxidant is added in the purification process, two impurities of sucralose diester and tetrachlorosucrose-6-ethyl ester are oxidized and converted into the target product sucralose-6-ethyl ester, so that the overall yield of sucralose-6-ethyl ester is improved, on one hand, the productivity of sucralose-6-ethyl ester is improved, on the other hand, the COD content of high-salt wastewater is reduced, and the pressure of subsequent biochemical treatment is relieved. In addition, the method simplifies the operation, shortens the flow, realizes cost reduction and efficiency improvement, and can create greater economic benefit.

In the description of the present application, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings, and are only for convenience of description and simplicity of description, and do not indicate or imply that the device or element being referred to must have a particular orientation, be constructed and operated in a particular orientation, and thus, should not be construed as limiting the present application. Furthermore, the terms "first," "second," "third," and the like are used for descriptive purposes only and are not to be construed as indicating or implying relative importance.

In the description of the present application, it is to be noted that, unless otherwise explicitly specified or limited, the terms "mounted," "connected," and "connected" are to be construed broadly, e.g., as meaning either a fixed connection, a removable connection, or an integral connection; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meaning of the above terms in the present application can be understood in a specific case by those of ordinary skill in the art.

While the foregoing is directed to embodiments of the present application, other modifications and variations of the present application may be devised by those skilled in the art in light of the above teachings. It should be understood by those skilled in the art that the foregoing detailed description is for the purpose of better explaining the present application, and the scope of protection of the present application shall be subject to the scope of protection of the claims.

Furthermore, those skilled in the art will appreciate that while some embodiments described herein include some features included in other embodiments, rather than other features, combinations of features of different embodiments are meant to be within the scope of the application and form different embodiments. For example, in the following claims, any of the claimed embodiments may be used in any combination.

Claims

1. A method for purifying sucralose-6-ester, comprising:

a concentration step: concentrating the mother liquor to be purified to remove the organic solvent, and after the concentration is finished, adding water into the mother liquor to form an aqueous solution to be purified; wherein, the mother liquor to be purified is obtained by neutralizing sucralose, and carrying out esterification and chlorination reaction to prepare reaction liquid of sucralose-6-ester;

2. The method of claim 1, further comprising:

and mixing the aqueous solution of the sugar residues with the first water phase, adding an extracting agent for extraction, and recovering a second organic phase obtained by extraction into the first filtrate to be subjected to the crystallization step.

3. The method according to claim 2, wherein in the filtrate recovery step, the ratio of the mass of the added water to the mass of the first organic phase is 0.5-2: 1, the dissolution temperature of the dissolution is 40-70 ℃, and the dissolution time is 0.5-2 h;

4. The method of claim 2, further comprising:

5. The method of claim 4, further comprising:

6. The method according to claim 4, wherein in the refining step, the mass ratio of the mass usage amount of the extracting agent to the mass of the sucralose-6-ester crude product is 2-5: 1; the crystallization temperature of the first crystallization is-5-10 ℃, and the crystallization time is 0.5-3 h;

the mass ratio of the water to the intermediate crystal is 2-5: 1; the crystallization temperature of the second crystallization is 0-30 ℃, and the crystallization time is 1-5 h.

7. The method according to claim 1, wherein in the concentration step, the concentration temperature is 60 to 80 ℃, and the vacuum degree is-0.1 to-0.05 Mpa;

8. The method according to claim 1, wherein in the oxidizing step, the oxidizing agent is one of sodium hypochlorite, sodium chlorate and calcium hypochlorite, preferably sodium hypochlorite;

9. The method according to claim 1, characterized in that in the oxidation step, the decolorizing agent is one or more of activated carbon, attapulgite, diatomaceous earth and activated clay, preferably activated carbon;

10. The process according to claim 1, characterized in that, in the oxidation step, the alkaline hydrolysis agent is ammonia or NaOH, preferably ammonia;

the dosage of the alkaline hydrolysis agent is based on the adjustment of the pH value of the aqueous solution to be purified to 8.5-10.5.

11. The method of claim 1, wherein, in the crystallizing step, the adjusting the first filtrate to neutral comprises:

adjusting the pH value of the first filtrate to 6.5-8.0 by using an acidic substance; wherein, the acidic substance is dilute hydrochloric acid or dilute sulfuric acid, and preferably dilute hydrochloric acid.

12. The method according to claim 1, wherein in the crystallization step, the extractant is one or more of methyl acetate, ethyl acetate, propyl acetate, isopropyl acetate, butyl acetate and isobutyl acetate, preferably ethyl acetate;