A method for recovering tin from trichlorosucrose

Abstract

The application discloses a method for recovering tin powder of sucralose, and belongs to the technical field of sucralose production. The method comprises the following steps: S1, water separation distillation; S2, organic tin recovery; S3, centrifugal drying; and S4, water separation and impurity washing. In the step S4, S41, cyclohexane and DMF are added into the crude tin powder obtained in the step S3, and the mixture is layered to obtain cyclohexane phase 1; S42, acid anhydride and water are added into the cyclohexane phase 1 in sequence, the mixture is stirred and layered to obtain cyclohexane phase 2; S43, DMF and water are added into the cyclohexane phase 2, and the mixture is layered to obtain cyclohexane phase 3; and S44, the cyclohexane phase 3 is distilled to obtain cyclohexane and tin ester phase. The dibutyl tin oxide obtained by the method is high in purity and can be directly reused, thereby solving the problem that the dibutyl tin oxide is difficult to reuse due to low purity in the existing sucralose production. Meanwhile, the method for recovering tin powder of sucralose is little different from the old production process, is easy to operate and has low investment.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of trichlorosucrose production, and particularly relates to a method for recovering tin powder in trichlorosucrose production. BACKGROUND

[0002] Trichlorosucrose is a high-fold sweetener. In the trichlorosucrose production process, tinization reaction is one of the key reactions. In the tinization reaction process, a catalyst dibutyl tin oxide is generally needed, which has a great influence on the conversion rate of the intermediate sucrose-6-ester. The dibutyl tin oxide is used as a catalyst for trichlorosucrose production, but when it is recovered and washed, flocculent substances with high tin content are generated. The flocculent substances contain many impurities after recovery, and the catalytic reaction is not ideal when they are used in production. The yield of the esterification liquid obtained by the reaction is low, and the flocculent substances cannot be directly reused. At present, the price of the raw material dibutyl tin oxide on the market is relatively high. Therefore, the recovery and reuse of the dibutyl tin oxide have a great influence on the cost of trichlorosucrose. The recovery of the dibutyl tin oxide in the trichlorosucrose production process is increasingly concerned.

[0003] At present, the main recovery process of the dibutyl tin oxide is to evaporate the flocculent substances into oil-like substances by using a distillation kettle, dissolve the oil-like substances in methanol, and then add them dropwise into an organic tin neutralization kettle to neutralize the reaction with liquid alkali to obtain tin powder. The reaction principle is shown as follows:

[0004] C 20 H 42 Sn2O5+2NaOH→2C8H 18 SnO+C2H3O2Na+2H2O.

[0005] The dibutyl tin oxide recovered by using this method contains a high proportion of impurities such as tin, monobutyl tin oxide, tributyl tin oxide, and tetrabutyl tin in the tin powder. The recovered tin powder can be used as raw material for continuous use. However, the current recovery process of the tin powder is not perfect, resulting in that the quality of the recovered tin powder does not meet the standards. Therefore, it is necessary to improve the recovery process of the dibutyl tin oxide.

[0006] Patent CN109575069A discloses a recovery method of a catalyst in trichlorosucrose production, which comprises the following steps: heating acylation liquid to 60-70℃, standing and keeping warm for 1-3h to obtain dibutyl tin acetate phase and sugar syrup phase by layering, separating out the dibutyl tin acetate phase, supplementing cyclohexane into the sugar syrup phase, stirring at about 40℃ for 1h, standing and layering out the sugar syrup phase, and then controlling the temperature of the cyclohexane phase to 60-100℃ to evaporate the cyclohexane under reduced pressure, and leaving the dibutyl tin acetate.

[0007] Patent CN109651428A discloses a method for recovering catalyst from trichloro-sucrose waste flocculation, which comprises the following steps: the waste flocculation solution is poured into a cyclohexane distillation kettle, cyclohexane and water are distilled out at 100-110 DEG C, black flocculation is left at the bottom of the kettle, the black flocculation is divided into a neutralization kettle, 3-5% NaOH solution is added for neutralization reaction, the material is centrifuged by a centrifuge to obtain crude dibutyl tin oxide, the crude dibutyl tin oxide is poured into a water separation kettle, then cyclohexane is supplemented in the water separation kettle, water is removed by warming and azeotropic reflux, acetic anhydride is supplemented and warmed to reflux to 70 DEG C for preservation, and appropriate amount of water is supplemented as an extractant to remove other impurities in the crude dibutyl tin oxide, and after static stratification, the lower layer of black water is sent to a sewage station, and the upper layer of cyclohexane phase is concentrated to obtain qualified dibutyl tin oxide.

[0008] Although the tin powder recovery process is improved, there are still problems such as low recovery purity and difficulty in reuse. Therefore, it is still necessary to propose a method for recovering dibutyl tin oxide in trichloro-sucrose production with high recovery purity and direct reuse. SUMMARY

[0009] The purpose of the present application is to solve the problems of low recovery purity and difficulty in reuse of dibutyl tin oxide in existing trichloro-sucrose production, and to provide a method for recovering trichloro-sucrose tin powder, which has high purity and can be directly reused.

[0010] In order to achieve the above purpose, the technical scheme adopted by the present application is as follows:

[0011] A method for recovering trichloro-sucrose tin powder, comprising the following steps:

[0012] S1, water separation distillation: the flocculation is distilled to remove cyclohexane, and is statically stratified to obtain a DMF-containing water phase and black oil;

[0013] S2, organotin recovery: the black oil obtained in step S1 is mixed with methanol, stirred and dissolved, and heated to obtain solution 1; the solution 1 is added to lye, incubated and reacted, and then cooled after the reaction is completed to obtain an organotin mixture;

[0014] S3, centrifugal drying: the organotin mixture obtained in step S2 is centrifuged and dried to obtain crude tin powder;

[0015] S4, water separation and impurity removal:

[0016] S41, adding cyclohexane and DMF to the crude tin powder obtained in step S3, and statically stratifying to obtain a DMF-containing water phase and a cyclohexane phase 1;

[0017] S42, adding acid anhydride and water to the cyclohexane phase 1 obtained in step S41, mixing, stirring and stratifying to obtain a DMF-containing water phase and a cyclohexane phase 2;

[0018] S43, adding DMF and water to the cyclohexane phase 2 obtained in step S42, washing and separating into a DMF-containing water phase and a cyclohexane phase 3;

[0019] S44, distilling the cyclohexane phase 3 obtained in step S43 to obtain a cyclohexane and tin ester phase.

[0020] Preferably, the flocculation in step S1 is obtained after the separation of the esterification reaction of sucralose.

[0021] Preferably, the distillation temperature in step S1 is 100-110°C.

[0022] Preferably, the volume ratio of methanol to black oil in step S2 is 4-1:1, and the heating in step S2 is heating to 38-45°C.

[0023] Preferably, the lye in step S2 is a 3-8% NaOH solution by mass fraction, and the mass ratio of lye to black oil is 1:3-5; further preferably 1:4.

[0024] Preferably, the addition time of solution 1 in step S2 is 1-1.5h, the holding time is 0.5-1.5h, and the reaction is terminated by heating to 90-98.5°C. The cooling is to 40-43°C.

[0025] Preferably, the mass ratio of crude tin powder, cyclohexane and DMF in step S41 is 1:1.56:1.88; and the separation temperature is 80-85°C.

[0026] Preferably, the mass ratio of acetic anhydride to crude tin powder in step S42 is 0.3-0.5:1, further preferably 0.4:1; and the mixing temperature of acetic anhydride is 70-75°C.

[0027] Preferably, the mass ratio of water to crude tin powder in step S42 is 1:0.8-1, further preferably 1:0.9; and the mixing temperature of water is 40-45°C.

[0028] Preferably, the mass ratio of DMF to crude tin powder in step S43 is 1.88:1.

[0029] Preferably, the distillation temperature in step S44 is 100-110°C.

[0030] The method of the present application further comprises step S5, tin powder recovery: adding lye to the tin ester phase obtained in S44, stirring and reacting to obtain tin powder.

[0031] Preferably, the lye in step S5 is a 3-8% NaOH solution by mass fraction, and the stirring and reaction temperature is 83-87°C.

[0032] Compared with the prior art, the present application has the following beneficial effects:

[0033] 1. The method for recovering tin powder of sucralose in the present application, based on the existing recovery process, uses the cyclohexane phase obtained when using the recovered tin powder to prepare tin ester, and adds a step of washing with DMF and water, thereby solving the problem of low purity of dibutyl tin oxide in the existing sucralose production process and the difficulty in recycling, and the tin powder recovered in the present application has high purity and can be directly recycled.

[0034] 2. The method for recovering tin powder of sucralose in the present application has small differences from the old production process, is easy to operate, and has low investment. DETAILED DESCRIPTION

[0035] The following non-limiting examples can enable those skilled in the art to more fully understand the present application, but do not limit the present application in any way. The following content is only an exemplary description of the scope of the present application, and those skilled in the art can make various changes and modifications to the application disclosed herein, which should also belong to the scope of the present application.

[0036] The present application will be further described below in the form of specific examples. The various chemical reagents used in the examples of the present application are obtained through conventional commercial channels unless otherwise specified. The flocculent used in the present application is the cyclohexane phase obtained after layering treatment of the esterification reaction of sucralose, containing organotin acetate.

[0037] Example 1: A method for recovering tin powder of sucralose

[0038] The method comprises the following steps:

[0039] S1, the flocculent is pumped into a distillation kettle, cyclohexane is distilled out at 100℃, and is allowed to stand and layer, to obtain a DMF-containing water phase and 200mL of black oil generated at the bottom of the kettle;

[0040] S2, 800mL of methanol (purity 99%) and the black oil are mixed, stirred and dissolved, heated to 40℃, to obtain solution 1, which is added dropwise into 50mL of lye (5% NaOH solution by mass fraction) in a neutralization kettle, the dropwise adding time is 1.5h, and the temperature is kept for 0.5h, then heated to 98.5℃, the reaction is completed, the temperature is lowered to 43℃, to obtain an organotin mixture, which is centrifuged and dried, to obtain crude tin powder;

[0041] S3, the crude tin powder is put into a water separation kettle, cyclohexane and DMF are added according to a mass ratio of 1:1.56:1.88, stirred and layered at 80℃, to obtain a DMF-containing water phase and cyclohexane phase 1;

[0042] S4, add acetic anhydride to the cyclohexane phase 1, the mass ratio of acetic anhydride and crude tin powder is 0.3:1, mix at 70℃, cool to 40℃ and add water, the mass ratio of water and crude tin powder is 1:0.8, stir and separate into layers to obtain a DMF-containing aqueous phase and a cyclohexane phase 2;

[0043] S5, add DMF and water to the cyclohexane phase 2 after the separation in step S4, the mass ratio of DMF and tin powder is 1.88:1, wash and separate into layers to obtain a DMF-containing aqueous phase and a cyclohexane phase 3;

[0044] S6, distill the cyclohexane phase 3 obtained in step S5 to obtain a cyclohexane and tin ester phase, and the tin ester phase can be directly used for production.

[0045] Example 2: A method for recovering tin powder from trichlorosucrose

[0046] The method comprises the following steps:

[0047] S1, pump the flocculation into a distillation kettle, distill cyclohexane at 105℃, and separate into layers to obtain a DMF-containing aqueous phase and 270mL of black oil generated at the bottom of the kettle;

[0048] S2, mix 270mL of methanol (purity 99%) and the black oil, stir and dissolve, heat to 45℃ to obtain solution 1, add the solution 1 dropwise into 90mL of lye (4% NaOH solution by mass fraction) in a neutralization kettle, the dropwise adding time is 1.5h, keep warm for 1h, then heat to 95℃, and the reaction is completed, cool to 40℃ to obtain an organotin mixture, centrifuge, and dry to obtain crude tin powder;

[0049] S3, put the crude tin powder into a water separation kettle, add cyclohexane and DMF according to the mass ratio of 1:1.56:1.88, stir and separate into layers at 82℃ to obtain a DMF-containing aqueous phase and a cyclohexane phase 1;

[0050] S4, add acetic anhydride to the cyclohexane phase 1, the mass ratio of acetic anhydride and crude tin powder is 0.4:1, mix at 75℃, cool to 45℃ and add water, the mass ratio of water and crude tin powder is 1:0.9, stir and separate into layers to obtain a DMF-containing aqueous phase and a cyclohexane phase 2;

[0051] S5, add DMF and water to the cyclohexane phase 2 after the separation in step S4, the mass ratio of DMF and tin powder is 1.88:1, wash and separate into layers to obtain a DMF-containing aqueous phase and a cyclohexane phase 3;

[0052] S6, distill the cyclohexane phase 3 obtained in step S5 to obtain a cyclohexane and tin ester phase, and the tin ester phase can be directly used for production.

[0053] Example 3: A method for recovering tin powder from trichlorosucrose

[0054] The method comprises the following steps:

[0055] S1, the flocculation is pumped into a distillation kettle, and cyclohexane is distilled out at 110 DEG C. After standing and layering, a DMF-containing aqueous phase and black oil 250 mL generated at the bottom of the kettle are obtained;

[0056] S2, 500 mL of methanol (purity 99%) and the black oil are mixed, stirred and dissolved, and heated to 40 DEG C to obtain solution 1. Solution 1 is added dropwise into 50 mL of lye (a 3% NaOH solution by mass fraction) in a neutralization kettle, the dropwise adding time is 1 h, and then the temperature is kept for 1.5 h, and then heated to 90 DEG C. After the reaction is completed, the temperature is lowered to 38 DEG C to obtain an organotin mixture. After centrifugation and drying, the crude tin powder is obtained;

[0057] S3, the crude tin powder is put into a water separation kettle, and cyclohexane and DMF are added according to a mass ratio of 1:1.56:1.88. After stirring and layering at 85 DEG C, a DMF-containing aqueous phase and a cyclohexane phase 1 are obtained;

[0058] S4, acetic anhydride is added to the cyclohexane phase 1, and the mass ratio of acetic anhydride to crude tin powder is 0.5:1. After mixing at 75 DEG C, the temperature is lowered to 45 DEG C, and water is added. The mass ratio of water to crude tin powder is 1:1. After stirring and layering, a DMF-containing aqueous phase and a cyclohexane phase 2 are obtained;

[0059] S5, DMF and water are added to the cyclohexane phase 2 after layering in step S4. The mass ratio of DMF to tin powder is 1.88:1. After washing and layering, a DMF-containing aqueous phase and a cyclohexane phase 3 are obtained;

[0060] S6, the cyclohexane phase 3 obtained in step S5 is distilled to obtain a cyclohexane and tin ester phase.

[0061] Comparative Example 1: A method for recovering tin powder from trichlorogalactose

[0062] The difference between the present comparative example and Example 2 is that there is no step of washing and layering with DMF and water.

[0063] Specifically, the method comprises the following steps:

[0064] S1, the flocculation is pumped into a distillation kettle, and cyclohexane is distilled out at 110 DEG C. After standing and layering, a DMF-containing aqueous phase and black oil 250 mL generated at the bottom of the kettle are obtained;

[0065] S2, 500 mL of methanol (purity 99%) and the black oil are mixed, stirred and dissolved, and heated to 40 DEG C to obtain solution 1. Solution 1 is added dropwise into 50 mL of lye (a 3% NaOH solution by mass fraction) in a neutralization kettle, the dropwise adding time is 1 h, and then the temperature is kept for 1.5 h, and then heated to 90 DEG C. After the reaction is completed, the temperature is lowered to 38 DEG C to obtain an organotin mixture. After centrifugation and drying, the crude tin powder is obtained;

[0066] S3, the crude tin powder was put into a water separation kettle, cyclohexane and DMF were added according to the mass ratio of 1:1.56:1.88, and the mixture was stirred and separated at 82°C to obtain a DMF-containing water phase and a cyclohexane phase 1;

[0067] S4, acetic anhydride was added to the cyclohexane phase 1, the mass ratio of acetic anhydride to crude tin powder was 0.4:1, the mixture was uniformly mixed at 75°C, cooled to 45°C and water was added, the mass ratio of water to crude tin powder was 1:0.9, the mixture was stirred and separated to obtain a DMF-containing water phase and a cyclohexane phase 2;

[0068] S5, the cyclohexane phase 2 obtained in step S4 was distilled to obtain a cyclohexane and tin ester phase, and the tin ester phase could not be directly used for production.

[0069] Comparative Example 2: A method for recovering tin powder from trichloro sucralose

[0070] The difference between this comparative example and Example 2 is that the amount of DMF in the washing and separation step is different.

[0071] Specifically, the method comprises the following steps:

[0072] S1, the flocculation was pumped into a distillation kettle, cyclohexane was distilled out at 105°C, and the mixture was allowed to stand and separate to obtain a DMF-containing water phase and 270 mL of black oil generated at the bottom of the kettle;

[0073] S2, 270 mL of methanol (purity 99%) and the black oil were mixed, stirred and dissolved, and heated to 45°C to obtain solution 1, the solution 1 was added dropwise into 90 mL of lye (4% NaOH solution by mass fraction) in a neutralization kettle, the dropwise addition time was 1.5 h, the mixture was incubated for 1 h, then heated to 95°C, and the reaction was completed, the mixture was cooled to 40°C to obtain an organotin mixture, the mixture was centrifuged and dried to obtain crude tin powder;

[0074] S3, the crude tin powder was put into a water separation kettle, cyclohexane and DMF were added according to the mass ratio of 1:1.56:1.88, and the mixture was stirred and separated at 82°C to obtain a DMF-containing water phase and a cyclohexane phase 1;

[0075] S4, acetic anhydride was added to the cyclohexane phase 1, the mass ratio of acetic anhydride to crude tin powder was 0.4:1, the mixture was uniformly mixed at 75°C, cooled to 45°C and water was added, the mass ratio of water to crude tin powder was 1:0.9, the mixture was stirred and separated to obtain a DMF-containing water phase and a cyclohexane phase 2;

[0076] S5, DMF and water were added to the cyclohexane phase 2 after the separation in step S4, the mass ratio of DMF to tin powder was 1.78:1, the mixture was washed and separated to obtain a DMF-containing water phase and a cyclohexane phase 3;

[0077] S6, the cyclohexane phase 3 obtained in step S5 was distilled to obtain a cyclohexane and tin ester phase, and the tin ester phase could not be directly used for production.

[0078] Example 3 A method for recovering tin powder from chlorinated sucrose

[0079] The difference between this comparative example and Example 2 is that the amount of DMF in the washing and layering step is different.

[0080] Specifically, the method comprises the following steps:

[0081] S1, the flocculation is pumped into a distillation kettle, and cyclohexane is distilled out at 105°C, and then the mixture is left to layer, to obtain a DMF-containing aqueous phase and 270 mL of black oil generated at the bottom of the kettle;

[0082] S2, 270 mL of methanol (purity 99%) and the black oil are mixed, stirred and dissolved, and heated to 45°C to obtain solution 1, which is added dropwise into 90 mL of lye (4% NaOH solution by mass fraction) in a neutralization kettle, the dropwise adding time is 1.5 h, and then the mixture is incubated for 1 h, heated to 95°C, and cooled to 40°C to obtain an organic tin mixture, which is centrifuged and dried to obtain crude tin powder;

[0083] S3, the crude tin powder is put into a water separation kettle, cyclohexane and DMF are added according to a mass ratio of 1:1.56:1.88, and the mixture is stirred and layered at 82°C to obtain a DMF-containing aqueous phase and a cyclohexane phase 1;

[0084] S4, acetic anhydride is added to the cyclohexane phase 1, the mass ratio of acetic anhydride to crude tin powder is 0.4:1, the mixture is uniformly mixed at 75°C, cooled to 45°C, and water is added, the mass ratio of water to crude tin powder is 1:0.9, the mixture is stirred and layered to obtain a DMF-containing aqueous phase and a cyclohexane phase 2;

[0085] S5, DMF and water are added to the cyclohexane phase 2 after the layering in step S4, the mass ratio of DMF to tin powder is 1.90:1, the mixture is washed and layered to obtain a DMF-containing aqueous phase and a cyclohexane phase 3;

[0086] S6, the cyclohexane phase 3 obtained in step S5 is distilled to obtain cyclohexane and a tin ester phase, and the tin ester phase is not directly used for production.

[0087] The tin ester phases obtained in Examples 1-3 and Comparative Examples 1-3 are respectively added into a 5% NaOH solution by mass fraction, and stirred and reacted at 85°C to obtain tin powder, and the purity of dibutyl tin oxide in the tin powder is detected, and the results are shown in Table 1.

[0088] Table 1 Purity of dibutyl tin oxide in recovered tin powder

[0089] Purity % Example 1 91.2 Example 2 95.8 Example 3 92.7 Comparative Example 1 60.9 Comparative Example 2 62.7 Comparative Example 3 65.9

[0090] From above, the tin powder recovered by the present application has high purity and can be directly reused. The method for recovering tin powder of the present application uses the cyclohexane phase obtained when the recycled tin powder is used to prepare tin ester to add one more step of DMF and water washing, thereby solving the problem that the purity of dibutyl tin oxide recovered in the existing production process of sucralose is not high and the dibutyl tin oxide is difficult to reuse. Meanwhile, the method for recovering tin powder of the present application has small difference from the old production process, is easy to operate and has low investment.

Claims

1. A process for recovery of tin from trichlorogalactose, characterized by, It comprises the following steps: S1, water distillation: remove cyclohexane by distillation of flocculation, and obtain water phase containing DMF and black oil by static stratification, wherein the flocculation is obtained after the esterification reaction of trichloro sucrose is stratified; S2, organic tin recovery: mix the black oil obtained in step S1 with methanol, stir and dissolve, and heat to obtain solution 1; add the solution 1 into lye, heat and react, cool after the reaction is completed, and obtain an organic tin mixture; S3, centrifugal drying: centrifugal and dry the organic tin mixture obtained in step S2 to obtain crude tin powder; S4, water separation and impurity removal: S41, add cyclohexane and DMF to the crude tin powder obtained in step S3, and obtain water phase containing DMF and cyclohexane phase 1 by static stratification; the mass ratio of the crude tin powder, cyclohexane and DMF is 1:1.56:1.88; the stratification temperature is 80-85℃; S42, add acetic anhydride and water into the cyclohexane phase 1 obtained in step S41, mix, stir and stratify to obtain water phase containing DMF and cyclohexane phase 2; the mass ratio of acetic anhydride and crude tin powder is 0.3-0.5:1; the mixing temperature of acetic anhydride is 70-75℃; the mass ratio of water and crude tin powder is 1:0.8-1; the mixing temperature of water is 40-45℃; S43, add DMF and water into the cyclohexane phase 2 obtained in step S42, wash and stratify to obtain water phase containing DMF and cyclohexane phase 3; the mass ratio of DMF and crude tin powder is 1.88:1; S44, distill the cyclohexane phase 3 obtained in step S43 to obtain cyclohexane and tin ester phase, which can be directly used for production.

2. The method of claim 1, wherein, The volume ratio of methanol to black oil in step S2 is 4-1:1, and the heating in step S2 is heating to 38-45℃.

3. The method of claim 1, wherein, The lye in step S2 is NaOH solution with mass fraction of 3-8%, and the mass ratio of lye to black oil is 1:3-5.

4. The method of claim 1, wherein, The adding time of solution 1 in step S2 is 1-1.5h, the heat preservation time is 0.5-1.5h, the reaction end is heating to 95-98.5℃, and the cooling is cooling to 40-43℃.

5. The method according to any one of claims 1 to 4, characterized in that, It further comprises step S5, tin powder recovery: add lye into the tin ester phase obtained in S44, stir and react to obtain tin powder.