CN113956186A - Preparation method of sodium cyclamate - Google Patents
Preparation method of sodium cyclamate Download PDFInfo
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- CN113956186A CN113956186A CN202111293873.2A CN202111293873A CN113956186A CN 113956186 A CN113956186 A CN 113956186A CN 202111293873 A CN202111293873 A CN 202111293873A CN 113956186 A CN113956186 A CN 113956186A
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- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C303/00—Preparation of esters or amides of sulfuric acids; Preparation of sulfonic acids or of their esters, halides, anhydrides or amides
- C07C303/34—Preparation of esters or amides of sulfuric acids; Preparation of sulfonic acids or of their esters, halides, anhydrides or amides of amides of sulfuric acids
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- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C303/00—Preparation of esters or amides of sulfuric acids; Preparation of sulfonic acids or of their esters, halides, anhydrides or amides
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Abstract
A method for preparing sodium cyclamate comprises the following steps: step 1: synthesis reaction, step 2: neutralization reaction, step 3: distillation, step 4: decoloring and neutralizing step 5: and (5) purifying by a rectifying tower. The raw material cyclohexylamine can be recycled after dehydration and purification by a rectifying tower.
Description
Technical Field
The invention belongs to the technical field of sweetener processing, and relates to a preparation method of sodium cyclamate.
Background
The chemical name of the sodium cyclamate is cyclohexyl sulfamic acid sodium, which is a chemical product generated by reacting cyclohexyl sulfamic acid synthesized by using cyclohexylamine as a raw material with sodium hydroxide, and is one of the types of commonly used additives in the current food processing. The sweetness of the sodium cyclamate is about 50 times that of sucrose, so the sodium cyclamate is often used as sugar substitute products, and the application fields comprise beverages, biscuits, frozen drinks and the like.
The sodium cyclamate is discovered by an American student in 1937, and is popular with the food production and processing enterprises due to low cost and high economic value. At present, sodium cyclamate has become an important sugar substitute product in the food processing industry. The production cost of the sodium cyclamate in China is far lower than that of the sodium cyclamate in China, so the sodium cyclamate has great advantages in export. At the present stage, China has become the biggest global sodium cyclamate production and export country, the application of sodium cyclamate in China mainly relates to the industries of medicine, cold drink, beverage and the like, and the share of sodium cyclamate in domestic and foreign markets also shows a steady increasing trend.
Disclosure of Invention
The invention aims to provide a preparation method of sodium cyclamate.
In order to achieve the above objects and other related objects, the present invention provides the following technical solutions: a method for preparing sodium cyclamate comprises the following steps:
step 1: synthesis reaction
Adding cyclohexylamine into a reaction kettle, stirring, adding sulfamic acid into the reaction kettle, heating the materials in the reaction kettle by using steam to raise the temperature of the materials to 90-100 ℃, stopping steam heating when the sulfamic acid is dissolved in the cyclohexylamine, and raising the temperature of the materials to 120-130 ℃; then controlling the steam pressure to be 1.8-2.2kg, heating for 0.8-1.2h, and then controlling the steam pressure to be 4.5-6.6kg, heating for 20-25 h;
step 2: and (3) neutralization reaction:
adding alkali liquor into the reaction kettle, and then reacting under the stirring condition to obtain reaction feed liquid containing sodium cyclamate;
and step 3: distillation
Adding the reaction liquid into a distillation kettle, heating to boil, distilling off an azeotrope of water and cyclohexylamine, and adding a back-supplementing cyclohexylamine solution into the distillation kettle and continuously distilling when the distilled azeotrope is less than 5-20% of the initial distillation amount; when the pH value of the feed liquid in the distillation kettle is less than or equal to 11, adding alkali liquor into the distillation kettle; when azeotrope of water and cyclohexylamine accounting for 35-70% of the mass of the reaction liquid is distilled out, adding water accounting for 10-30% of the mass of the reaction liquid into the distillation kettle; when the mass ratio of cyclohexylamine in the azeotrope of distilled water and cyclohexylamine is less than or equal to 0.02 percent, adding a crystallization mother liquor into the distillation kettle;
and 4, step 4: dewatering
Adding the azeotrope of the water and the cyclohexylamine obtained in the step (3) into a dehydration kettle, and adding sodium hydroxide for 1-10h under the stirring condition; then stopping stirring, standing for layering, discharging the sodium hydroxide solution below the layering boundary to a storage tank, and discharging the feed liquid above the layering boundary to a cyclohexylamine storage tank;
and 5: purification by rectifying tower
Adding the material liquid in the cyclohexylamine storage tank into a rectifying kettle, then adding toluene and heating, carrying out azeotropic dehydration on the toluene and water, and recovering the toluene and cyclohexylamine when the liquid temperature rises to 140 ℃ along with the water in the toluene circulation.
The preferable technical scheme is as follows: the mass ratio of the cyclohexylamine to the sulfamic acid is 2.5-5: 1.
the preferable technical scheme is as follows: and 2, adding a sodium hydroxide solution into the mixture, and reacting for 1-3h under the stirring condition.
The preferable technical scheme is as follows: condensing ammonia gas and cyclohexylamine generated in the reaction in the step 1, absorbing the ammonia gas by water, and feeding the separated cyclohexylamine into the step 1 for reaction.
The preferable technical scheme is as follows: in the step 3, when the mass ratio of cyclohexylamine in the azeotrope of distilled water and cyclohexylamine is less than or equal to 2 percent, collecting and obtaining a back-feeding cyclohexylamine solution.
The preferable technical scheme is as follows: further comprises a decoloring step: adding the distilled feed liquid into a decoloring kettle, stirring the feed liquid when the feed liquid is added to the amount of 30-60m%, adding hydrochloric acid to ensure that the pH value of the feed liquid is 5.5-7.5, then adding activated carbon, and decoloring under the stirring condition.
The preferable technical scheme is as follows: and (3) carrying out filter pressing on the material liquid obtained by decoloring, opening a reflux pump to reflux after filter pressing and discharging, and when the refluxed material liquid is clear, conveying the material liquid to a crystallization kettle.
The preferable technical scheme is as follows: stirring and starting a vacuum pump when the crystallization kettle is fed with a half of the raw materials; after feeding is finished, a pipeline for conveying feed liquid in vacuum is used for sucking clean, a feeding valve is closed, steam is started to raise the temperature to 55-65 ℃, then a steam valve is closed, concentration, cooling and crystallization are started, whether crystallization occurs in the barrel is observed when the temperature is 45-46 ℃, if crystallization occurs, the steam is closed, and the crystallization temperature is kept for 0.5-1.5 hours and then concentration is carried out; the concentration crystallization temperature is 1-2 ℃ higher than the crystallization temperature, the change of the crystal in the crystallization kettle is continuously observed in the period, if the crystal in the barrel rotates slowly under the stirring work or is in a static state, the steam valve is closed, when the temperature is reduced to 38-42 ℃, the bottom valve of the crystallization kettle is opened, the pipeline in the vacuum suck-back discharge valve is utilized to prevent the pipeline below the bottom valve from being blocked, then the emptying valve of the vacuum buffer barrel is opened, the vacuum pump is released and closed, and the crystallization is finished.
The preferable technical scheme is as follows: stirring and starting a vacuum pump when the crystallization kettle is fed with a half of the raw materials; after feeding is finished, a pipeline for conveying feed liquid in vacuum is used for sucking the feed liquid completely, a feeding valve is closed, steam is started to heat to 75-85 ℃, then the steam valve is closed, concentration, temperature reduction and crystallization are started, whether crystallization occurs in the barrel is observed when the temperature is 65-75 ℃, and the crystallization temperature is not lower than 68 ℃; if crystal appears, keeping the crystallization temperature for concentrating for 1 hour, and then increasing the temperature to 1-2 ℃ for concentrating and crystallizing; keeping the crystallization temperature to be concentrated, if the crystals in the barrel rotate slowly under the stirring work or are in a static state, closing the steam valve, opening the bottom valve of the crystallization kettle, preventing the pipeline below the bottom valve from being blocked by utilizing the pipeline in the vacuum back-suction discharge valve, then opening the emptying valve of the vacuum buffer barrel, discharging the vacuum, and closing the vacuum pump to finish crystallization.
The preferable technical scheme is as follows: placing a centrifugal bag in the centrifugal machine, opening the centrifugal machine to rotate a switch slowly, opening a bottom valve of the crystallization kettle and a pipeline valve to discharge and dewater, and uniformly discharging to avoid overlarge vibration of the centrifugal machine; opening the centrifuge to rapidly switch for dehydration after discharging is finished, and switching off the centrifuge motor when the mother liquor pipeline does not discharge water; pumping the mother liquor in the mother liquor ground tank into a mother liquor storage tank; when the centrifuge stops rotating completely, the mixture is sucked into a drying bin by vacuum.
Due to the application of the technical scheme, compared with the prior art, the invention has the advantages that:
the raw material cyclohexylamine can be recycled after dehydration and purification by a rectifying tower.
Drawings
FIG. 1 is a process flow diagram of the present invention.
Detailed Description
The following description of the embodiments of the present invention is provided for illustrative purposes, and other advantages and effects of the present invention will become apparent to those skilled in the art from the present disclosure.
Please refer to fig. 1. It should be understood that the structures, ratios, sizes, and the like shown in the drawings and described in the specification are for illustrative purposes only and are not intended to limit the scope of the present invention. The following examples are provided for a better understanding of the present invention, and are not intended to limit the invention. The experimental procedures in the following examples are conventional unless otherwise specified. The experimental materials used in the following examples were all purchased from a conventional biochemical reagent store unless otherwise specified.
Example 1: preparation method of sodium cyclamate
A. Reaction:
feeding reaction
1. Reacting with sulfamic acid by heating. The material ratio is as follows: cyclohexylamine 5:1
And pumping the cyclohexylamine into the reaction kettle, starting stirring by a stirring device of the reaction kettle, and then quickly putting the sulfamic acid into the kettle.
Heating for dissolving: heating to liquid temperature of 90-100 deg.C, and stopping heating when the feed liquid is dissolved. The liquid temperature will rise to 130 ℃ and the temperature will also rise to 120 ℃ and 110 ℃ by itself.
The steam pressure of the secondary heating reaction is controlled to be 2kg after heating for 1 hour, the steam pressure is controlled to be 5-6kg after heating for 20-25 hours, and the running conditions of a reflux and cooling water system and a cooling tower system are observed in the reaction.
4. Obvious crystals are observed on the inner wall of the reaction kettle from a sight glass, and the reaction end point is obtained when no ammonia gas is discharged from an ammonia gas observation barrel, so that the cyclohexylamine can be recovered. Firstly closing steam and return valve
And starting a vacuum pump, stopping stirring and recovering for 2-4 hours when the stirring current of the reaction kettle is increased by 10 ampere times, and completing the recovery when no distillation is observed from the recovery keg, thereby synthesizing the cyclohexyl sulfamate through the reaction.
B. Neutralizing:
1. and (3) after the reaction recovery, entering a neutralization process, pumping the sodium hydroxide solution into a reaction kettle, stirring the reaction kettle, stirring and neutralizing for 1-3 hours, and generating the sodium cyclamate after the neutralization is finished.
2. Sodium cyclamate solution. Transferring the reaction product to a distillation process to distill excessive cyclohexylamine.
C. Distilling cyclohexylamine:
1. the reaction liquid is pumped into a distillation kettle to be heated by steam. The steam pressure is about 2-3 kg. When the liquid in the kettle is boiled, azeotrope of water and cyclohexylamine begins to be distilled (the content of cyclohexylamine is about 40 percent). The evaporation speed is about 1000 and 1400 barrels per hour. The temperature is about 100 ℃ and 110 ℃.
2. When a certain amount of distillation is recovered, the distillation rate is significantly reduced. At this time, 3000-5000L of CP water (the content of cyclohexylamine is lower than 2%) should be added for continuous distillation. During the distillation process, the pH value of the feed liquid in the kettle is detected, the pH value is kept to be greater than 12 every 1-2 hours of detection, and if the pH value is lower than 11, alkali liquor is required to be added.
3. When the distillation recovery of the aqueous cyclohexylamine liquid is from 1.5 to 1.8 ten thousand liters, 6000 liters of pure water and 7000 liters of pure water should be added for further distillation. When the distillation is recovered to a 2.5-kiloliter barrel, a sample is taken from a recovery pipe orifice to detect the content of the residual cyclohexylamine. CP water recovery is started when the cyclohexylamine content is below 2%.
4. When the content of the distilled cyclohexylamine is less than 0.2 per mill, 10000-15000L of crystallization mother liquor is pumped for concentration, the concentration specific gravity of the feed liquor reaches 18-20, and the distilled feed liquor is pumped to a neutralization and decoloration kettle. After the feed liquid is discharged, a proper amount of pure water is added to clean the tank wall and the flushing pipeline, and the cleaning water is also pumped into the decoloring kettle.
D. And (3) dehydrating:
pumping 20-27 tons of 40% cyclohexylamine distilled in the distillation process into a dehydration kettle, starting a dehydration barrel for stirring, adding sodium hydroxide into the dehydration barrel for stirring for 2-3 hours, stopping stirring, and standing for layering.
Standing for 1-2 hours, discharging the sodium hydroxide solution below the layering boundary into a storage tank (reaction neutralization), discharging 60% cyclohexylamine into a 60% cyclohexylamine storage tank (for purification in a rectification process),
e rectifying tower purification
Dehydrating according to the principle that the azeotropic points of cyclohexylamine, water, toluene and impurities are different, and removing the impurities to purify the cyclohexylamine requires that: the purity of the cyclohexylamine is more than 98 percent
1. The rectifying still can be used for recovering 6-10 tons of 65 percent cyclohexylamine in each batch. Standing for 30-60 min after feeding, discharging sewage, removing impurities, and determining that the specific gravity is 0.89-0.92
2. 100 kg of toluene is added, 200kg of toluene is heated and circulated, the toluene at the upper layer of the layering liquid level of the water separating barrel is pumped into the tower top through the reflux of the recovery barrel, and the water at the lower layer is uniformly and quickly discharged to the receiving barrel. When the liquid temperature rises to 136-140 ℃ and the vapor temperature rises to 110-120 ℃, the circulation is stopped to recycle the toluene and the cyclohexylamine.
3. And after the recovery, the tower kettle and the pipeline are cleaned by vacuum. Discharging the residual liquid to a residual liquid storage tank or a residual liquid transfer barrel.
F decolorization
Discharging the distilled liquid into a neutralization and decoloration kettle, and neutralizing with hydrochloric acid and decoloring with activated carbon.
1. Neutralization
When the distilled liquid is discharged to a half, the decoloring kettle is started to stir, hydrochloric acid is added, and the pH value is detected by test paper after feeding is finished. The pH value is required to be within the range of 5.5-7.5 Duty. And when the PH value is unqualified, gradually adding hydrochloric acid according to the PH value data, and stirring for 20-30 minutes at intervals. The amount of hydrochloric acid added is quantified according to the pH value,
2. decolorization of
After the neutralization, 200k of activated carbon is added for decolorization to decompose the color of the original liquid, and the time for decolorization is 2-3 hours under stirring.
H. Concentration and crystallization:
1. crystallizing a crystallized product: and when the crystallization kettle is fed with a half of the raw materials, stirring and opening a vacuum pump to pull vacuum. And (3) completely sucking the pipeline by using vacuum after feeding, closing a feeding valve, opening steam, heating to 60 ℃, closing the steam valve, starting concentration, cooling and crystallization, observing whether crystallization occurs in the barrel or not when the temperature is 45-46 ℃, closing the steam if crystals occur, keeping the crystallization temperature for 1 hour, and then concentrating. The concentration crystallization temperature is 1-2 ℃ higher than the crystallization temperature, the change of the crystal in the crystallization kettle is continuously observed during the period, if the crystal in the barrel rotates slowly under the stirring work or is in a static state, the steam valve is closed, when the temperature is reduced to 40 ℃, the bottom valve of the crystallization kettle is opened, the pipeline below the bottom valve is prevented from being blocked by utilizing the pipeline in the vacuum suck-back discharge valve, then the vent valve of the vacuum buffer barrel is opened, the vacuum pump is released and closed, and the crystallization is finished
2. Crystallization of anhydrous products: and when the crystallization kettle is fed with a half of the raw materials, stirring and opening a vacuum pump to pull vacuum. And (3) completely sucking the pipeline by using vacuum after feeding, closing a feeding valve, opening steam, heating to 80 ℃, closing the steam valve, starting concentration, cooling and crystallization, and observing whether crystallization occurs in the barrel when the temperature is 70 ℃, wherein the crystallization temperature is not lower than 68 ℃. If crystal appears, keeping the crystallization temperature and concentrating for 1 hour, increasing the temperature to 1-2 ℃ for concentrating and crystallizing. Keeping crystallization temperature to concentrate, if the crystal in the barrel rotates slowly under stirring or is in a static state, closing the steam valve, opening the bottom valve of the crystallization kettle, preventing the pipeline below the bottom valve from being blocked by utilizing the pipeline in the vacuum suck-back discharge valve, then opening the emptying valve of the vacuum buffer barrel, discharging the vacuum, closing the vacuum pump, and completing crystallization
3. Centrifugation
And (4) placing the centrifuge bag by the centrifuge, opening the centrifuge to rotate a switch slowly, opening a bottom valve of the crystallization kettle and a pipeline valve to discharge and dewater, and uniformly discharging to avoid overlarge vibration of the centrifuge. And opening the centrifuge for rapid switch dehydration after discharging is finished, and switching off the centrifuge motor when the mother liquor pipeline does not produce water. And pumping the mother liquor in the mother liquor ground tank into a corresponding mother liquor storage tank. When the centrifuge stops rotating completely, the water is sucked into the drying bin by vacuum, and the water supply by the vacuum pump is ensured when the vacuum pump is started.
4. Drying
And drying the water-well finished product by a fluidized bed, starting a steam valve for heating, starting a draught fan, then starting an air blower, starting a vibration motor, and then starting charging and drying. The material in the hopper cannot be interrupted in the charging and drying process. The dry and wet conditions of the dried finished product need to be observed frequently, the steam quantity is adjusted, and sampling detection is carried out. The drying temperature is 60-100 ℃.
And after drying, closing the steam, closing the vibration motor after the dry materials run clean, closing the air blower and then closing the induced draft fan.
Example 2: preparation method of sodium cyclamate
A method for preparing sodium cyclamate comprises the following steps:
step 1: synthesis reaction
Adding cyclohexylamine into a reaction kettle, stirring, adding sulfamic acid into the reaction kettle, heating materials in the reaction kettle by using steam, raising the temperature of the materials to 95 ℃, stopping steam heating when the sulfamic acid is dissolved in the cyclohexylamine, and raising the temperature of the materials to 125 ℃; then, the steam pressure is controlled to be 12kg and heated for 1h, and then the steam pressure is controlled to be 6kg and heated for 22 h;
step 2: and (3) neutralization reaction:
adding alkali liquor into the reaction kettle, and then reacting under the stirring condition to obtain reaction feed liquid containing sodium cyclamate;
and step 3: distillation
Adding the reaction liquid into a distillation kettle, heating to boil, distilling an azeotrope of water and cyclohexylamine, and adding a back-supplementing cyclohexylamine solution into the distillation kettle and continuously distilling when the distilled azeotrope is less than 10% of the initial distillation amount; when the pH value of the feed liquid in the distillation kettle is less than or equal to 11, adding alkali liquor into the distillation kettle; when 50% of azeotrope of water and cyclohexylamine is distilled from the reaction liquid, adding 20% of water into the distillation still; when the mass ratio of cyclohexylamine in the azeotrope of distilled water and cyclohexylamine is less than or equal to 0.02 percent, adding a crystallization mother liquor into the distillation kettle;
and 4, step 4: dewatering
Adding the azeotrope of the water and the cyclohexylamine obtained in the step (3) into a dehydration kettle, and adding sodium hydroxide for 5 hours under the stirring condition; then stopping stirring, standing for layering, discharging the sodium hydroxide solution below the layering boundary to a storage tank, and discharging the feed liquid above the layering boundary to a cyclohexylamine storage tank;
and 5: purification by rectifying tower
Adding the feed liquid in the cyclohexylamine storage tank into a rectifying kettle, then adding toluene and heating, carrying out azeotropic dehydration on the toluene and water, and recovering the toluene and cyclohexylamine when the liquid temperature rises to 138 ℃ due to the toluene circulation with water.
The preferable technical scheme is as follows: the mass ratio of cyclohexylamine to sulfamic acid is 3.5: 1.
the preferable technical scheme is as follows: and (3) adding a sodium hydroxide solution in the step 2, and reacting for 2 hours under the stirring condition.
The preferable technical scheme is as follows: condensing ammonia gas and cyclohexylamine generated in the reaction in the step 1, absorbing the ammonia gas by water, and feeding the separated cyclohexylamine into the step 1 for reaction.
The preferable technical scheme is as follows: in the step 3, when the mass ratio of cyclohexylamine in the azeotrope of distilled water and cyclohexylamine is less than or equal to 2 percent, collecting and obtaining a back-feeding cyclohexylamine solution.
The preferable technical scheme is as follows: further comprises a decoloring step: adding the distilled feed liquid into a decoloring kettle, stirring the feed liquid when the feed liquid is added to the amount of 30-60m%, adding hydrochloric acid to ensure that the pH value of the feed liquid is 6.5, then adding activated carbon, and decoloring under the stirring condition.
The preferable technical scheme is as follows: and (3) carrying out filter pressing on the material liquid obtained by decoloring, opening a reflux pump to reflux after filter pressing and discharging, and when the refluxed material liquid is clear, conveying the material liquid to a crystallization kettle.
The preferable technical scheme is as follows: stirring and starting a vacuum pump when the crystallization kettle is fed with a half of the raw materials; after feeding is finished, a pipeline for conveying feed liquid in vacuum is used for sucking the feed liquid completely, a feeding valve is closed, steam is started to raise the temperature to 60 ℃, a steam valve is closed, concentration, temperature reduction and crystallization are started, whether crystallization occurs in the barrel is observed when the temperature is 45.5 ℃, if crystallization occurs, the steam is closed, the crystallization temperature is kept for 1 hour, and then concentration is carried out; the concentration crystallization temperature is higher than the crystallization temperature by 1.5 ℃, the change of the crystal in the crystallization kettle is continuously observed in the period, if the crystal in the barrel rotates slowly under the stirring work or is in a static state, the steam valve is closed, when the temperature is reduced to 40 ℃, the bottom valve of the crystallization kettle is opened, the pipeline below the bottom valve is prevented from being blocked by utilizing the pipeline in the vacuum suck-back discharge valve, then the emptying valve of the vacuum buffer barrel is opened, the vacuum pump is released and closed, and the crystallization is finished.
The preferable technical scheme is as follows: stirring and starting a vacuum pump when the crystallization kettle is fed with a half of the raw materials; after feeding is finished, a pipeline for conveying feed liquid in vacuum is used for sucking the feed liquid completely, a feeding valve is closed, steam is started to heat to 80 ℃, then the steam valve is closed, concentration, temperature reduction and crystallization are started, whether crystallization occurs in the barrel is observed when the temperature is 70 ℃, and the crystallization temperature is not lower than 68 ℃; if the crystal appears, keeping the crystallization temperature for concentrating for 1 hour, and then increasing the temperature to 1.5 ℃ for concentrating and crystallizing; keeping the crystallization temperature to be concentrated, if the crystals in the barrel rotate slowly under the stirring work or are in a static state, closing the steam valve, opening the bottom valve of the crystallization kettle, preventing the pipeline below the bottom valve from being blocked by utilizing the pipeline in the vacuum back-suction discharge valve, then opening the emptying valve of the vacuum buffer barrel, discharging the vacuum, and closing the vacuum pump to finish crystallization.
The preferable technical scheme is as follows: placing a centrifugal bag in the centrifugal machine, opening the centrifugal machine to rotate a switch slowly, opening a bottom valve of the crystallization kettle and a pipeline valve to discharge and dewater, and uniformly discharging to avoid overlarge vibration of the centrifugal machine; opening the centrifuge to rapidly switch for dehydration after discharging is finished, and switching off the centrifuge motor when the mother liquor pipeline does not discharge water; pumping the mother liquor in the mother liquor ground tank into a mother liquor storage tank; when the centrifuge stops rotating completely, the mixture is sucked into a drying bin by vacuum.
The foregoing is illustrative of the preferred embodiment of the present invention and is not to be construed as limiting thereof in any way, and any modifications or variations thereof that fall within the spirit of the invention are intended to be included within the scope thereof.
Claims (10)
1. A method for preparing sodium cyclamate is characterized in that: comprises the following steps:
step 1: synthesis reaction
Adding cyclohexylamine into a reaction kettle, stirring, adding sulfamic acid into the reaction kettle, heating the materials in the reaction kettle by using steam to raise the temperature of the materials to 90-100 ℃, stopping steam heating when the sulfamic acid is dissolved in the cyclohexylamine, and raising the temperature of the materials to 120-130 ℃; then controlling the steam pressure to be 1.8-2.2kg, heating for 0.8-1.2h, and then controlling the steam pressure to be 4.5-6.6kg, heating for 20-25 h;
step 2: neutralization reaction
Adding alkali liquor into the reaction kettle, and then reacting under the stirring condition to obtain reaction feed liquid containing sodium cyclamate;
and step 3: distillation
Adding the reaction liquid into a distillation kettle, heating to boil, distilling off an azeotrope of water and cyclohexylamine, and adding a back-supplementing cyclohexylamine solution into the distillation kettle and continuously distilling when the distilled azeotrope is less than 5-20% of the initial distillation amount; when the pH value of the feed liquid in the distillation kettle is less than or equal to 11, adding alkali liquor into the distillation kettle; when azeotrope of water and cyclohexylamine accounting for 35-70% of the mass of the reaction liquid is distilled out, adding water accounting for 10-30% of the mass of the reaction liquid into the distillation kettle; when the mass ratio of cyclohexylamine in the azeotrope of distilled water and cyclohexylamine is less than or equal to 0.02 percent, adding a crystallization mother liquor into the distillation kettle;
and 4, step 4: dewatering
Adding the azeotrope of the water and the cyclohexylamine obtained in the step (3) into a dehydration kettle, and adding sodium hydroxide for 1-10h under the stirring condition; then stopping stirring, standing for layering, discharging the sodium hydroxide solution below the layering boundary to a storage tank, and discharging the feed liquid above the layering boundary to a cyclohexylamine storage tank;
and 5: purification by rectifying tower
Adding the material liquid in the cyclohexylamine storage tank into a rectifying kettle, then adding toluene and heating, carrying out azeotropic dehydration on the toluene and water, and recovering the toluene and cyclohexylamine when the liquid temperature rises to 140 ℃ along with the water in the toluene circulation.
2. A process for the preparation of sodium cyclamate according to claim 1, characterised in that: the mass ratio of the cyclohexylamine to the sulfamic acid is 2.5-5: 1.
3. a process for the preparation of sodium cyclamate according to claim 1, characterised in that: and 2, adding a sodium hydroxide solution into the mixture, and reacting for 1-3h under the stirring condition.
4. A process for the preparation of sodium cyclamate according to claim 1, characterised in that: condensing ammonia gas and cyclohexylamine generated in the reaction in the step 1, absorbing the ammonia gas by water, and feeding the separated cyclohexylamine into the step 1 for reaction.
5. A process for the preparation of sodium cyclamate according to claim 1, characterised in that: in the step 3, when the mass ratio of cyclohexylamine in the azeotrope of distilled water and cyclohexylamine is less than or equal to 2 percent, collecting and obtaining a back-feeding cyclohexylamine solution.
6. A process for the preparation of sodium cyclamate according to claim 1, characterised in that: further comprises a decoloring step: adding the distilled feed liquid into a decoloring kettle, stirring the feed liquid when the feed liquid is added to the amount of 30-60m%, adding hydrochloric acid to ensure that the pH value of the feed liquid is 5.5-7.5, then adding activated carbon, and decoloring under the stirring condition.
7. A process for the preparation of sodium cyclamate according to claim 6, wherein: and (3) carrying out filter pressing on the material liquid obtained by decoloring, opening a reflux pump to reflux after filter pressing and discharging, and when the refluxed material liquid is clear, conveying the material liquid to a crystallization kettle.
8. The method for preparing sodium cyclamate according to claim 7, wherein: stirring and starting a vacuum pump when the crystallization kettle is fed with a half of the raw materials; after feeding is finished, a pipeline for conveying feed liquid in vacuum is used for sucking clean, a feeding valve is closed, steam is started to raise the temperature to 55-65 ℃, then a steam valve is closed, concentration, cooling and crystallization are started, whether crystallization occurs in the barrel is observed when the temperature is 45-46 ℃, if crystallization occurs, the steam is closed, and the crystallization temperature is kept for 0.5-1.5 hours and then concentration is carried out; the concentration crystallization temperature is 1-2 ℃ higher than the crystallization temperature, the change of the crystal in the crystallization kettle is continuously observed in the period, if the crystal in the barrel rotates slowly under the stirring work or is in a static state, the steam valve is closed, when the temperature is reduced to 38-42 ℃, the bottom valve of the crystallization kettle is opened, the pipeline in the vacuum suck-back discharge valve is utilized to prevent the pipeline below the bottom valve from being blocked, then the emptying valve of the vacuum buffer barrel is opened, the vacuum pump is released and closed, and the crystallization is finished.
9. The method for preparing sodium cyclamate according to claim 7, wherein: stirring and starting a vacuum pump when the crystallization kettle is fed with a half of the raw materials; after feeding is finished, a pipeline for conveying feed liquid in vacuum is used for sucking the feed liquid completely, a feeding valve is closed, steam is started to heat to 75-85 ℃, then the steam valve is closed, concentration, temperature reduction and crystallization are started, whether crystallization occurs in the barrel is observed when the temperature is 65-75 ℃, and the crystallization temperature is not lower than 68 ℃; if crystal appears, keeping the crystallization temperature for concentrating for 1 hour, and then increasing the temperature to 1-2 ℃ for concentrating and crystallizing; keeping the crystallization temperature to be concentrated, if the crystals in the barrel rotate slowly under the stirring work or are in a static state, closing the steam valve, opening the bottom valve of the crystallization kettle, preventing the pipeline below the bottom valve from being blocked by utilizing the pipeline in the vacuum back-suction discharge valve, then opening the emptying valve of the vacuum buffer barrel, discharging the vacuum, and closing the vacuum pump to finish crystallization.
10. A process for the preparation of sodium cyclamate according to claim 8 or 9, characterised in that: placing a centrifugal bag in the centrifugal machine, opening the centrifugal machine to rotate a switch slowly, opening a bottom valve of the crystallization kettle and a pipeline valve to discharge and dewater, and uniformly discharging to avoid overlarge vibration of the centrifugal machine; opening the centrifuge to rapidly switch for dehydration after discharging is finished, and switching off the centrifuge motor when the mother liquor pipeline does not discharge water; pumping the mother liquor in the mother liquor ground tank into a mother liquor storage tank; when the centrifuge stops rotating completely, the mixture is sucked into a drying bin by vacuum.
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