A method for preparing acesulfame potassium

Abstract

The present application discloses a method for preparing acesulfame potassium, comprising the following steps: step 1: reacting aminosulfonic acid and amine to obtain aminosulfonic acid amine salt; step 2: reacting aminosulfonic acid amine salt with diketene to obtain a first material; step 3: reacting the first material with sulfur trioxide solution to obtain a second material; step 4: reacting the second material with a hydrolyzate to obtain a third material; step 5: reacting the organic phase separated from the third material with a potassium-containing compound to obtain acesulfame potassium; in step 3, the acetoacetyl-N-sulfanilic acid amine salt in the first material and sulfur trioxide are continuously reacted at a constant amount ratio of substance. The present application has the advantage of continuous reaction.

Description

Technical Field

[0001] The invention relates to the field of chemical industry, and in particular to a method for preparing acesulfame potassium. Background Art

[0002] Acesulfame potassium, also known as AK sugar (Acesulfame-K), has a chemical name of 6-Methyl-1,2,3-oxathiazin-4(3H)-one 2,2-dioxide potassium salt, commonly known as acesulfame potassium; it appears as colorless crystals; it is easily soluble in water, with a solubility of 270 g / L at 20°C; CAS number: 55589-62-3; molecular weight: 201.24; melting point (°C): 229-232; relative density (water = 1): 1.81; pH: pH = 5.5-7.5.

[0003] Acesulfame potassium has the advantages of being safe and non-toxic, stable in nature, sweet and refreshing, without bad aftertaste, and affordable, and is widely used as a sweetener in food, medicine, and other fields.

[0004] At present, the aminosulfonic acid-sulfur trioxide method is the mainstream process for producing acesulfame potassium because of its easy availability of raw materials, mild reaction conditions, high product yield and high purity. The research on acesulfame potassium is gradually deepening with the development.

[0005] In the prior art, CN113454075A focuses on the acidity and alkalinity of the cyclization reaction; CN111377882A proposes a microreactor for rapid reaction; and CN113508110A proposes a reaction under pressure mixing in a reactor.

[0006] However, sulfur trioxide as a cyclizing agent needs to be dissolved in a solvent. In current production practice, dichloromethane is often used as a solvent for various reasons. Dichloromethane has a relatively excellent effect. However, after sulfur trioxide is dissolved in dichloromethane, due to the exothermic reaction during the cyclization reaction, it is generally reacted at a low temperature (-30 to 0°C). In the reaction, it is always hoped that the occurrence of side reactions can be reduced to reduce the generation of impurities and minimize the decomposition of the product. Summary of the invention

[0007] The inventors found that the sulfur trioxide cyclization agent used in the prior art has a high viscosity, and the use of microchannel reaction has the problem of being easily blocked and requiring a large load pressure; using an ordinary reactor for reaction has the problem of long reaction time, more side reactions, and serious product decomposition, resulting in reduced yield and increased impurities, which are very unfavorable. In addition, due to the above problems, the cyclization reaction is usually carried out in a reactor, which results in the reaction being unable to proceed continuously. The inability to proceed continuously reduces the automation control capability of the reaction equipment.

[0008] The object of the present invention is to provide a method for preparing acesulfame potassium.

[0009] To achieve the above-mentioned purpose and other related purposes, the present invention adopts the following technical solutions:

[0010] A method for preparing acesulfame potassium comprises the following steps:

[0011] Step 1: Mixing aminosulfonic acid and amine to obtain aminosulfonic acid amine salt;

[0012] Step 2: reacting aminosulfonic acid amine salt with diketene to obtain a first material;

[0013] Step 3: reacting the first material with a sulfur trioxide solution to obtain a second material;

[0014] Step 4: reacting the second material with the hydrolyzate to obtain a third material;

[0015] Step 5: reacting the organic phase separated from the third material with a potassium-containing compound to obtain acesulfame potassium;

[0016] In step 3, the acetoacetyl-N-sulfanilic acid amine salt in the first material and sulfur trioxide are continuously reacted at a constant molar ratio.

[0017] The sulfur trioxide solution is a solution of sulfur trioxide in an inert organic solvent.

[0018] The sulfur trioxide solution is a solution of sulfur trioxide in dichloromethane.

[0019] Wherein in step 1, amine is triethylamine.

[0020] The mass fraction of acetoacetyl-N-sulfanilic acid amine salt in the first material is greater than 35%.

[0021] In step 4, the first material and the sulfur trioxide solution are added to the cyclization reaction device in a constant ratio.

[0022] The first material and the sulfur trioxide solution are both sprayed to the reaction position using a spray device.

[0023] The reaction position is a slope, and the slope is connected to the reactor.

[0024] In step 3, the second material overflows out of the reactor.

[0025] It also includes a first material injection device electrically connected to the controller, a sulfur trioxide solution injection device, a first sulfur trioxide solution container, and a second sulfur trioxide solution container.

[0026] It also includes a one-way valve; wherein the controller controls the opening and flow of the first material injection device and the sulfur trioxide solution injection device according to the manually set value; the controller compares the difference between the material level of the first sulfur trioxide solution container and the set value, and controls the opening of the one-way valve between the first sulfur trioxide solution container and the second sulfur trioxide solution container.

[0027] The pressure of the first sulfur trioxide solution container is greater than the pressure of the second sulfur trioxide solution container.

[0028] The present invention can be carried out continuously. The material containing the intermediate DKA and the sulfur trioxide solution are sprayed onto the inclined surface in a fixed ratio by spraying. The sprayed materials are conveniently and evenly mixed and then flow into the reaction tank. After the reaction is completed, the materials overflow from the other end of the reaction tank and are then discharged. In this way, the reaction tank is small in size, simple to control, and continuous in reaction. The requirements for the refrigeration capacity and volume of the equipment are low, and the equipment cost is reduced. The storage and use of sulfur trioxide are safe. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a front view of a single-side inclined overflow reaction tank;

[0030] Figure 2 for Figure 1 Right view of;

[0031] Figure 3 This is the control schematic diagram of the sulfur trioxide solution injection equipment. DETAILED DESCRIPTION

[0032] The following is an explanation of the embodiments of the present invention by specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the process equipment or devices not specifically noted in the following embodiments all adopt conventional equipment or devices in the art. In addition, it should be understood that one or more method steps mentioned in the present invention do not exclude the presence of other method steps before and after the combination step or the insertion of other method steps between these explicitly mentioned steps, unless otherwise specified; it should also be understood that the combined connection relationship between one or more devices / devices mentioned in the present invention does not exclude the presence of other devices / devices before and after the combination device / device or the insertion of other devices / devices between these explicitly mentioned two devices / devices, unless otherwise specified. Moreover, unless otherwise specified, the numbering of each method step is only a convenient tool for identifying each method step, rather than limiting the order of arrangement of each method step or limiting the scope of the present invention. The change or adjustment of its relative relationship, without substantial change in the technical content, should also be regarded as the scope of the present invention.

[0033] A method for preparing acesulfame potassium comprises the following steps: step 1: reacting aminosulfonic acid and amine to obtain aminosulfonic acid amine salt; reacting aminosulfonic acid with amine to form aminosulfonate, triethylamine is commonly used as amine and triethylammonium aminosulfonate is produced. Amine can also be selected from trimethylamine, tri-n-butylamine, triisobutylamine, triisopropylamine and mixtures thereof. Generally, acetic acid is also added to aminosulfonic acid and amine to initiate and effectively maintain the reaction. Since the reaction is usually carried out under excess amine, the addition of acetic acid plays a role in catalysis and neutralization of amine.

[0034] Step 2: reacting aminosulfonic acid amine salt with diketene to obtain the first material; aminosulfonic acid salt reacts with acetyl acetylating agent to form acetyl acetylsulfanilic acid triethylamine salt, preferably acetyl acetylamide-N-sulfonic acid triethylammonium salt. The acetyl acetylating agent contains diketene. Taking the formation of acetyl acetylsulfanilic acid triethylamine salt as an example, acetyl acetylamide-N-sulfonic acid triethylammonium salt and diketene are used as reactants and acetyl acetylamide triethylammonium salt is produced. Organic solvents can be used for the formation reaction of ammonium aminosulfonic acid salt and the formation reaction of acetyl acetylsulfanilic acid triethylamine salt, and the organic solvent is preferably dichloromethane, chloroform, trichloroethylene, acetone, glacial acetic acid and a mixture thereof. As shown in the following formula, acetyl acetylsulfanilic acid triethylamine salt has isomers. These two isomers can be converted to each other. This conversion affects the increase in yield and the reaction time.

[0035]

[0036] Step 3: reacting the first material with a sulfur trioxide solution to obtain a second material; this step is a cyclization step. Acetoacetylsulfanilic acid triethylamine salt is reacted with a cyclizing agent in the presence of a solvent to form a cyclic sulfur trioxide adduct composition. The sulfur trioxide adduct may contain multiple sulfur trioxides. The solvent used for the cyclization reaction is preferably dichloromethane, acetone, glacial acetic acid, trichloroethylene and a mixture thereof.

[0037] Step 4: reacting the second material with the hydrolysis solution to obtain the third material; i.e., the hydrolysis step. The cyclic sulfur trioxide adduct can be hydrolyzed by conventional means (e.g., adding water or other aqueous solutions) to hydrolyze the cyclic sulfur trioxide adduct to form acesulfame (ACH). After hydrolysis, water as a solvent dissolves sulfuric acid, and the target product ACH is mostly dissolved in the organic phase.

[0038] Step 5: reacting the organic phase in the third material with a potassium-containing compound to produce acesulfame potassium, i.e., a neutralization step. Neutralization of ACH with an alkali produces a crude acesulfame potassium composition, which contains acesulfame potassium and some impurities.

[0039] The key content of the present invention lies in step 3, wherein the first material, that is, a mixture containing triethylamine acetoacetyl-N-sulfanilic acid (DKA) and sulfur trioxide are continuously reacted at a constant molar ratio.

[0040] In the prior art, after obtaining the first material, the first material is placed in a reactor, and then the reactor is cooled to -30°C, and then a sulfur trioxide solution is added dropwise. Sulfur trioxide reacts with DKA to produce sulfur trioxide adducts. This reaction process is violent and releases a large amount of heat. Generally speaking, continuous cooling is required to maintain the reaction at a low temperature, and the reaction needs to be maintained for a period of time depending on the speed of sulfur trioxide addition.

[0041] In view of this situation, the inventor proposed a new method to change the cyclization reaction: the sulfur trioxide solution and the first material are sprayed and mixed at the same time, reacted directly after mixing, and then flowed out of the reactor. Due to the high viscosity of the sulfur trioxide solution, it needs to be pressurized when sprayed out. However, the overall pressurization has high requirements for equipment and is not conducive to safety. Therefore, the inventor designed a segmented pressurization method. After sulfur trioxide is sprayed, it is necessary to maintain a certain reaction time with the first material. The inventor designed a single-sided inclined overflow reaction tank.

[0042] See also Figure 1 The single-side inclined overflow reaction tank comprises an inclined surface 1 and a reaction tank 2. Figure 2 yes Figure 1The right view shows the overflow port 3. The sulfur trioxide solution and the first material are simultaneously sprayed onto the reaction position, that is, the single-sided inclined surface, and the spray landing areas overlap. In this way, the sulfur trioxide solution and the first material are uniformly mixed in liquid form, and after mixing, they slowly flow into the overflow reaction tank along the single-sided inclined surface. The other side opposite to the inclined surface is the overflow port, and the overflow port height is lower than the side height of the reaction tank. The reaction liquid flows into the reaction tank from the side, and the mixed liquid that has completed the reaction on one side of the overflow port overflows from the overflow port. In this way, a continuous reaction is achieved. Multiple injectors can be used for injection, and the injector can be a Venturi injector. The landing area of ​​the injector can be designed to be generally long and narrow.

[0043] The inclined plane is provided to form a stable gradient reaction material in the reaction tank. After spraying on the inclined plane, the spray liquid can flow down the inclined plane into the reaction tank after mixing. If spraying directly into the reaction tank, the chaotic flow of the reaction liquid will be caused, which is not conducive to the complete reaction. The inclination angle of the inclined plane relative to the reaction tank is 20-30°.

[0044] The flow of the reaction liquid in the reaction tank can be designed by the overall capacity of the reaction tank. For example, if the injection volume per hour is 2000L, the overall capacity of the reaction tank can be selected as 2000L, and the reaction time can be controlled. The reaction degree gradient contour line in the reaction tank is basically parallel to the overflow port, so the reaction can be fully carried out.

[0045] In order to control the injection of the sulfur trioxide solution, a controller is used in the present invention to control the sulfur trioxide solution. Figure 3 , wherein the second sulfur trioxide solution container 4 is connected to the first sulfur trioxide solution container 5, the first container 5 is connected to the sulfur trioxide solution injection device 6; the sulfur trioxide solution injection device, the first sulfur trioxide solution container, and the second sulfur trioxide solution container are all electrically connected to the controller 7. A first material injection device (not shown) electrically connected to the controller is also included.

[0046] The first container of sulfur trioxide solution can pressurize the stored sulfur trioxide solution, and after pressurization, it can be sprayed out through the sulfur trioxide solution spraying device 6. In order to reduce the energy consumption of the pressure device and improve safety, and prevent the large amount of sulfur trioxide from spraying out and causing damage, a one-way valve is set between the first container of sulfur trioxide solution and the second container of sulfur trioxide solution; the first container of sulfur trioxide solution can accept the material delivery of the second container of sulfur trioxide solution, so that the first container of sulfur trioxide solution and the second container of sulfur trioxide solution can use different pressure control strategies. The controller controls the opening and flow of the first material spraying device and the sulfur trioxide solution spraying device according to the artificial setting value; the controller compares the difference between the material level of the first container of sulfur trioxide solution and the calculated value according to the artificial setting value. For example, when the material level in the first container is maintained at 30%, or 40%, the one-way valve between the first container of sulfur trioxide solution and the second container of sulfur trioxide solution is controlled to open, and sulfur trioxide solution is fed into the first container of sulfur trioxide solution. In this way, the pressure of the first container of sulfur trioxide solution is greater than the pressure of the second container of sulfur trioxide solution, which is prepared for the injection of high-viscosity fluid at low temperature.

[0047] In the present invention, the sulfur trioxide solution and the first material are mixed with a fixed amount of substance, that is, a mixed reaction of DKA and sulfur trioxide with a fixed amount of substance is achieved, which is very effective in reducing the generation of side reactions and improving the yield.

[0048] Example 1

[0049] 10000mol of aminosulfonic acid is dissolved in about 35000-42000mol of dichloromethane. At the end of the reaction, the pH value of the solution is detected, and the pH value is between 6.5 and 7. Then 10500-10150mol of triethylamine is added dropwise to the solution of the previous step, and stirring is performed while dropping, and the dropping time is about 4 hours. Then glacial acetic acid is added dropwise to the solution of the previous step, and the amount of glacial acetic acid is the reaction amount of the remainder of triethylamine, and stirring is performed while dropping, and the temperature is maintained at 15°C for 2 hours. Then, 10500-10150mol of diethylene ketone is added dropwise to the solution of the previous step, and the reaction starting conditions are controlled to be 10°C, and stirring is performed while dropping, and the dropping is performed for about 5 hours. During the dropping process, the reaction solution is controlled to heat up slightly, and the temperature is finally controlled to be 25°C; then it is transferred to a reactor, and the temperature is gradually lowered, and the reaction is reacted for 60 minutes under temperature control conditions, and the final temperature value is 3-5°C. After the reaction is completed, the temperature is quickly lowered to about 0°C and used as a raw material for the cyclization reaction.

[0050] The amount of DKA in the reactants was detected, and the mass fraction of DKA was about 41.9%.

[0051] When the first material is obtained, the inventors dissolve 60,000 mol of sulfur trioxide in 120,000 mol of dichloromethane, mix them evenly, and spray them into a single-side inclined overflow reaction tank with the first material at a constant ratio. The temperature of the reaction tank is controlled to be -30°C, and a reaction tank of appropriate length, width, and height is selected. The reaction time of the reactants is controlled to be 30-120 minutes, and the reactants flow out from the overflow port.

[0052] After the reaction is completed, the overflowed reactant is hydrolyzed and the organic phase is extracted. ACH is dissolved in the organic phase. The ACH mass fraction is measured and is about 7.4%.

[0053] Comparative Example 1

[0054] 10000mol of aminosulfonic acid is dissolved in about 35000-42000mol of dichloromethane. At the end of the reaction, the pH value of the solution is detected, and the pH value is between 6.5 and 7. Then 10500-10150mol of triethylamine is added dropwise to the solution of the previous step, and stirring is performed while dropping, and the dropping time is about 4 hours. Then glacial acetic acid is added dropwise to the solution of the previous step, and the amount of glacial acetic acid is the reaction amount of the remainder of triethylamine, and stirring is performed while dropping, and the temperature is maintained at 15°C for 2 hours. Then, 10500-10150mol of diethylene ketone is added dropwise to the solution of the previous step, and the reaction starting conditions are controlled to be 10°C, and stirring is performed while dropping, and the dropping is performed for about 5 hours. During the dropping process, the reaction solution is controlled to heat up slightly, and the temperature is finally controlled to be 25°C; then it is transferred to a reactor, and the temperature is gradually lowered, and the reaction is reacted for 60 minutes under temperature control conditions, and the final temperature value is 3-5°C. After the reaction is completed, the temperature is quickly cooled to about 0°C and used as a raw material for the cyclization reaction.

[0055] The amount of DKA in the reactants was detected, and the mass fraction of DKA was about 41.9%.

[0056] When the first material is obtained, the inventors dissolved 60,000 mol of sulfur trioxide in 120,000 mol of dichloromethane, mixed them evenly, and then dripped the dichloromethane solution of sulfur trioxide into the first material. The reaction temperature was maintained at -30°C and the reaction was maintained for 120-300 minutes.

[0057] After the reaction was completed, the reactants were hydrolyzed and the organic phase was extracted. ACH was dissolved in the organic phase. The ACH mass fraction was measured and was about 5.1%.

[0058] In the embodiment of the present invention, the first material and the sulfur trioxide solution are added in equal proportions. Therefore, during the reaction, there is no excess material, which reduces the occurrence of side reactions. The reaction time of the reactants in the reaction tank is short, and the possibility of product decomposition is significantly reduced. These two factors are the main reasons for the increase in the ACH content in the method of the present invention. The comparative example is a conventional process, in which the components in the solution are always changing during the reaction, affecting the reaction.

[0059] From the perspective of overall equipment cost, due to continuous reaction, the reactor, cooling device, etc. are all miniaturized equipment, and the price is significantly reduced; in addition, after continuous operation, the number of on-site operators is reduced and automatic control can be achieved.

[0060] Due to the continuous operation, the equipment no longer needs the two steps of discharging and feeding, and the overall utilization rate of the equipment is improved. Continuous production can also be achieved using microchannels, but the amount of microchannel reaction is small. The present invention makes continuous production on an industrial scale possible, reduces production costs, and improves product quality.

[0061] The above examples are for the purpose of illustrating the embodiments disclosed by the present invention and are not to be construed as limitations of the present invention. In addition, the various modifications listed herein and the variations of methods and compositions in the invention are obvious to those skilled in the art without departing from the scope and spirit of the present invention. Although the present invention has been specifically described in conjunction with various specific preferred embodiments of the present invention, it should be understood that the present invention should not be limited to these specific embodiments. In fact, various modifications obvious to those skilled in the art as described above to obtain the invention should be included within the scope of the present invention.

Claims

1. A method for preparing acesulfame potassium, comprising the steps of: Step 1: Mixing aminosulfonic acid and amine to obtain aminosulfonic acid amine salt; Step 2: reacting aminosulfonic acid amine salt with diketene to obtain a first material; Step 3: reacting the first material with a sulfur trioxide solution to obtain a second material; Step 4: reacting the second material with the hydrolyzate to obtain a third material; Step 5: reacting the organic phase separated from the third material with a potassium-containing compound to obtain acesulfame potassium; Features: In step 3, the acetoacetyl-N-sulfanilic acid amine salt in the first material and sulfur trioxide are continuously reacted at a constant amount ratio, wherein the first material and the sulfur trioxide solution are both sprayed to the reaction position using a spray device, and the spray landing area overlaps, wherein the reaction position is a slope, and the slope is connected to the reactor, wherein in step 3, the second material overflows the reactor.

2. The method for preparing acesulfame potassium as claimed in claim 1, characterized in that: The sulfur trioxide solution is a solution of sulfur trioxide in an inert organic solvent.

3. The method for preparing acesulfame potassium as claimed in claim 1, characterized in that: The sulfur trioxide solution is a solution of sulfur trioxide in dichloromethane.

4. The method for preparing acesulfame potassium as claimed in claim 1, characterized in that: Wherein in step 1, amine is triethylamine.

5. The method for preparing acesulfame potassium as claimed in claim 1, characterized in that: The mass fraction of acetoacetyl-N-sulfanilic acid amine salt in the first material is greater than 35%.

6. The method for preparing acesulfame potassium as claimed in claim 1, characterized in that: In step 3, the first material and the sulfur trioxide solution are added to the cyclization reaction device in a constant ratio.

7. The method for preparing acesulfame potassium as claimed in claim 1, characterized in that: It also includes a first material injection device electrically connected to the controller, a sulfur trioxide solution injection device, a first sulfur trioxide solution container, and a second sulfur trioxide solution container.

8. The method for preparing acesulfame potassium as claimed in claim 7, characterized in that: It also includes a one-way valve; wherein the controller controls the opening and flow of the first material injection device and the sulfur trioxide solution injection device according to the manually set value; the controller compares the difference between the material level of the first sulfur trioxide solution container and the set value, and controls the opening of the one-way valve between the first sulfur trioxide solution container and the second sulfur trioxide solution container.

9. The method for preparing acesulfame potassium as claimed in claim 8, characterized in that: The pressure of the first sulfur trioxide solution container is greater than the pressure of the second sulfur trioxide solution container.

Images