Acesulfame potassium compositions and methods for producing same

Abstract

Compositions and methods for producing high purity acesulfame potassium are described. A method includes the steps of: forming a cyclic sulfur trioxide adduct; hydrolyzing the cyclic sulfur trioxide adduct to form an acesulfame-H composition comprising acesulfame-H; neutralizing the acesulfame-H in the acesulfame-H composition to form a crude acesulfame potassium composition comprising acesulfame potassium and less than 2800 wppm of acetoacetamide-N-sulfonic acid, where the neutralizing step is carried out or maintained at a pH of 11.0 or below 11.0, to form a crude acesulfame potassium composition comprising acesulfame potassium and less than 2800 wppm of acetoacetamide-N-sulfonic acid; and treating the crude acesulfame potassium composition to form a refined acesulfame potassium composition, the refined acesulfame potassium composition comprising acesulfame potassium and less than 37 wppm of acetoacetamide-N-sulfonic acid.

Description

[0001] Related Applications

[0002] This application is a divisional application of a patent application filed on September 14, 2017, with application number 2017800016410 and titled “Acesulfame potassium composition and method for producing the same”.

[0003] This application is related to and claims priority from U.S. Provisional Patent Application No. 62 / 397,484 filed on September 21, 2016 and U.S. Provisional Patent Application No. 62 / 397,495 filed on September 21, 2016, which are incorporated herein by reference in their entireties. Technical Field

[0004] The present invention generally relates to acesulfame potassium and a method for producing acesulfame potassium. More specifically, the present invention relates to a method for producing high-purity acesulfame potassium. Background Art

[0005] Acesulfame potassium has a strong sweet taste and has been used as a sweetener in many food-related applications. In conventional acesulfame potassium production methods, aminosulfonic acid is reacted with an amine (e.g., triethylamine) to form an ammonium amidosulfamic acid salt (e.g., an ammonium amidosulfamic acid salt of trialkylammonium). The ammonium amidosulfamic acid salt is then reacted with a diketene to form an acetoacetamide salt. The acetoacetamide salt can be cyclized, hydrolyzed, and neutralized to form acesulfame potassium. U.S. Patent Nos. 5,744,010 and 9,024,016 disclose exemplary acesulfame potassium production methods.

[0006] Typically, the acetoacetamide salt is intermediately cyclized to form a cyclic sulfur trioxide adduct by reaction with sulfur trioxide in an inorganic or organic solvent. Conventionally used solvents for this reaction are organic solvents such as halogenated aliphatic hydrocarbon solvents, for example, methylene chloride. The adduct formed by the reaction is subsequently hydrolyzed and then neutralized with potassium hydroxide to form acesulfame potassium.

[0007] Acesulfame potassium products and intermediate compositions produced by conventional methods contain undesirable impurities, such as acetoacetamide-N-sulfonic acid. Limits on the content of various impurities are usually set by government regulations or consumer guidelines. It has been proven difficult to separate many of these impurities using standard purification processes such as evaporation, crystallization and / or filtration, resulting in consumer dissatisfaction and failure to meet standards.

[0008] There exists a need for an improved process for producing high purity acesulfame potassium compositions in which the formation of impurities such as acetoacetamide-N-sulfonic acid during synthesis is reduced or eliminated.

[0009] All documents discussed herein are incorporated by reference. Summary of the invention

[0010] The present application discloses a method for producing a refined acesulfame potassium composition, the method comprising the following steps: forming a cyclic sulfur trioxide adduct; hydrolyzing the cyclic sulfur trioxide adduct to form an acesulfame-H composition comprising acesulfame-H; neutralizing the acesulfame-H in the acesulfame-H composition to form a crude acesulfame potassium composition; and treating the crude acesulfame potassium composition to form a refined acesulfame potassium composition, the refined acesulfame potassium composition comprising acesulfame potassium and less than 37 wppm of acetoacetamide-N-sulfonic acid. The neutralization step is preferably performed or maintained at a pH of 11.0 or less than 11.0. The crude acesulfame potassium composition may comprise acesulfame potassium and less than 2800 wppm of acetoacetamide-N-sulfonic acid. The neutralization step may include reacting acesulfame-H with a neutralizer (e.g., potassium hydroxide) in an acesulfame-H / neutralizer reaction mixture to form an acesulfame potassium composition. Potassium hydroxide can be produced via a membrane process and the refined acesulfame potassium composition can contain less than 10wppm of mercury. In some cases, the acesulfame-H / neutralizer reaction mixture contains 1wt%-95wt% of a neutralizer and 1wt%-95wt% of acesulfame-H, based on the total weight of the acesulfame-H / neutralizer reaction mixture. The neutralization step can include neutralizing the acesulfame-H in the acesulfame-H composition to form a crude acesulfame potassium composition further comprising acetoacetamide. In some embodiments, the crude acesulfame potassium composition contains 500wppm-2375wppm of acetoacetamide-N-sulfonic acid and the refined acesulfame potassium composition contains less than 25wppm of acetoacetamide-N-sulfonic acid and further contains less than 25wppm of acetoacetamide. In one embodiment, the neutralization step is performed or maintained at a pH of 9.0-11.0 and the crude acesulfame potassium composition comprises 20 wppm-2500 wppm of acetoacetamide-N-sulfonic acid and the refined acesulfame potassium composition comprises less than 25 wppm of acetoacetamide-N-sulfonic acid and less than 15 wppm of acetoacetamide. In another embodiment, the neutralization step is performed or maintained at a pH of 8-10.3 and the crude acesulfame potassium composition comprises 600 wppm-1200 wppm of acetoacetamide-N-sulfonic acid, and the refined acesulfame potassium composition comprises less than 10 wppm of acetoacetamide-N-sulfonic acid and less than 10 wppm of acetoacetamide. In another embodiment, the neutralization step is performed or maintained at a pH of 8-10.3 and the crude acesulfame potassium composition comprises less than 2400 wppm acetoacetamide-N-sulfonic acid, and the refined acesulfame potassium composition comprises less than 10 wppm acetoacetamide-N-sulfonic acid and less than 10 wppm acetoacetamide.The refined acesulfame potassium composition may contain less than 37 wppm acetoacetamide, for example, less than 20 wppm acetoacetamide. The neutralization step may be performed or maintained at a pH of 9.0-11.0, and / or at a pH of 9.0-10.5, for example, 8.0-10.3, and / or at a temperature below 90°C. The treatment step may include an evaporation step with a residence time of less than 180 minutes. A method for producing a refined acesulfame potassium composition is also disclosed, the method comprising the steps of: reacting aminosulfonic acid with triethylamine to form an ammonium aminosulfonate; reacting the ammonium aminosulfonate with diketone to form an acetoacetamide salt; contacting dichloromethane with sulfur trioxide to form a cyclizer composition; reacting the acetoacetamide salt with sulfur trioxide in the cyclizer composition to form a cyclic sulfur trioxide adduct; and hydrolyzing the cyclic sulfur trioxide adduct to form an acetosulfame-H combination comprising acetosulfame-H. The method comprises the steps of: neutralizing the acetosulfan-H in the acetosulfan-H to form a crude acetosulfan potassium composition comprising acetosulfan potassium and less than 2800 wppm of acetoacetamide-N-sulfonic acid, wherein the neutralization step is performed or maintained at a pH of 11.0 or below 11.0; treating the crude acetosulfan potassium composition to form a refined acetosulfan potassium composition comprising acetosulfan potassium and less than 37 wppm of acetoacetamide-N-sulfonic acid. Preferably, steps (a), (b) and (c) are performed in any order before performing step (d). The neutralization step may be performed or maintained at a pH of 9.0-11.0 and the crude acetosulfan potassium composition may contain 20 wppm-2500 wppm of acetoacetamide-N-sulfonic acid and the refined acetosulfan potassium composition may contain less than 25 wppm of acetoacetamide-N-sulfonic acid and less than 15 wppm of acetoacetamide. The application also describes crude, intermediate and refined acesulfame potassium compositions produced by the methods described herein. In some cases, the application describes acesulfame potassium compositions comprising acesulfame potassium and less than 25wppm of acetoacetamide-N-sulfonic acid and less than 25wppm of acetoacetamide. In some cases, the acesulfame potassium composition further comprises 0.001wppm-5wppm of organic impurities and / or 0.001wppm-5wppm of at least one heavy metal, for example, at least one heavy metal selected from mercury, lead and mixtures thereof. In some cases, the acesulfame potassium composition further comprises mercury present in an amount of 1wppb-20wppm and / or lead present in an amount of 1wppb-25wppm. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] The present invention is described in detail below with reference to the accompanying drawings.

[0012] Figure 1The present invention is a process flow chart of a method for producing acesulfame potassium according to one embodiment of the present invention. DETAILED DESCRIPTION

[0013] introduce

[0014] Conventional methods for producing acesulfame potassium involve reacting aminosulfonic acid with an amine in the presence of acetic acid to form an ammonium sulfamic acid salt. The ammonium sulfamic acid salt is then reacted with an acetoacetylating agent (e.g., diketene) to form an acetoacetamide salt. The acetoacetamide salt is reacted with a cyclizing agent (e.g., sulfur trioxide) to form a cyclic sulfur trioxide adduct. The cyclic sulfur trioxide adduct is then hydrolyzed and neutralized via conventional means to form a crude acesulfame potassium composition comprising acesulfame potassium. The composition is phase separated into an aqueous phase and an organic phase. Most of the acesulfame potassium is separated into the aqueous phase. As used herein, the term "crude acesulfame potassium composition" refers to the initial product of the neutralization step or the aqueous phase formed by the phase separation step (without any further purification). The crude acesulfame potassium composition contains at least 5 wt% acesulfame potassium. The crude acesulfame potassium composition may optionally be treated to form an "intermediate acesulfame potassium composition" and / or a "refined acesulfame potassium composition," which are discussed below.

[0015] It has been shown that conventional acesulfame potassium compositions contain several undesirable impurities, especially acetoacetamide and acetoacetamide salts, for example, acetoacetamide-N-sulfonic acid triethylammonium salt. Acetoacetamide-N-sulfonic acid and its salts may also be present. The content limits for these compounds in refined acesulfame potassium compositions are generally determined by industrial purity standards and / or by standards established for specific end-use products in which acesulfame potassium is used as a sweetener. In some cases, the limits on these impurities are determined by government regulations. For most applications, high acesulfame potassium purity levels are preferred. Therefore, crude acesulfame potassium compositions are typically treated by various processing operations to reduce the presence of these impurities. A non-limiting list of such processing operations includes: evaporation, crystallization and / or filtration.

[0016] Without wishing to be bound by theory, it has now been discovered that the neutralization of the hydrolyzed sulfur trioxide adduct can produce stresses, for example, thermal stresses, on the acesulfame potassium molecule. This thermal stress can also affect acesulfame-H, also known as sweetener acid, which is formed during the hydrolysis step and is a precursor of acesulfame potassium. This stress on acesulfame potassium and possibly acesulfame-H can lead to the degradation of these compounds, leading to the formation of undesirable impurities. In some cases, this stress can lead to the degradation of acesulfame potassium / acesulfame-H into reactants of its formation reaction, for example, acetoacetamide and / or its salts and / or acetoacetamide-N-sulfonic acid, which can lead to the formation of additional impurities.

[0017] It has also now been discovered that the use of specific reaction parameters can advantageously reduce or eliminate stress on acesulfame potassium (or acesulfame-H) and / or reduce or eliminate product degradation, which in turn reduces or eliminates the formation of additional impurities and ultimately yields a high-purity final product.

[0018] In particular, it has been found that conducting the neutralization step within a specific pH range or limit surprisingly reduces or eliminates acesulfame potassium (or acesulfame-H) degradation and impurity formation, examples of which include the formation of acetoacetamide-N-aminosulfonic acid and / or the (re)formation of acetoacetamide salts. Typically, the neutralization step is conducted or maintained at a very high pH level in order to maximize the neutralization of acesulfame-H to acesulfame potassium and minimize the acesulfame-H content in the resulting crude acesulfame potassium composition. The reduced degradation of acesulfame potassium and acesulfame-H directly leads to the formation of a higher purity crude acesulfame potassium composition (discussed above), thereby simplifying subsequent processing operations for forming an intermediate or refined acesulfame potassium composition. The method also advantageously leads to the formation of intermediate and refined acesulfame potassium compositions having low acetoacetamide-N-aminosulfonic acid and / or acetoacetamide content.

[0019] In addition to the stresses formed during the neutralization step, the processing operations used to remove impurities from the acesulfame potassium in the crude acesulfame potassium composition can also cause stress (e.g., thermal stress) on the acesulfame potassium itself (or acesulfame-H), which can also lead to degradation. It is believed that under such stress, acetoacetamide-N-aminosulfonic acid may degrade (and optionally hydrolyze) into acetoacetamide and N-sulfonic acid (and optionally N-sulfonic acid derivatives). Therefore, thermal stress in the processing operation may lead to the formation of additional undesirable by-products, such as acetoacetamide. Advantageously, the reduction in the content of acetoacetamide-N-aminosulfonic acid in the crude acesulfame potassium composition further provides a concomitant reduction in the content of acetoacetamide that may be formed in subsequent processing operations, which leads to improved efficiency and ultimately leads to a reduction in the content of acetoacetamide in the resulting refined acesulfame potassium composition.

[0020] Additional specific terms used herein are now defined. "Acetoacetamide", as used herein, refers to the following molecule:

[0021]

[0022] As used herein, "acetoacetamide-N-sulfonic acid" refers to the molecule shown below. In some cases, acetoacetamide-N-sulfonic acid can be a degradation product of acesulfame potassium or acesulfame-H. The term "acetoacetamide-N-sulfonic acid," as used herein, also includes salts of acetoacetamide-N-aminosulfonic acid, for example, potassium, sodium and other alkali metal salts.

[0023]

[0024] The crude acesulfame composition may be processed to form an intermediate acesulfame potassium composition and a refined acesulfame composition, and the processing steps may include one or more concentration or separation operations.

[0025] "Intermediate acesulfame potassium composition" refers to a composition obtained by concentrating a crude acesulfame potassium composition, such as removing water from the crude acesulfame potassium composition. The intermediate acesulfame potassium composition comprises at least 10 wt% acesulfame potassium, based on the total weight of the intermediate acesulfame potassium composition, and has a higher weight percentage of acesulfame potassium than the crude acesulfame potassium composition.

[0026] "Refined acesulfame potassium composition" refers to a composition obtained (preferably directly) from separation (e.g., crystallization and / or filtration) of an intermediate acesulfame potassium composition. The refined acesulfame potassium composition comprises at least 15 wt% acesulfame potassium, based on the total weight percentage of the refined acesulfame potassium composition, and has a higher weight percentage of acesulfame potassium than the intermediate acesulfame potassium composition.

[0027] "Residence time", as used herein, refers to the period of time that a composition (or stream) to be treated, e.g., a crude acesulfame potassium composition, remains in a particular treatment operation. The residence time begins when the composition to be treated enters the treatment operation, and the residence time ends when the resulting composition (formed via treatment) leaves the treatment operation. As a specific example, the residence time for a concentration operation (e.g., evaporation) refers to the time from when the crude acesulfame potassium composition enters the evaporator until the intermediate acesulfame potassium composition leaves the evaporator. As another example, the residence time for a separation operation (e.g., crystallization) refers to the time from when the crude acesulfame potassium composition enters the crystallizer until the intermediate acesulfame potassium composition leaves the crystallizer.

[0028] "Cyclization reaction time", as used herein, refers to the time from the start of the acetoacetamide salt feed to the termination of the acetoacetamide salt feed. In some cases, if indicated, the cyclization reaction time can include additional time after the termination of the acetoacetamide salt feed, for example, an additional 5 minutes or an additional 1 minute.

[0029] The processing of the crude acesulfame potassium composition may involve one or more operations, for example, a concentration operation and / or a separation operation. Generally, a concentration operation is not considered a separation operation. In some embodiments, (one or more) concentration operations and (one or more) separation operations constitute the total processing of the crude acesulfame potassium composition, which obtains the refined acesulfame potassium composition. In some cases, the total concentration operation may include multiple individual concentration operations or units and the total separation operation may include multiple individual separation operations or units.

[0030] "Wppm" and "wppb," as used herein, mean parts per million or parts per billion, respectively, by weight, and are based on the total weight of the entire respective composition, e.g., the entire crude acesulfame potassium composition or the entire refined acesulfame potassium composition.

[0031] Acesulfame potassium formation (pH control)

[0032] Described herein is a method for producing a high purity acesulfame potassium composition. In one embodiment, the method comprises the steps of forming a cyclic sulfur trioxide adduct, hydrolyzing the cyclic sulfur trioxide adduct to form an acesulfame-H composition comprising acesulfame-H, and neutralizing the acesulfame-H in the acesulfame-H composition (and optionally phase separating the neutralization reaction product) to form a crude acesulfame potassium composition. The crude acesulfame potassium composition comprises acesulfame potassium and impurities (e.g., acetoacetamide-N-sulfonic acid) present in extremely low amounts (if any).

[0033] Other impurities may also be formed during the process steps described above. For example, the formation of a cyclic sulfur trioxide adduct may produce a cyclic sulfur trioxide adduct composition comprising the cyclic sulfur trioxide adduct and additional reaction byproducts and impurities. Similarly, the formation of acesulfame-H may produce an acesulfame-H composition comprising acesulfame-H and additional reaction byproducts and impurities.

[0034] The formation of the cyclic sulfur trioxide adduct may include the following steps: reacting aminosulfonic acid with triethylamine to form an ammonium aminosulfonate; reacting the ammonium aminosulfonate with diketene to form an acetoacetamide salt; contacting a solvent (e.g., methylene chloride) with a cyclizing agent (e.g., sulfur trioxide) to form a cyclizing agent composition; and reacting the acetoacetamide salt with sulfur trioxide in the cyclizing agent composition to form a cyclic sulfur trioxide adduct. The ammonium aminosulfonate formation reaction, the acetoacetamide salt formation reaction, and the contact of the solvent with the cyclizing agent may be performed in any order, as long as these steps are performed before the acetoacetamide salt reacts with the cyclizing agent in the cyclizing agent composition.

[0035] As described above, in the neutralization step, the neutralizing agent neutralizes acesulfame-H to form acesulfame potassium. Importantly, the neutralization step is performed at or maintained at a low pH level and / or the pH of the neutralization step is maintained at a low level, which results in the reduction or elimination of the formation of certain impurities (e.g., acetoacetamide-N-sulfonic acid) in the crude acesulfame potassium composition. In this context, "performed" means that the neutralization step is initiated at a low pH level, and "maintained" means that steps are taken to ensure that the pH remains within the low pH range throughout the neutralization step.

[0036] In one embodiment, the neutralization step is performed or maintained at a pH at or below 11.0, e.g., at or below 10.5, at or below 10, at or below 9.5, at or below 9.0, at or below 8.5, at or below 8.0, at or below 8.0, at or below 7.5, at or below 7.0, or at or below 6.5. In some embodiments, the pH of the neutralization step is performed or maintained below the limits described above (excluding the limits themselves). In terms of ranges, the neutralization step is preferably performed or maintained at a pH of 6.0-11.0, e.g., 7.0-11.0, 7.5-11.0, 9.0-11.0, 9-10.5, 7.0-10.5, 7.0-10.0, 8-10.5, 8-10.3, 8-10, or 7.5-9.0. The pH of the neutralization step is preferably performed or maintained within the ranges described above (excluding the endpoints).

[0037] In a preferred embodiment, the neutralizing step comprises reacting acesulfame-H in the acesulfame-H composition with a neutralizing agent to form an acesulfame potassium composition.

[0038] Utilizing these pH ranges and limits provides excellent conversion of acesulfame-H to acesulfame potassium, while minimizing the acesulfame-H and acesulfame potassium degradation product content in the resulting crude acesulfame potassium composition (and refined acesulfame potassium composition). Although low pH levels are generally desired according to embodiments of the present invention, it has now been found that if the pH of the neutralization step is too low, the conversion of acesulfame-H to acesulfame potassium may be undesirably reduced. If the pH of the neutralization step is too high, acesulfame potassium degrades into undesirable byproducts. It is known that acesulfame-H is less stable than acesulfame potassium, and therefore, is more susceptible to degradation. By using the pH ranges and limits described above, fewer acesulfame-H molecules are degraded into their precursors, such as acetoacetamide, while ensuring the formation of acesulfame potassium. In addition to the reduced acetoacetamide-N-sulfonic acid levels in the crude acesulfame potassium composition, low pH levels can also have a beneficial effect on other impurities that may be formed downstream of the neutralization step. For example, by reducing the acetoacetamide-N-sulfonic acid content, the formation of its decomposition by-products is also reduced during the evaporation and / or crystallization steps.

[0039] The neutralizing agent preferably comprises a potassium-containing compound. Preferably, the neutralizing agent comprises potassium hydroxide. Other suitable examples of neutralizing agents include KHCO3, K2CO3 and potassium alkoxides. In a preferred embodiment, the neutralizing agent comprises an alkali, for example, a hydroxide compound. In the case of using potassium hydroxide, potassium hydroxide can be produced via a membrane process. Alternatively, potassium hydroxide can be produced via an amalgam process.

[0040] The specific method for maintaining the pH in the desired range in the neutralization step can vary widely. In some embodiments, the pH in the neutralization step is carried out or maintained in the desired range by controlling the amount of the neutralizing agent (preferably alkaline compound, e.g., hydroxide) used in the neutralization step. In one embodiment, when a continuous process is used, the pH of the neutralization step is to maintain the pH at which the continuous process is located. In one embodiment, when a batch process is used, the pH of the neutralization step is the final pH of the neutralized reaction mixture, e.g., when a batch operation is completed.

[0041] In some cases, the pH in the neutralization step can be maintained within a desired range by managing the components of the neutralization reaction mixture, which includes acesulfame-H and a neutralizing agent (and a solvent). For example, the composition of the neutralization reaction mixture can include 1 wt%-95 wt% of a neutralizing agent, e.g., 10 wt%-85 wt% or 25 wt%-75 wt%, and 1 wt%-95 wt% of acesulfame-H, e.g., 10 wt%-85 wt% or 25 wt%-75 wt%. These concentrations are based on a mixture of the neutralizing agent and acesulfame-H (excluding the solvent).

[0042] In some embodiments, the temperature at which the treatment of the crude acesulfame potassium composition is carried out is maintained at a low level. Also, in some embodiments, the residence time (of the crude acesulfame potassium composition or its derivative) in one or more operations of the treatment process is maintained at a low level. Using treatment under these parameters advantageously reduces / eliminates the decomposition of acetoacetamide-N-sulfonic acid to other impurities.

[0043] In some embodiments, the treatment of the crude acesulfame potassium composition (e.g., one or more of the steps constituting the treatment operation) is carried out or maintained at low temperature. Preferably, the treatment operation includes a concentration operation and a separation operation and these operations are carried out at low temperature.

[0044] In some embodiments, the concentration operation (e.g., one or more of the steps that make up the concentration operation) is performed or maintained at a low temperature, for example, a temperature below 90° C., for example, below 88° C., below 85° C., below 83° C., below 80° C., below 78° C., below 75° C., below 73° C., below 70° C., below 65° C., below 55° C., below 50° C., or below 46° C. In some cases, the temperature of the concentration operation can be maintained at a temperature above 0° C., for example, above 10° C., above 15° C., above 20° C., above 22° C., above 25° C., above 35° C., above 40° C., or above 50° C. In terms of ranges, the temperature of the concentrating operation can be 0°C-90°C, for example, 25°C-90°C, 55°C-90°C, 10°C-88°C, 10°C-85°C, 75°C-88°C, 80°C-88°C, 15°C-85°C, 75°C-85°C, 20°C-83°C, 20°C-80°C, 22°C-78°C, 25°C-75°C, 25°C-73°C, 15°C-50°C, 25°C-65°C, 22°C-50°C, 20°C-55°C, 25°C-70°C, or 30°C-60°C.

[0045] In some embodiments, the separation operation (e.g., one or more of the steps that make up the separation operation) is performed or maintained at a low temperature, for example, a temperature below 35°C, below 30°C, below 25°C, below 20°C, below 15°C, below 10°C, below 8°C, below 6°C, below 5°C, or below 0°C. In some cases, the temperature of the separation operation can be maintained at a temperature above -25°C, for example, above -10°C, above 0°C, above 5°C, above 10°C, above 15°C, above 25°C, or above 30°C. In terms of ranges, the temperature of the separation operation can be -25°C-35°C, for example, -10°C to 35°C, 0°C-35°C, 5°C-30°C, -10°C to 30°C, -10°C to 25°C, -10°C to 20°C, -10°C to 15°C, 0°C-25°C, or -10°C to 30°C. Using the temperatures described above for the treatment advantageously improves the purity of the final product.

[0046] In some embodiments, the treatment of the crude acesulfame potassium composition, for example, one or more of the steps constituting the treatment operation is carried out or maintained at a low residence time. Preferably, the treatment operation includes a concentration operation and a separation operation and these operations are carried out at a low residence time and / or pH.

[0047] In some embodiments, concentration operation (for example, one or more of the steps constituting concentration operation) is carried out under low residence time or maintained under low residence time.In one embodiment, the residence time is less than 180 minutes, for example, less than 170 minutes, less than 150 minutes, less than 120 minutes, less than 100 minutes, less than 90 minutes, less than 75 minutes, less than 50 minutes, less than 40 minutes, less than 30 minutes, less than 20 minutes, or less than 10 minutes.With regard to lower limit, the residence time can be at least 1 second, for example, at least 10 seconds, at least 1 minute, at least 10 minutes, or at least 15 minutes.With regard to scope, the residence time can be 1 second-180 minutes, for example, 10 seconds-180 minutes, 1 minute-180 minutes, 10 minutes-150 minutes, 1 minute-50 minutes, 1 minute-30 minutes, 10 minutes-100 minutes, 1 minute-80 minutes, 10 minutes-80 minutes, 10 minutes-50 minutes, 15 minutes-90 minutes, or 15 minutes-75 minutes. The same residence time limits and ranges apply to separation operations (eg, one or more of the steps that make up a separation operation). Using the described residence times for a concentration operation and / or a separation operation advantageously improves final product purity.

[0048] In some embodiments, the concentration operation (for example, one or more of the steps constituting the concentration operation) is carried out or maintained at a low pH. In one embodiment, the pH of separation is maintained below 10.0, for example, below 9.5, below 9.0, below 8.5, below 8.0, below 7.5, below 7.0, or below 6.5. With regard to scope, the pH of the concentration operation is preferably maintained at 6.0-10.0, for example, 6.5-9.5, 7.0-9.0, or 7.5-8.5. The same pH limit and scope are applicable to separation operations (for example, one or more of the steps constituting the separation operation). Low pH levels are used for concentration operations or separation operations to advantageously improve final product purity.

[0049] The purified acesulfame potassium composition that has been processed through the process(es) described herein will have a high purity.

[0050] Acesulfame potassium composition

[0051] The crude acesulfame potassium composition is formed by hydrolyzing the cyclic sulfur trioxide adduct to form an acesulfame-H composition and neutralizing the acesulfame-H in the acesulfame-H composition to form a crude acesulfame potassium composition, as discussed herein. The product of the neutralization step is phase separated into an aqueous phase and an organic phase. The crude acesulfame potassium composition can be obtained from the aqueous phase (without any further purification). The crude acesulfame potassium composition comprises a mixture of acesulfame potassium and acetoacetamide-N-sulfonic acid, for example, less than 2800 wppm of acetoacetamide-N-sulfonic acid, for example, less than 2700, less than 2600 wppm, less than 2500 wppm, less than 2400 wppm, less than 2000 wppm, less than 1500 wppm, less than 1000 wppm, less than 500 wppm, or less than 100 wppm. In terms of ranges, the crude acesulfame potassium composition can comprise from 1 wppm to 2800 wppm of acetoacetamide-N-sulfonic acid, e.g., from 1 wppm to 2700 wppm, from 10 wppm to 2700 wppm, from 20 wppm to 2500 wppm, from 100 wppm to 2500 wppm, from 500 wppm to 2500 wppm, from 1500 wppm to 2400 wppm, from 500 wppm to 2375 wppm, from 600 wppm to 2000 wppm, from 900 to 1900 wppm, from 300 wppm to 1500 wppm, from 400 wppm to 1400 wppm, from 600 wppm to 1200 wppm, or from 700 wppm to 1100 wppm.

[0052] The crude acesulfame potassium composition may further comprise acetoacetamide, which may be present in the amounts discussed above for acetoacetamide-N-sulfonic acid.

[0053] A refined acesulfame potassium composition (which is generally suitable for end-consumer use) is formed by treating a crude acesulfame potassium composition to remove impurities. In some cases, the refined acesulfame potassium composition is a commonly sold product. The refined acesulfame potassium composition preferably comprises acesulfame potassium and less than 37wppm, e.g., less than 35wppm, less than 30wppm, less than 25wppm, less than 20wppm, less than 15wppm, less than 12wppm, less than 10wppm, less than 7wppm, less than 5wppm, less than 3wppm, less than 1wppm, less than 0.8wppm, less than 0.5wppm, or less than 0.3wppm of a mixture of acetoacetamide. In some cases, the refined acesulfame potassium composition does not contain acetoacetamide, e.g., is substantially free of acetoacetamide (undetectable). In terms of ranges, the refined acesulfame potassium composition may comprise 1 wppb-37 wppm acetoacetamide, for example, 10 wppb-35 wppm, 10 wppb-25 wppm, 10 wppb-15 wppm, 10 wppb-12 wppm, 10 wppb-10 wppm, 10 wppb-7 wppm, 10 wppb-5 wppm, 10 wppb-3 wppm, 100 wppb-15 wppm, 100 wppb-10 wppm, or 100 wppb-5 wppm.

[0054] The refined acesulfame potassium composition preferably comprises a mixture of acesulfame potassium and less than 37 wppm, e.g., less than 35 wppm, less than 30 wppm, less than 25 wppm, less than 20 wppm, less than 15 wppm, less than 12 wppm, less than 10 wppm, less than 7 wppm, less than 5 wppm, less than 3 wppm, less than 1 wppm, less than 0.8 wppm, less than 0.5 wppm, or less than 0.3 wppm of acetoacetamide-N-sulfonic acid. In some cases the refined acesulfame potassium composition is free of acetoacetamide-N-sulfonic acid, e.g., substantially free of acetoacetamide-N-sulfonic acid (undetectable). In terms of ranges, the refined acesulfame potassium composition may comprise 1 wppb-37 wppm of acetoacetamide-N-sulfonic acid, for example, 10 wppb-35 wppm, 10 wppb-25 wppm, 10 wppb-15 wppm, 10 wppb-12 wppm, 10 wppb-10 wppm, 10 wppb-7 wppm, 10 wppb-5 wppm, 10 wppb-3 wppm, 100 wppb-15 wppm, 100 wppb-10 wppm, or 100 wppb-5 wppm.

[0055] The acetoacetamide-N-sulfonic acid and / or acetoacetamide content can be analyzed in a crude, intermediate or refined acesulfame potassium composition via high performance liquid chromatography (HPLC), based on the European Pharmacopoeia Guide for Thin Layer Chromatography (2017) measurement and adapted for HPLC. The specific assay protocol utilizes an LC system HPLC unit from Shimadzu with a CBM-20 Shimadzu controller and equipped with an IonPac NS1 ((5 μm) 150×4 mm) analytical column and an IonPac NG1 guard column (35×4.0 mm). A Shimadzu SPD-M20A light emitting diode array detector can be used for detection (at 270 nm and 280 nm wavelengths). The analysis can be performed at a column temperature of 23°C. As the first eluent solution, an aqueous mixture of tetrabutylammonium hydrogen sulfate (3.4 g / L), acetonitrile (300 mL / L) and potassium hydroxide (0.89 g / L) can be used; as the second eluent solution, an aqueous mixture of tetrabutylammonium hydrogen sulfate (3.4 g / L) and potassium hydroxide (0.89 g / L) can be used. Elution can be performed in a gradient mode according to the following second eluent flow curve:

[0056] 0-3 minutes: constant 80% (v / v)

[0057] 3-6 minutes: linearly decrease to 50% (v / v)

[0058] 6-15 minutes: Constant at 50% (v / v)

[0059] 15-18 minutes: linearly decrease to 0%

[0060] 18-22 minutes: Constant at 0%

[0061] 22-24 minutes: linear increase to 80% (v / v)

[0062] 24-35 minutes: constant at 80% (v / v).

[0063] The total flow rate of the eluent can be about 1.2 mL / min. and data collection can be calculated using LabSolution software from Shimadzu.

[0064] As described above, the crude acesulfame potassium composition is formed by the aforementioned reaction, hydrolysis and neutralization, and the refined acesulfame potassium composition is formed by treating the crude acesulfame potassium composition. In a preferred embodiment, the neutralization can be carried out at a pH of 11.0 or lower or maintained at a pH of 11.0 or lower, for example, at 10.5 or lower, at 10 or lower, at 9.5 or lower, at 9.0 or lower, at 8.5 or lower, at 8.0 or lower, at 7.5 or lower, at 7.0 or lower, or at 6.5 or lower. (optionally at a pH of 7.5-11, e.g., 9.0-11.0, 9-10.5, 7.0-10.5, 7.0-10.0, 8-10.5, 8-10.3, 8-10, or 7.5-9.0); the crude acesulfame potassium composition may contain less than 2800 acetoacetamide-N-sulfonic acid, e.g., less than 2700 wppm, less than 2600 wppm, less than 2500 wppm, less than 240 0wppm, less than 2000wppm, less than 1500wppm, less than 1000wppm, less than 500wppm, or less than 100wppm (optionally 1wppm-2800wppm of acetoacetamide-N-sulfonic acid, for example, 1wppm-2800wppm, 10wppm-2700wppm, 20wppm-2500wppm, 100wppm-2500wppm m, 500wppm-2500wppm, 1500-2400wppm, 500wppm-2375wppm, 600wppm-2000wppm, 900-1900wppm, 300wppm-1500wppm, 400wppm-1400wppm, 600wppm-1200wppm or 700wppm-1100wppm); and the refined acesulfame potassium composition may contain less than 37wppm of acetoacetamide-N-sulfonic acid, for example, less than 35wppm, less than 30wppm, less than 25wppm, less than 20wppm, less than 15wppm, less than 12wppm, less than 10wppm, less than 7wppm, less than 5wppm, less than 3wppm, less than 1wppm, less than 0.8wppm, less than 0.5wppm, or less than 0.3wppm (optionally 1wppb-37wppm of acetoacetamide-N-sulfonic acid, e.g., 10wppb-35wppm, 10wppb-25wppm, 10wppb-15wppm, 10wppb-12wppm, 10wppb-10wppm, 10wppb-7wppm, 10wppb-5wppm, 10wppb-3wppm, 100wppb-15wppm, 100wppb-10wppm, or 100wppb-5wppm); and less than 37wppm of acetoacetamide, e.g., less than 35wppm, less than 30wppm, less than 25wppm, less than 20wppm, less than 15wppm ppm, less than 12 wppm, less than 10 wppm, less than 7 wppm, less than 5 wppm, less than 3 wppm, less than 1 wppm, less than 0.8 wppm, less than 0.5 wppm, or less than 0.3 wppm (optionally 10 wppb-37 wppm of acetoacetamide, for example, 10 wppb-35 wppm, 10 wppb-15 wppm, 10 wppb-12 wppm, 10 wppb-10 wppm, 10 wppb-7 wppm, 10 wppb-5 wppm, 10 wppb-3 wppm, 100 wppb-15 wppm, 100 wppb-10 wppm, or 100 wppb-5 wppm).

[0065] In particular embodiments, the crude acesulfame potassium composition comprises 500 wppm-2375 wppm of acetoacetamide-N-sulfonic acid and the refined acesulfame potassium composition comprises less than 25 wppm of acetoacetamide-N-sulfonic acid and further comprises less than 25 wppm of acetoacetamide.

[0066] In another specific embodiment, neutralization is performed or maintained at a pH of 9.0-11.0, the crude acesulfame potassium composition comprises 20 wppm-2500 wppm of acetoacetamide-N-sulfonic acid, and the refined acesulfame potassium composition comprises less than 25 wppm of acetoacetamide-N-sulfonic acid and less than 15 wppm of acetoacetamide.

[0067] In another specific embodiment, the neutralization is performed or maintained at a pH of 8.0-10.3 and the crude acesulfame potassium composition comprises 600 wppm-1200 wppm of acetoacetamide-N-sulfonic acid, and the refined acesulfame potassium composition comprises less than 10 wppm of acetoacetamide-N-sulfonic acid and less than 10 wppm of acetoacetamide.

[0068] In another specific embodiment, neutralization is performed or maintained at a pH of 8-10.3, the crude acesulfame potassium composition comprises less than 2400 wppm acetoacetamide-N-sulfonic acid, and the refined acesulfame potassium composition comprises less than 10 wppm acetoacetamide-N-sulfonic acid and less than 10 wppm acetoacetamide.

[0069] In another specific embodiment, neutralization is performed or maintained at a pH of 9.0-11.0, the crude acesulfame potassium composition comprises 500 wppm-2375 wppm of acetoacetamide-N-sulfonic acid, and the refined acesulfame potassium composition comprises 10 wppb-10 wppm of acetoacetamide-N-sulfonic acid and 10 wppb-10 wppm of acetoacetamide.

[0070] Acesulfame potassium composition (crude and / or refined) may contain other impurities in some cases. Exemplary impurities include, but are not limited to, halogenated acesulfame potassium. Acesulfame potassium composition (crude and / or refined) may also contain heavy metals. Organic impurities and / or heavy metals may be present in an amount of 1wppb-25wppm, based on the gross weight of each acesulfame potassium composition (crude or refined), for example, 100wppb-20wppm, 100wppb-15wppm, 500wppb-10wppm, or 1wppm-5wppm. Heavy metals are defined as metals with relatively high density, for example, greater than 3g / cm 3 or greater than 7g / cm 3. Exemplary heavy metals include lead and mercury. In some cases, a crude or refined acesulfame potassium composition may contain mercury in an amount of 1 wppb-25 wppm, for example, 100 wppb-20 wppm, 100 wppb-15 wppm, 500 wppb-10 wppm, or 1 wppm-5 wppm. In terms of limits, a crude or refined acesulfame potassium composition may contain less than 25 wppm of mercury, for example, less than 20 wppm, less than 15 wppm, less than 10 wppm, or less than 5 wppm. In some cases, a crude or refined acesulfame potassium composition may contain lead in an amount of 1 wppb-25 wppm, for example, 100 wppb-20 wppm, 100 wppb-15 wppm, 500 wppb-10 wppm, or 1 wppm-5 wppm. In terms of limits, the crude or refined acesulfame potassium composition may contain less than 25 wppm of lead, for example, less than 20 wppm, less than 15 wppm, less than 10 wppm, or less than 5 wppm. In some cases, when potassium hydroxide is formed via a membrane process, the resulting crude or refined acesulfame potassium composition may have very low levels of mercury, if present, for example, less than 10 wppm, less than 5 wppm, less than 3 wppm, less than 1 wppm, less than 500 wppb, or less than 100 wppb.

[0071] Intermediate reaction parameters

[0072] The reactions for producing high purity acesulfame potassium are described in more detail below.

[0073] Ammonium sulfamate formation reaction

[0074] In the first reaction step, sulfamic acid is reacted with an amine to form a sulfamate salt. An exemplary reaction mechanism using triethylamine as the amine and producing triethylammonium sulfamate is shown in reaction (1) below.

[0075] H2N-SO3H+N(C2H 5)3 →H2N-SO3 - ·HN + (C2H5)3 (1)

[0076] Acetic acid is also present in the first reaction mixture and reacts with an amine (eg, triethylamine) to form triethylammonium acetate as shown below in reaction (2).

[0077] H3C-COOH+N(C2H 5)3 →H3C-COO - ·HN + (C2H5)3 (2)

[0078] The amine used in these reactions can vary widely. Preferably, the amine comprises triethylamine. In one embodiment, the amine can be selected from trimethylamine, diethylpropylamine, tri-n-propylamine, triisopropylamine, ethyldiisopropylamine, tri-n-butylamine, triisobutylamine, tricyclohexylamine, ethyldicyclohexylamine, N,N-dimethylaniline, N,N-diethylaniline, benzyldimethylamine, pyridine, pyridine such as picoline, lutidine, cholidine or methylethylpyridine, N-methylpiperidine, N-ethylpiperidine, N-methylmorpholine, N,N-dimethylpiperazine, 1,5-dimethylpyridine ... -diazabicyclo[4.3.0]-non-5-ene, 1,8-diazabicyclo[5.4.0]-undec-7-ene, 1,4-diazabicyclooctane, tetramethylhexamethylenediamine, tetramethylethylenediamine, tetramethylpropylenediamine, tetramethylbutylenediamine, 1,2-dimorpholinoethane, pentamethyldiethyltriamine, pentaethyldiethylenetriamine, pentamethyldipropylenetriamine, tetramethyldiaminomethane, tetrapropyldiaminomethane, hexamethyltriethylenetetramine, hexamethyltripropylenetetramine, diisobutyltriamine, triisopropylenetriamine and mixtures thereof.

[0079] Acetoacetamide salt formation reaction

[0080] Once formed in reaction (1), the sulfamic acid salt is reacted with an acetoacetylating agent to form an acetoacetamide salt, preferably acetoacetamide-N-sulfonic acid triethylammonium salt. Preferably, the acetoacetylating agent comprises diketene, although other acetoacetylating agents may be used, with or without diketene.

[0081] In one embodiment, the resulting acetoacetamide salt corresponds to the following formula (3).

[0082]

[0083] Among them, M + is an appropriate ion. Preferably, M + Alkali metal ions or N + R1R2R3R4. R1, R2, R3 and R4, independently of each other, may be an organic group or hydrogen, preferably H or a C1-C8 alkyl, C6-C 10 Cycloalkyl, aryl and / or aralkyl. In a preferred embodiment, R1 is hydrogen, and R2, R3 and R4 are alkyl, for example, ethyl.

[0084] An exemplary reaction mechanism for forming acetoacetamide salts uses ammonium sulfamate salts of trialkylammonium and diketene as reactants and produces acetoacetamide triethylammonium salts, which is shown in reaction (4) below.

[0085]

[0086] In one embodiment, the reaction is carried out in the presence of a catalyst, which may vary widely. In some embodiments, the catalyst comprises one or more amines and / or phosphines. Preferably, the catalyst comprises triethylamine. In some cases trimethylamine is used as both catalyst and reactant.

[0087] In one embodiment, wherein the ammonium sulfamate forming reaction and the acetoacetamide forming reaction are carried out in separate reactors, the second reaction mixture comprises the ammonium sulfamate, diketene and a catalyst, e.g., triethylamine. Preferably, the catalyst from the first reaction is carried through the reaction mixture of the second reaction. The second reaction mixture is then subjected to conditions effective for forming the acetoacetamide salt.

[0088] In one embodiment, the composition of the second reaction mixture can be similar to the first reaction mixture. In a preferred embodiment, the reaction product of the ammonium sulfamate forming reaction provides the component of the ammonium sulfamate of the second reaction mixture. In addition to the above-mentioned components, the second reaction mixture can further include reaction byproducts or unreacted initial materials from the first reaction.

[0089] In one embodiment, the amount of acetyl acetylating agent (e.g., diketene) should be at least equimolar to the provided reactant ammonium sulfamate. In one embodiment, the process may utilize less than a 30 mol% excess (e.g., less than a 10 mol% excess) of diketene. Larger excesses are also contemplated.

[0090] Ammonium series sulfamic acid salt formation reaction and / or acetoacetamide salt formation reaction can use organic solvent.Suitable inert organic solvent comprises any organic solvent that does not react with initial material, cyclizing agent, final product and / or catalyst in the reaction in an undesirable manner.Solvent preferably has the ability to dissolve ammonium series sulfamic acid salt at least in part. Exemplary organic solvents include halogenated aliphatic hydrocarbons, preferably having up to 4 carbon atoms, for example, dichloromethane, chloroform, 1,2-dichloroethane, trichloroethylene, tetrachloroethylene, trichlorofluoroethylene; aliphatic ketones, preferably those having 3-6 carbon atoms, for example, acetone, methyl ethyl ketone; aliphatic ethers, preferably cyclic aliphatic ethers having 4 or 5 carbon atoms, for example, tetrahydrofuran, dioxane; lower aliphatic carboxylic acids, preferably those having 2-6 carbon atoms, for example, acetic acid, propionic acid; aliphatic nitriles, preferably acetonitrile; N-alkyl-substituted amides of carbonic acid and lower aliphatic carboxylic acids, preferably amides having up to 5 carbon atoms, for example, tetramethylurea, dimethylformamide, dimethylacetamide, N-methylpyrrolidone; aliphatic sulfoxides, preferably dimethyl sulfoxide, and aliphatic sulfones, preferably sulfolane.

[0091] Particularly preferred solvents include dichloromethane (methylene chloride), 1,2-dichloroethane, acetone, glacial acetic acid and dimethylformamide, with dichloromethane (methylene chloride) being particularly preferred. The solvent may be used alone or in a mixture. In one embodiment, the solvent is a halogenated aliphatic hydrocarbon solvent, preferably methylene chloride. Chloroform and tetrachloromethane are also exemplary solvents.

[0092] In one embodiment, the acetoacetamide salt formation reaction is carried out at a temperature of -30°C to 50°C, for example, 0°C to 25°C. The reaction pressure can vary widely. In a preferred embodiment, the reaction is carried out at atmospheric pressure, although other pressures are also contemplated. The reaction time can vary widely, preferably 0.5 hours to 12 hours, for example, 1 hour to 10 hours. In one embodiment, the reaction is carried out by introducing an ammonium aminosulfonate and metering in diketene. In another embodiment, the reaction is carried out by introducing diketene and metering in an ammonium aminosulfonate. The reaction can be carried out by introducing diketene and ammonium aminosulfonic acid and metering in a catalyst.

[0093] Once formed, each reaction product is optionally subjected to one or more purification steps. For example, the solvent can be separated from the reaction product, for example, via distillation, and the residue (mainly acetoacetamide-N-sulfonate) can be recrystallized from a suitable solvent (e.g., acetone, methyl acetate or ethanol).

[0094] Cyclization and hydrolysis

[0095] The acetoacetamide salt is reacted with a cyclizing agent (e.g., a cyclizing agent in a cyclizing agent composition) in the presence of a solvent to form a cyclic (sulfur trioxide) adduct composition comprising a cyclic sulfur trioxide adduct and impurities in some cases. In some cases, a cooling step is performed before the cyclic sulfur trioxide adduct formation reaction. In one embodiment, the cyclization is achieved by using a cyclizing agent of at least equimolar amount. The cyclizing agent can be dissolved in an inert inorganic or organic solvent. The cyclizing agent is typically used in molar excess, e.g., at most 20 times excess, or at most 10 times excess, based on the total moles of the acetoacetamide salt. An exemplary cyclization reaction using sulfur trioxide as a cyclizing agent is shown in the following reaction (5).

[0096]

[0097] In one embodiment, the weight ratio of solvent to the cyclizing agent in the cyclizing agent composition is at least 1: 1, e.g., at least 2: 1, or at least 5: 1. In one embodiment, the weight ratio of solvent to the cyclizing agent in the cyclizing agent composition is 1: 1-25: 1, e.g., 1: 1-10: 1, 2: 1-10: 1, or 5: 1-10: 1.

[0098] The cyclizing agent can be any compound that initiates the ring closure of the acetoacetamide salt. Although sulfur trioxide is the preferred cyclizing agent, other cyclizing agents are also contemplated.

[0099] The cyclizing agent can be added to the reaction mixture in solid or liquid form or by condensation in the vapor. Suitable inert inorganic or organic solvents are those liquids that do not react with sulfur trioxide or the initial material or final product of the reaction in an undesirable manner. Preferred organic solvents include, but are not limited to, halogenated aliphatic hydrocarbons, preferably having up to four carbon atoms, for example, dichloromethane (dichloromethane), chloroform, 1,2-dichloroethane, trichloroethylene, tetrachloroethylene, trichlorofluoroethylene; carbonic acid and lower aliphatic alcohols, preferably esters with methanol or ethanol; nitroalkanes, preferably having up to four carbon atoms, especially nitromethane; alkyl-substituted pyridines, preferably trimethylpyridine; and aliphatic sulfones, preferably sulfolane. Particularly preferred solvents for cyclization reactions include dichloromethane (dichloromethane), 1,2-dichloroethane, acetone, glacial acetic acid and dimethylformamide, and dichloromethane (dichloromethane) is particularly preferred. Other solvents, for example, other solvents mentioned herein, can also be suitably used as solvents. The solvent can be used alone or in a mixture. In one embodiment, the solvent is a halogenated aliphatic hydrocarbon solvent, preferably dichloromethane. The method can use these solvents alone or in a mixture of solvents.

[0100] In some cases, the solvent in the cyclizing agent composition can be selected from 1) concentrated sulfuric acid, 2) liquid sulfur dioxide, or 3) an inert organic solvent.

[0101] In a preferred embodiment, the same solvent is used for both the acetoacetamide salt formation reaction and the cyclization reaction. As a benefit, the solution obtained in the acetoacetamide salt formation reaction can be used immediately for the cyclization without separating the acetoacetamide salt formation reaction product.

[0102] In one embodiment, the reaction temperature for the cyclization reaction is -70°C to 175°C, e.g., -40°C to 60°C. The pressure at which the reaction is carried out can vary widely. In one embodiment, the reaction is carried out at a pressure of 0.01 MPa to 10 MPa, e.g., 0.1 MPa to 5 MPa. Preferably, the reaction is carried out at atmospheric pressure.

[0103] The acetoacetamide salt can be introduced into the cyclization reactor and the cooled cyclizing agent composition (e.g., a solution of the cyclizing agent optionally in a solvent) can be metered into the reactor. In a preferred embodiment, the two reactants (acetoacetamide salt and cyclizing agent) are fed into the reactor simultaneously. In one embodiment, the cooled cyclizing agent composition is initially introduced into the reactor and the acetoacetamide salt is added. Preferably, at least a portion of the cyclizing agent composition is introduced into the reactor, and then the acetoacetamide salt and (additional) cyclizing agent are metered continuously or in portions, preferably while maintaining the temperature described above.

[0104] The acetoacetamide salt may be introduced into the reactor and the cyclizing agent composition may be metered into the reactor. In a preferred embodiment, the two reactants are fed into the reactor simultaneously. In one embodiment, the cyclizing agent composition is initially introduced into the reactor and the acetoacetamide salt is added. Preferably, at least part of the cyclizing agent composition is introduced into the reactor, and then the acetoacetamide salt and (additional) cyclizing agent are metered in continuously or in portions, preferably while maintaining the temperature described above.

[0105] Forming a crude acesulfame potassium composition from a cyclic sulfur trioxide adduct composition, in some embodiments, comprises the steps of: hydrolyzing the cyclic sulfur trioxide adduct to form an acesulfame-H composition; neutralizing the acesulfame-H in the acesulfame H composition to form a crude acesulfame potassium composition; and forming the acesulfame potassium composition from the crude acesulfame potassium composition.

[0106] The cyclic sulfur trioxide adduct may be hydrolyzed via conventional means (eg, using water). Thus, the forming step may include the step of hydrolyzing the cyclic sulfur trioxide adduct to form an acesulfame-H composition. Acesulfame-H refers to a sweetener acid.

[0107] An exemplary hydrolysis reaction mechanism is shown below in reaction (6).

[0108]

[0109] The addition of water causes phase separation. The majority of the sweetener acid, acesulfame-H (6-methyl-3,4-dihydro-1,2,3-thiazin-4-one-2,2-dioxide), which is formed via hydrolysis, is present in the organic phase, for example, at least 60wt%, at least 70%, at least 80%, or at least 90%. The remainder of the sweetener acid is in the aqueous phase and can be extracted and optionally added to the sweetener acid in the organic phase. In the case where dichloromethane is used as the reaction medium, water or ice, for example, in molar excess (based on sulfur trioxide) can be added to the cyclic sulfur trioxide adduct / sulfur trioxide solution.

[0110] In some cases, the hydrolysis step comprises adding water to the cyclic sulfur trioxide adduct. In preferred embodiments, the weight ratio of water to acetoacetamide salt is greater than 1.3: 1, e.g., greater than 1.5: 1, greater than 1.7: 1, greater than 2: 1, or greater than 2.2: 1. Use of these ratios can result in a reduction in the formation of acetoacetamide-N-sulfonic acid and / or acetoacetamide in the neutralized crude acetosulfame potassium composition, e.g., the crude acetosulfame potassium composition can include acetoacetamide-N-sulfonic acid in the amounts discussed herein.

[0111] After adding water, the reaction solvent (e.g., methylene chloride) can be removed by distillation, or the acesulfame-H remaining in the organic phase can be extracted with a more suitable solvent. Suitable solvents are those that are sufficiently stable to sulfuric acid and have satisfactory dissolving power. Other suitable solvents include esters of carbonic acid, such as dimethyl carbonate, diethyl carbonate and ethylene carbonate, or esters of organic monocarboxylic acids, such as isopropyl formate and isobutyl formate, ethyl acetate, isopropyl acetate, butyl acetate, isobutyl acetate and neopentyl acetate, or esters or amides of dicarboxylic acids immiscible with water, such as tetrabutyl urea is suitable. Particularly preferred are isopropyl acetate and isobutyl acetate.

[0112] The combined organic phases are dried, for example with Na2SO4, and evaporated. Any sulfuric acid carried over from the extraction is removed by appropriately adding an aqueous alkali solution to the organic phase. For this purpose, an aqueous alkali solution may be added to the organic phase until the pH reached in the water corresponds to the pH of pure 6-methyl-3,4-dihydro-1,2,3-thiazin-4-one-2,2-dioxide at the same concentration in the same two-phase system of extractant and water.

[0113] Neutralization

[0114] Neutralization of acesulfame-H produces a non-toxic salt of acesulfame-H, e.g., acesulfame potassium. In one embodiment, neutralization is performed by reacting acesulfame-H with an appropriate base, e.g., potassium hydroxide, particularly membrane-produced potassium hydroxide. Other suitable bases include, e.g., KOH, KHCO3, K2CO3, and potassium alkoxides. An exemplary reaction mechanism using potassium hydroxide as a neutralizing agent is shown in reaction (7) below.

[0115]

[0116] In one embodiment, acesulfame-H can be neutralized and extracted directly from the purified organic extract phase using an aqueous solution of potassium base. Acesulfame potassium is then precipitated in the form of crystals where appropriate after evaporation of the solution and can also be recrystallized for purification.

[0117] In one embodiment, the method is not a small-scale batch method or a laboratory-scale method. For example, the method of the present invention for producing a refined acesulfame potassium composition can produce at least 50 grams of refined acesulfame potassium composition per batch, for example, at least 100 grams per batch, at least 500 grams per batch, at least 1 kilogram per batch, or at least 10 kilograms per batch. In terms of rate, the method of the present invention can produce at least 50 grams of refined acesulfame potassium composition per hour, for example, at least 100 grams per hour, at least 500 grams per hour, at least 1 kilogram per hour, or at least 10 kilograms per hour.

[0118] Figure 1 An exemplary acesulfame potassium process 100 is shown according to the methods described herein. The process 100 includes an ammonium sulfamate forming reactor 102 and an acetoacetamide forming reactor 104. Although Figure 1 Separate reactors for two intermediate formation reactions are shown, but other configurations, for example, a one-reactor process are also within the contemplation of the inventive process. Sulfamic acid is fed to the ammonium sulfamate formation reactor 102 via sulfamate feed line 106. Amine(s), preferably triethylamine, is fed to the ammonium sulfamate formation reactor 102 via amine feed line 108. In addition to sulfamate and amine(s), acetic acid is also fed to the ammonium sulfamate formation reactor 102 (via feed line 110). The resulting reaction mixture in the ammonium sulfamate formation reactor 102 is as discussed above. In the ammonium sulfamate formation reactor 102, sulfamate is reacted with amine (in the presence of acetic acid) to produce a crude ammonium sulfamate composition, which leaves the reactor 102 via line 112. Although not shown, a reaction solvent, for example, methylene chloride, may also be present in the ammonium sulfamate formation reactor 102.

[0119] The crude ammonium sulfamate composition in line 112 is directed to the acetoacetamide salt forming reactor 104. Diketene is fed to the acetoacetamide salt forming reactor 104 via feed line 114. In the acetoacetamide salt forming reactor 104, the ammonium sulfamate and diketene are reacted to produce a crude acetoacetamide salt composition, which exits the reactor 104 via line 118. Although not shown, methylene chloride may also be present in the acetoacetamide salt forming reactor 104.

[0120] The cyclizing agent (sulfur dioxide) and solvent (dichloromethane) are fed to vessel 119 via feed lines 121 and 123. Vessel 119 is preferably a vessel in which a cyclizing agent composition comprising these two components is formed. The cyclizing agent composition comprising both the cyclizing agent and the solvent leaves vessel 119 via line 125.

[0121] The crude acetoacetamide salt composition is directed to the cyclization reactor 120 via line 118. The cyclizing agent composition is also directed to the cyclization reactor 120 (via line 125). Line 125 is preferably made of such materials and in such a size and shape that it promotes the residence time discussed herein. In the cyclization reactor 120, the acetoacetamide salt in the crude acetoacetamide salt composition in line 118 is cyclized and the cyclic sulfur trioxide adduct stream exits via line 124.

[0122] The cyclic sulfur trioxide adduct is directed to a hydrolysis reactor 126 in line 124. Water is fed to the hydrolysis reactor 126 via a water feed 128. In the hydrolysis reactor 126, the cyclic sulfur trioxide adduct is hydrolyzed to produce a crude acesulfame-H composition, which leaves the hydrolysis reactor 126 via line 130 and is directed to a phase separation unit 132. The phase separation unit 132 separates the contents of line 130 into an organic phase 134 and an aqueous phase 136. The organic phase 134 includes the major amount of acesulfame-H in line 130 and a solvent, e.g., methylene chloride. The aqueous phase 136 leaves via line 137 and includes triethylammonium sulfate, and optionally sulfuric acid and a trace amount of acesulfame-H. The aqueous phase may be further purified to separate and / or recover acesulfame-H and / or triethylammonium sulfate. The recovered acesulfame-H may be combined with a combination (not shown) from acesulfame.

[0123] The organic phase 134 exits the phase separation unit 132 and is directed to an extraction column 138 (via line 140). Water is fed to the extraction column 138 via water feed 142. The water extracts residual sulfate from the contents of line 140, and the purified acesulfame-H composition exits the extraction column 138 via line 144. The extracted sulfate exits the extraction column 138 via line 145.

[0124] The purified acesulfame-H composition is directed to a neutralization unit 146 in line 144. Potassium hydroxide is also fed to the neutralization unit 146 (via line 148). The addition of potassium hydroxide to the neutralization unit 146 (via line 148) can be adjusted to achieve and / or maintain a desired pH level during neutralization, as discussed herein. The potassium hydroxide neutralizes the acesulfame-H in the purified acesulfame-H composition to produce a product comprising acesulfame potassium, methylene chloride, water, potassium hydroxide, and impurities (e.g., acetoacetamide-N-sulfonic acid or acetoacetamide), which exits the neutralization unit 146 via line 150. This product can be considered a crude acesulfame potassium composition.

[0125] The crude acesulfame potassium product stream can be directed in line 150 to a processing zone 156 to recover refined acesulfame potassium, shown exiting via stream 152. In addition to refined acesulfame potassium, methylene chloride and potassium hydroxide can also be separated from the crude acesulfame potassium product stream, as shown by stream 154. The contents of stream 154 can be recovered and / or recycled to the process. Processing zone 156 can include one or more of the processing operations described herein, for example, stripping, evaporation, crystallization, and filtration.

[0126] The product is directed to a phase separation unit 160 in line 150. Phase separation unit 160 separates the product in line 150 into an organic phase 162 and an aqueous phase 164. Aqueous phase 164 includes the major amount of acesulfame potassium in line 150 as well as some impurities. Organic phase 162 contains potassium hydroxide, methylene chloride, and water, and can be further processed to recover these components. Aqueous phase 164 (without any further processing) can be considered a crude acesulfame potassium composition. Aqueous phase 164 can optionally be processed to form a refined acesulfame potassium composition.

[0127] Aqueous phase 164 is directed to treatment unit 156 via line 166. In treatment unit 156, aqueous phase 164 is treated to obtain a refined acesulfame potassium composition (a product that can be sold), which is shown exiting via stream 152. In addition to the refined acesulfame potassium composition, dichloromethane and potassium hydroxide may also be separated. These components exit treatment unit 156 via line 154. The contents of stream 154 may be recovered and / or recycled to the process.

[0128] The present invention also relates to the following aspects:

[0129] Aspect 1: A method for producing a refined acesulfame potassium composition, the method comprising the following steps:

[0130] (a) forming a cyclic sulfur trioxide adduct;

[0131] (b) hydrolyzing the cyclic sulfur trioxide adduct to form an acesulfame-H composition comprising acesulfame-H;

[0132] (c) neutralizing the acesulfame-H in the acesulfame-H composition to form a crude acesulfame potassium composition comprising acesulfame potassium and less than 2,800 wppm of acetoacetamide-N-sulfonic acid, wherein the neutralizing step is performed at a pH at or below 11.0; and

[0133] (d) treating a crude acesulfame potassium composition to form a refined acesulfame potassium composition comprising acesulfame potassium and less than 37 wppm of acetoacetamide-N-sulfonic acid.

[0134] Aspect 2: The method according to aspect 1, wherein the neutralization step comprises:

[0135] Acesulfame-H is reacted with the neutralizer in the acesulfame-H / neutralizer reaction mixture to form an acesulfame potassium composition.

[0136] Aspect 3: The method according to any one of the preceding aspects, wherein the neutralizing agent comprises potassium hydroxide.

[0137] Aspect 4: The method according to any of the preceding aspects, wherein potassium hydroxide is produced via a membrane process and the acesulfame potassium composition is refined to have less than 10 wppm mercury.

[0138] Aspect 5: The method according to any one of the preceding aspects, wherein the acesulfame-H / neutralizer reaction mixture comprises 1 wt% to 95 wt% of the neutralizer and 1 wt% to 95 wt% of acesulfame-H, based on the total weight of the acesulfame-H / neutralizer reaction mixture.

[0139] Aspect 6: The method according to any one of the preceding aspects, wherein the neutralization step (c) comprises neutralizing acesulfame-H in the acesulfame-H composition to form a crude acesulfame potassium composition further comprising acetoacetamide.

[0140] Aspect 7: The method according to any one of the preceding aspects, wherein the crude acesulfame potassium composition comprises 500 wppm-2375 wppm of acetoacetamide-N-sulfonic acid and the refined acesulfame potassium composition comprises less than 25 wppm of acetoacetamide-N-sulfonic acid and further comprises less than 25 wppm of acetoacetamide.

[0141] Aspect 8: The method according to any one of the preceding aspects, wherein the neutralization step (c) is carried out at a pH of 9.0-11.0 and the crude acesulfame potassium composition contains 20 wppm-2500 wppm of acetoacetamide-N-sulfonic acid and the refined acesulfame potassium composition contains less than 25 wppm of acetoacetamide-N-sulfonic acid and less than 15 wppm of acetoacetamide.

[0142] Aspect 9: The method according to any one of the preceding aspects, wherein the neutralization step (c) is carried out at a pH of 8-10.3 and the crude acesulfame potassium composition contains 600 wppm-1200 wppm of acetoacetamide-N-sulfonic acid, and the refined acesulfame potassium composition contains less than 10 wppm of acetoacetamide-N-sulfonic acid and less than 10 wppm of acetoacetamide.

[0143] Aspect 10: The method according to any one of the preceding aspects, wherein the neutralization step (c) is carried out at a pH of 8-10.3 and the crude acesulfame potassium composition contains less than 2400 wppm of acetoacetamide-N-sulfonic acid, and the refined acesulfame potassium composition contains less than 10 wppm of acetoacetamide-N-sulfonic acid and less than 10 wppm of acetoacetamide.

[0144] Aspect 11: The method according to any one of the preceding aspects, wherein the refined acesulfame potassium composition comprises less than 37 wppm acetoacetamide.

[0145] Aspect 12: The method according to any one of the preceding aspects, wherein the neutralization step (c) is performed at a pH of 9.0-11.0.

[0146] Aspect 13: The method according to any one of the preceding aspects, wherein the neutralization step (c) is performed at a pH of 9.0-10.5.

[0147] Aspect 14: The method according to any one of the preceding aspects, wherein the neutralization step (c) is performed at a pH of 8.0-10.3.

[0148] Aspect 15: The method according to any one of the preceding aspects, wherein the treating step (d) is carried out at a temperature below 90°C.

[0149] Aspect 16: The method according to any of the preceding aspects, wherein the treating step (d) comprises an evaporation step with a residence time of less than 180 minutes.

[0150] Aspect 17: The method according to any of the preceding aspects, wherein the neutralization step is maintained at a pH at or below 11.0.

[0151] Aspect 18: A purified acesulfame potassium composition produced or capable of being produced, or capable of being obtained or obtained by the method according to any one of aspects 1-17.

[0152] Aspect 19: A method for producing a refined acesulfame potassium composition, the method comprising the following steps:

[0153] (a) reacting aminosulfonic acid with triethylamine to form an ammonium aminosulfonate;

[0154] (b) reacting an ammonium sulfamate with diketene to form an acetoacetamide salt;

[0155] (c) contacting methylene chloride with sulfur trioxide to form a cyclizing agent composition;

[0156] (d) reacting the acetoacetamide salt with sulfur trioxide in the cyclizing agent composition to form a cyclic sulfur trioxide adduct;

[0157] (e) hydrolyzing the cyclic sulfur trioxide adduct to form an acesulfame-H composition comprising acesulfame-H;

[0158] (f) neutralizing the acesulfame-H in the acesulfame-H to form a crude acesulfame potassium composition comprising acesulfame potassium and less than 2,800 wppm of acetoacetamide-N-sulfonic acid, wherein the neutralization step is performed at a pH at or below 11.0,

[0159] (g) treating a crude acesulfame potassium composition to form a refined acesulfame potassium composition, the refined acesulfame potassium composition comprising acesulfame potassium and less than 37 wppm of acetoacetamide-N-sulfonic acid,

[0160] Wherein steps (a), (b) and (c) may be performed in any order before performing step (d).

[0161] Aspect 20: The method according to aspect 19, wherein the refined acesulfame potassium composition further comprises less than 20 wppm of acetoacetamide.

[0162] Aspect 21: The method according to any one of the preceding aspects, wherein the neutralization step (f) is carried out at a pH of 9.0-11.0 and the crude acesulfame potassium composition contains 20 wppm-2500 wppm of acetoacetamide-N-sulfonic acid and the refined acesulfame potassium composition contains less than 25 wppm of acetoacetamide-N-sulfonic acid and less than 15 wppm of acetoacetamide.

[0163] Aspect 22: Acesulfame potassium composition comprising acesulfame potassium and less than 25 wppm of acetoacetamide-N-sulfonic acid and less than 25 wppm of acetoacetamide.

[0164] Aspect 23: The acesulfame potassium composition according to Aspect 22, further comprising 0.001 wppm to 5 wppm of organic impurities and / or 0.001 wppm to 5 wppm of at least one heavy metal.

[0165] Aspect 24: The acesulfame potassium composition according to any of the preceding aspects, wherein the at least one heavy metal is selected from mercury, lead, and mixtures thereof.

[0166] Aspect 25: The acesulfame potassium composition according to any of the preceding aspects, wherein mercury is present in an amount of 1 wppb to 20 wppm.

[0167] Aspect 26: The acesulfame potassium composition according to any of the preceding aspects, wherein lead is present in an amount of 1 wppb to 25 wppm.

[0168] Example

[0169] The following examples are included to demonstrate methods and compositions and are not intended to limit the scope of the present application.

[0170] Examples 1a-c and Comparative Example A

[0171] 100mmol of 99.5% pure aminosulfonic acid is suspended in 50mL dichloromethane in the flask with reflux. Under continuous stirring, 105mmol of trimethylamine is added within about 3 minutes. During this time, the temperature rises to about 42°C (boiling point of dichloromethane) due to the acid / base exothermic reaction. The first reaction mixture is stirred for another about 15 minutes until no solid deposit is seen in the flask. Then, 10mmol of acetic acid is added to the first reaction mixture and stirred for another about 15 minutes. At this time, within 7 minutes of adding acetic acid, 110mmol of diketene is added dropwise to form a second reaction mixture. After all diketenes are added to the second reaction mixture and a reaction time of about 15 minutes, the second reaction mixture is cooled. The second reaction mixture cooled by the gained comprises about 30% of acetoacetamide N-sulfonic acid triethylammonium salt. If necessary, the second reaction mixture cooled by the preparation of other batches.

[0172] In a separate vessel, a sulfur trioxide / methylene chloride composition comprising about 15 wt % sulfur trioxide and about 85 wt % methylene chloride was prepared by contacting the two components with each other.

[0173] A second flask (a 4-neck round bottom flask equipped with a mechanical stirrer, a thermometer and a feed container) is placed in a cooling bath containing a mixture of isopropanol and dry ice. Approximately 200 g of acetoacetamide-N-sulfonic acid triethylammonium salt solution and approximately 577 g of sulfur trioxide / methylene chloride composition are measured. Approximately 15 wt % of the total sulfur trioxide / methylene chloride composition (approximately 87 g) is initially fed to the reaction flask under continuous stirring by a mechanical stirrer. When the temperature of the flask contents reaches -35°C (due to the cooling bath), the remainder of the sulfur trioxide / methylene chloride composition and all of the acetoacetamide-N-sulfonic acid triethylammonium salt solution are fed to the second flask. Prior to the formation of cyclic sulfur trioxide adducts, for example, the time period for the solvent to contact the cyclizing agent prior to feeding the acetoacetamide-N-sulfonic acid triethylammonium salt solution to the second flask is less than 1 hour. The feed rate was controlled in such a way that the temperature of the contents of the second flask remained between -25°C and -35°C during the feed / cyclization reaction. After the reactants were fed, the reaction was allowed to proceed for an additional approximately one minute. The cooling bath was then removed.

[0174] After about one minute, the temperature of the flask contents reached about -22°C. At this point, hydrolysis was initiated by feeding deionized water to the flask. The water was fed over 10 minutes. The hydrolysis reaction was exothermic. Water was added slowly so as to maintain the temperature at -20°C to -5°C. After the water was added, the reaction mixture was allowed to reach room temperature.

[0175] For Examples 1a-c and Comparative Example A, the weight proportion of water added for the hydrolysis to acetoacetamide-N-sulfonic acid triethylammonium salt in dichloromethane solution was kept constant.

[0176] The hydrolyzate was phase separated via a separatory funnel. The heavier organic sweetener acid-methylene chloride phase (acesulfame-H composition) was separated and the remaining aqueous phase was discarded.

[0177] The acesulfame-H in the acesulfame-H composition was neutralized with a 10% potassium hydroxide solution. The neutralization was performed at 25°C ± 1°C. The potassium hydroxide addition was completed within 20 minutes. The neutralization was performed at various pH levels, as shown in Table 1.

[0178] After the neutralization step was completed, additional phase separation was performed using a separatory funnel to produce an aqueous phase containing acesulfame potassium (and some impurities) and an organic phase. The aqueous phase was considered the crude acesulfame potassium composition in Table 1. The dichloromethane in the remaining organic phase was discarded.

[0179] The crude acesulfame potassium samples of Examples 1a-c and Comparative Example A were tested for acetoacetamide-N-sulfonic acid content. The testing was performed using the HPLC equipment and techniques discussed herein. In particular, HPLC analysis was performed using an LC system HPLC unit from Shimadzu with a CBM-20 Shimadzu controller and equipped with an IonPac NS1 ((5 μm) 150×4 mm) analytical column and an IonPac NG1 guard column (35×4.0 mm). A Shimadzu SPD-M20A light emitting diode array detector was used for detection (at 270 nm and 280 nm wavelengths). The analysis was performed at a column temperature of 23° C. As the first eluent solution, an aqueous mixture of tetrabutylammonium hydrogen sulfate (3.4 g / L), acetonitrile (300 mL / L) and potassium hydroxide (0.89 g / L) was used; as the second eluent solution, an aqueous mixture of tetrabutylammonium hydrogen sulfate (3.4 g / L) and potassium hydroxide (0.89 g / L) was used. The calculations were performed using the LabSolution software from Shimadzu. Elution was performed in gradient mode according to the following second eluent flow profile:

[0180] 0-3 minutes: constant 80% (v / v)

[0181] 3-6 minutes: linearly decrease to 50% (v / v)

[0182] 6-15 minutes: Constant at 50% (v / v)

[0183] 15-18 minutes: linearly decrease to 0%

[0184] 18-22 minutes: Constant at 0%

[0185] 22-24 minutes: linear increase to 80% (v / v)

[0186] 24-35 minutes: constant at 80% (v / v).

[0187] The total flow rate of the eluent was approximately 1.2 mL / min. Data collection and calculations were performed using the LabSolution software from Shimadzu.

[0188] The results are shown in Table 1.

[0189] Table 1: Acetoacetamide-N-sulfonic acid content in crude acesulfame potassium composition

[0190]

[0191] As shown in Table 1, when the neutralization step was conducted at a pH at or below 11.0, the acetoacetamide-N-sulfonic acid content in the resulting crude acesulfame potassium composition was significantly lower than when a higher pH was used - at least 23% less (Comparative Example A vs. Example 1c 3066-2361 / 3066=23%).

[0192] Importantly, the reduction in the acetoacetamide-N-sulfonic acid content of the crude acesulfame potassium composition provides a concomitant reduction in acetoacetamide formation (e.g., via acetoacetamide-N-sulfonic acid degradation) in subsequent separation operations, which results in a reduction in the acetoacetamide content of the resulting purified acesulfame potassium composition.

[0193] Although the present invention has been described in detail, modifications within the spirit and scope of the present invention will be apparent to those skilled in the art. In view of the above discussion, the relevant knowledge in the art and the references discussed above in conjunction with the background technology and the specific embodiments, the disclosures of which are all incorporated herein by reference. In addition, it should be understood that aspects of the present invention and the various embodiments and parts of various features described above and / or in the appended claims may be combined or interchanged in whole or in part. In the above description of various embodiments, those embodiments with reference to another embodiment may be appropriately combined with other embodiments, as will be understood by those skilled in the art. In addition, it will be understood by those of ordinary skill in the art that the foregoing description is by way of example only, and is not intended to limit the present invention.

Claims

1. A method for producing a refined acesulfame potassium composition, the method comprising the following steps: (a) forming a cyclic sulfur trioxide adduct; (b) hydrolyzing the cyclic sulfur trioxide adduct to form an acesulfame-H composition comprising acesulfame-H and an organic solvent; (c) adding a neutralizing agent to the acesulfame-H composition formed in step b to neutralize the acesulfame-H in the acesulfame-H composition to form a crude acesulfame potassium composition, the crude acesulfame potassium composition comprising acesulfame potassium and acetoacetamide-N-sulfonic acid, wherein the neutralization step is performed at a pH of 8 to 11; and (d) treating the crude acesulfame potassium composition to form a refined acesulfame potassium composition, the refined acesulfame potassium composition comprising acesulfame potassium and less than 37 wppm of acetoacetamide-N-sulfonic acid, wherein the treating step (d) comprises a concentration operation and a separation operation, wherein the concentration operation is carried out at a temperature of less than 85 degrees Celsius, and wherein the treating step (d) comprises an evaporation step with a residence time of less than 120 minutes.

2. The method of claim 1, wherein the neutralization step (c) comprises: Acesulfame-H is reacted with the neutralizer in the acesulfame-H / neutralizer reaction mixture to form an acesulfame potassium composition.

3. The method of claim 2, wherein the neutralizing agent comprises potassium hydroxide.

4. The process of claim 3, wherein potassium hydroxide is produced via a membrane process and the refined acesulfame potassium composition comprises less than 10 wppm mercury.

5. The method of claim 2, wherein the acesulfame-H / neutralizer reaction mixture comprises 1 wt% to 95 wt% of the neutralizer and 1 wt% to 95 wt% of acesulfame-H, based on the total weight of the acesulfame-H / neutralizer reaction mixture.

6. The method of claim 1, wherein the neutralizing step (c) comprises neutralizing acesulfame-H in the acesulfame-H composition to form a crude acesulfame potassium composition further comprising acetoacetamide.

7. The process of claim 6, wherein the crude acesulfame potassium composition comprises 500 wppm to 2375 wppm of acetoacetamide-N-sulfonic acid and the refined acesulfame potassium composition comprises less than 25 wppm of acetoacetamide-N-sulfonic acid and further comprises less than 25 wppm of acetoacetamide.

8. The method of claim 6, wherein the neutralization step (c) is carried out at a pH of 9.0-11.0 and the crude acesulfame potassium composition comprises 20 wppm-2500 wppm of acetoacetamide-N-sulfonic acid and the refined acesulfame potassium composition comprises less than 25 wppm of acetoacetamide-N-sulfonic acid and less than 15 wppm of acetoacetamide.

9. The method of claim 6, wherein the neutralization step (c) is carried out at a pH of 8-10.3 and the crude acesulfame potassium composition comprises 600 wppm-1200 wppm of acetoacetamide-N-sulfonic acid, and the refined acesulfame potassium composition comprises less than 10 wppm of acetoacetamide-N-sulfonic acid and less than 10 wppm of acetoacetamide.

10. The process of claim 6, wherein the neutralization step (c) is carried out at a pH of 8-10.3 and the crude acesulfame potassium composition comprises less than 2400 wppm of acetoacetamide-N-sulfonic acid, and the refined acesulfame potassium composition comprises less than 10 wppm of acetoacetamide-N-sulfonic acid and less than 10 wppm of acetoacetamide.

11. The method of claim 6, wherein the refined acesulfame potassium composition comprises less than 37 wppm acetoacetamide.

12. The method of claim 1, wherein the neutralization step (c) is performed at a pH of 9.0-11.

0.

13. The method of claim 1, wherein the neutralization step (c) is performed at a pH of 9.0-10.

5.

14. The method of claim 1, wherein the neutralization step (c) is performed at a pH of 8.0-10.

3.

15. The method of claim 1, wherein the treating step (d) comprises an evaporation step having a residence time of less than 180 minutes.

16. The method of claim 1, wherein the neutralizing step is maintained at a pH at or below 11.

0.

17. A method for producing a refined acesulfame potassium composition, the method comprising the following steps: (a) reacting aminosulfonic acid with triethylamine to form an ammonium aminosulfonate; (b) reacting the ammonium sulfamate with diketene to form acetoacetamide; (c) contacting methylene chloride with sulfur trioxide to form a cyclizing agent composition; (d) reacting the acetoacetamide salt with sulfur trioxide in the cyclizing agent composition to form a cyclic sulfur trioxide adduct; (e) hydrolyzing the cyclic sulfur trioxide adduct to form an acesulfame-H composition comprising acesulfame-H and an organic solvent; (f) adding a neutralizing agent to the acesulfame-H composition formed in step e to neutralize the acesulfame-H in the acesulfame-H to form a crude acesulfame potassium composition, the crude acesulfame potassium composition comprising acesulfame potassium and acetoacetamide-N-sulfonic acid, wherein the neutralization step is performed at a pH of 8 to 11, (g) treating a crude acesulfame potassium composition to form a refined acesulfame potassium composition, the refined acesulfame potassium composition comprising acesulfame potassium and less than 37 wppm of acetoacetamide-N-sulfonic acid, Wherein steps (a), (b) and (c) may be performed in any order before performing step (d), wherein processing step (g) comprises a concentration operation and a separation operation, wherein the concentration operation is performed at a temperature below 85 degrees Celsius.

18. The method of claim 17, wherein the refined acesulfame potassium composition further comprises less than 20 wppm acetoacetamide.

19. The method of claim 18, wherein the neutralization step (f) is carried out at a pH of 9.0-11.0 and the crude acesulfame potassium composition comprises 20 wppm-2500 wppm of acetoacetamide-N-sulfonic acid and the refined acesulfame potassium composition comprises less than 25 wppm of acetoacetamide-N-sulfonic acid and less than 15 wppm of acetoacetamide.

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