Process for the preparation of an acesulfame in a spray reactor having a specific velocity of flow

Abstract

In general, the invention relates to a process for the preparation of acesulfame or a derivative thereof. More specifically, the invention relates to a process, to a product obtainable by the process and the use of a specified velocity of flow for improving yield in the preparation of acesulfame or a derivative thereof. The invention relates to a process for the preparation of a product, the product being 6-methyl-3,4-dihydro1,2,3-oxathiazin-4-one 2,2-dioxide or a derivative thereof, the process comprising the following steps: a. Contacting SO.sub.3 and acetoacetamide-N-sulfonic acid or a derivative thereof in a reactor with a reactor pressure to obtain the product; b. The product exiting the reactor to a region outside the reactor through an aperture at a velocity of flow higher than 0.9 m/s, the region outside the reactor having an external pressure which is lower than the reactor pressure.

Claims

1. A process for the preparation of a product, the product being 6-methyl-3,4-dihydro1,2,3-oxathiazin-4-one 2,2-dioxide or a derivative thereof, the process comprising the following steps: a. contacting SO.sub.3 and acetoacetamide-N-sulfonic acid or a derivative thereof in a reactor with a reactor pressure to obtain the product; b. the product exiting the reactor to a region outside the reactor through an aperture at a velocity of flow in the range from 3 to 17 m/s, the region outside the reactor having an external pressure which is lower than the reactor pressure.

2. The process according to claim 1, wherein the velocity of flow is in the range from 5 to 15 m/s.

3. The process according to claim 1, wherein the reactor has a reactor temperature in the range from −70 to 175° C.

4. The process according to claim 1, wherein the reactor pressure is in the range from 0.2 to 2 MPa.

5. The process according to claim 1, wherein the external pressure is in the range from 0.01 to 0.5 MPa.

6. The process according to claim 1, wherein the difference between the reactor pressure and the external pressure is in the range from 0.1 to 1.9 MPa.

7. The process according to claim 1, wherein the aperture has a cross sectional area in the range from 10 mm.sup.2 to 500 mm.sup.2.

8. The process according to claim 1, wherein the product exits the reactor in step b. as a spray.

9. The process according to claim 1, comprising the following step: c. the product is contacted with H.sub.2O.

10. The process according to claim 9, wherein step c. is started within 60 seconds of step b.

11. The process according to claim 1, wherein the product is cooled by evaporation of a solvent.

12. The process according to claim 1, wherein the molar ratio in step a. of the SO.sub.3 to the acetoacetamide-N-sulfonic acid or derivative thereof is in the range from 1:1 to 20:1.

13. The process according to claim 1, wherein step b. is performed within 10 minutes of step a.

14. The process according to claim 1, wherein the contacting in step a. is performed in the presence of a reaction solvent, wherein the reaction solvent comprises dichloromethane.

15. The process according to claim 1, wherein the SO.sub.3 for the contacting step a. is provided in a first solvent, wherein the first solvent comprises dichloromethane.

16. The process according to claim 1, wherein the acetoacetamide-N-sulfonic acid or a derivative thereof for the contacting step a. is provided in a second solvent, wherein the second solvent comprises dichloromethane.

17. The process according to claim 1, wherein the SO.sub.3 for the contacting step a. is provided in a first solvent and the acetoacetamide-N-sulfonic acid or a derivative thereof for the contacting step a. is provided in a second solvent and the first solvent and the second solvent are the same.

Description

SUMMARY OF THE FIGURES

(1) The invention is now further elucidated with reference to the figures. The figures and figure descriptions are exemplary and are not to be considered as limiting the scope of the invention.

(2) FIG. 1 is a flow diagram showing a process according to the invention.

(3) FIG. 2 is a schematic diagram showing a reactor and hydrolysis bed.

(4) FIG. 3 shows a schematic diagram of a tubular reactor.

(5) FIG. 4 shows a plot of yield against velocity of flow.

(6) FIG. 5 shows a plot of yield against reaction time.

DESCRIPTION OF THE FIGURES

(7) FIG. 1 is a flow diagram showing a process according to the invention. In step a. 101 an acetoacetamide-N-sulfonic acid or derivative thereof is contacted with SO.sub.3 in a reactor. In this case the triethyl ammonium salt of acetoacetamide-N-sulfonic acid dissolved in dichloromethane is contacted with SO.sub.3, also dissolved in dichloromethane. In this case the temperature in the reactor is 105° C. and the pressure in the reactor is 0.7 MPa. In step b. 102, the product sprays out of the reactor through an aperture having a cross sectional area of 110 mm to outside of the reactor where the pressure is atmospheric. The velocity of flow through the aperture is 10 m/s. On exiting the reactor and reducing in pressure, some of the dichloromethane solvent evaporates and the temperature of the product reduces to 40° C. In this case, an optional hydrolysis step c. 103 is performed. The product which has sprayed out of the reactor falls onto a hydrolysis bed which is provided with a flow of H.sub.2O, thereby hydrolysing and liberating sulphuric acid. In this case several optional further steps 104 are performed to separate the dichloromethane, acesulfame product, H.sub.2O and sulphuric acid.

(8) FIG. 2 is a schematic diagram showing a reactor 203 and hydrolysis bed 205. An acetoacetamide-N-sulfonic acid derivative supply 201, in this case the triethylammonium salt of acetoacetamide-N-sulfonic acid dissolved in dichloromethane, and an SO.sub.3 supply 202, in this case SO.sub.3 dissolved in dichloromethane, are provided to the reactor 203 and react there to an acesulfame product, in this case an adduct of acesulfame with SO.sub.3. The product exits from the reactor 203 from the apertures 204 as a spray and descends onto a hydrolysis bed 205 having an H.sub.2O supply 206 where it is hydrolysed. The hydrolysis products 207 are removed from the hydrolysis bed and optionally passed to further processes, for example for separating solvents, products and by-products.

(9) FIG. 3 shows a schematic diagram of a tubular reactor. An acetoacetamide-N-sulfonic acid supply 201 and an SO.sub.3 supply 202 enter the reactor 203, each via a tube. The reactor 203 is itself a cylindrical tube. The supplies 201 & 202 in this case are mixed by a static mixer 301. The static mixer 301 has the same cross-sectional diameter as the reactor 203. The product 302 leaves the reactor 203 via a circular aperture 204. In this case, the diameter of the aperture 204 is less than the cross-sectional diameter of the reactor 203. The cross-sectional diameter of the reactor 203 is determined at the static mixer 301. On exiting the reactor 203 via the aperture 204, the product 302 turns into a spray due to evaporation of solvent.

(10) FIG. 4 shows a plot of yield against velocity of flow for the process of the invention. Yield is expressed as a proportion of the theoretical maximum yield.

(11) FIG. 5 shows a plot of yield against reaction time for the process of the invention. Yield is expressed as a proportion of the theoretical maximum yield.

REFERENCE LIST

(12) 101 Contacting Step a. 102 Exiting Step b. 103 Optional hydrolysis step c. 104 Optional further steps 201 acetoacetamide-N-sulfonic acid supply 202 SO.sub.3 supply 203 Reactor 204 Aperture 205 Hydrolysis bed 206 Water supply 207 Hydrolysis products 301 Mixer 302 Product

EXAMPLES

(13) The invention is now further elucidated with the aid of examples. These examples are for illustrative purposes and are not to be considered as limiting the scope of the invention.

Examples 1 to 6

(14) A device was provided according to FIG. 2. The acetoacetamide-N-sulfonic acid supply was the triethylammonium salt of Acetoacetamide-N-sulfonic acid dissolved in dichloromethane (DKA) at a concentration of 1.5 molar. The SO.sub.3 supply was SO.sub.3 dissolved in dichloromethane (DCM/SO.sub.3) at a concentration of 5 molar. The two supplies were provided to the reactor with volume flow ratio DKA:DCM/SO.sub.3 of 1:1.2 and the total flow rate was dynamically adjusted such that the product ejected from the reactors with a velocity of flow as given for the particular example in table 1. The supply of H.sub.2O to the hydrolysis bed was adjusted such that the ratio of sulphuric acid:H.sub.2O by weight in the hydrolysis products was 3:1.

(15) TABLE-US-00001 TABLE 1 Yield of acesulfame depending on velocity of flow and reaction time Velocity of Consumption flow through Yield (% of Reaction compared Example aperture theoretical Time with optimum # [m/s] maximum) [s] run as reference 1 0.5 55% 0.72 +55% 2 0.9 58% 0.43 +47% 3 1 60% 0.37 +42% 4 5 78% 0.07  +9% 5 9 85% 0.05 REF 6 15 82% 0.025  +4% 7 30 74% 0.013 +15%

(16) The consumption parameter is calculated as the total cash cost of raw materials, energy consumption, the cost of working up of solvents and auxiliary materials, waste generation with its respective incineration cost as well as the treatment of effluents and off-gas. The consumption parameter is determined by producing a fixed mass of acesulfame K product. The consumption parameter thus represents both the economical and the ecological efficiency of the process.

(17) FIG. 4 shows the yield of the reaction as a proportion of the theoretical maximum yield plotted graphically against the velocity of flow. FIG. 5 shows the yield of the reaction as a proportion of the theoretical maximum yield plotted graphically against the reaction time.