Process for the preparation of an acesulfame with sulphuric acid processing

Abstract

The present invention generally 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 present invention also relates to the use of such a process for making diammonium sulphate. The present 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-sulphonic acid or a derivative thereof in the presence of an amine, thereby obtaining a first stream comprising the amine and sulphuric acid; b. Providing a second stream comprising ammonia; c. Providing a circuit; d. Introducing the second stream into the circuit at point A and the first stream into the circuit at point B to obtain a cycle stream cycling in the circuit; e. Removing a portion of the cycle stream at a point C to obtain a third stream;
wherein the circulation ratio is in the range from 3 to 30, the circulation ratio being the value of the mass flow rate of the cycle stream immediately preceding point A F.sub.c divided by the value of the mass flow rate of the first stream into the circuit at point B F.sub.1 according to the following formula:
circulation ratio=F.sub.c/F.sub.1.

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 salt thereof, the process comprising the following steps: a. Contacting SO.sub.3 and acetoacetamide-N-sulphonic acid or a salt thereof, in the presence of an amine, thereby obtaining a first stream comprising the amine and sulphuric acid; b. Providing a second stream comprising ammonia; c. Providing a circuit; d. Introducing the second stream into the circuit at point A and the first stream into the circuit at point B to obtain a cycle stream cycling in the circuit; e. Removing a portion of the cycle stream at a point C to obtain a third stream; wherein the circulation ratio is in the range from 3 to 30, the circulation ratio being the value of the mass flow rate of the cycle stream immediately preceding point A F.sub.c divided by the value of the mass flow rate of the first stream into the circuit at point B F.sub.1 according to the following formula:
circulation ratio=F.sub.c/F.sub.1.

2. The process according to claim 1, wherein the amine is triethyl amine.

3. The process according to claim 1, wherein the third stream is removed from the cycle stream at a point C and the points A, B & C are ordered in the direction of the flow of the cycle stream in the circuit.

4. The process according to claim 1, wherein the second stream does not comprise more than 50 wt. % H.sub.2O.

5. The process according to claim 1, wherein the second stream is a liquid.

6. The process according to claim 1, wherein the second stream is at a pressure in the range from 0.2 to 1.5 MPa.

7. The process according to claim 1, further comprising the following step: f. Separating the third stream to obtain a fourth stream comprising the amine and a fifth stream comprising diammonium sulphate; wherein the fourth stream comprises a higher wt. % of the amine than the first stream; wherein the fourth stream comprises a lower wt. % of diammonium sulphate than the first stream.

8. The process according to claim 7, wherein the fifth stream is contacted with H.sub.2O in a step g.sub.1.

9. The process according to claim 8, wherein least part of the H.sub.2O is present in step g.sub.1 in a gaseous state.

10. The process according to claim 7, wherein the mass ratio of the fourth stream to the fifth stream is in the range from 30:70 to 1:99.

11. The process according to claim 7, wherein the content of H.sub.2O in the fifth stream is reduced in a step g.sub.2.

12. The process according to claim 11, wherein the step g.sub.2 is a solidification.

13. The process according to claim 7, wherein the fourth stream is separated into a sixth stream and a seventh stream in a step h; wherein the seventh stream comprises more H.sub.2O than the sixth stream; wherein the sixth stream comprises more of the amine than the seventh stream.

14. The process according to claim 13, wherein the step h is a distillation.

15. The process according to claim 1, wherein the cycle stream is heated or cooled.

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) The figures and descriptions focus on the features of the process relating to the invention and are not intended to be a comprehensive description of already established processes. The skilled person is aware of the technical details required to implement parts of the process which fall outside the focus of the invention, such as standard processes for distillation, phase separation and drying.

(3) FIG. 1 is a schematic showing material flows in a process according to the invention.

(4) FIG. 2 is a schematic process flow showing the steps of the invention

(5) FIG. 3 is the graph showing the influence of water content in the production of diammonium sulphate on energy efficiency.

(6) FIG. 4 is a graph showing the influence of circulation ratio on the conversion yield of sulphuric acid to diammonium sulphate as well as on pump parameters.

DESCRIPTION OF THE FIGURES

(7) FIG. 1 is a schematic showing material flows in a process according to the invention. A first stream 102 arising from a preparation process for acesulfame, comprising triethyl amine, sulphuric acid and water along with other trace constituents and a second stream 101 of liquid ammonia are introduced into a circuit to obtain a cycle stream, the first stream at point B and the second stream at point A in the circuit. The cycle stream is cooled or heated in a heat exchanger 103 and passed to a phase separator 104 at point C in the circuit. In the phase separator 104, a portion of the cycle stream called the third stream is separated into a liquid fifth stream comprising diammonium sulphate and H.sub.2O and a gaseous fourth stream comprising triethyl amine and H.sub.2O. Part of the fifth stream is circulated into the cycle stream, in this case 8 to 15 times the flow of the first stream. The portion of the fifth stream leaving the circuit proceeds to be contacted with steam 105 to obtain aqueous diammonium sulphate solution which proceeds to further processing 106 and a steam portion which joins with the fourth stream. The further processing of the fifth stream comprises a solidification to obtain solid diammonium sulphate. The fourth stream along with the added steam component is distilled 107 into triethyl amine 108, which can be reused in the preparation of acesulfame, and a water fraction 109 which can be circulated back into the first stream 102.

(8) FIG. 2 is a schematic process flow showing the steps of the invention. In a step a. 201 SO.sub.3 and acetoacetamide-N-sulphonic acid are contacted to form an acesulfame. A first stream comprising H.sub.2O, triethyl amine and sulphuric acid results from this step. In a step b. 202 a second stream of liquid ammonia is provided. In a step c. 203 a circuit is provided. In a step d. 204, the first and second streams are introduced into the circuit to obtain a cycle stream. In a step e. 205 a third stream is removed from the cycle. The third stream may be separated into a volatile fourth stream comprising triethyl amine and H.sub.2O and a liquid fifth stream comprising H.sub.2O and diammonium sulphate in a separation step f. The fifth stream may subsequently be contacted with H.sub.2O in the form of steam in step g.sub.1 206 and the resultant diammonium sulphate subsequently solidified in step g.sub.2 207. The fourth stream may be distilled in a step h. 208 to separate into a triethyl amine phase and a H.sub.2O phase. Purified triethyl-amine leaves the distillation at the column bottom.

(9) FIG. 3 further elucidates the influence of water content in the diammonium sulphate (DASA) solution (stream passing to solidification 106). The power requirements for drying are influenced by the water content. The power consumption was measured over the course of an hour

(10) FIG. 4 shows the effect of varying the circulation ratio on the proportional conversion of sulphuric acid into diammonium sulphate as well as the Reynolds number and energy consumption for the pump. The parameters were measured over the course of an hour.

EXAMPLES

(11) 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.

(12) General Procedure

(13) A process was set up according to FIG. 1. The contacting step a. in which the acesulfame was created was performed as follows. The acetoacetamide-N-sulphonic acid supply was the triethylammonium salt of Acetoacetamide-N-sulphonic 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. A hydrolysis bed was provided with a flow of H.sub.2O which was adjusted such that the ratio of sulphuric acid:H.sub.2O by weight in the hydrolysis products was maintained in the range from 3:1 to 1:1. The sulphuric acid and triethyl amine products of the contacting and hydrolysis reaction were extracted using excess dichloromethane resulting in the first stream comprising 43 to 55 wt. % sulphuric acid and 10 to 12 wt. % triethyl amine in aqua. Pure liquefied ammonia or ammonia solutions were employed as the second stream. 10 times the input of the first stream was circulated to the cycle stream.

Examples 1 to 7

(14) In Examples 1 to 4 the quantity of H.sub.2O was varied in the hydrolysis step yielding the concentrations in the first stream shown in table 1. The concentration of ammonia in the second stream in these examples was 100 wt. % (liquid ammonia). In examples 5 to 7 the first stream was the same as in example 1. Here the ammonia concentration in the second stream was varied, firstly taking the maximum soluble content in water at 20° C. of 36 wt. % (example 5), secondly taking a commercially employed value of 25 wt. % (example 6) and thirdly taking the value 21 wt. % (example 7).

(15) TABLE-US-00001 TABLE 1 Content of second stream Contents of first stream [wt. %] [wt. %] Example H.sub.2SO.sub.4 H.sub.2O TEA AcOH*TEA NH.sub.3 1 55 30 12 3 100 2 51 35 11 3 100 3 47 40 11 2 100 4 43 45 10 2 100 5 55 30 12 3 32 6 55 30 12 3 25 7 55 30 12 3 21

(16) Results for the power requirement for spray drying of the diammonium sulphate are shown in table 2 and presented in FIG. 3. The power consumption was measured over the course of an hour.

(17) TABLE-US-00002 TABLE 2 Energy Efficiency H.sub.2O content in DASA production Spray drying Example [wt. %] kW/kg DASA 1 30 0.226 2 35 0.284 3 40 0.363 4 45 0.439 5 50 0.542 6 55 0.655 7 60 0.82

Example 8

(18) The procedure was repeated according to example 1, except that the circulation ratio was varied as per table 3. The proportion of sulphuric acid converted, the Reynolds number and the pump power demand are also displayed in table 3. Results are displayed in FIG. 4. The parameters were measured over the course of an hour.

(19) TABLE-US-00003 TABLE 3 Conversion of Pump power sulphuric acid Reynolds demand Example Circulation ratio [%] number (Normalised) 8a 3 82 930 1 8b 4 89 1276 1.72 8c 5 94 1508 2.47 8d 6 96.5 1856 3.22 8e 7 98 2204 4.17 8f 8 99 2436 4.89 8g 9 99.5 2784 11.34 8h 10 99.7 3132 14.03 8i 11 99.7 3364 17.52 8j 12 99.7 3712 22.75 8k 13 99.7 3944 27.44 8l 14 99.7 4292 34.11 8m 15 99.7 4640 41.94 8n 16 99.7 4872 48.8 8o 17 99.7 5220 57.94 8p 18 99.7 5568 69.2 8q 19 99.7 5800 78.56 8r 20 99.7 6148 91.63 8s 21 99.7 6496 108.47 8t 22 99.7 6728 123.31 8u 23 99.7 7076 144.3 8v 24 99.7 7424 165.89 8w 25 99.7 7656 188.75 8x 26 99.7 8004 220.61 8y 27 99.7 8325 253.63 8z 28 99.7 8584 287.63 8aa 29 99.7 8923 318.7 8bb 30 99.7 9280 352.78

REFERENCE LIST

(20) 101 Second stream 102 First stream 103 Cooler 104 Phase separator 105 Steam 106 Crystallisation 107 Distillation 108 Triethyl amine phase 109 H.sub.2O phase 201 Step a. 202 Step b. 203 Step c. 204 Step d. 205 Step e 206 Step g.sub.1 207 Step g.sub.2 208 Step h