PROCESS FOR OPERATING A PLANT FOR PREPARING AN ALKANESULFONIC ACID
20190077748 ยท 2019-03-14
Assignee
Inventors
- Benjamin Fonfe (Frankfurt, DE)
- Chiu Kee Cheung (Alzenau, DE)
- Ali Hartwig (Gruendau, DE)
- Nadine Duerr (Mobile, AL, US)
Cpc classification
C07C303/16
CHEMISTRY; METALLURGY
International classification
Abstract
The present invention relates to a process for operating a plant for preparing an alkanesulfonic acid, wherein said alkanesulfonic acid is prepared by oxidation of an alkylmercaptan, dialkydisulfide and/or dialkylpolysulfide and the one or more alkyl radicals of the alkylmercaptan, dialkydisulfide and/or dialkylpolysulfide are identical with the alkyl radical of the alkylsulfonic acid to be prepared, characterized in that the oxidation is performed in the presence of an at least stoichiometric amount of an oxoacid of nitrogen, e.g. nitric acid, relative to the amount of said alkylmercaptan, dialkyldisulfide and/or dialkylpolysulfide during the start-up phase of the plant of the plant, wherein the start up phase comprises the steps adding an oxoacid of nitrogen to the reactor, adding sulfur-containing reactant progressively so that it is converted to alkanesulfonic acid, filling up the compile volume of the reactor by adding progressively sulfur-containing reactant and if needed oxoacid of nitrogen to make sure that it is in excess, once the reactor is full, transitioning out of the start-up phase by adding an oxygen containing fluid, and during the running phase, keeping the reaction volume full by balancing the volume of product withdrawn with the volume of sulfur-containing reactant added.
Claims
1. A process for operating a plant for preparing an alkanesulfonic acid, wherein said alkanesulfonic acid is prepared by oxidation of an alkylmercaptan, dialkydisulfide and/or dialkylpolysulfide, such that the oxidation is performed in the presence of an at least stoichiometric amount of an oxoacid of nitrogen relative to the amount of said alkylmercaptan, dialkyldisulfide and/or dialkylpolysulfide during the start-up phase of the plant, the process comprising: i) providing an oxoacid of nitrogen in a reactor, ii) feeding at least one of an alkylmercaptan containing stream, a dialkydisulfide containing stream, and a dialkylpolysulfide containing stream into the oxoacid of nitrogen in the reactor to give an alkanesulfonic acid containing product mixture, and iii) repeating step ii) until the available inner volume of the reactor is filled completely with the alkanesulfonic acid containing product mixture obtained in step ii), iv) feeding additional oxoacid of nitrogen into the reactor, when the amount of oxoacid of nitrogen provided in step i) is not enough to fill the available inner volume of the reactor with the product mixture obtained in step ii), v) feeding an oxygen containing fluid stream into the reactor, when the available inner volume of the reactor is completely filled with the product mixture obtained in the step ii) and/or in the step iii), vi) removing at least part of the alkanesulfonic acid containing product mixture from the reactor, and vii) feeding at least one of an alkylmercaptan containing stream, a dialkydisulfide containing stream, and a containing stream into the reactor to yield a reaction mixture, wherein said alkylmercaptan, dialkyldisulfide and/or dialkylpolysulfide is identical with the alkylmercaptan, dialkyldisulfide and/or dialkylpolysulfide of any of the preceding steps, wherein the volume of the alkylmercaptan, dialkyldisulfide and/or dialkylpolysulfide containing stream, fed into the reactor in step vii), equals the volume of the product mixture removed from the reactor in step vi).
2. The process according to claim 1, wherein the start-up phase of the plant is performed in a batch mode or in a semi-continuous mode.
3. The process according to claim 1, wherein the oxoacid of nitrogen is nitric acid and the process further comprises: i) providing at least the amount of nitric acid according to the formula:
4. The process according to claim 3, further comprising: iii) feeding water, further nitric acid, or a mixture thereof, into the reactor until the stirrer of the reactor is immersed in the alkanesulfonic acid containing product mixture.
5. The process according to claim 3, further comprising: v) feeding at least one of an alkylmercaptan containing stream, a dialkydisulfide containing stream, and a containing stream and an oxygen containing fluid stream into the reactor until the available inner volume of the reactor is filled completely with the alkanesulfonic acid containing product mixture.
6. The process according to claim 1, wherein the steps v) to vii) are performed in a continuous mode or in an essentially continuous mode.
7. The process according to claim 1, wherein the oxygen containing fluid stream is fed into the reactor near to or under the stirrer of the reactor.
8. The process according to claim 1, wherein alkanesulfonic acid is prepared from at least one of an alkylmercaptan with a C.sub.1 to C.sub.12 alkyl radical, dialkyldisulfide with a C.sub.1 to C.sub.12 alkyl radical, and dialkylpolysulfide with a C.sub.1 to C.sub.12 alkyl radical.
Description
EXAMPLES
Comparative Example 1
[0138] A first test was performed to see the corrosive behavior of a typical reaction mixture of the preparation of an alkanesulfonic acid by oxidizing a dialkyldisulfide with oxygen on the materials of chemical reactors. For this purpose coupons of four different austenitic steels were placed in a bath of a mixture comprising 96.5 wt.-% methanesulfonic acid (MSA), 2 wt.-% dimethyldisulfide (DMDS), 1 wt.-% S-methyl methanethiosulfonate (MMTS) and 0.5 wt.-% water (H.sub.2O), which is representative for a reaction mixture obtained in the oxidizing of a dialkyldisulfide with oxygen.
[0139] Plates of the following austenitic stainless steels were used in the test:
TABLE-US-00001 TABLE 1 Overview of the tested austenitic stainless steels. Material number according ASTM (USA) to EN 10 088-2 DIN/EN number number 1.4404 X6 CrNiMoTi17-12-2 316 L 1.4439 X 2 CrNiMoN 17-13-5 S 31726 1.4539 X 1 NiCrMoCu 25-20-5 N08904 1.4571 X 6 CrNiMoTi 17-12-2 316 Ti
[0140] The thickness of the different coupons was measured before and after the tests. For determining the corrosive effect of dimethyldisulfide and S-methyl methanethiosulfonate on the austenitic stainless steels, the coupons were placed into a mixture comprising 96.5 wt.-% methanesulfonic acid (MSA), 2 wt-% dimethyldisulfide (DMDS), 1 wt.-% S-methyl methanethiosulfonate (MMTS) and 0.5 wt.-% water (H.sub.2O) at a constant temperature of 70 C. for a period of 300 hours. The difference in the thickness of the coupons was determined and was converted to a loss of thickness in mm per year (mm/year). The results are summarized, in the table below. None of the chosen austenitic stainless steels was resistant to the mixture of the preparation of methanesulfonic acid. However, there were even strong corrosion effects visible on the steels according to the material numbers 1.4571 and 1.4404.
TABLE-US-00002 TABLE 2 Results for the tested austenitic stainless steels Steels tested 1.4571 1.4404 1.4539 1.4439 Thickness 10 mm/year 10 mm/year up to up to loss 10 mm/year 10 mm/year
Comparative Example 2
[0141] A second test was performed in order to find out whether the presence of dimethyldisulfide (DMDS), S-methyl methanethiosulfonate (MMTS) or any other components, such as acetic acid, in the reaction mixture leads to the observed, corrosion phenomena. For this purpose four different solutions based on methanesulfonic acid were provided: a first solution which consisted of pure methanesulfonic acid (MSA 100%), a second solution with methanesulfonic acid containing traces of acetic acid (MSA+AA), a third solution with methanesulfonic acid containing 1 wt.-% of S-methyl methanethiosulfonate (MSA+MMTS) and a fourth solution with methanesulfonic acid containing 2 wt.-% of dimethyldisulfide (MSA+DMDS).
[0142] The thickness of the different test coupons of the four different material numbers of comparative example 1 was measured before and after the tests. For determining the corrosive effect of dimethyldisulfide, S-methyl methanethiosulfonate or acetic acid on the austenitic stainless steels, the coupons were placed into the aforementioned solutions at a constant temperature of 70 C. for a period of 300 hours. The difference in the thickness of the four test coupons was determined and then converted to a loss of thickness in mm per year (mm/year). The results are summarized in table 3 below.
TABLE-US-00003 TABLE 3 Results for the tested austenitic stainless steels Steels tested 1.4571 1.4404 1.4408 1.4462 MSA (100%) <0.01 mm/year MSA + AA <10 mm/year MSA + AA + MMTS 10 mm/year MSA + AA + DMDS 10 mm/year
[0143] The results show that pure methanesulfonic acid does not lead to considerable corrosion phenomena. However, the additional presence of acetic acid, even if only in traces, already leads to significantly increased corrosion phenomena. The additional presence of the S-methyl methanethiosulfonate or dimethyldisulfide in methanesulfonic acid even leads to thickness loss of the tested steels of approximately 50 mm per year. Hence, the additional presence of any of these sulfur species leads to an increase in corrosion by a factor of more than 1000, compared to the corrosion in pure methanesulfonic acid.
Example 1
[0144] In order to find out the necessary amount of nitric acid for passivating steels, test coupons of the material numbers 1.4408, 1.4462, 1.4539 and 1.4571 were placed into different solutions based on methanesulfonic acid with traces of acetic acid: a first solution containing methanesulfonic acid with traces of acetic acid (MSA+AA), a second solution containing methanesulfonic acid with traces of acetic acid and in addition 0.05 wt.-% of nitric acid (MSA+AA+0.05% HNO.sub.3), a third solution containing methanesulfonic acid with traces of acetic acid and in addition 0.1 wt.-% of nitric acid (MSA+AA+0.1% HNO.sub.3), and a fourth solution containing methanesulfonic acid with traces of acetic acid and in addition 0.5 wt.-% of nitric acid (MSA+AA+0.5% HNO.sub.3). The temperature of the solutions was in each case 70 C. and the test coupons were left in the solutions for a duration of 300 hours. The difference in the thickness of the four test coupons before and after the tests was determined according to the procedure of comparative examples 1 and 2 and was converted to a loss of thickness in mm per year (mm/year). The results are summarized in table 4 below.
TABLE-US-00004 TABLE 4 Corrosion rates of steels contested with nitric acid containing methanesulfonic acid. Steels tested 1.4408 1.4462 1.4539 1.4571 MSA + AA <10 mm/year MSA + pitting corrosion AA + 0.05% HNO.sub.3 MSA + <0.01 mm/year <0.01 mm/year <0.01 mm/year crevice AA + 0.1% corro- HNO.sub.3 sion MSA + <0.01 mm/year AA + 0.5% HNO.sub.3
[0145] The results show that the presence of 0.5 wt.-% of nitric acid p.assivates the surfaces of all tested steels' against corrosion by methanesulfonic acid with traces of acetic acid.
Example 2
[0146] Further tests were carried out to tired out whether the Presence of 0.5 wt.-% of nitric acid is also effective to passivate steels against corrosion by methanesulfonic acid, which in addition to acetic acid also contains 1 wt.-% of S-methyl methanethiosulfonate and 2 wt.-% of dimethyldisulfide. Test coupons of the material numbers 1.4408, 1.4462, 1.4539 and 1.45711 were placed into the solutions, which had a temperature of 70 C., and left therein for a duration of 300 hours. The difference in the thickness of the four test coupons before and after the tests was determined according to the procedure of comparative examples 1 and 2 and then converted to a loss of thickness in mm per year (mm/year). The results are summarized in table 5 below.
TABLE-US-00005 TABLE 5 Corrosion rates of steels contacted with methanesulfonic acid containing sulfur compounds and nitric acid. Steels tested 1.4408 1.4462 1.4539 1.4571 MSA + AA + MMTS 10 mm/year MSA + AA + DMDS 10 mm/year MSA + AA + MMTS + <0.01 mm/year 0.5% HNO.sub.3 MSA + AA + DMDS + <0.01 mm/year 0.5% HNO.sub.3
[0147] It was found that the presence of 0.5% of nitric acid is also effective to passivate the surface of test coupons of the tested steels against corrosion by methanesulfonic acid containing traces of acetic acid and S-methyl methanethiosulfonate or dimethyldisulfide.
Example 3
[0148] In situ tests were carried out in order to show the passivating effect of nitric acid on the material of a chemical reactor in the industrial preparation of methanesulfonic acid by oxidation of dimethyldisulfide. For this purpose, a continuously stirred tank reactor (CSTR) was used that effected a conversion of dimethyldisulfide of at least 98%, so that the product stream exiting the reactor contained ca. 1 wt.-% of dimethyldisulfide and ca. 0.5 wt.-% S-methyl methanethiosulfonate. The product stream exiting the reactor was directed to a material test unit, which essentially is a jacketed pressure vessel with a residence time of approximately one hour. Using the jacket it was possible to regulate the temperature within the material test unit from 40 C. to 70 C. This means that the reactor for producing methanesulfonic acid could be operated first at a relatively safe temperature of 40 C. and independently the temperature in the material test unit could be increased to 70 C. Two test coupons of each of the steels according to the material numbers 1.4408 and 1.4507 were attached inside the jacketed pressure vessel using screws made of polytetrafluoroethylene.
[0149] The tests were carried out for a complete duration of more than two months. Each test ran for a duration of approximately three days: The operation mode in the reactor and the temperature in the material test unit are summarized in table 6. After each test run the material test unit was opened and the steel test coupons were inspected for signs of corrosion and their weight was noted to quantify any weight losses.
TABLE-US-00006 TABLE 6 In situ material testing conditions Cumulated Temperature Test test in the mate- Run duration duration Operation mode in the rial test unit no. [h] [h] reactor [ C.] 1 145.0 500 g/h DMDS, 40 C., 40 150 g/h HNO.sub.3 (32 wt.-%) 2 68.6 214 500 g/h DMDS, 40 C., 40 150 g/h HNO.sub.3 (32 wt.-%) 3 65.5 279 500 g/h DMDS, 40 C., 40 150 g/h HNO.sub.3 (32 wt.-%) 4 71.0 350 500 g/h DMDS, 40 C., 50 150 g/h HNO.sub.3 (32 wt.-%) 5 69.5 420 500 g/h DMDS, 40 C., 55 150 g/h HNO.sub.3 (32 wt.-%) 6 72 492 500 g/h DMDS, 40 C., 60 150 g/h HNO.sub.3 (32 wt.-%) 7 68 559 500 g/h DMDS, 40 C., 70 150 g/h HNO.sub.3 (32 wt.-%) 8 92 651 500 g/h DMDS, 50 C., 70 150 g/h HNO.sub.3 (32 wt.-%) 9 69 719 500 g/h DMDS, 50 C., 70 150 g/h HNO.sub.3 (16 wt.-%) 10 91 810 500 g/h DMDS, 55 C., 70 150 g/h HNO.sub.3 (32 wt.-%) 11 164 974 500 g/h DMDS, 60 C., 70 150 g/h HNO.sub.3 (32 wt.-%) 12 90 1064 760 g/h DMDS, 60 C., 70 225 g/h HNO.sub.3 (32 wt.-%) 13 56 1120 760 g/h DMDS, 50 C., 70 195 g/h HNO.sub.3(16 wt.-%) 14 42 1162 760 g/h DMDS, 60 C., 70 170 g/h HNO.sub.3 (8 wt.-%)
[0150] In all test runs there were no signs of corrosion whatsoever on any of the test coupons and there S were no weight losses recorded, even when lower concentrations of nitric acid were dosed, e.g. the amount of nitric acid dosed in test run no. 14 equals a nitric acid concentration of approximately 1 wt.-% in the product stream.