EP4151774A1 - Process for the production of methane sulfonic acid - Google Patents
Process for the production of methane sulfonic acid Download PDFInfo
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- EP4151774A1 EP4151774A1 EP21198115.4A EP21198115A EP4151774A1 EP 4151774 A1 EP4151774 A1 EP 4151774A1 EP 21198115 A EP21198115 A EP 21198115A EP 4151774 A1 EP4151774 A1 EP 4151774A1
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- msa
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- AFVFQIVMOAPDHO-UHFFFAOYSA-N Methanesulfonic acid Chemical compound CS(O)(=O)=O AFVFQIVMOAPDHO-UHFFFAOYSA-N 0.000 title claims abstract description 130
- 229940098779 methanesulfonic acid Drugs 0.000 title claims abstract description 65
- 238000000034 method Methods 0.000 title claims abstract description 30
- 230000008569 process Effects 0.000 title claims abstract description 25
- 238000004519 manufacturing process Methods 0.000 title claims abstract description 12
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 claims abstract description 56
- 238000005868 electrolysis reaction Methods 0.000 claims abstract description 6
- 230000035484 reaction time Effects 0.000 claims description 9
- HIFJUMGIHIZEPX-UHFFFAOYSA-N sulfuric acid;sulfur trioxide Chemical compound O=S(=O)=O.OS(O)(=O)=O HIFJUMGIHIZEPX-UHFFFAOYSA-N 0.000 claims description 8
- 229910003460 diamond Inorganic materials 0.000 claims description 4
- 239000010432 diamond Substances 0.000 claims description 4
- 238000000926 separation method Methods 0.000 claims description 4
- 239000011541 reaction mixture Substances 0.000 claims description 3
- ZOXJGFHDIHLPTG-UHFFFAOYSA-N Boron Chemical compound [B] ZOXJGFHDIHLPTG-UHFFFAOYSA-N 0.000 claims description 2
- 229910052796 boron Inorganic materials 0.000 claims description 2
- 238000004821 distillation Methods 0.000 claims description 2
- 239000007772 electrode material Substances 0.000 claims 1
- AKEJUJNQAAGONA-UHFFFAOYSA-N sulfur trioxide Chemical compound O=S(=O)=O AKEJUJNQAAGONA-UHFFFAOYSA-N 0.000 abstract description 24
- JZMJDSHXVKJFKW-UHFFFAOYSA-N methyl sulfate Chemical compound COS(O)(=O)=O JZMJDSHXVKJFKW-UHFFFAOYSA-N 0.000 description 41
- 238000006243 chemical reaction Methods 0.000 description 40
- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Substances [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 description 14
- 238000005481 NMR spectroscopy Methods 0.000 description 11
- 230000015572 biosynthetic process Effects 0.000 description 10
- 239000000047 product Substances 0.000 description 10
- 238000002474 experimental method Methods 0.000 description 7
- 238000003756 stirring Methods 0.000 description 7
- 239000000126 substance Substances 0.000 description 7
- 239000003999 initiator Substances 0.000 description 6
- -1 alkane sulfonic acids Chemical class 0.000 description 5
- 230000008901 benefit Effects 0.000 description 5
- 239000006227 byproduct Substances 0.000 description 5
- 239000011521 glass Substances 0.000 description 5
- 238000006277 sulfonation reaction Methods 0.000 description 5
- 238000007306 functionalization reaction Methods 0.000 description 4
- 230000037361 pathway Effects 0.000 description 4
- 229910052697 platinum Inorganic materials 0.000 description 4
- 238000011002 quantification Methods 0.000 description 4
- 239000004809 Teflon Substances 0.000 description 3
- 229920006362 Teflon® Polymers 0.000 description 3
- 238000000354 decomposition reaction Methods 0.000 description 3
- 230000007423 decrease Effects 0.000 description 3
- 230000003247 decreasing effect Effects 0.000 description 3
- PCHJSUWPFVWCPO-UHFFFAOYSA-N gold Chemical compound [Au] PCHJSUWPFVWCPO-UHFFFAOYSA-N 0.000 description 3
- 229910052737 gold Inorganic materials 0.000 description 3
- 239000010931 gold Substances 0.000 description 3
- GKOZUEZYRPOHIO-UHFFFAOYSA-N iridium atom Chemical compound [Ir] GKOZUEZYRPOHIO-UHFFFAOYSA-N 0.000 description 3
- 239000000463 material Substances 0.000 description 3
- 229910052751 metal Inorganic materials 0.000 description 3
- 239000002184 metal Substances 0.000 description 3
- 230000001590 oxidative effect Effects 0.000 description 3
- 238000007086 side reaction Methods 0.000 description 3
- 239000010935 stainless steel Substances 0.000 description 3
- 229910001220 stainless steel Inorganic materials 0.000 description 3
- 238000005160 1H NMR spectroscopy Methods 0.000 description 2
- IAZDPXIOMUYVGZ-WFGJKAKNSA-N Dimethyl sulfoxide Chemical compound [2H]C([2H])([2H])S(=O)C([2H])([2H])[2H] IAZDPXIOMUYVGZ-WFGJKAKNSA-N 0.000 description 2
- 229910000831 Steel Inorganic materials 0.000 description 2
- 150000001335 aliphatic alkanes Chemical class 0.000 description 2
- 239000000956 alloy Substances 0.000 description 2
- 229910045601 alloy Inorganic materials 0.000 description 2
- 239000010405 anode material Substances 0.000 description 2
- 238000004140 cleaning Methods 0.000 description 2
- 230000008878 coupling Effects 0.000 description 2
- 238000010168 coupling process Methods 0.000 description 2
- 238000005859 coupling reaction Methods 0.000 description 2
- 238000013461 design Methods 0.000 description 2
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- 239000007789 gas Substances 0.000 description 2
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- 238000007254 oxidation reaction Methods 0.000 description 2
- 238000011160 research Methods 0.000 description 2
- 150000003839 salts Chemical class 0.000 description 2
- DZXBHDRHRFLQCJ-UHFFFAOYSA-M sodium;methyl sulfate Chemical compound [Na+].COS([O-])(=O)=O DZXBHDRHRFLQCJ-UHFFFAOYSA-M 0.000 description 2
- 239000010959 steel Substances 0.000 description 2
- 238000003786 synthesis reaction Methods 0.000 description 2
- LSNNMFCWUKXFEE-UHFFFAOYSA-M Bisulfite Chemical compound OS([O-])=O LSNNMFCWUKXFEE-UHFFFAOYSA-M 0.000 description 1
- OTMSDBZUPAUEDD-UHFFFAOYSA-N Ethane Chemical compound CC OTMSDBZUPAUEDD-UHFFFAOYSA-N 0.000 description 1
- 229910002567 K2S2O8 Inorganic materials 0.000 description 1
- ZLMJMSJWJFRBEC-UHFFFAOYSA-N Potassium Chemical compound [K] ZLMJMSJWJFRBEC-UHFFFAOYSA-N 0.000 description 1
- 239000002253 acid Substances 0.000 description 1
- 230000002378 acidificating effect Effects 0.000 description 1
- 230000004913 activation Effects 0.000 description 1
- 239000000654 additive Substances 0.000 description 1
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000003197 catalytic effect Effects 0.000 description 1
- 238000006555 catalytic reaction Methods 0.000 description 1
- 238000004440 column chromatography Methods 0.000 description 1
- 238000005260 corrosion Methods 0.000 description 1
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- 239000003792 electrolyte Substances 0.000 description 1
- 238000009713 electroplating Methods 0.000 description 1
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- 229910052760 oxygen Inorganic materials 0.000 description 1
- 239000001301 oxygen Substances 0.000 description 1
- 239000012071 phase Substances 0.000 description 1
- 229910052700 potassium Inorganic materials 0.000 description 1
- 239000011591 potassium Substances 0.000 description 1
- 238000002360 preparation method Methods 0.000 description 1
- 230000001737 promoting effect Effects 0.000 description 1
- 230000009257 reactivity Effects 0.000 description 1
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- 239000003566 sealing material Substances 0.000 description 1
- 230000000087 stabilizing effect Effects 0.000 description 1
- QAOWNCQODCNURD-UHFFFAOYSA-N sulfuric acid Substances OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 description 1
- 230000002110 toxicologic effect Effects 0.000 description 1
- 231100000027 toxicology Toxicity 0.000 description 1
- 230000007306 turnover Effects 0.000 description 1
Images
Classifications
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- C—CHEMISTRY; METALLURGY
- C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
- C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
- C25B3/00—Electrolytic production of organic compounds
- C25B3/01—Products
- C25B3/07—Oxygen containing compounds
-
- C—CHEMISTRY; METALLURGY
- C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
- C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
- C25B11/00—Electrodes; Manufacture thereof not otherwise provided for
- C25B11/04—Electrodes; Manufacture thereof not otherwise provided for characterised by the material
- C25B11/042—Electrodes formed of a single material
- C25B11/043—Carbon, e.g. diamond or graphene
-
- C—CHEMISTRY; METALLURGY
- C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
- C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
- C25B3/00—Electrolytic production of organic compounds
- C25B3/20—Processes
- C25B3/23—Oxidation
-
- C—CHEMISTRY; METALLURGY
- C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
- C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
- C25B3/00—Electrolytic production of organic compounds
- C25B3/20—Processes
- C25B3/29—Coupling reactions
Definitions
- the present invention relates to a process for the production of methane sulfonic acid from methane and sulfur trioxide in oleum.
- MSA Due to its unique properties, MSA is already used in some processes and demand is expected to increase further in the near future.
- the numerous advantages of MSA are: strongly acidic without being oxidizing, low vapor pressure and odorless, low toxicological risk, high solubility of its salts, high chemical stability and additionally it is biodegradable. All these characteristics make MSA attractive for use in e.g. the electronics industry for electroplating, for cleaning processes, for metal recycling, or in ionic liquids for a number of other processes.
- methane derivatives are used and then converted in multi-step redox reactions. This is not only unfavorable due to the number of reaction steps but also because side products are generated.
- a more attractive pathway is the direct sulfonation of methane, which is known for more than twenty years.
- the sulfonation usually takes place in oleum and is initiated by a metal peroxo- or peroxosulfate species.
- Methane sulfonic acid in contrast to methyl bisulfate (MBS), is considered a high value-added product and a green acid (for example, non-oxidant, low vapor pressure, bio-degradable, and so on) with uses in the pharma, electronic and cleaning industry.
- Basickes et al. ( Basickes, Hogan, Sen, J. Am . Chem. Soc. 1996, 11, 13111- 13112 ) describe the radical-initiated functionalization of methane and ethane in fuming sulfuric acid. Temperatures of 90°C and above are necessary and the yield of MSA is low.
- Mukhopadhyay and Bell report the direct sulfonation of methane at low pressure to methanesulfonic acid in the presence of potassium peroxydisphosphate as the initiator.
- a temperature of 95°C is chosen and the conversion rate of SO 3 is below 30%.
- WO 2004/041399 A2 and US 7,119,226 B2 both suggest a radical pathway and chain reaction for the production of methane sulfonic acid.
- radical chain reactions usually result in undesirable side products, which even manifest themselves as disturbing inhibitors in the production of alkane sulfonic acids, which may lead to termination of the actual reaction for preparing the alkane sulfonic acid and further to impurities, formation of side products and poor yields based on sulfur trioxide and methane.
- WO 2018/146153 describes a method for the production of alkane sulfonic acids, especially methane sulfonic acid, from alkane, especially methane, in which a carbocation is assumingly formed as intermediate.
- alkane sulfonic acids especially methane sulfonic acid
- the problem is solved by an electrochemical process for the production of methane sulfonic acid (MSA) from methane and sulfur trioxide, wherein methane and fuming sulfuric acid are electrolyzed with at least one electrode as anode, preferably at least one BDD electrode or a resistant electrode made from another anode material such as FTO or Pt/lr, ITO, ATO, lead, stainless steel, gold, and alloys thereof, in a pressurized reactor under a methane pressure in the range of at least 30 bar and at most 200 bar in a temperature range of 50°C to 120°C, preferably for a reaction time range which is adjusted depending on the current density and is preferably more than 2 hours, and the MSA is separated from obtained reaction mixture, for instance by distillation or other suitable separation methods such as column chromatography, fractional freezing, ion chromatography, membrane separation.
- MSA methane sulfonic acid
- the current density at the anode is usually kept between 0.5 mA/cm 2 to 20 mA/cm 2 during current flow and can be varied in the progress of the reaction or even paused for a determined amount of time during the reaction so that times of current flow and current-less times may be changed in intervalls.
- the pressure in the pressurized reactor is preferably kept in the range of 50 to 120 bar.
- the reaction can be carried out at temperatures, where unselective and uncontrolled radical chain reactions do not take place as observed in the prior art where high temperatures are required.
- the inventive process can, for example, efficiently be carried out already at about 50°C or slightly higher.
- substances promoting the decomposition of any initiators to radicals or stabilizing said radicals, as used in the prior art is not required in the inventive process as such initiators are not used in the inventive process.
- no such substances are added in the invention.
- Such substances include metal salts ⁇ e.g., Pt, Hg, Rh). They show detrimental side effects of triggering side reactions, which can be avoided by the present invention.
- the temperature in the pressurized reactor is preferably kept in a temperature range of 50°C to 100°C, and the reaction time in the pressurized reactor is usually kept between 3 and 24 hours, depending on the strength of the current density.
- the reaction mixture in the pressurized reaction vessel is preferably agitated, advantageously with a high-speed stirrer in order to safeguard an intimate contact between the anode, the fuming sulfuric acid and the methane.
- the stirring speed should be in the range of 600 rpm to 1800 rpm.
- any electrode fulfilling these properties such as FTO or Pt/lr, ITO, ATO, lead, stainless steel, gold, and alloys thereof, depending on the actual conditions might also be used
- the electrolyte is fuming sulfuric acid having a concentration of 20 to 30 wt.%. SO 3 .
- concentrations of concentrated sulfuric acid with SO 3 in a concentration up to 45 wt.%, or even higher up to 60 wt.% are also possible.
- MSA concentration increases over time at all the current densities applied in shorter reaction times up to three hours. At reaction times longer than 3 hours, however, the current density will influence the yield significantly. At higher current density, the product as well as intermediate species can be decomposed faster which will lead to a decreased concentration compared to lower current densities. As the current density can also be adapted over the time this is actually an advantage as it gives room to find and tune an optimum setting between reaction kinetics and product or intermediate stability.
- the reaction can also take place if electrolysis and pressurization of the reactor are done in separate steps. After one hour of electrolysis of Oleum the reactor can be pressurized with methane immediately or after stirring without current for a time between 0 and 60 min in between. With increasing pause-time as intermediate stirring the concentration of MSA decreases. This shows that an active species is formed during electrolysis which decomposes slowly.
- the reactor was heated to 70 °C under stirring at 1200 rpm where a pressure of 90 bar was reached, then a current density of 3.125 mA/cm 2 was kept for 18000 seconds. Afterwards the autoclave was placed in an ice bath and cooled down to 25 °C before the pressure was released. The liquid sample was then analyzed by 1 H-NMR using sodium methyl sulfate as an internal standard for quantification. The concentration of MSA was 1.5 M, which is a yield of 24% based on SO 3 . Per every electron passed, 4.7 molecules of MSA were generated. The concentration of by-product methyl bisulfate was 1.4 mM, resulting in a selectivity towards MSA of 99.9%.
- the reactor was heated to 70 °C under stirring at 1200 rpm where a pressure of 90 bar was reached, then a current density of 1.25 mA/cm 2 was kept for 16 hours. Afterwards the autoclave was placed in an ice bath and cooled down to 25 °C before the pressure was released. The liquid sample was then analyzed by 1 H-NMR using sodium methyl sulfate as an internal standard for quantification. The concentration of MSA was 1.9 M, which is a yield of 32% based on SO 3 . Per every electron passed, 4.9 molecules of MSA were generated. The concentration of by-product methyl bisulfate was 55 mM, resulting in a selectivity towards MSA of more than 97%.
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- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Engineering & Computer Science (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Electrochemistry (AREA)
- Materials Engineering (AREA)
- Metallurgy (AREA)
- Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
- Electrolytic Production Of Non-Metals, Compounds, Apparatuses Therefor (AREA)
Abstract
The present invention relates to a process for the electrosynthetic production of methane sulfonic acid from methane and sulfur trioxide in oleum by electrolysis.
Description
- The present invention relates to a process for the production of methane sulfonic acid from methane and sulfur trioxide in oleum.
- Selective methane functionalization is still one of the top challenges of chemical research due to its low reactivity compared to its oxidation products. However, being abundant and cheap it could be a great feedstock for a number of useful products that can either serve as fuels or be used in chemical industry.
- In order to avoid the standard functionalization route via syngas formation various concepts including oxy-functionalization or coupling are under extensive investigation. Most of the very innovative developments, however, can still not meet the demands for an industrial application.
- The two most recently developed processes that are used by industry are the oxidative methane coupling as developed at Linde and Siluria (
US10047020B2 WO 2018/146153 ). - Due to its unique properties, MSA is already used in some processes and demand is expected to increase further in the near future. The numerous advantages of MSA are: strongly acidic without being oxidizing, low vapor pressure and odorless, low toxicological risk, high solubility of its salts, high chemical stability and additionally it is biodegradable. All these characteristics make MSA attractive for use in e.g. the electronics industry for electroplating, for cleaning processes, for metal recycling, or in ionic liquids for a number of other processes.
- For most of the production pathways described on the patent field, methane derivatives are used and then converted in multi-step redox reactions. This is not only unfavorable due to the number of reaction steps but also because side products are generated.
- A more attractive pathway is the direct sulfonation of methane, which is known for more than twenty years. The sulfonation usually takes place in oleum and is initiated by a metal peroxo- or peroxosulfate species.
- Early work on methane sulfonation led to the report of several radical initiators and additives for the activation of CH4 to methane sulfonic acid (MSA) in fuming sulfuric acid. However, the reactions lack high yield and good selectivity. Additionally, the reaction mechanism is still not yet entirely understood. Obvious problems arise in order to scale up these processes such as additional catalytic routes for SO2 conversion, excessively large reactors and extremely high temperatures. Methane sulfonic acid (MSA), in contrast to methyl bisulfate (MBS), is considered a high value-added product and a green acid (for example, non-oxidant, low vapor pressure, bio-degradable, and so on) with uses in the pharma, electronic and cleaning industry.
- Basickes et al. (Basickes, Hogan, Sen, J. Am . Chem. Soc. 1996, 11, 13111- 13112) describe the radical-initiated functionalization of methane and ethane in fuming sulfuric acid. Temperatures of 90°C and above are necessary and the yield of MSA is low.
- Mukhopadhyay and Bell (Organic Process Research & Development 2003, 7, 161-163) report the direct sulfonation of methane at low pressure to methanesulfonic acid in the presence of potassium peroxydisphosphate as the initiator. In order to activate the initiator, a temperature of 95°C is chosen and the conversion rate of SO3 is below 30%.
- Lobree and Bell (Ind. Eng. Chem . Res. 2001, 40, 736-742) also studied the K2S2O8-initiated sulfonation of methane to methanesulfonic acid. A radical mechanism is described and high temperature as well as low concentrations of initiator are required in order to achieve modest conversion rates of SO3.
-
US 2,493,038 describes the preparation of methane sulfonic acid from SO3 and methane.US 2005/0070614 describes further methods for preparing methane sulfonic acid, and its application. The methods known in the prior art are in part complicated, cost-intensive, and lead to undesirable products because of the harsh conditions. -
WO 2004/041399 A2 andUS 7,119,226 B2 both suggest a radical pathway and chain reaction for the production of methane sulfonic acid. In general, radical chain reactions usually result in undesirable side products, which even manifest themselves as disturbing inhibitors in the production of alkane sulfonic acids, which may lead to termination of the actual reaction for preparing the alkane sulfonic acid and further to impurities, formation of side products and poor yields based on sulfur trioxide and methane. -
WO 2018/146153 describes a method for the production of alkane sulfonic acids, especially methane sulfonic acid, from alkane, especially methane, in which a carbocation is assumingly formed as intermediate. However, said process is quite complicated and the reaction conditions and yields need further optimization. - It is thus the object of the present invention to provide an industrial process for the electrosynthetic production of methane sulfonic acid under improved conditions compared to thermochemical pathways.
- In a first embodiment the problem is solved by an electrochemical process for the production of methane sulfonic acid (MSA) from methane and sulfur trioxide, wherein methane and fuming sulfuric acid are electrolyzed with at least one electrode as anode, preferably at least one BDD electrode or a resistant electrode made from another anode material such as FTO or Pt/lr, ITO, ATO, lead, stainless steel, gold, and alloys thereof, in a pressurized reactor under a methane pressure in the range of at least 30 bar and at most 200 bar in a temperature range of 50°C to 120°C, preferably for a reaction time range which is adjusted depending on the current density and is preferably more than 2 hours, and the MSA is separated from obtained reaction mixture, for instance by distillation or other suitable separation methods such as column chromatography, fractional freezing, ion chromatography, membrane separation.
- In the inventive process, the current density at the anode is usually kept between 0.5 mA/cm2 to 20 mA/cm2 during current flow and can be varied in the progress of the reaction or even paused for a determined amount of time during the reaction so that times of current flow and current-less times may be changed in intervalls.
- The pressure in the pressurized reactor is preferably kept in the range of 50 to 120 bar.
- Furthermore, the reaction can be carried out at temperatures, where unselective and uncontrolled radical chain reactions do not take place as observed in the prior art where high temperatures are required. The inventive process can, for example, efficiently be carried out already at about 50°C or slightly higher. The addition of substances promoting the decomposition of any initiators to radicals or stabilizing said radicals, as used in the prior art, is not required in the inventive process as such initiators are not used in the inventive process. Particularly, no such substances are added in the invention. Such substances include metal salts {e.g., Pt, Hg, Rh). They show detrimental side effects of triggering side reactions, which can be avoided by the present invention.
- Thus, the temperature in the pressurized reactor is preferably kept in a temperature range of 50°C to 100°C, and the reaction time in the pressurized reactor is usually kept between 3 and 24 hours, depending on the strength of the current density.
- The reaction mixture in the pressurized reaction vessel is preferably agitated, advantageously with a high-speed stirrer in order to safeguard an intimate contact between the anode, the fuming sulfuric acid and the methane. Depending on the size and form of the stirrer and the design of the reactor, the stirring speed should be in the range of 600 rpm to 1800 rpm.
- The above reaction condition of pressure and temperature influence the reaction results to some extent, but the kind of electrode and the applied current density have higher impact. Keeping the current density at a moderate strength, the yield of MSA can be increased whereas too high current density will first lead to an increase, but then to a decrease over the time. Thus, the strength of the current density has to be carefully adjusted to the electrolyzing time in order to obtain maximum yields. The use of a BDD-electrode is found to be of major advantage for the process. The inventors have found that the properties of the BDD electrode are of particular advantage:
- High selectivity towards MSA on the BDD-electrode
- BDD offers high corrosion stability
- BDD resist deactivation over a long period
- Chemically inert material prevents catalysis of unwanted side reactions
- As an alternative electrode, any electrode fulfilling these properties, such as FTO or Pt/lr, ITO, ATO, lead, stainless steel, gold, and alloys thereof, depending on the actual conditions might also be used
- The electrolyte is fuming sulfuric acid having a concentration of 20 to 30 wt.%. SO3. However, other concentrations of concentrated sulfuric acid with SO3 in a concentration up to 45 wt.%, or even higher up to 60 wt.% are also possible.
- The present invention is further illustrated by the following Figures and Experimental Part. In the Figures, it is shown in:
- Figure 1:
- The dependency of the process on the current density for the formation of MSA
- Figure 2:
- The dependency of the concentration of MSA on the formation time in combination with the current density
- Figure 3:
- The dependency of the process on the methane pressure for the formation of MSA
- Figure 4:
- The dependency of the process on the temperature for the formation of MSA
- Figure 5:
- The separation of electrolysis step and methane pressurization
- Figure 6:
- The selectivity of a BDD electrode vs a Pt/lr electrode for the formation of MBS vs. MSA
- As it can be seen in
Figure 1 , Very low current current densities already lead to high product concentration after only 3 hours reaction time. There is an optimum range for the applied current density. If current density is too low the reaction will be slowed down significantly. If current density is too high the product or active intermediate species will decompose. This is evident in the figure from the decrease in electron "turnover" with increasing current density. The decomposition reactions can for instance include total oxidation of methane or the oxygen evolution reaction. The number of MSA molecules generated per passed electron is in general higher at low current densities. This means that at the applied conditions a lower current density leads to the same or only slightly lower MSA yield than a higher current density however with a highly increased faradaic yield. Therefore, in this case lower current densities are favorable, as any higher current density would just lead to lost charge. - As shown in
Figure 2 , MSA concentration increases over time at all the current densities applied in shorter reaction times up to three hours. At reaction times longer than 3 hours, however, the current density will influence the yield significantly. At higher current density, the product as well as intermediate species can be decomposed faster which will lead to a decreased concentration compared to lower current densities. As the current density can also be adapted over the time this is actually an advantage as it gives room to find and tune an optimum setting between reaction kinetics and product or intermediate stability. - From
Figure 3 , it becomes evident that a high methane pressure is beneficial for high product concentration whereas lower pressure leads to a low concentration of MSA. In order to avoid a slow reaction rate due to a decreased methane partial pressure it would be of advantage to keep a high pressure during the whole reaction time, which could be realized in a continuously operating process of the invented method. - In
Figure 4 , the temperature dependence of product concentration is shown. Similar to current density it was found that an optimum temperature range exists for this reaction. If too low, the reaction will proceed slowly and if too high the concentration is decreased due to decomposition reactions or possibly undetected side reactions other than MBS formation. - As shown in
Figure 5 , the reaction can also take place if electrolysis and pressurization of the reactor are done in separate steps. After one hour of electrolysis of Oleum the reactor can be pressurized with methane immediately or after stirring without current for a time between 0 and 60 min in between. With increasing pause-time as intermediate stirring the concentration of MSA decreases. This shows that an active species is formed during electrolysis which decomposes slowly. - The comparison of BDD with Pt/lr as anode material is shown in
Figure 6 . Although this is only a 30 min reaction it becomes evident that the selectivity towards MSA is higher using BDD. This does not only account for the selectivity with respect to SO3 consumption but also to Coulomb selectivity. However, the presented method also works on Pt/lr. -
- BDD anodes, DIACHEM® Electrode Typ 52, from CONDIAS, which is an electrode with a boron doped diamond (BDD) active layer.
- Counter electrode wire, platinum/iridium - Pt90/lr10, from Evochem
- Pt/lr anodes from Goodfellow (Pt/lr - 90/10 Foil)
-
- NMR analysis of the liquid phase with Bruker AV-300. Capillary DMSO-d6 for reference.
- Electrochemical measurements with Gamry Interface 1010E potentiostat
- The autoclave was designed and built in-house (see
Fig. 1 below). It is equipped with a pressure gauge (JUMO dTrans p30), and thermocouple (type K; protected by a Teflon hose). The autoclave material on the outside was stainless steel (1.4571) The H-type-cell design for electrochemical experiments was realized by a Teflon or glas inlet. The half cells were separated by a glass frit. The autoclave was heated via a heating jacket, controlled by a previously optimized PID controller. Sealing materials consisted of gold or Teflon. - Every experiment was carried out in the electro-autoclave described above in a two electrode arrangement, i.e. working electrode and counter electrode. In a usual experiment both half-cells were filled with 3 ml each of oleum (20-30%), then the autoclave was closed and pressurized with methane at room temperature. After placing it in the heating block, electrodes were connected to the potentiostat and the autoclave was heated under stirring to the desired temperature. Once the temperature was reached and stabilized, the respective electrochemical experiment was started. After the pre-set reaction time the electrodes were disconnected from the potentiostat and the autoclave was placed in an ice water bath to cool down under stirring. Once room temperature was reached the gas phase was released. Then the autoclave was opened and stirred with 750 rpm for 5 min to remove residual gas from the liquid phase.
- For quantification of MBS and MSA two NMR tubes were measured; one with the reaction solution (tube 1) and the other one with a mixture of a weighted amount of MBS and 1 ml of reaction solution (tube 2). The ratio R of MBS to MSA after reaction was determined from the first NMR tube. In
equation 1 the definition of R is shown:CMBS concentration of MBS after reaction I 1,MSA integral of MSA signal from NMR tube 1 CMSA concentration of MSA after reaction I 2,MBS,reaction contribution of MBS from reaction to integral of MBS signal from NMR tube 2 I 1,MBS integral of MBS signal from NMR tube 1 I 2,MSA integral of MSA signal from NMR tube 2 - R was then used to calculate the contribution of MBS from the reaction to the NMR integral of MBS in the second tube, I 2,MBS,reaction , as this integral consists of the already present MBS from the reaction and the added MBS. After subtracting I 2,MBS,reaction from the actual MBS integral from
tube 2, I 2,MBS , the contribution of the added MBS to the integral, I 2,MBS,added , is obtained (eq. 2). Since this amount is known, it is used to calculate the MSA concentration after reaction, cMSA , (eq. 3).I 2,MBS,added Share of added MBS to integral of MBS signal from NMR tube 2 I 2,MBS Integral of MBS signal from NMR tube 2 C MBS,added concentration of MBS added to tube 2 - Then, knowing the actual MSA concentration, MBS concentration from reaction, cMBS , can be simply calculated from the first NMR tube using eq. 1.
-
- In a 60 ml high pressure steel autoclave with an H-type cell glass inlet for electrochemical experiments where the two compartments were separated by a glass frit, 3 ml of fuming sulfuric acid (20-30%) were added to each cell compartment. The autoclave cap, where a boron-doped diamond anode and a platinum/iridium wire as a counter electrode were attached, was then carefully placed on the autoclave in a way that the electrodes were placed in the two compartments of the H-cell. After closing, the reactor was pressurized with 73 bar methane pressure at room temperature. The reactor was heated to 70 °C under stirring at 1200 rpm where a pressure of 90 bar was reached, then a current density of 3.125 mA/cm2 was kept for 18000 seconds. Afterwards the autoclave was placed in an ice bath and cooled down to 25 °C before the pressure was released. The liquid sample was then analyzed by 1H-NMR using sodium methyl sulfate as an internal standard for quantification. The concentration of MSA was 1.5 M, which is a yield of 24% based on SO3. Per every electron passed, 4.7 molecules of MSA were generated. The concentration of by-product methyl bisulfate was 1.4 mM, resulting in a selectivity towards MSA of 99.9%.
- In a 60 ml high pressure steel autoclave with an H-type cell glass inlet for electrochemical experiments where the two compartments were separated by a glass fritt, 3 ml of fuming sulfuric acid (20-30%) were added to each cell compartment. The autoclave cap, where a boron-doped diamond anode and a platinum/iridium wire as a counter electrode were attached, was then carefully placed on the autoclave in a way that the electrodes were placed in the two compartments of the H-cell. After closing, the reactor was pressurized with 73 bar methane pressure at room temperature. The reactor was heated to 70 °C under stirring at 1200 rpm where a pressure of 90 bar was reached, then a current density of 1.25 mA/cm2 was kept for 16 hours. Afterwards the autoclave was placed in an ice bath and cooled down to 25 °C before the pressure was released. The liquid sample was then analyzed by 1H-NMR using sodium methyl sulfate as an internal standard for quantification. The concentration of MSA was 1.9 M, which is a yield of 32% based on SO3. Per every electron passed, 4.9 molecules of MSA were generated. The concentration of by-product methyl bisulfate was 55 mM, resulting in a selectivity towards MSA of more than 97%.
Claims (5)
- Process for the electrosynthetic production of methane sulfonic acid (MSA) wherein methane and fuming sulfuric acid are electrolyzed with at least one electrode as anode that can be boron doped diamond or any other suitable electrode material in a pressurized reactor under a methane pressure in the range of at least 30 bar and at most 200 bar in a temperature range of 50°C to 120°C and a current density in a range of 0.5 mA/cm2 to 20 mA/cm2, preferably for a reaction time which is adjusted depending on the current density and is preferably more than 2 hours, and the MSA is separated from obtained reaction mixture by distillation or any other suitable separation method.
- Process according to claim 1, wherein the pressure in the pressurized reactor is kept in the range of 50 to 120 bar.
- Process according to claim 1 or 2, wherein the temperature in the pressurized reactor is kept in a temperature range of 50°C to 100°C.
- Process according to any one of claims 1, 2 or 3, wherein the reaction time in the pressurized reactor is kept between 3 and 24 hours.
- Process according to any one of claims 1, 2, 3 or 4 wherein the current density at the anode is kept between 0.5 mA/cm2 to 20 mA/cm2 during electrolysis.
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US20050070614A1 (en) | 2003-06-21 | 2005-03-31 | Richards Alan K. | Anhydrous processing of methane into methane-sulfonic acid, methanol, and other compounds |
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WO2018146153A1 (en) | 2017-02-07 | 2018-08-16 | Grillo-Werke Ag | Method for the production of alkane sulfonic acids |
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WO2019212835A2 (en) * | 2018-03-10 | 2019-11-07 | Richards Alan K | Compounds, processes, and machinery for converting methane gas into methane-sulfonic acid |
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2021
- 2021-09-21 EP EP21198115.4A patent/EP4151774A1/en not_active Withdrawn
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US2493038A (en) | 1946-05-31 | 1950-01-03 | Houdry Process Corp | Reaction of methane with sulfur trioxide |
WO2004041399A2 (en) | 2002-11-05 | 2004-05-21 | Richards Alan K | Anhydrous conversion of methane and other light alkanes into methanol and other derivatives, using radical pathways and chain reactions with minimal waste products |
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US7119226B2 (en) | 2004-04-20 | 2006-10-10 | The Penn State Research Foundation | Process for the conversion of methane |
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