CN110257848B - Molten salt electrochemical method for oxidizing methane to hydrogen and carbon monoxide at medium and low temperature - Google Patents
Molten salt electrochemical method for oxidizing methane to hydrogen and carbon monoxide at medium and low temperature Download PDFInfo
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- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 title claims abstract description 160
- 150000003839 salts Chemical class 0.000 title claims abstract description 82
- UGFAIRIUMAVXCW-UHFFFAOYSA-N Carbon monoxide Chemical compound [O+]#[C-] UGFAIRIUMAVXCW-UHFFFAOYSA-N 0.000 title claims abstract description 20
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 title claims abstract description 20
- 229910002091 carbon monoxide Inorganic materials 0.000 title claims abstract description 20
- 239000001257 hydrogen Substances 0.000 title claims abstract description 20
- 229910052739 hydrogen Inorganic materials 0.000 title claims abstract description 20
- 230000001590 oxidative effect Effects 0.000 title claims abstract description 9
- 238000002848 electrochemical method Methods 0.000 title claims abstract description 8
- 238000005868 electrolysis reaction Methods 0.000 claims abstract description 24
- 239000001301 oxygen Substances 0.000 claims abstract description 22
- 229910052760 oxygen Inorganic materials 0.000 claims abstract description 22
- 238000007254 oxidation reaction Methods 0.000 claims abstract description 20
- 230000003647 oxidation Effects 0.000 claims abstract description 19
- 239000003792 electrolyte Substances 0.000 claims abstract description 18
- -1 oxygen ions Chemical class 0.000 claims abstract description 15
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims abstract description 7
- 229910052751 metal Inorganic materials 0.000 claims description 30
- 239000002184 metal Substances 0.000 claims description 30
- KWGKDLIKAYFUFQ-UHFFFAOYSA-M lithium chloride Chemical group [Li+].[Cl-] KWGKDLIKAYFUFQ-UHFFFAOYSA-M 0.000 claims description 16
- 238000000034 method Methods 0.000 claims description 16
- 230000008569 process Effects 0.000 claims description 13
- WCUXLLCKKVVCTQ-UHFFFAOYSA-M Potassium chloride Chemical compound [Cl-].[K+] WCUXLLCKKVVCTQ-UHFFFAOYSA-M 0.000 claims description 12
- CDBYLPFSWZWCQE-UHFFFAOYSA-L Sodium Carbonate Chemical compound [Na+].[Na+].[O-]C([O-])=O CDBYLPFSWZWCQE-UHFFFAOYSA-L 0.000 claims description 12
- FAPWRFPIFSIZLT-UHFFFAOYSA-M Sodium chloride Chemical compound [Na+].[Cl-] FAPWRFPIFSIZLT-UHFFFAOYSA-M 0.000 claims description 12
- 229910045601 alloy Inorganic materials 0.000 claims description 11
- 239000000956 alloy Substances 0.000 claims description 11
- BWHMMNNQKKPAPP-UHFFFAOYSA-L potassium carbonate Chemical compound [K+].[K+].[O-]C([O-])=O BWHMMNNQKKPAPP-UHFFFAOYSA-L 0.000 claims description 10
- 239000007772 electrode material Substances 0.000 claims description 9
- 229910021607 Silver chloride Inorganic materials 0.000 claims description 7
- 150000003841 chloride salts Chemical class 0.000 claims description 7
- HKZLPVFGJNLROG-UHFFFAOYSA-M silver monochloride Chemical compound [Cl-].[Ag+] HKZLPVFGJNLROG-UHFFFAOYSA-M 0.000 claims description 7
- BVKZGUZCCUSVTD-UHFFFAOYSA-L Carbonate Chemical compound [O-]C([O-])=O BVKZGUZCCUSVTD-UHFFFAOYSA-L 0.000 claims description 6
- 229910002651 NO3 Inorganic materials 0.000 claims description 6
- NHNBFGGVMKEFGY-UHFFFAOYSA-N Nitrate Chemical compound [O-][N+]([O-])=O NHNBFGGVMKEFGY-UHFFFAOYSA-N 0.000 claims description 6
- QAOWNCQODCNURD-UHFFFAOYSA-L Sulfate Chemical compound [O-]S([O-])(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-L 0.000 claims description 6
- 150000004673 fluoride salts Chemical class 0.000 claims description 6
- 229910000027 potassium carbonate Inorganic materials 0.000 claims description 6
- 239000001103 potassium chloride Substances 0.000 claims description 6
- 229910000029 sodium carbonate Inorganic materials 0.000 claims description 6
- 239000011780 sodium chloride Substances 0.000 claims description 6
- 229910001030 Iron–nickel alloy Inorganic materials 0.000 claims description 5
- XGZVUEUWXADBQD-UHFFFAOYSA-L lithium carbonate Chemical group [Li+].[Li+].[O-]C([O-])=O XGZVUEUWXADBQD-UHFFFAOYSA-L 0.000 claims description 4
- 229910052808 lithium carbonate Inorganic materials 0.000 claims description 4
- IIPYXGDZVMZOAP-UHFFFAOYSA-N lithium nitrate Chemical group [Li+].[O-][N+]([O-])=O IIPYXGDZVMZOAP-UHFFFAOYSA-N 0.000 claims description 4
- INHCSSUBVCNVSK-UHFFFAOYSA-L lithium sulfate Chemical group [Li+].[Li+].[O-]S([O-])(=O)=O INHCSSUBVCNVSK-UHFFFAOYSA-L 0.000 claims description 4
- 229910002119 nickel–yttria stabilized zirconia Inorganic materials 0.000 claims description 4
- FGIUAXJPYTZDNR-UHFFFAOYSA-N potassium nitrate Chemical compound [K+].[O-][N+]([O-])=O FGIUAXJPYTZDNR-UHFFFAOYSA-N 0.000 claims description 4
- 229910000367 silver sulfate Inorganic materials 0.000 claims description 4
- VWDWKYIASSYTQR-UHFFFAOYSA-N sodium nitrate Chemical compound [Na+].[O-][N+]([O-])=O VWDWKYIASSYTQR-UHFFFAOYSA-N 0.000 claims description 4
- 239000006260 foam Substances 0.000 claims description 3
- FUJCRWPEOMXPAD-UHFFFAOYSA-N Li2O Inorganic materials [Li+].[Li+].[O-2] FUJCRWPEOMXPAD-UHFFFAOYSA-N 0.000 claims description 2
- KKCBUQHMOMHUOY-UHFFFAOYSA-N Na2O Inorganic materials [O-2].[Na+].[Na+] KKCBUQHMOMHUOY-UHFFFAOYSA-N 0.000 claims description 2
- 239000007832 Na2SO4 Substances 0.000 claims description 2
- BQCADISMDOOEFD-UHFFFAOYSA-N Silver Chemical compound [Ag] BQCADISMDOOEFD-UHFFFAOYSA-N 0.000 claims description 2
- PMZURENOXWZQFD-UHFFFAOYSA-L Sodium Sulfate Chemical compound [Na+].[Na+].[O-]S([O-])(=O)=O PMZURENOXWZQFD-UHFFFAOYSA-L 0.000 claims description 2
- 229910052925 anhydrite Inorganic materials 0.000 claims description 2
- VTYYLEPIZMXCLO-UHFFFAOYSA-L calcium carbonate Substances [Ca+2].[O-]C([O-])=O VTYYLEPIZMXCLO-UHFFFAOYSA-L 0.000 claims description 2
- 229910000019 calcium carbonate Inorganic materials 0.000 claims description 2
- 239000001110 calcium chloride Substances 0.000 claims description 2
- 229910001628 calcium chloride Inorganic materials 0.000 claims description 2
- 229910001634 calcium fluoride Inorganic materials 0.000 claims description 2
- ZCCIPPOKBCJFDN-UHFFFAOYSA-N calcium nitrate Inorganic materials [Ca+2].[O-][N+]([O-])=O.[O-][N+]([O-])=O ZCCIPPOKBCJFDN-UHFFFAOYSA-N 0.000 claims description 2
- 125000005587 carbonate group Chemical group 0.000 claims description 2
- XUCJHNOBJLKZNU-UHFFFAOYSA-M dilithium;hydroxide Chemical compound [Li+].[Li+].[OH-] XUCJHNOBJLKZNU-UHFFFAOYSA-M 0.000 claims description 2
- TWRXJAOTZQYOKJ-UHFFFAOYSA-L magnesium chloride Substances [Mg+2].[Cl-].[Cl-] TWRXJAOTZQYOKJ-UHFFFAOYSA-L 0.000 claims description 2
- 229910001629 magnesium chloride Inorganic materials 0.000 claims description 2
- 229910001635 magnesium fluoride Inorganic materials 0.000 claims description 2
- OTYBMLCTZGSZBG-UHFFFAOYSA-L potassium sulfate Chemical compound [K+].[K+].[O-]S([O-])(=O)=O OTYBMLCTZGSZBG-UHFFFAOYSA-L 0.000 claims description 2
- 229910052939 potassium sulfate Inorganic materials 0.000 claims description 2
- WOCIAKWEIIZHES-UHFFFAOYSA-N ruthenium(IV) oxide Inorganic materials O=[Ru]=O WOCIAKWEIIZHES-UHFFFAOYSA-N 0.000 claims description 2
- 229910052709 silver Inorganic materials 0.000 claims description 2
- 239000004332 silver Substances 0.000 claims description 2
- 229910052938 sodium sulfate Inorganic materials 0.000 claims description 2
- 229910001233 yttria-stabilized zirconia Inorganic materials 0.000 claims description 2
- UXVMQQNJUSDDNG-UHFFFAOYSA-L Calcium chloride Chemical compound [Cl-].[Cl-].[Ca+2] UXVMQQNJUSDDNG-UHFFFAOYSA-L 0.000 claims 1
- 239000007789 gas Substances 0.000 abstract description 43
- 238000006243 chemical reaction Methods 0.000 abstract description 29
- 230000015572 biosynthetic process Effects 0.000 abstract description 13
- 238000003786 synthesis reaction Methods 0.000 abstract description 13
- 229910052799 carbon Inorganic materials 0.000 abstract description 6
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 abstract description 5
- 230000009286 beneficial effect Effects 0.000 abstract description 4
- 230000008878 coupling Effects 0.000 abstract description 4
- 238000010168 coupling process Methods 0.000 abstract description 4
- 238000005859 coupling reaction Methods 0.000 abstract description 4
- 230000008021 deposition Effects 0.000 abstract description 4
- 229910052593 corundum Inorganic materials 0.000 description 21
- 239000010431 corundum Substances 0.000 description 21
- 238000010438 heat treatment Methods 0.000 description 17
- 239000000047 product Substances 0.000 description 12
- 238000005516 engineering process Methods 0.000 description 10
- OKKJLVBELUTLKV-UHFFFAOYSA-N Methanol Chemical compound OC OKKJLVBELUTLKV-UHFFFAOYSA-N 0.000 description 9
- 238000007789 sealing Methods 0.000 description 9
- WSFSSNUMVMOOMR-UHFFFAOYSA-N Formaldehyde Chemical compound O=C WSFSSNUMVMOOMR-UHFFFAOYSA-N 0.000 description 6
- 238000004817 gas chromatography Methods 0.000 description 6
- 239000000203 mixture Substances 0.000 description 6
- 239000010405 anode material Substances 0.000 description 5
- 239000011261 inert gas Substances 0.000 description 5
- 239000007788 liquid Substances 0.000 description 5
- 239000010935 stainless steel Substances 0.000 description 5
- 229910001220 stainless steel Inorganic materials 0.000 description 5
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 5
- 239000000919 ceramic Substances 0.000 description 4
- 230000008859 change Effects 0.000 description 4
- 238000005265 energy consumption Methods 0.000 description 4
- 238000002156 mixing Methods 0.000 description 4
- 239000003345 natural gas Substances 0.000 description 4
- 230000001105 regulatory effect Effects 0.000 description 4
- 239000007787 solid Substances 0.000 description 4
- 239000000126 substance Substances 0.000 description 4
- 238000011161 development Methods 0.000 description 3
- 229930195733 hydrocarbon Natural products 0.000 description 3
- 150000002430 hydrocarbons Chemical class 0.000 description 3
- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 description 2
- 230000010718 Oxidation Activity Effects 0.000 description 2
- 239000013064 chemical raw material Substances 0.000 description 2
- 238000001816 cooling Methods 0.000 description 2
- 239000000446 fuel Substances 0.000 description 2
- 150000002500 ions Chemical class 0.000 description 2
- 230000007774 longterm Effects 0.000 description 2
- 238000002844 melting Methods 0.000 description 2
- 230000008018 melting Effects 0.000 description 2
- 239000003208 petroleum Substances 0.000 description 2
- 239000000758 substrate Substances 0.000 description 2
- 238000005303 weighing Methods 0.000 description 2
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 1
- 150000001336 alkenes Chemical class 0.000 description 1
- 229910021529 ammonia Inorganic materials 0.000 description 1
- 239000006227 byproduct Substances 0.000 description 1
- 150000005323 carbonate salts Chemical class 0.000 description 1
- 150000001875 compounds Chemical class 0.000 description 1
- 208000012839 conversion disease Diseases 0.000 description 1
- 238000005336 cracking Methods 0.000 description 1
- 230000009849 deactivation Effects 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 229910001873 dinitrogen Inorganic materials 0.000 description 1
- 238000001035 drying Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 230000005518 electrochemistry Effects 0.000 description 1
- 238000001914 filtration Methods 0.000 description 1
- 239000001095 magnesium carbonate Substances 0.000 description 1
- 229910000021 magnesium carbonate Inorganic materials 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 229910044991 metal oxide Inorganic materials 0.000 description 1
- 150000004706 metal oxides Chemical class 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- JRZJOMJEPLMPRA-UHFFFAOYSA-N olefin Natural products CCCCCCCC=C JRZJOMJEPLMPRA-UHFFFAOYSA-N 0.000 description 1
- 239000005416 organic matter Substances 0.000 description 1
- 238000005691 oxidative coupling reaction Methods 0.000 description 1
- 238000002360 preparation method Methods 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
- 238000002407 reforming Methods 0.000 description 1
- 238000012827 research and development Methods 0.000 description 1
Images
Classifications
-
- 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
- C25B1/00—Electrolytic production of inorganic compounds or non-metals
-
- 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
- C25B1/00—Electrolytic production of inorganic compounds or non-metals
- C25B1/01—Products
- C25B1/02—Hydrogen or oxygen
-
- 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
- C25B9/00—Cells or assemblies of cells; Constructional parts of cells; Assemblies of constructional parts, e.g. electrode-diaphragm assemblies; Process-related cell features
- C25B9/17—Cells comprising dimensionally-stable non-movable electrodes; Assemblies of constructional parts thereof
Abstract
The invention discloses a fused salt electrochemical method for oxidizing methane into hydrogen and carbon monoxide at a medium and low temperature, which comprises the steps of adopting a three-electrode system consisting of a working anode, a reference electrode and a counter electrode in a low-temperature fused salt electrolyte containing oxygen ions, directly introducing methane to the surface of the working anode at the flow rate of 50-200 mL/min at the temperature of 400-700 ℃, and electrochemically oxidizing the methane on the working anode to generate the hydrogen and the carbon monoxide by adopting constant-potential electrolysis and correcting the anode potential compared with the oxygen evolution potential. The medium-low temperature molten salt pool provided by the invention can reduce the reaction temperature of partial oxidation of methane by a coupling electrochemical means, and provides a new technical route for converting methane into synthesis gas in industry to directly match with downstream Fischer-Tropsch reaction; in particular, the abundant oxygen ions in the molten salt are beneficial to reducing the carbon deposition of the anode.
Description
Technical Field
The invention belongs to the field of efficient energy conversion and utilization, and particularly relates to a fused salt electrochemical method for oxidizing methane into hydrogen and carbon monoxide at a medium and low temperature.
Background
With the rapid development of economic society, the human consumption of energy is increasing day by day, and in order to effectively solve the problem of energy shortage faced by human, the existing fossil energy must be used economically and efficiently. Natural gas is a relatively abundant fossil energy contained in the earth, and can be directly used as fuel to provide energy, and can also be used as a chemical raw material in chemical fields of ammonia synthesis, methanol synthesis and derivatives thereof, and the consumption of the chemical fields is only about 8% of the total consumption of the natural gas. This is mainly due to the fact that the main component of natural gas is methane, which is known as the most structurally stable organic molecule and is much more difficult to activate than other hydrocarbons. However, in the long term of development, with the decrease of fossil resources such as petroleum and the increase of difficulty in exploitation, natural gas may be used as a main energy source and a chemical raw material instead of petroleum, and therefore, research and development of a high-efficiency methane conversion and utilization technology is an extremely hot issue internationally. Methane conversion technology can be broadly divided into direct conversion technology and indirect conversion technology. The direct conversion technique also includes the partial oxidation of methane to prepare organic oxygen-containing compound and the oxidative coupling of methane to prepare multi-carbon alkane, olefin and the like, wherein the partial oxidation of methane to prepare C1 organic matter is considered to be the most importantRoute of industrial potential, but byproducts CO and CO2The generation of the methanol and the formaldehyde is difficult to inhibit, the oxidation speed of the target products of the methanol and the formaldehyde is much higher than that of the methane, and the like, and the related technology still stays at the laboratory level more. The indirect methane conversion technology is to prepare synthesis gas from methane and then synthesize various chemical raw materials and oil products from the synthesis gas. As the technology for producing liquid hydrocarbons or hydrocarbons as main fuels from synthesis gas by the fischer-tropsch reaction is mature, indirect conversion technology is more industrially selected to utilize methane. However, the indirect conversion technology still has considerable disadvantages, including more complicated flow, high energy consumption, higher production cost, etc. The main reason for the complicated process is that the current main way for converting methane into synthesis gas is dry and wet reforming of methane (see formulas 1 and 2), both reactions are strong endothermic reactions, the reaction usually requires a high temperature of more than 800 ℃, and the further conversion of synthesis gas usually requires a high temperature and the mismatch of the temperatures in the two processes under medium and low temperature conditions, which results in huge overall energy consumption and complicated process.
CH4+H2O＝CO+3H2ΔH298K＝+206kJ/mol (1)
CH4+CO2＝2CO+2H2ΔH298K＝+247kJ/mol (2)
2CH4+O2＝2CO+4H2ΔH298K＝-36kJ/mol (3)
Therefore, it is of great practical significance to reduce the operating temperature of methane conversion to syngas, and partial oxidation of methane is a desirable solution to this problem. First, the partial oxidation of methane is an exothermic reaction (see formula 3), which makes it possible to lower the reaction temperature; in particular, it is hopeful to further reduce the reaction temperature of methane partial oxidation by coupling electrochemical means. At present, the electrochemical partial oxidation of methane mostly occurs in a Solid Oxide Electrolytic Cell (SOEC), is limited by the bottleneck problems of low-temperature electron conductivity and low ion conductivity of a solid oxide electrode and an electrolyte, and still cannot reduce the reaction conversion temperature to a medium-low temperature; particularly, methane is easy to generate cracking reaction under high temperature condition to generate simple substance carbon, which causes deactivation of carbon deposition on the anode and influences the stability of the electrochemical system under long-term working condition. Therefore, it is necessary to provide an electrolytic cell which can really operate under the medium-low temperature condition, and the molten salt electrolytic cell can operate under the medium-low temperature condition, and has the advantages of high ionic conductivity of electrolyte, wide electrode selection range and the like; the development of the molten salt electrochemical method for oxidizing methane into hydrogen and carbon monoxide at medium and low temperature has important economic value and practical significance.
Disclosure of Invention
The invention provides a molten salt electrochemical method for oxidizing methane into hydrogen and carbon monoxide at medium and low temperature, aiming at the defects that the existing methane conversion preparation synthesis gas needs high temperature and is matched with the downstream technical process. The method can prepare the synthesis gas by using methane under the condition of medium and low temperature, solves the problem that the synthesis gas prepared by methane conversion needs high temperature and is difficult to be directly matched with downstream Fischer-Tropsch reaction, realizes the purpose of reducing the overall energy consumption, and simultaneously realizes simple overall structure and convenient use of the device.
In order to achieve the purpose, the invention adopts the following technical scheme:
a molten salt electrochemical method for oxidizing methane to hydrogen and carbon monoxide at a medium and low temperature is characterized in that a three-electrode system consisting of a working anode, a reference electrode and a counter electrode is adopted in low-temperature molten salt electrolyte containing oxygen ions, methane is directly introduced to the surface of the working anode at a flow rate of 50-200 mL/min at the temperature of 400-700 ℃, constant-potential electrolysis is adopted, the potential of the working anode is more positive than the oxygen evolution potential, and the methane is electrochemically oxidized on the working anode to generate the hydrogen and the carbon monoxide.
The low-temperature molten salt electrolyte is any one of carbonate, chloride salt, fluoride salt, nitrate or sulfate; wherein the carbonate is Li2CO3、Na2CO3、K2CO3、CaCO3Or MgCO3One or more mixed salts of LiCl, NaCl, KCl and CaCl2Or MgCl2The fluoride salt is one or more of LiF, NaF, KF and CaF2Or MgF2The nitrate is LiNO3、NaNO3、KNO3、Ca(NO3)2Or Mg (NO)3)2The sulfate is Li2SO4、Na2SO4、K2SO4、CaSO4Or MgSO 24One or more mixed salts of (a).
When the low-temperature molten salt electrolyte is a chloride salt or a fluoride salt, the oxygen ions are derived from an added oxide.
When the low-temperature molten salt electrolyte is carbonate or nitrate or sulfate, the oxygen ions come from the low-temperature molten salt electrolyte or an added oxide.
The additional oxide comprises Li2O、Na2O、K2O、CaO、MgO、CO2Or SO2Any one or more of.
Preferably, the low-temperature molten salt electrolyte is mixed salt of three chloride salts of LiCl, NaCl and KCl with the molar ratio of 47.5:15:37.5, and the melting point of the mixed salt of the three chloride salts is 399 ℃; or the low-temperature molten salt electrolyte is Li with the molar ratio of 43.5:31.5:252CO3、Na2CO3、K2CO3Three mixed carbonate salts having a melting point of 393 ℃.
The working anode adopts metal, alloy, metal oxide, metal ceramic and perovskite type ceramic which are not corroded by molten salt heat and electrochemistry or can form a stable compact oxidation film as the working anode electrode material. The working anode electrode material is metal Au, metal Ag, metal Pt, metal Ni, metal Cu, NiFe alloy, NiFeCu alloy, RuO2Ni-YSZ, Co-YSZ, Cu-GDC, Ru-GDC, and LSM.
The counter electrode adopts metal or alloy which is not corroded by molten salt heat or can form a stable and compact oxide film as a counter electrode material. The counter electrode material is any one of metal Au, metal Ag, metal Pt, metal Ni, metal Cu, NiFe alloy and NiFeCu alloy.
The working anode and the counter electrode are in a sheet, net, foam metal structure or porous structure.
The reference electrode is Ag/Ag2SO4Or Ag/AgCl high temperature reference electrode, in which Ag2SO4Or the AgCl concentration is 0.1mol/kg, and silver wires are used as reference electrode materials.
The principles of the embodiments of the present invention are as follows:
carbonate or oxygen ions first undergo an oxidation reaction at the working anode (see formulas 4 and 5), and active oxygen having high oxidation activity is generated by the reaction, and this active oxygen further oxidizes methane (see formula 6).
CO3 2--2e-＝CO2+Oactive(4)
O2--2e-＝Oactive(5)
CH4+Oactive＝CO+2H2(6)
Compared with the prior art, the method has the following advantages and prominent effects: the working temperature of methane partial oxidation is successfully reduced by utilizing the characteristic that a molten salt pool can work at a medium-low temperature and coupling an electrochemical technology, and the energy consumption is reduced and simultaneously the working temperature can be better matched with the downstream Fischer-Tropsch reaction temperature. ② the fused salt has higher ion conduction capability compared with the solid oxide electrolyte. And the low and medium temperature working conditions are not beneficial to anode carbon deposition, and meanwhile, the abundant oxygen ions in the molten salt are beneficial to reducing the anode carbon deposition, which are beneficial to prolonging the service life of the system. And compared with a solid oxide electrolytic cell, the electrode material in the molten salt electrolytic cell has wider selection range.
Drawings
FIG. 1 is a schematic view of the flow structure of the present invention;
in the figure, ① methane gas cylinder, ② nitrogen gas cylinder, ③ pressure reducing valve, ④ gas flowmeter, ⑤ electrochemical workstation, ⑥ sealing element, ⑦ tubular electric furnace, ⑧ corundum tube, ⑨ working anode, ⑩ corundum crucible,
a high-temperature reference electrode is arranged on the substrate,
the counter electrode is arranged on the back surface of the substrate,
a molten salt of a molten salt,
a filtering and drying device is arranged in the filter,
gas chromatography.
FIG. 2 is a constant potential electrolysis curve of the working anode of example 1 in the present invention.
FIG. 3 is a constant potential electrolysis curve of the working anode of example 2 in the present invention.
FIG. 4 is a graph of the change in the concentration of gaseous products in the potentiostatic electrolysis of the working anode of example 1 in accordance with the present invention;
after the start of electrolysis, the current was stabilized at 20mA cm-2The corresponding gas concentrations vary significantly: the methane concentration is reduced by 320ppm, H2The concentration increased by 10ppm and the CO concentration increased by 4 ppm.
FIG. 5 is a graph of the change in concentration of gaseous products in constant potential electrolysis at the working anode of example 2 in accordance with the present invention;
after the start of electrolysis, the current was stabilized at 30mA cm-2The corresponding gas concentrations vary significantly: the methane concentration is reduced by 500ppm, H2The concentration increased by 20ppm and the CO concentration increased by 11 ppm.
Detailed Description
The following is a specific embodiment based on the technical solution of the present invention, and the present invention can be better understood through the following embodiments in combination with the accompanying drawings. It should be noted that the present invention is not limited to the following embodiments, and those skilled in the art can make insubstantial modifications or changes in form and content of the present invention based on the principle of the present invention, and fall within the scope of the present invention.
[ example 1 ]
Weighing Li2CO3，Na2CO3，K2CO3(the molar ratio is 43.5:31.5:25) of 300g in total, the mixture is mechanically and uniformly mixed, then the mixture is placed into a corundum crucible and is placed into a tubular electric furnace, the temperature is increased to 300 ℃ at the heating rate of 5 ℃/min, the temperature is kept for 24h to remove water in salt, then the temperature is increased to 600 ℃ at the heating rate of 5 ℃/min, the temperature is kept for half an hour until the salt is completely melted to form uniform mixed salt, and then the temperature is reduced to 500 ℃ for keeping. Sealing the upper and lower ends of the tubular electric furnace by stainless steel flanges, and introducing inert gas N through the opening of the lower square flange2The corresponding flow rate was 200 mL/min. NiFe alloy (64:36) is selected as a working anode material, and the electrode structure is sheet-shaped. The working anode is directly contacted with the thin corundum tube which is introduced with methane gas, and the whole body is sealed in a gas chamber which is made of a thick corundum tube, so that the working electrode is ensured to be positioned below the liquid level of the molten salt. As shown in FIG. 1, a counter electrode and a working electrode were inserted into a molten salt electrolysis cell while connecting gas flow paths as shown in FIG. 1. Regulating the methane inlet flow rate to be 50mL/min and keeping the methane inlet flow rate for 1h, and connecting the three electrodes with an electrochemical workstation. The electrochemical workstation is provided with a constant potential electrolysis program with the setting parameter of 1.0V vs2SO4And the current curve with time was recorded, as shown in figure 2 for the constant potential electrolysis curve of the working anode. Meanwhile, the on-line gas chromatography is started to detect the gas product on line in real time, as shown in a working anode constant potential electrolysis corresponding gas product concentration change curve shown in figure 4, after the electrolysis starts, the current is stabilized at 20mA cm-2The concentration of the corresponding gas is obviously changed, the concentration of methane is reduced by 320ppm, and H2The concentration increased by 10ppm and the CO concentration increased by 4 ppm.
[ example 2 ]
Weighing Li2CO3，Na2CO3，K2CO3(molar ratio 47.5:30.5:23) 300g in total, Li in an amount of 5% by mass of the mixed salt was added2O increasing the oxygen ion content in the molten salt, mechanically mixing uniformly, placing the mixture into a corundum crucible, placing the corundum crucible into a tubular electric furnace, heating to 300 ℃ at the heating rate of 10 ℃/min, preserving heat for 24 hours to remove water in the salt, and heating to the temperature of 10 ℃/minAnd (3) keeping the temperature for half an hour at 600 ℃ until the salt is completely melted to form uniform mixed salt, and then cooling to 500 ℃ for keeping. Sealing the upper and lower ends of the tubular electric furnace by stainless steel flanges, and introducing inert gas N through the opening of the lower square flange2The corresponding flow rate was 200 mL/min. The metal Au is selected as a working anode material, the electrode structure is in a sheet shape, the working anode is directly contacted with the thin corundum tube which is filled with methane gas, and the whole body is sealed in a gas cavity which is made of a thick corundum tube, so that the working electrode is ensured to be positioned below the liquid level of the molten salt. As shown in FIG. 1, a counter electrode and a working electrode were inserted into a molten salt electrolysis cell while connecting gas flow paths as shown in FIG. 1. Regulating the methane inlet flow rate to be 100mL/min and keeping the methane inlet flow rate for 0.5h, and connecting the three electrodes with an electrochemical workstation. The electrochemical workstation is provided with a constant potential electrolysis program with the setting parameter of 1.0V vs2SO4And the current curve with time was recorded as shown in figure 3 for the constant potential electrolysis curve of the working anode. Meanwhile, the on-line gas chromatography is started to detect the gas product on line in real time, as shown in the graph of fig. 5, the working anode constant potential electrolysis corresponds to the concentration change curve of the gas product, and after the electrolysis starts, the current is stabilized at 30mA cm-2The concentration of the corresponding gas is obviously changed, the concentration of methane is reduced by 500ppm, H2The concentration increased by 20ppm and the CO concentration increased by 11 ppm.
[ example 3 ]
LiCl, NaCl and KCl (molar ratio 47.5:15:37.5) are weighed to be 300g, Na accounting for 4 percent of the mass of the mixed salt is added2Increasing the oxygen ion content in the molten salt, mechanically mixing uniformly, putting the mixture into a corundum crucible, putting the corundum crucible into a tubular electric furnace, heating to 300 ℃ at the heating rate of 5 ℃/min, preserving heat for 24 hours to remove water in the salt, heating to 600 ℃ at the heating rate of 5 ℃/min, preserving heat for half an hour until the salt is completely melted to form uniform mixed salt, and then cooling to 400 ℃ for keeping. Sealing the upper end and the lower end of the tubular electric furnace by using stainless steel flanges, and introducing inert gas Ar through the lower square flange opening, wherein the corresponding flow rate is 200 mL/min. Selecting metal Au as a working anode material, wherein the electrode structure is in a net shape, directly contacting the working anode with a thin corundum tube filled with methane gas, and integrally sealing the working anode in a gas cavity made of a thick corundum tube to ensure the workThe electrode is located below the molten salt level. As shown in FIG. 1, a counter electrode and a working electrode were inserted into a molten salt electrolysis cell while connecting gas flow paths as shown in FIG. 1. The methane inlet flow rate was adjusted to 50mL/min and maintained for 2h, and the three electrodes were connected to an electrochemical workstation. The electrochemical workstation sets a constant potential electrolysis program with the parameters of 1.2V vs. Ag/AgCl and records the current curve along with the time. Meanwhile, the online gas chromatography is started to detect the gas product on line in real time. After the start of electrolysis, the current was stabilized at 25mA cm-2The concentration of the corresponding gas is obviously changed, the concentration of methane is reduced by 330ppm, H2The concentration increased by 25ppm and the CO concentration increased by 6 ppm.
[ example 4 ]
LiCl, NaCl and KCl (molar ratio 47.5:15:37.5) are weighed to be 300g, and Li accounting for 2 percent of the mass of the mixed salt is added2O increasing the oxygen ion content in the molten salt, mechanically mixing uniformly, putting the mixture into a corundum crucible, putting the corundum crucible into a tubular electric furnace, heating to 300 ℃ at the heating rate of 5 ℃/min, preserving heat for 24 hours to remove water in the salt, heating to 600 ℃ at the heating rate of 5 ℃/min, and preserving heat until the salt is completely melted to form uniform mixed salt. Sealing the upper and lower ends of the tubular electric furnace by stainless steel flanges, and introducing inert gas N through the opening of the lower square flange2The corresponding flow rate was 200 mL/min. Selecting metal ceramic Ni-YSZ as a working anode material, wherein the metal ceramic Ni-YSZ is in a porous structure, directly contacting the working anode with a thin corundum tube filled with methane gas, and integrally sealing the working anode in a gas chamber made of a thick corundum tube to ensure that a working electrode is positioned below the liquid level of molten salt. As shown in FIG. 1, a counter electrode and a working electrode were inserted into a molten salt electrolysis cell while connecting gas flow paths as shown in FIG. 1. Regulating the methane inlet flow rate to be 100mL/min and keeping the methane inlet flow rate for 1h, and connecting the three electrodes with an electrochemical workstation. The electrochemical workstation sets a constant potential electrolysis program with the parameters of 1.2V vs. Ag/AgCl and records the current curve along with the time. Meanwhile, the online gas chromatography is started to detect the gas product on line in real time. After the start of electrolysis, the current was stabilized at 120mA cm-2The concentration of the corresponding gas is obviously changed, the concentration of methane is reduced by 1200ppm, and H2The concentration is increased by 980ppm and the CO concentration is increased by 800ppm。
[ example 5 ]
LiCl 300g is weighed and Li with the mass of 5 percent of the mixed salt is added2O increasing the oxygen ion content in the molten salt, mechanically mixing uniformly, putting the mixture into a corundum crucible, putting the corundum crucible into a tubular electric furnace, heating to 300 ℃ at the heating rate of 5 ℃/min, keeping the temperature for 24 hours to remove water in the salt, heating to 700 ℃ at the heating rate of 5 ℃/min, and keeping the temperature. Sealing the upper end and the lower end of the tubular electric furnace by using stainless steel flanges, and introducing inert gas Ar through the lower square flange opening, wherein the corresponding flow rate is 200 mL/min. Selecting foam metal Ni as a working anode material, directly contacting the working anode with a thin corundum tube filled with methane gas, and integrally sealing the working anode in a gas chamber made of a thick corundum tube to ensure that a working electrode is positioned below the liquid level of molten salt. As shown in FIG. 1, a counter electrode and a working electrode were inserted into a molten salt electrolysis cell while connecting gas flow paths as shown in FIG. 1. Regulating the methane inlet flow rate to be 200mL/min and keeping the methane inlet flow rate for 1h, and connecting the three electrodes with an electrochemical workstation. The electrochemical workstation sets a constant potential electrolysis program with the parameters of 1.5V vs. Ag/AgCl and records the current curve along with the time. Meanwhile, the online gas chromatography is started to detect the gas product on line in real time. After the electrolysis, the current stabilized at 420mAcm-2The concentration of the corresponding gas is obviously changed, the concentration of the methane is reduced by 6500ppm, and H2The concentration increased 5900ppm, and the CO concentration increased 5400 ppm.
The principle involved in the embodiment of the invention is as follows:
carbonate or oxygen ions are first oxidized at the working anode (see formula 4, 5), and active oxygen having high oxidation activity is generated by the reaction to further oxidize methane (see formula 6). This also increases the range of materials available for the working anode to some extent.
CO3 2--2e-＝CO2+Oactive(4)
O2--2e-＝Oactive(5)
CH4+Oactive＝CO+2H2(6)
Fig. 2, 3, 4 and 5 show the constant potential electrolysis curves and the corresponding gas product concentration curves of the embodiment 1 and the embodiment 2, respectively, and the results prove that the possibility of realizing the electrochemical conversion of methane into synthesis gas at a medium and low temperature based on the molten salt electrolytic cell, and a new technical route is provided for the direct coupling of methane into synthesis gas and the downstream fischer-tropsch reaction in industry.
Claims (10)
1. A molten salt electrochemical method for oxidizing methane to hydrogen and carbon monoxide at medium and low temperature is characterized in that: in a low-temperature molten salt electrolyte containing oxygen ions, a three-electrode system consisting of a working anode, a reference electrode and a counter electrode is adopted, methane is directly introduced to the surface of the working anode at the temperature of 400-700 ℃ at the flow rate of 50-200 mL/min, constant potential electrolysis is adopted, the anode potential is more positive than the oxygen evolution potential, and the methane is electrochemically oxidized on the working anode to generate hydrogen and carbon monoxide.
2. A molten salt electrochemical process for the medium-low temperature oxidation of methane to hydrogen and carbon monoxide as claimed in claim 1 wherein: the low-temperature molten salt electrolyte is any one of carbonate, chloride salt, fluoride salt, nitrate or sulfate; wherein the carbonate is Li2CO3、Na2CO3、K2CO3、CaCO3The chloride salt is LiCl, or LiCl, NaCl, KCl, CaCl2、MgCl2The fluoride salt is LiF, NaF, KF, CaF2Or MgF2The nitrate is LiNO3、NaNO3、KNO3、Ca(NO3)2The sulfate is Li2SO4、Na2SO4、K2SO4、CaSO4Or MgSO 24Mixed salts of a plurality of (1).
3. A molten salt electrochemical process for the medium-low temperature oxidation of methane to hydrogen and carbon monoxide as claimed in claim 2 wherein: when the low-temperature molten salt electrolyte is a chloride salt or a fluoride salt, the oxygen ions are derived from an added oxide.
4. A molten salt electrochemical process for the medium-low temperature oxidation of methane to hydrogen and carbon monoxide as claimed in claim 2 wherein: when the low-temperature molten salt electrolyte is carbonate or nitrate or sulfate, the oxygen ions come from the low-temperature molten salt electrolyte or an added oxide.
5. A molten salt electrochemical process for the medium-low temperature oxidation of methane to hydrogen and carbon monoxide as claimed in claim 3 or 4 wherein: the additional oxide comprises Li2O、Na2O、K2O、CaO、MgO、CO2Or SO2Any one or more of.
6. A molten salt electrochemical process for the medium-low temperature oxidation of methane to hydrogen and carbon monoxide as claimed in claim 3 wherein: the low-temperature molten salt electrolyte is three mixed salts of LiCl, NaCl and KCl with the molar ratio of 47.5:15: 37.5.
7. A molten salt electrochemical process for the medium-low temperature oxidation of methane to hydrogen and carbon monoxide as claimed in claim 4 wherein: the low-temperature molten salt electrolyte is Li with a molar ratio of 43.5:31.5:252CO3、Na2CO3、K2CO3Three kinds of mixed salt.
8. A molten salt electrochemical process for the medium-low temperature oxidation of methane to hydrogen and carbon monoxide as claimed in any one of claims 1 to 4, 6 or 7 wherein: the working anode electrode material is metal Au, metal Ag, metal Pt, metal Ni, metal Cu, NiFe alloy, NiFeCu alloy, RuO2Any one of Ni-YSZ, Co-YSZ, Cu-GDC, Ru-GDC and LSM; the counter electrode material is any one of metal Au, metal Ag, metal Pt, metal Ni, metal Cu, NiFe alloy and NiFeCu alloy.
9. A molten salt electrochemical process for the medium-low temperature oxidation of methane to hydrogen and carbon monoxide as claimed in claim 8 wherein: the working anode and the counter electrode are in a sheet, net, foam metal structure or porous structure.
10. A molten salt electrochemical process for the medium-low temperature oxidation of methane to hydrogen and carbon monoxide as claimed in claim 9 wherein: the reference electrode is Ag/Ag2SO4Or Ag/AgCl high temperature reference electrode, in which Ag2SO4Or the AgCl concentration is 0.1mol/kg, and silver wires are used as reference electrode materials.
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