WO2015139136A1 - Procédé d'électroréduction de co2 - Google Patents

Procédé d'électroréduction de co2 Download PDF

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Publication number
WO2015139136A1
WO2015139136A1 PCT/CA2015/050206 CA2015050206W WO2015139136A1 WO 2015139136 A1 WO2015139136 A1 WO 2015139136A1 CA 2015050206 W CA2015050206 W CA 2015050206W WO 2015139136 A1 WO2015139136 A1 WO 2015139136A1
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Prior art keywords
bicarbonate
catholyte
carbon dioxide
reactor
salt
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PCT/CA2015/050206
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English (en)
Inventor
Clive M H BRERETON
Colin Oloman
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Brereton Clive M H
Colin Oloman
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Publication of WO2015139136A1 publication Critical patent/WO2015139136A1/fr

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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
    • C25B15/00—Operating or servicing cells
    • C25B15/08—Supplying or removing reactants or electrolytes; Regeneration of electrolytes
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/32—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols by electrical effects other than those provided for in group B01D61/00
    • B01D53/326—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols by electrical effects other than those provided for in group B01D61/00 in electrochemical cells
    • 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
    • C25B3/00—Electrolytic production of organic compounds
    • C25B3/20—Processes
    • C25B3/25—Reduction
    • 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
    • C25B9/19—Cells comprising dimensionally-stable non-movable electrodes; Assemblies of constructional parts thereof with diaphragms
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2257/00—Components to be removed
    • B01D2257/50—Carbon oxides
    • B01D2257/504—Carbon dioxide
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P20/00—Technologies relating to chemical industry
    • Y02P20/151—Reduction of greenhouse gas [GHG] emissions, e.g. CO2

Definitions

  • This invention pertains to the field of processes for the electro-chemical reduction of carbon dioxide, in particular, an improved process for the electro-reduction of carbon dioxide in alkaline conditions.
  • the present invention is an improved process for electro-reduction of CO2 (ERC) in alkaline condition, regarding its commercial application, by resolving the problems of CO 2 feed gas composition, reactant consumption, bicarbonate disposal and formate product concentration in a single integrated system.
  • EEC CO2
  • the present invention provides a process for the electrochemical reduction of carbon dioxide in an electroreduction reactor that yields a catholyte product, an anolyte product, and bicarbonate salt, the process comprising a step of separating the bicarbonate salt from the catholyte product and using the recovered bicarbonate salt to concentrate a carbon dioxide gas feed to the electroreduction reactor.
  • the present invention provides a process for the electrochemical reduction of carbon dioxide in an alkaline catholyte solution comprising the steps of: separating bicarbonates produced during the electrochemical reduction from the catholyte; converting the separated bicarbonates to carbonates; and using the carbonates from the previous step to concentrate a carbon dioxide feed gas to the process.
  • the process may further comprise recycling the bicarbonates to a catholyte feed.
  • the product of the electrochemical reduction of carbon dioxide may be a formate salt.
  • the product of the electrochemical reduction of carbon dioxide may be carbon monoxide.
  • the step of separating the bicarbonates may be by crystallization.
  • the step of concentrating a carbon dioxide gas feed may comprise converting bicarbonate salt to carbonate salt and using the carbonate salt to absorb carbon dioxide in a cyclic carbonate/bicarbonate C02 absorption/desorption system.
  • part of the bicarbonate salt from the absorption/desorption system may comprise the catholyte feed to the electroreduction reactor.
  • part of a supernatant solution from the bicarbonate crystallization may be recycled to the catholyte fed to the electroreduction reactor.
  • the desorbed carbon dioxide may be taken as the reactant feed to the electroreduction reactor.
  • part of the formate salt may be returned to the catholyte.
  • the separated bicarbonate salt may be converted to carbonate salt that is then recycled to the anolyte feed to the electoreduction reactor.
  • part of the anolyte product is recycled to the catholyte feed to the electroreduction reactor.
  • the concentration of bicarbonate in the catholyte product from the electroreduction reactor may be in the range from about 1 to 4 molar.
  • the concentration of formate in the catholyte product from the electroreduction reactor may range from about 0.5 to 6 molar.
  • the bicarbonate crystallization may be done at a temperature ranging from about 40 °C to 90 °C under a carbon dioxide partial pressure ranging from about 0.5 to 2 bar.
  • the catholyte pH may range from about 7 to 9.
  • the bicarbonate salt may be one of ammonium lithium, sodium and potassium bicarbonate.
  • the formate product concentration may be in the range of about 2 to 13 molar.
  • the bicarbonate may be crystallized under an atmosphere comprising carbon dioxide.
  • the concentration of carbon dioxide in the feed gas to the concentration step may be in the range of about 10 to 50 percent by volume.
  • the concentration of carbon dioxide in the gas leaving the concentration step may be in the range of about 70 to 99 percent by volume.
  • Figure 1 shows a flowsheet of a generic continuous process for the electroreduction of C0 2 .
  • Figure 2 shows a flowsheet of one manifestation of a process for the electro-reduction of C0 2 (ERC), according the present invention, to produce a solution of a formate salt such as potassium or sodium formate.
  • EEC electro-reduction of C0 2
  • Figure 3 shows a flowsheet of a second manifestation of a process for the electroreduction of C02 according to the present invention.
  • Figure 4 shows experimental results for Example 2.
  • Figure 5 shows a theoretical prediction of liquid phase composition from evaporation of a mixed potassium formate/bicarbonate solution.
  • Figure 1 shows a process for the electrochemical reduction of carbon dioxide to obtain C0 2 reduction products by cathode reactions with the generic form: xC0 2 + (y-2(z-2x))H + + ye " CxHyOz + (z-2x)H 2 0 Reaction 1
  • x, y and z may take integer values respectively of 1 to 3, 0 to 8 and 0 to 2, as exemplified in Table 1.
  • the process of Figure 1 has an electrochemical reactor A where carbon dioxide (CO 2 ) is reduced according to Reaction 1 , along with the associated reactor feed, recycle and product separation systems.
  • CO 2 carbon dioxide
  • the electrochemical reactor A may have single or multiple electrochemical cells of parallel plate or cylindrical shape, wherein each cell is divided into an anode chamber with anode B and a cathode chamber with cathode C by a separator D.
  • An electric power source E supplies direct current to the reactor at a voltage about 2 to 6 Volt/cell.
  • the process uses anode and cathode feed tanks F and G along with the respective product separators H and I.
  • an anode fresh feed J optionally mixed with recycle U, forms anolyte liquid K which is passed to the anode chamber B where it is converted to anode output L, to be subsequently separated to products M and N and an optional anolyte recycle U.
  • a cathode fresh feed O optionally mixed with recycle V, forms catholyte liquid Q which is mixed with C0 2 gas P and passed to the cathode chamber C where the mixture (P+Q) is converted to cathode output R, to be subsequently separated to products S and T and an optional catholyte recycle V.
  • the cathode C in the reactor A, includes a porous electrode with an electro-catalytic specific surface in the range about 100 to 100,000 m 2 /m 3 , which may include nano-structured surface embellishments, and may be in the form of a reticulate, foam, felt, matt, mesh, frit, fixed-bed, fluidized-bed, gas diffusion electrode (GDE), solid polymer electrode (SPE) or the like.
  • the cathode is fed by a mixture of a C0 2 containing gas P and a catholyte liquid solution Q in a volumetric flow ratio from about 1 to 1000, measured at 1 bar(abs), 273 K.
  • the gas P and liquid Q may be introduced separately to the cathode, or mixed before entering the cathode, then pass through the cathode in two-phase co-current flow.
  • the co-current fluid (P+Q) flow path through the porous cathode may be preferably in the so-called "flow-by” mode with fluid flow orthogonal to the electric current or optionally in the so-called “flow-though” mode with fluid flow parallel to the electric current.
  • the reactor may be oriented horizontally or sloped or preferably vertically, with the cathode fluid (P+Q) flow preferably upward but optionally downward.
  • the separator D may be a layer of an electronically non- conductive material that is inherently ionically conductive, or made ionically conductive by absorption of an electrolyte solution.
  • the preferred separator is an ion selective membrane such those under the trade names Nafion, Fumasep, VANADion, Neosepta and Selemion and PEEK as detailed in Table 4, and is preferably a cation exchange membrane (CEM) such as Nafion N424, with a selectivity above about 90%.
  • CEM cation exchange membrane
  • the separator may also comprise a layer of porous hydrophilic material such as asbestos, Zirfon R Perl (Agfa-Gevaert N.V.), Scimat (Freudenberg NonWovens), Celgard (Celgard LLC) and like materials used as separators in water electrolysers and electric batteries.
  • porous hydrophilic material such as asbestos, Zirfon R Perl (Agfa-Gevaert N.V.), Scimat (Freudenberg NonWovens), Celgard (Celgard LLC) and like materials used as separators in water electrolysers and electric batteries.
  • the electronically conductive anode material may be selected from those known to the art, including for example nickel, stainless steel, lead, conductive oxide (e.g. Pb0 2 , Sn0 2 ), diamond, platinised titanium, iridium oxide and mixed oxide coated titanium (DSE), and the like.
  • the anode may be a two-dimensional electrode or a three-dimensional (porous) electrode in the form of a reticulate, foam, felt, matt, mesh, frit, fixed-bed, fluidized-bed, gas-diffusion (GDE) or solid-polymer electrode (SPE).
  • the desired cathode products S,T,V and process conditions determine the choice of the electronically conductive cathode electro-catalyst material(s), which may be selected from the exemplary lists in Tables 2 and 3.
  • the anode reaction is complimentary to the cathode electro-reduction reaction 1 and may be chosen from a wide range of electro-oxidations exemplified by reactions 2 to 10.
  • the primary reactants at the anode may be soluble ionic species as in reactions 2 to 5, neutral species as in reactions 6 to 10, "immiscible" organic liquids as in reactions 7 and 8 or gases as in reactions 9 and 10.
  • Immiscible liquid and gas reactants, along with an aqueous liquid anolyte, may engender multi-phase flow at the anode which may include respectively a gas/liquid foam or liquid/liquid emulsion.
  • the anolyte K may be a non-aqueous solution of an electrolyte, but preferably an aqueous solution of an acid or base and/or salt with alkali metal or ammonium cations.
  • Corresponding reagents may be for example: sulphuric, hydrochloric, hydrobromic, phosphoric or methanesulphonic acid; sodium, potassium, rubidium, caesium or ammonium hydroxide or a sodium, potassium, rubidium, caesium, or ammonium salt of the above acids.
  • the anolyte may optionally include species to be engaged in oxidative redox couples, such as Ag 2+ / Ag 1 + ,Ce 4 7 Ce 3+ , Co 3+ / Co 2+ , Fe 3+ / Fe 2+ , Mn 3+ / Mn 2+ , V 5+ / V 4+ , organic couples such as quinone/hydroquinone and the like, in bare, complexed or chelated forms, with a redox potential matched to that of the desired anode process.
  • species to be engaged in oxidative redox couples such as Ag 2+ / Ag 1 + ,Ce 4 7 Ce 3+ , Co 3+ / Co 2+ , Fe 3+ / Fe 2+ , Mn 3+ / Mn 2+ , V 5+ / V 4+
  • organic couples such as quinone/hydroquinone and the like, in bare, complexed or chelated forms, with a redox potential matched to that of
  • the desired cathode products S,T,V and process conditions determine the choice of the electronically conductive cathode electro-catalyst material(s), which may be selected from the exemplary lists in Table 2 or from organo-metal complexes of cobalt, copper, iron, nickel, palladium and rhenium such as those in Table 3, on electronically conductive supports.
  • AFN (0.5 ohms.cm2)
  • the catholyte Q may be a non-aqueous solution of an electrolyte, but preferably an aqueous solution of an acid or base and/or salt with alkali metal or ammonium cations.
  • Corresponding reagents may be for example: sulphuric, hydrochloric, hydrobromic, phosphoric, methanesulphonic or formic acid; sodium, potassium, rubidium, caesium or ammonium hydroxide or a sodium, potassium, rubidium, caesium, or ammonium salt of the above acids, including the bicarbonate and carbonate salts.
  • the catholyte may optionally include species to be engaged in reductive redox couples, such as, Cr 3+ / Cr 2+ , Cu 2+ / Cu 1 + , Sn 4+ / Sn 2+ , Ti 3+ / Ti 2+ , V 3+ / V 2+ , organic couples such as quinone/hydroquinone and the like, in bare, complexed or chelated forms, with a redox potential matched to that of the desired cathode process.
  • the catholyte may contain chelating and/or surface active agents (surfactants) such as for example amino-carboxylates (e.g. EDTA, DTPA), phosphonates and quaternary ammonium salts.
  • surfactants such as for example amino-carboxylates (e.g. EDTA, DTPA), phosphonates and quaternary ammonium salts.
  • the feed gas P may contain about 1 to 100 volume % C0 2 and the cathode reactant mixture (P+Q) may enter and/or traverse the porous cathode in a two-phase flow pattern such as described in reference 3 as: "bubbly", “plug”, “slug”, “dispsersed” or “froth” (i.e. a foam).
  • Methods for separating the anode and cathode products may be for example gas/liquid or liquid/liquid disengagement, crystallization, filtration, liquid extraction and distillation.
  • Equation 1 shows the reaction in acid but most practical ERC processes use an alkaline catholyte with pH in the range about 7 to 10.
  • two exemplary products of interest are formate salts and carbon monoxide, for which the cathode reactions are:
  • each mole of the desired product e.g. HC0 2 " or CO
  • each mole of the desired product may be accompanied by about 1 to 4 moles of undesired bicarbonate, in the form of a bicarbonate salt such as KHCO3.
  • This bicarbonate is responsible for excess consumption of its associated counter-ions (e.g. K + ) and of C0 2 , both of which increase the process costs.
  • a similar situation occurs with ERC under alkaline conditions to obtain a variety of products, such as those in Table 1.
  • An objective of the present invention is to reduce, and preferably resolve, the problems associated with bicarbonate formation during the reduction of C0 2 in alkaline conditions.
  • K + potassium
  • the K + may be replaced by other alkali metal cations (e.g. Li + , Na + , Rb + , Cs + ) or ammonium (NH + ).
  • the invention may not be so readily applied to Rb + and Cs + due to the relatively high solubility of their bicarbonate salts in water.
  • the items 1 to 12 are process units specified as follows: an electrochemical reactor 1 , a separator 2, a separator 3, a divider 4, a reactor/separator 5, a mixer 6, a reactor/separator 7, a divider 8, a reactor/separator 9, a mixer 10, a mixer 11 , and a mixer 12.
  • the reference numbers 13 to 35 refer to process streams whose functions are described below.
  • the reactor/separator 7, divider 8 and reactor/separator 9 with respective process streams 13,14,15,16,17,19,20,30,31 constitute the conventional cyclic carbonate/bicarbonate C0 2 absorption/stripping process in which a waste gas stream 13, typically with about 10 to 40 volume % C0 2 is purified to above about 80 volume % C0 2 in stream 20, via absorption into a potassium carbonate solution 31 to form a potassium bicarbonate solution 15.
  • the unwanted gases e.g.
  • N 2 , 0 2 are rejected in stream 14 then 15 is divided into 16 and 17 and C0 2 is stripped from the latter into 20.
  • the remaining bicarbonate 16 is mixed with the catholyte product recycle 29 to give stream 18, an aqueous potassium bicarbonate-formate mixture which is combined with carbon dioxide gas 22 and fed to the cathode of the electrochemical reactor.
  • the electrochemical reactor With alkaline conditions in the cathode the electrochemical reactor converts C0 2 to a mixture of bicarbonate and formate salts 24 from which unconverted C0 2 27 and potassium bicarbonate 26 are separated in separator 3 to give potassium formate solution 25 that is subsequently divided to a product 28 and the aforementioned recycle 29.
  • the potassium bicarbonate 26 is decomposed by heat and separated into C0 2 gas 21 and a potassium carbonate solution 30.
  • the former is mixed with stream 20 to feed the ERC reactor and the latter is mixed with the recycled potassium carbonate 19 to give a potassium carbonate solution 31 that feeds the aforementioned C0 2 concentration process.
  • a controlled pH acid anolyte solution 32 enters the ERC anode where the anode reaction converts water to protons (H+) and oxygen gas by reaction 6 to give an anolyte exit stream 33.
  • Oxygen 35 is separated in the recycle separator/tank 2 where a solution of potassium hydroxide (KOH) 34 joins the recycle loop to maintain the anolyte pH and process potassium balance.
  • KOH potassium hydroxide
  • the anolyte may include, for example, a solution of potassium sulphate (K 2 S0 4 ) and sulphuric acid (H 2 S0 4 ) and/or potassium hydrogen sulphate KHS0 4 or the analogous phosphates (H 3 P0 4 , K 3 P0 4 , K 2 HP0 4 , KH 2 P0 4 ) or potassium salts with other anodically stable anions.
  • anolyte pH and the potassium balance may be controlled through other electro-oxidation reactions, such as reactions 3 to 10 above, for example by generating chlorine by reaction 3 from an anolyte solution of potassium chloride (KCI) and hydrogen chloride (HCI) or by producing benzoquinone by reaction 7 in an emulsion with sulphuric acid.
  • KCI potassium chloride
  • HCI hydrogen chloride
  • the carbonate recycle system of Figure 3 shows an alternative manifestation of this invention that serves to lower chemical feed (e.g. KOH) and disposal (e.g. KHCO 3 ) costs while maintaining an alkaline pH in the anolyte, which is useful to protect non- noble metal anodes from corrosion. Also, by increasing the concentration of C0 2 in the cathode feed the C0 2 recycle may improve the performance of the ERC reactor, for example by raising the Faradaic efficiency and/or current density.
  • chemical feed e.g. KOH
  • disposal e.g. KHCO 3
  • the formate recycle 18 is mixed with a potassium bicarbonate solution 28, recycled from the anolyte loop then fed to the cathode in stream 12.
  • the potassium bicarbonate stream 16 is divided in 5 to a reject bicarbonate 19 and a process bicarbonate 20, which is decomposed in unit 6 to potassium carbonate, carbon dioxide and water.
  • Carbon dioxide 21 from unit 6 is mixed with fresh gas 10 and recycled to the cathode in stream 11 , while the potassium carbonate 22 is recycled to the anolyte loop via unit 2.
  • the anolyte tank 2 mixes the recycle potassium carbonate 22 with fresh potassium hydroxide 23 and anolyte bicarbonate recycle 27 to give a potassium carbonate solution which is fed to the anode in stream 24.
  • the anode reaction 15 converts water to oxygen gas plus protons and potassium carbonate to potassium bicarbonate, part of which is divided from the anode outlet stream 26 and recycled in stream 28 to the cathode feed mixer unit 8.
  • the oxygen gas 29 disengages and may be separated from the anolyte loop in units 2 or 9. Analogous to Figure 2 and Table 5, depending on the separation efficiency in unit 3 the formate steams 17,18 will contain residual bicarbonate and the bicarbonate streams 16,19,20 will have residual formate.
  • Example 1 A single-cell continuous parallel plate trickle-bed electrochemical reactor was assembled with superficial area dimensions of 0.5 m long by 0.02 m wide for both the anode and the cathode.
  • the 3D cathode contained by a 3 mm thick gasket, was a bed of pure lead wool with a fibre diameter, porosity and specific surface respectively about 0.2 mm, 80% and 3000 m 2 /m 3 , contacted with a lead plate current collector and separated from a 316 stainless steel anode by a Nafion 1 1 10 cation membrane, which was supported in by 2 layers of a 8 mesh per inch polypropylene screen held in a 3mm thick anode gasket.
  • the 3D cathode was fed with a [C0 2 gas + liquid electrolyte] mixture consisting of 100 vol% C0 2 gas at 150 Sml/minute and 2.3 ml/minute of 1 M aqueous potassium carbonate solution containing about 1 mM sodium DTPA, and which recycled into a catholyte batch volume of 230 ml.
  • the anode was fed with a recycling flow of 1 M potassium carbonate solution at 30 ml/minute via a 1.5 litre pump tank.
  • the reactor was operated at 120 kPa(abs), 295 K for 5 hours with a current of 5 A and voltage ranging from about 4.0 to 4.5 V.
  • the concentration of potassium formate in the catholyte product increased from about 0.15 M at 10 minutes to 0.3 M at 30 minutes to 0.58 M at 300 minutes, at which stage potassium bicarbonate crystals began to form in the catholyte recycle tank and to plug the 1/8 inch tubing in the catholyte loop. Virtually zero formate was detected in the anolyte.
  • a reactor was assembled as in Example 1 , but with a Fumasep FKB-130 cation membrane and a cathode 0.1 m high by 0.01 m wide consisting of 4 stacked layers of tin plated #30 stainless steel mesh with specific surface about 7000 m2/m3.
  • the reactor was fed with an anolyte of 2.5 M KOH at 40 ml/min and catholyte recycling at 40 ml/min from a 2 litre batch of initial composition [0.5 M KHC03 + 2 mM sodium DTPA], plus 90 Sml/min pure C02 gas.
  • the reactor was operated continuously for a period of 78 hours at 300 kPa(abs), 293 K at a superficial current density of 2000 A m 2 .
  • Figure 4 shows the accumulation of bicarbonate and formate in the catholyte batch over time, reaching concentrations of respectively 2.3 and 0.5 M. Near the end of this run KHCO3 began to crystallise from the catholyte and plug the process components.
  • Example 3 recounts an experimental test of the concept of concentrating formate and crystallizing bicarbonate from a recycling catholyte.
  • Figure 6 shows the change in concentrations of bicarbonate, carbonate and formate in the supernatant solution over time.
  • Figure 6 substantiates the concept illustrated by Figure 5. While Figure 5 and 6 show the concentrations of formate and bicarbonate in the liquid phase the amounts of these salts in the solid (crystalline) phase is readily found with a material balance by those skilled in the art. Experimental measurements on the solid phase from example 3 showed the concentrations of potassium bicarbonate, potassium carbonate and potassium formate respectively about 88, 7 and 5 percent by weight. The carbonate content is due to partial decomposition of bicarbonate by reaction 14.
  • the separation of bicarbonate salts from the recycling catholyte has the further advantage of replacing part of the costly potassium hydroxide feed with an alkaline recycling source of the potassium cations which are necessary to sustain the electric current driving the electrochemical reactions.

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Abstract

L'invention porte sur des procédés améliorés pour l'électroréduction de CO2 (ERC) dans des conditions alcalines par résolution des problèmes de composition de gaz d'alimentation au CO2, de consommation de réactifs, de rejet de bicarbonate et de concentration du produit formiate. Lesdits procédés de réduction électrochimique de dioxyde de carbone dans un réacteur d'électroréduction qui produit un produit catholyte, un produit anolyte et du sel de type bicarbonate comprennent une étape de séparation du sel de type bicarbonate et du produit catholyte et d'utilisation du sel de type bicarbonate récupéré pour concentrer une charge d'alimentation en dioxyde de carbone gazeux allant vers le réacteur d'électroréduction. En outre, lesdits procédés de réduction électrochimique de dioxyde de carbone dans une solution alcaline de catholyte comprennent la séparation de bicarbonates produits pendant la réduction électrochimique du catholyte, la conversion des bicarbonates séparés en carbonates et l'utilisation des carbonates provenant de l'étape précédente pour concentrer un gaz d'alimentation en dioxyde de carbone allant vers le procédé. Dans certains modes de réalisation, le procédé peut en outre comprendre le recyclage des bicarbonates vers une charge d'alimentation en catholyte.
PCT/CA2015/050206 2014-03-19 2015-03-19 Procédé d'électroréduction de co2 WO2015139136A1 (fr)

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CN112543821A (zh) * 2018-07-10 2021-03-23 塞彭公司 用于从含co2的气体生产一氧化碳和氢气的方法和系统

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