CN113718272A - Method for preparing two alkalis - Google Patents

Method for preparing two alkalis Download PDF

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CN113718272A
CN113718272A CN202010391683.3A CN202010391683A CN113718272A CN 113718272 A CN113718272 A CN 113718272A CN 202010391683 A CN202010391683 A CN 202010391683A CN 113718272 A CN113718272 A CN 113718272A
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王昱飞
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    • C—CHEMISTRY; METALLURGY
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    • C25B1/14—Alkali metal compounds
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    • 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
    • C25B1/14—Alkali metal compounds
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    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
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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
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    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/30—Hydrogen technology
    • Y02E60/36—Hydrogen production from non-carbon containing sources, e.g. by water electrolysis

Abstract

The invention discloses a method for preparing two alkalis, which adopts a cation exchange membrane to divide an electrolytic cell into an anode area and a cathode area, wherein a sodium salt solution and an organic solvent in which a compound QH is dissolved are added into the anode area, the organic solvent and the sodium salt solution are not mutually soluble, a cathode electrolyte is added into the cathode area, and a direct current power supply is applied between an anode electrode and a cathode electrode; under the action of current, sodium ions in the sodium salt solution permeate the cation exchange membrane to reach the cathode region, and the compound QH releases H+And returns to the oxidized state of Q, H+Combining with anions in the sodium salt solution to generate an acid solution; when preparing soda ash, the catholyte is sodium carbonate solution, sodium bicarbonate solution or sodium bicarbonate and sodium carbonate mixed solution, and is held in the cathode regionContinuously introducing CO2(ii) a When caustic soda is prepared, the catholyte is a sodium hydroxide solution. The method can solve the problems of high energy consumption, high emission, high safety risk and the like in the production of the two-alkali, reduce the manufacturing cost of the two-alkali and realize the efficient recycling of the product.

Description

Method for preparing two alkalis
Technical Field
The invention relates to the preparation of caustic soda or sodium carbonate, in particular to a method for preparing two alkalis by utilizing PCET reaction.
Background
Two kinds of soda, namely caustic soda and soda ash, are one of the most important products in the chemical industry, and are widely applied to the fields of buildings, chemical industry, metallurgical industry, printing and dyeing industry, leather industry, daily chemical industry and food.
At present, the industrial modes for producing soda ash at home and abroad mainly comprise a trona method, a Solvay soda method and a Hough soda method, and the Solvay soda method with the history of more than 140 years is still the most important chemical soda method in the world at present. Although various attempts have been made for more than 100 years since the competitive advantage of the soda preparation method by Sorver, no other chemical soda preparation method can compete with the soda preparation method by Sorver, but the inherent defects of low raw material utilization rate and large waste liquid discharge amount cannot be overcome. The energy consumption for producing the calcined soda is about 9.3 GJ/t-13.6 GJ/t, and the energy is mainly obtained by burning coal, which results in a large amount of CO2The discharge is realized, the utilization rate of raw materials is low, the utilization rate of raw material sodium is only about 75 percent, the utilization rate of chloride ions is 0 percent, and 10m is discharged every 1t of soda production3The waste liquid of (2). The Hou's soda production method is an improvement of famous chemists in China on the basis of the Solvay soda production method, the utilization rate of raw material sodium is improved to more than 96%, but the Hou's soda production method needs to build a synthetic ammonia plant (with higher energy consumption) or purchase raw materials from the synthetic ammonia plant, so that the cost is high, and further, the Hou's soda production method has great disadvantage in economic cost.
Caustic soda is also widely used in national economy, and is mainly prepared by an electrolytic method, namely, the caustic soda is prepared by electrolyzing salt water by adopting an ion exchange membrane method, and chlorine is generated at an anode and hydrogen is generated at a cathode in the electrolytic process. The method has the advantages of abundant raw material source, high raw material utilization rate, high caustic soda quality, and high byproduct purity (more than 99% of H purity)2And Cl2). However, the problems faced by caustic soda production are mainly:
1. the energy consumption of electrolysis is high: during the electrolysis process, the cathode and the anode can continuously generate hydrogen and chlorine, the theoretical potential of the cathode and the anode can reach 2.172V, the electrolysis voltage can reach more than 3V in the actual industrial production, the direct current power consumption reaches 2200kWh/t-NaOH, and the direct current power consumption accounts for more than 80% of the total power consumption of caustic soda production.
2. The operation risk is high: liquid chlorine and chlorine belong to dangerous chemicals which are mainly supervised for the first time, and safety accidents caused by chlorine still appear endlessly even under the strict supervision policy.
3. The environmental protection pressure is large: chlorine gas is a highly toxic gas and is the largest byproduct in the ion membrane caustic soda industry, and 0.89 ton of chlorine gas is produced as a byproduct for 1 ton of caustic soda.
CN110656343A discloses a method for preparing two-soda and high-purity gypsum by using mirabilite and limestone through PCET reaction, a compound with proton coupling electron transfer PCET reaction property is used as an electrocatalyst, and H in the traditional electrolysis method is replaced by oxidation reaction of hydrogen atoms2And the decomposition reaction of O greatly reduces the energy consumption for producing the two alkalis. However, most of the electrocatalysts with PCET reaction activity are difficult to adapt to acid-base environments at the same time, such as anthraquinone compounds, and the PCET reaction can occur under acidic conditions, and the reaction formula is as follows: q +2H +2e-＝QH2，pH<7; under the strong alkaline condition, only oxidation-reduction reaction without carrying proton can occur, and the reaction formula is as follows: q2++2e-＝Q，pH>10, thereby losing the proton transferring ability, so that the method is limited by the property of the electrocatalyst, and can only prepare NaOH solution with the concentration of 2.02mol/L, and cannot prepare high-concentration caustic soda. And most of the compounds capable of PCET are sensitive to oxygen, e.g.
Figure BDA0002486030980000021
Figure BDA0002486030980000022
And the like are sensitive to oxygen, and a compound capable of generating PCET is directly added into the electrolyte and is easily oxidized before current is conducted, so that the catalytic effect is lost. And the exchange efficiency of the cathode electrocatalyst and the anode electrocatalyst is low by adopting an extraction-back extraction method, and the method is very unstable.
Disclosure of Invention
The invention aims to provide a method for preparing two alkalis, which can solve the problems of high energy consumption, high emission, high safety risk and the like in the production of the two alkalis, reduce the manufacturing cost of the two alkalis and realize the efficient recycling of products.
The method for preparing the two alkalis adopts a cation exchange membrane to divide an electrolytic cell into an anode area and a cathode area, wherein a sodium salt solution and an organic solvent in which a compound QH is dissolved are added into the anode area, the organic solvent and the sodium salt solution are not mutually soluble, a cathode electrolyte is added into the cathode area, and a direct current power supply is applied between an anode electrode and a cathode electrode.
The compound QH is a compound capable of generating a PCET reaction, and QH is a reduction state thereof; the PCET reaction is proton coupling electron transfer, and the specific reaction chemical formula is as follows: QHn→Q+nH++ ne or Q + nH++ne→QHn。
Under the action of current, sodium ions in the sodium salt solution in the anode region permeate the cation exchange membrane to reach the cathode region, and the compound QH releases H+And returning to oxidized Q, releasing H+And the acid solution can be used as a raw material for preparing hydrochloric acid or can be used for dissolving calcium carbonate to prepare other chemical products.
When preparing sodium carbonate, the catholyte is sodium carbonate solution, sodium bicarbonate solution or sodium bicarbonate and sodium carbonate mixed solution, and CO is continuously introduced into the cathode region2(ii) a Under the action of electric current, water in the catholyte is ionized to form H+And OH-，H+Reduction to hydrogen, OH, at the cathode electrode-With introduction of CO2Combined to CO3 2-，CO3 2-And sodium ions which penetrate through the cation exchange membrane and reach the cathode region are combined to generate a sodium carbonate solution, namely, more sodium carbonate solution is prepared in the cathode region. When bicarbonate is present in the catholyte, bicarbonate and ionized OH are present-With reaction to CO3 2-The specific reaction formula is as follows: HCO3 -+OH-＝CO3 2-+H2O。
When caustic soda is prepared, the catholyte is a sodium hydroxide solution; under the action of electric current, water in the catholyte is ionized to form H+And OH-，H+Reduction to hydrogen, OH, at the cathode electrode-Combined with sodium ions which reach the cathode region through the cation exchange membrane to generate sodium hydroxide solution, namely the sodium hydroxide solution is prepared in the cathode regionA solution of sodium hydroxide.
And evaporating and crystallizing the sodium carbonate solution or the sodium hydroxide solution to obtain solid sodium carbonate or caustic soda.
Further, the compound capable of undergoing the PCET reaction is an anthraquinone-based compound, which is one of the following structural formulas:
Figure BDA0002486030980000031
Figure BDA0002486030980000041
further, the compound capable of generating the PCET reaction has a structural formula
Figure BDA0002486030980000051
Figure BDA0002486030980000052
Further, the organic solvent is at least one of dichloromethane, trichloromethane, carbon tetrachloride, 1,2 dichloroethane, 1-butyl-3-methylimidazole hexafluorophosphate ionic liquid, sulfonated kerosene, ethyl acetate and cyclohexane.
Further, in the anode region, a compound QH dissolved in an organic solvent reacts to form Q, so that a Q-rich organic solution is generated, the Q-rich organic solution and hydrogen are introduced into a hydrogenation reactor, the Q-rich organic solution and the hydrogen are reduced under the action of a catalyst to generate a QH-rich organic solution, and the QH-rich organic solution is mixed with a sodium salt solution and introduced into the anode region for electrolytic reaction.
Further, the cathode electrode is made of H+The hydrogen from the reduction is used as the source of hydrogen for the reduction to produce a QH-rich organic solution.
Further, the catalyst is palladium black, palladium carbon, foam nickel, Pd/Al2O3Or Pd/SiO2。
Further, the anode electrode is made of carbon fiber materials, and the cathode electrode is a hydrogen evolution electrode.
Further, the sodium salt solution is a sodium chloride solution, a sodium sulfate solution, a sodium formate solution or a sodium acetate solution.
Further, the cathode electrolyte is a sodium hydroxide solution with the mass fraction of 30-32%. In the electrolytic process, sodium ions in the sodium salt solution in the anode region carry part of water molecules to enter the cathode region, and the water molecules and OH ionized from the cathode region-The sodium hydroxide solution is generated by combination, more high-concentration sodium hydroxide solution is prepared on the premise of ensuring the concentration of the catholyte to be unchanged or slightly improved, and the preparation of high-concentration caustic soda is realized.
Further, CO was introduced2The volume concentration of (A) is 1-100%.
Compared with the prior art, the invention has the following beneficial effects.
1. The organic solvent dissolved with the compound QH is mixed with the sodium salt and added into the anode region, the cathode region is only added with the cathode electrolyte, and the H ionized from the cathode region is generated under the action of current+The compound Q and the hydrogen in the organic solvent are reduced outside the electrolytic cell to generate the compound QH for recycling under the action of the catalyst, so that the compound which can generate PCET reaction is prevented from contacting with an alkali solution in the cathode region, and the problem that the existing compound with PCET reaction performance cannot prepare high-concentration dibasic acid is solved.
2. The invention selects specific anthraquinone compounds with oleophylic and hydrophobic properties as the electrocatalyst of the electrolytic reaction, and dissolves the compound QH in the organic solvent which is not soluble with the sodium salt solution, and during the electrolytic reaction, the compound QH and the Q generated by oxidation are almost completely dissolved in the organic phase and do not enter the water phase, thereby avoiding the inactivation of the electrocatalyst due to oxidation. The anthraquinone compound has low sensitivity to oxygen, simple synthesis, high reaction speed and easy industrial amplification, and is suitable for preparing high-concentration sodium carbonate or caustic soda.
3. The organic solution rich in Q and hydrogen generated by the reaction of a compound QH dissolved in an organic solvent into Q are introduced into a hydrogenation reactor, and are reduced under the action of a catalyst to generate the organic solution rich in QH, and the organic solution rich in QH and a sodium salt solution are mixed and introduced into an anode region for an electrolytic reaction, so that the recycling of an electrocatalyst is realized, and the electrocatalyst does not need extraction-back extraction and has good stability.
4. The invention adopts H on the cathode electrode+The hydrogen obtained by reduction is used as a hydrogen source for reducing and generating the organic solution rich in QH, so that the recycling of byproducts is realized, the production and manufacturing cost is reduced, and the utilization rate of raw materials is improved.
5. The cathode electrode can ionize the ionized H+The hydrogen is reduced to hydrogen, and the hydrogen can be separated out from the cathode electrode of the traditional electrolytic cell for preparing caustic soda, so that when equipment is reconstructed based on the method, only the anode of the electrolytic cell is required to be reconstructed, and the reconstruction cost is reduced.
6. The method for preparing the dibasic acid and the dibasic acid has no three wastes, is environment-friendly, and realizes the resource and cyclic utilization of the byproducts.
Drawings
FIG. 1 is a schematic diagram of an electrolytic reaction for producing caustic soda according to an embodiment of the present invention;
FIG. 2 is a schematic diagram of the electrolytic reaction for preparing soda ash according to the second embodiment of the present invention.
Detailed Description
The present invention will be described in detail with reference to the accompanying drawings.
In the first embodiment, a perfluorinated sulfonic acid cation exchange membrane with a carboxylic acid layer is adopted to divide an electrolytic cell into an anode area and a cathode area, carbon fiber cloth is adopted as an anode electrode, and a nickel platinized net is adopted as a hydrogen evolution electrode as a cathode electrode.
Adopts a structural formula as
Figure BDA0002486030980000061
The compound QH of (1) was dissolved in a mixed solution of 1,2 dichloroethane and n-butanol to give an organic solution having a compound QH concentration of 0.1mol/L, and 1-butyl-3-methylimidazolium hexafluoro-fluoride having a concentration of 0.3mol/L was added to the organic solution as an anode electrocatalystThe sulfate ionic liquid serves as a supporting electrolyte. Sodium acetate solution with the concentration of 2mol/L is prepared to be used as sodium salt solution, and the sodium salt solution and the organic solution dissolved with the compound QH are circularly led into the anode area of the electrolytic cell. The cathode region was configured with 30 wt.% sodium hydroxide solution as the catholyte. And (3) connecting a direct current power supply between the anode electrode and the cathode electrode to start electrolytic reaction.
Referring to fig. 1, the Q organic solution refers to a Q-rich organic solution produced by reacting QH, a compound dissolved in an organic solvent, into Q, and the QH organic solution refers to a QH-rich organic solution produced by reduction.
Under the action of current, sodium ions in the sodium salt solution in the anode region permeate the cation exchange membrane to reach the cathode region, and the compound QH releases H+And returning to oxidized Q, releasing H+Combined with acetate in the sodium salt solution to form an acetic acid solution. Water in the catholyte of the cathode compartment is ionized H+And OH-，H+Reduction to hydrogen, OH, at the cathode electrode-And sodium ions which penetrate through the cation exchange membrane and reach the cathode region are combined to generate a sodium hydroxide solution as a product.
In the anode region, the compound QH dissolved in organic solvent reacts to form Q to generate Q-rich organic solution, the Q-rich organic solution and hydrogen are introduced into a hydrogenation reactor, hydrogen obtained by H + reduction on a cathode electrode is used as a hydrogen source, and a catalyst Pd/Al is used2O3Under the action of the catalyst, Q in the organic solution is regenerated into QH, and then the organic solution rich in QH generated by reduction and the sodium salt solution are mixed and introduced into an anode region for electrolytic reaction and are recycled. The specific reaction is as follows:
an anode region: QH-2e +2CH3COO-→Q+2CH3COOH；
A cathode region: 2H2O+2e→2OH-+H2；
A hydrogenation reaction zone: q + H2→QH；
And (3) total reaction: CH (CH)3COO-+H2O→CH3COOH+OH。
During the electrolysis, the current density is 50mA/cm-2The average electrolytic voltage is only 1.3V, the average electrolytic efficiency of the cathode region and the anode region is 96.8 percent through acid-base titration, the purity of the sodium hydroxide solution product is more than 99 percent, the direct current energy consumption for producing each ton of sodium hydroxide is 900kWh, the heat value is 10.647GJ/t-NaOH calculated by the unit heat value of each kWh of electric energy being 11.83MJ, and the currently used chlor-alkali electrolytic technology has the direct current energy consumption of 2100kWh/t NaOH, thereby greatly reducing the production energy consumption. And due to 30 wt.% of sodium hydroxide solution in the catholyte, as the electrolysis proceeds, the sodium ions in the anode region permeate the cation exchange membrane to reach the cathode region and the OH which is continuously separated from the water-The sodium hydroxide is generated by combination, so that the concentration of the cathode electrode solution is not reduced, and the preparation of the high-concentration caustic soda solution is realized.
The prior art is as follows: CN110656343A discloses a method for preparing two-soda and high-purity gypsum by utilizing a PCET reaction and using mirabilite and limestone, wherein in the embodiment 3, caustic soda and high-purity gypsum are prepared in a co-production manner, the electrolysis energy consumption of each ton of caustic soda is 800kWh, and the energy consumption of the invention is compared with that of the prior art and is shown in Table 1.
TABLE 1 energy consumption comparison of the present invention with the prior art
Figure BDA0002486030980000071
Although the energy consumption of electrolysis is lower by 100kWh compared with the prior art, the embodiment of the present invention can directly produce the sodium hydroxide solution with a concentration of more than 30 wt.% as a product. In the prior art, only 2.02mol/L sodium hydroxide solution can be produced, the mass percent concentration is reduced to about 7.4 wt.%, a large amount of steam is needed to concentrate the 2.02mol/L sodium hydroxide solution to more than 30 wt.%, and the heat value of the steam consumed by evaporation and concentration in the prior art is about 6.76GJ/t NaOH, which is 71.4% of the direct current power consumption. Therefore, in general, the invention saves the standard calorific value of 5.577GJ/tNaOH and greatly reduces the unit energy consumption for preparing sodium hydroxide products by about 34 percent.
In the second embodiment, a method for preparing soda ash adopts a cation exchange membrane to divide an electrolytic cell into an anode area and a cathode area, wherein the anode electrode adopts carbon fiber cloth, and the cathode electrode adopts a nickel platinized net as a hydrogen evolution electrode.
Adopts a structural formula as
Figure BDA0002486030980000081
The compound QH of (1) was dissolved in a mixed solution of 1,2 dichloroethane and n-butanol to give an organic solution having a compound QH concentration of 0.1mol/L, and a 1-butyl-3-methylimidazolium hexafluorosulfate ionic liquid having a concentration of 0.3mol/L was added to the organic solution as a supporting electrolyte. Sodium acetate solution with the concentration of 2mol/L is prepared to be used as sodium salt solution, and the sodium salt solution and the organic solution dissolved with the compound QH are circularly led into the anode area of the electrolytic cell. The cathode region was provided with 25 wt.% Na2CO3The solution acts as a catholyte. And (3) connecting a direct current power supply between the anode electrode and the cathode electrode to start electrolytic reaction. During the reaction, the catholyte is introduced with CO2An absorption tower for absorbing 30% CO by volume2And then circulated back to the cathode region to continue the reaction.
Referring to fig. 2, the Q organic solution refers to a Q-rich organic solution generated by reacting QH, a compound dissolved in an organic solvent, into Q, and the QH organic solution refers to a QH-rich organic solution generated by reduction.
Under the action of current, sodium ions in the sodium salt solution in the anode region permeate the cation exchange membrane to reach the cathode region, and the compound QH releases H+And returning to oxidized Q, releasing H+Combined with acetate in the sodium salt solution to form an acetic acid solution. Water in the catholyte of the cathode compartment is ionized H+And OH-，H+Reduction to hydrogen, OH, at the cathode electrode-With introduction of CO2Combined to CO3 2-，CO3 2-And sodium ions which reach the cathode region through the cation exchange membrane-The combination produces a sodium carbonate solution as the product.
The method comprises the steps of introducing a Q-rich organic solution and hydrogen generated by reacting a compound QH dissolved in an organic solvent into Q into a hydrogenation reactor, adopting hydrogen obtained by H + reduction on a cathode electrode as a hydrogen source for reducing the compound Q, regenerating QH from Q in the organic solution under the action of a catalyst palladium black, mixing the QH-rich organic solution generated by reduction with a sodium salt solution, introducing the mixture into an anode region for electrolytic reaction, and recycling the mixture. The specific reaction is as follows:
an anode region: QH-2e +2CH3COO-→Q+2CH3COOH；
A cathode region: 2H2O+2e+CO2→CO3 2-+H2；
A hydrogenation reaction zone: q + H2→QH；
And (3) total reaction: 2CH3COO-+2H2O+CO2→2CH3COOH+CO3 2-；
During the electrolysis, the current density is 20mA/cm-2The average electrolytic voltage is only 0.9V, the average electrolytic efficiency of the cathode region and the anode region is 95 percent through acid-base titration, and the purity of the sodium carbonate solution is more than 99 percent. The direct current power consumption per ton of sodium carbonate is about 480kWh, and the heat value is about 5.68GJ/t-Na calculated by the unit heat value of electric energy per kWh of 11.83MJ2CO3The energy consumption is far lower than that of the existing soda ash production by 13-15 GJ/t-Na2CO3。
In the third embodiment, a method for preparing soda ash adopts a cation exchange membrane to divide an electrolytic cell into an anode area and a cathode area, wherein the anode electrode adopts carbon fiber cloth, and the cathode electrode adopts a nickel platinized net as a hydrogen evolution electrode.
Adopts a structural formula as
Figure BDA0002486030980000091
The compound QH of (1) was dissolved in a mixed solution of 1,2 dichloroethane and n-butanol to give an organic solution having a compound QH concentration of 0.1mol/L, and a 1-butyl-3-methylimidazolium hexafluorosulfate ionic liquid having a concentration of 0.3mol/L was added to the organic solution as a supporting electrolyte. Sodium acetate solution with the concentration of 2mol/L is prepared to be used as sodium salt solution, and the sodium salt solution and the organic solution dissolved with the compound QH are circularly led into the anode area of the electrolytic cell. Cathode region arrangement25 wt.% of Na2CO3The solution acts as a catholyte. And (3) connecting a direct current power supply between the anode electrode and the cathode electrode to start electrolytic reaction. During the reaction, the catholyte is introduced with CO2An absorption tower for absorbing 30% CO by volume2And then circulated back to the cathode region to continue the reaction.
Under the action of current, sodium ions in the sodium salt solution in the anode region permeate the cation exchange membrane to reach the cathode region, and the compound QH releases H+And returning to oxidized Q, releasing H+Combined with acetate in the sodium salt solution to form an acetic acid solution. Water in the catholyte of the cathode compartment is ionized H+And OH-，H+Reduction to hydrogen, OH, at the cathode electrode-With introduction of CO2Combined to CO3 2-，CO3 2-And sodium ions which reach the cathode region through the cation exchange membrane-The combination produces a sodium carbonate solution as the product.
The method comprises the steps of introducing a Q-rich organic solution and hydrogen generated by reacting a compound QH dissolved in an organic solvent into Q into a hydrogenation reactor, adopting hydrogen obtained by H + reduction on a cathode electrode as a hydrogen source for reducing the compound Q, regenerating QH from Q in the organic solution under the action of a catalyst palladium black, mixing the QH-rich organic solution generated by reduction with a sodium salt solution, introducing the mixture into an anode region for electrolytic reaction, and recycling the mixture.
During the electrolysis, the current density is 20mA/cm-2The average electrolytic voltage is 0.7V, the average electrolytic efficiency of the cathode region and the anode region is 95 percent through acid-base titration, the purity of the sodium carbonate solution is more than 99 percent, the direct current consumption energy consumption for producing each ton of sodium carbonate is about 375kWh, the heat value is about 4.44 GJ/t-Na-MJ calculated by the unit heat value of each kWh of electric energy being 11.83MJ2CO3。
In the fourth embodiment, a method for preparing soda ash adopts a cation exchange membrane to divide an electrolytic cell into an anode area and a cathode area, wherein the anode electrode adopts carbon fiber cloth, and the cathode electrode adopts a nickel platinized net as a hydrogen evolution electrode.
Adopts a structural formula as
Figure BDA0002486030980000101
The compound QH of (1) was dissolved in a mixed solution of 1,2 dichloroethane and n-butanol to give an organic solution having a compound QH concentration of 0.1mol/L, and a 1-butyl-3-methylimidazolium hexafluorosulfate ionic liquid having a concentration of 0.3mol/L was added to the organic solution as a supporting electrolyte. Sodium acetate solution with the concentration of 2mol/L is prepared to be used as sodium salt solution, and the sodium salt solution and the organic solution dissolved with the compound QH are circularly led into the anode area of the electrolytic cell. The cathode region was provided with 25 wt.% Na2CO3The solution acts as a catholyte. And (3) connecting a direct current power supply between the anode electrode and the cathode electrode to start electrolytic reaction. During the reaction, the catholyte is introduced with CO2An absorption tower for absorbing 30% CO by volume2And then circulated back to the cathode region to continue the reaction.
Under the action of current, sodium ions in the sodium salt solution in the anode region permeate the cation exchange membrane to reach the cathode region, and the compound QH releases H+And returning to oxidized Q, releasing H+Combined with acetate in the sodium salt solution to form an acetic acid solution. Water in the catholyte of the cathode compartment is ionized H+And OH-，H+Reduction to hydrogen, OH, at the cathode electrode-With introduction of CO2Combined to CO3 2-，CO3 2-And sodium ions which reach the cathode region through the cation exchange membrane-The combination produces a sodium carbonate solution as the product.
The method comprises the steps of introducing a Q-rich organic solution and hydrogen generated by reacting a compound QH dissolved in an organic solvent into Q into a hydrogenation reactor, adopting hydrogen obtained by H + reduction on a cathode electrode as a hydrogen source for reducing the compound Q, regenerating QH from Q in the organic solution under the action of a catalyst palladium black, mixing the QH-rich organic solution generated by reduction with a sodium salt solution, introducing the mixture into an anode region for electrolytic reaction, and recycling the mixture.
During the electrolysis, the current density is 20mA/cm-2The average electrolytic voltage is 0.76V, and the average electrolysis is carried out in the cathode region and the anode region by acid-base titrationThe efficiency is 95 percent, the purity of the sodium carbonate solution is more than 99 percent, the direct current power consumption for producing each ton of sodium carbonate is about 405kWh, the heat value is about 4.79GJ/t-Na calculated by the unit heat value of electric energy per kWh being 11.83MJ2CO3。
In the fifth embodiment, a method for preparing caustic soda adopts a perfluorinated sulfonic acid cation exchange membrane with a carboxylic acid layer to divide an electrolytic cell into an anode area and a cathode area, wherein the anode electrode adopts carbon fiber cloth, and the cathode electrode adopts a nickel platinized net as a hydrogen evolution electrode.
Adopts a structural formula as
Figure BDA0002486030980000111
The compound QH of (1) was used as an anode electrocatalyst, the compound QH was dissolved in a mixed solution of 1,2 dichloroethane and n-butanol to obtain an organic solution having a concentration of 0.1mol/L, and 1-butyl-3-methylimidazolium hexafluorosulfate ionic liquid having a concentration of 0.3mol/L was added to the organic solution as a supporting electrolyte. Sodium acetate solution with the concentration of 2mol/L is prepared to be used as sodium salt solution, and the sodium salt solution and the organic solution dissolved with the compound QH are circularly led into the anode area of the electrolytic cell. The cathode region was configured with 30 wt.% sodium hydroxide solution as the catholyte. And (3) connecting a direct current power supply between the anode electrode and the cathode electrode to start electrolytic reaction.
Under the action of current, sodium ions in the sodium salt solution in the anode region permeate the cation exchange membrane to reach the cathode region, and the compound QH releases H+And returning to oxidized Q, releasing H+Combined with acetate in the sodium salt solution to form an acetic acid solution. Water in the catholyte of the cathode compartment is ionized H+And OH-，H+Reduction to hydrogen, OH, at the cathode electrode-And sodium ions which penetrate through the cation exchange membrane and reach the cathode region are combined to generate a sodium hydroxide solution as a product.
Introducing organic solution rich in Q and hydrogen generated by reacting compound QH dissolved in organic solvent into a hydrogenation reactor, and reducing hydrogen obtained by H + on a cathode electrode as a hydrogen source for reducing compound Q in the presence of catalyst Pd/Al2O3Under the action of (2) adding the organic solutionThe QH is regenerated, and then the organic solution rich in QH generated by reduction and the sodium salt solution are mixed and introduced into an anode region for electrolytic reaction and are recycled.
During the electrolysis, the current density is 20mA/cm-2The average electrolytic voltage is 1.02V, the average electrolytic efficiency of the cathode region and the anode region is 95 percent through acid-base titration, the direct current consumption energy consumption for producing each ton of sodium hydroxide is only 720kWh, and the calorific value is about 8.52GJ/t-NaOH calculated by the unit calorific value of electric energy per kWh being 11.83 MJ. The direct current power consumption is 180kWh/t-NaOH lower than that in the first embodiment and about 80kWh/t-NaOH lower than that in the prior art.
In the sixth embodiment, a method for preparing caustic soda adopts a perfluorinated sulfonic acid cation exchange membrane with a carboxylic acid layer to divide an electrolytic cell into an anode area and a cathode area, wherein the anode electrode adopts carbon fiber cloth, and the cathode electrode adopts a nickel platinized net as a hydrogen evolution electrode.
Adopts a structural formula as
Figure BDA0002486030980000112
The compound QH of (1) was used as an anode electrocatalyst, the compound QH was dissolved in a mixed solution of 1,2 dichloroethane and n-butanol to obtain an organic solution having a concentration of 0.1mol/L, and 1-butyl-3-methylimidazolium hexafluorosulfate ionic liquid having a concentration of 0.3mol/L was added to the organic solution as a supporting electrolyte. Sodium acetate solution with the concentration of 2mol/L is prepared to be used as sodium salt solution, and the sodium salt solution and the organic solution dissolved with the compound QH are circularly led into the anode area of the electrolytic cell. The cathode region was configured with 30 wt.% sodium hydroxide solution as the catholyte. And (3) connecting a direct current power supply between the anode electrode and the cathode electrode to start electrolytic reaction.
Under the action of current, sodium ions in the sodium salt solution in the anode region permeate the cation exchange membrane to reach the cathode region, and the compound QH releases H+And returning to oxidized Q, releasing H+Combined with acetate in the sodium salt solution to form an acetic acid solution. Water in the catholyte of the cathode compartment is ionized H+And OH-，H+Reduction to hydrogen, OH, at the cathode electrode-And sodium ions which reach the cathode region through the cation exchange membraneThe combination produces sodium hydroxide solution as the product.
Introducing organic solution rich in Q and hydrogen generated by reacting compound QH dissolved in organic solvent into a hydrogenation reactor, and reducing hydrogen obtained by H + on a cathode electrode as a hydrogen source for reducing compound Q in the presence of catalyst Pd/Al2O3Under the action of the catalyst, Q in the organic solution is regenerated into QH, and then the organic solution rich in QH generated by reduction and the sodium salt solution are mixed and introduced into an anode region for electrolytic reaction and are recycled.
During the electrolysis, the current density is 20mA/cm-2The average electrolytic voltage is 1.29V, the average electrolytic efficiency of the cathode region and the anode region is 96 percent through acid-base titration, the direct current consumption energy consumption for producing each ton of sodium hydroxide is about 902kWh, and the calorific value is about 10.67GJ/t-NaOH calculated by the unit calorific value of electric energy per kWh being 11.83 MJ.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents and improvements made within the spirit and principle of the present invention are intended to be included within the scope of the present invention.

Claims (10)

1. A method for preparing two alkalis is characterized in that: adopting a cation exchange membrane to divide the electrolytic cell into an anode region and a cathode region, adding a sodium salt solution and an organic solvent dissolved with a compound QH into the anode region, wherein the organic solvent and the sodium salt solution are not mutually soluble, adding a cathode electrolyte into the cathode region, and applying a direct current power supply between an anode electrode and a cathode electrode;
the compound QH is a compound capable of generating a PCET reaction, and QH is a reduction state thereof;
under the action of current, sodium ions in the sodium salt solution in the anode region permeate the cation exchange membrane to reach the cathode region, and the compound QH releases H+And returning to oxidized Q, releasing H+Combining with anions in the sodium salt solution to generate an acid solution;
when preparing soda ash, the catholyte is sodium carbonate solution, sodium bicarbonate solution or sodium bicarbonate and sodium carbonate mixed solution, and is held in the cathode regionContinuously introducing CO2(ii) a Under the action of electric current, water in the catholyte is ionized to form H+And OH-，H+Reduction to hydrogen, OH, at the cathode electrode-With introduction of CO2Combined to CO3 2-，CO3 2Combining with sodium ions which penetrate through the cation exchange membrane and reach the cathode region to generate a sodium carbonate solution;
when caustic soda is prepared, the catholyte is a sodium hydroxide solution; under the action of electric current, water in the catholyte is ionized to form H+And OH-，H+Reduction to hydrogen, OH, at the cathode electrode-And combines with sodium ions which penetrate through the cation exchange membrane and reach the cathode region to generate sodium hydroxide solution.
2. The process for preparing dibasic acid as claimed in claim 1, wherein: the compound capable of generating PCET reaction is an anthraquinone compound, and the anthraquinone compound is one of the following structural formulas:
Figure FDA0002486030970000011
Figure FDA0002486030970000021
Figure FDA0002486030970000031
3. the process for obtaining dibasic acid according to claim 2, wherein: the compound capable of generating PCET reaction has a structural formula
Figure FDA0002486030970000032
4. The process for obtaining dibasic acid according to claim 1 or 2, wherein: the organic solvent is at least one of dichloromethane, trichloromethane, carbon tetrachloride, 1,2 dichloroethane, 1-butyl-3-methylimidazole hexafluorophosphate ionic liquid, sulfonated kerosene, ethyl acetate, n-butyl alcohol and cyclohexane.
5. The process for obtaining dibasic acid according to claim 1 or 2, wherein: in the anode zone, a compound QH dissolved in an organic solvent reacts to form Q, so that a Q-rich organic solution is generated, the Q-rich organic solution and hydrogen are introduced into a hydrogenation reactor, the Q-rich organic solution and the hydrogen are reduced under the action of a catalyst to generate a QH-rich organic solution, and the QH-rich organic solution is mixed with a sodium salt solution and introduced into the anode zone for electrolytic reaction.
6. The process for obtaining dibasic acid according to claim 5, wherein: the cathode electrode is coated with a solution of H+The hydrogen from the reduction is used as the source of hydrogen for the reduction to produce a QH-rich organic solution.
7. The process for obtaining dibasic acid according to claim 5, wherein: the catalyst is palladium black, palladium carbon, foam nickel, Pd/Al2O3Or Pd/SiO2。
8. The process for obtaining dibasic acid according to claim 1 or 2, wherein: the anode electrode is made of carbon fiber materials, and the cathode electrode is a hydrogen evolution electrode.
9. The process for obtaining dibasic acid according to claim 1 or 2, wherein: the sodium salt solution is a sodium chloride solution, a sodium sulfate solution, a sodium formate solution or a sodium acetate solution.
10. The process for obtaining dibasic acid according to claim 1 or 2, wherein: the catholyte is a sodium hydroxide solution with the mass fraction of 1-32%, and preferably the mass fraction of the sodium hydroxide solution is 30-32%.
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