Method for preparing two alkalis

Abstract

The invention discloses a method for preparing two alkalis, an electrolytic cell is divided into an anode area and a cathode area by a cation exchange membrane, a sodium salt solution and an organic solvent dissolved with a compound QH are added into the anode area, the organic solvent and the sodium salt solution are not dissolved mutually, a cathode electrolyte is added into the cathode area, a direct-current power supply is applied between the anode electrode and the cathode electrode; under the action of current, sodium ions in the sodium salt solution penetrate through the cation exchange membrane to reach the cathode area, the compound QH releases H < + > and recovers to Q in an oxidation state, and H < + > is combined with anions in the sodium salt solution to generate an acid solution; when sodium carbonate is prepared, the cathode electrolyte is a sodium carbonate solution, a sodium bicarbonate solution or a mixed solution of sodium bicarbonate and sodium carbonate, and CO2 is continuously introduced into the cathode area; when caustic soda is prepared, the cathode electrolyte is a sodium hydroxide solution. The method can solve the problems of high energy consumption, high emission, high safety risk and the like in two-alkali production, reduces the manufacturing cost of the two-alkali, and realizes efficient resource utilization of products.

Description

technical field [0001] The invention relates to the preparation of caustic soda or soda ash, in particular to a method for preparing the two alkalis through PCET reaction. Background technique [0002] The two alkalis, caustic soda and soda ash, are one of the most important products in the chemical industry, and are widely used in construction, chemical industry, metallurgical industry, printing and dyeing industry, leather industry, daily chemical industry and food industry. [0003] At present, the industrial methods of producing soda ash at home and abroad mainly include the trona method, the Solvay soda method, and the Hou's soda method, and the Solvay soda method with a history of more than 140 years is still the most important chemical method in the world today. alkaline method. Since the Solvay soda production has taken the competitive advantage for more than 100 years, although people have made many attempts, there is no other chemical soda production method that c...

AI Technical Summary

Problems solved by technology

[0005] 1. High energy consumption for electrolysis: During the electrolysis process, the cathode and anode will continuously generate hydrogen and chlorine gas, and its theoretical potential is as high as 2.172V. In actual industrial production, the electrolysis voltage is as high as 3V or more, and the DC power consumption reaches 2200kWh / t-NaOH. Accounting for more than 80% of the total energy consumption of caustic soda production

[0006] 2. High risk of operation: liquid chlorine and chlorine gas belong to the first batch of hazardous chemicals under key supervision. Even under strict regulatory policies, safety accidents caused by chlorine gas still emerge in endlessly

[0007] 3. High pressure on environmental protection: Chlorine gas, as a highly toxic gas, is the largest by-product of the ion-exchange membrane caustic soda industry, and 0.89 tons of chlorine gas is produced by producing 1 ton of caustic soda

However, most electrocatalysts with PCET reactivity are difficult to adapt to acid and alkali environments at the same time. For example, anthraquinone compounds can undergo PCET reaction under acidic conditions. The reaction formula is: Q+2H+2e - =QH 2 , pH2+ +2e - =Q, pH>10, thereby losing the ability to transfer protons, so limited by the nature of the electrocatalyst, this method can only produce NaOH solution with a concentration of 2.02mol / L, and cannot produce high-concentration caustic soda

And among the many compounds that can undergo PCET, most of them are sensitive to oxygen, such as etc. are very sensitive to oxygen, if the compound capable of PCET is directly added to the electrolyte, it will be easily oxidized before the current is turned on, thus losing the catalytic effect

Moreover, the exchange efficiency between the cathode electrocatalyst and the anode electrocatalyst is very low and very unstable by using the "extraction-stripping" method.

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