Sodium Hydroxide Production with Carboxylic Acid and Sulfur Dioxide Intermediates

BACKGROUND AND SUMMARY

Sodium hydroxide is generally produced using the chlor-alkali process, which is energy intensive, requires rare metal anodes and cathodes, and produces hydrochloric acid, which has a limited market and cannot be discharged into the environment. Production of sodium hydroxide in prior art is energy intensive, CO₂emissions intensive, and expensive. Additionally, prior art production of sodium hydroxide may not be employed in CO₂removal, or may not be added to a sea for deacidification or CO₂removal, because they are energy intensive, CO₂emissions intensive, expensive, and environmentally damaging. Commercial applications of hydrochloric acid often involve employing hydrochloric acid in a reaction with a carbonate salt, which may result in the release of CO₂and may counter any CO₂emissions reduction benefit. Additionally, if hydrochloric acid is released into the environment, it will react with carbonate or bicarbonate salts present in the environment, emitting carbon dioxide and acidifying water bodies, such as the ocean. Sodium hydroxide is an essential chemical employed in a wide range of applications, which include, for example, pulp & paper production, lithium processing, soap production, rayon production, aluminum refining, to name a few. Production of sodium hydroxide in prior art is energy intensive, CO₂emissions intensive, and expensive. Reducing the energy, cost, and emissions associated with the production of sodium hydroxide would greatly benefit the economy and environment. There is a significant need for a low energy consumption, low CO₂emissions, environmentally friendly process for producing sodium hydroxide.

Production of calcium oxide, or calcium hydroxide, or cement klinker in prior art produces CO₂emissions, which may be difficult or expensive to capture. It may be highly desirable to develop a calcium oxide, or calcium hydroxide, or cement klinker production process which does not produce CO₂emissions and/or inherently produces high purity, captured CO₂.

Some embodiments of the present invention may pertain to low carbon emissions, or low energy consumption, or carbon negative production of sodium hydroxide, or sodium carbonate, or sodium bicarbonate, or sodium sulfite, or sodium bisulfite, or gypsum, or alkaline-earth sulfate, or alkali hydroxide, or alkali carbonate, or alkali bicarbonate, or alkali sulfite. Some embodiments of the present invention may enable ultra-low CO₂emissions production of sodium hydroxide with calcium sulfate as the side product. Calcium sulfate comprises a solid, is minimally soluble in water, is non-toxic, is not dangerous for the environment, and has a multi-billion metric ton per year market in gypsum wallboard, concrete aggregates, fireproofing, plaster, building materials, and other applications. Some embodiments of the present invention may be capable of scaling to greater than 1 billion ton per year CO₂emissions reduction, or carbon removal, or a combination thereof. Some embodiments of the present invention may enable highly scalable, environmentally beneficial systems and methods for ocean deacidification, which are capable of scaling to meaningfully increase ocean pH, rejuvenate marine ecosystems, and permanently sequester carbon dioxide. Additionally some embodiments may lower the required cost and energy consumption of alkali hydroxides, alkali carbonates, and alkali bicarbonates. Some embodiments may be employ equipment comprising abundant and recyclable materials.

Some embodiments of the present invention may pertain to low carbon emissions, or low energy consumption, or carbon negative production of calcium oxide, or calcium hydroxide, or calcium carbonate, or magnesium oxide, or magnesium hydroxide, or cement, or cement klinker, or Portland cement, or magnesium carbonate, or alkaline earth oxide, or alkaline earth hydroxide, or alkaline earth carbonate or any combination thereof. Some embodiments of the present invention may enable ultra-low CO₂emissions production of calcium oxide, or magnesium oxide, or cement. Some embodiments may comprise a CO₂capture process, or a CO₂air capture process, or CO₂removal process, or a CO₂conversion process, or a CO₂separation process, or a process for recovering or separating CO₂from solutions comprising carbonate, or bicarbonate, or any combination thereof. Some embodiments of the present invention may enable calcium oxide or cement production with inherent production of high purity, high pressure carbon dioxide in the nature of the process, which may reduce the cost and energy required to produce low emissions or zero emissions calcium oxide or cement. Some embodiments may be employ equipment comprising abundant and recyclable materials.

Advantages of some embodiments include lower energy consumption, lower cost, or lower CO₂emissions, CO₂emissions negative outputs, or application in carbon dioxide removal, or no strong acid products, or abundant materials, or global scalability.

BRIEF FIGURE DESCRIPTIONS

FIG. 1: Process for producing calcium oxide and captured carbon dioxide with carboxylic acid and sulfur dioxide intermediates.

FIG. 2A: Process for producing calcium oxide and weak acid derivative employing carboxylic acid and sulfur dioxide intermediates.

FIG. 2B: Process for producing calcium oxide and weak acid derivative employing carboxylic acid and sulfur dioxide intermediates.

FIG. 3A: Process for producing magnesium oxide and weak acid derivative employing carboxylic acid and sulfur dioxide intermediates.

FIG. 3B: Process for producing magnesium oxide and weak acid derivative employing carboxylic acid and sulfur dioxide intermediates.

FIG. 4A: Process for producing alkaline earth oxide and captured carbon dioxide employing carboxylic acid, alkali, and sulfur dioxide intermediates.

FIG. 4B: Process for producing alkaline earth oxide and captured carbon dioxide employing carboxylic acid, alkali, and sulfur dioxide intermediates.

FIG. 4C: Process for producing alkaline earth oxide and captured carbon dioxide employing carboxylic acid, alkali, and sulfur dioxide intermediates.

FIG. 5A: Process for producing alkaline earth oxide and weak acid derivative employing carboxylic acid, alkali, and sulfur dioxide intermediates.

FIG. 5B: Process for producing alkaline earth oxide and weak acid derivative employing carboxylic acid, alkali, and sulfur dioxide intermediates.

FIG. 5C: Process for producing alkaline earth oxide and weak acid derivative employing carboxylic acid, alkali, and sulfur dioxide intermediates.

FIG. 5D: Process for producing alkaline earth oxide and weak acid derivative employing carboxylic acid, alkali, and sulfur dioxide intermediates.

FIG. 5E: Process for producing alkaline earth oxide and weak acid derivative employing carboxylic acid, alkali, and sulfur dioxide intermediates.

FIG. 5F: Process for producing alkaline earth oxide and weak acid derivative employing carboxylic acid, alkali, and sulfur dioxide intermediates.

FIG. 6A: Process for producing alkaline earth oxide and weak acid derivative employing carboxylic acid, alkali, and sulfur dioxide intermediates.

FIG. 6B: Process for producing alkaline earth oxide and weak acid derivative employing carboxylic acid, alkali, and sulfur dioxide intermediates.

FIG. 7A: Process for producing alkaline earth oxide and weak acid derivative employing carboxylic acid, alkali, and sulfur dioxide intermediates with membrane separation of at least a portion of alkali sulfite.

FIG. 7B: Process for producing alkaline earth oxide and weak acid derivative employing carboxylic acid, alkali, and sulfur dioxide intermediates with membrane separation of at least a portion of alkali sulfite.

FIG. 8: Process for producing alkaline earth oxide and weak acid derivative employing carboxylic acid, alkali, and sulfur dioxide intermediates with membrane separation of at least a portion of alkali sulfite.

FIG. 9A: Process for producing alkali hydroxide from alkali sulfate using carboxylic acid and sulfur dioxide intermediates.

FIG. 9B: Process for producing alkali hydroxide from alkali sulfate using carboxylic acid and sulfur dioxide intermediates.

FIG. 9C: Process for producing alkali hydroxide from alkali sulfate using carboxylic acid and sulfur dioxide intermediates.

FIG. 9D: Process for producing alkali hydroxide from alkali sulfate using carboxylic acid and sulfur dioxide intermediates.

FIG. 10A: Process for producing alkali hydroxide from alkali sulfate using carboxylic acid and sulfur dioxide intermediates.

FIG. 10B: Process for producing alkali hydroxide from alkali sulfate using carboxylic acid and sulfur dioxide intermediates.

FIG. 10C: Process for producing alkali hydroxide from alkali sulfate using carboxylic acid and sulfur dioxide intermediates.

FIG. 10D: Process for producing alkali hydroxide from alkali sulfate using carboxylic acid and sulfur dioxide intermediates.

FIG. 10E: Process for producing alkali hydroxide from alkali sulfate using carboxylic acid and sulfur dioxide intermediates.

FIG. 10F: Process for producing alkali hydroxide from alkali sulfate using carboxylic acid and sulfur dioxide intermediates.

FIG. 11A: Process for producing alkali hydroxide from alkali sulfate using carboxylic acid and sulfur dioxide intermediates.

FIG. 11B: Process for producing alkali hydroxide from alkali sulfate using carboxylic acid and sulfur dioxide intermediates.

FIG. 11C: Process for producing alkali hydroxide from alkali sulfate using carboxylic acid and sulfur dioxide intermediates.

FIG. 12A: Process for producing alkali hydroxide from alkali sulfate using carboxylic acid and sulfur dioxide intermediates.

FIG. 12B: Process for producing alkali hydroxide from alkali sulfate using carboxylic acid and sulfur dioxide intermediates.

FIG. 12C: Process for producing alkali hydroxide from alkali sulfate using carboxylic acid and sulfur dioxide intermediates.

FIG. 13A: Process for producing alkali carbonate and removing or capturing or converting CO₂from alkali sulfate employing acid, such as carboxylic acid, and sulfur dioxide intermediates.

FIG. 13B: Process for producing alkali carbonate and removing or capturing or converting CO₂from alkali sulfate employing acid, such as carboxylic acid, and sulfur dioxide intermediates.

FIG. 13C: Process for producing alkali carbonate and removing or capturing or converting CO₂from alkali sulfate employing acid, such as carboxylic acid, and sulfur dioxide intermediates.

FIG. 13D: Process for producing alkali carbonate and removing or capturing or converting CO₂from alkali sulfate employing acid, such as carboxylic acid, and sulfur dioxide intermediates.

FIG. 13E: Process for producing alkali carbonate and removing or capturing or converting CO₂from alkali sulfate employing acid, such as carboxylic acid, and sulfur dioxide intermediates.

FIG. 13F: Process for producing alkali carbonate and removing or capturing or converting CO₂from alkali sulfate employing acid, such as carboxylic acid, and sulfur dioxide intermediates.

FIG. 14A: Process for producing alkali carbonate and removing or capturing or converting CO₂from alkali sulfate employing carboxylic acid and sulfur dioxide intermediates.

FIG. 14B: Process for producing alkali carbonate and removing or capturing or converting CO₂from alkali sulfate employing carboxylic acid and sulfur dioxide intermediates.

FIG. 14C: Process for producing alkali carbonate and removing or capturing or converting CO₂from alkali sulfate employing carboxylic acid and sulfur dioxide intermediates.

FIG. 15A: Process for producing alkaline earth oxide and weak acid derivative employing carboxylic acid, alkali (such as ammonia or ammonium), and sulfur dioxide intermediates.

FIG. 15B: Process for producing alkaline earth oxide and weak acid derivative employing carboxylic acid, alkali (such as ammonia or ammonium), and sulfur dioxide intermediates.

FIG. 15C: Process for producing alkaline earth oxide and weak acid derivative employing carboxylic acid, alkali (such as ammonia or ammonium), and sulfur dioxide intermediates.

FIG. 16A: Process for producing alkaline earth oxide and weak acid derivative employing carboxylic acid, alkali (such as ammonia or ammonium), and sulfur dioxide intermediates.

FIG. 16B: Process for producing alkaline earth oxide and weak acid derivative employing carboxylic acid, alkali (such as ammonia or ammonium), and sulfur dioxide intermediates.

FIG. 16C: Process for producing alkaline earth oxide and weak acid derivative employing carboxylic acid, alkali (such as ammonia or ammonium), and sulfur dioxide intermediates.

FIG. 17A: Process for producing alkaline earth oxide and weak acid derivative employing carboxylic acid, alkali (such as ammonia or ammonium), and sulfur dioxide intermediates.

FIG. 17B: Process for producing alkaline earth oxide and weak acid derivative employing carboxylic acid, alkali (such as ammonia or ammonium), and sulfur dioxide intermediates.

FIG. 17C: Process for producing alkaline earth oxide and weak acid derivative employing carboxylic acid, alkali (such as ammonia or ammonium), and sulfur dioxide intermediates.

FIG. 18: Process for producing alkaline earth oxide and weak acid derivative employing carboxylic acid, alkali (such as ammonia or ammonium), and sulfur dioxide intermediates.

FIG. 19: Process for producing alkaline earth oxide and weak acid derivative employing carboxylic acid, alkali (such as ammonia or ammonium), and sulfur dioxide intermediates.

FIG. 20A: Process for producing or recovering ammonia from ammonium sulfate

FIG. 20B: Process for producing or recovering ammonia from ammonium sulfate

FIG. 20C: Process for producing or recovering ammonia from ammonium sulfate

FIG. 21A: Process for producing or recovering ammonia from ammonium sulfate

FIG. 21B: Process for producing or recovering ammonia from ammonium sulfate

FIG. 21C: Process for producing or recovering ammonia from ammonium sulfate

FIG. 22A: Process for producing or recovering ammonia from ammonium sulfate

FIG. 22B: Process for producing or recovering ammonia from ammonium sulfate

FIG. 22C: Process for producing or recovering ammonia from ammonium sulfate

FIG. 23A: Process for producing or recovering ammonia from ammonium sulfate

FIG. 23B: Process for producing or recovering ammonia from ammonium sulfate

FIG. 23C: Process for producing or recovering ammonia from ammonium sulfate

FIG. 24: Process for thermally decomposing or calcining alkaline earth sulfite to form alkaline earth oxide and sulfur dioxide and/or absorbing sulfur dioxide employing a recirculating carrier gas to, for example, enable use of zero emissions heat and/or enable low diatomic oxygen concentrations

FIG. 25: Process for thermally decomposing or calcining alkaline earth sulfite to form alkaline earth oxide and sulfur dioxide and/or absorbing sulfur dioxide employing a recirculating carrier gas

FIG. 26A: Process for producing alkali hydroxide using carboxylic acid and sulfur dioxide intermediates from alkali chloride.

FIG. 26B: Process for producing alkali hydroxide using carboxylic acid and sulfur dioxide intermediates from alkali chloride.

FIG. 26C: Process for producing alkali hydroxide using carboxylic acid and sulfur dioxide intermediates from alkali chloride.

FIG. 26D: Process for producing alkali hydroxide using carboxylic acid and sulfur dioxide intermediates from alkali chloride.

FIG. 27: Process for producing alkali sulfate from alkali chloride and alkaline earth sulfate using ammonia and carbon dioxide intermediates

FIG. 28A: Process for producing alkali sulfate from alkali chloride and alkaline earth sulfate using ammonia and carbon dioxide intermediates

FIG. 28B: Process for producing alkali sulfate from alkali chloride and alkaline earth sulfate using ammonia and carbon dioxide intermediates

FIG. 28C: Process for producing alkali sulfate from alkali chloride and alkaline earth sulfate using ammonia and carbon dioxide intermediates

FIG. 29: Process for producing alkali sulfate and capturing CO₂employing alkali chloride and alkaline earth sulfate using ammonia and carbon dioxide intermediates

FIG. 30: Process for producing alkali sulfate, capturing CO₂, and/or producing urea employing alkali chloride and alkaline earth sulfate using ammonia and carbon dioxide

FIG. 31A: Process for producing alkali hydroxide from alkali sulfite employing acid and sulfur dioxide intermediates

FIG. 31B: Process for producing alkali hydroxide from alkali sulfite employing acid and sulfur dioxide intermediates

FIG. 31C: Process for producing alkali hydroxide from alkali sulfite employing acid and sulfur dioxide intermediates

FIG. 32A: Process for absorbing or reacting sulfur dioxide within alkali acid-anion, such as alkali carboxylate, in a manner which may minimize or reduce potential residual vapor in remaining gases.

FIG. 32B: Process for absorbing or reacting sulfur dioxide within alkali acid-anion, such as alkali carboxylate, in a manner which may minimize or reduce potential residual vapor in remaining gases.

FIG. 33: Process for producing alkali hydroxide from alkali sulfate using carboxylic acid and sulfur dioxide intermediates.

FIG. 34: Process for producing alkali hydroxide from alkali sulfate using carboxylic acid, sulfur dioxide, and carbon dioxide intermediates.

FIG. 35: Process for producing alkali hydroxide from alkali sulfate using carboxylic acid, sulfur dioxide, and carbon dioxide intermediates.

FIG. 36A: Process for producing alkali bicarbonate or carbonate from alkali sulfate using carboxylic acid and sulfur dioxide intermediates and carbon dioxide input and intermediate.

FIG. 36B: Process for producing alkali bicarbonate or carbonate from alkali sulfate using carboxylic acid and sulfur dioxide intermediates and carbon dioxide input and intermediate.

FIG. 37: Process for producing alkali hydroxide from alkali sulfate using carboxylic acid, magnesium, sulfur dioxide, and carbon dioxide intermediates.

FIG. 38: Process for producing alkali hydroxide from alkali sulfate using carboxylic acid, magnesium, sulfur dioxide, and carbon dioxide intermediates.

FIG. 39A: Process for producing alkali bicarbonate or carbonate from alkali sulfate using carboxylic acid and sulfur dioxide intermediates and carbon dioxide input and intermediate.

FIG. 39B: Process for producing alkali bicarbonate or carbonate from alkali sulfate using carboxylic acid and sulfur dioxide intermediates and carbon dioxide input and intermediate.

DETAILED DESCRIPTION
Example Chemistry
Example 1: Process for Producing Calcium Oxide or Cement or Clinker

(1) React Material comprising Calcium, or Magnesium, or Other Alkaline Earth-Weak Acid Anion with Acetic Acid, which may comprise, including, but not limited to, one or more or any combination of the following:

CaCO₃(s or aq)+2CH₃COOH(aq) custom-character Ca(CH₃COO)₂(aq)+CO₂(g)

Calcium Silicate(s)+2CH₃COOH(aq) custom-character Ca(CH₃COO)₂(aq)+Silicon Dioxide(s)

CaS(s)+2CH₃COOH(aq) custom-character Ca(CH₃COO)₂(aq)+H₂S(g)

Calcium(Weak Acid Anion)+2CH₃COOH(aq) custom-character Ca(CH₃COO)₂(aq)+Weak Acid(s, or g, or l, or aq)

Note: Residual solids or undissolved solids, such as silicon dioxide or other undissolved solids, may be separated from the liquid solution using a solid-liquid separation.

Note: CO₂(g) may comprise captured CO₂.

Note: In some embodiments, some chemicals comprising calcium may comprise a portion of magnesium. In some embodiments, for example, input chemicals or input material may comprise a mixture of calcium and magnesium.

Note: In some embodiments, acetic acid vapor and/or water vapor may be separated or recovered from CO₂(g).

Ca(CH₃COO)₂(aq)+SO₂(g or aq)+H₂O(l or aq) custom-character CaSO₃(s)+2CH₃COOH(aq) (2)

Note: CaSO₃(s) may be separated using a solid-liquid separation.

Note: In some embodiments, SO₂(g) may comprise other gases in addition to SO₂(g). In some embodiments, the remaining gases after the absorption or reaction of at least a portion of SO₂(g) may comprise a portion of acetic acid vapor. In some embodiments, the remaining gases after the absorption or reaction of at least a portion of SO₂(g) may comprise at least a portion of acetic acid vapor, which may comprise acetic acid evaporated from the products of reaction step ‘(2)’. In some embodiments, remaining gases comprising at least a portion of acetic acid vapor may be contacted with Ca(CH₃COO)₂(aq) before the reaction with SO₂(g), which may enable at least a portion of acetic acid vapor to be absorbed in the Ca(CH₃COO)₂(aq) and/or removed from the remaining gases. In some embodiments, acetic acid vapor may be removed from remaining gases using, for example, including, but not limited to, one or more or any combination of the following: alkaline earth carbonate, or alkaline earth-weak acid, or alkaline earth carbonate-water slurry, or alkaline earth oxide, or alkaline earth hydroxide, or alkaline earth hydroxide-water slurry, or alkaline earth hydroxide-water suspension, or alkaline earth hydroxide-water solution, or water, or alkali carbonate, or alkali bicarbonate, or alkali hydroxide.

Note: In some embodiments, residual aqueous magnesium sulfite may be present in the ‘2CH₃COOH(aq)’. In some embodiments, the residual aqueous magnesium sulfite may remain in the ‘2CH₃COOH(aq)’ transferred to reaction ‘(1)’ from, for example, reaction ‘(2)’. In some embodiments, at least a portion of the aqueous magnesium sulfite may remain in the ‘2CH₃COOH(aq)’ solution transferred to reaction ‘(1)’ from reaction ‘(2)’/. Additional magnesium sulfite above the solubility limits of magnesium sulfite in the solution may precipitate or co-precipitate during the reaction of Ca(CH₃COO)₂(aq) or Mg(CH₃COO)₂(aq) with SO₂(g or aq), or sulfite, or bisulfite, or any combination thereof.

Note: In some embodiments, residual aqueous magnesium sulfite may be present in the ‘2CH₃COOH(aq)’. In some embodiments, a portion of the residual aqueous magnesium sulfite may be concentrated and/or separated using, including, but not limited to, one or more, or any combination of the following: heating, or cooling, or reverse osmosis, or membrane based process, or precipitation, or electrodialysis, or forward osmosis, or any combination thereof. For example, the residual aqueous magnesium sulfite may be separated by concentrating the magnesium sulfite using reverse osmosis or nanofiltration, wherein the pore size or properties of the membrane may enable the permeation of at least a portion of the acetic acid and the rejection of at least a portion of magnesium sulfite, and/or cooling the resulting concentrated magnesium sulfite solution to produce at least a portion of a magnesium sulfite precipitate.

CaSO₃(s) custom-character CaO(s)+SO₂(g) (3)

Note: ‘(3)’ may comprise calcining CaSO₃(s), which may employ a kiln.

Note: CaSO₃(s) may be dried, or dehydrated, or both before or during ‘(3)’.

Example 2: Process for Producing Magnesium Oxide or Cement or Clinker

(1) React Material comprising Calcium, or Magnesium, or Other Alkaline Earth-Weak Acid Anion with Acetic Acid

MgCO₃(s or aq)+2CH₃COOH(aq) custom-character Mg(CH₃COO)₂(aq)+CO₂(g)

Magnesium Silicate(s)+2CH₃COOH(aq) custom-character Mg(CH₃COO)₂(aq)+Silicon Dioxide(s)

MgS(s)+2CH₃COOH(aq) custom-character Mg(CH₃COO)₂(aq)+H₂S(g)

Magnesium(Weak Acid Anion)+2CH₃COOH(aq) custom-character Mg(CH₃COO)₂(aq)+Weak Acid(s, or g, or l, or aq)

Note: Residual solids or undissolved solids, such as silicon dioxide or other undissolved solids, may be separated from the liquid solution using a solid-liquid separation.

Note: In some embodiments, 2CH₃COOH(aq) may comprise at least a portion of MgSO₃(aq), which may be referred to as residual MgSO₃(aq).

Mg(CH₃COO)₂(aq)+SO₂(g or aq)+H₂O(l or aq) custom-character MgSO₃(s)+2CH₃COOH(aq) (2)

Note: MgSO₃(s) may be separated using a solid-liquid separation.

Note: Residual MgSO₃(aq) may be present in the 2CH₃COOH(aq) solution.

MgSO₃(s) custom-character MgO(s)+SO₂(g) (3)

Note: ‘(3)’ may comprise calcining MgSO₃(s), which may employ a kiln.

Note: MgSO₃(s) may be dried, or dehydrated, or both before or during ‘(3)’.

Example 3: Process for Producing Calcium Oxide or Cement or Clinker with Alkali Intermediate

(1) React Material comprising Calcium, or Magnesium, or Other Alkaline Earth-Weak Acid Anion with Acetic Acid

CaCO₃(s or aq)+2CH₃COOH(aq) custom-character Ca(CH₃COO)₂(aq)+CO₂(g)

Calcium Silicate(s)+2CH₃COOH(aq) custom-character Ca(CH₃COO)₂(aq)+Silicon Dioxide(s)

CaS(s)+2CH₃COOH(aq) custom-character Ca(CH₃COO)₂(aq)+H₂S(g)

Calcium(Weak Acid Anion)+2CH₃COOH(aq) custom-character Ca(CH₃COO)₂(aq)+Weak Acid(s, or g, or l, or aq)

Note: Residual solids or undissolved solids, such as silicon dioxide or other undissolved solids, may be separated from the liquid solution using a solid-liquid separation.

Note: If CO₂(g) is produced, it may be desirable for said CO₂(g) to be produced at a high partial pressure CO₂(g), or purity CO₂(g), or to comprise captured CO₂(g).

Ca(CH₃COO)₂(aq)+Na₂SO₃(s or aq) custom-character 2NaCH₃COO(aq)+CaSO₃(s) (2)

Note: CaSO₃(s) may be separated using a solid-liquid separation.

Note: In some embodiments, Na₂SO₃(s or aq) may comprise a solid comprising sodium sulfite, which may be added to or dissolved in a solution comprising calcium acetate.

Note: In some embodiments, Na₂SO₃(s or aq) may comprising an aqueous solution comprising sodium sulfite and acetic acid.

2NaCH₃COO(aq)+SO₂(g or aq)+H₂O(l or aq) custom-character Na₂SO₃(aq)+2CH₃COOH(aq) (3)

Note: In some embodiments, SO₂(g) may comprise other gases in addition to SO₂(g). In some embodiments, the reaction of 2NaCH₃COO(aq)+SO₂(g) may result in at least a portion of acetic acid vapor in the remaining gases during or after the reaction. In some embodiments, NaCH₃COO(aq) entering the present step may be pre-contacted with or may absorb at least a portion of acetic acid vapor from the remaining gases. In some embodiments, the reactor or absorption column may be configured to absorb acetic acid vapor in NaCH₃COO(aq) before or while reacting NaCH₃COO(aq) with SO₂(g). In some embodiments, acetic acid vapor may be removed from remaining gases using, for example, including, but not limited to, one or more or any combination of the following: alkaline earth carbonate, or alkaline earth-weak acid, or alkaline earth carbonate-water slurry, or alkaline earth oxide, or alkaline earth

Na₂SO₃(aq)+2CH₃COOH(aq) custom-character 2CH₃COOH(aq or l)+Na₂SO₃(s) (4)

Note: CH₃COOH may be more soluble in water than Na₂SO₃. In some embodiments, Na₂SO₃may be separated or precipitated from solution by, for example, including, but not limited to, evaporation, or distillation, or crystallization, or separation systems or methods described herein, or separation systems or methods described in the art, or any combination thereof.

Note: In some embodiments, CH₃COOH and/or water may be separated from Na₂SO₃by, for example, evaporation, or distillation, or crystallization, or any combination thereof. In some embodiments, CH₃COOH may evaporate with water vapor and/or condense with water vapor, which may result in a distillate or condensate comprising CH₃COOH(aq).

Note: In some embodiments, magnesium sulfite(aq) may be present in the Na₂SO₃(aq)+2CH₃COOH(aq). In some embodiments, if present, magnesium sulfite may begin to precipitate or crystalize before Na₂SO₃. In some embodiments magnesium sulfite solid may be separated during step ‘(4)’. In some embodiments, separated magnesium sulfite may be decomposed to magnesium oxide, or decomposed separately from calcium sulfite, or decomposed together with calcium sulfite, or any combination thereof.s

Note: Na₂SO₃(s) may be separated from CH₃COOH(aq) by a solid-liquid separation, which may include, but is not limited to, filter, or centrifuge, or decanter, or separation systems or methods described herein, or separation systems or methods described in the art, or any combination thereof.

Note: In some embodiments, a feed solution comprising sodium sulfite and acetic acid may be evaporated, wherein a portion of acetic acid and water vapor evaporate and/or are condensed to form an a separated acetic acid solution, and/or the remaining solution comprises aqueous acetic acid and a higher concentration of sodium sulfite than in the concentration of sodium sulfite in the feed solution.

CaSO₃(s) custom-character CaO(s)+SO₂(g) (5)

Note: ‘(5)’ may comprise calcining CaSO₃(s), which may employ a kiln.

Note: CaSO₃(s) may be dried, or dehydrated, or both before, or during ‘(5)’.

Note: In some embodiments, it may be preferred or desired to react SO₂(g) with NaCH₃COO(aq) to form Na₂SO₃(aq), and then react Na₂SO₃with Ca(CH₃COO)₂(aq) to form CaSO₃(s) because, for example, including, but not limited to, one or more or any combination of the following potential benefits:

- In some embodiments, it may be desirable to absorb SO₂(g) in an absorption column. Precipitate formation can be problematic in an absorption column due to, for example, including, but not limited to, precipitate clogging packing material, or plates, or interfering with gas flows, or interfering with liquid flows, or forming scaling, or any combination thereof. The reaction of Ca(CH₃COO)₂(aq) with SO₂(g) may form a precipitate comprising CaSO₃(s), which may be challenging in some absorption columns or a gas absorption processes. The reaction of NaCH₃COO(aq) with SO₂(g) may, if desired, the salt may mostly remain at an aqueous or liquid phase throughout the reaction, because, for example, Na₂SO₃may be soluble in water, which may be desirable in an absorption column.
- In some embodiments, if the SO₂(g) comprises gases in addition to SO₂(g), acetic acid vapor may be present in the remaining gases during or after the reaction of SO₂(g) with an acetate salt. If SO₂(g) is contacted with NaCH₃COO(aq), which may form aqueous phase Na₂SO₃(aq) and/or acetic acid, the reactor or absorption column may be configured such that NaCH₃COO(aq) entering the reactor or absorption column absorbs or recovers at least a portion of acetic acid vapor from the remaining gases. If SO₂(g) is contacted with NaCH₃COO(aq), which may form aqueous phase Na₂SO₃(aq) and/or acetic acid, the reactor or absorption column may be configured such that NaCH₃COO(aq) entering the reactor or absorption column absorbs or recovers at least a portion of acetic acid vapor from the remaining gases before or while NaCH₃COO(aq) is substantially reacted with SO₂(g). The employing NaCH₃COO(aq) may react with residual SO₂(g) potentially present in the remaining gases, which may avoid solid formation or solid handing issues which may occur if Ca(CH₃COO)₂(aq) is reacted with residual SO₂(g).
- For example, in some embodiments in some embodiments, the ability for the reaction products to comprise aqueous or pumpable phases may enable absorption column, or absorber, or reactor, or any combination thereof designs or configurations which may facilitate the recovery of acetic acid vapor and/or may reduce the potential amount or concentration of acetic acid vapor in the remaining gases.
- For example, it may be desirable to absorb SO₂(g) in an absorption column because the SO₂(g) may be at a dilute concentration, or a low partial pressure, or may comprise a gas mixture, or to improve absorption efficiency, or to facilitate the recovery or removal of any acid vapor from remaining gases, or to facilitate the recovery or removal of acetic acid vapor from remaining gases, or prevent or minimize or reduce the concentration or partial pressure of acetic acid vapor in the remaining gases, or any combination thereof. For example, in some embodiments, the process employed to decompose calcium sulfite to calcium oxide and sulfur dioxide may form a gas mixture comprising sulfur dioxide. For example, in some embodiments, the partial pressure of sulfur dioxide in said gas mixture may be lower than 1 atm, or 0.9 atm, or 0.8 atm, or 0.7 atm, or 0.6 atm, or 0.5 atm, or 0.4 atm, or 0.3 atm, or 0.2 atm, or 0.1 atm, or 0.05 atm, or any combination thereof and/or wherein the volume percent concentration of sulfur dioxide in said gas mixture may be lower than 100%, or 90%, or 80%, or 70%, or 60%, or 50%, or 40%, or 30%, or 20%, or 10%, or 5%, or any combination thereof.
- Greater absorption rate or absorption efficiency.
- Solid-liquid separations may be easier or simpler or higher yielding. For example, in some embodiments, if the rate of precipitation is dependent on the mixing of two liquids, rather a precipitation reaction from a gas and a liquid, the formation of and/or separation of precipitates may be more controllable.

Example 4: Process for Producing Magnesium Oxide or Cement or Clinker with Alkali Intermediate

(1) React Material comprising Calcium, or Magnesium, or Other Alkaline Earth-Weak Acid Anion with Acetic Acid

MgCO₃(s or aq)+2CH₃COOH(aq) custom-character Mg(CH₃COO)₂(aq)+CO₂(g)

Magnesium Silicate(s)+2CH₃COOH(aq) custom-character Mg(CH₃COO)₂(aq)+Silicon Dioxide(s)

MgS(s)+2CH₃COOH(aq) custom-character Mg(CH₃COO)₂(aq)+H₂S(g)

Magnesium(Weak Acid Anion)+2CH₃COOH(aq) custom-character Mg(CH₃COO)₂(aq)+Weak Acid(s, or g, or l, or aq)

Note: Residual solids or undissolved solids, such as silicon dioxide or other undissolved solids, may be separated from the liquid solution using a solid-liquid separation.

Note: If CO₂(g) is produced, it may be desirable for said CO₂(g) to be produced at a high partial pressure CO₂(g), or purity CO₂(g), or to comprise captured CO₂(g).

Mg(CH₃COO)₂(aq)+Na₂SO₃(s or aq) custom-character 2NaCH₃COO(aq)+MgSO₃(s) (2)

Note: MgSO₃(s) may be separated using a solid-liquid separation.

2NaCH₃COO(aq)+SO₂(g or aq)+H₂O(l or aq) custom-character Na₂SO₃(aq)+2CH₃COOH(aq) (3)

Na₂SO₃(aq)+2CH₃COOH(aq) custom-character 2CH₃COOH(aq or l)+Na₂SO₃(s) (4)

Note: CH₃COOH may be more soluble in water than Na₂SO₃. In some embodiments, water may be removed and/or Na₂SO₃may be separated or precipitated by, for example, including, but not limited to, evaporation, or distillation, or crystallization, or separation systems or methods described herein, or separation systems or methods described in the art, or any combination thereof.

Note: In some embodiments, magnesium sulfite(aq) may be present in the Na₂SO₃(aq)+2CH₃COOH(aq). In some embodiments, if present, magnesium sulfite may precipitate or crystalize before Na₂SO₃. In some embodiments, if present, magnesium sulfite may precipitate or crystalize before Na₂SO₃, which may enable the separation of at least a portion of magnesium sulfite from Na₂SO₃.

Note: Na₂SO₃(s) may be separated from CH₃COOH(aq or l) by a solid-liquid separation, which may include, but is not limited to, filter, or centrifuge, or decanter, or separation systems or methods described herein, or separation systems or methods described in the art, or any combination thereof.

Note: In some embodiments, CH₃COOH may evaporate with water vapor and/or condense with water vapor to form a distillate or condensate comprising CH₃COOH(aq).

MgSO₃(s) custom-character MgO(s)+SO₂(g) (5)

Note: ‘(5)’ may comprise calcining CaSO₃(s), which may employ a kiln.

Note: CaSO₃(s) may be dried, or dehydrated, or both before, or during ‘(5)’.

Note: In some embodiments, it may be preferred to react SO₂(g) with NaCH₃COO(aq) to form Na₂SO₃(aq), and then react Na₂SO₃with Mg(CH₃COO)₂(aq) to form MgSO₃(s) because, for example, including, but not limited to, one or more or any combination of the following potential benefits:

- In some embodiments, it may be desirable to absorb SO₂(g) in an absorption column. Precipitate formation can be problematic in an absorption columns due to, for example, including, but not limited to, precipitate clogging packing material, or plates, or interfering with gas flows, or interfering with liquid flows, or forming scaling, or any combination thereof. The reaction of Mg(CH₃COO)₂(aq) with SO₂(g) may form a precipitate comprising MgSO₃(s), which may be problematic in some absorption columns or a gas absorption processes. The reaction of NaCH₃COO(aq) with SO₂(g) may, if desired, remain an aqueous solution or liquid solution throughout the reaction, because, for example, Na₂SO₃is soluble in water, which may be desirable in an absorption column.
- For example, it may be desirable to absorb SO₂(g) in an absorption column because the SO₂(g) may be at a dilute concentration, or a low partial pressure, or may comprise a gas mixture, or to improve absorption efficiency, or to facilitate the recovery or removal of any acid vapor from remaining gases, or any combination thereof. For example, in some embodiments, the process employed to decompose calcium sulfite to calcium oxide and sulfur dioxide may form a gas mixture comprising sulfur dioxide. For example, in some embodiments, the partial pressure of sulfur dioxide in said gas mixture may be lower than 1 atm, or 0.9 atm, or 0.8 atm, or 0.7 atm, or 0.6 atm, or 0.5 atm, or 0.4 atm, or 0.3 atm, or 0.2 atm, or 0.1 atm, or 0.05 atm, or any combination thereof and/or wherein the volume percent concentration of sulfur dioxide in said gas mixture may be lower than 100%, or 90%, or 80%, or 70%, or 60%, or 50%, or 40%, or 30%, or 20%, or 10%, or 5%, or any combination thereof.
- In some embodiments, if the SO₂(g) comprises gases in addition to SO₂(g), acetic acid vapor may be present in the remaining gases during or after the reaction of SO₂(g) with an acetate salt. If SO₂(g) is contacted with NaCH₃COO(aq), which may form aqueous phase Na₂SO₃(aq) and/or acetic acid, the reactor or absorption column may be configured such that NaCH₃COO(aq) entering the reactor or absorption column absorbs or recovers at least a portion of acetic acid vapor from the remaining gases. If SO₂(g) is contacted with NaCH₃COO(aq), which may form aqueous phase Na₂SO₃(aq) and/or acetic acid, the reactor or absorption column may be configured such that NaCH₃COO(aq) entering the reactor or absorption column absorbs or recovers at least a portion of acetic acid vapor from the remaining gases before or while NaCH₃COO(aq) is substantially reacted with SO₂(g). The employing NaCH₃COO(aq) may react with residual SO₂(g) potentially present in the remaining gases, which may avoid solid formation or solid handing issues which may occur if Ca(CH₃COO)₂(aq) is reacted with residual SO₂(g).
- Greater absorption rate or absorption efficiency.
- Solid-liquid separations may be easier or simpler or higher yielding. For example, if the rate of precipitation is dependent on the mixing of two liquids, rather than a gas and a liquid, the formation of and/or separation of precipitates may be more controlled.

Example 5: Process for Producing Calcium Oxide or Cement or Clinker with Alkali Intermediate with Recirculating Separation Process

(1) React Material comprising Calcium, or Magnesium, or Other Alkaline Earth-Weak Acid Anion with Acetic Acid

CaCO₃(s or aq)+2CH₃COOH(aq) custom-character Ca(CH₃COO)₂(aq)+CO₂(g)

Calcium Silicate(s)+2CH₃COOH(aq) custom-character Ca(CH₃COO)₂(aq)+Silicon Dioxide(s)

CaS(s)+2CH₃COOH(aq) custom-character Ca(CH₃COO)₂(aq)+H₂S(g)

Calcium(Weak Acid Anion)+2CH₃COOH(aq) custom-character Ca(CH₃COO)₂(aq)+Weak Acid(s, or g, or l, or aq)

Note: Residual solids or undissolved solids, such as silicon dioxide or other undissolved solids, may be separated from the liquid solution using a solid-liquid separation.

Ca(CH₃COO)₂(aq)+Na₂SO₃(s or aq)+CH₃COOH(aq) custom-character 2NaCH₃COO(aq)+CH₃COOH(aq)+CaSO₃(s) (2)

Note: CaSO₃(s) may be separated using a solid-liquid separation.

Note: CH₃COOH(aq) may be present due to CH₃COOH(aq) being present in the retanate solution comprising Na₂SO₃(aq) from a membrane based separation of CH₃COOH(aq) and Na₂SO₃(aq).

2NaCH₃COO(aq)+SO₂(g or aq)+H₂O(l or aq) custom-character Na₂SO₃(aq)+2CH₃COOH(aq) (3)

Na₂SO₃(aq)+2CH₃COOH(aq) custom-character 2CH₃COOH(aq) separately from Na₂SO₃(aq)+2CH₃COOH(aq) (4)

Note: A portion of CH₃COOH(aq) may be separated from Na₂SO₃(aq) using a separation process, such as a membrane based process, such as reverse osmosis. In some embodiments, CH₃COOH(aq) may have a hydration radius or molar mass sufficiently small to permeate through a membrane, while said membrane may reject Na₂SO₃(aq). In some embodiments, Na₂SO₃(aq)+2CH₃COOH(aq) may be separated into a permeate solution comprising 2CH₃COOH(aq) and a retentate solution comprising Na₂SO₃(aq)+2CH₃COOH(aq).

CaSO₃(s) custom-character CaO(s)+SO₂(g) (5)

Note: ‘(5)’ may comprise calcining CaSO₃(s), which may employ a kiln.

Note: CaSO₃(s) may be dried, or dehydrated, or both before or during ‘(5)’.

Example 6: Process for Producing Magnesium Oxide or Cement or Clinker with Alkali Intermediate with Recirculating Separation Process

(1) React Material comprising Calcium, or Magnesium, or Other Alkaline Earth-Weak Acid Anion with Acetic Acid

MgCO₃(s or aq)+2CH₃COOH(aq) custom-character Mg(CH₃COO)₂(aq)+CO₂(g)

Magnesium Silicate(s)+2CH₃COOH(aq) custom-character Mg(CH₃COO)₂(aq)+Silicon Dioxide(s)

MgS(s)+2CH₃COOH(aq) custom-character Mg(CH₃COO)₂(aq)+H₂S(g)

Magnesium(Weak Acid Anion)+2CH₃COOH(aq) custom-character Mg(CH₃COO)₂(aq)+Weak Acid(s, or g, or l, or aq)

Note: Residual solids or undissolved solids, such as silicon dioxide or other undissolved solids, may be separated from the liquid solution using a solid-liquid separation.

Mg(CH₃COO)₂(aq)+Na₂SO₃(s or aq)+CH₃COOH(aq) custom-character 2NaCH₃COO(aq)+CH₃COOH(aq)+MgSO₃(s) (2)

Note: MgSO₃(s) may be separated using a solid-liquid separation.

Note: CH₃COOH(aq) may be present due to CH₃COOH(aq) being present in the retanate solution comprising Na₂SO₃(aq) from a membrane based separation of CH₃COOH(aq) and Na₂SO₃(aq).

2NaCH₃COO(aq)+SO₂(g or aq)+H₂O(l or aq) custom-character Na₂SO₃(aq)+2CH₃COOH(aq) (3)

Na₂SO₃(aq)+2CH₃COOH(aq) custom-character 2CH₃COOH(aq) separately from Na₂SO₃(aq)+2CH₃COOH(aq) (4)

MgSO₃(s) custom-character MgO(s)+SO₂(g) (5)

Note: ‘(5)’ may comprise calcining MgSO₃(s), which may employ a kiln.

Note: MgSO₃(s) may be dried, or dehydrated, or both before or during ‘(5)’.

Example 7: Sodium Hydroxide Production from Sodium Sulfate Using Calcium Precipitation and Acid Intermediate

(1) React Material comprising Calcium, or Magnesium, or Other Alkaline Earth-Weak Acid Anion with Acetic Acid

CaCO₃(s or aq)+2CH₃COOH(aq) custom-character Ca(CH₃COO)₂(aq)+CO₂(g)+H₂O(l or aq)

Calcium Silicate(s)+2CH₃COOH(aq) custom-character Ca(CH₃COO)₂(aq)+Silicon Dioxide(s)+H₂O(l or aq)

CaS(s)+2CH₃COOH(aq) custom-character Ca(CH₃COO)₂(aq)+H₂S(g)+H₂O(l or aq)

Calcium(Weak Acid Anion)+2CH₃COOH(aq) custom-character Ca(CH₃COO)₂(aq)+Weak Acid(s, or g, or l, or aq)+H₂O(l or aq)

Note: Residual solids or undissolved solids, such as silicon dioxide or other undissolved solids, may be separated from the liquid solution using a solid-liquid separation.

Note: CO₂(g) may comprise captured CO₂.

Note: In some embodiments, acetic acid vapor and/or water vapor may be separated or recovered from CO₂(g).

Ca(CH₃COO)₂(aq)+Na₂SO₄(s or aq) custom-character 2NaCH₃COO(aq)+CaSO₄(s) (2)

Note: In some embodiments, Na₂SO₄(s) may be added directly to or dissolved in Ca(CH₃COO)₂(aq).

Note: In some embodiments, Na₂SO₄(s) may be dissolved in water or an aqueous solution to form Na₂SO₄(aq) before mixing with Ca(CH₃COO)₂(aq).

Note: In some embodiments, water may be added to the process to make up for water which may leave the process, for example, if NaOH(aq) is an output, or another aqueous solution is an output, or any combination thereof. In some embodiments, water may be added to the process by Na₂SO₄being in the form of Na₂SO₄(aq) or an aqueous solution comprising sodium sulfate, wherein at least a portion of the water in Na₂SO₄(aq) may comprise water added to the process. In some embodiments, Na₂SO₄(aq) may be provided or sourced as an aqueous solution. For example, in some embodiments, Na₂SO₄(aq) may be provided to the process in the form of Na₂SO₄(aq). In some embodiments, Na₂SO₄(aq) may be provided or sourced as a solid or Na₂SO₄(s), then dissolved in water to form Na₂SO₄(aq).

2NaCH₃COO(aq)+SO₂(g or aq)+H₂O(l or aq) custom-character Na₂SO₃(aq)+2CH₃COOH(aq) (3)

Na₂SO₃(aq)+2CH₃COOH(aq) custom-character 2CH₃COOH(aq)+Na₂SO₃(s) (4)

Na₂SO₃(s or aq)+Ca(OH)₂(s or aq) custom-character 2NaOH(aq or s)+CaSO₃(s) (5)

Note: Ca(OH)₂(s or aq) may comprise a solid-liquid suspension, such as milk of lime.

Note: CaSO₃(s) may be separated using a solid-liquid separation.

CaSO₃(s) custom-character CaO(s)+SO₂(g) (6)

Note: ‘(6)’ may comprise calcining CaSO₃(s), which may employ a kiln.

Note: CaSO₃(s) may be dried, or dehydrated, or both before or during ‘(6)’.

CaO(s)+Water(g or l or aq) custom-character Ca(OH)₂(s or aq) (7)

Note: In some embodiments, CaO(s) may be employed to remove water vapor or facilitated drying of CaSO₃(s) before or during decomposition of CaSO₃(s) to CaO(s).

Note: In some embodiments, calcium oxide may be reacted directly with an aqueous solution comprising sodium sulfite to produce calcium sulfite and sodium hydroxide. In some embodiments, calcium oxide may be reacted directly with an aqueous solution comprising sodium sulfite to produce calcium sulfite and sodium hydroxide, which may comprise combining step ‘(5)‘ and step’(7)’.

Note: In some embodiments, calcium oxide may be reacted with water to produce an aqueous solution, or solid-liquid suspension, or milk of lime, or solid, or any combination thereof comprising calcium hydroxide.

2NaOH(aq or s) custom-character 2NaOH(aq or s)+Water (8)

Note: In some embodiments, NaOH(aq) may be concentrated into an aqueous solution comprising a greater mass percent concentration of NaOH.

Note: In some embodiments, water may be removed and/or NaOH may be separated or precipitated by, for example, including, but not limited to, evaporation, or distillation, or crystallization, or separation systems or methods described herein, or separation systems or methods described in the art, or any combination thereof.

Note: In some embodiments, it may be desirable for NaOH to comprise a concentrated aqueous solution.

Example 8: Sodium Hydroxide Production from Sodium Sulfate Using Alkaline-Earth Precipitation and Acid Intermediate

(1) React Material comprising Calcium, or Magnesium, or Other Alkaline Earth-Weak Acid Anion with Acetic Acid

MgCO₃(s or aq)+2CH₃COOH(aq) custom-character Mg(CH₃COO)₂(aq)+CO₂(g)

Magnesium Silicate(s)+2CH₃COOH(aq) custom-character Mg(CH₃COO)₂(aq)+Silicon Dioxide(s)

MgS(s)+2CH₃COOH(aq) custom-character Mg(CH₃COO)₂(aq)+H₂S(g)

Magnesium(Weak Acid Anion)+2CH₃COOH(aq) custom-character Mg(CH₃COO)₂(aq)+Weak Acid(s, or g, or l, or aq)

Note: Residual solids or undissolved solids, such as silicon dioxide or other undissolved solids, may be separated from the liquid solution using a solid-liquid separation.

Mg(CH₃COO)₂(aq)+Na₂SO₄(aq) custom-character 2NaCH₃COO(aq)+MgSO₄(s or aq) (2)

2NaCH₃COO(aq)+SO₂(g or aq)+H₂O(l or aq) custom-character Na₂SO₃(aq)+2CH₃COOH(aq) (3)

Na₂SO₃(aq)+2CH₃COOH(aq) custom-character 2CH₃COOH(aq)+Na₂SO₃(s) (4)

Na₂SO₃(s or aq)+Mg(OH)₂(s or aq) custom-character 2NaOH(aq or s)+MgSO₃(s) (5)

Note: Mg(OH)₂(s or aq) may comprise a solid-liquid suspension, such as milk of lime.

Note: MgSO₃(s) may be separated using a solid-liquid separation.

MgSO₃(s) custom-character MgO(s)+SO₂(g) (6)

Note: ‘(6)’ may comprise calcining MgSO₃(s), which may employ a kiln.

Note: MgSO₃(s) may be dried, or dehydrated, or both before or during ‘(6)’.

MgO(s)+Water(g or l or aq) custom-character Mg(OH)₂(s or aq) (7)

Note: MgO(s) may be employed to remove water vapor or facilitated drying of MgSO₃(s) before or during decomposition of MgSO₃(s) to MgO(s).

2NaOH(aq or s) custom-character 2NaOH(s)+Water (8)

Note: In some embodiments, it may be desirable for NaOH to comprise a concentrated aqueous solution.

Example 9: Sodium Hydroxide Production from Sodium Sulfate Using Calcium Precipitation and Acid Intermediate

(1) React Material comprising Calcium, or Magnesium, or Other Alkaline Earth-Weak Acid Anion with Acetic Acid

CaCO₃(s or aq)+2CH₃COOH(aq) custom-character Ca(CH₃COO)₂(aq)+CO₂(g)

Calcium Silicate(s)+2CH₃COOH(aq) custom-character Ca(CH₃COO)₂(aq)+Silicon Dioxide(s)

CaS(s)+2CH₃COOH(aq) custom-character Ca(CH₃COO)₂(aq)+H₂S(g)

Calcium(Weak Acid Anion)+2CH₃COOH(aq) custom-character Ca(CH₃COO)₂(aq)+Weak Acid(s, or g, or l, or aq)

Note: Residual solids or undissolved solids, such as silicon dioxide or other undissolved solids, may be separated from the liquid solution using a solid-liquid separation.

Ca(CH₃COO)₂(aq)+Na₂SO₄(aq) custom-character 2NaCH₃COO(aq)+CaSO₄(s) (2)

2NaCH₃COO(aq)+SO₂(g or aq)+H₂O(l or aq) custom-character Na₂SO₃(aq)+2CH₃COOH(aq) (3)

Na₂SO₃(aq)+2CH₃COOH(aq) custom-character 2CH₃COOH(aq)+Na₂SO₃(s) (4)

Na₂SO₃(s or aq)+Mg(OH)₂(s or aq) custom-character 2NaOH(aq or s)+MgSO₃(s or aq) (5)

Note: Mg(OH)₂(s or aq) may comprise a solid-liquid suspension, such as milk of lime.

Note: MgSO₃(s) may be separated using a solid-liquid separation.

MgSO₃(s) custom-character MgO(s)+SO₂(g) (6)

Note: ‘(6)’ may comprise calcining MgSO₃(s), which may employ a kiln.

Note: MgSO₃(s) may be dried, or dehydrated, or both before or during ‘(6)’.

MgO(s)+Water(g or l or aq) custom-character Mg(OH)₂(s or aq) (7)

Note: MgO(s) may be employed to remove water vapor or facilitated drying of MgSO₃(s) before or during decomposition of MgSO₃(s) to MgO(s).

2NaOH(aq or s) custom-character 2NaOH(s)+Water (8)

2NaOH(aq) custom-character 2NaOH(aq—more concentrated)+Water

Note: In some embodiments, it may be desirable for NaOH to comprise a concentrated aqueous solution.

Note: Residual MgSO₃(aq) may be present or dissolved in the solution comprising NaOH(aq). In some embodiments, during the concentrating of NaOH(aq) or removal of at least a portion of water from the NaOH(aq), at least a portion of the residual MgSO₃may precipitate or may be separated or recovered. For example, in some embodiments, MgSO₃(aq) may be less soluble in water than NaOH(aq). Separated or recovered MgSO₃may be transferred, for example, to step ‘(6)’.

Example 10: Sodium Carbonate Production from Sodium Sulfate Using Alkaline-Earth Precipitation and Acid Intermediate