# Making Caustic Soda with Less Salt Using a Special Electrolysis Cell > This patent describes a method to make purer caustic soda and chlorine gas using a two-chamber electrolysis cell with a gas diffusion electrode by carefully controlling pressure differences. - **Patent:** US 9181624 - **Original title:** Method of electrolysis employing two-chamber ion exchange membrane electrolytic cell having gas diffusion electrode - **Owner:** Chlorine Engineers Corp - **Granted:** 2015 - **Status:** Active - **Times cited:** 7 - **Field:** chemical_manufacturing, energy, materials, industrial_processes ## What it does The patent claims a method for electrolyzing brine (saltwater) in a "two-chamber ion exchange membrane electrolytic cell" (Claim 1). This cell has an "anode chamber" and a "cathode gas chamber" separated by an "ion exchange membrane." The cathode chamber uses a "gas diffusion electrode." The core idea is "reducing a differential pressure" between the liquid pressure in the anode chamber and the gas pressure in the cathode gas chamber (Claim 1). This pressure difference is precisely controlled, for example, reduced to "2.4 kPa or less" (Claim 1) or "-21.6 kPa or more" (Claim 2), by adjusting a "sealing pot or a valve" (Claim 1). This precise pressure control helps in "decreasing a salt concentration in the caustic soda aqueous solution" (Claim 1). For example, by carefully adjusting the valve downstream of the cathode chamber, the pressure inside the cathode chamber can be increased, which reduces the pressure difference across the membrane, leading to purer caustic soda. ## What it does NOT cover - Electrolysis methods that do not use a "two-chamber ion exchange membrane electrolytic cell." - Electrolysis cells that do not employ a "gas diffusion electrode" as the cathode. - Methods that do not involve reducing the differential pressure between the anode liquid and cathode gas. - Methods where the differential pressure is not controlled to be "2.4 kPa or less" or "-21.6 kPa or more." - Electrolysis processes for producing chemicals other than chlorine gas and caustic soda. ## The clever bit The novelty lies in precisely managing the pressure difference across the ion exchange membrane in a two-chamber cell with a gas diffusion electrode. By reducing this "differential pressure" to specific narrow ranges (e.g., 2.4 kPa or less), the method significantly lowers the unwanted salt concentration in the produced caustic soda solution. ## Real-world examples 1. Chlor-alkali plants 2. Manufacturing of PVC (polyvinyl chloride) 3. Water treatment facilities 4. Pulp and paper production 5. Textile bleaching ## Why it matters Caustic soda (sodium hydroxide) and chlorine gas are fundamental chemicals used in countless industries, from making paper and plastics to purifying water. Producing these chemicals with lower salt impurities, as described in this patent, means the final products are cleaner and more valuable. This improved purity can reduce downstream processing costs and enhance the quality of products made using these chemicals. ## Frequently asked questions ### What does Making Caustic Soda with Less Salt Using a Special Electrolysis Cell cover? This patent describes a method to make purer caustic soda and chlorine gas using a two-chamber electrolysis cell with a gas diffusion electrode by carefully controlling pressure differences. ### Who owns patent US 9181624? Chlorine Engineers Corp owns this patent, granted in 2015. ### When does this patent expire? This patent is expected to expire on April 15, 2030, when the invention enters the public domain. ### What is patent US 9181624 cited by? This patent has been cited by 7 later patents that build on its ideas. ### What problem does this patent solve? Caustic soda (sodium hydroxide) and chlorine gas are fundamental chemicals used in countless industries, from making paper and plastics to purifying water. Producing these chemicals with lower salt impurities, as described in this patent, means the final products are cleaner and more valuable. This improved purity can reduce downstream processing costs and enhance the quality of products made using these chemicals. ### What does this patent NOT cover? Electrolysis methods that do not use a "two-chamber ion exchange membrane electrolytic cell." **Full plain-English explainer:** https://patentbrief.org/patent/us/9181624/method-of-electrolysis-employing-two-chamber-ion-exchange-membrane-electrolytic- **Original patent:** https://patents.google.com/patent/US9181624 --- _Source: PatentBrief — https://patentbrief.org. Patent facts are from public records; the plain-English explanation is PatentBrief's._ ## Related patents Semantically similar inventions in the PatentBrief corpus: - [How to Make Hydrogen Gas and Cupric Chloride Using an Electrolysis Cell](https://patentbrief.org/patent/us/8636880/electrolysis-cell-for-the-conversion-of-cuprous-chloride-in-hydrochloric-acid-to) — This patent describes an electrochemical cell that uses cuprous chloride in hydrochloric acid to produce hydrogen gas and cupric chloride, separated by a special membrane. - [Dome-Shaped Plates for Efficient Hydrogen Production in Electrolyzers](https://patentbrief.org/patent/us/20250027216/electrolyzer) — This patent describes an electrolyzer that uses uniquely dome-shaped plates to improve how water is split into hydrogen and oxygen, enhancing efficiency and product separation. - [How to Make Big Electrodes for Splitting Water](https://patentbrief.org/patent/us/20210123152/method-for-preparing-large-area-catalyst-electrode) — This patent describes a simple, energy-saving way to create large, efficient catalyst electrodes using a mix of iron, cobalt, and nickel compounds through an electrical plating process. - [Making Chemicals from Carbon Dioxide and Steam Using Electricity](https://patentbrief.org/patent/us/20110132770/process-for-producing-compounds-of-the-cxhyoz-type-by-reduction-of-carbon-dioxid) — This patent describes a process that uses electricity to split steam and then reacts the resulting hydrogen with carbon dioxide or carbon monoxide to create various carbon-based compounds, like fuels or plastics. - [How Fuel Cells Get Even Gas Flow with Special Layers](https://patentbrief.org/patent/us/10468695/gas-distribution-element-for-a-fuel-cell) — This patent describes a fuel cell component that uses a special two-layer design with linear channels and transverse openings to evenly spread fuel gas for better performance.