Molten Salt Chemical Looping Process for Efficient Chlorine Production from HCl

Background

Hydrogen chloride (HCl) is a waste product in several industrial processes at massive scale, such as in the preparation of isocyanates which are crucial to many industries. One way to repurpose HCl waste is to upcycle it into chlorine (Cl₂), a valuable starting material used in industrial chemistry. Current methods of converting HCl to Cl₂ include the Deacon process, an equilibrium reaction that consists of the aerobic oxidation of HCl to Cl₂ and water. A disadvantage to all single-stage Deacon Process concepts is the expensive workup (i.e. separation of Cl₂ from other products in the equilibrium mixture). A more efficient continuous process involves molten salt-based chemical looping with three interconnected reactors containing reactive salts.

Description

Researchers at the University of California, Santa Barbara have realized continuous production of Cl₂ from HCl with a three-reactor molten salt chemical looping system. This three-stage process consists of (I) the oxidation of CuCl, (II) the chlorination of Cu₂OCl₂, and (III) thermal decomposition of CuCl₂. The most essential component of this technology is the reactor system comprising three inter-connected bubble lift columns that are placed in a sand bath to provide uniform heating. The system’s relatively-low KCl concentration allows for a high space-time yield, as well as relatively low temperature differences between the reactors. Additionally, this technology can be operated with notably low energy consumption. The Cl₂ produced can be used to manufacture other commercially valuable products and simultaneously curtail the emissions of waste HCl.

Advantages

• Upcycles a common waste product
• More efficient Cl₂ workup compared to current HCl conversion technologies
• Low energy consumption

Applications

• Large-scale industrial chemistry

Patent Status