Acid Gas Capture at High Temperatures Using Molten Alkali Metal Borates

Materials designed for CO₂ capture provide both an opportunity and a challenge in that industrial emissions typically contain an assortment of acid gasses, which may include SO and NO alongside CO₂. Growing pressure to reduce emissions of all acid gasses, CO₂ included, presents an opportunity for simultaneous capture and a challenge in handling the resultant products. Molten alkali metal borates embody a new class of high-temperature liquid-phase materials for carbon dioxide capture and we propose here that they can also be used to address the more general challenge of acid gas capture. We examine the melt capture performance at industrially relevant concentrations and mixtures, identifying the various reaction mechanisms and products, and propose designs for separating these products efficiently at high temperatures, so that they outperform the state-of-the-art CO₂ capture technologies in handling this opportunity challenge. We also discuss the conditions to avoid and the challenges that lie ahead for these materials in the context of emission reduction and environmental protection.