Kilogramme-scale high-purity CO ₂ production via a two-component system of solid NaHCO ₃ and borax in 50% aqueous glycerol

A sustainable two-component system for in situ generation of high-purity carbon dioxide (CO ₂ ) gas is presented. The process operates continuously at a production rate of 1 kg h ^-1 under ambient conditions (45 °C, 1 bar) using sodium bicarbonate (NaHCO ₃ ) and borax (Na ₂ B ₄ O ₇ ·10H ₂ O) in a 50% (v/v) aqueous glycerol medium. Stoichiometric analysis for a 1 kg h ^-1 CO ₂ output requires 1.91 kg h ^-1 NaHCO ₃ and 0.46 kg h ^-1 borax. Glycerol serves a dual function as solvent and chemical modulator, significantly enhancing the acidity of boric acid formed in situ from borax hydrolysis. In 50% aqueous glycerol, the system attains a pH of approximately 5.2, sufficient to protonate bicarbonate ions and promote CO ₂ liberation under mild, non-corrosive conditions. The evolved gas passes through sodium hydroxide (NaOH) scrubbers to remove trace moisture and impurities, yielding CO ₂ of >99.5% purity, confirmed by gravimetric and gas chromatographic analysis. The solid by-products, primarily sodium metaborate and sodium carbonate, are benign and easily separable, minimizing environmental impact. This glycerol-mediated borax–bicarbonate process provides a safe, portable, and energy-efficient alternative to conventional CO ₂ sources such as pressurized cylinders or acid-based generators. Its tuneable solvent chemistry not only enables scalable and sustainable CO ₂ production but also illustrates the broader potential of solvent-induced modulation of weak acid reactivity. The approach demonstrates how solvent selection can transform chemical behaviour, offering new pathways for green and adaptive reaction design in industrial and analytical applications.