A four‐step thermocatalytic route for converting CO ₂ into high‐purity oxalic acid

This research outlines a four‐step methodology for transforming CO 2 into high‐purity oxalic acid. CO 2 was first sequestered as KHCO 3 through its reaction with aqueous KOH, followed by hydrogenation using a supported AgPd/CNT catalyst in a batch reactor at an initial H 2 pressure of 60 bar and a temperature of 150°C. The formate yield reached 91.8% at optimum conditions. Potassium formate in the solid state was thermally coupled in the presence of KOH at 400°C under N 2 flow, yielding potassium oxalate of up to 76% yield. The final step was the selective precipitation of potassium oxalate with ferrous ions to produce FeC 2 O 4 ·2H 2 O, with approximately 99% recovery efficiency, and then ferrous oxalate was acidified with HCl to get crystalline oxalic acid (H 2 C 2 O 4 ·2H 2 O) with a yield of about 85% with a product purity of 99%. After integrating all four steps, the overall yield of oxalic acid from CO 2 was about 57%.