Synthesis of formic acid using anodic plasma electrolysis

Anodic plasma electrolysis, an advanced oxidation process (AOP), is an alternative method for synthesizing formic acid through the oxidation of methanol, known for producing a high amount of hydroxyl radicals (OH•). This study aims to synthesize formic acid using anodic plasma electrolysis at a high power setting of 500 W. In addition, it seeks to determine the effects of applied voltage and air injection flow rates on the formation of formic acid from methanol and ethanol feedstocks. The experimental setup involved injecting air through a cathode pipe into the anodic plasma zone in a Na2SO4 electrolyte solution. The process was conducted in a 1.2-L batch reactor, varying the voltage and air injection flow rates, using methanol and ethanol as feed materials. The highest yield of formic acid was 5.077 mmol from methanol oxidation and 7.268 mmol from ethanol oxidation after 45 minutes of reaction time. Optimal results were achieved at an applied voltage of 680 V, an air injection flow rate of 0.8 Lpm (L/min), a fixed power of 500 W, and a feed concentration of 2% v/v. The primary by-product identified was nitrate (NO−3 ), with 2.093 mmol generated from methanol oxidation and 2.281 mmol from ethanol oxidation. In addition, the morphology of the eroded stainless steel electrode revealed a mushroom-like shape with a rough and porous surface.