Synthesis of Acetylsalicylic Acid Catalysed by Food Industry Waste Ash: A Preliminary Study

Green chemistry aims to develop more sustainable and environmentally friendly chemical processes by reducing waste, minimising the use of hazardous substances, and identifying alternative catalysts and solvents. Traditional organic synthesis often relies on catalysts that are toxic, flammable, or corrosive, such as phosphoric acid, creating a need for greener alternatives. This study investigated the potential of ash derived from food industry waste as a green catalyst. Various waste materials were utilised, including onion and garlic husks, peanut skins and shells, hop and barley residues after beer production, and cocoa shells and beans. ICP-MS analysis was used to determine the content of 25 elements (Na, Mg, P, K, Ca, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Se, Mo, Cd, Pb, B, Al, S, Ga, Rb, Sr, Ba, La) in the food industry waste ash. The catalytic activity of the ash was evaluated in the synthesis of acetylsalicylic acid from salicylic acid and acetic anhydride. Reactions were carried out in the presence of 20 mg of ash by heating the reaction mixture in a water bath at 80–100 °C. Reaction yields ranged from 11% (peanut shell ash) to 78% (barley ash). In addition to barley ash, good reaction yields were also obtained with hop ash, cocoa shell ash, and cocoa bean ash. The results demonstrated that ash-derived materials successfully catalysed the reaction, suggesting that metals present in the ash may play a role in catalysis. These findings indicate that food industry waste may represent a promising and sustainable source of catalysts for organic synthesis.