Valorization of Papermill Wastes for the Production of Levulinic Acid and Butyl Levulinate

The waste management policy strongly encourages the valorization of waste biomas to give strategic biochemicals, instead of their traditional combustion for energy recovery or, even worse, of their landfill disposal. In this context, the acid-catalysed hydrothermal conversion of negative-value bio-wastes into levulinic acid (LA) and butyl levulinate (BL) represents a smart exploitation widely adaptable to different kinds of waste feedstocks. Now, particular attention was devoted to the cellulose-rich powder which derives from the cutting operations occurring during the tissue paper production and represents a waste for paper mill processes. LA is obtained by acid hydrolysis of biomass cellulose fraction and was classified as one of the top-12 promising building blocks. BL has been identified as important versatile biomolecules employed for the preparation of fuel additives, polymers and flavoring formulations. In this research, this cellulose-rich feedstock was used for the production of LA in water and BL in n-butanol, adopting in both cases a dilute acid and/or inorganic salts as catalysts. The effects of the main reaction parameters on the catalytic performances to the target products were investigated and optimized. The highest LA mass yield was obtained in the presence of very diluted HCl at 180 °C, corresponding to about 45 wt%. On the other hand, under the best reaction conditions, working in n-butanol, at 190°C in the presence of diluted H2SO4, BL yield over 40 mol% respect to glucan content was reached.