Catalytic Hydrothermal Production of Platform Chemicals from Coffee Biomass Using Organic Acids as Catalysts

Abstract

Coffee cherry waste, a byproduct of coffee production, presents significant environmental challenges due to its large volume—approximately 20 million tons annually. The disposal of this waste, which includes pulp and mucilage, often leads to pollution of land and water systems, contributing to environmental degradation. Additionally, the high acidity and organic content of coffee cherry waste complicate its management, making it crucial to find sustainable solutions for its valorization and reuse in order to mitigate these ecological impacts. The purpose of this study is to investigate the efficiency and selectivity of various organic acid catalysts in the hydrothermal valorization of coffee cherry waste. The procedures were conducted using the liquid hot water (LHW) treatment for one hour with a 1:20 biomass/catalyst ratio and a 1 mm biomass particle size at 180 °C in 500 mL batch reactors modifying 10 different organic acids at 0.02 M. Concentrations of the valorized products (HMF, furfural, levulinic acid, formic acid, and sugars) were measured using HPLC-IR. Among the catalysts tested, adipic acid demonstrated the highest efficiency, with a total yield of 53.667%, showing significant selectivity towards formic acid (19.663%) and levulinic acid (11.291%). In contrast, butyric acid was the least efficient catalyst, yielding a total of 17.395% and showing minimal selectivity towards other compounds. Chloroacetic acid and benzoic acid were notable for their high selectivity towards sugars. Other catalysts, such as anthranilic acid, propanoic acid, and succinic acid, displayed moderate efficiency and selectivity, with balanced yields across various compounds. These findings highlight the importance of catalyst selection in optimizing the hydrothermal process for desired product outcomes.