Valorisation of Wastewaters Coming from Olive Industry and Brewery for Furanic Compound Production

Abstract

In this work, the catalytic conversion of residual sugars into furanic compounds, such as 5-hydroxy-methylfurfural (5-HMF) and furfural, was assessed as a promising alternative for valorizing residual wastewaters. Both furanic compounds are considered platform molecules, i.e. chemicals that can serve as a substrate for the production of various other higher value-added products, and offers diverse applications. These compounds are derived from pentose and hexose sugars through dehydration reactions in acidic mediums, primarily originating from sugars present in biomass. In this work, olive milled wastewaters (OMWs) and brewery wastewaters (BWs), which derive from processes concerning olive and malt biomasses, were employed as substrates for heterogeneous catalysis using different acidic catalysts. Commercial and home-prepared catalysts like niobium pentoxide (Nb2O5), niobium phosphate (NbOPO4), and phosphated mesoporous titania have been tested for their effectiveness in catalyzing the conversion of wastewaters into furanic compounds. The study found OMWs and BWs to be rich sources of sugars suitable for conversion, with notable yields of furanic compounds achieved under specific conditions. OMWs showed a maximum 5-HMF yield of 36%, while BWs demonstrated even higher yields, reaching up to 77% for 5-HMF.The research suggests that acid solids as catalysts offer a promising way for eco-friendly and economically viable processes for wastewaters conversion into valuable furanic compounds.