Hydrolysis and butanolysis of lignocellulosic biomass are efficient routes to produce two valuable bio-based platform chemicals, levulinic acid and n-butyl levulinate, which find increasing applications in the field of biofuels and for the synthesis of intermediates for chemical and pharmaceutical industries, food additives, surfactants, solvents and polymers. In this research, the acid-catalyzed hydrolysis of the waste residue of Cynara cardunculus L. (cardoon), remaining after seed removal for oil exploitation, was investigated. The cardoon residue was employed as-received and after a steam-explosion treatment which causes an enrichment in cellulose. The effects of the main reaction parameters, such as catalyst type and loading, reaction time, temperature and heating methodology, on the hydrolysis process were assessed. Levulinic acid molar yields up to about 50 mol % with levulinic acid concentrations of 62.1 g/L were reached. Moreover, the one-pot butanolysis of the steam-exploded cardoon with the bio-alcohol n-butanol was investigated, demonstrating the direct production of n-butyl levulinate with good yield, up to 42.5 mol %. These results demonstrate that such residual biomass represent a promising feedstock for the sustainable production of levulinic acid and n-butyl levulinate, opening the way to the complete exploitation of this crop.

Nowadays, the transformation of lignocellulosic biomass into added-value products, such as bio-based platform chemicals and fuels, is attracting great attention. In this research, the acidcatalyzed hydrolysis of waste grape pomace and Cynara Cardunculus L. (cardoon), remained after wine and oil exploitation respectively, to levulinic acid was investigated. The grape pomace residue was employed as received, whereas the cardoon one was used both as received and after the steam explosion treatment, becoming enriched in cellulose. Since waste biomasses are low value materials, this investigation was performed adopting the High Gravity approach, using biomass loadings as higher as possible in order to achieve the maximum product concentration in the hydrolyzates, while maintaining an appreciable yield. Under the optimized reaction conditions, starting from grape pomace residue, the levulinic acid yield and concentration of 49.5 mol% and 8.5 g/L were reached respectively, whereas, from pre-treated cardoon residue, levulinic acid yields and concentrations up to 53 mol% and 62 g/L were attained, highlighting cardoon as the most suitable feedstock. On this basis, one-pot alcoholysis of pre-treated cardoon in n-butanol to n-butyl levulinate was successfully performed. In summary, waste cardoon resulted a promising feedstock for the sustainable production of both levulinic acid and alkyl levulinates, paving the way towards a circular economy.

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