A green approach for the valorisation of Arundo donax L. and paper mill waste to produce the advanced biofuel n-Butyl Levulinate

The continue depletion of fossil sources and their environmental impact represent one of the main problems of this century. Therefore, a lot of studies have been recently performed in order to produce sustainable advanced biofuels. These components are directly obtained from not edible lignocellulosic biomasses and can totally or partially replace fossil fuel. In this work, the feasible production of the advanced biofuel n-Butyl Levulinate (BL) from an herbaceous lignocellulosic biomass and an industrial paper mill waste has been investigated and optimized. Alkyl levulinates can be produced from cellulosic fraction of biomasses. Up to now, several studies have been focused on the possible production of these compounds through a two-step process: a preliminary acid hydrolysis of the biomass to levulinic acid, followed by the purification of levulinic acid and its esterification to the target molecule. This strategy is obviously limited by the high cost connected with the overall process. By contrast, the one-pot alcoholysis of raw biomasses directly to the target product represents an innovative easier and cheaper approach. Starting form two different kinds of raw biomasses (Arundo donax L. and industrial paper mill waste), the direct acid-catalysed alcoholysis to n-butyl levulinate has been studied, employing n-butanol as solvent and H2SO4 as homogeneous catalyst (0.6-1.2 wt%). With both the considered biomasses, BL yields around 35 mol% have been achieved with high loading of feedstock between 14 and 20 wt%. Furthermore, the feasibility of our process has been tested, employing both microwave and traditional heating system, reaching the BL molar yield of 38 mol% with the high biomass loading of 20 wt% starting from A. donax L. Finally, the BL yield of 33 mol% was achieved with the extremely low catalyst loading of 0.6 wt% working with biomass loading up to 20 wt% of A. donax L., at 200°C for 180 minutes employing traditional heating. This obtained result is very promising because the employed reaction parameters, in particular the very low acid concentration, make our process promising and feasible especially from an industrial point of view.