BIOFUELS FROM WASTE BIOMASS: A CASCADE STRATEGY FOR THE SUSTAINABLE PRODUCTION OF 2-METHYL-TETRAHYDROFURAN AND 2-BUTANOL

2-methyltetrahydrofuran and 2-butanol are two very promising biofuels: in this work, a cascade strategy for their synthesis has been investigated through hydrolysis and hydrogenation reactions starting from waste biomass. The exhausted cellulose powder, an abundant industrial by-product of the paper manufacture, was employed as feedstock for the production of levulinic acid in aqueous medium under sustainable reaction conditions, adopting microwave irradiation, dilute HCl as catalyst and high biomass/water weight ratio. The highest levulinic acid yield, 38 wt% calculated respect to the starting biomass, was ascertained, and then the obtained raw hydrolyzate was employed as substrate for the synthesis of the two targeted biofuels. The reaction was carried out in the presence of 5 wt% Ru/C and the effect of several reaction parameters, such as the amount and properties of the acid co-catalyst (niobium phosphate and HY zeolite), temperature, H2 pressure and the presence of 10 wt% Re/C, was investigated. The selectivity of the reaction strongly depends on the presence of rhenium and on the type of co-catalyst. In fact, niobium phosphate preferentially promoted the 2-methyltetrahydrofuran synthesis, leading to a yield of 21.3 mol%, calculated respect to initial moles of levulinic acid in the raw hydrolyzate, whereas HY zeolite resulted to be more active in the hydrogenation/decarboxylation reaction to 2-butanol, which was obtained with yield of 65.1 mol%, calculated respect to initial moles of levulinic acid in the raw hydrolyzate.