Highly basic solid catalysts obtained by spray drying of a NaAlO2 and boehmite suspension for the upgrading of glycerol to acetins†
In here, we present the low-cost production of NaAlO2–Al2O3 catalysts, which exhibit high activity in the transesterification of methyl acetate with glycerol to obtain acetins. The catalyst preparation procedure is based on the spray drying of a colloidal boehmite suspension, supplemented with a sodium aluminate (NaAlO2) solution using a pilot scale spray drier. Upon subsequent calcination, we obtain spherical micro particles presenting a homogeneous dispersion of sodium aluminate and featuring high basicity. The NaAlO2 loading has a marked impact on the basicity and textural properties of the final materials. These solids are found to be efficient heterogeneous base catalysts for the upgrading of glycerol (which is essentially a waste) to glycerol acetins (which are important bio-based fuel additives). With 100 mg of the catalyst loaded with 20 wt% of NaAlO2, a conversion of 96% is obtained after 4 h of reaction at 60 °C (10 mmol of glycerol + 100 mmol of methyl acetate). Importantly, the selectivity for triacetin is as high as 20% (the rest being 50% of diacetin and 30% of monoacetin). The catalysts act strictly in a heterogeneous way and are recyclable upon calcination.