Highly Basic Solid Catalyst 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.