SAPO-34 crystallized using novel pyridinium template as highly active catalyst for synthesis of ethyl levulinate biofuel

Abstract

Silicoaluminophosphate Number 34 (SAPO-34) crystallized using novel N-heterocyclic organic template—1-propylpyridinium hydroxide ([PPy]OH)—as an excellent catalyst for the production of ethyl levulinate biofuel is reported. First, the time-dependent crystallization study of SAPO-34 using various spectroscopy, microscopy and analytical techniques is performed and it reveals that the precursor undergoes several important crystallization steps, namely dissolution of reactants (induction), nucleation and crystal growth of SAPO-34, before it transforms into a more metastable SAPO-36 crystalline phase. The resulting SAPO-34 solid (Si0.198Al0.475P0.327O2) exhibits high porosity (SBET = 673 m2/g, VTot = 0.27 cm3/g) and high Si content (Si/(Si + Al + P) = 0.198) which contribute to high surface acidity (2.52 mmol/g) as confirmed by the NH3-TPD analysis. The SAPO-34 catalyst shows 93.4% conversion to ethyl levulinate via esterification of levulinic acid with ethanol just within 20 min at 190 °C under non-microwave instant heating, which is considered very fast as compared to other systems. In addition, high catalyst recyclability is observed even after fifth cycle of reaction, thus offering another promising pathway for crystallizing zeolites using this new class of template that are beneficial for catalytic biofuel upgrading process.