SAPO-35 zeolite crystallized using novel structure-directing agent for catalytic conversion of levulinic acid into ethyl levulinate under non-microwave instant heating

Abstract

SAPO-35 zeolite (LEV topology) is an 8-membered ring zeolite material that offers high selectivity and activity in separation and catalysis but this microporous material can only be crystallized using hexamethyleneimine, quinuclidine and cyclohexylamine organic templates thus far. Herein, the hydrothermal synthesis and crystallization evolution of SAPO-35 using a novel N-heterocyclic organic template, namely 1-propylpyridinium hydroxide ([PPy]OH), are reported. As compared to the previous reported hexamethyleneimine-templated synthesis conditions (24 h, 200 °C), the current system requires merely 21 h to fully crystallize SAPO-35 using [PPy]OH new template. Furthermore, the current system also witnesses a different route for crystallizing SAPO-35 where dissolution of reactants (induction), nucleation, crystal growth and intrazeolite transformation from SAPO-34 to SAPO-35 are observed. The resulting SAPO-35 zeolite of high porosity and acidity is active and selective in the catalytic conversion of levulinic acid into ethyl levulinate―a biofuel additive―under non-microwave instant heating, where it shows 96.3% conversion and 100% selectivity towards ethyl levulinate after 20 min at 190 °C with high catalyst reusability. Hence, this work offers a promising route to crystallize SAPO-35 that is benign for catalytic biofuel upgrading.