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Time-dependent crystallization evolution for synthesizing SAPO34 and SAPO-20 zeolites from a very active hydrogel is followed and reported where the XRD, FTIR, TGA/DTG, SEM/EDX, N2 adsorption–desorption and TPD-NH3 techniques are used. During the crystallization process, the hydrophobic trimethylbenzylammonium cation (BTMA+) has shown its ability as an effective structure-directing and pore filling agent. The resulting pure SAPO-34 and SAPO-20 show high crystallinity, where SAPO-34 exhibits higher porosity (393 m2 g−1, 0.24 cm3 g−1) and acidity (1.20 mmol g−1) than SAPO-20 (29 m2 g−1, 0.16 cm3 g−1, 0.02 mmol g−1), and these features are highly beneficial in the microwave-assisted ethanolysis of furfuryl alcohol. SAPO-34 shows outstanding catalytic activity (100% conversion, 72.5 ± 0.3% yield of ethyl levulinate) and its performance is much superior to that of SAPO-20 and other classical catalysts thanks to its medium pore size that induces molecular sieving effect. The spent SAPO-34 catalyst has high recyclability with stable activity, making it a superior and cost-effective catalyst for various selective petrochemical reactions. [ABSTRACT FROM AUTHOR]

A detailed investigation of the hydrothermal crystallization of SAPO-34 in the presence of the novel 1-propylpyridinium hydroxide ([PrPy]OH) organic structural directing agent is presented. The synthesis conditions are systematically tuned to investigate the effects of various parameters (viz. concentrations of each reactant, crystallization time, and temperature) on the nucleation and crystallization of SAPO-34. The results show that a careful variation in each of the synthesis parameters results in the formation of competing phases such as SAPO-5, SAPO-35, and SAPO-36. Pure and fully crystalline SAPO-34 can be crystallized using a precursor hydrogel of a molar ratio of 2.0 Al: 4.7 P: 0.9 Si: 6.7 [PrPy]OH: 148 H2O at 200 °C for only 19 h, which is a shorter time than that found in previous studies. The prepared SAPO-34 is also very active in the esterification of levulinic acid and 1-propanol. By using microwave heating, 91.5% conversion with 100% selectivity toward propyl levulinate is achieved within 20 min at 190 °C. Hence, the present study may open a new insight into the optimum synthesis study of other zeolites using novel pyridinium organic moieties and the opportunity of replacing conventional harmful and non-recyclable homogeneous catalysts in levulinate biofuel synthesis. [ABSTRACT FROM AUTHOR]

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. [Display omitted] • Crystallization evolution of SAPO-35 using a novel organic template. • Different route for crystallizing SAPO-35 is observed. • The crystallization time using new template is shorter than previous ones. • The SAPO-35 catalyst is active in the production of ethyl levulinate biofuel additive. • 96.3% conversion and 100% ethyl levulinate selectivity are recorded in 20 min at 190 °C. [ABSTRACT FROM AUTHOR]