Effects of Synthesis Variables on SAPO-34 Crystallization Templated Using Pyridinium Supramolecule and Its Catalytic Activity in Microwave Esterification Synthesis of Propyl Levulinate

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 degrees 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 degrees 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.

Automated summary

A detailed study on the hydrothermal crystallization of SAPO-34 using 1-propylpyridinium hydroxide ([PrPy]OH) as a structural directing agent was conducted. The effects of different synthesis parameters on the nucleation and crystallization of SAPO-34 were systematically investigated. It was found that by carefully adjusting the parameters, pure and fully crystalline SAPO-34 could be synthesized in a shorter time compared to previous studies. The prepared SAPO-34 also exhibited high activity in esterification reactions. By using microwave heating, a conversion rate of 91.5% with 100% selectivity towards propyl levulinate was achieved within 20 minutes.