SAPO-34 Catalyst: Synthesis Optimization by Template Alteration and In Situ Coke Evolution Analysis in Methanol Conversion to Light Olefins

The template's role in the physicochemical properties of SAPO-34 was investigated using the four most popular templates (tetraethylammonium hydroxide (TEAOH), morpholine (MOR), triethylamine (TEA), and diethylamine (DEA)) in both single- and mixed-template methods to reduce the consumption of costly TEAOH. Catalyst activity in methanol conversion to light olefins was examined at 425 °C and WHSV of 1 gMeOH gCat–1 h–1. The TEA-based sample proved to be a good substitute for TEAOH in single template SAPO, and both TEAOH/DEA and TEAOH/TEA-based samples were successfully produced with the sole existence of the SAPO-34 phase and exhibited acceptable performance. Possessing a high external surface area (macro and mesopores) was recognized to be the dominant parameter affecting the catalyst's lifetime while having the optimum acidity and the small particle size played minor roles. In-situ measurement of coke formation over SAPO-34 was also conducted in a thermogravimetric reactor and led to the proposal of the coke formation mechanism, which was confirmed by 13C NMR spectroscopy and gas chromatography–mass spectrometry techniques.