Thorough investigation of varying template combinations on SAPO-34 synthesis, catalytic activity and stability in the methanol conversion to light olefin

Abstract

Crystals of SAPO-34 molecular sieves were synthesized under hydrothermal conditions using tetraethylammonium hydroxide, morpholine and a mixture of them as structure-directing agents. The properties of the catalysts were characterized using XRD, SEM, BET, ICP, FT-IR, ²⁹Si MAS NMR and NH₃-TPD. Characterization studies showed that using a mixed template lead to a reduction in particle size and an increase in external surface area. The catalytic performance of the synthesized catalysts was tested in MTO reactions with different time-on-stream. All the samples showed high activity and selectivity to light olefins at the initial stage of the reaction. The maximum yield of ethylene, propylene and butene was determined to be 12.57, 13.45 and 2.21 wt%, respectively. The catalyst produced by the tetraethylammonium hydroxide/morpholine ratio of 1 : 1 exhibited the longest catalyst lifetime.