Improved Catalytic Performance on Post-Treated Zeolites SAPO-18 for 1-Butene Cracking

A facile and effective post-treatment route has been systematically applied for the preparation of hierarchical zeolites SAPO-18 using oxalic acid or sodium citrate etching solution. The influence of acidic or alkaline post-treatment on the relative crystallinity, morphology, chemical composition, pore characteristics, and acidity of a series of zeolites SAPO-18 was investigated by X-ray diffraction, scanning and transmission electron microscopy, X-ray fluorescence spectroscopy, nitrogen adsorption–desorption, temperature-programmed desorption of ammonia, and solid-state magic angle spinning nuclear magnetic resonance spectroscopy experiments. Post-treatment led to an increase in mesoporosity by widening the micropores, but a decrease in the acid strength of zeolite SAPO-18 samples. The effects of mesoporosity and acidity on the catalytic cracking performance of zeolite SAPO-18 samples were studied. The hierarchical zeolite SAPO-18 sample post-treated by alkaline sodium citrate solution with suitable concentration exhibited better catalytic conversion and improved light olefin selectivity in cracking of 1-butene.