Experimental study on coking, deactivation, and regeneration of binderless 5A zeolite during 1-hexene adsorption

Abstract

Coking, deactivation, and regeneration of 5A zeolite during 1-hexene adsorption were studied on a fixed-bed adsorber and a themogravimetric analyzer. Adsorption activity measurement, scanning electron microscope (SEM) analysis, X-ray diffraction (XRD) analysis, FT-IR analysis, 1H NMR analysis, and porosity measurement were used to reveal the mechanism of coking and deactivation of 5A zeolite, and evaluate the influences of binder on them. There are distinct increases in both coke content and deactivation degree with increasing the adsorption temperature. Deactivation degrees of zeolite increase as coke contents rise, however, they display smaller increasing rate at higher coke content. The rates of coke formation and deactivation of 5A zeolite are significantly enhanced by the binder mainly due to the fact that the activity sites offered by the amorphous compounds contained in the binder catalyze the formation of coke precursors. As compared to the coke formed in zeolite with binder, the coke in binderless zeolite is more aromatic. The coke which consists of inflammable part and nonflammable part can be oxidatively removed completely while the temperature approaches 787 K. No destruction in 5A zeolite crystal structure was observed in the regenerated binderless sample. The formation of coke during 1-hexene adsorption on zeolite can be explained using the carbonization-cyclization reaction mechanism. Furthermore, the kinetics models for formation and removal of coke were developed.