Exploration of the dynamic equilibrium between the rare earth location within RE-NaY zeolite and the FCC carbon deposition precursor

Abstract

In this research, we formulated a systematic and elaborate experimental protocol.Initially, a minute quantity of Ce was introduced into the NaY framework via the hydrothermal method, followed by gradient temperature calcination to acquire a series of Ce-NaY samples. Subsequently, a multi-dimensional characterization method was adopted. This method included HRTEM, Refinement of XPRD structure, XPS, NH3-TPD, Py-FTIR, In-situ IR-catalytic conversion using cyclohexene as the probe, and microreactor hydrogen transfer activity assessment. The aim was to precisely trace the location of low-content Ce within the framework and uncover its regulatory mechanism regarding the " precursor " of FCC carbon deposition. The results indicated that the Ce0.01-550Y sample achieved the lowest carbon deposition while maintaining the highest cyclohexane yield. Its excellent performance stemmed from the fine matching and synergistic effect of Brønsted acid and Lewis acid densities. This research indicates that by precisely adjusting the spatial distribution of rare earth ions in NaY zeolite, the steps that initiate carbon deposition can be hindered, thereby reducing the selectivity of carbon deposition.