Consideration of the methanol-to-olefins (MTO) reaction over different zirconium species of the Zr-SAPO catalyst: a comprehensive periodic DFT investigation

Abstract

Methanol-to-olefins (MTO) conversion is a crucial industrial process for producing valuable light olefins, but developing highly efficient and selective catalysts remains a significant challenge. The incorporation of zirconium has been shown to enhance the catalytic performance of MTO catalysts. In this study, periodic density functional theory (DFT) calculations were employed to investigate the stability and reactivity of zirconium species within the SAPO-18 framework. Results revealed that loading Zr³⁺ ions into 6-membered rings (6MRs) of the SAPO-18 framework (Zr-ZH) was the most favorable configuration for producing propylene, with a lower activation energy (0.46 eV) than that required for loading Zr⁴⁺ ions into 8-membered rings (8MRs) (Zr-ZOH). Analysis of Mulliken charges and partial density of states (DOS) suggested that the incorporation of zirconium into the SAPO-18 framework enhanced the electronic properties of the catalyst, leading to a significant increase in propylene selectivity. In summary, the DFT calculations provided valuable insights into the preferred coordination environments and electronic structures of zirconium species in the SAPO-18 catalyst. These results suggest that optimizing zirconium incorporation can lead to significant improvements in the catalytic performance of MTO processes, particularly with respect to propylene selectivity.