Phosphorus promotion on hydrothermal stability of ZSM-5 by P precursors with different molecular sizes

• Published in: Microporous and mesoporous materials 2023-10, Vol.360, p.112706, Article 112706
• Main Authors: Ni, Ne, Gao, Xiuzhi, Xing, Enhui, Zhu, Yuan, Liu, Jianqiang, Xin, Mudi, Ouyang, Ying, Luo, Yibin, Shu, Xingtian
• Format: Article
• Language: English
• Subjects: Catalytic cracking; Hydrothermal stability; P precursor; Phosphorus modification; ZSM-5
• ISSN: 1387-1811; 1873-3093
• DOI: 10.1016/j.micromeso.2023.112706

The promotional effects of phosphorous modification on ZSM-5 zeolites by phosphorus oxyacids (H4P2O7, H3PO4, H3PO3, and H3PO2) with different molecular sizes were investigated with catalytic cracking of n-tetradecane as the probe reaction. It was verified that the diffusion of P precursor molecules into ZSM-5 channels was important to prevent aggregation of P species for better stabilization on tetra-coordinated framework aluminum. Meanwhile, the P–Al interaction was proposed based on results of 27Al, 31P, and 29Si MAS NMR. With H3PO2 as the P precursor, easy diffusion into ZSM-5 channels contributed to less formation of polyphosphates, homogeneous distribution of P species, better reserved crystallinity, microporous area and acidic sites for improving cracking performance of n-tetradecane. [Display omitted] •H3PO2 can significantly improve the hydrothermal stability of ZSM-5.•Easy diffusion of H3PO2 into channels of ZSM-5 is the key to stabilize TFAl.•Easy diffusion of H3PO2 led to less formation of large polyphosphates.•H3PO2 was oxidized and coordinated to TFAl during modification on ZSM-5.•Catalytic cracking of n-tetradecane was greatly enhanced over H3PO2 modified ZSM-5.