Jiajun Zheng

Synthesis of Wool-Ball-Like ZSM-5 with Enlarged External Surfaces and Improved Diffusion: A Potential Highly-Efficient FCC Catalyst Component for Elevating Pre-cracking of Large Molecules and Catalytic Longevity

A hierarchical ZSM-5 zeolite composed of nano-sized MFI zeolite crystals was synthesized without using secondary template by a traditional hydrothermal procedure. The as-synthesized hierarchical ZSM-5 and a reference catalyst were both characterized by XRD, SEM, FT-IR, in situ infrared (IR) spectrometry of pyridine, NH3-TPD, N2 adsorption–desorption, intelligent gravimetric analyzer, and by thermogravimetry analyses. After examining and comparing the results, it is discovered that the hierarchical ZSM-5 catalyst displays excellent catalytic performance with an improved conversion of isopropylbenzene and a longer catalytic life because of its dramatically enlarged external surfaces. The results also display that the shortened diffusion path length contributes to enhancing the stability of the hierarchical catalyst by depressing the coking deposit during the catalytic cracking of n-octane.Graphical AbstractA wool-ball-like zeolite composed of nano-sized MFI crystals was synthesized without a secondary template by the traditional hydrothermal procedure. Nanocrystallization of crystal particles in the hierarchical ZSM-5 zeolite gives the catalyst an improved diffusion and a dramatically enhanced external surface which contributes to elevating pre-cracking of large molecules and catalytic longevity, and to offering a potential and high-efficiency FCC catalyst component.

Synthesis, characterization and n-hexane hydroisomerization performances of Pt supported on alkali treated ZSM-22 and ZSM-48

ZSM-48 and ZSM-22 zeolites with similar Si/Al molar ratio have been treated with alkali to modify the pore structures and acidity, and alkali treated ZSM-22 and ZSM-48 samples have been characterized by X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), N2 adsorption/desorption, Nuclear Magnetic Resonance (NMR), NH3-Temperature Programmed Desorption (NH3-TPD) and Pyridine-Fourier Transform Infrared Spectroscopy (Py-FTIR). Characterization results indicate that NaOH treatment could improve the mesoporous structure for both ZSM-22 and ZSM-48. NaOH treatment modifies the acidity of ZSM-22 and ZSM-48 diversely. The n-hexane hydroisomerization performances of Pt supported protonic form ZSM-22 and ZSM-48 (Pt/HZSM-22 and Pt/HZSM-48) bifunctional catalysts have been evaluated in a fixed bed reactor. Catalytic results indicate that catalytic activity and selectivity depend on both pore structure and acidity of zeolites. In comparison of Pt/HZSM-22 and Pt/HZSM-48, Pt/HZSM-22 shows better n-hexane hydroisomerization performance at relatively low temperature ( 300 °C) Pt/HZSM-48 exhibits better catalytic performance. Moreover, alkali treated Pt/HZSM-48 could produce more di-branched isomer compared with alkali treated Pt/HZSM-22.

Synthesis and characterization of zeolitic composite ZSM-5/MOR with multi-modal pores

Abstract ZSM-5/MOR zeolitic composite was prepared by a two-step synthetic route and characterized by SEM, N 2 adsorption and NH 3 -TPD. The results showed the composite has different acid property and multi-modal pore structure from the physical mixture of two zeolites, and a strong acid center is formed in the composite. In the catalytic cracking reaction of n-octane, the composite ZSM-5/MOR has higher conversion and longer life than their physical mixture.