Potential hidden sites in FAUJASITE: New insights on a proton transfer mechanism
报告人
Dr. Louwanda Lakiss（CNRS, France）
报告时间
2022年6月15日（周三）19:30
主办方
中国石油大学（华东）化学化工学院
直播二维码
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报告摘要
Zeolite Y and its ultra-stabilized hierarchical derivative (USY) are widely used in oil refining, petrochemistry, and other chemicals manufacturing. After almost 60 years of academic and industrial research, their resilience is unique as no other catalyst displaced them from key processes such as FCC and hydrocracking. The three-dimensional FAU structure is built from sodalite cages (cubo-octahedral units of 24 T atoms, t-toc) linked by hexagonal prisms (double-six rings of 12 T atoms, t-hpr), generating a supercage with a diameter of 1.3 nm. This supercage is accessible through 12 membered ring windows with a diameter of 0.73 nm. Although the FAU-type structure is one of the most open amongst the known zeolites, only a third of its active sites, those located in the supercage, are accessible to reactants. On the other side, its ultra stabilized forms USY contain far fewer active sites than their parent Y, but they exhibit a much higher catalytic activity. Numerous studies attribute this superior performance to a synergy between the extraframework aluminum species (EFAl) generated during stabilization processes and vicinal Brønsted acid sites. Even though several papers reported that EFAl species increase some hydrocarbons (i-C₄H₁₀, n-C₅H₁₂ and n-C₆H₁₄) cracking rates, they all failed to find a direct correlation between these species and the catalytic activity of USY catalysts. In a nutshell, the fundamentals of such an unexpectedly high catalytic activity in USY are still debated. To shed more light on this superior activity, a multi-technique study combining advanced spectroscopies (IR and solid-state NMR) and molecular modeling will be reported and discussed.