Nengcui Zhang,Yimin Zhang,Feng Wu,Ziyan Liu,Xinyu Xu,Qiang Li,Yi Mei,Yun Zu
Phosphorus (P)-doping H-ZSM-5 zeolites, which is crucial for industrial applications, aim to adjust both acidity and framework stability while optimizing product distribution in heterogeneous catalysis. Nonetheless, current phosphating methods often suffer from inadequate phosphorus dispersion and unclear interfacial interactions with framework aluminum (Al). In this work, P-doping ZSM-5 zeolites were successfully one-step prepared by using tributylphosphine served as an organophosphorus precursor, assisting by density functional theory calculations. On account of this, a stable interface of tetracoordinated-phosphorus and framework Al was fabricated uniformly. Such an interfacial structure not only made more framework Al sit in the straight/sinusoidal channels, but also remodeled Brønsted acid sites and reinforced its acidity. Under comparable conditions, methanol-to-propylene (MTP) evaluations indicated that the high-silica PZ-75 zeolite catalyst displayed an appreciable catalytic lifetime (30 h) and a higher C 3 H 6 selectivity (52.4 %). Additionally, in-situ Fourier transform infrared spectroscopy further revealed that this exceptional MTP performance was attributable to the predominant olefinic pathway and lower hydrogen transfer ability. These results provide valuable information for cognizing phosphorus-zeolite chemistry and creating high-performance MTP catalytic materials.
The small pore aluminosilicate zeolites are always accompanied by the abundant framework aluminum content and the consequential extra-framework counterparts severely restrained its application in the gas separation process. In this work, the high-silica zeolite ERI (Si/Al = 7.3) was successfully fabricated using a OSDA in the potassium cation medium. It is found that the spatial distribution of aluminum sites in the ERI zeolite can be effectively tailored in the synthetic system with varying aluminum content. Furthermore, the ERI frameworks with spatially biased aluminum sites were also clarified. By combining multiple spectroscopy techniques and powder X-ray diffraction crystallography, the framework of aluminum sites related to host-guest interactions confined in high-silica ERI was clarified. In the gas separation of a binary mixture of O 2 /N 2 (21:79 v /v), the Sr 2+ cation-exchanged high-silica zeolite ERI exhibited efficient O 2 adsorption capacity: 0.74 mmol·g −1 and IAST selectivity: 2.89. These findings not only provide a structural foundation but also offer a model for the efficient separation of O 2 from multi-component gas mixtures.
Linjie Guan,Meiyu Liu,Honghai Liu,Li Zhang,Yiming Zhang,Yucai Qin,Binbin He,Yi Mei,Yun Zu
The regulation of the engineering regionally spatial framework aluminum (Al F ) distribution in MFI channels has been considered as an effective way for the production of light olefins by targeted fluid catalytic cracking (TCO) technology. In this work, ZSM-5 zeolites with controlled Al F distributions are facilely synthesized by tuning the combinations of pentaerythritol (PET), tetrapropylammonium (TPA) and Na cations. The Al F atoms in the prepared HZ5-[PET + Na] and HZ5-[TPA] samples are enriched in the straight channels and intersection channels, respectively, which are favorable to the n-butane monomolecular reaction pathway, promoting the propylene production. Whereas the Al F atoms in the HZ5-[TPA + Na] sample are simultaneously distributed in both the straight and intersection channels, the n-butane molecules preferentially take place monomolecular reaction in the straight channels to generate carbonium ions (e.g., C 2 H 5 + , C 3 H 7 + and C 4 H 9 + ). Subsequently, all of them enter into the intersection channels to induce the occurrence of bimolecular reaction. Such a process is conducive to the formation of ethylene. These insights can help to clarify the catalytic behavior of regional framework acid sites in ZSM-5 channels and then provide an effective approach to design efficient TCO catalysts.
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