Mengyue Li,Yi Zhai,Xubin Zhang,Fumin Wang,Guojun Lv,Mengyao Li,Qing Zhang,Yongkui Liu
It is of great significance to develop a novel strategy to synthesize hollow zeolite without using mesoporogens due to its extremely short diffusion length. Ferric nitrate as a common iron source and structure direction agent has been used for synthesizing Fe-doped zeolite. However, the effect of ferric nitrate on the morphology of zeolite has not yet been elaborated. Here, we successfully synthesized hollow MFI zeolite with a framework iron-rich surface by using ferric nitrate as an iron source and seed-assistant strategy. It is the first time to propose that inorganic iron has the hollow structure-directing effect. Herein, by comparatively investigated the effect of iron content on the structure and evolution process of hollow zeolite, a novel crystallization mechanism has been proposed based on the competitive relationship between crystallization and dissolution rates. When the Si/Fe ratio reaches 25, the internal dissolution rate of seeds is faster than the surface crystallization rate of zeolite, the hollow structures are acquired. The obtained Fe-doped hollow zeolite exhibits superior catalytic performance for the reaction of phenol degradation. In this reaction, the higher effectiveness factor (η) close to 1 of Fe-doped hollow zeolite confirmed by calculations indicates its superior mass transferability.
A hollow zeolite encapsulated Rh catalyst Rh@H-S-1 with an “eggshell” structure was prepared using the method of organic alkali treatment and recrystallization. Compared with catalysts with directly encapsulated Rh@S-1 and surface impregnated Rh/S-1, this catalyst exhibited both superior activity and a higher TOF value in hydroformylation of 1-hexene due to the high dispersion of Rh and high diffusion. The Rh element did not need to be reduced in the preparation, and it was in situ reduced by the syngas. The content of lower valence Rh δ+ gradually increased with the reaction procedure and played as an active center. The low oxidized state Rh + or Rh δ+ in the form of Rh(CO) 2 are proposed as active sites in hydroformylation, which were generated under the synergistic effect between CO and H 2 . Importantly, the hollow encapsulated catalyst effectively decreased Rh leaching to 0.1 ppm and showed better stability compared with the impregnated Rh/S-1 catalyst.
危险品化学品经营许可证（带存储）