Interlayer Structural Modification And Structure Resolution Of Layered Zeolites

The zeolite materials with new structures were synthesized in the dissertation, with the purpose to relieve the diffusion limitation for the large-size reactant and product in small or medium pores, and to improve the accessibility of the catalytic active sites in zeolites. The thesis is composed of four parts, including the interlayer silylation of the lamellar zeolite precursors to form the interlayer expanded zeolite (IEZ), the post-treatment of the germanosilicates zeolites, the synthesis of the zeolite nanosheetThe interlayer expanded zeolite BEZ-Nu-6(1) was synthesized by using the organosilane Me2Si(OEt)2 (DEDMS) to insert into the interlayer of Nu-6(1) in the first part. Through the analysis of condition for IEZ, the high quality IEZ-Nu-6 must be synthesized in the hydrochloric acid/ethanol solution. When water was used as the solvent, the zeolite with a poor quality was obtained. During silylation, the organic structure directing agent (OSDA) of Nu-6(1) was quickly leached from the interlayer to the solution when using water as the solvent, but DEDMS could not be inserted the interlayer. When using ethanol, the leaching of SDA and insertion of DEDMS was well balanced, giving rise to a good IEZ zeolite. Using DFT to optimize the structure and refinement, IEZ-Nu-6 with two kinds of ten member ring, which has larger pore, was more active than Nu-6(2) in the esterification of acetic acid and ethanol.In the second part, the lamellar precursor PREFER was applied to develop a new type of interlayer expanded zeolite IEZ-FER(D4h) by the molecular alkoxysilylation under the assistance of the thermal acid treatment, using 1,3,5,7-tetramethyl cyclotetrasiloxane (D4h) as a silylating agent to connect neighboring layers. The experimental results show that as synthesized IEZ-FER(D4h) exhibits expanded interlayer spacing along a axis direction. The 4-membered ring (4MR) exists in the EEZ-FER(D4h) as the building unit, the methyl groups rendering the hydrophobic properties also exists in the structure. The newly formed channel systems exhibit 12MR and 14MR pores along the [010] and [001] respectively, which is different from that of the 3D FER. Rietveld crystal structure refinements of the PXRD patterns of the IEZ-FER(D4h) confirm that the proposed framework model are correct, and reveal that the 4MR indeed exists. In addition, XRD, UV-Raman, NMR, IR and BET techniques were employed to characterize the physical properties, and the vapor adsorption was carried out to characterize the pore size, hydrophobicity and hydrophily.In the third part, the nanosheet zeolite ECNU-9 was synthesized by using 1-butyl-3-methyl imidazolium hydroxide as OSDA, which was only two unit cells thick along a axis. The nanosheets have regular geometry and good dispersion. Using the software DIFFaX to simulate the structure of ECNU-9, it was found that ECNU-9 has the ten member ring and twelve member ring. According to the crystallization of ECNU-9, the micellar blocking crystallization mechanism is proposed, adding the inorganic salts which have the hydration, the ionic liquid can aggregate into positively charged micellar, which can attract the negative SiO44- or GeO44- species on the surface of the micellar to crystallize into ECNU-9.In the fourth part, the zeolite IM-20 was post-treated in acid solution, and the material with new structure were obtained by structural reorganization. The material ECNU-12 was obtained, strong acid solution using water as the solvent, the structure of ECNU-12 originated from IM-20 which was taken off two kinds of double four member rings. The material ECNU-13 was obtained under the strong acid solution using ethanol as the solvent, the structure of ECNU-13 originated from IM-20 which was taken off one kind of double four member ring. Using the DFT to optimize the structure, and then to simulate the XRD patterns compared with the experimental patterns, which was almost the same.