Synthesis, Characterization And Catalytic Performance Of Metal Heteroatom Molecular Sieves

By virtue of their uniform pore structure, large specific surface area,strong adsorption properties, molecular sieves are widely applied in various fields. With the rapid development of industrialization, pure silica molecular sieve has been unable to meet human needs. So the various modified molecular sieves were synthesized continuously. The metal heteroatom molecular sieves can be a very good improvement in acid sites and can effectively improve the catalytic activity and selectivity, so we study the metal heteroatom molecular sieves very necessary. Mesoporous molecular sieve while having excellent catalytic performance, but because the amorphous wall, causing the alkali resistance and hydrothermal stability are poor, is restricted in actual application. So the mesoporous molecular sieve crystallization become one method to solve this problem, and has become the hotspot of scientific research. Metal doped crystalline molecular sieve combines advantages of metal heteroatom molecular sieve and crystalline molecular sieve, it will become a good material in molecular sieve family. This paper mainly studies the one step synthesis of crystalline molecular sieve, and elaborated the synthesis conditions, at the same time, the samples were characterization and catalytic performance of structure test. The paper also studied the synthesis, characterization and catalytic properties of high content of metal heteroatom molecular sieves.This paper through the hydrothermal prepared by one step synthesis of metal heteroatom molecular sieves. Based on metal complexes and sixteen alkyl three methyl ammonium bromide (CTAB) complex as template agent, control of pH, reaction temperature, reaction time,material ratio, crystalline temperature, we synthesized the metal heteroatom molecular sieves successfully. We synthesized a series of high content of metal heteroatom mesoporous molecular sieve, with sixteen alkyl three methyl ammonium bromide (CTAB) as template agent, according to the S+I-I+I- mechanism of the synthesis. The samples were characterized by X-ray diffraction (XRD), X-ray fluorescence (XRF), inductively coupled plasma (ICP), scanning electron microscopy (SEM), high resolution transmission electron microscopy (HRTEM), nitrogen adsorption desorption (N2 adsorption-desorption), hydrogen temperature programmed desorption(H2-TPR), ammonia temperature programmed desorption (NH3-TPD),X-ray photoelectron spectroscopy (XPS), infrared absorptionspectroscopy (FT-IR),ultraviolet visible spectroscopy (UV-vis) and X-ray absorption fine structure (XAFS). And catalytic properties were investigated by cumene cracking reaction and residuum hydrocracking reaction. The main research results of the thesis are as follows:1. We synthesized a series of metal nickel (Ni) crystalline molecular sieves Cry-Ni for the first time. The content of Ni were 5.65%, 6.71%and 7.88%. Test results show that the material has the crystalline microporous MFI framework, but also has the typical structure of mesoporous MCM-41. Ni2+ in the form of six coordinated uniformity exists in the molecular skeleton. Samples have uniform pore structure,high specific surface area, large pore volume, perfect alkali resistance and good thermal stability. In cumene cracking and residuum hydrogenation catalytic cracking reaction, the Cry-Ni showed good catalytic performance.2. We successful synthesized the crystalline molecular sieve Cry-Co.The material having MFI skeleton and the mesoporous structure of MCM-41, at the same time the material with uniform pore structure, the metal atoms have better dispersion in the sample. The samples with highsurface area (425 m2g-1), larger pore volume (0.97 cm3g-1). The metalatoms in the form of six coordination better exist in the zeolite framework, the sample improves the acidity of zeolites. Cry-Co showed excellent catalytic properties in cumene cracking in catalytic reaction.3. The synthesis of doped metal iron (Fe) crystalline molecular sieves.Test results show that the sample has the similar Cry-Ni and Cry-Co crystalline phase and mesoporous structure.4. A series of high metal content of Ni-MCM-41 was synthesized by one-step hydrothermal synthesis method. The highest nickel content can up to 16.28 %.Test results show the Ni-MCM-41 has uniform mesopores,Ni2+ uniformly dispersed in the molecular skeleton. Ni2+ increases the acid and selective activity of mesoporous molecular sieves. In the reaction of hydrocracking of coker wax oil, high metal content Ni-MCM-41 showed excellent catalytic activity.