Study On Synthesis And Catalytic Properties Of Porous Montmorillonite Heterostructured Materials

Porous clay heterostructures (PCHs) is a novel porous materials which structures and performances are superior to traditional pillared clays. Its pore size range from micropore of zeolites, pillared clays to mesopores of M41S. Heavy crude oils, biological molecules and other large macromolecular species can be accommodated into PCHs galleries for shape-selective processing or catalysis.In this thesis, Na-montmorillonite as start layered material was purified and then modified with quaternary ammonium, the resulting organoclay mixed and reacted with neutral amine and tetraethylorthosilicate (TEOS) make the interlamellar hydrolysis and condensation polymerization of TEOS directed by intercalated quaternary ammonium cations and neutral amine as co-surfactants. The gel from centrifuging above mixtures was dried in air and then calcined in air atmosphere, thus PCHs was obtained. Firstly, the PCHs synthesis conditions and their effects on PCHs were studied. Then, the structure of PCHs was characterized by the means of X-ray diffraction(XRD), thermogravimetric(TG), FT-IR and N2 adsorption-desorption isotherms measurements. The catalytic properties of PCHs as catalysts in synthesizing 4-tert-butylcatechol through alkylation of catechol with tert-butyl alcohol were investigated at last.By studying on PCHs synthetic conditions and its effects on PCHs, experiments results shows that PCHs, prepared under the condition of organoclay/neutral amine/TEOS molar ratio of 1:20:150, reaction time of 6~8h and calcined temperature of 500-800癈, have a well-ordered layered structure. The quaternary ammonium cations and neutral amine have a structure-directing template functions on the PCHs formation,"that is say, the basal spacing of PCHs can be tailored through the chain length of quaternary ammonium cations and neutral amine. The aluminum added into PCHs can destruct the layered structure of PCHs.By XRD, TG, FT-IR and Na adsorption-desorption isotherms measurements, XRD results suggested that PCHs have a larger basal spacing than the nativeMontmorillonite and organoclay, PCHs basal spacing values are in the range of 21.3-29.8 A, and it still have a large value even though after calcined at 700 ℃. The result of FT-IR indicated that silica or alumina intercalated into Montmorillonite interlayer can destructed the layered structure of Montmorillonite. The Na adsorption-desorption isotherms is type IV according to BDDT, attributed to the mesopore in materials. The samples of PCHs calcined at 500 癈 have a high BET surface area ranging from 502.6 to 821.1 cm2/g and a sharp and single pore size distribution of 39A or so. Some samples have a 661.1 cm2/g BET surface area and 22 A pore size even though have calcined at high temperature of 700 C.Catalytic properties of PCHs in alkylation of catechol with tert-butyl alcohol to 4-tert-butylcatechol was investigated at last. The results showed that the reaction time, neutral and calcined temperature and incorporation of Al in synthesizing PCHs all had a influences on its catalytic performance, and the highest yield of 4-TBC of all samples was 19.6%,the lowest yield of 4-TBC was 9.2%. Comparison its catalytic performances with other Montmorillonite catalysts, it have a higher yield of 4-TBC than native Na-Montmorillonite but lower than acid-treated Montmorillonite, and the Si-PCHs are better catalyst than Si-Al-PCHs in synthesizing 4-TBC.