Synthesis, Characterization and Catalytic Properties of Metal-incorporated SBA-1 with Zeolitic Wall

• Main Authors: Tsung-Han Lin, 林宗翰
• Other Authors: Soofin Cheng
• Format: Others
• Language: zh-TW
• Published: 2014
• Online Access: http://ndltd.ncl.edu.tw/handle/96594827395655626841

博士 === 國立臺灣大學 === 化學研究所 === 102 === Cubic Pm3n mesoporous aluminosilicate isomorphous to SBA-1 with three-dimensional inter-connected pore structures was prepared in alkaline condition (pH around 9) using aluminum-incorporated ZSM-5 seeds as the Si and Al sources and cetyltriethylammonium bromide (CTEABr) as pore-directing agent with the aid of NaCl salt. The resultant materials (termed Al-ZSBA-1) with Al loading up to Al/Si molar ratio of 0.057 have cubic Pm3n structure and high surface areas (ca. 600 m2/g). They showed stronger acidities than the counter materials prepared using sodium silicate as the silica source (referred as Al-SBA-1-alk). Moreover, all the Al in Al-ZSBA-1 retained in tetrahedral coordination after calcination at 823 K, while a portion of Al incorporated in Al-SBA-1-alk became octahedrally coordinated. When applying the materials as catalysts in the alkylation of 2,4-di-tert-butylphenol (DTBP) with cinnamylalcohol to form flavan, Al-ZSBA-1 gave higher flavan selectivity of 75% and yield of 39% than Al-SBA-1-alk, mordenite, ZSM-5, and beta zeolites. These results demonstrated that the Al-ZSBA-1 materials owned the advantages of strong acidity from zeolite nanostructures and good diffusivity from mesopores. In addition, cubic Pm3n mesoporous Ti-incorporated silica with 1-5mol% Ti content have been prepared by co-condensation method and gold clusters were deposited on these supports by deposition-precipitation (DP) method. These resultant materials (termed yAu3+/xTi, x and y represent the Ti/Si molar percentage and Au/support weight percentage in the synthesis solution, respectively.) were characterized by XRD patterns, N2 adsorption-desorption isotherms, UV-Vis spectra and TEM. All samples have cubic Pm3n structure and high surface areas. The studies by UV-Vis spectra indicated that the Ti(IV) in the catalysts with low Ti content was favorably in tetrahedral (Td) coordination, whereas for the catalysts with Ti/Si molar ratio above 5%, a larger amount of Ti(IV) was in octahedral coordination. TEM images showed that the average particle size is larger than 3 nm as actual gold loadings is above 1wt%. The catalytic results showed the catalyst with low actual gold loadings (< 1wt%) which is more selective to PO, while at high gold loadings (> 1wt%), the catalyst showed lower PO selectivity. In propylene epoxidation with H2 and O2, 7.4% propene conversion and > 90% PO selectivity were achieved over 10Au3+/3Ti catalyst. We also successfully synthesized Ti-ZSBA-1 materials with zeolitic wall by using TS-1seeds as silica source and CTEABr as surfactant. The 10Au3+/3TiZ catalyst gave higher propylene conversion of 8.6% and PO selectivity of 92.6% than 10Au3+/3Ti. Most of all, the deactivation problem was improved significantly and the decay rate of 10Au3+/3TiZ is smaller than 10Au3+/3Ti.