不同結構之含鋁介孔材料之合成與催化反應比較

Abstract

本研究在鹼性條件(pH8-10)下利用共沉澱法合成，以陽離子型界面活性劑CTEABr(Cetyltriethylammonium bromide)作為模板，矽源為sodium silicate (Na2SiO3)，加入NaAlO2作為鋁源來合成不同孔洞結構之含鋁介孔二氧化矽。利用不同陰離子來調控孔洞結構，其中(Cl-與NO3-)可以分別得到具有三維立方堆積孔洞結構(3D-cubic，Pm3n)之介孔材料SBA-1-alk與二維六方堆積孔洞結構(2D-hexagonal，p6mm)之介孔材料HMM-alk，加入的鋁金屬含量達到Al/Si=5％。接著將矽源換成ZSM-5沸石晶種合成具有結晶性孔壁的ZSBA-1-alk結構，並以CTMABr作為模板合成二維六方堆積孔洞結構MCM-41分別與非晶相孔壁的Al-SBA-1-alk和Al-HMM-alk做比較。所合成的材料經由XRD、N2 adsorption-desorption isotherm、FT-IR、Al-NMR 和TPD等技術鑑定，可得知所合成出來的材料有很好的二維或三維介孔結構、表面積達到900 m2/g、加入晶種的ZSBA-1-alk酸含量比SBA-1-alk高，孔壁具有ZSM-5的結晶性、大部分的鋁離子是在骨架的四面體中心。最後利用所製備含鋁介孔材料作為酸觸媒，催法2,4-di-tert-butylphenol及cinnamyl alcohol的烷基化反應，結果三維立方堆積的Al-SBA-1-alk催化活性高於二維六方堆積的Al-MCM-41及Al-HMM-alk，而含沸石晶種的5Al-ZSBA-1-alk的催化效果最好，flavan的產率在95 °c反應4小時可以達到56％(mol/g catal)。

Al-incorporated 3D-cubic(Pm3n) SBA-1-alk and 2D-hexagonal(p6mm) HMM-alk were synthesized by one-pot method in alkaline condition (pH=8-10) by using CTEABr (Cetyltriethylammonium bromide) as the template NaAlO2 as Al source, and Na-silicate as the silica source in the presence of NO3- and Cl- anions, respectively. Furthermore, Al-incorporated ZSM-5 seeds were used as the Al and Si sources to synthesize cubic Al-ZSBA-1-alk. Meanwhile, Al-MCM-41 was compared using CTMABr as the template in order to compared the properties with Al-SBA-1-alk and Al-HMM-alk. The resultant materials were characterized by X-ray diffraction (XRD), N2 adsorption-desorption isotherm, FT-IR, Al-NMR and TPD. The small-angle XRD patterns of Al-SBA-1-alk and Al-HMM-alk confirmed the 3-D cubic Pm3n phase and 2-D hexagonal p6mm phases. ZSBA-1-alk exhibited an absorption band at 550 cm-1 in the FT-IR spectrum, which is assigned to the stretching of five-membered T-O-T (T = Si or Al) rings in ZSM-5. In Al-NMR most Al is assigned to the tetrahedrally-coordinated Al species The materials were tested as catalysts in alkylation of 2,4-di-tert-butylphenol with cinnamyl alcohol.3D-cubic Al-SBA-1-alk showed better activity than 2D-hexagonal Al-HMM-alk and Al-MCM-41, while 5Al-ZSBA-1-alk gave the best catalyst activity and yield reached 56％(mol/g catal) at 95 °C in 4 hours.