利用含鈦沸石前驅物合成結晶型孔壁SBA-1介孔材料以及其催化應用

Abstract

本研究首先以鹼式法合成介孔分子篩SBA-1，使用十六長碳鏈而親水端稍大的陽離子型界面活性劑cetyltriethylammouium bromide (CTEABr) 當作模板，矽源選擇使用經濟效益上非常便宜的水玻璃(Na-silicate)，在鹼性條件下 (pH=8.0~10.0) 來合成具有三維孔洞結構的介孔分子篩SBA-1。接著將矽源換成ZSM-5沸石晶種來合成具有結晶型孔壁的SBA-1，在合成過程中必須調控ZSM-5沸石晶種的水熱時間，水熱時間過長會造成沸石與介孔分子篩分相的情形，然而水熱時間太短會導致ZSM-5沸石晶種的結晶性太差。接著，將鈦離子 (Ti4+) 引入到ZSM-5骨架中形成TS-1沸石晶種，並且使用TS-1沸石晶種當作矽源，來製備具有三維孔洞結構的介孔分子篩SBA-1。所得材料經由XRD、N2 adsorption-desorption isotherm、FT-IR、UV-Vis spectrum和XANES等技術鑑定，可得知所合成出來的材料擁有很好的三維介孔結構、表面積可達到900 m2/g左右、孔壁具有ZSM-5的結晶性，而且大多數的鈦離子是在骨架中的四面體中心，利用所得含TS-1沸石晶種的SBA-1介孔材料做為觸媒，檢測其催化2,3,6-三甲基苯酚氧化反應的活性，發現以1TSBA-1-22-8.70這個觸媒的催化效果最好，TMP的轉化率和TMBQ的選擇率分別可以達到37.3%和91.9%。

First, cubic Pm3n SBA-1 was synthesized successfully in alkaline condition (pH=8.0~10.0) by using CTEABr as the template and Na-silicate, which is very cheap for commercial use, as the silca source. Then, Na-silicate was replaced by ZSM-5 seeds as the silica source to synthesize cubic SBA-1 and controlling the hydrothermal period of the ZSM-5 seeds was found to be essential in order to obtain crystalline ZSM-5 without observing the separation phase from the mesoporous structure. Finally, Ti-silicalite (TS-1) seeds were used as the silica precursor and CTEABr as the template to synthesize new mesostructured material labeled as TSBA-1 by co-precipitation method. The resultant materials were as characterized by X-ray diffraction (XRD), N2 adsorption-desorption isotherm, FT-IR, UV-Vis spectroscopy and XANES. The small-angle XRD patterns of the as-synthesized TSBA-1 reveled three peaks indexed as (200), (211) and (220) of the 3-D cubic Pm3n phase. Moreover, no seperated phase of ZSM-5 was observed in the high-angle region. TSBA-1 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 Ti) rings in ZSM-5. In UV-Vis spectra, TSBA-1 had an obvious absorption band at 220 nm, assigned to the tetrahedrally-coordinated Ti species. The materials were tested as catalysts in oxidation of 2,3,6-trimethyphenol (TMP). The optimal conversion of TMP and selectivity of TMBQ are 37.3% and 91.9% respectively.