使用經濟與環境友善的方法合成功能化之SBA-15介孔材料的鑑定與應用

本博士論文是利用中性交聯共聚物為模版試劑，以經濟與對環境友善的觀點，合成含有奈米孔洞大小之介孔洞材料，探討其吸附與催化性質，並進一步改良傳統的合成條件，設計更簡單與更有效率的合成方法，以減少使用傳統合成法常用的強酸或強鹼試劑，並提升材料的產率。在第一個部分，我發現在接近中性的鹽類溶液中（pH ~ 4–5），以Pluronic P123三段式共聚合物為模版試劑，四乙氧基矽（Tetraethyl orthorsilicate，TEOS）為矽來源，利用鹽析效應，即可合成具有泡棉狀孔洞結構之二氧化矽介孔洞材料。若再加入適量的乙醇，則可得到孔洞排列規則的二氧化矽介孔洞材料，其孔洞結構類似SBA-15與MSU-H，這些合成條件不需使用強酸或強鹼試劑，是對環境友善的綠色製程。我也利用過渡金屬鹽類之水溶液的自生酸性環境，在不使用強鹽酸的條件下，製備含有高過渡金屬含量、且孔洞排列規則之SBA-15材料，並運用為異相催化反應之觸媒，結果發現含鈦之SBA-15材料，在環己烯的epoxidation反應上，有不錯的催化活性。含鋯、鐵與錫之SBA-15材料，則可催化pinacol-type重排反應，其中含鋯之SBA-15材料，較傳統的HY、ZSM-5與含金屬之AlPO-5等沸石材料有優越的催化活性，尤以大分子pinanediol之重排反應上更為顯著。在論文的第二個部分，我極力開發含有機官能基之SBA-15材料，藉由修飾傳統SBA-15之合成方法，在合成溶液中加入適量的Zr(IV)離子，濃度約為5.0–12.5 mM，成功製備了薄片狀SBA-15材料，並使其奈米孔道縮短到150–350奈米的範圍內，比傳統纖維狀SBA-15材料之微米長度的奈米孔道短了許多，因此分子在孔道中的擴散速率可以提升，亦大幅降低了孔道堵塞的問題。在熱重分析、原位（in situ）X光繞射與電子顯微鏡之冷凍蝕刻等技術的研究下，我發現在合成溶液中加入鋯離子，會大幅縮短P123微胞與TEOS的自組裝速率，增加二氧化矽之聚合度，因此使合成出的SBA-15材料具有薄片狀外型與超短介孔道。我也證實了具有超短介孔道之官能基化SBA-15材料，較傳統纖維狀、具有微米長度介孔道之官能基化SBA-15材料，對大型染料分子有較快的吸附速率與較高的吸附量。在異相催化反應上，我發現具超短介孔道之磺酸化SBA-15材料，在50 oC下，不需額外使用溶劑，即可有效催化羧酸與甲醇的酯化反應，極具潛力運用在生產生質柴油之觸媒材料。同時我也發現具短介孔道之胺基化SBA-15材料，可運用於抗氧化、抗癌與抗愛滋病藥物之flavanone合成，並可在短時間得到高flavanone產率，預期可取代傳統製程所使用液態強鹼，減少環境污染與副產物的形成。因此我相信含金屬之SBA-15材料與超短介孔道之官能基化SBA-15材料，為有效率的固態酸與鹼觸媒，在未來極有可能工業化，取代目前工業製程之液態酸與鹼觸媒，提供更經濟與環保的綠色製程。

關鍵字

介孔洞材料； SBA-15 ；固態酸鹼觸媒；異相催化

並列摘要

This thesis focused on the preparations and applications of functionalized mesoporous silica materials using block co-polymer P123 as the pore-directing agent with the thought of economy and environmental friendliness. In the first part, mesostructured silica and metal-incorporated SBA-15 materials were prepared without the addition of mineral acids. With the aid of NaCl, ultra-large mesocellular silica foams (MCF) were obtained in the P123-H2O-NaCl system, while ordered mesoporous silica materials with good hydrothermal stability and pore symmetry similar to SBA-15 and MSU-H materials were prepared by adding proper amount of ethanol as the co-solvent. By adding various metal precursors in the P123-H2O-NaCl system, highly ordered Sn-, Ti-, Fe- and Zr-SBA-15 materials with metal loadings up to ~10 mol% were easily obtained. Zr(IV) up to 10 mol% was found to be isomorphously substituted in the silica framework of Zr-SBA-15 materials, whereas extra-framework Fe2O3 clusters were formed in Fe-SBA-15 with Fe loading higher than 5 mol%. Zr-SBA-15 was superior to other metal-incorporated SBA-15 in catalyzing the liquid-phase pinacol-type rearrangement. The catalytic activities of Zr-SBA-15 were better than those of zeolitic materials and metal-incorporated AlPO-5, especially for bulky diol reactants. For Sn and Ti incorporated SBA-15, SnO2, and TiO2 nanocrystallites were formed inside the mesopores of SBA-15 materials when Sn/Si and Ti/Si molar ratios were greater than 3.8 mol%. The SnO2 and TiO2 nanocrystallites were not significantly aggregated and grew into large crystals upon heating (~1000 oC) due to the space confinement of the mesochannels. Concomitantly, the Sn- and Ti-SBA-15 materials were thermally stable up to ~ 1000 oC, superior to that of siliceous SBA-15 material, due to the stabilization of the mesopores by SnO2 and TiO2 nanocrystallites. Moreover, the formation of additionally superficial Ti(IV) with tetrahedral-coordinated environment and the decrease of surface hydroxyl groups were found by calcining the Ti-SBA-15 materials. With calcining at 800 oC, the Ti-SBA-15 materials with Ti/Si ratios of 0.03–0.05, which contained additionally superficial Ti(IV) species, suitable surface hydrophobicity and short mesochannels, could efficient catalyze epoxidation of cyclohexene toward cyclohexene epoxide. In the second part, homogeneously dispersed SBA-15 hexagonal thin platelets with short mesochannels were prepared by adding a proper amount of ZrOCl2 in the conventional SBA-15 synthesis solution. The formation mechanism was comprehensively investigated by in-situ small-angle XRD and freeze-fracture replication TEM techniques. The quick self-assembly of P123 micelles and TEOS induced by Zr(IV) ions nearby the interfaces was proposed to be responsible for the formation of SBA-15 platelets with short mesochannels. Similar route was extended to prepare organic functionalized SBA-15 platelets in one-pot. In addition, the morphology and the length of mesochannels could be fine-tuned from platelet morphology with short mesochannels (150–350 nm) to fiber-like morphology with long mesochannels (> 10 μm) by introducing various amounts of NaCl in the synthesis solution. The organic functionalized SBA-15 platelets with short mesochannels showed higher uptake amounts and faster adsorption rates toward new coccine dye and octadecane than those of SBA-15 fibers with long mesochannels. The functionalized SBA-15 platelets with short mesochannels also gave faster rates in catalyzing liquid phase reactions than those of SBA-15 fibers with long mesochannels, such as propylsulfonic acid functionalized SBA-15 in esterification of carboxylic acids and methanol, and aminopropyl-functionalized SBA-15 in Claisen-Schmidt condensation of benzaldehyde and 2’-hydroxyacetophone to form 2’-hydroxychalcone and flavanone. I believed that the organic-functionalized SBA-15 platelets with short mesochannels facilitate molecular diffusion and are promising in industrial applications.

並列關鍵字

mesoporous materials ； SBA-15 ； solid acid and base catalysts ； hetereogeous catalysts

參考文獻

71. Luan, Z.; Maes, E. M.; van der Heide, P. A. W.; Zhao, D.; Czernuszewicz, R. S.; Kevan, L. Chem. Mater. 1999, 11, 3680.

103. (a) Li, T.; Wong, S.-T.; Chao, M.-C.; Lin, H. P.; Mou C. Y.; Cheng, S Appl. Catal. A. 2004, 261, 211. (b) Chen, C.-L.; Li, T.; Xu, N.; Cheng, S.; Mou, C.-Y. Catal. Lett. 2002, 78, 223.

8. Chien, S. H.; Huang, K. C.; Kuo, M. C. Stud. Surf. Sci. Catal. 2004, 154, 2876.

90. Chen, S. Y.; Cheng, S. Stud. Surf. Sci. Catal. 2005, 156, 89.

23. (a) Wang, X. G.; Cheng, S.; Chan, J. C. C.; Chao, J. C. H. Micropor. Mesopor. Mater. 2006, 96, 321. (b) Wang, X. G.; Cheng, S.; Chan, J. C. C. J. Phys. Chem. C 2007, 111, 2156.

國際替代計量

使用經濟與環境友善的方法合成功能化之SBA-15介孔材料的鑑定與應用

全文下載

主題瀏覽