規則排列之穩定中孔洞矽化物及碳材的合成與鑑定

Synthesis and Characterization of Ordered and Stable Mesoporous Silica and Carbon Materials

丁君強(Chun-Chiang Ting)

指導教授 ： 高憲明

國立中央大學/理學院/化學系/博士(2010年)

摘要

中文摘要：
本論文研究的目的是藉由有機模板 (界面活性劑)、糖分子與與四乙基矽氧烷 (tetraethoxysilane, TEOS)，在酸性水溶液中利用多成份共自組裝現象 (multi-component cooperative assembly) 合成具有不同結構且規則排列的中孔洞氧化矽 (mesoporous silica) 及中孔洞碳材 (mesoporous carbons)。
在合成具立方體結構 ( ) 的中孔洞矽化合物 SBA-1 的研究中，在不同合成溫度範圍下藉由添加左旋果糖 (D-fructose) 或是蔗糖 (sucrose),以四乙基矽氧烷為矽源並且添加做為有機模板的溴化十六基三乙氧基銨 (cetyltriethylammonium bromide, CTEABr),在酸性水溶液中形成規則排列的立方體中孔洞矽化物 SBA-1。在本篇研究中藉由固態核磁共振光譜的技術 (solid-state NMR),闡明在不同合成溫度以及反應條件下規則立方體結構 ( ) 中孔洞矽化物 SBA-1的形成，是由於左旋果糖及其衍生物會與做為有機模板的溴化十六基三乙氧基銨在水溶液中纏繞 (entangled) 形成穩定的球狀微胞 (spherical micelles) 以形成立方體結構。為了達到良好的熱及水熱穩定度 (thermal and hydrothermal stability) 的產物，不同的合成條件在文中皆被詳細的探討。相對於早期所發表的文獻中的 SBA-1 產物皆須在低溫合成下方可得到，在此次研究中利用此一添加糖類的策略確實可在高溫的合成條件下得到穩定與規則排列的立方體結構的 SBA-1。
為了近一步探討溴化烷基三乙氧基銨 (CnH2n+1N(C2H5)3Br) 中烷基鏈段長度 (alkyl-length) 對於形成 SBA-1 結構的影響，在文中採用較溴化十六基三乙氧基銨烷基鏈段較短的氯化十二基三甲氧基銨 (dodecyltrimethyl ammonium chloride (C12TMACl) 做為有機模板，在酸性水溶液中以及不同的合成溫度的環境中合成規則且表面形態 (morphology) 豐富的立方體排列 ( ) 的中孔洞矽化合物。藉由29Si MAS NMR 的觀察下，改變合成溫度及鹽酸濃度的反應條件，氧化矽骨架交聯程度 (silica framework cross-linking) 會隨之提高,並且藉由 SEM 的觀察下可觀察到所形成的氧化矽中孔洞 SBA-1 豐富的形態變化。
在論文的第二部份是藉由前述的多成份組成共自組裝的方式，使用低價且對環境友善的蔗糖做為碳源和輔助結構導向試劑 (auxiliary structure-directing agent)、四乙基矽氧烷、低分子量的醇類 (微胞修飾劑 (modified)) 以及做為碳源及有機模板來源的三區塊高分子共聚合物 (triblock copolymer) P123，在酸性水溶液的環境下合成具立方體排列 (I4132) 及六角柱狀排列 (hexagonal) (p6mm) 的中孔洞碳材。藉由碳化合物前驅物-有機模板-矽化物 (carbon precursor-organic templates-silica) 以多成份自組裝 (multi-component assembly) 現象直接合成規則立方體 (I4132) 及六角柱狀排列 (P6mm) 排列的中孔洞碳/矽混成物。在熱處理的過程中作為碳前驅物的糖分 子會聚合成較大分子量的寡聚合物 (oligomer),利用糖分子本身所具有的氫氧官能基 (hydroxyl groups) 在酸性的環境下藉由S+X-I+機制與陽離子界面活性劑以靜電作用力 (electrostatic bonding) 形成規則立方體排列的中孔材料。在藉由無氧熱處理移除模板移除及碳化處理後得到立方體排列的中孔洞碳/矽複合材料 (composite),在氧化矽移除之後即可得到具有穩定結構且規則排列的中孔洞碳化合物材料。藉由選擇合適的反應條件以調控界面活性劑微胞的形狀，在合適的矽-蔗糖-P123共聚高分子的組成下,利用此一獨特且便利的方法來合成不同結構且規則排列的中孔洞碳化合物。

關鍵字

中孔碳材 ； 左旋果糖 ； 蔗糖 ； 中孔洞矽化合物

並列摘要

Abstract
The goal of this thesis is to synthesize the highly ordered mesoporous silica and carbons with different structures (such as for silica, I4132 and P6mm for carbons) from multi-component cooperative assembly route with sucrose, organic template (surfactant) and inorganic silica (tetraethoxysilane, TEOS) building blocks by a facile acidic aqueous pathway.
In the study of synthesis of cubic ( ) mesoporous silica SBA-1, it has been synthesized at different loadings of D-fructose over a broad temperature range with tetraethoxysilane (TEOS) and cetyltriethylammonium bromide (CTEABr) as silicon source and template agent under highly acidic conditions. In our research shows that the derivatives of D-fructose and the surfactant molecules are entangled with each other to form stable spherical micelles with adequate curvatures for the formation of cubic mesophase in a wide range of synthesis conditions by the solid-state NMR. Various synthesis parameters have been investigated under different synthesis conditions in order to obtain the highly ordered mesoporous silica SBA-1 materials with good thermal and hydrothermal stability. In contrast to earlier published results requiring the low synthesis temperature, this strategy allows for the preservation of the SBA-1 mesophase under high temperature synthesis conditions and leads to a highly cross-linked silica framework. In ordered to discuss the effect of hydrophobic alkyl-length of alkyltriethylammonium bromide CnH2n+1N(C2H5)3Br in the formation of cubic ( )mesophase, cubic mesoporous silica SBA-1 with rich morphologies have been synthesized by using dodecyltrimethyl ammonium chloride (C12TMACl), a surfactant with a relatively short chain as compared to the conventional C16TMABr, as the template under strong acidic conditions over a broad synthesis temperature range and synthesis compositions. Increasing the synthesis temperature and HCl concentration during the synthesis not only increased the degree of silica framework cross-linking, but controlled the undesirable phase transformation and lavish morphology variation observed in the conventional synthesis of pure silica SBA-1, as also evident from 29Si MAS NMR and SEM.
The second part of this thesis is to provide a facile and efficient method for the synthesis of highly ordered cubic (space group I4132) and hexagonal (P6mm) mesoporous carbons/silica nanocomposites through multi-component assembly route by simply using low?cost and environmentally friendly sucrose as an auxiliary structure-directing agent and carbon source, tetraethoxysilane (TEOS), low-molecular weigh alcohol as micelle modified agents and triblock copolymer surfactant P123 as well as carbon source and structure-directing agent under weakly acidic?aqueous media. The uniform cubic mesoporous carbon materials were synthesized by the direct carbonization of carbon precursor-templates-silica materials under acidic aqueous condition. Similar to silicate clusters that contain silanol groups, the sugar contain a large number of hydroxyl groups can provide the (S+X-I+) pathway, where S, X, and I correspond to surfactant, halide, and inorganic species, respectively under acidic conditions. Furthermore, similar to the silicate condensation reaction, the sugars undergo polymerization at similar temperature forming cross-linked oligomer. Driven by electrostatic bonding, these building blocks co-operatively assemble with surfactant resulting in ordered nanocomposites after silicate condensation and sugar polymerization. Carbonization and subsequent surfactant removal create ordered mesoporous carbon/silica nanocomposite. Selecting appropriate reaction conditions can be control the shape of the surfactant assemblies; this novel and facile method can be used to synthesize various mesostructure carbons with controlled composition through optimizing the molar composition of silica-sucrose-P123 copolymer.

並列關鍵字

D-fructose ； sucrose ； mwsoporous silica materials ； mesoporous carbons

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