| 摘要: | 氟化作用對於增進氧化物觸媒如氧化鋁之觸媒活性是一個很重要的處理過程，近年來，氟化作用常常被用來增進沸石中的催化活性，氟化試劑和氟化量已經被廣泛地研究並且發現對於氟化觸媒之活性影響重大。在氧化鋁及沸石中，形成Al-F各種物種會因為氟原子有強拉電子的性質，使鄰近的羥基質子化，造成布忍斯特酸性增強。然而至今，對於表面上氟離子如何影響觸媒的作用仍未有清楚的輪廓，這有部分原因是因為缺乏精確地証明有關含氟物種的鑑定方法。並且氧或氫氧鋁氟化合物的結構相當多元複雜。經氟化後之氧化物觸媒其酸性位置可能相當複雜並與樣品之製備過程非常相關。雖然在該領域有相當多的研究卻仍對不同氟化試劑扮演導向結構及控制氟化表面之酸度的角色無法釐清，然而鑑定這些氟化物種對於了解這些材料的觸媒活性的增進，因為已有報導指出在氟化過程中，鋁配位環境的改變及氟原子作為配位基的強拉電子性質是這些材料之觸媒酸性與活性改變的主要因素。固態核磁共振技術是研究沸石和催化劑中目前最常使用的方法之一，可是對於氟化物的結構以及氟離子如何與被拔除的鋁原子反應的研究卻是很少。19F核磁共振對於鑑定氟化物是個直接且具高靈敏度的偵測方法。在含氟這種高含量物種的固態樣品中，通常需要高轉速來減小同核與異核的偶極作用力。迄今，19F的化學位移與週遭環境的相互關係還未能充分的了解，特別是異核原子的氟鋁氧化物。氟化物以及脫鋁反應造成的氟化物至今仍未完全了解。因此，本計畫旨在申請具”超高”轉速的魔角旋轉探頭 (轉速> 40 kHz)，利用二維19F和27Al NMR技術來觀察氟化的沸石中27Al的化學環境以及19F在結構中不同位置的化學位移。本計劃中的第二個目標是利用超高轉速的19F NMR技術研究含氟高分子之相結構，超高轉速的19F NMR對於光譜的解析度將會大幅提升使得以往的文獻資料中的馳豫數據更加容易解釋，我們計畫比較各種直接極化與馳豫濾波的技術探討高分子PVDF 與其相關的系統如高分子混合物或複合高分子電解質。 Fluorination is an important treatment for oxide catalysts such as alumina to improve their catalytic activity. Recently, the fluorination has often been used to improve the catalytic properties of the zeolite catalysts. Fluorinating agent and fluorine content have been widely studied and found to have an important impact on the activity of the fluorinated catalysts. The formation of Al-F groups increases the Brønsted acidity of alumina and zeolites probably because of the electronwithdrawing property of fluorine, which increases the protonic character of neighboring hydroxyl groups. There is, however, no definite description of how surface fluorine affects the catalysts-support interaction. This is due, in part, to a lack of a precise identification of the F-containing sites. Furthermore, structural identification is complicated by the rich structural chemistry of the aluminum oxy/hydoxyfluorides. The acid sites of these fluorinated oxide catalysts could be very complex and are very dependent on sample preparation. Despite much work in this field, the role that the different fluorination agents play in directing the structure and controlling the acidity of the fluorinated surface remains unclear. Identification of these fluorinated species is, however, critical to the understanding of the catalytic properties of these materials, since the change in the coordination environment of aluminum on fluorination and the increased electronegativity of fluorine as a ligand are reported to be responsible for the observed modification of the acidity, and thus catalytic activity, of these materials. Solid-state NMR spectroscopy has been one of the most applied methods for the investigation of zeolites and related catalysts. However, few studies have concentrated on the structure of fluoride and how fluoride interacts with the extracted aluminum. 19F magic-angle spinning NMR (MAS NMR) is a direct and sensitive method for distinguishing different fluorine species in fluorinated catalysts. However, it usually requires fast spinning rates to average the large homo- and hetero-nuclei dipolar interactions in solid samples that contain abundant nuclear spins such as 19F. To date, however, no comprehensive correlations between local environments and 19F chemical shifts have been established, making assignment of the different 19F resonances difficult, particularly for heterogeneous aluminum oxyfluoride environments. The nature of the fluorine species and the causes of these dealumination effects are still not fully understood. Thus, the first aim of this proposal is to apply ultrafast MAS (spinning rate > 40 kHz) 19F and 27Al NMR and corresponding 2D NMR methods to establish comprehensive correlations between 27Al local environments and 19F chemical shifts of the different fluorine sites in the fluorinated zeolites. The second aim of our proposal is to characterize the phase structure and polymorphism of fluoropolymers using “ultrafast” 19F MAS NMR. The 19F MAS NMR spectra obtained with ultrafast MAS conditions should give significantly improved quality of 19F MAS NMR spectra and simplify the interpretation of the relaxation data previously reported in the literature. We plan to probe phase structure and location of reverse units in PVDF and related polymer systems by using ultrafast MAS, and to compare the effects of direct polarization with relaxation filters and debate the results in terms of domain selectivity with regard to the reverse units. This study will be further extended to PVDF-based polymer electrolyte systems including polymer blends such as PVDF/PMMA, PVDF/P123 and composite polymer electrolytes with incorporation of nanosized SiO2 and Al2O3 particles. 研究期間：9808 ~ 9907 |
