FTIR偵測二氧化鈦與有毒分子的氣-固相反應

FTIR Study of Gas-Solid Reaction of Toxic Molecules on TiO2

王昱琨(Yu-Kun Wang)

指導教授 ： 蘇昭瑾

國立臺北科技大學/工程學院/有機高分子研究所/碩士(2010年)

摘要

本篇論文主要分為兩個部分，第一部分是甲基碘與改質二氧化鈦的氣固相光催化反應，實驗腔體連接傅立葉紅外線光譜儀，用以追蹤甲基碘與二氧化鈦反應過程及產物。甲基碘與銳鈦礦二氧化鈦反應僅有二氧化碳中間產物訊號，約反應2小時甲基碘全部降解。甲基碘與含氮二氧化鈦光催化反應，中間產物有二氧化碳、甲醛和乙醚，在第14小時甲醛和乙醚吸收峰幾乎消失不見，光催化效果不佳可能是含氮二氧化鈦比表面積較低，或是氮原子取代二氧化鈦上的氧原子導致氫氧基團減少降低催化效率。未含氮二氧化鈦雖然有最大的比表面積，但光催化卻費時20小時，應該是金紅石相比例較高的關係，金紅石相二氧化鈦照光後電子、電洞容易在內部產生再結合，所以可以抵達二氧化鈦表面的電子、電洞較少，光催化效果不佳主要受到晶相影響。
第二部分主要研究奈米金觸媒於室溫下催化一氧化碳實驗，我們使用四氯金酸當作金的前驅物，二氧化鈦作為觸媒載體，利用光沉澱法與沉澱沉積法製備奈米金觸媒，由於沉積上的金粒子小於4奈米所以從X-射線繞射儀結果無法觀察到奈米金的訊號；以X-光螢光分析儀進行元素定性和定量分析，發現我們所製備的觸媒金含量皆超過4重量百分比；以化學分析能譜儀量測得沉澱沉積法所製備的樣品金屬態的金含量96.4 %，氧化態的金含量3.6 %。利用傅立葉散射－反射紅外光譜儀了解室溫下金觸媒催化一氧化碳能力，觀察到一氧化碳吸附於載體後會先形成羰基，在通入氧氣後羰基會轉變為碳酸鹽、碳酸氫鹽和羧酸鹽中間產物吸附在載體上，最後結果得知沉澱沉積法所製備的觸媒，金屬態金含量最高，一氧化碳吸附相(2051 cm-1)訊號較強，此原因使其對一氧化碳催化效果最佳。

關鍵字

甲基碘 ； 二氧化鈦 ； 傅立葉紅外線光譜儀 ； 奈米金觸媒 ； 一氧化碳

並列摘要

The thesis is mainly divided into two parts. The first part is the study of photooxidation of methyl iodie (CH3I) on TiO2. The FTIR was connected with vacuum chamber, which used as study reaction process and products. Photooxidation of CH3I on anatase TiO2 showed that the dissociation of CH3I to generate carbon dioxide as the major products. It took about 2 hours to degrade completely. Photooxidation of CH3I on N-doped TiO2, the intermediates are CO2(g)、CH2O(g)、and (C2H5)2O. After 14 hours, CH2O(g) and (C2H5)2O almost disappeared. The reason of the slower decomposition rate of CH3I on N-doped TiO2 is due to the smaller surface area based on the BET measurement or substitution of oxygen atom by nitrogen atom on TiO2 caused decrease of hydroxyl group. Although undoped N-TiO2 has the largest surface area, but the photooxidation took about 20 hours. The main reason for the slowest decay rate is the existence of rutile crystal phase.
The second part of the thesis is the study of TiO2-supported gold catalysts for CO oxidation at ambient temperature. Gold catalysts were prepared by photo-deposition method and deposition-precipitation method using HAuCl4 as the gold precursor. TiO2 DP25 was chosen to be the substrate in this study. No distinct gold peaks were observed on XRD patterns, because the gold size was less than 4 nm. The amount of gold in the samples was over 4 weight percent characterized by XRF. The ESCA result showed that the catalysts prepared by deposition-precipitation method contained metallic gold about 96.4 %, and nonmetallic gold about 3.6 %. The DRIFT technique was applied to analyze the interaction of CO over Au-TiO2 catalysts at room temperature. CO adsorbed on Au-TiO2 leading to carbonyl species. Carbonate、monodentate and carboxylate species were discovered as intermediate species in this catalysis. In addition, the higher composition of metallic gold exists in a sample, the better performance can be achieved for CO oxidation.

並列關鍵字

Methyl iodide ； Titanium Dioxide ； Fourier-Transform Infrared Spectroscopy(FT-IR) ； gold nanoparticle catalyst ； carbon monoxide

參考文獻

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