以光纖反應器直接光催化分解氮氧化物

Abstract

為減少由車輛及內燃機產生的廢氣，本研究目的為以光纖反應器去除氣相中污染物NOx，模擬工廠鍋爐尾氣的溫度，成份等參數做一試驗性質的評量，以達到減少環境污染的目的。為區分各觸媒分解NOx的光催化活性，在以批式之方法試驗觸媒後，TiO2觸媒膜覆於光纖上進行流動系統的反應。觸媒的製備以熱水解法製備含銀之二氧化鈦覆膜液，以浸漬覆膜法覆膜0.1mm外徑之光纖。由SEM之檢測，光纖表面鍍膜之TiO2觸媒層約爲54nm，Ag/TiO2之觸媒則約為44nm的厚度，以紫外-可見光吸收光譜偵測，吸收位置大約在350nm附近。本研究之流動系統改變光強度、氧濃度、溫度等參數並以初濃度為246ppm之NOx，通入可容納117根光纖之光纖反應器，滯留時間為64分鐘，達平衡後打開紫外光源並持續照光數小時;產物流以NOx分析儀器偵測氣相NOx、NO、NO2濃度的變化，實驗發現，光強度提升去除效率隨之增加。含銀0.5wt%之TiO2觸媒於光強度6W/cm2，氧氣9%體積分率，溫度160℃可得本實驗系統最好之去除效率5.22%。

To reduce the emissions of NOx caused by traffic emissions and internal combustion engines, the NOx removal using photoreactor has been investigated. An optical fiber photoreactor was studied for the photodecomposition of NOx under a steady state flow system. A batch also was performed to classify photocatalytic efficiency of different catalysts for decomposing of NOx. Based on the batch data, the TiO2-coated optical fiber photoreactor was built and studied in order to optimize different parameters such as temperature, O2 volume ratio and light intensity. Hence the optical fiber reactor may achieve a practical removal of the NOx. The titanium oxide sol for dip-coating on the optical fiber was prepared according to the procedures of modified hydrothermal synthesis previously. The thickness of the TiO2 and Ag/TiO2 film prepared by modified hydrothermal method on an optical fiber were about 54nm and 44nm estimated by SEM, respectively. The UV-vis spectra showed that pre-edge of adsorption peak located at about 350nm. In the photocatalytic reaction, the concentration of NOx reactant gas was 246ppm and the retention time was about 64min. A NOx analyzer was used to measure the NO, NOx, and NO2 concentrations. After reaching steady state, UV irradiation was turned on and continued for several hours. The experimental data revealed that the removal of NOx was found to increase as the intensity of the incident light intensity increased. The optimal catalyst and reaction conditions were observed at the 0.5wt%-Ag/TiO2 catalyst and a reaction temperature 160℃. The conversion of NOx was 5.22%.