以Ti-MCM-41與V-Ti-MCM-41分子篩光觸媒同時處理VOCS及NOX之研究

Abstract

本研究係經由水熱法合成含Ti與V之中孔洞材Ti-MCM-41與V-Ti-MCM-41。由於MCM-41材料本身具有大比表面積之特性可作為吸附劑使用，而在植入Ti與V金屬後於紫外光照射下更可達到光觸媒之效果，因此藉此材料可將空氣中的NOx與VOCs等污染物同時去除；不僅可以同時處理兩種污染物質，還改善傳統吸附劑只能吸附而無法去除之缺憾，達到吸附與光催化雙功能的目標。實驗的進行是以連續式反應器測試Acetone與NO之濃度變化情形。吸附測試結果發現，V-Ti-MCM-41(100) 比純Si-MCM-41擁有更佳之吸附效能；而光催化測試結果則顯示，在光照下含有Ti、V之MCM-41材料其不但有吸附Acetone之能力更兼具光催化效能，因此可以延長其單獨作為吸附劑時之處理時間。此外在本實驗條件下，V-Ti-MCM-41(50)具有最佳Acetone與NO處理效能，並同時能將NO2產生量降至最低。 在同時處理Acetone與NO上，研究結果發現當兩者共存時其處理效能高於個別存在時之情況，顯示兩者之間為協同去除之關係。而針對V-Ti-MCM-41(50)探討NO在有無氧氣以及水氣存在下之氧化還原反應，發現在無氧狀態下其處理效能達到40%轉化率，並同時無NO2之產生；而當系統中氧氣含量在5%以上，其轉化率能達到100%，同時卻伴隨NO2之產生，但其總體NOx之處理效能依然能達到70%，因此初步推論即使在有氧環境下，V-Ti-MCM-41(50)光催化NO仍然同時存在著還原與氧化兩種途徑。水氣效應方面，則是發現在一定程度水氣量下對於NO轉化率與NO2之產生量並沒有太大影響。

Ti-MCM-41 and V-Ti-MCM-41 molecular sieves were synthesized by hydrothermal treatment. The synthesized materials were characterized by XED, BET, TEM and XPS. The purpose of this study is the continuous and simultaneous removal of the toxic pollutants like NO and acetone solvent vapors under UV illumination at room temperature over Ti-MCM-41 and V-Ti-MCM-41 materials. Owing to the dual functional characteristic nature of the materials (adsorption/photocatalysis), they could adsorb the pollutants on the surface rapidly and photodecompose the pollutants subsequently. The simultaneous abatement of NO and acetone pollutants were carried out using a continuous flow reactor system under 254nm UV illumination. The adsorption test indicates that V-Ti-MCM-41(100) exhibits higher adsorption capacity than that of Si-MCM-41. Besides, V-Ti-MCM-41(50) exhibits the highest NO and acetone conversion with the lowest NO2 selectivity. It was found that 40% NO conversion was observed without formation of NO2 under the absence of oxygen over V-Ti-MCM-41(50). The obtained results clearly indicate that the NO reduction could be occurred in the absence of oxygen. On the other hand, the conversion of NO was reached ca. 100% under the presence of oxygen. Therefore, it is clear that the both oxidation and reduction of NO could be favored in the presence of oxygen.