以可見光觸媒/中孔洞沸石複合材料同時處理VOCs與NOx之可行性研究

Abstract

二氧化鈦光觸媒因其可利用太陽光源，因此廣受各界注目，然而其應用最 大之限制為其光催化效率過低，相對的吸附材之優點為其除污速率高，但一旦吸 附材飽和了，就無法再達到原有之除污效果。因此若能結合吸附材與光觸媒則可 以兼具兩者之優點，先將污染物吸附在吸附材上，再進行光催化分解。除此之外， 當單獨以光觸媒進行空氣污染物如VOCs 及NOx 之去除時，其光催化反應均為 氧化分解，此在氧化NOx 時會形成HNO3，其不僅更危害人體健康，也將造成 觸媒表面之毒化，因此如何有效的將NOx 還原為N2 與H2O 為一重要之室內/大 氣污染防制課題。 本計畫即擬以三年期間，完成金屬摻雜沸石/氮摻雜可見光觸媒之長效複合 材料之製備，並將之應用於VOCs 之氧化與NO 之還原，以達同時處理多種空氣 污染物之目標。在第一年之研究中將以液相法製備不同中孔洞沸石型吸附材與光 觸媒複合環保材料，並探討比較其在紫外光下之VOCs 及NOx 處理效果; 第二 年之計畫則將嘗試摻雜(或含浸) V, Cu 等金屬於中孔洞沸石型吸附材與光觸媒複 合環保材料中，以瞭解其在紫外光甚至可見光下處理VOCs 及NOx 之效果; 在 找出最佳之V, Cu 金屬沸石型吸附材與光觸媒之組合後，第三年之計畫將改以氣 相法更有效率、更具量產性的製備氮摻雜(N-doping)之光觸媒沸石複合材料，並 探討比較其在紫外光與可見光下同時處理VOCs 及NOx 之效果，以及進行其量 產之可行性與成本效益分析。

Photocatalysts such as titania has attracted wide attention due to its ability of utilizing solar energy. However, its photocatalytic activity is so low that a high reactor residence time is usually required. On the other hand, adsorbents such as the mesoporous zeolite materials have the advantage of fast adsorption efficiency but the removal efficiency of pollutants decays rapidly once it reaches saturated capacity. Therefore a combination of the two materials can thus provide a better way of achieving high pollutant removal efficiency within short reaction time and lasting for a longer duration. Furthermore, the removals of both VOCs and NOx are via photo-oxidation reactions when titania is used alone. This is sufficiently good for removing VOCs since its end products are CO2 and H2O, but the oxidation product of NOx is HNO3 which is not only a hazardous pollutant but also a poison material to the catalyst. In this three-year study, it is intended to synthesize the metal doped-zeolite/ N-doped titania composite materials which can serve as a catalytic adsorbent for the simultaneous removals of VOCs and NO. In the first year project mesoporous zeolite/titania composite will be synthesized via a sol-gel method. The removals of VOCs and NO will be tested in a batch UV photocatalytic reactor. In the second year study the metals of V and/or Cu will be doped or impregnated into the mesoporous zeolite-titania composite to evaluate if they can improve the photocatalytic activity for removing VOCs and NOx under UV or even visible light sources. After obtaining the best composite material of the photocatalytic adsorbent, the third year project will then switch to the gas phase synthesis of the photocatalytic adsorbent. The main purpose of the gas phase synthesis is to be able to efficiently dope nitrogen atoms into photocatalyst so that it can utilize visible light source. In addition, the mass production and the cost effectiveness of the catalytic adsorbent will be more feasible.