雙金屬氧化物磁性觸媒合成並應用於溼式催化氧化甲苯二胺

Abstract

本研究進行磁性微奈米觸媒之改質(Pt/ZrO2/Fe3O4, Pt/ZM)及雙金屬氧化物磁性觸媒(Pt/TiO2-ZrO2/SiO2/Fe3O4, Pt/T-ZSM)的合成，並應用於觸媒溼式催化氧化反應程序(catalytic wet air oxidation, CWAO)處理甲苯二胺(2,4-diaminotoluene, TDA)，進而比較磁性顆粒的添加及不同觸媒對於WAO程序降解TDA及其中間副產物的效能。 本實驗所製備之Pt/ZM及Pt/T-ZSM皆具有優良的比表面積(86.04及111.32 m2 g-1)，其飽和磁化量分別為 13.14及6.08 emu g-1，鉑金屬含量為2.59與1.75 wt. %。經由電子顯微鏡的觀察可知磁性觸媒粒徑皆小於100 nm，且反應前後皆保有超順磁性之特性，顆粒皆能有效的以高梯度磁性分離機加以固液分離並回收。 於溼式氧化反應中可知溫度為主要的操作參數，溫度越高則提供越多的能量降解有機物質。系統中只要提供足夠的氧氣量即可有效降解TDA及其副產物，壓力及轉速之影響小於溫度。 本實驗之水樣體積為500 mL，於WAO系統中反應三小時後，當溫度T = 523 K，氧氣分壓PO2 = 1.38 MPa，轉速Nr = 500 rpm, TDA初始濃度CTDAo = 500 mg L-1時，TDA降解效率(ηTDA)及TOC礦化效率(ηTOC)分別為99與75%。由此可知TDA於高溫氧化的條件下能快速的降解及有效的礦化。在CWAO系統中添加0.5 g Pt/T-ZSM於前條件時，ηTDA及ηTOC分別為99與83%。若觸媒的選擇為0.5 g Pt/ZM時，在相同反應條件下，則ηTDA及ηTOC分別為99與95%以上。有此可知觸媒的添加能有效的降低反應的活化能，增進反應速率對於降解TDA及其中間副產物能提供較佳的催化氧化效果，使得系統能在相同時間獲致較高的礦化效率。以觸媒單位質量Pt之處理效能加以比較時，Pt/T-ZSM與Pt/ZM礦化效率之比為1.29。結果顯示雙金屬觸媒優於單金屬觸媒。

This study focuses on the synthesis of magnetic binary metal oxide catalyst (Pt/TiO2-ZrO2/SiO2/Fe3O4, Pt/T-ZSM) and the modified of magnetic catalyst (Pt/ZrO2/Fe3O4, Pt/ZM). These magnetic particles are used in the catalytic wet air oxidation process (CWAO) for the decomposition of 2,4-diaminotoluene (TDA). The performances for the treatment of TDA via WAO and CWAO systems are investigated. The characteristics of Pt/ZM and Pt/T-ZSM prepared in this work are with BET specific surface areas of 86.04 and 111.32 m2 g-1, saturation magnetizations of 13.14 and 6.08 emu g-1 respectively, contents of platinum on the catalyst surface of 2.59 and 1.75 wt.%, diameters of particles are smaller than 100 nm. Further, the superparamagnetic properties of these catalyst are still held after the use in CWAO process. In WAO system, the dominant operating parameter is temperature (T). The energy supply for the decomposition of contaminants increases with the increasing temperature. To ensure efficient oxidation, of course, the pressure of oxidant (PO2) should be sufficient for the reaction. After three hours reaction time (t) in WAO, as T = 523 K, PO2 = 1.38 MPa, stirring speed Nr = 500 rpm and initial concentration of TDA (CTDAo) = 500 mg L-1,the decomposition efficiency of TDA (ηTDA) and mineralization efficiency of TOC (ηTOC) are 99 and 75%, respectively. It shows that TDA is nearly decomposed at the condition of high temperature with enough oxidant. For the case with 0.5 g Pt/T-ZSM in CWAO, at the same conditions as above,ηTDA and ηTOC are 99 and 83%, respectively. In the same reaction conditions with 0.5 g Pt/ZM, ηTDA and ηTOC are 99 and 95%, respectively. Thus, as the magnetic catalysts are employed in the WAO system, the CWAO process can lower the activation energy of reaction, promoting the reaction rate and giving a higher ηTOC at the same reaction time. Comparing the performances per mass of Pt for the two catalysts, the ratio of values of ηTOC of Pt/T-ZSM to Pt/ZM is 1.29, indicating the oxidation ability of binary metal oxide catalysts Pt/T-ZSM is better than that of single metal oxide catalyst of Pt/ZM.