CeO_2-ZrO_2固溶体在催化湿式空气氧化苯酚废水中的作用

Crucial role of CeO_2-ZrO_2 solid solution in catalyzing wet air oxidation of phenolic wastewater

采用共沉淀法制备了CuO/ZnO/Ce O_2、CuO/ZnO/ZrO_2和CuO/ZnO/Ce O_2-Zr O_2催化湿式空气氧化苯酚废水催化剂,并采用N_2吸附-脱附、X射线衍射(XRD)、X射线光电子能谱(XPS)、程序升温还原(TPR)、N_2O滴定和电感耦合等离子体原子发射光谱等手段对催化剂进行了表征.结果表明,CuO/ZnO/Ce O_2-Zr O_2催化剂表现出最佳的催化性能.在200℃、2 MPa空气、苯酚初始浓度500 mg·L^(-1)的条件下,COD去除率为96.5%.XRD表明Ce O_2-Zr O_2复合氧化物载体以Ce_xZr_(1-x)O_2固溶体形式存在,增加了催化材料的储放氧能力.XPS表明Ce^(3+)和Ce^(4+)在催化剂表面共同存在,协调了氧化还原过程.TPR表明催化剂的还原性对催化剂的氧化活性起到至关重要的影响.由于CuO/ZnO/Ce O_2-Zr O_2催化剂活性组分和载体间的强相互作用,处理后的水样未发现金属离子,进而有效的提高了催化剂的稳定性和避免了对水样的二次污染.

The CuO/ZnO/Ce O_2,CuO/ZnO/Zr O_2 and CuO/ZnO/Ce O_2-Zr O_2 catalysts were prepared by a co-precipitation procedure and employed in catalyzing wet air oxidation of phenol in bath reactor. The catalysts were characterized in forms of N_2adsorption-desorption,XRD,XPS,H_2-TPR,N_2 O titration and ICP-AES. The results showed that the CuO/ZnO/Ce O_2-Zr O_2 catalyst exhibited the best catalytic activity. As the initial concentration of phenol was 500 mg·L^（-1）,the COD removal was 96.5% after 4 h at 200 ℃ and 2 MPa air. The XRD experiment showed that the Ce O_2-Zr O_2 compound oxide support existed in the form of Ce_xZr_（1-x）O_2 solid solution,which mainly increased oxygen storage capacity. The characterization with XPS experiment confirmed that the Ce^（3＋）and Ce^（4＋）both existed on the catalyst surface which could coordinate the oxidation-reduction process. The relationship between the catalytic activity and reducibility revealed that the redox properties were significant in calculating the catalytic activity in CWAO reaction. Moreover,there was very low metal iron leaching due to the strong interactions between active component and support,which was beneficial to the catalytic stability and suppressed the secondary pollution.