Ce/Zr物质的量比对Ru/CexZr1-xO2催化剂的性质及其湿式氧化苯酚性能的影响

Effect of Ce/Zr molar ratio on the catalytic performance of Ru/CexZr1-xO2 in the wet air oxidation of phenol

    摘要
  • 摘要: 采用溶胶凝胶法制备了系列不同Ce/Zr物质的量比的Ru/CexZr1-xO2催化剂，通过X射线衍射（XRD）、氮气吸附-脱附、拉曼（Raman）光谱、储氧能力（oxygen storage capacity，OSC）、热重（TG）以及吡啶红外（Py-FTIR）等手段对其进行了表征，考察了该催化剂在湿式氧化苯酚反应中的性能。结果表明，ZrO2可与CeO2形成固溶体；随着ZrO2掺杂量的增加，CexZr1-xO2固溶体的OSC值增大。相比于CeO2，掺杂ZrO2后催化剂表面的L酸量明显增多。催化剂湿式氧化（catalytic wet air oxidation，CWAO）性能与OSC和表面酸性均有密切的关系：催化剂表面的L酸有利于苯酚氧化生成CO2，而OSC过高会导致催化剂表面积炭，使催化剂失活。当ZrO2掺杂量为25%时，在160℃、2 MPa纯氧条件下，催化氧化苯酚5 h后，苯酚转化率和总有机碳（total organic carbon，TOC）去除率分别为100%和99%，说明该催化剂具有优异的苯酚氧化性能。

     

    Abstract: A series of CexZr1-xO2 catalysts with different Ce/Zr molar ratios were prepared by sol-gel method and characterized by X-ray diffraction (XRD), nitrogen sorption, Raman spectra, oxygen storage capacity (OSC), thermogravimetry (TG) and pyridine adsorption infrared (Py-FTIR) spectra; the performance of CexZr1-xO2 in catalytic wet air oxidation (CWAO) of phenol was investigated. The results demonstrate that CexZr1-xO2 solid solution is formed by doping ZrO2 in CeO2 and the OSC value of CexZr1-xO2 increases with an increase in the content of ZrO2. In comparison with pure CeO2, CexZr1-xO2 solid solution has more Lewis acid sites. The catalytic activity of CexZr1-xO2 is related to both OSC and surface acidity; the Lewis acid sites are favorable for the complete oxidation of phenol, whereas high OSC may promote the carbonaceous deposition that leads to catalyst deactivation. The Ru/Ce0.75Zr0.25O2 catalyst exhibits high activity in phenol oxidation; after reaction for 5 h at 160℃ and 2 MPa O2, phenol conversion and total organic carbon (TOC) rate reach 100% and 99%, respectively.

     

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