Preparation Of Catalyst With ZrO₂ As Support And Its Enhanced Catalytic Performance Of CO

Carbon monoxide is one of the major air pollutants, and its massive emission has caused severe environmental pollution. The catalytic oxidation of carbon monoxide plays an important role in control of automotive emission and theory research, at the same time, the catalytic oxidation of carbon monoxide is an important model reaction in catalyst study. The catalysts used for elimination of CO at low-temperature are noble metals such as Au, Pd, Pt, Ru etc., and the noble metal catalysts show high activity and long-life time; however the inadequate reserves and the high price restrict the widespread applications. The transition metals are in rich resource, low cost, at the same time, the oxidates of these transition metals have high catalytic activity on CO, and so they have great applications on CO catalytic oxidation.As we all known that, ZrO₂ is the only one that has the characteristics of acidity, basicity and at the same time redox in the surface, at the same time, it is a p-type semiconductor, which is easy to produce oxygen hole, and it can produce a strong interaction with the active component as a catalyst carrier. So ZrO₂ is good catalytic and support material.In this paper, the zirconia and yttria-stabilized zirconia were prepared by sol-gel method coupled with supercritical CO₂ fluid-drying technology. And the as-prepared zirconia and yttria-stabilized zirconia were used as support, ultrasonic-precipitation method and impregnation methods were used to preprare catalysts which supported different metals, such as CuO/ZrO₂,CuO/ZrO₂(Y₂O₃),Mn/ZrO₂(Y₂O₃),Co/ZrO₂(Y₂O₃),Ln/ZrO₂(Y₂O₃), and the catalytic oxidation of CO was investigated on these catalysts in details.The main contents of this thesis are listed as follows:1. Ultrafine zirconia and yttria-stabilized zirconia powders with no agglomeration and high specific surface were prepared using ZrOCl₂·8H₂O as precursor, urea as precipitant and yttria as stabilizer by sol-gel method coupled with supercritical CO₂ fluid-drying technology. The particles were characterized by XRD, TG-DTA, BET, FT-IR and TEM. The specific surface of ZrO₂ calcined under 400 oC is 85 m²/g, and the main phases of the sample is monoclinic phases and contain part of tetragonal phases; however, the yttria- stabilized zirconia calcined at 400 oC shows tetragonal phases, and its specific surface is as high as 120.25 m²/g.2. We used as-prepared ZrO₂ as support and ultrasonic-precipitation method to prepare the catalyst CuO/ZrO₂. The catalytic oxidation of CO results show that the catalyst supported 12%CuO has the highest activity, the light-off temperature is 149 oC, the temperature of total conversion of CO is 162 oC. At the same time, the light-off temperature of 12%CuO/ZrO₂(Y₂O₃) is 126 oC, the temperature of total conversion of CO is as low as 152 oC.3. We used impregnation method to prepare Mn/ZY, the results show that the 12%Mn/ZY calcined under 350 oC have higher catalytic activity. The temperature of 100% CO conversion is 142 oC; the light-off temperature of (12%CuO/12%Mn)/ZY is 56 oC, the temperature of 100% CO conversion is 82 oC, CuO and Mn show high synergistic effect.4. We used yttria-stabilized zirconia to support Co and prepared a series of catalysts Co/ZY, and investigated the effection of calcine temperature, the contents of supported Co etc. The results show that the 8%Co/ZY calcined under 200 oC and pretreated at 300 oC has the highest catalytic activity, the T₉₅ is as low as 113 oC and the sample exhibits both good cycling stability and excellent long-term stability.5. We prepared a series of catalysts supported Ln in the aim of investigateing the promote effection of the rare earth metals. The results show that the CeO₂ can promote the catalytic activity of the catalysts within a certain range.