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《中国石油和化工标准与质量》2014,(3)
随着汽车数量的不断增加,汽车尾气的排放量也在不断的增多。CexZrl-xo2由于自身的抗高温性能、良好的老化性能、储氧能力较高以及低温还原性能等优势,是现代新一代三效催化剂材料中的重要组成部分,其对于处理汽车尾气具有十分重要的作用。因此,本文针对铈锆复合氧化物的制备方法进行详细的分析。 相似文献
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微波辐射铈锆固溶体催化合成乙酸丁酯的研究 总被引:1,自引:0,他引:1
在微波辐射条件下,以铈锆固溶体为催化剂,用乙酸和丁醇为原料合成乙酸丁酯,考察了微波辐射功率、反应时间、催化剂用量、乙酸丁醇比等对乙酸转化率的影响,并与常规加热法进行了对比。所确定的最佳反应条件为:在中高火条件下,醇酸摩尔比为1∶1,加入Ce0.6Zr0.4O20.5 g,反应15 m in,此时乙酸的转化率为64.1%,比传统加热法(反应4 h,转化率62.2%)反应速度大大加快,且转化率高。 相似文献
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采用共沉淀法制备了CexZr1-xO2固溶体作为催化剂载体,采用柠檬酸络合法将镍负载于CexZr1-xO2载体上得到Ni/CexZr1-xO2催化剂,利用X射线衍射(XRD)、N2吸附-脱附(N2-BET)、程序升温脱附(TPD)、程序升温还原(TPR)等技术对催化剂进行表征,在常压微型固定床反应器上测试了CO2甲烷化的性能,考察了n(Ce)/n(Zr)、镍含量对催化性能的影响。研究发现制备的催化剂具有优异的活性,在常压和空速15 000 mL·g-1·h-1条件下,反应温度200℃时,12% Ni/Ce0.25Zr0.75O2催化剂(负载量为质量分数,下同)CO2的转化率达74%,CH4选择性为100%。12% Ni/Ce0.25Zr0.75O2催化剂300 h的稳定性测试结果显示其具有较高的抗烧结性能。催化剂的优异活性归因于采用了新的负载方法--柠檬酸络合法负载活性组分镍,该法实现了镍的高分散和催化剂的大的比表面积。 相似文献
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铈锆固溶体CexZr1-xO2上H2S的选择性催化氧化性能 总被引:1,自引:0,他引:1
采用共沉淀法合成一系列具有不同Ce/Zr物质的量比的铈锆固溶体CexZr1-xO2,考察Ce/Zr比例对H2S选择氧化反应催化活性的影响。通过XRD、BET、Raman、XPS、CO2-TPD、O2-TPD、H2-TPR等手段对铈锆固溶体的晶体结构、表面性质、碱性位以及氧化还原性等进行表征。结果表明,所有的铈锆固溶体催化剂均可以在化学计量比的氧气下具有优良的低温催化活性,催化活性随着Ce/Zr比例的提高而增加,其中Ce0.9Zr0.1O2活性最高,(160~260) ℃转化率均保持在95%以上,在180 ℃时硫收率可达到97%,这主要是因为Ce0.9Zr0.1O2具有最多的中度碱性位、活性位数量和强的氧化还原性。同时推测Ce4+为催化反应的活性位,并遵循氧化还原机理。此外,催化剂的失活主要是由于催化剂表面生成硫酸盐物种,消耗了活性组分Ce4+。 相似文献
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纳米级铈锆氧化物固溶体在催化剂中的应用 总被引:1,自引:0,他引:1
对以铈锆氧化物固溶体Ce0.75Zr0.25O2为助剂的催化剂进行了活性评价.实验结果表明:固-固化学反应法制备的Ce0.75Zr0.25O2固溶体与传统的共沉淀法制备的Ce0.75Zr0.25O2固溶体在三效催化剂中作为催化助剂的作用是相当的,对模拟汽车尾气起到了很好的净化作用.还研究了Ce0.75Zr0.25O2对交联粘土(PILC)催化剂Cu/CeTi-PILC的丙烯选择性催化还原一氧化氮反应的影响.实验证明:Ce0.75Zr0.25O2固溶体能提高催化剂5%Cu/CeTi-PILC对C3H6和一氧化氮的催化活性,起燃温度明显降低,其中C3H6起燃温度降低了15℃;一氧化氮起燃温度降低了112℃. 相似文献
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The formation of solid solutions between tin cations and mullite by calcination at 1400°C of amorphous precursors prepared by pyrolysis of aerosols is reported. The oxidation state of the tin cations and the position that they occupy in the mullite structure have been analyzed using XAS (XANES and EXAFS) spectroscopy, which shows that the tetravalent tin cations are located at the octahedral positions of the Al3+ ions, which induces cell expansion. The limit of tin incorporation under the experimental conditions reported here correspond to a tin/mullite mole ratio of ∼5%, which is within the range previously reported for other tetravalent cations (4%–6%). 相似文献
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Koichiro Fukuda Hiroyuki Taguchi Tetsuya Fukuda 《Journal of the American Ceramic Society》2002,85(7):1804-1806
Five types of Ca2 SiO4 solid solutions, doped with either P5+ , Ge4+ , Fe3+ , Mg2+ , or Ba2+ , were prepared and examined by high-temperature X-ray diffractometry up to 800°C. The starting and finishing temperatures were determined for the α'L -to-β martensitic transformation during cooling and the reverse (β-to-α'L ) transformation during heating. These four types of transformation temperatures for the preparations doped with either P5+ or Ge4+ steadily decreased with increasing substituted fraction. The effect of the substitution on the decrease for each transformation temperature was quantitatively evaluated by Δ T / x , where Δ T is the difference in the transformation temperatures between the solid solutions and pure Ca2 SiO4 , and x represents the fraction substituted for Si4+ or Ca2+ in the α'L -phase structure. The evaluated value for the substitution of P5+ was more than 3 times that of Ge4+ . The effect of the substituent ions mentioned above, together with Na+ and Sr2+ , on the lowering of the starting temperature of the α'L -to-β transformation was principally determined by the differences in the ionic radius between the interchanging cations. 相似文献
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以堇青石为载体担载固体酸催化剂活性组分,以乙酸与乙醇合成乙酸乙酯的反应为模型反应,考察多种制备条件对堇青石担载固体酸催化剂酯化活性的影响,筛选最佳制备工艺. 结果表明,固体酸颗粒悬浊液性质均一、稳定,浸渍液中添加g-Al2O3或聚乙二醇会阻碍催化剂表面活性的发挥. 以悬浊液为浸渍液,1 mol/L H2SO4溶液达50%(j)的工艺条件下,堇青石担载固体酸催化剂酯化活性最高. 堇青石表面担载的固体酸是酯化活性中心,全回流反应100 min,乙酸的转化率达到79.2%,二次利用时转化率为一次转化率的95.6%. 堇青石担载固体酸催化剂制备工艺的平行性和稳定性较好,催化剂外形规整,孔道均匀整齐,在保持高活性的同时,达到催化剂成型和提高酯化催化剂经济性的目的. 相似文献
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含Ce_xZr_(1-x)O_2固溶体三效催化剂的制备及性能研究 总被引:5,自引:0,他引:5
用共沉淀技术在室温、pH =10 0的条件下制备出了CexZr1-xO2 固溶体 ,将其用于Pd基三效催化剂的制备 ,对催化剂的性能进行了评价 ,结果表明 :和纯的CeO2 相比 ,含CexZr1-xO2 固溶体的催化剂具有较高的催化性能 ,其中Pd/Ce0 6Zr0 .4 O2 催化剂性能最佳 ,HC、CO、NO的转化率在A/F =14 6时分别为 97 33%、89 5 2 %、10 0 %;新鲜催化剂的起燃温度分别为 186、180、185℃ ,高温处理后起燃温度分别为 2 49、2 41、2 46℃。 相似文献
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Masatomo Yashima Nobuo Ishizawa Masahiro Yoshimura 《Journal of the American Ceramic Society》1992,75(6):1541-1549
Oxygen vacancies can be introduced into zirconia solid solution ZrO2 –MO u ( u = 1 and 1.5) to maintain electroneutrality. Recently, the local structures around Zr4+ and M2 u + ions in ZrO2 –MO u solid solutions have been studied through EXAFS spectroscopy, diffuse scattering analysis, and single-crystal structure analysis. The present study constructs an ion-packing model for zirconia solid solutions based on some defect cluster models. The decrease of cell volume with the occurrence of vacancies is assumed to be expressed by decreasing the coordination number (CN) of cations around the vacancy. The distribution of CNs in a solid solution was calculated from a certain defect cluster model. The average interatomic distances, the average CN, and the short-range order parameters were calculated using this distribution of CNs. The local structures calculated from the model were compared with experimental data in the systems ZrO2 –MO1.5 (M = Y, Gd, Yb, and Ca). In the ZrO2 –YO1.5 system, the r (s–O) interatomic distance, where s represents Zr4+ or Y3+ and O represents O2− , decreased with Y content and therefore vacancy content. The probability of finding Y3+ around a vacancy increases with increasing yttria content from a comparison of the calculated results with the ones from recent EXAFS studies. The present model can qualitatively explain compositional and size dependences of the dopant on various local structures. 相似文献