Pt-Ir/C/PTFE疏水催化剂及交换效率研究

【作者】 梁宏伟；

【导师】 桑革；

【作者基本信息】 中国工程物理研究院北京研究生部 ， 核燃料循环与材料， 2003， 硕士

【摘要】 本论文用湿浸法和分步湿浸法研制了8种Pt（Ir）／C／PTFE疏水催化剂。用TEM、SEM、XRD分析技术对疏水催化剂的表面形貌、活性组分分布及物相进行分析，结果表明：活性组分较均匀地以颗粒状负载在载体上，平均粒径为0.03μm。 用AUTOSORB-1-C吸附仪对疏水催化剂的比表面积、孔体积及孔径分布进行分析，结果表明：疏水催化剂中Pt：Ir=3：1时，其比表面积最大，活性组分仅为Ir的催化剂比表面积最小；疏水催化剂的脱附、吸附平均孔径均在18.0±0.21（?）范围之内。 研究了8种疏水催化剂在323K温度下气-液对流、气汽并流、气汽-液对流的氢-氘同位素交换实验。结果表明：（1）在同位素催化交换过程中若将液体雾化则催化剂的催化活性比纯的气液对流方式高近10倍；（2）在Pt／C／PTFE疏水催化剂中加入Ir，当Pt：Ir=3：1时，疏水催化剂的催化活性在所研制的催化剂中催化活性最高；（3）比表面积大的疏水催化剂其催化活性也高，即疏水催化剂的催化活性随其比表面积的增大而增加。 研究了温度、压力对疏水催化剂氢同位素交换时交换柱上部排出的HDO摩尔量的影响。结果表明：在选择催化交换温度时须考虑压力条件。用疏水催化剂分别在五种不同温度下进行氢同位素交换实验，结果表明催化活性在313～333K之间变化不大，但当温度降低到305K或增加到343K时活性明显降低。 研究了不同氢气流速对疏水催化剂氢同位素交换实验结果的影响。结果表明：随氢气流速从2.381·min^-1增加到6.381·min^-1，催化剂的催化活性增加较快，从6.381·min^-1增加至9.381·min^-1，催化活性的增加就逐渐缓慢下来。更多还原

【Abstract】 The preparation of eight hydrophobic catalysts of Pt（Ir）/C/PTFE by dipping method in single and multiple steps respectively has been described in this thesis. The species with their distribution of the active elements （Pt or Ir）, and the topography on the surface have been investigated by transmission electron microscope（TEM）, scanning electron microscope（SEM） and X-ray diffraction（XRD）. Results indicate that the active elements were deposited on the carrier homogenously, and that the average diameter of the particles is 0.03μm.The specific surface area, total pore volume and average pore radius have been determined using an adsorption meter. A maximum specific area for the catalyst was obtained when the ratio of Pt/Ir is 3:1, but it becomes the smallest when the active ingredient is Ir without Pt. The average aperture on the adsorption or desorption is 18.0±0.2lA.The hydrogen isotope exchange reaction kinetics between deuterium-enriched water and hydrogen gas have been tested for the eight hydrophobic catalysts beds with the gas-liquid countercurrent gas-vapor co-current gas/vapor-liquid countercurrent modes, respectively. Results indicate that the mass transfer coefficient K_ya in the co-current mode is approximately one order of magnitude greater than that in the gas-liquid （without vapor） countercurrent mode, and that Pt-Ir/C/PTFE hydrophobic catalyst with the ratio of Pt /Ir as 3:1 can increase the catalytic activity obviously, and that the catalytic activity increases with the increasing of the specific surface area.The effects of the temperature and pressure on the mole fraction of HDO in the top segement of the column have been examined for the hydrophobic catalyst. Results indicate that the selection of the optimum temperature for the exchange effect depends on the column pressure. The exchange efficiency on the hydrogen isotopes exchange has been examined for the hydrophobic catalysts at different temperature. The result indicates that the catalytic activities keep steady between 313K and 333K, and decrease obviously when the temperature is below 305K or above 343K.The effect of the flow rate of hydrogen gas within the column on the efficient of the hydrogen isotope exchange has been studied for the hydrophobic catalyst. Results indicate that the catalytic activity increases rapidly with the increasing of hydrogen flow rate from 2.38 to 6.38 1 min^-1, but the increase becomes very slowly as the flow rate increases from 6.38 to 9.38 1 min^-1更多还原