.pt-ir/c/ptfe Hydrophobic Catalyst And Exchange Efficiency Study

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...