A room-temperature reactor packed with hydrophobic catalysts for the oxidation of hydrogen isotopes released in a nuclear facility will contribute to nuclear safety. The inorganic-based hydrophobic Pt catalyst named HIP has been developed especially for efficient oxidation over a wide concentration range of hydrogen isotopes at room temperature, even in the presence of saturated water vapor. The overall reaction rate constant for hydrogen oxidation with the HIP catalyst in a flow-through system using a tritium tracer was determined as a function of space velocity, hydrogen concentration in carriers, temperature of the catalyst, and water vapor concentration in carriers. The overall reaction rate constant for the HIP catalyst in the range near room temperature was considerably larger than that for the traditionally applied Pt/Al(2)O(3) catalyst. Moreover, the decrease in reaction rate for HIP in the presence of saturated water vapor was slight compared with the reaction rate in the absence of water vapor due to the excellent hydrophobic performance of HIP. Oxidation reaction on the catalyst surface is the rate-controlling step in the range near room temperature and the rate-controlling step is shifted to diffusion in a catalyst substratum above 313 K due to its fine porosity. The overall reaction rate constant in the range near room temperature was dependent on the space velocity and hydrogen concentration in carriers. The overall reaction rate constants in the range of 1,000/T greater than 3.2 correlated to k(overall) [S(-1)] = 5.59 x 10(7) x SV[h(-1)] x exp (- 67.7[kJ/mol]/R(g)T), where the space velocity range was from 600 to 7,200 h(-1).
Times Cited: 4 IWAI, Yasunori/G-3773-2011 4