C-13 KINETIC ISOTOPE EFFECTS IN THE CATALYTIC-OXIDATION OF CO OVER AG

The C-13 kinetic isotope effects in the catalytic oxidation of carbon monoxide over silver wool were found in the temperature range 343-453 K with the following temperature dependence: 100 ln(k(12)/k(13)) = (3. 398-630/T) +/- 0.083. A reaction CO/O-2 gas mixture of 1:2 ratio was u sed in a static system with initial pressures ranging from 20 to 40 kP a. Under these conditions the reaction obeys the rate law dP(CO)/dt = -k(1)P(CO) and has an apparent activation energy of 59.3 +/- 1.7 kJ mo l(-1). In our theoretical interpretation, based on Bigeleisen's formal ism, various geometries of (CO2)double dagger were applied as transiti on states of the rate determining step, and only a (CO2)double dagger with an interbond angle of 110 degrees and stretching force constants of 1700 and 1000-1400 N m(-1) could explain the experimental results.