Frequency Response Method for the Study of Kinetics of a Heterogeneous Catalytic Reaction of Gases

Article abstract of DOI:10.1021/j100357a032

A new frequency response method is proposed on the basis of actual data on C3H6 + H2 -> C3H8 over Pt/Al2O3 at 273 K observed under each partial pressure of ca. 10 Pa: the gas space of a continuous-flow reactor was varied sinusoidally, and every partial pressure variation induced was followed by a mass spectrometer.Both amplitude and phase difference of ΔR observed in the angular frequency region from 40 to 60 rad/min were described well by <*>, where R_s and P_H^(s) denote the overall reaction rate and the partial pressure of H2 at the steady state before the oscillation and <*> is the time derivative of the pressure variation, dΔP_H/dt.The "rate constant" n and κ were 0.15 and 7 * 1E-2 min, respectively.The unordinary rate equation involving P_H was interpreted by R = ?_dμ_d in terms of the driving force or the free energy drop, μ_d, and the frequency factor, ?_d, at the rate-limiting step; Δ?_d/?_d = nΔP_H/P_H^(s) and <*>.The newly derived rate constant κ seemed to decrease with increasing temperature.The turnover frequency could be given by n/κ.