Steady-state Flow Method Research Articles

TRANSIENT RESPONSE METHOD IN HETEROGENEOUS CATALYSIS

Abstract The steady-state flow method has been widely used in the kinetic study of heterogeneous catalysis. Under the conditions of steady state, all elementary steps in series are progressing at the same rate and hence the measured rates hardly tell the precise kinetic structure, or mechanism, of catalytic reactions which usually consist of several elementary steps including adsorption of reactants, surface reaction, and desorption of products. In the kinetic analyses of any given reactions, it is a common practice for the investigator to postulate a number of suspected rate models and then to assess these models to verify a optimal one which best fits observed rate data. Usually, however, there are quite a large number of plausible rate models even for a rather simple reaction, and it is not easy to determine the most adequate model among others even with the help of mathematical model indentification techniques with a electronic computer. This method is based on the assumption that there is a best mode...

Vapour pressure of isotopic solids by a steady flow method: Argon between 72 °K and triple point

A steady state flow method was devised to measure the single stage separation factor in the solid-vapour equilibrium. The method was applied to the36A-40A solid system and found to work satisfactorily. The logarithm of the separation factor was found to depend linearly from 1/T2 within the experimental errors, ranging from 0.0104 at 72 °K to 0.0072 at triple point. This linear dependence is in agreement with the current theories of small quantum effects on thermodynamic systems. Using Bigeleisen’s formulation of the theory and taking into account anharmonic effects, the value of the mean square frequency of the lattice harmonic vibrations in solid argon is derived; this value agrees satisfactorily with specific heat measurements. The difference in triple point temperatures of40A and36A is derived from the measurements and found to be 0.0435 °K.

Temperature dependence of the binary diffusion coefficient of gases

AbstractThe variation with temperature of the binary gas diffusion coefficient for the gas pairs N2 ‐ H2 and NH3 ‐ H2 is reported for the temperature range of 0°–300°C. The data were obtained using a steady state flow method, and the apparatus and experimental conditions relative to this technique are discussed. Although this method does not give absolute values of the diffusion coefficient, it is relatively simple and accurate.The extent of agreement of the data with equations for the prediction of gas diffusion coefficients is shown. Better results are obtained when these equations are applied to nearly ideal systems, such as the N2 ‐ H2 pair, rather than to gases which have highly polar molecules such as NH3.