Pore-surface diffusion model isothermal micropore

Isothermal Micropore and Pore-Surface Diffusion Models. 317... 

The mass transfer coefficient can be calculated as the ratio of the estimated values of Op and Tp. 2, Isothermal Micropore and Pore-Surface Diffusion Models... 

The expressions for the FRFs for the isothermal micropore and pore-surface diffusion models were obtained for constant diffusion coefficients. If this assumption is not met, that is, if the concentration dependence of the diffusion coefficient has to be taken into account, the value estimated from the maximum of the — Imag(Fi p(diffusion coefficient corresponding to the steady-state concentration. 

Note that these equations are simplified versions of the general model and based on an efifeetive diffusion eoefficient which is dependent on the slope of the adsorption isotherm. Principally speaking, the general model based on the material balance and all mass transfer resistances (concentration boundary layer around a pellet, macro and micropore diffusion, sometimes surface diffusion and laminar pore flow) has to be solved. 

Our library contains FRFs for four simple isothermal mechanisms Langmuir kinetics, film resistance model, micropore diffusion, and pore-surface model. For each mechanism, a short description with the model equations is given, together with the expressions for the first-order FRF Fx p(w), and two second-order FRFs, F2,pp(w, w) and F2,pp(w, —[Pg.293]

Fig. 1(a) shows N2 adsorption and desorption isotherm of Pt/C. At a relative N2 pressure of 0.4-0.7, an increase in the amount of adsorbed N2 with a hysteresis loop corresponds to the filling of mesopores. This result suggests that not only micropores less than 1 nm but also mesopores were generated under pyrolysis. The BET surface area was calculated to be 623 mVg. The pore size distribution of mesopores was calculated using the BJH model for the desorption branch and is shown in Fig. 1(b). The average pore size was 3.5 nm. The neutral surfactants molecule must play an important role to generate micropores and mesopores during the carbonization. We expect that the existence of mesopores would improve the diffusion of reactants and products in selective CO oxidation. 

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