Development of the Crank’s diffusion model for the case of material-gas feedback regime in gas flow reactors. Advanced methodology of oxygen partial pressure relaxation for the kinetics of oxygen exchange in nonstoichiometric oxides

Oxygen Exchange in MIEC Perovskite Oxide La0.6Sr0.4Co0.2Fe0.8O3−δ: Kinetic and Equilibrium Parameters and Their Interrelation

“…To do this, it is necessary to refer to the main provisions of the model described in. 41,45 According to the model, the working area in which cylindrical samples are located inside the quartz tube can be represented as a chain of continuous stirred tank reactors. This approximation allows us to take into account the inhomogeneity of the conditions that occur when gas flows inside such oxide-filled reactors.…”

“…When setting up such an experiment, questions naturally arise not only about the optimal selection of sample geometric dimensions but also about the correct choice of the flow rate, the values of the partial pressures of oxygen, and the value of the pressure step. To do this, it is necessary to refer to the main provisions of the model described in. , According to the model, the working area in which cylindrical samples are located inside the quartz tube can be represented as a chain of continuous stirred tank reactors. This approximation allows us to take into account the inhomogeneity of the conditions that occur when gas flows inside such oxide-filled reactors.…”

“…Experimental data were processed using the original macrokinetic model of tanks-inseries (TIS). 41 The model is based on a consistent macrokinetic consideration of diffusion-convection in the flow reactor with oxide samples, surface reaction of oxygen with oxide, and oxygen diffusion in oxide particles. This model is a development of the "Crank model" (a classical solution of the problem of diffusion in solid particles reacting with a gas of constant composition), widely used to describe the relaxation kinetics of oxygen exchange with oxides in such methods as relaxation of electrical conductivity.…”

Perspective on high-temperature surface oxygen exchange in a porous mixed ionic-electronic conductor for solid oxide cells

“…This assumption has been proven to be valid by Elshof et al when the p O 2 gradient is within a factor of 10. 49,68 Furthermore, the blank theory about the inhomogeneous ORR kinetics of porous MIEC at the gas-solid interfaces has been filled by Zhang et al and Nemudry et al 1,32 Ji et al studied the ORR kinetics of porous CeO 2Àd using the ECR method. Their results demonstrate that the reciprocal of the characteristic time (1/t), which denotes the total reaction rate of the ORR, shows different temperature dependences on temperature.…”

“…To solve the problem associated with gas diffusion in pores, a general consensus among researchers is to divide porous MIEC into finite volume elements (FVEs). 1,32 The normalized conductivity for the i th FVE ( i ( t )) can be obtained with similar analytical thinking for a dense system with the surface exchange as the rate-limiting step, as shown in eqn (5). Note that the oxygen bulk transport of porous MIEC is too fast to be negligible where the submicron particle size is much smaller than the characterized length.…”