Apparent reaction kinetics

In general, a gas-solid catal3dic reaction involves seven processes on porous catalysts as follows  

Among these, (1) and (7) are called as external diffusion, (2) and (6) internal diffusion, and both of them are physical processes the others are chemical kinetic processes. 

The mechanism or sequence about gas-solid catalytic reactions can be roughly shown in Fig. 2.32. There must be mass transfer processes between gas-sohd and in pores of solid for the whole process of gas-solid catalytic reaction. 

Reaction heat and temperature difference between gas stream and catalyst leads to the heat transfer processes between gas and solid. The mass and heat transfer coefficients depend on Reynold and Prandtl numbers of fluid flow, i.e., state and physical properties of fluid flow. Mass and heat transfer processes in solid cataljret and catal3dic reaction process on internal surface of catalysts take place simultaneously, which relate to the diffusion coefficients of reactants and products as well as the heat conductivity coefficient of catalysts. Therefore, the overall rate of a catal3dic reaction depends not only on the rate of chemical reaction, but also on several physical processes such as flowing state, mass and heat transfer. The kinetics involving physical process effect is usually called as apparent or macrokinetics, while that having no physical processes is called intrinsic or microkinetics. 

the physical transportation and adsorption-desorption should be involved in the interpretation of heterogeneous catalytic processes compared with that of homogeneous ones. It should be considered to understand the regularity of each step, to compare the effect of each step on total reaction rate and to And the slowest step that is called as rate determining step. 

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Continuing the formal development of the influence of the adsorption isotherm on the apparent reaction kinetics, we next consider the case of a reac-... 

If one has intrinsic and apparent reaction kinetics available, then Equation 10 may be viewed as a three-parameter model (t)ce, b wo> B -d f°r prediction of isothermal trickle-bed reactor performance. However, Biwo depends on two mass transfer coefficients and a priori model parameter evaluation is no simpler than before. 

Constitutionally speaking, the axial gas-solid distribution two-phase model gives reasonable prediction for CFB combustion, but the sub-models of apparent reaction kinetics for S02 sorption and NOx reduction still calls for further improvement. 

Real and Apparent Reaction Kinetics a. Falsification of Reaction Order." If... 

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