CONICET | Buscador de Institutos y Recursos Humanos

Amodel to calculate the actual transient effectiveness factor in sphericalporous catalyst particles in gradientless reactors, where a first orderreaction takes place under isothermal conditions, linear equilibrium adsorptionand intraparticle diffusion control, was developed. After a certain time haselapsed following a change in the feed?s reactant concentration, the transienteffectiveness factor can be approximated as a linear combination of the steadystate effectiveness factor and the relative rate of change of the concentrationin the fluid phase. Oppositely to the well-known steady state effectivenessfactor, which depends only on the Thiele modulus , related to intrinsic properties of the catalysts,the transient effectiveness factor also depends on other two dimensionlessnumbers:, the relationship between the capacity ofaccumulation of reactant in the fluid and solid phases, and , a relationship between the convective flow andthe intraparticle diffusion rate. In this way, the catalyst load, the reactorvolume and the volumetric flow do impact on the effectivenessfactor. The coefficients defined as and are the Diffusion-Adsorption-ReactionFactor and the Flow Factor, respectively, which are complex functions of theThiele modulus, the convective modulus andthe system?s adsorption capacity, and which can be used to correct the steadystate effectiveness factor to yield the approximated transient effectivenessfactor, which is more exact. In the case of a pulse perturbationin the reactant?s concentration, the transient effectiveness factor reaches aconstant value which is larger than that from the steady state effectivenessfactor and, the larger the catalyst mass and the flow, the larger thedifference. Results show the existence of a pseudo-equilibrium state ingradientless reactors.

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