Calculation of Mass Transfer Limitations for a Gas-Phase Reaction in an Isothermal Fixed Bed Reactor: Tutorial and Sensitivity Analysis

Abstract

The study of the reactivity of catalysts requires one to assess chemical kinetics and mechanisms in the absence of mass transport artifacts. Despite the existence of models and criteria for assessing the presence of mass transfer limitations during catalytic tests for gas-phase reactions in isothermal fixed bed reactors, the literature does not present straightforward protocols for performing the latter calculations. In this work, we present a systematic protocol for the calculations above. Particularly, we present protocols for estimating the effectiveness factor for external and the Weisz-Prater number for the internal mass transfer limitations. Data previously published on the oxidation of propane over mixed vanadium–aluminum (hydr)oxides was taken as a case study. Based on these protocols, we did a sensitivity study of the models used for calculations. Results showed that the model for calculating the effectiveness factor was poorly sensitive to all the above modifications. Meanwhile, the Weisz-Prater number was much more sensitive to the studied modifications, even reaching deviations up to ∼200%.

Regulation of the Reaction Route in Hydrogenation of Renewable Palm Oil Using NiMo Bimetallic Catalyst

“…The data in Table S5 show that the diffusion rates in pores were much faster than the conversion rates for the palm oil SDO, i.e., the diffusion limits could be excluded for the reactions studied in this work . Furthermore, the Weisz-Prater analysis − also assesses mass transfer limitations in the Supporting Information, which showed the same conclusion. Then, as illustrated in Figure a,b, the nonsulfided catalysts exhibit discernibly disparate activation energy values.…”

Stabilizing Pd–cerium oxide–aluminum oxide catalysts for methane oxidation by reduction pretreatments

“…This was verified by means of the Weisz-Prater and Mear's criteria for internal and external mass transfer limitations, respectively. 52,53 The MTL data and calculations for the reduced/aged (Pd/Ce/Al-R-a and Ce/Pd/Al-R-a) and aged (Pd/Ce/Al-a and Ce/Pd/Al-a) catalysts are given in the ESI †. The Weisz-Prater ( C w-p ) values for these catalysts were between 6–9 at 500–850 °C (Table S6†).…”

“…This was verified by means of the Weisz-Prater and Mear's criteria for internal and external mass transfer limitations, respectively. 52,53 The MTL data and calculations for the reduced/aged (Pd/Ce/Al-R-a and Ce/Pd/Al-R-a) and aged (Pd/ S6 †). The internal mass transfer limitations (MTL) started above 340 °C (C w-p > 1) for the reduced/aged catalysts (Fig.…”

Application of Model-Free and Model-Based Kinetic Methods in Evaluation of Reactions Complexity during Thermo-Oxidative Degradation Process: Case Study of [4-(Hydroxymethyl)phenoxymethyl] Polystyrene Resin

“…Namely, in order to obtain the rate of the reaction that leads to the degradation of indene in the presence of oxygen in the reactor conditions, all the above-mentioned quantities should be taken into account and inserted into some form of newly constructed equation of the Arrhenius type. On the other hand, for the calculation of mass transfer limitations of a gas-phase reaction inside the chemical reactor (for example, in a fixed bed reactor), a large number of variables needs to be considered in the simulation tests, as can be seen in the paper of García-Sánchez et al [53]. Therefore, after finding the optimal reaction rate for the indene catalytic reaction under chemical reactor conditions, it should then be compared with the observed reaction rate, which may be affected by the external mass diffusion [54] and intrinsic reaction rate of the catalyst species.…”