Combination of Langmuir-Hinshelwood-Hougen-Watson and microkinetic approaches for simulation of biogas dry reforming over a platinum-rhodium alumina catalyst

Abstract

Dry reforming of CH4 on a platinum-rhodium alumina catalyst is selected to numerically investigate biogas reforming process. Langmuir-Hinshelwood-Hougen-Watson (LHHW) rate expressions for dry reforming and reverse water-gas shift reactions are presented. Activation energies are estimated by combining microkinetics with the theory of unity bond indexquadratic exponential potential (UBI-QEP). Pre-exponential factors are initially obtained by using the transition state theory (TST) and optimised, later, by minimising errors between modelling and experimental data. Adsorption of CH4 on the catalyst surface is found to be the rate determining step in the range of relatively low temperature (600-770 °C), while at relatively high temperature (770-950 °C) the thermal cracking of adsorbed CH4 is the rate controlling step. Small effect of reverse water-gas shift reaction results in the ratio of H2 to CO produced less than unity for all operating conditions. The simulation shows that the dry reforming process proceeds with reaction rate far from equilibrium state. The presented mechanism is capable of predicting the dependence of biogas dry reforming activities (e.g., reactant conversions, product formations, H2 to CO ratio, and temperature profile inside the catalyst) on operating conditions (e.g., inlet temperature, heat supplied through the catalyst wall, and composition of biogas at inlet).

A simple coupled ANNs‐RSM approach in modeling product distribution of Fischer‐Tropsch synthesis using a microchannel reactor with Ru‐promoted Co/Al 2 O 3 catalyst

“…4 The Langmuir-Hinshelwood-Hougen-Watson (LHHW) type approach has been found successfully in describing many different heterogeneous catalytic reactions such as methylcyclohexane dehydrogenation over Pt/Al 2 O 3 catalyst, the oxidation of nitric oxide over carbon catalysts, esterification of acetic acid with ethanol over ion exchange resins etc. 10 Although the efforts of using complex LHHW mechanistic approach with the aid of genetic algorithm (GA) for data regression provide the robust solutions, [11][12][13][14][15] the limitations pertaining to the debatable mechanistic elementary reactions, difficulties of being both physical and statistical relevance, tedious computational times, and complexity of the established kinetic system based upon proposed mechanistic elementary reactions, all pose persistent challenges on designing and sizing the catalytic process involving the complex kinetics in the realistic scenario. 10 Although the efforts of using complex LHHW mechanistic approach with the aid of genetic algorithm (GA) for data regression provide the robust solutions, [11][12][13][14][15] the limitations pertaining to the debatable mechanistic elementary reactions, difficulties of being both physical and statistical relevance, tedious computational times, and complexity of the established kinetic system based upon proposed mechanistic elementary reactions, all pose persistent challenges on designing and sizing the catalytic process involving the complex kinetics in the realistic scenario.…”

“…[6][7][8][9] Among them, Fischer-Tropsch (FT) synthesis is one of the extensively investigated area using the LHHW approach. 10 Although the efforts of using complex LHHW mechanistic approach with the aid of genetic algorithm (GA) for data regression provide the robust solutions, [11][12][13][14][15] the limitations pertaining to the debatable mechanistic elementary reactions, difficulties of being both physical and statistical relevance, tedious computational times, and complexity of the established kinetic system based upon proposed mechanistic elementary reactions, all pose persistent challenges on designing and sizing the catalytic process involving the complex kinetics in the realistic scenario. [16][17][18][19][20][21][22][23][24][25] Due to its inherent features of fast converge, less computational time together with equipped statistical analysis, the hybrid ANNs-RSM has been successfully implemented into many practical applications such as investigation of the flexible mechanism considering friction dynamics in lubricating industry, 26 structural reliabilities studies, 27 and optimization of biohydrogen productions etc.…”