Fundamental Nature of Reforming Reactions in Catalytic Reactor Systems
11 Pages Posted: 4 Aug 2022
Date Written: July 29, 2022
The development of better steam reforming catalysts has long been an area of intense interest. Despite years of intense research, there remains a need for steam reforming catalysts and steam reforming methods with improved performance in terms of hydrogen productivity, low temperature activity, and low carbon monoxide selectivity. This study relates to a thermochemical process for producing hydrogen by the endothermic reaction of methanol with steam in a heterogeneous catalytic reactor system. Computational fluid dynamics simulations are carried out to better understand the consumption, generation, and exchange of thermal energy between endothermic and exothermic processes in the heterogeneous catalytic reactor system used for hydrogen production. The effects of different factors on the fundamental nature of reforming reactions in heterogeneous catalytic reactor systems are investigated. The results indicate that chemisorption can occur over a wide temperature range, the most effective temperature for adsorption depending on the nature of the catalyst. Since heterogeneously catalyzed reactions occur on the surface of the catalyst, the rates of such reactions are proportional to the accessible surface area of the catalyst. Active catalysts are usually highly porous solids. To be efficient catalytically, a process must involve energies of activation for all the steps involved that, at their maxima, are less than those required for the uncatalyzed reaction. The reactor designs suffer from a fundamental limitation resulting from the flow configuration in which a reacting stream flows parallel to a heat transfer surface through which the majority of heat is transferred perpendicular to the direction of fluid flow. Balancing the heat requirements of an endothermic reaction with heat generated by an exothermic reaction flowing parallel to and on the opposite side of a separating plate is extraordinarily difficult since the endothermic reaction is likely to have a very different dependence upon concentration and temperature than the endothermic reaction. The rates of reforming reactions depend upon a number of factors, including the chemical nature of the reacting species and the external conditions to which they are exposed.
Keywords: Thermochemical processes; Heterogeneous catalysis; Hydrogen production; Chemical reactions; Transport phenomena; Steam reforming
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