Nonlinear Behavior of Methanol Synthesis Compared to CO₂ Methanation

Abstract

The nonlinear behavior of CO2 methanation over a Ni‐catalyst is compared to methanol synthesis over a standard Cu/ZnO‐catalyst in a continuous stirred tank reactor (CSTR). Both reactions have received a lot of attention these days for chemical energy storage. Both reactions are exothermic but behave in a different way. CO2 methanation is known to be strongly exothermic, giving rise to multiple steady states. This behavior is induced by the self‐acceleration of the methanation reaction because the heat production of the chemical reaction increases with rising temperature. It is shown that methanol synthesis behaves fundamentally different under the operating conditions usually employed in practice. It is less exothermic but, even more important, the overall heat production of the methanol reaction system decreases with increasing temperature, giving rise to a unique and stable steady state. This insight is obtained with an extension of the classical graphical analysis with heat production and heat removal curves.