The National Institute of Chemistry, as a MefCO₂ partner, attended the 2016 AIChE Annual Meeting and delivered the presentation of scientific project activities, entitled “Mechanism, Reaction Kinetics and Multi-Scale Modelling of CO2 Hydrogenation to Methanol over Trimetallic Heterogeneous Catalysts”.
The AIChE Annual Meeting is the premier educational forum for chemical engineers interested in innovation and professional growth. Academic and industry experts cover wide range of topics relevant to cutting-edge research, new technologies, and emerging growth areas in chemical engineering. The attendees and the type of audience primarily comprises chemical engineers, but optionally also mechanical engineers, chemists and physicists, whereas the field of work is predominantly related to academia, while a substantial industrial presence is also noted.
As carbon dioxide is a source of potential carbon-containing raw material and also one of the major greenhouse gases, and a highly efficient catalyst is the key for methanol synthesis via CO2 hydrogenation, both catalyst synthesis itself as well as the multi-scale material/process modelling were presented. Thus, in parallel to extensive experimental trials (varying catalysts and process operating conditions), density functional theory (DFT) calculations were used to determine elementary reaction steps and their activation energies, as well as pre-exponential factors, yielding the rate constants for different operating conditions. These parameters were used in the kinetic Monte Carlo (KMC) and micro-kinetic modelling to obtain the model for a packed bed reactor (PBR). The two critical variables for the design of PBR, the packing void fraction and the pressure drop across PBR, are usually predicted using empirical correlations that were and still are a matter of an ongoing discussion among researchers. The generalization of typical parameters brings about a high error risk and leads to oversized reactors due to the capacity safety factor.
In contrast to the correlations and experimental investigations of adaptive parameters, several numerical approaches are available today to investigate the flow within particle packings, mostly based on computational fluid dynamics (CFD), which were also applied in this study. The common work-flow for the CFD simulations of a realistic packed bed thus consisted of reactor bed packing, domain meshing, boundary conditions setting, simulation running, and finally, collecting the results, coupling CFD with reaction kinetics upon operating outside a fully-developed turbulent regime, in which the solution could have been approximated by plug flow pattern.