(560di) Catalytic Ethylene Dimerization to 1-Butene Using Automated Construction of Microkinetic Models with Rmg-Cat

The dimerization of ethylene to 1-butene is a reaction of interest as not only is the cost of ethylene low, but also because 1-butene is used in the production of high value plastics and polymers such as polyethylene and polybutene. Unfortunately, this reaction needs to be described in great detail to understand the full chemistry of the system, which makes intimate knowledge of all species both adsorbed and not adsorbed to the catalytic surface necessary, resulting in models that are quite large. Acquiring this level of detail for one industrially relevant reaction on a single catalyst is time consuming and complex, making the need for a quick and accurate high-throughput method for screening novel catalysts for any reaction even greater. Our Reaction Mechanism Generator for Heterogeneous Catalysis (RMG-Cat) [1], built upon the well-established open-source RMG software [2], can provide the complete reaction network from user-defined ignition conditions. It can: propose both elementary reactions and new species by applying reaction templates and recipes; estimate thermodynamic and kinetic parameters using databases of DFT calculations, functional-group decision trees, and heuristics; solve governing rate equations; and decide which reaction pathways should be explored further.

RMG-Cat can estimate adsorbate thermochemistry on a range of hypothetical metal surfaces using linear scaling relations and construct detailed microkinetic models for any surface, with no prior assumption of a rate limiting step. By running simulations with sensitivity analysis, we can determine the rate limiting step on each surface and can plot a “volcano surface” of the degree of rate control of each reaction as a function of elemental binding energies. We demonstrate this new tool on the catalytic dimerization of ethylene to 1-butene and longer olefins.

[1] Goldsmith, C. F., West, R. H. “Automatic Generation of Microkinetic Mechanisms for Heterogeneous Catalysis” J. Phys. Chem. C. 21 (18), 9970–9981 (2017) http://doi.org/10.1021/acs.jpcc.7b02133

[2] Gao, C. W., Allen, J. W., Green, W. H., West, R. H. "Reaction Mechanism Generator: Automatic construction of chemical kinetic mechanisms". Comput. Phys. Commun., 203, 212-225, (2016) http://doi.org/10.1016/j.cpc.2016.02.013