Metal-doped Cr2O3 as a catalyst for non-oxidative propane and butane dehydrogenation: A multiscale kinetic study

Molecules that are difficult to convert catalytically often require a complex and specially tailored catalyst composition. Catalytic alkane dehydrogenation is an interesting example, where theoretical ab-initio and kinetic meso-scale simulations can provide the understanding of the performance improvement when the catalyst composition is altered. Herein, we study non-oxidative dehydrogenation of propane and butane over variously doped (Na, Li, K, Mg, Ca, or Cs) chromium oxide using first principles. The reaction pathway for the conversion of propane to propene/propyne and of butane to 1- and 2-butene is studied using density functional theory with the Hubbard U correction. Energies and kinetic parameters describing the adsorption, desorption, and surface reactions are used in mean-field microkinetic and kinetic Monte Carlo simulations. The process was modelled at industrially relevant temperatures, pressures, and feed gas flow velocities. Calculating the catalytic conversion, selectivity to products, and activity trends show that surface doping enhances the conversion and activity. The highest conversion for most dopants is achieved at temperatures below 850 K and atmospheric pressure, where the activity is significantly improved compared to the non-doped Cr2O3 catalyst.