Hierarchical Multiscale Modeling of Methane Steam Reforming Reactions

In this work, a hierarchical multiscale modeling approach is demonstrated. Models at the atomic and molecular level, on Ni crystal, in catalyst pellets and reactor tubes in a steam methane reformer are included. The kinetics of steam reforming, including carbon formation on the supported Ni catalyst, was studied experimentally in a tapered element oscillating microbalance (TEOM) reactor at relevant industrial conditions. A predictive microkinetic model of steam reforming including filamentous carbon formation was developed. The activation energy and pre-exponential factor of each elementary step were estimated using the unity bond index−quadratic exponential potential (UBI−QEP) approach and transition-state theory, respectively. Only a few parameters in the model were refined based on the experimental results and DFT calculations. The hybrid kinetic model combining a traditional kinetic model and a microkinetic model was used in simulations to significantly reduce the computational load. Maps of the kinetic carbon potential in the catalyst pellets and tubular reformer were established at different operating conditions. It was found that intraparticle diffusion resistance increases the carbon potential. High carbon potentials were found near both the inlet and the outlet of the reactor.