Multiscale Modelling of In Situ Oil Sands Upgrading with Molybdenum Carbide Nanoparticles

Abstract

This chapter presents multi-scale models of the reactions that occur in the in situ oil sands upgrading process. Its focus is on the various modelling tools and their applications to the benzene hydrogenation reactions catalyzed by molybdenum carbide nanoparticles. As the reaction mechanism of benzene hydrogenation on molybdenum carbide is not clear, we start with density functional theory (DFT) studies to elucidate the reaction mechanism, using both periodic and cluster models. Benzene hydrogenation on molybdenum carbide follows the Langmuir-Hinshelwood mechanism, with the six-member ring tilting up gradually. A tight-binding quantum chemical molecular dynamics (TB-QCMD) method is used to track the physical motion of the atoms in the reaction processes of C6H6 on a Mo-terminated α-Mo2C (0001) surface. The approximate DFT method, density functional tight-binding (DFTB), was parameterized to allow the quantum mechanical treatment of nanoscale systems. With the nudged elastic band method, the potential energy profiles of benzene hydrogenation on molybdenum carbide nanoparticles have been obtained. Finally a force field was brought in to describe the solvent environment in the system, leading to a multiscale quantum mechanical/molecular mechanical (QM/MM) model. This study suggests that entropy and the environment play important roles in heterogeneous reactions catalyzed by molybdenum carbide nanoparticles.