In-situ Heavy Oil Upgrading with Molybdenum Carbide Nanoparticles: A Multiscale Modelling Approach

Liu, Xingchen

In-situ Heavy Oil Upgrading with Molybdenum Carbide Nanoparticles: A Multiscale Modelling Approach

atmire.migration.oldid	3025
dc.contributor.advisor	Salahub, Dennis
dc.contributor.author	Liu, Xingchen
dc.date.accessioned	2015-03-16T16:07:12Z
dc.date.available	2015-06-23T07:00:43Z
dc.date.issued	2015-03-16
dc.date.submitted	2015	en
dc.description.abstract	Heterogeneous reactions catalyzed by transition-metal-related nanoparticles represent a crucial type of reaction in chemical industry. This thesis provides a multiscale modelling approach to study the benzene hydrogenation reactions on molybdenum carbide nanoparticles (MCNPs) in the process of in-situ heavy oil upgrading in Alberta. To clarify the debate on the benzene hydrogenation mechanism, density functional theory (DFT) calculations are performed with cluster models in Chapter 3. From the DFT thermodynamic data, together with the experimental information gathered in the literature, the benzene hydrogenation mechanism on molybdenum carbide was identified as the Horiuti-Polanyi type Langmuir-Hinshelwood mechanism. Benzene adsorbs horizontally on the molybdenum carbide, and the hydrogenation process causes the gradual tilting up of the C6 ring, to form 12-dihydrobenzene and 1234-tetrahydrobenzene, and finally the product cyclohexane, and causes the crossover from chemisorption to physisorption. Topological analysis of the electron localization function (ELF) in Chapter 4 provides a deeper understanding of the interactions between the unsaturated hydrocarbons and the MCNPs. The chemisorption of unsaturated hydrocarbons on the MCNPs involves strong chemical interactions of a covalent nature, and is dominated by multi-center electron sharing interactions. The building up of a multiscale model starts with the parameterization of the quantum mechanical (QM) density functional tight-binding (DFTB) method for Mo, C, H, O, and Si. The QM calculations show that the MCNPs are highly metallic nanoparticles. The topology of the active sites is more important than the sizes of the MCNPs for the catalytic activity. By coupling the QM DFTB method with an MM force field, a quantum mechanical/molecular mechanical (QM/MM) model was built to describe the reactants, the nanoparticles and the surroundings. Umbrella sampling (US) was used to calculate the free energy profiles of the benzene hydrogenation reactions in a model aromatic solvent in the in-situ heavy oil upgrading conditions. By comparing with the traditional method in computational heterogeneous catalysis, the results reveal new features of the metallic MCNPs. Rather than being rigid, they are very flexible in the working condition due to the entropic contributions of the MCNPs and the solvent, which greatly affect the free energy profiles of these nanoscale heterogeneous reactions.	en_US
dc.identifier.citation	Liu, X. (2015). In-situ Heavy Oil Upgrading with Molybdenum Carbide Nanoparticles: A Multiscale Modelling Approach (Doctoral thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca. doi:10.11575/PRISM/26557	en_US
dc.identifier.doi	http://dx.doi.org/10.11575/PRISM/26557
dc.identifier.uri	http://hdl.handle.net/11023/2113
dc.language.iso	eng
dc.publisher.faculty	Graduate Studies
dc.publisher.institution	University of Calgary	en
dc.publisher.place	Calgary	en
dc.rights	University of Calgary graduate students retain copyright ownership and moral rights for their thesis. You may use this material in any way that is permitted by the Copyright Act or through licensing that has been assigned to the document. For uses that are not allowable under copyright legislation or licensing, you are required to seek permission.
dc.subject	Chemistry--Physical
dc.subject.classification	multiscale modelling	en_US
dc.subject.classification	Nanoparticles	en_US
dc.title	In-situ Heavy Oil Upgrading with Molybdenum Carbide Nanoparticles: A Multiscale Modelling Approach
dc.type	doctoral thesis
thesis.degree.discipline	Chemistry
thesis.degree.grantor	University of Calgary
thesis.degree.name	Doctor of Philosophy (PhD)
ucalgary.item.requestcopy	true