Mechanochemistry, the use of mechanical stress to activate chemical reactions, has emerged as a significant area of interest in recent years. Two theoretical approaches have been developed to simulate mechanochemical processes: COnstrained Geometries Simulate External Force (COGEF) and External Force is Explicitly Included (EFEI). In the COGEF method, mechanical stress is simulated by increasing the distance between atoms in a molecule that serve as pulling points (PPs) at a constant rate. In the EFEI methods, a constant external force (Fext) is applied between PPs, allowing the atoms to move to maintain that force. Both methods have been used in the literature to study the ring opening of cyclobutene under mechanochemical conditions. These studies have shown that applying a force between cis PPs in cyclobutene induces ring opening along the conrotatory pathway in COGEF-based simulations and ring opening along the disrotatory pathway in EFEI-based simulations. The latter is consistent with experiments. The work in this thesis identifies the origin of the differences in the outcomes obtained with these two methods, which may be of interest in the context of researchers selecting methods to simulate mechanochemical processes. The results demonstrate that the origin of the difference in behaviour is related to the manner in which these methods alter the potential energy surface (PES) through the application of a mechanical stress. Specifically, the PES obtained with the COGEF method does not contain a minimum energy pathway (MEP) linking cyclobutene to the disrotatory product, whereas the EFEI surface does contain such a path. The differences in PESs suggest that the EFEI method is more suitable to simulate mechanochemical processes. The EFEI approach was then used to examine how the electronic structure evolves to permit a formally forbidden disrotatory reaction to occur. The circumvention of the Woodward-Hoffmann rules was not due to a change in the electronic structure. Instead, the application of an external force shifts the transition state along the reaction coordinate towards the reactants, lowering the barrier for the reactions. The orbital effects that disfavor movement from reactants to products are rendered secondary to mechanochemical factors. / Thesis (Master, Chemistry) -- Queen's University, 2011-12-14 16:47:24.197

Removal of polynuclear aromatics from diesel fuel has become a focus of intense research due to the stringent environmental legislation associated with clean fuels. In this work, selective ring opening of model compound decalin over the set of catalysts comprising of 1) Ir-Pt supported on mesoporous Zr-MCM-41, large and medium pore zeolites like HY and H-Beta and 2) Ni-Mo/carbide on HY, H-Beta, Al-SBA-15, ¥ã- alumina and silica alumina were studied. All the catalysts were extensively characterized by BET surface area measurement, CO-chemisorption, XRD, FTIR, TPR and TPD of ammonia. Ring opening of decalin was studied on these catalysts in a trickle-bed reactor in a temperature range of 200- 400 ¡ÆC, pressure range of 2-7 MPa and LHSV of 1 to 3 h- 1. 31.7 and 65.0 wt.% of RO yield and selectivity were observed on Ir-Pt/HY catalyst at 220 ¡ÆC, whereas 34.0 and 40.0 wt.% of ring opening yield and selectivity were observed on Ni-Mo carbide/HY catalyst at 240 ¡ÆC. From the model compound studies, Ir-Pt/HY, Ni-Mo carbide/HY and Ni-Mo carbide/H-Beta were selected for study of hydrotreated light gas oil in a trickle bed reactor. Ni-Mo carbide/HY performed better over other catalysts and increased the cetane index of hydrotreated light gas oil by 12 units at 325 ¡ÆC. A first order kinetic model was fitted for the hydrotreated light gas oil study. 89, 111 and 42 KJ/gmol of activation energies was observed for dearomatization, aromatization and naphthenes cracking steps, respectively. The thermodynamic equilibrium calculations reveal that the selectivity of ring opening products of decalin can be maximized by favoring the formation of unsaturated compounds at higher operating temperatures. Energetics of dealkylation and ring opening reactions of naphthenes in gas phase and on the surface of Br©ªnsted acid sites were calculated using quantum chemical simulations. In iv gas phase, ratio of Arrhenius activation energies for forward and reverse reactions of RO and dealkylation reactions are 1.92 and 1.82 respectively. Deakylation on different level clusters revealed that surface reaction is the rate controlling.

Removal of polynuclear aromatics from diesel fuel has become a focus of intense research due to the stringent environmental legislation associated with clean fuels. In this work, selective ring opening of model compound decalin over the set of catalysts comprising of 1) Ir-Pt supported on mesoporous Zr-MCM-41, large and medium pore zeolites like HY and H-Beta and 2) Ni-Mo/carbide on HY, H-Beta, Al-SBA-15, ¥ã- alumina and silica alumina were studied. All the catalysts were extensively characterized by BET surface area measurement, CO-chemisorption, XRD, FTIR, TPR and TPD of ammonia. Ring opening of decalin was studied on these catalysts in a trickle-bed reactor in a temperature range of 200- 400 ¡ÆC, pressure range of 2-7 MPa and LHSV of 1 to 3 h- 1. 31.7 and 65.0 wt.% of RO yield and selectivity were observed on Ir-Pt/HY catalyst at 220 ¡ÆC, whereas 34.0 and 40.0 wt.% of ring opening yield and selectivity were observed on Ni-Mo carbide/HY catalyst at 240 ¡ÆC. From the model compound studies, Ir-Pt/HY, Ni-Mo carbide/HY and Ni-Mo carbide/H-Beta were selected for study of hydrotreated light gas oil in a trickle bed reactor. Ni-Mo carbide/HY performed better over other catalysts and increased the cetane index of hydrotreated light gas oil by 12 units at 325 ¡ÆC. A first order kinetic model was fitted for the hydrotreated light gas oil study. 89, 111 and 42 KJ/gmol of activation energies was observed for dearomatization, aromatization and naphthenes cracking steps, respectively. The thermodynamic equilibrium calculations reveal that the selectivity of ring opening products of decalin can be maximized by favoring the formation of unsaturated compounds at higher operating temperatures. Energetics of dealkylation and ring opening reactions of naphthenes in gas phase and on the surface of Br©ªnsted acid sites were calculated using quantum chemical simulations. In iv gas phase, ratio of Arrhenius activation energies for forward and reverse reactions of RO and dealkylation reactions are 1.92 and 1.82 respectively. Deakylation on different level clusters revealed that surface reaction is the rate controlling.