The promotional effect of copper on alumina and activated carbon supported NIMO hydrodeoxygenation catalysts

Abstract

The rapid depletion of oil reserves and the environmental issues caused by heavy reliance on fossil fuels throughout society's explosive growth have forced the world to find alternative sources of fuel. Fossil fuels for transportation and industrial purposes can be satisfactorily replaced with biofuels such as biodiesel and bioethanol liquid fuels. Unfortunately, use of these bioderived fuels is discouraged because of their high concentration of oxygen-containing compounds. Several studies have been conducted to remove the oxygen-containing compounds, most of which have focused on removing aromatic oxygenated compounds due to the difficulty of removing oxygen from these compounds. Hydrodeoxygenation (HDO) catalysts are a crucial part of the HDO process. However, the currently employed hydrodeoxygenation (HDO) catalysts suffer from deactivation due to the high oxygen content in bio-oil, thus producing fuel sources that cannot comply with the required fuel quality standards. Unsupported NiMo and CuNiMo catalysts were synthesized and characterized to understand the interactions between the metals (Ni, Mo, and Cu) in the catalysts and guide on understanding the use of Cu as an additional promoter metal. Single crystal XRD revealed the interaction between Ni and Mo showing how octahedral MoO surrounds Ni forming an octahedral sphere. Other characterization techniques such as FT-IR, UV/Vis, SEM-EDS, TEM, XRD, ICP, and TGA/DSC were also employed to elucidate the relationships. The alumina and activated carbon supported NiMo/γ-Al2O3, NiMo/AC, CuNiMo/γ-Al2O3, and CuNiMo/AC catalysts were also prepared and characterized using similar techniques to further understand the idea of promoting using copper and the possibility of migrating from the conventional γ-Al2O3 support which suffers deactivation due to dealumination. It was observed that the general uptake of metals is much higher for the γ-Al2O3 support compared to the AC support. Diffuse reflectance spectroscopy showed better dispersion of Ni and Mo in the γ-Al2O3 catalyst when Cu was introduced. The catalysts were also evaluated in the HDO of phenol model fuel and the catalytic activity followed the trend: CuNiMo/γ-Al2O3 (46.1%) > NiMo/γ-Al2O3 (42.1%) > NiMo/AC (25.1%) > CuNiMo/AC (5.6%). HDO studies showed much higher improvement in catalytic activity when Cu was introduced to γ-Al2O3 supported NiMo while in the case of AC-supported NiMo, the activity was unusually lower regardless of the remarkably higher total metal content in the catalyst. Through this work, we recommend the use of Cu as a promoter in γ-Al2O3 supported NiMo catalysts for HDO. Further work is needed to fully understand the disparities observed when Cu is used as a promoter in the AC supported NiMo catalysts.Thesis (MSc) -- Faculty of Science, School of Biomolecular & Chemical Sciences, 202