Optimization of iron-based catalyst for partial upgrading of Athabasca Bitumen: The role of Fe oxidation state, particle size, and concentration

Abstract

The present investigation examines the prospective application of Fe-based catalysts for catalyzing the partial upgrading of Athabasca oil sand bitumen, aiming for developing an economically viable and environmentally sustainable process. The primary focus is to analyze the impact of the oxidation state of iron, catalyst particle size, and catalyst concentration on partial upgrading efficiency to optimize bitumen resource utilization without the need of an external source/supply of hydrogen gas using an autoclave reactor. The experimental results demonstrate that Fe-based catalysts, particularly those with lower oxidation states such as FeS, FeO, and Fe3O4, significantly improve the oil quality and reduce bitumen’s viscosity through increasing saturates and substantially reducing the asphaltene fractions. Furthermore, it is also identified that those catalysts can promote hydrogenation and cracking reactions that transform heavier fractions into lighter ones while achieving up to 59% vacuum residue conversion. A comprehensive screening process using Minitab statistical software was made to identify the best catalyst based on the catalyst’s oxidation state, concentration, and particle size range. As a result, Fe3O4 nanoparticles at a 0.5 wt% loading have been identified as the optimal catalyst combination for achieving the maximum liquid yield, while simultaneously producing the minimum asphaltene content, and maximum viscosity reduction. An assessment of the fresh and spent Fe3O4 catalyst yielded valuable insights concerning the catalytic partial upgrading of bitumen, unveiling a reaction mechanism involving iron catalyst sulfidation, desulfurization reactions, CH scission, and hydrocarbon cracking, in addition to the formation of coke. The potential role of various alloy materials employed in the fabrication of reactors for bitumen partial upgrading has also been studied and compared, discussing their unique advantages and limitations in terms of product quality and liquid yield. The findings presented in this study contribute significantly to the development of more efficient and sustainable upgrading processes, paving the way for optimizing catalyst properties for bitumen upgrading applications and providing a valuable perspective on the role of catalysts in the upgrading of heavy oils.