Design and Optimization of Novel Catalytic Materials for Sustainable Fuels through Multiscale Modelling Techniques

Abstract

Depletion of fossil fuels and concerns over global warming are driving scientists from academy and industry towards sustainable carbon sources, particularly ones centralized on biomass-valorization processes. Pyrolysis of biomass yields a complex mixture known as bio-oil, comprising of aqueous and organic fractions. Due to the inherent instability of bio-oil, its catalytic upgrading is necessary through hydrodeoxygenation (HDO) or steam reforming (SR) reactions. The aim of this PhD dissertation is to employ multiscale computational modeling techniques to understand, design, and optimize catalysts for bio-oil upgrading.

In the search for efficient catalysts towards bio-oil HDO refining, a wide range of nickel-based single-atom alloy (SAA) catalysts denoted as M-Ni(111) (i.e., M = Pd, Pt, Cu, Co, Fe, Ru, Re, Rh, V, W, and Mo) were systematically explored using density functional theory (DFT) and microkinetic modeling. Results established stability, electronic properties, and activity of four bio-oil derivatives in vacuum and O*-induced environments, guiding the synthesis of cost-effective SAA combinations. Turning to bio-oils steam reforming, a thorough DFT-screening combined with ab initio molecular dynamics (AIMD) study of 26-doped M-Ni-based SAA catalysts identified 3 promising high-performing bimetallic SAA M-Ni combinations, i.e., CuNi, Zn-Ni, and Ag-Ni that passed the costing/stability screening protocol and dehydrogenation activity, while Pd-Ni provided optimal H2 activity and regeneration ability. Further screening for trimetallic M1-M2-Ni co-dopants yielded stable single-sites with balanced adsorption and reduced coking susceptibility.

Controlling the zeolite support acidity by tunning the Brønsted acid sites plays a critical role in the catalytic upgrading of bio-oils. Using reactive force-field-based molecular dynamics (ReaxFF-MD) simulations, we explored BEA zeolites modified with 9 different silica-to-alumina ratios to elucidate their acid-catalyzed deoxygenation selectivity for oleic acid upgrading to drop-in biofuels. An optimal SAR of 37.4 was pinpointed for improving the long-chain fatty acid deoxygenation upgrading, achieving maximum oleic acid conversion to gasoline and diesel biofuels, dovetailed with moderate coking higher heating value and yield in ex situe H2 environment. Finally, a process modelling and techno-economic assessment (TEA) of domestic bio-oil feedstocks upgrading within the UAE demonstrated that dates-extracted palm oil upgrading offers an economically feasible direction for a bio-refinery modelled based on inputs from the molecular-level catalytic upgrading mechanism.

Date of Award	20 Jul 2024
Original language	American English
Supervisor	MARIA LOURDES VEGA FERNANDEZ (Supervisor)