SACM - United Kingdom
Permanent URI for this collectionhttps://drepo.sdl.edu.sa/handle/20.500.14154/9667
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Item Restricted Photocatalytic Reforming of Lignocellulosic Feedstocks for H2 Production using TiO2-based Catalyst(The University of Manchester, 2024-06-26) Aljohani, Meshal; Fan, Xiaolei; Christopher, HardacreThe demand for energy has increased massively, mainly supplied by fossil fuels with significant carbon emissions. Hydrogen (H2) emerges as an efficient and clean energy carrier, having many promising characteristics (such as higher heating value and zero carbon emission after combustion) to replace fossil fuels. Solar-driven photocatalytic reforming (photoreforming, PR) of biomasses (such as cellulose and lignin) at ambient conditions presents a promising solution to produce renewable H2 due to the use of (i) biomass (widely abundant in nature, sustainable and theoretically carbon neutral) and (ii) solar energy (i.e., the sun as the largest energy resource driving the catalysis). Current PR processes mainly employ cellulose and bio-derived chemicals such as bioethanol. Comparatively, although it is very challenging, the direct use of lignin for H2 production via PR can be advantageous. This PhD thesis employed platinised TiO2 catalysts to study the PR of model aromatic compounds, purified and IonSolv-extracted lignin and cellulose, and raw biomass feedstocks to produce H2. While PR of aromatic compounds and lignin yields comparable and low levels of H2 production (4.8−6.6 μmol gcat−1 h−1) compared to cellulose (~62.8 μmol gcat−1 h−1) due to poisoning by intermediates, alternating between anaerobic and aerobic atmospheres resulting in a threefold enhancement in H2 production from the PR of lignin. In addition, Pt nanoparticles loaded on TiO2 using an in-situ photodeposition method enhanced the production of H2 significantly from the PR of lignin and aromatic substrates compared to ex-situ methods. The PR of isolated cellulose pulps from various bioenergy crops showed the highest H2 production, while derived lignin was the lowest. The variations in H2 production from bioenergy crops were found to be unrelated to the differing composition of cellulose, hemicellulose and lignin. The interaction strength of bioenergy crops with water, as observed by NMR relaxometry, was determined to influence H2 production, correlating with H2 production. In summary, this thesis investigates the challenges of lignin PR, proposes mitigation strategies, and identifies factors impacting the PR of lignocellulosic feedstocks for efficient H2 production.17 0Item Restricted Waste Gasification for Hydrogen Production(University College London (UCL), 2023) Lahig, Talal; Materazzi, MassimilianoThe vision for hydrogen being at the forefront of the energy transition is already in existence, due to its high energy density and its zero greenhouse gas emissions during use. Current production methods include steam-methane reforming and coal gasification, which lead to high CO2 emissions that will amplify climate change with increasing demand. Opposite to this is waste gasification, which provides a sustainable gateway for clean hydrogen production as waste contains biogenic carbon and can attain negative carbon emissions when coupled with carbon capture and sequestration (CCS). This study concentrates on the development of a novel approach to predict the pyrolysis yields of diverse waste based on its components of cellulose, hemicellulose, lignin, polyethylene and polypropylene. The work demonstrates that the flexibility and predictive capability of an air-steam bubbling fluidised bed (BFB) gasification model for a wide array of waste types is improved. The model was rigorously validated against pilot plant data through comparison of the outlet syngas composition, the tar content, the heating value and the temperature profile across the fluidised bed gasifier at a range of conditions. The effects of the feedstock type, equivalence ratio (ER) and the steam-to-waste ratio (STWR) are investigated to determine the optimal conditions for achieving a high H2 yield, while maintaining medium heating values. It was found that a H2/CO ratio of 2.37 is achieved with an ER of 0.30 and a STWR of 1.2 using sugarcane bagasse.34 0Item Restricted Novel Lignin from Pine Wood Chips using Microwave-Assisted Organosolv Method(Saudi Digital Library, 2024-01-01) Aljuhani, Abdulhameed Hamed; Laybourn, AndreaThe microwave-assisted Organosolv method for lignin extraction from pine wood chips, conducted in temperatures between 165°C to 205°C, is thoroughly examined in this study. Critical insights emerge as the highest lignin yield, standing at 25.237%, is achieved at 205°C, while purity reaches its pinnacle at 88.3% when operating at 195°C. Moreover, an optimal residence time of 30 minutes was optimised to achieve maximum yields of 1.93% of lignin-rich material. Microwave technology demonstrates advantages such as rapid heating and environmental friendliness, underscoring the need for judicious temperature-energy balance. A robust lignin calibration curve has been established, facilitating the precise determination of lignin concentration, ultimately revealing a lignin content of 19.582% with an STD of ±2.3% in the initial pine wood chips. These insights could be used to promote the utilisation of lignocellulosic biomass sustainably, emphasising the significance of temperature management in practical applications.20 0