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Title: Bio-oil generation and upgrading using catalysts towards its integration into a crude-oil refinery
Author: Sanna, Aimaro
ISNI:       0000 0004 2720 2067
Awarding Body: University of Nottingham
Current Institution: University of Nottingham
Date of Award: 2011
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Currently biomass covers around 85% of the total renewable energy supply of the United Kingdom together with landfill gas and waste combustion. However its potential is still underutilized. Indeed, its conversion in fuels, energy and chemicals could revitalize rural economies, limit the dependence on foreign oil imports, and improve the environment by reducing fossil fuel consumption and thus reducing greenhouse gases. Recently, new pathways to convert the biomass into intermediate liquid namely bio-oil have been investigated. Pyrolysis is a promising technology to produce renewable fuels from biomass especially decentralized at point of production. However, the quality of bio-oil still remains a major limitation in terms of oxygen content and calorific value. The overall aim of this project was to contribute to the understanding of the engineering aspects in which biomass could be economically converted to chemicals, fuels and energy using catalytic pyrolysis to enhance the quality of the bio-oil. This can enable the production of intermediate bio-liquids with properties similar to those of petroleum, allowing the use of the existing crude-oil refinery settings for bio-oil upgrading into fuels. The integration of the bio-oil into a crude-oil refinery would sensibly decrease the economical disadvantage of biomass compared to fossil fuels. This work proposes an innovative three-step catalytic process that converts biorefinery residues, such as spent grains, into bio- oil by catalytic pyrolysis. The water insoluble fraction of the bio-oil (WIBO) is converted into a solid residue that possesses similar characteristics to those of coal, and a liquid product called bio-crude by a process name Thermo-t similar to the visbreaking process used to upgrade the quality of crude-oil heavy distillation residues. The water fraction (WSBO) is then converted into alcohols and alkanes using hydrogenation reactions. Despite the fact that the original biomass contains undesirable high oxygen (39-46 wt%) and moisture contents, there was a clear improvement in the properties of the bio-oils generated by catalytic pyrolysis that presented oxygen content of 26- 31 wt% and the final Thermo-t residue as the oxygen content was reduced by over 70% to 9-14 wt% on average. Catalytic pyrolysis was able to produce a bio-oil with less oxygen and nitrogen, high aliphatics and hydrogen using activated serpentine and olivine at low temperatures (370-430 QC). The activated materials seem to be beneficial to the bio-oil energy content that increase from less than 20 MJ/kg in the original biomass to 24-26 MJ/kg and finally to 29-37 MJ/kg after Thermo-t process. About 70-74% of starting energy remains in the bio-oil using ACOL and ACSE at 430 QC, respectively, while only 52% is retained using alumina at the same temperature. Finally, bio-crudes and bio-cokes from Thermo- t process retain 30 and 36% of the starting energy, respectively. The WSBO can be catalytically hydro-treated by Aqueous Phase Processing in a 1st stage at temperatures lower than 130 QC to reduce the organics removed as solid depositions to only 7 wt%, avoiding the typical catalyst deactivation of traditional hydro-treating technology. Then, in a 2nd stage at 220-250 QC, 93% of the partially deoxygenated bio-oil functionalities, such as ketones, aldehydes, aromatics and sugars are converted in much more stable functionalities that leave a final product with acidity and stability much compatible with current fossil fuels. Overall, this study has shown that there is a great technical scope for converting biomass into high-value products that can help to off-set fossil fuels.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available