An estimated 60 MT carbon/year is available in Canada from forestry, agricultural, and municipal solid waste (MSW), with an energy content ranging between 1.5 and 2.2 EJ/year - equivalent to 18% and 27% of the energy derived from fossil fuels. Besides fuels, transportation problem of heavy oils obtained from Alberta oil sands can be potentially solved by blending the biomass derived oils and chemicals with heavy oils, thus saving on the high cost of diluents. However, setting up a “Bio–refinery” is technologically challenging, since biomass contains oxygen and is a solid material. To convert biomass to fuels and chemicals, C–O bonds need to be selectively cleaved, without breaking the C–C bonds. Thus, utilizing the processing knowledgebase of petroleum may not be possible and novel catalysts and processes need to be developed. The proposed research focuses on the two non-biological pathways to process biomass, viz., (i) liquid phase inorganic catalytic pathway and (ii) high temperature pyrolytic pathway. Liquid phase processing is more suitable for selectively producing bulk/fine chemicals and platform intermediates and pyrolysis is a preferred choice for the delocalized processing of bio-based feedstock to produce bio-fuels.
Liquid phase catalytic processing of biomass: Grand challenges associated with the liquid phase processing of biomass include (a) the development of novel, multifunctional and stable catalysts for its selective conversion, (b) identifying an appropriate solvation medium, since biomass is a solid and needs to be dissolved in a solvent; solvent environment alters the conversion and selectivity and (c) minimizing the formation of humins, which are insoluble polymeric species formed during biomass reactions and result in significant loss of carbon and damage the catalyst (analogous to coke formation in the petroleum industry). Hence the proposed research aims to address these challenges by (i) developing molecular understanding of the catalytic reaction mechanisms and associated energetics, (ii) characterizing catalysts and identifying key descriptors of their activity and selectivity, (iii) selecting and screening potential solvents by developing a fundamental understanding of the role of solvents in biomass processing and (iv) discovering potential routes, precursors and kinetics of humins formation.
Pyrolysis of biomass: High temperature pyrolysis in the absence of oxygen converts biomass to bio-oil. However, the bio-oil produced from pyrolysis is unsuitable for direct use, storage and transportation due to its poor stability, low energy density, and extremely corrosive nature arising from the high oxygen content. Commercialization of pyrolysis process is only possible if the bio-oil can be made stable and amenable for storage and transportation. Catalytic hydrodeoxygenation of bio-oil is an effective strategy to reduce the oxygen content in bio-oil and make it suitable for transportation and further upgradation. Hence the proposed project aims to develop novel catalysts to selectively remove oxygen from oxygenates in bio-oil, like furans, alcohols, aldehydes and anhydrosugars.
Approach: A combined computational and experimental approach is taken to investigate the catalytic biomass processing and the role of solvents in it. Due to rapid advancements in computational technology and developments in computational chemistry (with the ability to model reactions and reaction dynamics at a molecular level, in the presence of a solvent and at finite temperatures), it is now possible to probe reactive processes and solvation, for biomass species and humins precursors, in real experimental conditions (without having to only rely on calculations in gas phase) and with dynamic information. However, the modelling approach alone may not succeed either, since it would not be computationally feasible to explore all the possible reaction pathways, leading to the formation of humins and platform intermediates. Hence, we believe that a marriage between experimental and first-principles, quantum mechanical condensed phase molecular modelling approaches is best suited for studying catalytic biomass chemistry. Additionally, experimental inputs are crucial to develop relevant models for active catalysts in modelling and to identify chemical structure of humins.