Hydrolysis of lignocellulosic biomass by a modified organosolv method on a biorefinery perspective – example of Miscanthus χ giganteus

Roque, Ricardo Miguel Nunes (2014). Hydrolysis of lignocellulosic biomass by a modified organosolv method on a biorefinery perspective – example of Miscanthus χ giganteus. University of Birmingham. Ph.D.

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Abstract

Concerns about climate change and our awareness on energy security have risen during the last decades leading the search for new forms of energy to reduce the world’s dependence on fossil fuels. Bioenergy has been proposed as one route to contribute signiﬁcantly to meet global energy demand by using renewable sources of energy.

The overall objective of this work was to study and optimise a hydrolysis treatment of lignocellulosic biomass but particularly of Miscanthus \(\chi\) giganteus under the biorefinery concept. A modified organosolv method using subcritical water, ethanol and carbon dioxide on a high-pressure batch reactor was proposed and tested for its efficacy on the hydrolysis and fractionation of Miscanthus into its lignocellulose main components, hemicellulose, cellulose and lignin. Temperature (80–200\(^0\)C), reaction time (5–60 min), ethanol concentration (0–70%), carbon dioxide initial pressure (10–55 bar) and load size (2.5–15 g) were the parameters studied and respective ranges. Optimisation models for solubilisation and delignification were obtained and validated using a central composite design based on a response surface methodology. According to both models temperature is the parameter that affects hydrolysis the most obtaining the highest hydrolysis solubilisation and delignification at 200\(^0\)C. On the other side CO2 initial pressure was not significant, what should be further investigated in the future at higher pressures.

Reducing sugars quantification obtained a maximum concentration of 2g/10g Miscanthus by DNS assay with an optimal temperature to hydrolyse hemicellulose from 140 to 180\(^0\)C. FTIR analysis of each fraction confirmed a successful separation of the biomass main components with a reduction in the cellulose fibres crystallinity. Temperature was considered the most significant parameter to fractionate biomass with the highest temperature (200 \(^0\)C) being the one that produced a better quality fibres, supernatant and lignin in terms of contamination by the other fractions. However, results also showed that higher temperature tends to oxidise lignin. Fibres analysis by scanning electron microscopy showed that fibre structure was preserved but presented lignin-type globules on their surface indicating lignin reprecipitation.

Type of Work:

Thesis (Doctorates > Ph.D.)

Award Type:

Doctorates > Ph.D.

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