Dwindling global resources necessitate the investigation, and development of more sustainable,
optimised, and effective processes beyond conventional practices. Therefore, the present work
explores novel synthesis methods and environments. The areas investigated are: hydrothermal
carbonisation, alcohol/water mixtures, and aerosol-assisted sol-gel synthesis.
Hydrothermal carbonisation is an emerging thermochemical conversion process. Herein
hydrothermal carbonisation processing is performed on two novel biomass waste feedstocks,
bread waste and avocado seeds. Both of these feedstocks are unsuitable for animal feed or other
thermochemical processes and therefore are generally sent to landfill. The valorisation of these
waste streams would therefore produce value from a genuine waste product. Hydrothermal
carbonisation of bread waste is investigated at a range of different processing temperatures
(160-200 °C) and retention times (30-90 min), in addition to two different pressurising gases
helium and carbon dioxide. Under carbon dioxide at 200 °C after 60 mins the hydrochar
displayed exceptional energy density at 36 MJ Kg-1 and contained a large portion of volatile
matter (58.8%). Thus, bread waste demonstrated high potential in producing a renewable solid
fuel or activated carbon material. Hydrothermal carbonisation of avocado seeds examined the
potential to perform a one-pot catalyst synthesis procedure. A mixture of magnetite and
heamatite was supported on the hydrochar in situ to yield a magnetic carbon composite
material. This catalyst showed full regioselectivity in an exemplary catalytic testing procedure
as well as viable adsorption of indigo carmine (~49 mg g-1). Therefore, the efficient production
of catalytic materials is exhibited with potential application to a wide range of different
lignocellulosic wastes and catalytic metals.
The molecular interactions within alcohol/water mixtures at both ambient and hydrothermal
(sub-critical) conditions was analysed using Fourier-transform infrared spectroscopy.
Mathematical analysis methods such as deconvolution, and perturbation induced 2D
correlation analysis were performed to analyse the data. Using this methodology the molecular
transition points discussed in literature for ambient alcohol/water mixtures were identified by
trends in blueshifting and excess intensity of the crucial peaks O-H and C-O stretching.
Following this, novel information about the molecular dynamics of alcohol/water mixtures
under hydrothermal conditions was acquired. Further to this, the effect of ethanol/water
mixtures on the hydrothermal carbonisation of bread waste and avocado seeds was
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investigated. Whilst the properties of hydrochar were affected by varying ethanol concentration
at lower processing temperatures these effects were reduced at higher processing temperatures.
Aerosol-assisted sol-gel synthesis mechanisms were investigated using optical trapping
instrumentation at the Central Laser Facility. The initial stages of synthesis were imitated by
trapping a single droplet of the precursor solutions using focussed light. This droplet was
monitored using Raman spectroscopy and heated externally, therefore replacing the space
domain in the aerosol flow tube with a time domain. From this investigation, evidence against
the expected reactions based on bulk sol-gel synthesis was obtained. Furthermore, insight was
gained into the effects of different compounds in the precursor solution on droplet stability and
evaporation. Finally, an alternative reaction mechanism to that observed in bulk sol-gel
synthesis was proposed based on the observed Raman spectroscopic data.
