A hot filtration unit downstream of a 1kg/h fluidised bed fast pyrolysis reactor was designed and built. The filter unit operates at 450oC and consists of 1 exchangeable filter candle with reverse pulse cleaning system. Hot filtration experiments up to 7 hours were performed with beech wood as feedstock. It was possible to produce fast pyrolysis oils with a solid content below 0.01 wt%. The additional residence time of the pyrolysis vapours and secondary vapour cracking on the filter cake caused an increase of non-condensable gases at the expense of organic liquid yield. The oils produced with hot filtration showed superior quality properties regarding viscosity than standard pyrolysis oils. The oils were analysed by rotational viscosimetry and gel permeation chromatography before and after accelerated aging. During filtration the separated particulates accumulate on the candle surface and build up the filter cake. The filter cake leads to an increase in pressure drop between the raw gas and the clean gas side of the filter candle. At a certain pressure drop the filter cake has to be removed by reverse pulse cleaning to regenerate the pressure drop. The experiments showed that successful pressure drop recovery was possible during the initial filtration cycles, thereafter further cycles showed minor pressure drop recovery and therefore a steady increase in differential pressure. Filtration with pre-coating the candle to form an additional layer between the filter candle and cake resulted in total removal of the dust cake.

No description available.

Some eukaryotes are able to gain access to otherwise well-protected carbon sources in plant biomass by exploiting microorganisms in the environment, or harboured in their digestive system. One such organism is the European black slug, Arion ater, which takes advantage of a gut microbial consortium that can break down plant tissues, including the widely available, but difficult to digest, carbohydrate polymers in lignocellulose. This ability is considered to be one of the major factors that have enabled A. ater to become one of the most widespread plant pest species in Western Europe and North America. Here we have identified the A. ater gut environment as a target for metagenomic study through identification of cellulolytic activity of bacterial origin. Next generation sequencing technology was used to characterize the bacterial diversity and functional capability of the gut microbiome of this notorious agricultural pest. Over 6 Gbp of gut metagenomic community sequences were analysed to reveal populations of known lignocellulose-degrading bacteria, along with abundant well-characterized bacterial plant pathogens. This study also revealed a repertoire of more than 3,000 carbohydrate active enzymes (CAZymes), indicating a microbial consortium capable of degradation of all components of lignocellulose, including cellulose, hemicellulose, pectin and lignin. Together, these functions would allow A. ater to make extensive use of plant biomass as a source of nutrients. This thesis demonstrates the importance of studying microbial communities in understudied groups such as the gastropods, firstly with respect to understanding links between feeding and evolutionary success and, secondly, as sources of novel enzymes with biotechnological potential, such as CAZYmes that could be used in the production of biofuel.

No description available.

1,4-Dimethylnaphthalene (1,4-DMN) is a pesticide used for inhibiting the sprouting of stored potatoes, and therefore prolonging the storage time. It is registered for commercial use in different parts of the world (e.g. USA and New Zealand) and its registration process in the EU is at an advanced stage. Limited information is available regarding the behaviour and fate of this pesticide in the environment, and therefore, various studies are required in this field. In such studies, analytical methods for the determination of 1,4-DMN in the different environmental samples are a core element. This work aims to contribute to the knowledge about this pesticide, particularly in the analytical and environmental aspects. Several methods were developed in this work for the determination of 1,4-DMN in environmental samples. HPLC was selected for the final separation and quantification. The development of HPLC separation methods for 1,4-DMN and other related compounds were achieved by the practical step-by-step approach, the use of chromatographic-simulation software, or by a combination of the two approaches. A mixture of seven dimethylnaphthalene isomers and other related naphthalene compounds was used to study the behaviour of these compounds toward the different chromatographic conditions in reversed-phase HPLC with UV detection. This study provides a good understanding of the effect of different chromatographic conditions on the HPLC separation of the compounds studied, and forms a background for the subsequent work in method development. Optimised methods for the separation of this mixture were finally achieved which provide good separation of most of the mixture’s components. In the light of the above study, an HPLC-UV separation method for routine analysis of 1,4-DMN was developed and validated. This method provides good linearity (r2 > 0.999) in the range 0.2 –300 µg/ml, and good precision with %RSD values of 3.45 % and 0.37 % for 0.02 (method LOD) and 50 µg/ml levels. The method was found to be accurate by comparing it statistically to a gas chromatographic method. The two methods were found to produce results which were not significantly different (at the 5% level) by using a regression test. Several extraction procedures were then compared for their efficiency in extracting 1,4-DMN residues in potato samples, and also for their suitability for routine HPLC analysis. A final HPLC method (TMP/Heat method) for the analysis of 1,4-DMN residues in potato samples was then achieved and validated. This method is based on extracting 1,4-DMN from potato peel with a mixture of ethanol and 2,2,4-trimethylpentane (7:3) by heating at 50 oC. A liquid-liquid extraction is achieved (in the same extraction flask) with the water derived from the fresh peel, to end up with 1,4-DMN concentrated in the 2,2,4-trimethylpentane layer. The evaluation of the volume of this layer, in addition to the correction of any loss of 1,4-DMN during the analysis, was achieved by using 2-methylnaphthalene as an internal standard. 2-methylnaphthalene was selected as a suitable internal standard for 1,4-DMN analysis after comparing it with several other compounds (2-ethylnaphthalene, 1-ethylnaphthalene and n-butylbenzene) for the similarity of their behaviour to 1,4-DMN in the extraction and chromatographic separation processes. An aliquot of the 2,2,4-trimethylpentane layer was then analysed directly by HPLC. This method was validated in the range 0.015 to 3 µg/g of potato fresh weight. It was found to have adequate speed, detection sensitivity (LOQ of 0.015 µg/g of potato fresh weight), accuracy (recovery between 90.3 to 106 %) and precision (%RSD between 1.7 to 10.5 %) for routine analysis of 1,4-DMN residues in treated potatoes. For the determination of natural 1,4-DMN in potatoes, a new analytical method was developed for the extraction and quantification of 1,4-DMN at trace levels. The method (ACN/PROP method) uses the advantage of injecting large volumes (100 µl) of the extracts containing 1,4-DMN directly to the HPLC as a means of enhancing the detection sensitivity. This advantage was achieved by using a mixture of acetonitrile : 2-propanol (7:3) as the extraction solution, which is compatible with the mobile phase and miscible with the water derived from potato peel. The resulting extracts were ready for direct analysis with HPLC with no further clean up. In addition, a high ratio of sample : solvent (1:1) was used for further enhancement of the detection sensitivity. This method was validated at 7.5 and 15 µg/kg of potato fresh weight. It was found to be adequate for trace analysis of 1,4-DMN in potatoes with a limit of quantification of 4.5 µg/kg of potato fresh weight, recovery values between 86.4 to 87.1 % and a precision expressed by %RSD between 4.0 to 7.9 %. The ACN/PROP method was used for the determination of the natural levels of 1,4-DMN in potato peel and flesh, in addition to some other plant materials. A small peak was detected in the chromatogram of potato peel extracts, at the right retention time for 1,4-DMN, with an area equivalent to a level of about 4 µg/kg of potato fresh weight. However, it was not possible to confirm the identity of this peak due to its low level and the high background noise. There was no sign of the presence of 1,4-DMN in any of the rest of the plant materials analysed which were potato flesh, apples, orange, celery, spring onion, carrots, rhubarb and poppy seeds. A headspace method and preliminary work using Soxhlet extraction were also examined for the determination of natural 1,4-DMN in potatoes. However, some shortcomings in the development of the methods obstructed the achievement of adequate results. The ACN/PROP method was also optimised for rapid routine analysis of the residues of 1,4-DMN in treated potatoes. The optimised method was validated in the range of 0.03 to 3 µg/g of potato fresh weight, and found to provide good accuracy (recovery between 89.6 to 93.2 %) and precision (%RSD between 1.6 to 7.3 %). In addition, it is a rapid, easy and straightforward procedure. Because of its advantages, this method was used for different applications regarding the distribution and removal of 1,4-DMN residues in treated potatoes. To investigate the distribution and removal of 1,4-DMN residues, potato tubers treated and stored for about 18 weeks under commercial storage conditions were analysed for 1,4-DMN residues. 1,4-DMN residues in individual tubers were in the range of 0.63 to 1.16 µg/g fresh weight after 18 weeks of storage with a low variability factor of about 1.5. The residues were found to be concentrated in the peel layer of the tuber and have relatively even distribution across the different parts of the tuber surface. Washing 1,4-DMN-treated potatoes with water and some other solutions was found to remove insignificant amounts of 1,4-DMN residues from potato tubers. In contrast, heating the peel of 1,4-DMN-treated potatoes in an oven at 75 ± 5 oC removed up to 96 % of 1,4-DMN residues.

No description available.

No description available.

There is huge need to develop an alternative to hydrocarbons fuel, which does not produce CO2 or contribute to global warming - 'the hydrogen economy' is such an alternative, however the storage of hydrogen is the key technical barrier that must be overcome. The potential of graphitic nanofibres (GNFs) to be used as materials to allow the solid-state storage of hydrogen has thus been investigated. This has been conducted with a view to further developing the understanding of the mechanism(s) of hydrogen storage in GNFs and modifying the material structure to maximise the amount of hydrogen that can be reversibly stored in the material. GNFs were synthesised using chemical vapour deposition (CVD) with careful control of temperature and gas mixture to create predominately herringbone GNFs from both Iron and Nickel catalysts. Within this, it was found that once GNF growth has been initiated under certain conditions, alteration of those conditions does not alter the fundamental structure of the GNF synthesised, but can increase the carbon yield, although reorientation of the surfaces was observed. The GNFs synthesised were subsequently chemically (acid washed and CO2 oxidised) and thermally treated to remove the residual CVD catalyst and alter their surface structures in an attempt to allow dihydrogen molecules to penetrate and adsorb onto the internal graphene layers. However, it was found that after initial growth, the surface layers of the GNFs became re-orientated parallel to the fibre axis - representing a large energy barrier to adsorption onto the surfaces of the internal graphene layers. By careful use and control of conditions, this re-orientated layer can be removed to yield GNFs with cleaned surfaces. Once GNFs with cleaned edges had been synthesised, these were modified to remove oxygen species from their surfaces. To further develop the understanding of the potential hydrogen uptake mechanisms, Pd particles were introduced to the GNF surfaces to act as catalyst gateways. By carefully controlling the variables of the incipient wetness process, a variety of morphologies and structures were synthesised. This allowed the precise determination of the hydrogen uptake mechanism occurring in samples by Kubas binding, Dissociation or Spill-over mechanisms. All of the GNFs created have had their hydrogen uptake capacities precisely determined using a Sieverts apparatus designed and constructed by the author. None of the samples were found to adsorb any significant levels of hydrogen (>0.1 wt%), regardless of the treatments applied to them – this result has been discussed in light of the existing claims for high hydrogen uptake in GNFs made within the literature. The conclusion of this thesis is that no hydrogen uptake capacity could be observed in the GNFs synthesised during the project, however, the development of the uptake mechanisms and GNF structures has led to suggested modifications that may yield GNFs suitable for storing large quantities of hydrogen (i.e. in excess of US-DOE targets).

Nearly half the worlds population is dependent on wood as their primary energy source. Therefore with deforestation becoming increasingly prevalent in many regions of the developing world, there is an urgent need to improve combustion efficiency of stoves or to find alternative fuels. Densification of loose biomass residues into briquettes is a means of upgrading the feedstock material. Briquettes are easier to store, more convenient to use and burn at a more steady and controlled rate than loose biomass. This investigation focuses on understanding some of their combustion characteristics and the relationship to the briquette design and manufacture process. The social context of the work is presented through an informal case study considering the potential of briquetting in Ghana. The initial experimental work focuses on developing a process to manufacture newspaper briquettes of consistent quality at low-pressures using a wet technique, and a method to burn them in a controlled way is suggested. These techniques were used to carry out a study on rectangular slab-shaped briquettes, looking at the effect of process variables (density, moisture content and size) on briquette burn-rate. An analytical expression for the normalised burn-rate (NBR) of a briquette in free-air, in terms of these of these variables, was found by numerical fitting. The effect of shape on combustion was also experimentally investigated using cylindrical briquettes with a central hole (holey briquettes) burning in free-air and an analytical expression was derived for their burn rate. The NBR behaviour of sawdust briquettes, rapeseed oil residue briquettes as well as slabs of pine wood was then studied. Rapeseed oil residue has a very different calorific value from that of newspaper, and a method was suggested for predicting the difference in rate as a function of difference in calorific value. In the second phase of the work, a numerical model of pyrolysis was developed. The model assumed that heat transfer through the fuel limited the rate of pyrolysis. The thermal parameters (thermal conductivity, heat capacity and thermal diffusivity) were estimated using a heat probe method, and the kinetic parameters found by numerical optimization. The model was shown to predict, for newspaper briquettes, the experimentally observed size dependent behaviour of the normalised burn rate, and the trend observed for the effect of changes in density. The model was applied to predict the effect of changes in a briquettes thermal parameters on burn rate, and an analytical expression found by numerical fitting. This provides a means of estimating relative changes in burn rate due to changes in fuel properties, and forms the basis for a pyrolysis sub-model for use in stove optimisation. Such a model has the advantage of being able to vary key, easily quantifiable and easily controlled solid biomass briquette properties relative to the behaviour and properties of a well understood fuel such as wood. In the final part of the study, some of the limitations of the numerical model are explored by completing a sensitivity study investigating the relative effect of some of the key assumptions made.

Hydrogen is an ideal energy carrier as it only produces water as a by-product. However, technical and social issues first need to be overcome in order to achieve such economy. In particular, this work focuses on solid state hydrogen storage as it is a key technological challenge. Herein, potential candidates currently investigated are porous materials that physisorb molecular hydrogen with fast kinetics and good reversibility in order to meet mobile transportation requirements. The goal is to be able to optimize the sorption properties of a compound by tuning critical parameters such as its pore size and/or its specific surface area. Carbon nanofibres were investigated as potentially cost-efficient materials. Engineering routes such as the integration of hetero-species by nitrogen doping and exfoliation / intercalation were performed on various carbon nanostructures affecting the surface topology of the engineered compounds compared to the as-prepared materials although the excess uptakes at 77 K and 20 bar remained low ca. 0.6 wt. %. Metal-organic frameworks are a promising class of porous materials and are currently strong competitors as hydrogen storage media thanks to their flexibility in structure design. A series of Cu (II) - frameworks have been found to have exceptional sorption properties at 77 K and 20 bar up to 7 wt. %. The successful combination of neutron techniques at NIST-CNR and ISIS-RAL enabled a clear insight of the adsorption site distribution of two Cu (11) - frameworks using para-H2 and D2 as probing gases. A common feature for the MOFs investigated was that dihydrogen preferentially coordinated to the exposed metal centres ca. 2.4 Å, followed by sorption at two discrete sites located within triangular windows connecting the MOF cavities. It revealed the co-existence of preferential site-specific with non-site specific adsorption within the pore structure which is different from the common concept of dihydrogen interacting with a homogeneous surface. It was also possible to follow the dynamics of hydrogen molecules at different coverage of the surface through the rotational transitions of the para-H2 molecule.