Colloidal synthesis can be used to functionally design the morphology of nanoparticles for specific applications. A sol-immobilisation technique has been successfully employed to synthesize bi-metallic gold and palladium nano-catalysts. The ability of a gold and palladium bimetallic catalyst to selectively oxidise toluene has been used to enhance the hydrocarbon selective catalytic reduction (HC-SCR) of NOx. The influence of reactor configuration on performance is also evaluated and an alternative HC-SCR system design is presented. The capacity of gold and palladium nano-catalysts to produce benzonitrile at low temperatures was further explored. Both nitroxidation and ammoxidation synthesis routes were employed to maximise nitrile productivity. The rate limiting partial oxidation step is 'by-passed' by utilising benzyl alcohol as a reactant, and the subsequent production of benzonitrile is evaluated for an array of Au-Pd catalysts. The ammoxidation of an aliphatic alcohol; ethanol is also examined. Currently 90% of ethanol production is sourced from biomass, with bio-ethanol considered a sustainable platform chemical of the future. The influence of metal composition, preparation method, metal loading and support selection on catalytic performance is assessed. The stability of the gold and palladium catalysts is examined and deactivation mechanisms are explored. A potential process for the ammoxidation for ethanol is presented and the various unit operations required for a high purity grade acetonitrile product are discussed.

Carrying out oxidations on an industrial scale in an environmentally sustainable manner can be challenging with currently available methods. Consequentially, the pharmaceutical industry avoids transformations involving oxidations where possible. Developments over the past few decades have brought catalytic processes to light that can carry out oxidations using simple terminal oxidants, such as O2 and H202• In particular, ligand-promoted Pd(II) complexes have been shown to be capable of oxidising alcohols and olefins to carbonyl compounds, producing water as the principal byproduct. In this thesis, aerobic alcohol oxidations and Wacker-type olefin oxidations are studied, with the aim of minimising Pd catalyst loadings through the stabilisation of the catalyst using ligands. Continuing on from previous work on aerobic alcohol oxidations promoted by the 8-hydroxy-2- quinolinesulfonic acid (HSA) ligand, study of functionalized imines and NHC ligands shows the uniqueness of the HSA ligand in enhancement of the oxidation of 2-octanol to 2-octanone. In [C4mpyrr] [FAP] the HSA complex was seen to deactivate but Pd-black was not seen to form, suggesting that the ionic liquid is stabilising the formation of Pd nanoparticles. Supporting of the HSA complex on a SILP was shown to provide similar catalytic activity as in the bulk phase, but requiring significantly smaller volumes of ionic liquid to function. For the Wacker oxidation of olefins, cationic triflate Pdll-complexes were investigated in weakly coordinating solvents, which were found to be active catalysts in a pressurised 8% O2 in N2 environment but resulted in rapid olefin isomerisation. A Pd(OAc)2/H202,-mediated oxidation system in acetic acid was then developed, promoted by the use of ligands such as 2-(2'-pyridyl)benzoxazole. The catalyst could yield 69% acetophenone from styrene under room temperature conditions in 24 hours. Also, the concept of a thermally phase switchable betainium ionic liquid/H2O solvent was trialed for the simplified recovery of the product and catalyst recycle post-reaction.

Radiofrequency (RF) heating of composite magnetic materials enables direct and efficient transfer of energy to the sites of catalytic reactions within a chemical reactor. The materials consist of an RF heated magnetic component and a catalytic component. The two components can be optimised separately according to the demands of the application. This approach was applied to continuous direct amide formation from amines and carboxylic acids under flow conditions, a reaction of great interest and potential to the pharmaceutical industry. The RF heat generation of NiFe2 04-TiO2 magnetic materials were optimised. Catalyst screening showed sulfated commercial P 25 Ti02 to give good catalytic activity in the reaction of 4-phenylbutyric acid with aniline in xylene. The composite material was prepared mechanochemically from a mixture of the optimised magnetic and catalytic components. A continuous RF heated reactor was developed, consisting of a 6 mm diameter insulated micro packed-bed reactor placed within an RF induction coil. The reactor was operated at 7 bar and up to 200°C for up to 10 hours. The sulfated composite achieved t he highest activity of up to 50% conversion in a single pass and the least deactivation. Temperature profiles obtained from the analytical solutions were combined with a catalyst kinetic model to form a reactor model, which was validated by the experimental results. The concentration profiles obtained from the reactor model gave an insight into the mechanism of the observed process intensification - the temperature rise along the RF heated reactor axis helped to offset the reduction in the reaction rate as a result of depletion of the reactants. This novel type of process is therefore most suited to reactions with high reaction rate orders and it would therefore be of great interest to investigate other processes where this effect could be demonstrated.

A series of hydrophobic ionic liquids (ILs) have been employed to extract acetic acid from aqueous solutions at 101.3 KPa. This study was carried out using tetradecyltrihexylphosphonium cation ([P666, 14]+) combined with two series of anions: benzoate and long-chain carboxylate based anions. For comparison, the extraction of organic solvent MTBE was also investigated. The long-chain carboxylate based ILs showed a larger two phase region and high extraction efficiency. [The performance of a selection of inorganic salts, organic salts, and ILs in the extractive distillation for the (HOAc + H20) system was analyzed by vapour-liquid equilibrium under atmospheric pressure. The results indicate that the inorganic salts showed a salting-out effect of acetic acid while all the organic salts and ILs presented salting-out effect of water. All the ILs investigated showed a notable salting-out effect of wate which implied that an IL might be a promising additive in extractive distillation processes. Supported materials were investigated in extractive distillation for the (HOAc + H20) system. The performance of a selection of organic and ILs functionalized supports was analyzed by vapour-liquid equilibrium at 101.3 kPa. Leaching problem of the imidazolium based IL tethered support, blockage problem of the powder support and the saturation of the support during continuous distillation are still the challenging parts in this work. The UNIFAC method was employed to correlate and predict the LLE and VLE data for IL/salt modified systems. The results illustrated that the UNIF AC model has the ability to correlate and predict both VLE and LLE in mixtures containing ILs or salts with satisfactory accuracy. In addition, the ability of a commercial process simulator (Aspen Plus), to model phase equilibrium for the ternary systems of (HOAc + H20 + IL/salt) was examined. The physico-chemical properties of the investigated ionic liquids were characterized as a function of temperature.

The main aim of this project was to investigate the photochemical degradation pathways of lignin models using singlet oxygen and other photo-induced reactive species, in order to understand the photochemical transformations of the lignin polymer and other lignin-like polymers. The sensitized photolytic oxidation of lignin models containing the 13-0-4' lignin substructures using visible light, Rose Bengal and oxygen was studied in an attempt to understand and develop photocatalytic oxidation as a method for the conversion of lignin into added-value chemicals, Initial studies using a simple model dimer and attempting to replicate a published method[1] resulted in significant differences in the products when compared with the previous literature studies. A time study was carried out and a possible mechanism of a photo catalysed dimerization has been proposed. The observed radical coupling reaction has been shown to precede the eventual cleavage of a key benzylic ether bond in the tetramer and the formation of a quinone product and guaiacol by-product. Similar radical couplings were also observed for 13-5' dimer and trimer lignin models, Identification of the coupling products was obtained by spectroscopic characterization and corroborated by independent synthesis. Batch and flow reactors were tested and compared for the photolysis reactions. The flow reactor was proved to be more efficient than the batch reactor in terms of time-space conversion and yield. It was also shown that the flow reaction is a good method for the study of mechanism and optimization of the conditions required for the process, The dimerization process was then used for the preparation of three novel unsymmetrical coupling products. Successful cross-coupling of lignin models in this way provides a flexible new synthetic strategy for the preparation of more complex lignin models which is competitive with previous synthetic routes.

Heterogeneous catalysis is widely used in industry for the synthesis of chemicals. However, achieving a high selectivity to the desired products can be a challenge. Numerous factors influence the selectivity of a reaction, including the solvent used. The effect of solvent on the hydrogenation of the aromatic ketone over a Pt/Titania catalyst was, therefore, investigated, The solvent was found to have a major effect on the rate and the selectivity of the reaction. This effect was found not to be due to empirical or physical properties of the solvent. Alkane solvents gave fast reactions which favoured ring hydrogenation, aromatics gave slower reactions which favoured carbonyl hydrogenation and alcohols favoured carbonyl hydrogenation. The rate in alcohol solvents depended on whether the solvent was a primary alcohol or secondary alcohol, with secondary alcohols giving much faster reactions, In addition, water had a major effect on the rate and selectivity of alcohol solvents. The aromatic solvents were found to be site blocking the active sites, The alcohols form a layer on the catalyst surface, which in the case of the primary alcohol solvents prevents the substrate from reaching the active sites. Reactions were performed over Pt/silica sintered Pt/titania and Pt supported on anatase and rutile. The reaction was found to be structure sensitive and oxygen vacancies were found to play a role in determining the selectivity of the reaction. The selective hydrogenation of a number of compounds over OMS-2 and catalysts based on OMS-2 was investigated. It was found the OMS-2 is an active hydrogenation catalyst, even without an added metal, though the reactions were usually slower. Chloronitrobenzene was not dehalogenated by OMS-2. Due to the results obtained over this catalyst, the mechanism of nitrobenzene hydrogenation was investigated. It was found that two mechanisms occlllTed, which depended on the catalyst and conditions used.

This thesis presents investigations on the use of various iron and aluminium oxides, and oxyhydroxides based sorbents for the removal of arsenic from groundwater via adsorption processes. Three main types of materials were employed: (i) a natural ore and an industrial by-product; (ii) organised mesoporous silicas (OMS) coated with iron and aluminium, and: (iii) metal oxyhydroxides produced from industrial coagulants solutions (FAS(OH)s). The synthetized materials were optimised with respect to adsorption capacity and all the sorbents were fully characterised. The OMS were coated with various ratios of Fe and AI oxides with a view to tailoring the As(III)/As(V) selectivity of the adsorbents. The effects of pH, arsenic speciation and concentration. and adsorbent dosage on the adsorption of arsenic were investigated in a series of batch experiments as well as the different adsorption mechanisms. A kinetic investigation was undertaken with the effect of particle size on the adsorption process and the diffusion of the As species within the solid matrix of the absorbents were investigated. The most promising materials with regard to adsorption capacity were then employed in small scale columns, for evaluation of performance in a continuous process. Several aspects from these investigations were considered and discussed with regard to the potential use of the materials in full-scale fixed bed adsorption units. First the effect of common dissolved ions on the adsorption efficiency of the materials was studied and a reconstituted groundwater was used for comparison purposes. The regeneration of saturated adsorbents using various chemicals was investigated. In a further study, the metal oxyhydroxide powder adsorbent was agglomerated into a granular material and used in subsequent adsorption experiments. Finally, a full scale adsorption unit was designed employing the optimal adsorbent material, which may result in a 50 % smaller footprint unit when compared to existing technologies.

No description available.

Aspects of the mass transport processes occurring in the ion-exchange membranes, PUDO 193, a Cellophane membrane derived from regenerated cellulose and Permion 2291 40/30, a grafted co-polymer of polyethylene and methacrylic acid, were studied while the membranes were swollen in solutions of KOH of a wide range of concentrations. Measurement of the dimensional changes (length, width and thickness) of as received Cellophane films, after immersion in solutions of KOH, revealed a complex swelling behaviour with the majority of swelling resulting in changes in thickness. Unlike Cellophane, and as a consequence of their different structure, the swelling behaviour of Permion films were found to be less complex. The swelling behaviour was used to determine the porosity of the swollen membranes. The ion-exchange capacity of the mono-functional Permion was obtained by pH titration, a method unsuitable for use with Cellophane since it is not fully exchanged at low external electrolyte concentrations. The ion-exchange properties of Cellophane were determined using atomic absorption techniques and a crion tracer method which was deemed suitable since similar results were obtained for Permion by this method and by pH titration. Transport numbers of potassium ions and transference numbers of water through Cellophane and Permion as single membrane types were obtained using a meticulous technique, which minimised the unwanted effects of diffusion and osmosis. The method obtained transport numbers relevant to a specific concentration by holding solution composition constant and equal on either side of the membrane. The confidence gained in the technique, enhanced by careful cell testing and the application of correction factors, provided a sound basis for the measurement and subsequent understanding of transport behaviour in the less obvious situation, namely in assemblies of membranes. Measurements of the resistance of Cellophane and Permion ftlms equilibrated in solutions of KOH were made. Membrane resistance vs. membrane thickness plots were curved due to current refraction into the region where the membrane was clamped between the two halves of the conductivity cell. The data was linearised using a nonempirical correction factor and hence the accuracy of the measured membrane conductivity was improved. From the primary resistance data, electrolyte conductivity and the mobilities of the potassium and hydroxyl ions in free solution were calculated. The ratio of potassium to hydroxyl ion mobility in free solution formed a basis for a comparison with a similar mobility ratio in the membrane phase. This method allowed a comparison of mobilities in free solution and the membrane phase without the necessity of estimating a suitable tortuosity factor. Models of tortuosity were then introduced to assess the blocking characteristics of the two membranes. The transport properties of assemblies of Cellophane and Perm ion were investigated. Transport numbers entering and leaving the assembly were found to be different and depended on the orientation of the assembly. For the situation where transport numbers were greater leaving the assembly and at low current densities a steady state was reached and the depletion of electrolyte at the interface was replaced by diffusion, osmosis and hydraulic flow. At high current densities depletion of electrolyte at the interface was rapid causing the decomposition of the Cellophane. For the situation where transport numbers were greater entering the assembly, the assembly separated at the Permion/Cellophane interface due to the accumulation of electrolyte, the difference between measured and predicted transport numbers was accounted for by the effects of diffusion and osmosis which occurred mainly in the Cellophane.

The electrochemical reduction of uranium (IV) oxide to metallic uranium has been studied in lithium chloride-potassium chloride eutectic at 450°C using electrochemical and advanced material characterisation techniques. Electrochemical characterisation identified a single reduction peak occurring at -2.57V with respect to the Ag|Ag+ reference electrode. Sweep voltammetry has identified that the electroreduction of uranium dioxide to metallic uranium occurs via a single, 4-electron transfer, process. The electrochemical reduction has also been observed to be dependent on the activity of O2- ions: An increase in the bulk activity of the oxygen anion impeded the electroreduction process. This phenomena was thermodynamically predicted using Littlewood diagrams produced for the system. In addition, in situ energy dispersive X-ray diffraction investigations were carried out on the I12 JEEP beamline at the Diamond Light Source which resulted in the direct observation of the formation of uranium metal when a uranium dioxide electrode was exposed to electroreduction potentials. No intermediate phases were observed which supports the electrochemical characterisation of this process occurring in a single step. Moreover, microstructural characterisation has been performed on micro-bucket electrodes and metallic cavity electrodes. A coral-like structure was identified after reduction of uranium dioxide and has been attributed to the volume change associated with the reduction. Microstructural reconstructions were performed on four separate sub-volumes in the direction of propagation of the electroreduction process. The porosity was seen to decrease significantly from 16% to 4%. The pore connectivity was also observed to decrease from 93% to 18%. This drastic change in porosity and pore connectivity is reflected in the pore tortuosity which is seen to increase to infinity. This microstructural evaluation is concluded to impede the diffusion of O2- ions out of the electrode resulting in an increased probability of impediment of the electrochemical reduction process.