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Research and applications of multivariate statistical process monitoring and fault diagnostic techniques for performance monitoring of continuous and batch processes continue to be a very active area of research. Investigations into new statistical and mathematical methods and there applicability to chemical process modelling and performance monitoring is ongoing. Successive researchers have proposed new techniques and models to address the identified limitations and shortcomings of previously applied linear statistical methods such as principal component analysis and partial least squares. This thesis contributes to this volume of research and investigation into alternative approaches and their suitability for continuous and batch process applications. In particular, the thesis proposes a modified canonical variate analysis state space model based monitoring scheme and compares the proposed scheme with several existing statistical process monitoring approaches using a common benchmark simulator – Tennessee Eastman benchmark process. A hybrid data driven and mechanistic model based process monitoring approach is also investigated. The proposed hybrid scheme gives more specific considerations to the implementation and application of the technique for dynamic systems with existing control structures. A nonmechanistic hybrid approach involving the combination of nonlinear and linear data based statistical models to create a pseudo time-variant model for monitoring of large complex plants is also proposed. The hybrid schemes are shown to provide distinct advantages in terms of improved fault detection and reliability. The demonstration of the hybrid schemes were carried out on two separate simulated processes: a CSTR with recycle through a heat exchanger and a CHEMCAD simulated distillation column. Finally, a batch process monitoring schemed based on a proposed implementation of interval partial least squares (IPLS) technique is demonstrated using a benchmark simulated fed-batch penicillin production process. The IPLS strategy employs data unfolding methods and a proposed algorithm for segmentation of the batch duration into optimal intervals to give a unique implementation of a Multiway-IPLS model. Application results show that the proposed method gives better model prediction and monitoring performance than the conventional IPLS approach.

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The aim of this work was to investigate the applicability of using supercritical (sc) hydrofluorocarbons (HFCs) as alternative solvents for hydrogenation and polymer modification processes. Solubility studies in binary and ternary systems have been carried out using both dielectrometry and gravimetric techniques and results show that a range of unsaturated carboxylic acids (crotonic acid, 6-methoxy-1-tetralone, methylsuccinic acid, alpha-acetamido-cinnamic acid and itaconic acid) have a high degree of solubility in 1,1,1,2-tetrafluoroethane (HFC 134a). The solubility results were modelled successfully using the Peng-Robinson equation of state (PR EOS) and this model was used to devise a separation methodology for itaconic acid and methylsuccinic acid. It is suggested that HFC 134a can be used as both the reaction medium and the extracting solvent, which enables in-line separation of compounds during sc synthesis.;The homogeneous asymmetric hydrogenation of a range of unsaturated substrates (itaconic acid, dimethyl itaconate, alpha-acetamido-cinnamic acid and trans-2-methyl-2-penetenoic acid) has been studied using a rhodium/MonoPhos catalytic system. High yields and enantiomeric excesses (ee's) have been observed and this, coupled with the separation technique, provides an effective method of asymmetric reduction, which greatly enhances the commercial applicability of this technology.;The infusion of difluoromethane (HFC 32) into polystyrene (PS) and polyethylene (PE) has been characterised and the results have been compared to those obtained for carbon dioxide. Significant plasticization was observed in the polymeric materials and it was shown that manipulation of the experimental temperature, pressure and depressurisation rate could cause significant changes in the morphology of the samples.;It is concluded that sc HFCs are promising alternatives to conventional organic solvents and are useful for a variety of processes. These media have accessible critical constants, relatively high dielectric constant values and are able to facilitate the dissolution of polar solutes and rhodium based catalysts without the need for co-solvents or fluorinated ponytails. Furthermore, the investigation suggests that reactions carried out in the sc regime can allow facile reagent/product separation and it is logical to assume that a similar methodology can be applied to catalyst recovery.

Process intensification is in principle a strategy of making dramatic reductions in the capital cost of a production system, improving intrinsic safety, reducing environmental impact and energy consumption. An electrochemical cell is a specific example of a multiphase system that should be capable of being operated very intensively within a centrifugal acceleration field. This thesis presents the first systematical research work in this field. It demonstrates that many electrochemical processes can be enhanced considerably by using a high-acceleration field, which takes full advantage of the improvement in catalytic activity and optimal electrode structure. Six electrochemical processes have been investigated. Namely, the electro-reduction of oxygen, electro-oxidations of hydrogen and methanol, chlorine evolution, water electrolysis, and methanol fuel cell reaction. Several catalysed electrodes including Ti mesh or carbon cloth were prepared and used for the above processes. A number of catalyst deposition routes were explored for the preparation of the technical electrodes, including Pt, Ag, Pt-Ru and RuO₂ electrodes. The action of a centrifugal field is two fold: first, it acts as an mass transfer promotor; second, it accelerates gas bubble disengagement For chlorine evolution, water electrolysis, and methanol oxidation, centrifugal fields play a very significant role in and lead to significant reductions in polarisation and mass transport resistance. The high acceleration fields reduce the cell resistance drastically through effectively disengaging gas bubbles from the electrode surface. It also overcomes mass transport limitations in these systems through generation of powerful interphase buoyancy force. The processes were therefore greatly intensified in centrifugal fields and approached a maximum efficiency. Increase in the operating temperature and the concentration also benefit the processes. Interestingly, both effects were intensified in centrifugal fields, i.e., the current density increases more rapidly in centrifugal fields than in stationary cell at a constant potential corresponding to the same increment in temperature and concentration. For the gas consuming systems, e.g., oxygen reduction and hydrogen oxidation, centrifugal fields also produce positive results. The degree of intensification for these systems was limited to a relatively low level. Centrifugal fields have little benefit for methanol fuel cell operation. The results were disappointing and unexpected. It was realised that the cathode process, an oxygen gas consuming reaction, is difficult to be intensified by using centrifugal means due to the type of electrode used at the cathode, although the anode process was intensified in centrifugal fields. A model for a centrifugal cell with gas evolving electrodes was proposed and tested. In the model the cell voltage and cell voltage reduction are obtained from the hydrodynamic electrochemical, and electrochemical engineering theories.

A study has been carried out into the reactions of ethanol over transition metal dehydrogenation catalysts, with particular emphasis on the reaction of ethanol to ethyl ethanoate. The reaction is of commercial interest, and the test work has been aimed at the development of a process that would yield ethyl ethanoate at commercially acceptable purity. Copper based catalysts have been shown to selectively promote the formation of ethyl ethanoate. Experimental work has been carried out to identify an optimised catalyst and reaction conditions for the ethanol to ethyl ethanoate reaction. A copper based catalyst that yields >95% selectivity to ethyl ethanoate, at >40% conversion of ethanol, has been identified. A purification scheme has been devised that incorporates selective hydrogenation using either nickel or ruthenium heterogeneous catalysts to remove aldehyde and ketone by-products. The purification scheme includes a novel distillation section. The catalyst system developed can be used to synthesise ethyl ethanoate at a purity of >99.98% from industrially available ethanol that contains up to 5% 2-propanol. A commercial plant producing 50,000 tonnes of ethyl ethanoate per annum, using the technology described in this thesis, has been in operation since April 2001.Four patents, based on the technology described in this thesis, have been applied for or granted.

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