Acrolein is an indispensable chemical intermediate with a rising demand in recent years. The concern of the increase of propylene prices due to the shrinking supply of nonrenewable crude oil makes the acid-catalyzed gas-phase glycerol dehydration to acrolein a prime candidate for research. Our analysis showed that the sustainable acrolein production from glycerol was both technically and economically viable. Alumina2700® (Al) and Silica1252® (Si) loaded with silicotungstic acid (HSiW) possessed distinct features while provided equally good acrolein yield (73.86mol% and 74.05mol%, respectively) optimally. Due to the unique non-equilibrium characteristics, non-thermal plasma (NTP) could promote a variety of chemical reactions; however, its application in a dehydration process remained blank. This study used the reaction of glycerol dehydration to acrolein to probe whether NTP could 1) improve acrolein yield during dehydration, 2) suppress the coke formation and regenerate the catalyst, and 3) modify the properties of the catalyst. The dielectric barrier discharge configuration was used to generate NTP; various NTP field strengths and also their interaction with temperature and the catalyst were investigated. The results showed that NTP improved the glycerol conversion and that NTP with a proper field strength increased acrolein selectivity. The optimal acrolein yields of 83.6 mol% and 83.1 mol% were achieved with 3.78 kV/cm NTP and 4.58 kV/cm NTP at 275°C for HSiW-Al and HSiW-Si, respectively. The application of NTP-O2 (5% oxygen in argon, 4.58 kV/cm) during glycerol dehydration significantly suppressed coke formation on HSiW-Si. NTP-O2 could regenerate the deactivated HSiW-Si at low temperatures by removing both soft and hard coke at various rates. NTP-O2 with higher field strength, at medium operation temperature (150ºC) and in argon atmosphere was more effective for coke removal/catalyst regeneration. Applying NTP to the catalyst fabrication showed some capabilities in modifying catalyst properties, including enlarging surface area, preserving mesopores, increasing acid strength and Brønsted acidity. NTP with argon as the discharge gas performed better in these modifications than NTP with air as the discharge gas.

Summary: A process is under investigation for the manufacture of dicalcium phosphate by the hydrolosis of concentrated superphosphate containing recycled monocalcium phosphate. The hydrolysis also results in the formation of an aqueous solution of monocalcium phosphate and free phosphoric acid. The phases are separated, followed by washing and drying of the solid dicalcium phosphate. The wash water is used in the hydrolyzer. The solution is returned to the superphosphate production step, where phosphate rock and additional phosphoric acid are added, and where water is evaporated to form the solid superphosphate. Pilot plant results have indicated that filtration rates vary widely under almost identical mixing conditions, presumably due to variations in particle size ranges. It was thought worthwhile, therefore, to study the effects of different mixing variables on the relative particle sizes as indicated by the settling rates of the mixture.

Polystyrene (PS) is an important commodity polymer. In its most commonly used form, PS is a high molecular weight linear polymer, typically produced through free-radical polymerization, which is a well understood and robust process. This process produces a high molecular weight, clear thermoplastic that is hard, rigid and has good thermal and melt flow properties for use in moldings, extrusions and films. However, polystyrene produced through the free radical process has a very broad molecular weight distribution, which can lead to poor performance in some applications. To this end, nitroxide-mediated radical polymerization (NMRP) can synthesize materials with a much more consistently defined molecular architecture as well as relatively low polydispersity than other methods. NMRP involves radical polymerization in the presence of a nitroxide mediator. This mediator is usually of the form of a stable radical which can bind to and disable the growing polymer chain. This will “tie up” some of the free radicals forming a dynamic equilibrium between active and dormant species, through a reversible coupling process. NMRP can be conducted through one of two different processes: (1) The bimolecular process, which can be initiated with a conventional peroxide initiator (i.e. BPO) but in the presence of a stable nitroxide radical (i.e. TEMPO), which is a stable radical that can reversibly bind with the growing polymer radical chain, and (2) The unimolecular process, where nitroxyl ether is introduced to the system, which then degrades to create both the initiator and mediator radicals. Based on previous research in the group, which included experimental investigations with both unimolecular and bimolecular NMRP under various conditions, it was possible to build on an earlier model and come up with an improved detailed mechanistic model. Additionally, it was seen that certain parameters in the model had little impact on the overall model performance, which suggested that their removal would be appropriate, also serving to reduce the complexity of the model. Comparisons of model predictions with experimental data both from within the group and the general literature were performed and trends verified. Further work was done on the development of an additionally reduced model, and on the testing of these different levels of model complexity with data. The aim of this analysis was to develop a model to capture the key process responses in a simple and easy to implement manner with comparable accuracy to the complete models. Due to its lower complexity, this substantially reduced model would me a much likelier candidate for use in on-line applications. Application of these different model levels to the model-based D-optimal design of experiments was then pursued, with results compared to those generated by a parallel Bayesian design project conducted within the group. Additional work was done using a different optimality criterion, targeted at reducing the amount of parameter correlation that may be seen in D-optimal designs. Finally, conclusions and recommendations for future work were made, including a detailed explanation of how a model similar to the ones described in this paper could be used in the optimal selection of sensors and design of experiments.

Boron carbide was produced on tungsten substrate in a dual impinging-jet CVD reactor from a gas mixture of BCl3, CH4, and H2. The experimental setup was designed to minimise the effect of mass transfer on reaction kinetics, which, together with the on-line analysis of the reactor effluent by FTIR, allowed a detailed kinetic investigation possible. The phase and morphology studies of the products were made by XPS, XRD,micro hardness and SEM methods. XPS analysis showed the existence of chemical states attributed to the boron carbide phase, together with the existence of oxy-boron carbide species. SEM pictures revealed the formation of 5-fold icosahedral boron carbide crystals up to 30 micron sizes for the samples produced at 1300oC. Microhardness tests showed change of boron carbide hardness with the temperature of tungsten substrate. The hardness values (Vickers Hardness) observed were between 3850 kg/mm2 and 4750 kg/mm2 corresponding to substrate temperatures of 1100 and 1300 C, respectively. The FTIR analysis of the reaction products proved the formation of reaction intermediate BHCl2, which is proposed to occur mainly in the gaseous boundary layer next to the substrate surface. The experimental parameters are the temperature of the substrate, and the molar fractions of methane and borontrichloride at the reactor inlet. The effects of those parameters on the reaction rates, conversions and selectivities were analysed and such analyses were used in mechanism determination studies. An Arrhenius type of a rate expression was obtained for rate of formation of boron carbide with an energy of activation 56.1 kjoule/mol and the exponents of methane and boron trichloride in the reaction rate expression were 0.64 and 0.34, respectively, implying complexity of reaction. In all of the experiments conducted, the rate of formation of boron carbide was less than that of dichloroborane. Among a large number of reaction mechanisms proposed only the ones considering the molecular adsorption of boron trichloride on the substrate surface and formation of dichloroborane in the gaseous phase gave reasonable fits to the experimental data. Multiple non-linear regression analysis was carried out to predict the deposition rate of boron carbide as well as formation rate of dichloroborane simultaneously.

Summary: A process is under investigation for the manufacture of dicalcium phosphate by the hydrolosis of concentrated superphosphate containing recycled monocalcium phosphate. The hydrolysis also results in the formation of an aqueous solution of monocalcium phosphate and free phosphoric acid. The phases are separated, followed by washing and drying of the solid dicalcium phosphate. The wash water is used in the hydrolyzer. The solution is returned to the superphosphate production step, where phosphate rock and additional phosphoric acid are added, and where water is evaporated to form the solid superphosphate.Pilot plant results have indicated that filtration rates vary widely under almost identical mixing conditions, presumably due to variations in particle size ranges. It was thought worthwhile, therefore, to study the effects of different mixing variables on the relative particle sizes as indicated by the settling rates of the mixture.

This work addresses fundamental aspects of designing templates and curing conditions for the synthesis of mesoporous metal oxide thin films. The first section addresses selection of cationic-carbohydrate surfactant mixtures to synthesize templated silica thin films for selective adsorption of simple carbohydrates based on molecular imprinting. Nuclear magnetic resonance and fluorescence spectroscopy results suggest a novel structure for mixtures of alkyl glucopyranosides or xylopyranosides with cationic (trimethylammonium) surfactants. Despite thermodynamically favorable mixing, the carbohydrate headgroups in the mixed micelle adopt an inverted configuration with their headgroups in the micelle core, and therefore are inaccessible for molecular imprinting. This orientation occurs even when the alkyl tail length of the carbohydrate surfactant is greater than that of the cationic surfactant, but this limitation can be overcome by introducing a triazole linker to the carbohydrate surfactant. The next section addresses the effects of aging conditions on the structural and chemical evolution of surfactant templated silica thin films. The third section describes the synthesis of carbohydrate/cationic surfactant imprinted silica thin films with orthogonally oriented cylindrical pores by modifying the glass surface with a random copolymer. The last part of the dissertation addresses the effect of pore orientation on the transformation mechanism of block copolymer templated titania thin films during high temperature curing. Mesoporous titania thin films can be used for photochemical and solar cell applications, but doing so requires addressing the tradeoff between loss of mesostructural order and growth of crystallinity during thermal treatment. By using advanced x-ray scattering techniques it has been shown that the titania films with vertically oriented pores can better withstand the anisotropic stress that develops during thermal treatment compare to titania films with mixed pore orientation. For instance, films with parallel or mixed pores can only be heated at 400 °C for a brief time (~10 min) without loss of order, while orthogonally oriented films can be heated at 550 °C or greater for extended time periods (on the order of hours) without significant loss of long-range mesopore structure. Detailed kinetic modeling was applied to enable the comparison of activation energy for mesostructure loss in films as a function of pore orientation and thickness.

An improved steady-state method combining experiment and mathematical modelling has been developed to characterize the scalable convective heat transfer coefficient, hvol [W*m^(-3)*K^(-1)], of uncoated and catalyst-support coated aluminium foam monoliths. The values of hvol were recovered by parameter fitting its model values to experimental temperature data for steady-state air-cooled monoliths under a known heating flux. The model was built with experimentally recovered values of the monolith’s thermal conductivity and fluid permeability along with known values for other physical parameters. The volumetric heat transfer coefficients of 10, 20 and 40 pore-per-inch uncoated aluminium foams were determined to range between 2,700 and 20,000 W*m^(-3)*K^(-1) at channel Reynolds numbers between 85 and 1,700. The presence of a 76 micron thick anodized layer of catalyst support on monolith foams effected a small but significant reduction in the value of hvol. Coating with an anodized layer also reduced the permeabilities of the monoliths to air flow by 4-20%. Knowledge of the scalable parameter, hvol, was used to model a steady-state non-isothermal, non-isobaric heat-coupled methanol reformer. The model shows that changes to the convective transfer coefficient due to coating the monolith with catalyst support may have significant consequences for the thermal profile of the model reactor and for the product yield. / Thesis (Master, Chemical Engineering) -- Queen's University, 2011-12-12 20:11:18.046

In this work we study mixtures of cationic surfactant (CTAB) and sugar based surfactant(s) (octyl beta-D-glucopyranoside (C8G1), dodecyl maltoside (C12G2) and octyl beta-D-xylopyranoside (C8X1)) to understand the non-ideal thermodynamic behavior of the mixtures of cationic and non-ionic surfactants in water and synthesis of imprinted materials. The thermodynamics of micellization, mixing and dilution of these systems are studied using Isothermal Titration Calorimetry (ITC) and the experimental data obtained are modeled with a pseudo-phase separation model with non-ideal mixing described by regular solution theory. It is shown that a model accounting for enthalpy of demicellization and enthalpy of dilution based on McMillan-Mayer model is able to fit ITC data set for CTAB-C8G1 system with varying mole fractions. In addition to measuring non-ideal mixing behavior, mixtures of cationic and saccharide-based surfactants are of interest for the molecular imprinting of oxide materials. Mixtures of CTAB and either C8G1 or C8X1 are utilized to prepare nonporous adsorbent materials which act as selective adsorbents towards the headgroup of the saccharide surfactant. The approach is based on the Stöber silica particle synthesis process in which surfactants are added to soft particles present at the onset of turbidity to imprint their surface. This approach is shown to yield particles displaying selective adsorption for sugars with different number of carbons, but also provide enantioselective adsorption of targeted saccharides. Enantioselectivity of D-glucose, D-xylose and D-maltose is demonstrated by imprinting with C8G1, C8X1 and C12G2, respectively. The imprinting technique provides the first example of selective adsorption based on non-covalent imprinting of silica for sugars. The mixed surfactant are also used to synthesize templated porous materials incorporating titanium which are used for epoxidation catalysis. The porous materials obtained have high surface area, uniform pore sizes in the mesopore range, and provided high selectivity and activity towards epoxidation of styrene. Titanosilicate thin films are also synthesized using cationic and saccharide surfactant mixtures to understand the incorporation of the titanium into the porous material. It is demonstrated that large amounts of isolated, tetracoordinated titanium sites can be incorporated into mesoporous silica-based materials via the complexation of the titanium precursor with a saccharide-based surfactant.

Membrane process including microfiltration (MF), ultrafiltration (UF), nanofiltration (NF) and reverse osmosis (RO) have provided numerous successful applications ranging from drinking water purification, wastewater treatment, to material recovery. The addition of functional moiety in the membranes pores allows such membranes to be used in challenging areas including tunable separations, toxic metal capture, and catalysis. In this work, polyvinylidene fluoride (PVDF) MF membrane was functionalized with temperature responsive (poly(N-isopropylacrylamide), PNIPAAm) and pH responsive (polyacrylic acid, PAA) polymers. It’s revealed that the permeation of various molecules (water, salt and dextran) through the membrane can be thermally or pH controlled. The introduction of PAA as a polyelectrolyte offers an excellent platform for the immobilization of metal nanoparticles (NPs) applied for degradation of toxic chlorinated organics with significantly increased longevity and stability. The advantage of using temperature and pH responsive polymers/hydrogels also includes the high reactivity and effectiveness in dechlorination. Further advancement on the PVDF functionalization involved the alkaline treatment to create partially defluorinated membrane (Def-PVDF) with conjugated double bounds allowing for the covalent attachment of different polymers. The PAA-Def-PVDF membrane shows pH responsive behavior on both the hydraulic permeability and solute retention. The sponge-like PVDF (SPVDF) membranes by phase inversion were developed through casting PVDF solution on polyester backing. The SPVDF membrane was demonstrated to have 4 times more surface area than commercial PVDF MF membrane, allowing for enhanced nanoparticles loading for chloro-organics degradation. The advanced functionalization method and process were also validated to be able to be scaled-up through the evaluation of full-scale functionalized membrane provided by Ultura Inc. California, USA. Nanofiltration (NF) between UF and RO presents selectivity controlled by both steric and electrostatic repulsions, which are widely used to reject charged species, particularly multivalent ions. In this work, selective permeation of CaCl2 and high sucrose retention are obtained through the modification of nanofiltration membranes with lower charge compared to commercial nanofiltration membrane. The membrane module also shows high stability with constant water permeability in a long-term (two months) test. Extended Nernst-Planck equation were further used to evaluate the experimental results and it fits well.

The cost of deconstructing cellulose into soluble sugars is a key impediment to the commercial production of lignocellulosic biofuels. The use of the quartz crystal microbalance (QCM) to investigate reaction variables critical to enzymatic cellulose hydrolysis is investigated here, extending previous studies of fungal cellulase activity for the first time to whole cell cellulases. Specifically, the activity of the cellulases of Clostridium thermocellum, which are in the form of cellulosomes, was investigated. To clearly differentiate the activity of free cellulosome and cell-bound cellulosome, the distribution of free cellulosome and cell-bound cellulosome in crude cell broth at different growth stages of C. thermocellum (ATCC 27405) was quantified. Throughout growth, greater than 70% of the cellulosome in the crude cell broth was unattached to the cell. The frequency response of the QCM was shown to capture adsorption and hydrolysis of amorphous cellulose films by the whole-cell cellulases. Further, both crude cell broth and free cellulosomes were found to have similar inhibition pattern (within 0 - 10 g/L cellobiose). Thus, kinetic models developed for the cell-free cellulosomes, which allow for more accurate interfacial adsorption analysis by QCM than their cell-attached counterparts, may provide insight into hydrolysis events in both systems.