Thesis (M. Sc. (Chemistry)) -- University of Limpopo, 2016 / In this study, the use of synthetic hierarchical MFI zeolites as supports for palladium hydrocracking catalysts was investigated. Hierarchical zeolites were synthesised through two different routes, viz., (i) the indirect and (ii) direct routes. In (i) pristine ZSM-5 zeolites with different SiO2/Al2O3 ratios (SARs) were synthesised hydrothermally using tetrapropylammonium bromide as structure-directing agent (SDA), followed by a brief desilication of its calcined form in 0.2 M NaOH solution at 65 °C for 0.5 h. Procedure (ii) involved prior synthesis of three polyquaternary ammonium surfactants (containing 2 - 4 ammonium centres), followed by their use as SDAs in the hydrothermal synthesis of hierarchical MFI zeolites. The resulting materials were characterised by XRD, FT-IR, SEM and N2 adsorption isotherms (including BET surface area measurements). Successful synthesis of different classes of the hierarchical MFI zeolites was confirmed by XRD patterns, while successful synthesis of polyquaternary ammonium surfactants was confirmed by both their 1H NMR spectra and their ability to direct the MFI structure. On the basis of IR, peak intensities in the OH region between 3500 and 3800 cm-1, the surfactant-templated zeolites were inferred to be more acidic than zeolites prepared through the desilication route. Significant changes in crystal morphology were observed upon desilication of ZSM-5(50), while the ZSM-5(77) and ZSM-5(100) retained their agglomerated morphology upon a similar treatment. The micrograph pristine of ZSM-5(50) showed a predominant morphology of large and small spheroids, together with some ill-defined cubic shapes. After desilication, the zeolite did not retain the original morphology entirely, showing hexagonal prismatic crystals with twinning occurring in other areas and large spheroids “hatching” to reveal their contents upon treatment. Desilicated zeolites exhibited improved textural properties (i.e., increased SBET, pore volumes and pore diameters) and minor structural readjustments compared to their pristine counterparts. Textural properties of surfactant-templated zeolites were superior to those of desilicated zeolites, and improved with increasing number of quaternary ammonium centres in the surfactant template. These materials were generally more crystalline than the conventional zeolites. Hydrocracking catalysts containing 0.9 wt.% Pd loading on different MFI supports were prepared by the incipient wetness impregnation method. The n- v hexadecane hydrocracking conditions used were typical of LTFT process (i.e., Temperature = 215 - 310 °C, WHSV = 1 h-1, Pressure = 20 bar, in addition to the H2 /n-C16 ratio of 10). The catalytic activity in all catalyst systems increased with increasing reactor temperature and displayed C4/C12 ratios ≠ 1, evidence of the occurrence of secondary cracking (i.e., a non-ideal hydrocracking behaviour). This was also supported by the shapes of their product distribution profiles, which showed dominant C3 - C7 n-paraffins. Co-feeding H2O with n-C16 into the reactor was found to be detrimental to n-C16 conversion, but promoted the selectivity to iso-paraffins in the product spectrum. Simultaneous introduction of CO and H2O aggravated secondary cracking. Amongst the pristine ZSM-5 zeolite-based catalysts, Pd/P-ZSM-5(77) showed the best catalytic performance. Upon desilication, the performance order changed to favour Pd/D-ZSM-5(50*). For the surfactant-templated supports, Pd/HSZ(N4) showed the most superior hydrocracking performance. Comparison of catalytic activities of the best performing catalyst systems derived from the conventional and surfactant-templated zeolites in the hydrocracking of n-hexadecane, follow the order Pd/D-ZSM-5(50*) > Pd/P-ZSM-5(77) > Pd/HSZ(N4). That is, the pristine and desilicated zeolite-based catalysts performed better than their surfactant-templated zeolite-based counterparts. Therefore, the post-synthesis generation of mesoporosity through desilicating ZSM-5 with a SAR of 50 has proven beneficial for the resulting catalyst system. One of the possible reasons for the relatively inferior hydrocracking performance of the Pd/HSZ(N4) catalyst may be the aluminium-richness of the support (SAR = 40) compared to the conventional ZSM-5-based supports. In summary, catalysts Pd/D-ZSM-5(50*), Pd/P-ZSM-5(77) and Pd/HSZ(N4) are promising for diesel-selective catalysis and need further refinements and exploration.

M. Tech. Chemical Engineering. / Evaluates the use of modified eccalite as an adsorbent for the efficient removal of vanadium from industrial wastewater. The specific objectives of the study are: i. To determine whether modification of eccalite with a surfactant such as (hexadecyltrimethylammonium bromide HDTMA-Br, CTAB) will gives an optimal performance in vanadium removal from industrial wastewater; ii. To conduct batch adsorption experiments for modified eccalite for the determination of equilibrium adsorption capacity, kinetics, and thermodynamic parameters; iii. To perform column/dynamic adsorption experiments for modified eccalite in order to determine the dynamic adsorption capacity and breakthrough profiles. iv. Fit the experimental data to existing mathematical model describing the sorption process of vanadium removal from wastewater.

M. Tech. Engineering: Chemical. / Focuses on the emerging application of clinoptilolite in removing aspirin and cephalexin from municipal wastewater streams. The mechanisms of sorbent-organic compounds interaction was studied in detail. Specifically, this research aims to achieve the following objectives: I. to investigate the sorption capacity of surfactant modified clinoptilolite on the removal of aspirin and cephalexin ; II. To relate sorbents performance to process variables with sorbent properties and water quality ; III. to compare the sorption capacity of surfactant modified clinoptilolite to commercial emerging adsorbents on the removal of aspirin and cephalexin from aqueous solution ; IV. to apply existing mathematical models to describe isotherms and kinetic data in order to extract design parameters.

M.Tech.Chemical Engineering. / The distillery wastewaters released from industries that use molasses as a major source of carbon in their fermentation processes pose serious threats to the water quality in several regions around the globe. Melanoidin is an antioxidant that results from the Malliard reaction found in fermentation and distillation processes. This study explores the removal of melanoidin from aqueous solution using natural clinoptilolite modified using cationic surfactant hexadecyltrimethyl ammonium bromide. The absorbent media was characterized using analyatical techniques such as BET, FTIR, SEM-EDS and XRD analysis. Given the relatively low cost of natural zeolite, it is possible to apply the sorbent in polishing distillery wastewater after a biological process. Since both natural zeolites and distillery waste streams are used in agriculture, a prudent way to dispose the spent media is to use it as fertilizer in farming.

M. Tech. Chemical Engineering. / Discusses the general objective of this research is to study the application of a combined advanced oxidation and adsorption process, with a view to developing a novel technique for the treatment of tea industry effluents prior to discharge into receiving water bodies. The specific objectives of the research are: a) To tailor natural zeolite physico-chemical properties in attempt to enhance its adsorptive performance ; b) To evaluate the decolourization efficiency of functionalized zeolite in tea industry effluent treatment. c) To evaluate the effect of the following operational parameters: pH, initial concentration,temperature and the sorbent mass, on the removal of colour in tea industry effluent. d) To apply adsorption and advanced oxidation independently and to combine the two into one process.

M. Tech. Mechanical engineering. / Acid deposition is caused by the emission of acidic gases, for example, nitrogen oxides and sulfur dioxide. Nitrogen oxide emissions can be controlled by the proper selection of equipment and operating conditions. Sulfur dioxide on the other hand, can be cleaned by means of procombustion, combustion or post-combustion techniques; the latter being the most effective. The objective of this study is to find suitable additives which will augment the reactivity of lime towards FGD (flue gas desulfurization), while at the same time being easily available at a low price. Zeolite based sorbents yielded the highest reactivity, and all additives, except iron waste, had pozzolanic materials as their main reactive compounds.