The objective of this work was the development of structured zeolite catalysts by growing of ZSM-5 and Y zeolites layers on the pre-treated FeCrAlloy wires, which could now offer technical advantage in catalytic application. The advantages of implementation of zeolitic coatings in industrial applications are that they have; lower pressure drop, high heat and mass transfer rates compared to standard pelleted or extruded catalysts. The key focus of this research was the generation of thin films of zeolite ZSM–5 and Y zeolite catalysts on the surface of a FeCrAlloy metal substrate. Using in-situ hydrothermal synthesis, the influence of the synthesis parameters such as substrate oxidation and crystallisation time on the zeolite crystallisation process in both the bulk phase (powder) and on the structured zeolite was studied and optimised. Then powder and structured Na-ZSM-5 and Na-Y were treated by calcination and ion exchange in post-synthesis treatment. Further post-synthesis modification was required in the zeolite Y case to improve the catalytic properties. The post synthetic modification of zeolite Y was carried out using acidified ammonium nitrate which was optimised to produce dealuminated zeolite Y with good crystallinity and a Si/Al = 8. Characterisation was performed after each stage of this work to optimise catalyst development using XRD, SEM, EDAX, BET, MAS-NMR, and TGA. Once the optimised zeolite Y and ZSM-5 structured catalysts prepared, cracking of n-heptane was carried out to assess the in catalytic performance compared with Y and ZSM-5 pellets in a fixed-bed reactor under the same operation conditions. The cracking of n–heptane over the pellets and structured catalysts for both ZSM–5 and Y zeolite showed very similar product selectivities for similar amounts of catalyst with apparent activation energy of around 60 kJ mol-1. This research demonstrates that structured catalysts can be manufactured with excellent zeolite adherence and when suitably activated/modified give comparable cracking results to the pelleted powder forms. These structured catalysts will improve temperature distribution in highly exothermic and endothermic catalysed processes.

Zeolites are crystalline aluminosilicates that are frequently used as catalysts to transform chemical feedstocks into more useful materials in a size- or shape-selective fashion; they are one of the earliest forms of nanotechnology. Zeolites can also be used, especially in the form of zeolite membranes (layers of zeolite on a support), to separate mixtures based on the size of the molecules. Recent advances have also created the possibility of using zeolites as alkaline catalysts, in addition to their traditional applications as acid catalysts and catalytic supports. Transport and catalysis in zeolites are greatly affected by physical and chemical defects. Such defects can be undesirable (in the case of zeolite membranes), or desirable (in the case of nitrogen-doped alkaline zeolites). Studying zeolites at the relevant length scales requires indirect experimental methods such as vapor adsorption or atomic-scale modeling such as electronic structure calculations. This dissertation explores both experimental and theoretical characterization of zeolites and zeolite membranes. Physical defects, important in membrane permeation, are studied using physical adsorption experiments and models of membrane transport. The results indicate that zeolite membranes can be modeled as a zeolite powder on top of a support—a “supported powder,” so to speak—for the purposes of adsorption. Mesoporosity that might be expected based on permeation and confocal microscopy measurements is not observed. Chemical defects—substitutions of nitrogen for oxygen—are studied using quantum mechanical models that predict spectroscopic properties. These models provide a method for simulating the 29Si NMR spectra of nitrogendefected zeolites. They also demonstrate that nitrogen substitutes into the zeolite framework (not just on the surface) under the proper reaction conditions. The results of these studies will be valuable to experimentalists and theorists alike in our efforts to understand the versatile and complicated materials that are zeolites.

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This work investigated the combined technology of adsorption on hydrophobic molecular sieves (zeolites) and direct UV (254 nm) photolysis for removing estrone (E1) from water. The target compound estrone belongs to the group of endocrine-disruptor compounds (EDCs) that are raising more and more concern due to increasing evidence of their adverse estrogenic effects on aquatic organisms and humans. Current wastewater treatment processes remove less than 80% of estrone on average. However, because of its strong biological potency, small amounts are still able to exert adverse estrogenic effects on aquatic systems. Consequently, advanced treatment technologies have been investigated in the hope of reaching higher removal efficiency. Adsorption of estrogens on hydrophobic zeolites in this work is a potential new alternative. Based on the hydrophobic nature of estrogens including E1, two types of zeolites, dealuminated Y (DAY) and silicalite-1, and a type of granular activated carbon Centaur® activated carbon (GAC) were evaluated for adsorption capacity. The results demonstrated that DAY is the best adsorbent for E1 in that 99% E1 can be removed by DAY. Silicalite-1 was the least effective. Moreover, adsorption of E1 to DAY is much faster. Estrone reached adsorption equilibrium in 4 hours on DAY versus 8 days for GAC. The adsorption data of DAY for E1 were fit to the Freundlich and Langmuir equations and the maximum adsorption capacity is estimated as 74 mg E1/g DAY. Direct UV photolysis of E1 in solution was also evaluated. Short-wave UV (ë = 254 nm) degraded E1 in solution much more effectively than long-wave UV-light (ë = 365 nm). No significant increase in degradation of E1 in UV photolysis was found with the addition of hydrogen peroxide. The regeneration of E1-contaminated DAY was investigated by a series of adsorption/direct UV (ë = 254nm) irradiation cycles. No significant deterioration of adsorption capacity of DAY was observed over nine adsorption/regeneration cycles.

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The production of zeolite membranes has developed over the last decade, and the membranes have been used extensively in pervaporation separation processes due to their resistance to chemical and thermal operating conditions. However, the conventional methods used in preparing anisotropic zeolite membranes, such as the secondary growth and in-situ crystallization methods, involve long and complex procedures that require the preparation of zeolite aluminosilicate gel prior to the fabrication process. Therefore, the aim of this study was to develop and test an easier, less expensive, and less time-consuming technique to fabricate different types of zeolite anisotropic membranes. Moreover, the fabrication of zeolite membranes using inexpensive kaolin raw materials taken straight out of the ground was taken into account and assessed. Within this framework, a novel technique of converting raw source alumina and silica, to a useful pure material of zeolite A was developed without any form of pre-treatment. Although this technique yielded a successful outcome in terms of the purity of the product, the later work conducted in fabricating membranes was focused on natural and commercial sources of zeolites rather than using the prepared products, to avoid the lengthy procedure. Anisotropic membranes of zeolite A, mordenite, and ZSM-5 were fabricated successfully using a simple, economical, and straight-forward technique. This technique made it possible to fabricate types of zeolite membranes that have been difficult to synthesise at the lab scale, where an anisotropic, clinoptilolite, thin membrane was fabricated for the first time in this study. All of the four membranes were subjected to different types of mixtures and provided promising results.

In this study commercial ultrastable Y zeolite was modified by different synthesis methods as precipitation, impregnation, and thermal hydrolysis, with different titanium and zirconium precursors. The intention was to investigate the effect of these metals in the framework on the zeolite acidity properties and how this influences the performance of the final catalyst on oil processes such as hydrocracking. For precipitation modification, different samples were synthesized varying the time precipitating ranging from one injection up to 9 hours. Samples in impregnation modification were synthesized along with thermal hydrolysis to compare different modification synthesis methods. Zeolite has a strong dealumination effect below pH 2 but low pH is needed to maintain titanium precursor in solution. Thermal hydrolysis shows an improvement in activity compared to precipitation and impregnation better selectivity compared to thermal hydrolysis. Metals preserve aluminum content when exposed to acidic post-treatment and shows improvements in yield of isomers compared to blanks. NH3-TPD showed decrease of weak and strong acid sites with increase of medium acid sites when exposed to acid post-treatment. BAS controls the yield of isomers.

No description available.

The efficacy of using zeolitic materials for the removal of nickel (II) and vanadium (IV) ions from solution has been evaluated in order to provide a method for the removal of the metal ions during hydroprocessing of crude oil. Batches of sodium based zeolites with a variety of pore sizes and Si/Al ratios were prepared using standard methods (high causticity solutions and templating agent). Characterisation of the products was carried out using powder X-ray diffraction, infrared spectroscopy, Raman spectroscopy and thermogravimetric analysis to confirm the presence of single zeolitic phases (zeolite A, zeolite X, zeolite Y, sodalite Na8 [AlSiO4]6Cl2 and hydrosodalite Na6 [AlSiO4]6. 6H2O). In a batch exchange process, divalent nickel and tetravalent vanadium ion solutions of concentration range 0.01M - 0.1M were placed in contact with the zeolite samples at 110°C for a period of 24h. Nickel (II) exchange was found to occur for all the zeolites at concentrations considered. Zeolite X was found to be most efficient at removing nickel from the solutions while zeolite Y was least efficient. Characterisation of zeolite X after ion exchange using powder X-ray diffraction and scanning electron microscopy showed that the structure of the zeolite had been maintained. Simplistic modelling of powder X-ray diffraction data have shown that the nickel ions are preferentially substituted on one of the four sodium sites. Vanadium (IV) exchange was also found to occur for all the zeolites at the concentrations considered. Zeolite A was found to be most efficient for the vanadium uptake. Characterisation with PXRD, FTIR and SEM-EDS however, shows that in addition to exchange at the zeolite s normal cation exchange sites, a significant amount of framework silicon species were also exchanged by the vanadium ions thus having a destructive effect on the zeolite framework leading to structural collapse. Ion exchange of the sodium-based zeolites with potassium and lithium showed that the uptake of nickel and vanadium of the zeolites significantly increased compared to the as- synthesised zeolites. Zeolite Y was surface-modified with the APTES ligand and showed a similar trend to that observed for alkali metal-zeolites; showing significantly greater nickel uptake at lower concentrations. Nickel-tetraphenylporphrin was synthesised as a mimic for the nickel-asphaltenes found in crude oil and an α-hydrogen donor solvent used to remove the nickel in the presence of zeolite ion exchangers. A similar trend was observed to that seen in aqueous solution, implying the process would be transferrable to a live medium. Analysis to determine the metal ions present in ashed Nigerian crude samples before and after solvent and/or complexing agent extraction was carried out using inductively coupled plasma mass spectroscopy (ICPMS) and energy fluorescence analysis by X-rays (XRF). The process showed varying amounts of nickel was extracted by the different media along with iron. For nickel, the extent of extraction in the order of increasing % extraction is H2O<H3PO4<EDTA<IPA. For iron the order of increasing % extraction was H2O=EDTA<H3PO4<CH3OH while zinc extraction was in the order H2O<H3PO4 <CH3OH=EDTA.