A dissertation submitted to the Faculty of Engineering and the Built Environment, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Master of Science in Engineering, 2016 / The sulfur removal methods from petroleum products have become an important research topic. Sulfur poisons the catalysts found in vehicles engines and it is also a major air pollutant (Nehlsen, 2005). Recent sulfur specifications require refineries to produce ultra-clean products (Ma et al., 2002). This work aims at exploring a batch adsorptive desulfurization technique using a polymer-supported imidation agent (PI) as an adsorbent. The test was carried out at atmospheric pressure and on two commercial diesel fuels with sulfur contents of 5200 (Case 1) and 670 (Case 2) mg/kg which resembles the feed and outlet streams from the hydrodesulfurization (HDS) reactor respectively. The adsorbent was synthesized according to the procedure described by Shiraishi et al. (2003), BET, FTIR, SEM equipped with EDS and TGA were used for charaterization of the adsorbent. The PI was successfully synthesized and its surface area was 0.5333 m2/g which was incredibly lower than that of the PI synthesized by Fadhel (2010). Hence carbon nanotubes (CNTs) were added to the solution with the aim of improving the sulfur removal efficiency of PI. The obtained results indicated that PI with CNTs yield better results than PI without CNTs. In overall, the lowest sulfur content of 3462 mg/kg (33% removal efficiency) and 26 mg/kg (96% removal efficiency) for Case 1 and Case 2 respectively were obtained. Furthermore, the adsorbents were most effective at lower mixing rates (150 – 400 rpm), longer contact time (30 – 40 hours), practically high adsorbent amount (1 g) and moderate lower temperatures (25 – 50 ºC). The Freundlich adsorption isotherm model was the best fit to the experimental data in both Case 1 and Case 2. The kinetic model that best fitted well the experimental data is the pseudo-second-order model for both Case 1 and Case 2. The kinetic rate constant for Case 2 (4.079 x 10-3g/mg.min) was greater than that for Case 1 (6.75 x 10-5g/mg.min) thus indicating that fuel with low sulfur content has a higher sorption uptake than fuel with high sulfur content. Based on the results obtained in this study, it is suggested that the adsorption of sulfur at high sulfur content fuel is not capable to be used as a complimentary method to the HDS process. On the other hand, at low sulfur content fuel, there is an opportunity for combining this method with the traditional HDS method to achieve ultra-clean fuel. / GR2016

Researchers use metal-thiophene complexes to mimic reactions which occur inside hydrodesulfurization (HDS) reactors. Information obtained from these model studies may often be applied to understanding the mechanisms involved with commercially used catalysts. Certain mechanisms¹ for HDS propose thiophene ring cleavage,forming a metallacycle, prior to hydrogenation of one double bond. There are, however, limited examples of complexes derived from C-S cleavage.^2,3,4 Thermal reactions of the iridium complex, [Ir(COD)(PMe₃₎₃]Cl (COD=1,5- cyclooctadiene), with thiophene, thiazole, 4-methyl thiazole and 5-methyl thiazole yields the C-S addition metallacycles (Me₃P)₃Ir-(CH=CHCH=S)CI (I), \ (Me3P)3Ir-(CH=NCH=CHS)CI (II), (Me3P)3Ir-CCH=NC(CH3)=CHS)CI (III) and (Me3P)3Ir (CH=NCH=C(CH3)S)CI (IV), respectively. These compounds were characterized using the following methods: ¹H NMR, ¹³C NMR, ³¹P NMR, elemental analysis and single crystal x-ray diffraction. Following C-S addition to [Ir(COD)(PMe3)3]CI, nitrogen present in the thiazoles exhibit enhanced nucleophilicity. For exmnple, compounds II-IV react with methylene chloride to form dimers: CH2[NCR=CR'SIr(Cl)(PMe3)3CH]2. The above compounds are soluble in water and react with PF6 salts liberating the chloride atom from the Ir center. pKb measurements were recorded as well. This thesis describes the synthesis and examination of con1pounds I-IV as they may model the HDS process. Compounds II-IV represent the first examples of ring opened thiazole metallacycles with iridium. / Master of Science

M.Tech. (Department of Chemical Engineering, Faculty of Engineering and Technology), Vaal University of Technology. / This thesis presents a slight on desulphurization process of the commercial diesel fuel using the carbon-based metal oxide nanocomposites such as graphene oxide, ZnO, rGO as a nano-adsorbent, activated carbon (PAC and AC) and charcoal Granular active carbon (GAC) to produce a fuel of less than 10 ppm sulphur content. Due to the high percentage of sulphur compounds in the fuel causing air pollution, acid rain and other problems related to combustion process. The synthesised of sorbents were achieved using incipient impregnation, microwaved-assisted and chemical exfoliation methods. The materials were characterized using Thermogrametric Analyzer (TGA), Fourier transform infrared spectroscopy (FTIR) and X-ray diffractometer (XRD), Brunauer, Emmett and Teller (BET). The examination effect of operating conditions on the adsorption capacity with DBT and Sulphur compounds adsorption, the isotherms and the adsorption kinetic models were evaluated. The experimental data for PAC and AC were well suited to Freundlich isotherm and pseudo second-order kinetic models. The results shown that the sulphur feed concentration, the space velocity and the functional groups of the adsorbents have a considerable effect on the adsorption. In addition, it was observed that the temperature in the range of 30 to 80oC has a significant effect on the adsorption of Sulphur compounds from diesel fuel using 20 wt.% of sorbents. The rGO substrate which contained abundant oxygen functional groups was confirmed to promote the dispersion metal oxide and increased the adsorption efficiency of sulphur compounds (H2S and SO2) by providing oxygen ions weakly bound to the sulphur molecules. For the desulfurization process by adsorption, PAC and AC exhibited a better affinity for 80% removal of sulphur compared to the GAC and GO. The effects of metal species such as zinc oxide (ZnO) and reduced graphite oxide (rGO) composite on the adsorption capacity of hydrogen sulphide (H2S) were investigated. It was found that depending on the copper load, the adsorption capacity of H2S increased up to 20 times compared to pure ZnO. To study the oxidation changes on copper and zinc oxides, crystallite analysis by XRD and chemical state analysis by XPS were performed.