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Yes / Several new homemade nano-catalysts are prepared here to reduce sulfur compound found in light gas oil (LGO) utilizing the adsorption desulfurization technique. The effect of different support materials (Fe2O3, Cr2O3 and CdO) having the same particle size (20 nm) on the adsorptive desulfurization performance for loading 5% nickel sulfate (5 wt%NiO) as an active component for each catalyst, is studied. Oxidative desulfurization process (ODS) in a novel digital baffle batch reactor (DBBR) is used to evaluate the performance of the catalysts prepared. Moderate operating conditions are employed for the ODS process. The efficient new nano-catalysts with for the removal of sulfur are found to be 93.4%, 85.6% and 62.1% for NiO/Fe2O3, NiO/Cr2O3 and NiO/CdO, respectively at 175 deg C, 75 min and 2 ml of H2O2. The best kinetic model and the half-live period for the nano-catalysts related to the relevant reactions have also been investigated here.

Yes / A digital baffle batch reactor (DBBR) for oxidative desulfurization (ODS) reactions is designed and applied here in order to reduce the sulfur concentration presented in light gas oil (LGO) based on a novel homemade nano-catalyst (Copper Oxide (CuO)/Activated Carbon (AC)). With efficient impregnation, good pore size distribution, high activity and higher surface area, the designed nano-catalyst (CuO/AC) demonstrated excellent catalytic efficiency. To evaluate the effectiveness of nano catalyst (prepared experimentally), several experiments related to ODS reactions using the digital baffle batch reactor are carried out under moderate process conditions (reaction temperature (100, 120 and 140 °C), contact time (15, 30 and 45 min) and oxidant (H2O2) amount (2, 3 and 5 ml)). The experimental outcomes indicated that increasing the reaction temperature, batch time and oxidant amount lead to reduced sulfur concentration of oil feedstock leading to a greener fuel. The efficiency of sulfur conversion is reported to be 83.1 % using the modified nano-catalysts and new reactor (DBBR) at reaction temperature 140 oC, batch time 45 min and H2O2 amount of 5 ml. So, such new results using DBBR for ODS reactions based on CuO/AC as a new modified nano catalyst has not been reported in the public domain and it is considered as new results.

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

Sulfur dioxide emissions, which are produced through the combustion of coal, are thought to be a leading contributor to acid rain. A number of postcombustion techniques for the reduction of sulfur dioxide emissions are being tested; however, the reduction in the pyritic sulfur content of coal through physical cleaning methods may be the most economically viable alternative to the S02 problem. In this investigation, the microbubble column flotation process (MCF), developed at VPI&SU, was tested as a means of reducing the pyritic sulfur content of several high-sulfur coals targeted by the u.S. Department of Energy. A wide variety of pyrite rejection schemes were tested including the use of pyrite depressants, dispersants and elevated pH conditions. The overall efficiency of the MCF process was characterized using a technique known as "release analysis". This technique was used to provide the optimum grade versus recovery relationship for a given coal and a given set of reagent conditions. It was also used as a means for evaluating the various schemes for rejecting coal pyrite. The results of this work indicate that the MCF process is capable of producing a separation very close to that generated by release analysis. The release analysis technique was also found to be an effective means of characterizing pyrite liberation and pyrite rejection for a given coal. In general, it was found that liberation was the most important factor in the rejection of pyrite, although elevated pH conditions seemed to provide improvements for some coals. / Master of Science

A new fine-coal cleaning circuit, with potential near-term applications, has been evaluated for treating fine coal (i.e., 28 mesh x 0). This circuit combines a surface-based separator known as Microcel™ column flotation with an enhanced gravity separator known as the Multi-Gravity Separator (MGS). The synergistic effect of combining both processes in a single circuit resulted in improved ash and pyritic sulfur rejection with minimal losses in energy recovery. In addition, technical and economic analyses of this processing scheme suggest it compares favorably with existing post-combustion desulfurization techniques. A detailed study of the MGS included the development of a model based on fundamental principles of fluid mechanics and mineral processing. The theoretical analyses identified drum speed as the most important MGS operating parameter. To validate these findings, a detailed parametric test program was conducted using coal samples from the Pittsburgh No. 8 and Illinois No. 6 seams. A statistical analysis of the test data also showed that drum speed was the most important variable in controlling the performance of the MGS. The other controlling parameters, i.e., feed percent solids, feed rate and wash-water addition rate, were found to be of lesser importance. The experimental test results were found to be in good agreement with the theoretical predictions obtained using the model. / Ph. D.

D. Tech. Mechanical Engineering. / Investigates and/or rank the performance of locally available materials (i.e. limestone, dolomite, or calcrete) as sorbents in the capture of SO2 emissions from coal-fired power plants. Two experimental procedures were adopted in this work: the pH-stat method was used to simulate conditions encountered in wet flue gas desulphurisation (WFGD); and the fixed-bed reactor was used to simulate conditions encountered in the dry in-duct flue gas desulphurisation (DFGD) process. It is important to note that most studies of using calcium-based materials as sorbents for SO2 removal have been carried out in overseas countries. These studies were carried out using materials and research conditions prevailing in the particular countries. Furthermore, all South African coal-fired power stations burn low grade coal allowing the high grade coal to be exported. As a result, coal-fired power stations in South Africa emit higher emissions than the overseas power stations which are operated on high grade coals. Thus the results achieved internationally may not be directly translated to the South African conditions.