كلية العلوم
Permanent URI for this communityhttps://repository.neelain.edu.sd/handle/123456789/482
Browse
202 results
Search Results
Item VITAM B1; MODELS: SYNTHESIS AND CHARACTERIZATION OF LIGAND BRIDGED DICOBALOXIMES(ALNEELAIN UNIVERSITY, 2009) BAKHEIT M USTAFA MOHAMED SALIHItem structural &spectroscopic stuoies on antenna protein complexes sing atomic force &laser scanning microscop(ALNEELAIN UNIVERSITY, 2003) Elsiddiq Tawer Kafi AburassABSTRACT ln this work we studied mainly the structure and liunctionality of aggregated antenna molecules of photosynthetic purple bacteria. Our goal was to understand some of thc nicchtinism ul'solar Hltllilllflll cimvcisiuii in the hiulugical systciils. lllc iicccssity ol'l|tc work arises from the vital importance of the photosynthetic phenomena for lite on the earth to occur and continue, and the essential role which the antenna complexes play in this process. State-of the-art technology in the tield of microscopy was used for this goal. Atomic force and laser scanning microscopes were used as main tools in this work. Methods for crystallizing the LH2 protein complex were developed, and the ring structure olithis antenna complex was resolved to nano-metcr scale. lilectric conductivity ot' the Lll2 was studied with Scanning Tunneling Spectroscopy (STS). With One-Photon Excitation (OPE) technique the dipole strength of the energy transfer between adjacent Ll'l2’s in the inter-molecular spaces was postulated, and the kinetics ofthe energy was modeled in the intra-molecular spaces for the B850 group. A model suggesting the existence of a metastable state, and traps of excitations within the system is postulated. Two-l’l1oton Excitation (TPE) technique was successfully applied to chloroplasts. The 3D structure ofsingle intact chloroplast complexes was obtainable with good contrast. mItem Preparation and Characterization of Tungsten Based Catalysts and their Performance in Oxidative Desulfurization of Fuel Oil.(ALNEELAIN UNIVERSITY, 2009-05) Zaki Eldin Awad Elgeed Ali AbdallaBeijing University of Chemical Technology Doctoral Dissertation Abstract Deep desulfurization of transportation fuels has become an important research subject due to the increasingly stringent regulations and fiiel specifications in many countries for environmental protection purpose. In this respect, a lot of research work has been done to reduce the sulfiir contents in fuel to ppm level, but the problem persists. To attain this target we used Oxidative desulfurization (ODS) method, which is considered one of the promising techniques used for desulfurization, owing to its attractive features such as mild reaction temperature and pressure, lower cost of operation and environmentally fiiendly. Thus, for ultra deep desulfurization of oil a series of ttmgsten based catalysts was designed using different strategies. The aim was to prepare efficient catalysts by simple method and relatively inexpensive and find the most suitable reaction conditions for oxidative desulfurization. Therefore following this conception, firstly Na;WO4/Al;O; promoted with different concentrations of phosphates (to enhance its catalytic activity towards oxidation desulfurization) was prepared by impregnation method. Analytical characterization results (XRD, XPS, and FT-IR) revealed that tungstate and phosphate were uniformly dispersed in alumina matrix and its structural properties were preserved. The experimental data showed that phosphate promoted Na;WO4/A120; catalyst was highly active for ODS, it reduced the sulfur of model oil containing DBT with 500 ppm S to a level of less than 2 ppm (corresponding to 99.7% sulfur removal) at 90 °C, H20;/S molar ratio =5, using 200 mg of catalyst, 25 ml model oil and 1 ml of acetic acid as phase transfer within 2 h. The catalyst was also found to be reusable and the experimental results showed that no significant decrease in its activity occurred for five runs. Na;WO4Pl.5/A1103 was applied in oxidative desulfurization (ODS) of FCC diesel oil (with sulfur contents 4100 ppm) as well. The reaction was canied out at 80 °C, H20;/S molar ratio =20 using 500 mg of catalyst, 25 ml FCC diesel oil, 5 ml of glacial acetic acid as a phase transfer reagent and 5 h continuous stirring under reflux conditions, and the oxidized oil was extracted with Methanol and passed through (1 >< 25 cm) alumina colunm (10 g A1203). The results showed that the catalyst reduced the sulfiir contents of oil FCC diesel oil from 4100 ppm S to 320 ppm S (corresponding 92% sulfur removal). Beijing University of Chemical Technology Doctoral Dissertation Secondly, W/MCM-41 mesoporous catalyst with different tungsten amounts was prepared by wet impregnation method in acidic media. The catalyst was charactenzed by XRD, FT -IR, SEM, SEM/EDX, TEM, XPS and N; adsorption. The characterization results revealed that tungsten was introduced successfully into MCM-41 silica support without changing its morphology even at high loading contents. The catalytic oxidation activity of the synthesized materials was found to be significant and gradually increased with increasing W loading on MCM—4l support. This catalyst reduced the sulfur contents of model oil from 500 ppm S to 3.6 ppm S corresponding to 99.3% Sulfur removal at 80 °C, H202/S molar ratio =5, using 100 mg of catalyst, 25 ml model oil, and 0.15 ml of acetic acid as phase transfer within 1.5 h. The catalyst was also recycled and the results showed no significant decrease in catalyst activity for three runs. Polyoxometalates has been considered as efficient catalysts for oxidation and exhibit fast reversible multi-electron redox transfomiations under mild reaction conditions. So, in order to achieve the advantages of both: the mesoporous MCM-41 support and catalytic properties of monovacant lacunary Keggin-type Polyoxometalate encapsulated quaternary ammonium salt, MCM-41 supported (BU4N)4H3(PW1|O39) mesoporous material with different (Bu4N)4H3(PW"O39) loadings was prepared by impregnation method in ethanoilic acidic media under reflux conditions. The use of acidic media was to avoid the hydrolysis of Polyoxometalates, while the quatemary ammonium salt was anchored in catalyst structure to take advantage of its large lipophilic hydrocarbon part, which helped in hydrophobic distribution of the catalyst in oil, in favor of less mass transfer resistance and faster reaction rate, avoiding the use of extemal phase transfer reagent. Characterization results revealed that MCM-41 retained its mesoporous structure even at high (Bu4N)4H3(PW||O39) loadings. BET analysis showed that catalysts possessed high surface area (805 — 9l2 ml/g), and (Bu4N)4H3(PW11O39) was homogeneously dispersed on silica support and grafted on its surface through W—Si—O linkage. Wide angle XRD and “P CP—MAS NMR confinned the perpetuation of its lacunary Keggin unit during synthesis. The material was found to be more active for oxidative desulfurization of organosulfur compounds than NagWO4/PxAl;O; and W/MCM-41 catalysts and desulfurized almost 100% of DBT and thiophene under mild reaction conditions (60 °C, H202/S molar ratio = 4, 100 mg of catalyst, 25 ml model oil and 1 h). The catalyst was also reusable and its activity was not reduced even afler four Beijing University of Chemical Technology Doctoral Dissertation recycles runs. When the catalyst was applied for oxidative desulfurization of FCC diesel oil with 974 ppm S, a sulfur removal of 97.2% (27 ppm S) was achieved at 70 °C, H20;/S molar ratio = 20, using 200 mg of catalyst, 25 ml of FCC diesel oil and 3 h continuous stirring. The oxidized oil was separated by simple extraction with methanol. Finally, Polyoxometalates were attempted to incorporate into mesoporous silica framework by direct synthesis route using co-condensation sol-gel method in the presence of CTAB as surfactant. In this respect, novel Cetyltrimethylammonium encapsulated monovacant lacunary Keggin Polyoxometalates units (C19H4;N)4H3(PW,|O;w) incorporated SiO¢ with different (C|9H4;N)4H;(PW11O39) contents (6.3- 14.9%) was prepared and characterized by XRD, FT-IR, Raman scattering spectroscopy, “P CP-MAS NMR spectroscopy, XPS, XRF, N; adsorption/desorption, DSC and HRTEM. The characterization results revealed that (C19H4¢N)4H3(PW|1O39) was highly dispersed into silica matrix and its structure remained intact afier formation of the material. The material possessed high surface area (543-1009 ml/g), pore volume (0.40-1.19 cm’/g), and pore walls thickness (5.85-9.37 nm) with interconnected wonn-like mesostructure. Small angle XRD and N; adsorption/desorption results showed that the material retained its mesoporous structure for up to 14.9wt.% (C|9H4;N).4H3(PW"O39) loading, further increase in percentage resulted in the formation of disordered structure with abundant micropores. The resulting material (C191-l41N)4H;(PWnO;9)/SiO; was highly porous and showed high catalytic activity for oxidation desulfiuization of DBT and reduced its sulfur contents from 500 ppm S to 0.2 ppm (corresponding to 99.96% sulfur removal) at 60 °C, H202/S molar ratio = 4 using 100 mg of catalyst, 25 ml model oil and 1.5 h. So this thesis presents the development of tungsten based catalysts from conventional ‘alumina supported NalWO4 promoted with phosphate’ catalyst to the ‘mesoporous MCM-41 silica supported WO;, and(Bu4N)4H;;(PW"O3i;) catalysts and finally, ‘direct incorporation of (C19H4;N)4H3(PWnO;9) into mesoporous silica, in order to find the most suitable precursor and reaction conditions. Key Words: Tllngsten, catalyst, Mesoporous materials, Oxidative desulfizrization, Polyoxometalate, FCC Diesel oil. IIIItem THE ROLE OF H YDROX YL TERMINA TED POLYBUTADIENE IN SPECIAL POLYURETHANE FORMULATIONS A THESIS(ALNEELAIN UNIVERSITY, 2007-08) ELSHRIEF ELMISKI KHAMISABSTRACT Hydroxyl-terminated polybutadiene (HTPB) resins occupy a unique position among the commercially available polyols. This class of materials may be used to prepare polyurethane elastomers that are characterized by low temperature flexibility, hydrophobicity and hydrolytic stability. Due to the hydrocarbon nature of the polymer backbone, these elastomers also possess extremely low dielectric constant, dissipation factor, and low MVTR (moisture vapor transmission rate) properties. Depending on the hydroxyl functionality and backbone microstmcture, namely, the l,2-vinyl, 1,4-cis, or 1,4-trans distribution of each repeating unit, the HTPB- derived polyurethane elastomers can have a wide range of physical properties including glass transition temperature and viscosity. This thesis is concemed with the role of (HTPB) as a soft segment in the preparation of special polyurethane which can be utilized in composite binding system, based on the following materials: I Hydroxyl terminated poly butadiene as a pre polymer. 0 2,4 toluene diisocyanate as a curing agent. 0 dioctyl sebacate as a plasticizer. 0 Tris methyl azidrinyl phosphinoxide(MAPO) as a cross linker. the dynamic mechanical behavior was studied followed by morphological studies using, (Electron Scan Micrograph), by tracing the different behavior of results regarding the relation between sofi segment and hard segment, and the means of controlling the disorder played by the long chain and entangled soft segment. MAPO was used as a cross linker in this manner. Different parameters has been gathered for tailoring a binding system, based on (HTPB) pre polymer, which can fit for use in solid composite propellants. llItem synthesis of some2 bromo-3ary laimion5 acetoxy1.4 naphtoquinones as antibacterial agent(Al-Neelain University, 2009) suhyla mohmoud ali elzeberABSTRACT Two groups of - amino quinones ,2-bromo-3-aryl amino -5- acetoxy-1,4-naphthoquinones and compound 2-amino-1,4- naphthoquinones were synthesis in this work by coupling some amines through nucleophilic substitution of their free amnino groups at position-2 of quinone. The compound 2-bromo-5-acetoxy-1,4- naphthoquinones were refluxed with the different aromatic amines to produce compound 2-bromo-3-a1ylamino-5-acetoxy-1,4- naphthoquinones. Under the same condition compounds l,4- naphthoquinone was reacted with the some amines to give 2-ainino-l,4- naphthoquinones . Compounds 2-bromo-5-acetoxy-l,4-naphthoquinone and 1,4- napthtoquinone were prepared as the first step in this work. The structure of the target molecules were deducted on basis of their spectral data (UV,IR,NMR and MS). The targeted molecules were screened for their antibacterial potential and significant activity was observed for most of them .Item commissioning and optimizA TION OF ATOTAL Skin electon therapy tech nique usingahig hdose RATE ELECTRON FACILITY(AlNEElAN UNVERSLTY, 2007) YOUSIF ABD AHah Mohammed YousifItem Chemical and Physical Characteristics of oils of seeds of some Cmaferea Plants Growing in the Sudan . ( A comparative Study )(ALNEELAIN UNIVERSITY, 2004) Mahmoud Mohamed Ali MahmoudAbstract Seeds of four species of the family Cructfirea were analyzed for seed Crude protein, Crude fiber, total ash ,and oil contents using Petroleum ether (40-60C°) as the solvent for extraction .The physical and chemical characteristics such as : Acid value, Saponification value unsaponiable matter , Peroxide and iodine value, Colour, refractive index, relative viscosity ,and relative density of oils were determined . Phytochemical screening of oil samples, and Thin layer chromatography were used to detect the expected compounds in Cructfirea oil seeds.Triterpenoids , flovanoid aglycones ,and phenolic acids were detected in all species. Fatty acids and other compounds in the oils were determined by Gas chromatography /mass spectrometric analysis. 13-Docosenoic acid(Erucic acid)generally highly considered in cruciferous plants was 21.15% in ‘Emca sativus and 36.05% in Rapfianus satillu_s.Oih8r acids found in the four species were hexadecanoic,9-Octadecen0iC,0ctadecanoic, 8,11,14-eicosatrienoic,9,12,15-octadecatrienoic,1 1-eicosanoic, eicosenoic,docosonoic ,15-tetracosenoic ,tetrac0sanoic and the di iso — octyl ester of 1,2-benzene dicarboxylic acid . Data from the literature based on previous studies in oils from other countries showed some differences in composition and yield .These differences may be due to the variations in the climate ,soil and geographic location .Item HYDROGEOLOGY OF THE SOUTH KOSTI PROVINCE(AlNEElAN UNVERSLTY, 2002-12) Abdel Rhman Hassan Shiekh LdrisItem Evaluation of Rigle EL-fools Crude oils by studying Physical and chemical, specification extraction of paraffin Wax and the capability of manufacturing the base oils(Al-Neelain University, 2009) Haitham Kamal Awad Alijitfistract The studied crude oil sample was collected from the field and distillated atmospherically using the (minitop-combi) apparatus which. is a very advanced automatic equipment complying with the ASTMD 2892 (l5 theoretical plat column) to separate the light component from the crude oil. Then appropriates lube cuts was collected by vacuum distillation according to ASTMD523o using the same equipment. The predetermined temperature ranges of the collected cuts were analyzed and tested to determine their characteristics. As in the industry, all cuts were subjected to several processes either to eliminate some of the undesired components or to enhance some properties. The vacuum residue were subjected to deasphaltin process to remove all the asphalts from the cut. after that all cuts were dewaxed including the deasphalted oil using (methyl ethyl ketone) to enhance the cooled properties. Then carried out to all of the aromatics to improve the viscosity index and the quality of the produced base oil cuts (using Phenol). The study conclude that Rile EL- foola crude oil is quite suitable for the manufacturing of base oils and it has gave different types and grades oflube base oils. IllItem Analysis of Topological Structure of Artificially Porous Gum Arabic by Scanning Electron Microscope(SEM)(ALNEELAIN UNIVERSITY, 2007-10) Amna Adam HamidAbstract Artificial porosity in Gum Arabic has been formed after being blended with Potassium bromate by using chemical method. Structural characterization is carried out by scaning electron microscope (SEM) micrographs exhibited equal K Br distribution and poly dispersed porosity by the combination of SEM and image analysis techniques we are enabled to trace the features and topology of the produced porosity. From the results obtained we have found that, the porosity had show random growth and increases in size and density after thermal treatment. This increment can be attributed to the connectivity of pores.