Co(NO)(NO₂)₂L₂ complexes (L = PPh₃, PMePh₂, PMe₂Ph, PMe₃, PEt₃, PEt₂Ph, PEtPh₂, PPrPh₂, PBu₃ and 1/2DPPPr) were prepared from the reactions of Co(NO)X₂L₂ (X = Cl, Br) with sodium nitrite in methanol freshly distilled from magnesium methoxide. The complexes were characterized by elemental analysis, 15-N labeling, infrared and NMR spectroscopy. The crystal structure of Co(NO)(NO₂)₂(PMePh₂)₂ was determined by X-ray diffraction. The cobalt atom has tetragonal pyramidal geometry. The nitrosyl group in the axial position is strongly bent. The NO₂ ligands have two different ligating geometries: one is bound to cobalt through the nitrogen atom and the other is bidentate forming an asymmetric four membered ring. The phosphine ligands are equivalent and trans to each other. Multinuclear NMR spectroscopy (¹H, ³¹P, ¹⁵N and ¹⁴N) was used to determine the solution structure of Co(NO)(NO₂ )₂L₂ complexes, to study mono and bisnitrosyls of cobalt, to establish some correlations between NMR parameters and structural characteristics of these complexes and to follow their reactions in solution. Reactions of Co(NO)(NO₂)₂L₂ with CO, NO and RCOX were observed to produce Co(NO)₂XL complexes. Since the structure may be indicative of electronic requirements at the metal center as well as the reactivity of the compounds, The crystal structures of Co(NO)₂Cl(PPh₃) and Co(NO)₂(ONO)(PPh₃) were also determined. In these complexes the cobalt atoms have pseudotetrahedral geometry. The CoNO angles are in the range considered to be linear. They are geniculated in an "atracto" conformation. Co(NO)(NO₂)₂L₂ and Co(NO)₂(ONO)L complexes react with oxygen in the solid state or in solution to form Co(NO₃)₂(OL)₂ complexes. When the reactions with O₂ were carried out in the presence of an excess of olefins, the formation of nitrates is inhibited Co(NO₂)₂(OL)₂ and olefin oxides are formed instead. The crystal structures of Co(NO₃)₂(OPMePh₂)₂ and Co(NO₂)₂(OPMePh₂)₂ were determined by X-ray diffraction. In these complexes, the NO₃ and NO₂ groups are bidentate. They are arranged in a cis configuration around the cobalt atom.

Bibliography: pages 136-140. / This thesis set out to investigate the activity of various supported cobalt catalysts for high pressure propene oligomerization. This work was carried out as part of a larger research effort to upgrade light olefins to liquid fuels in the distillate range. The supports investigated included activated carbon, alumina, silica alumina, synthetic mica montmorillonite, zeolite Y and NH₄⁺-ZSM-5. A cobaltmolybdenum hydrodesulphurization catalyst was also tested. The synthesis procedures used in this work included double ammoniation (Co-C), incipient wetness impregnation (Co-C, alumina, NH₄⁺-ZSM-5), ion-exchange (NaY, NH₄⁺-ZSM-5), chemisorption (cobalt complex on activated carbon) and homogeneous deposition-precipitation (Co-Silica alumina).

No description available.

Fischer-Tropsch (FT) synthesis is a reaction which entails the conversion of synthesis gas, also known as syngas (a mixture of H2 and CO gases), to liquid hydrocarbon fuels, oxygenated hydrocarbons, chemicals and water. This syngas mixture is obtained from natural gas, coal, petroleum, biomass or even from organic wastes. In this study cobalt catalysts supported on novel carbon spheretitania (CS-TiO2) composite materials were synthesized and tested for their performance in the FT process. Initially carbon spheres (d = 80-120 nm) were prepared in a vertical swirled floating chemical vapour deposition reactor without the use of a catalyst. The rate of production was controlled and the highest production rate of about 195 mg/min was obtained at an acetylene (C2H2) flow rate of 545 mL/min at 1000 °C. The produced carbon spheres (CSs) had a narrow size distribution with a uniform diameter size. Purification and functionalisation of the CSs improved the total surface area, due to the removal of PAHs which blocked the CS pores. The introduction of functional groups to the CSs was achieved and these changed the wetting properties of the CSs. Functionalising the CSs for longer than 17 h in HNO3 destroyed the morphology of the CSs. After successful preparation of functionalised CSs, the interactions between CSs and TiO2 were studied by in the TiO2 composite using two different sol-gel methods, namely the conventional sol-gel and the surfactant wrapping sol-gel method. The surfactant wrapping sol-gel method entailed the modification of the CSs by dispersing them in a surfactant, in this case hexadecyltrimethylammonium bromide or CTAB [(CH3(CH2)15N(CH3)3Br]. This introduced alkyl “tails” which eased the dispersability of the CSs before coating them with Ti[O(CH2)3CH3]4 (a source of TiO2) to produce a homogeneously coated CS-TiO2 composite material (defined as ASW3). It should be mentioned that many, many experiments were performed to develop an efficient and reliable method to make homogeneously coated CS-TiO2 composites since it was found to be very difficult to achieve an interaction between carbonaceous materials and TiO2 especially by sol-gel procedures. The traditional sol-gel method was used to prepare CS-TiO2 composites with different ratios viz. 1CS-1SG, 1CS-2.5SG, 1CS-5SG, 1CS-10SG, 1CS-25SG and 1CS-50SG. These composites showed weak interactions between CSs and TiO2 even at high TiO2 loading ratio. Interestingly the surface area of these composites showed high values of 80 and 85 m2/g for 1CS-5SG and 1CS-10SG, respectively. At lower TiO2 ratios the measured surface area was similar to that of CSs, i.e 10 m2/g for 1CS-1TiO2. At high TiO2 ratios the measured surface area was similar to that of TiO2, i.e 49 m2/g for 1CS-50TiO2. The TEM images of CS-TiO2 (ASW3) composites prepared by surfactant wrapping methods showed a successful TiO2 coating of CSs. The TiO2 grain size was 8.0 nm with both anatase and rutile phases. High surface areas (up to 98 m2/g) of composite materials were achieved by employing this procedure. The high surface areas achieved suggest that the interaction between CSs and TiO2 was homogeneous and the increase was due to the “bridge” formed between CSs and TiO2. A series of cobalt catalysts (10% by weight) supported on these materials was carried out by the deposition precipitation method using Co(NO3)2·6H2O as the metal precursor. After appropriate drying and calcination the catalysts were characterized using traditional characterisation techniques and tested in the FT reaction using a fixed bed reactor. The the 10%Co/CS catalyst produced a CO conversion of 15.2% while the catalyst had a low total BET surface area (6 m2/g) compared to non-carbonaceous catalysts with higher BET surface areas. This observation suggests that the surface area did not necessarily play a role in the CO conversion, but that other properties (reducibility and dispersion) of CSs influenced the catalyst activity. After coating CSs with TiO2 and loading cobalt to produce 10%Co/ASW3 both the BET surface area of the catalyst and the CO conversion increased to 83 m2/g and 20.1%, respectively. CO-TPD of 10%Co/ASW3 showed a large amount of strongly adsorbed CO. This increased CO was due to the interaction between CSs and TiO2 which developed CO adsorptive sites.

The effect of the addition of ethanol (2% and 6%) during the Fischer-Tröpsch (FT) synthesis has been investigated using a 10%Co/TiO2 catalyst in a stirred basket reactor (T = 220°C, P = 8 bar, H2/CO = 2). The transformation of ethanol vapour (2% and 6% in nitrogen) over the Co/TiO2 catalyst was also studied in the absence of the synthesis gas under FT reaction conditions. Ethanol was observed to be incorporated in the growing chain and was found to (i) increase the selectivity to light products, (ii) increase the olefin to paraffin ratio and (iii) significantly decrease the catalyst activity. These effects were almost completely reversed when the ethanol in the feed was removed. Thermodynamic predictions, TPR and XRD analysis have shown that cobalt metal particles were oxidised to CoO by ethanol but that re-reduction to Co metal was possible when ethanol was removed from the feed stream allowing the catalyst to recover most of its initial performance, in particular when high flow rates were used. The effect of the cobalt carboxylate chain length (C2, C5 and C9) used in the preparation of alumina supported cobalt catalysts has been studied by TPR, XRD and hydrogen chemisorption techniques. The activity and selectivity of the prepared catalysts have been evaluated for the Fischer-Tröpsch (FT) reaction in a stirred basket reactor. It is shown that for catalysts with Co content of 10 wt.% the activity increases as the carboxylate chain length increases while the selectivity towards methane and light hydrocarbons decreases with the carboxylate chain length. The catalyst prepared using cobalt acetate was found to present the highest metal-support interaction and the poorest performance for the Fischer-Tröpsch reaction. When the metal content was increased to 15 wt.% Co and 20 wt.% Co respectively, the metal-support interaction for the catalyst prepared from cobalt acetate significantly decreased making it a better catalyst for the FT reaction compared to the catalysts prepared from C5 and C9 cobalt carboxylates. The effect of the addition of Au to a Co FT catalyst supported on titania, alumina and silica respectively, has been investigated by varying the amount of Au (0.2 to 5 wt.%) added to the catalyst. The catalysts were characterized by atomic absorption spectroscopy, XRD, XPS and TPR analysis. The catalyst evaluation for the Fischer- Tröpsch reaction activity and selectivity was achieved in a fixed bed micro-reactor (H2:CO = 2; 20 bar; 220°C). Addition of Au to supported Co catalysts improved the catalyst reduction and the cobalt dispersion on the catalyst surface. The catalyst activity for the FT reaction and the methane and light product selectivity increased with Au loading in the catalyst.

Polystyrene bis(salicylaldehyde)-propylene-1,3-diiminato Cobalt (II) (salen) and Polystyrene bis(acetylacetone)-propylene-1,3-diiminato Cobalt (II) (BAE) were prepared stepwise from polystyrl chloride. The reaction series included substitution of the chloride with a malononitrile carbanion, reduction to a diamine, condensation to form a Schiff base, and complexation with Co(II) acetate to form the active polymeric material. Optimum conditions with regard to time, temperature, reaction ratios, and solvent were determined for each reaction. The ability of the polymer bound cobalt complex to oxidize 3-methyl indole was measure. The BAE catalyst yielded a large amount of the corresponding o-formylaminoacetophenone. However, the exact yield is not known because product could not be separated from the indole. The salen catalyst showed starting material with a small indication of product.

Dissertation (Ph.D.)--Auburn University, 2004. / Abstract. Includes bibliographic references (269-292).

M.Sc. / 2-(Pyrazol-1-ylmethyl)pyridine ligands were synthesised by phase transfer alkylation of 2-picolyl hydrochloride with the appropriate pyrazole. These ligands were subsequently reacted with NiCl2, NiBr2, FeCl2 or CoCl2 to form the respective complexes. The substituents on the pyrazole included phenyl and tert-butyl groups as well as electron withdrawing CF3 groups. The substituents played an important role in the steric and electrophilic nature of the metals. A second ligand design is 2,6-bis(pyrazol-1-ylmethyl)pyridine and were prepared by phase transfer alkylation of 2,6-bis(chloromethyl)pyridine with two mole equivalents of the appropriate pyrazole. These ligands were reacted with NiCl2, NiBr2, FeCl2 or CoCl2 to form the respective complexes. A third ligand design is 2-(chloromethyl)- or 2-(bromomethyl)-6-(pyrazol-1-ylmethyl)pyridine and were prepared by the selective alkylation of 2,6-bis(chloromethyl)pyridine with one mole equivalent of the appropriate pyrazole. These ligands were also reacted with NiCl2, NiBr2, FeCl2 or CoCl2 to form the respective complexes. Characterisation of all compounds was done by a range of spectroscopic techniques as well as X-ray crystallography and elemental analysis. The data showed good fit to the proposed structures and in a few cases were confirmed by X-Ray crystallography. All complexes were tested as catalysts for ethylene and higher olefin oligomerisation and showed good activity. The production of alkenes were confirmed in toluene and hexane, however, due to the use of EtAlCl2 and toluene the oligomers were alkylated to form the Friedel-Crafts alkylation products. Similar alkylation was observed for the higher olefin reactions. In comparison, the same reactions in hexane resulted in only C4, C6 and C8 oligomers. When higher olefin reactions were also conducted in hexane, polymeric solids were observed.

Neste trabalho foram preparados e caracterizados catalisadores de cobalto suportados em y-Al2O3, CeO2, 20%CeO2-yAl2O3 e em soluções sólidas CexZr1-xO2 (0<= x<=1), pelo método de impregnação, com o objetivo de avaliar o desempenho destes frente à reforma a vapor e oxidativa do etanol. Na preparação dos catalisadores utilizou-se o teor de 20% em massa de cobalto, para os suportes y-Al2O3, CeO2 e 20%CeO2-y-Al2O3, e 10% para os suportes CexZr1-xO2. Para a caracterização dos sólidos, as técnicas utilizadas foram: Espectroscopia Dispersiva de Raios-X (EDX), Redução a Temperatura Programada com H2 (RTP-H2), Difração de Raios-X pelo método do pó (DRX), Adsorção de Nitrogênio pelo método B.E.T. e Espectroscopia na região do Ultravioleta e do Visível. As reações de reforma a vapor de etanol foram realizadas nas temperaturas de 400, 500 e 600oC com razões molares H2O/Etanol= 3/1 e 4/1. Já, os ensaios catalíticos de reforma oxidativa foram realizados a 500oC com razões molares H2O/Etanol/O2= 3/1/0,16 e 3/1/0,20. Através dos resultados de DRX e RTP-H2 verificou-se a formação da fase Co3O4 para todos os catalisadores. Para os catalisadores suportados em y-Al2O3 e 20%CeO2-y Al2O3 observou-se ainda a formação da fase CoO-Al2O3. Nos ensaios catalíticos de reforma a vapor do etanol foi verificado que as mais altas conversões do etanol em produtos e maiores seletividades a hidrogênio foram obtidas a 600oC e razão H2O/Etanol=3/1. A maior razão CO2/CO foi obtida a 500oC com o catalisador Co/Ce0,4Zr0,6O2. Observou-se também que a adição de oxigênio ocasionou uma diminuição na deposição de carbono. / Cobalt supported in yAl2O3, CeO2, 20%CeO2-yAl2O3 and CexZr1-xO2 (0<= x <= 1) solid solution, were prepared by impregnation and applied in steam and oxidative reforming of ethanol. In the preparation of the catalysts was used 20wt.% of cobalt with yAl2O3, CeO2 and 20%CeO2-yAl2O3 supports and 10wt.% with CexZr1-xO2 supports. The solids were characterized by X-Ray Dispersive Spectroscopy; Temperature Programmed of Reduction with H2 (TPR- H2); X-Ray Diffraction (XRD); Nitrogen Adsorption by B.E.T. method; Ultraviolet and Visible Spectroscopy. The ethanol steam reforming was carried out at 400, 500 and 600oC with molar rates H2O/Ethanol= 3/1 and 4/1. The ethanol oxidative reforming was carried out at 500 °C with molar rates H2O/Ethanol/O2 = 3/1/0.16 e 3/1/0.20. XRD and TPR-H2 results showed the formation of Co3O4 phase for all catalysts. For the catalysts supported in y-Al2O3 and 20%CeO2-y-Al2O3 was still observed the formation of the CoO-Al2O3 phase. In the ethanol steam reforming the higher conversion was obtained at 600°C and the best H2 selectivity was observed with the H2O/Etanol=3/1 molar ratio. The higher CO2/CO ratio was observed at 500oC with Co/Ce0,4Zr0,6O2 catalyst. Already, the addition of oxygen caused a decrease in the carbon deposition.

Thesis (M.S.)--Mississippi State University. Department of Chemical Engineering. / Title from title screen. Includes bibliographical references.