Thesis (MScIng)--University of Stellenbosch, 2007. / Bibliography. Also available via the Internet.

Inaug.-Diss.--Georg-Auguste-Universität zu Göttingen. / Includes bibliographical references.

Call number: LD2668 .T4 1962 Y85

Thesis (Ph. D.)--University of Washington, 2003. / Vita. Includes bibliographical references (leaves 120-129).

Bibliography: pages 150-156. / The catalytic oligomerization of propene to liquid fuels using synthetic mica montmorillonite (SMM) as well as the effect of incorporating nickel into the lattice and nickel, cobalt and zinc into the interlayer spaces was investigated. NiSMM is more active for propene oligomerization than SMM, although the product selectivity (60% of the oligomers boiled at above 453 K) is similar. The increase in activity of NiSMM is attributed to an increase in the surface acidity of the catalyst. The maximum activity over the nickel exchanged catalyst occurs at a nickel loading of 0.057 wt %. It is proposed that the bond strength of the acidic hydroxyl groups are perturbed by the polarizing effect of the divalent cation (Co, Zn or Ni) present in the interlayer spaces of SMM. The reduction of nickel, ion exchanged into SMM, removes the induction period associated with SMM and increases the catalyst lifetime. However, reduction of the lattice nickel results in a decrease in catalyst lifetime although the Bronsted acidity has increased. It is proposed that the metallic nickel present in reduced NiSMM may promote dehydrogenation of high molecular weight hydrocarbons thus causing rapid deactivation of the catalyst by increasing the formation of "graphitic" coke. The lifetime of NiSMM is greatly reduced by using a wet propene feed and reacting at higher temperatures (443 K) due to the generation of Bronsted sites and increased coke formation rates, respectively. Deactivation of the catalyst is associated with a "graphitic" coke build up. The RON of the petrol fraction is 94.5 and the hydrogenated diesel fraction has a cetane number less than 35.

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.

Thesis (MSc)--Stellenbosch University, 2001. / ENGLISH ABSTRACT: This study concerns the copolymerization of propylene with l-heptene. The percentage of l-heptene used as co-monomer in the polymerization reactions was varied from 5% to 20% in order to compare a variety of polymers with different percentages of comonomer incorporated. A variety of different catalysts were used for these polymerizations. Two metallocene catalysts were used: (A) the isospecific catalyst, rae- [ethylene bis(l-indenyl)]zirconium dichloride (rac-Et(Ind)2ZrCh2) and (B) the silylene-bridged catalyst, rac-Me2Si(2-MeBenz[ e]Ind)zZrCh2. Methylaluminoxane (MAO) was used as cocatalyst for these two metallocene catalysts. Another series of polymerization reactions was done using a Ziegler-Natta catalyst, namely TiCb/AlEt3/Si02. Characterization of the copolymers included usmg high temperature gel permeation chromatography (HTGPC) for molecular mass and molecular mass distributions, differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA) to investigate the thermal and mechanical properties of the copolymers, nuclear magnetic resonance spectroscopy (NMR) for information concerning the microstructures of the copolymers and crystallization analysis fractionation (CRYSTAF) to investigate the short chain branching of the copolymers. Comparative studies were done on the different catalysts and the polymer properties. The synthesized polymers were also compared with copolymers of propylene with l-hexene and l-octene. / AFRIKAANSE OPSOMMING: Hierdie studie behels die kopolimerisasie van propileen met I-hepteen. Die persentasie van I-hepteen wat as komonomeer in die polimerisasie-reaksies gebruik is, is van 5% tot 20% gevarieer. 'n Verskeidenheid van verskillende kataliste is gebruik vir hierdie polimerisasies. Twee metalloseenkataliste is gebruik: (A) die isospesifieke katalis, rae- [etileen bis(l-indeniel)]zirconium dichloried (rac-Et(lnd)2ZrCh2) en (B) die silileengebrugde katalis, rac-Me2Si(2-MeBenz[e]Ind)2ZrCh2. Metielaluminoksaan (MAO) is as ko-katalis gebruik saam met bogenoemde twee metalloseenkataliste. 'n Ander reeks polimerisasie reaksies is gedoen waarin 'n Ziegler-Natta katalis gebruik is as aktiverende katalis, naamlik TiCi)/ AlEt3/Si02. Die karakterisering van die kopolimere sluit in: hoë temperatuur gel deurlatings chromatrografie (HTGPC) vir molekulêre massa en molekulêre massa verspreidings, differensiële skandering kalorimetrie (DSC) en dinamiese meganiese analisering (DMA) om sodoende die termiese en meganiese eienskappe van die polimere te ondersoek, kern magnetiese resonans spektroskopie (KMR) vir inligting in verband met die mikrostrukture van die kopolimere en kristallisasie analise fraksioneringstegniek (CRYSTAF) om die kort-kettingvertakkings van die kopolimere te ondersoek. Vergelykende studies IS op die verskillende katalisatore en die polimeereienskappe gedoen. Die gesintetiseerde polimere is ook met kopolimere van propileen met I-hekseen en l-okteen vergelyk.

No description available.

Bibliography: pages 129-132. / A synthesis techniQue was developed for the preparation of a nickel oxide sil ica alumina catalyst. The propene oligomerisation activity and the selectivity of the catalysts prepared by homogeneous decomposition deposition (HDD) were investigated and compared with nickel oxide silica alumina catalysts prepared by the techniQues of impregnation (IMP) and co-precipitation (SG). Amongst others. the effect of the nickel content. reacti6n temperature and pressure, and water content of the feed, on the activity and selectivity. were investigated. Also investigated were the lifetime of the various catalysts and, in the case of HDD type catalysts. the ability to oligomerise high molecular weight hydrocarbons (Cb). Nickel oxide silica alumina prepared by the HDD method is more active for the propene oligomerisation than catalysts prepared by the IMP and SG methods. The product spectrum in the case of IMP and HDD type catalysts are similar, with a propene dimer (Cb) being the main product. In the case of SG type catalysts. however. a shift to heavier products was observed, i.e., propene dimer (Cb) and trimer (Cq) were formed in eQual Quantities. It is proposed that the increase in activity of HDD type catalysts was due to a large extent of metal dispersion and distribution and a stronger interaction between the metal and the support. It is also proposed that the metal is readily accessible to the reactant molecules. The activity and selectivity of catalysts prepared by the HDD method were independent of the nickel content. This was not the case for IMP and SG type catalysts. both of which showed decreasing activity with increasing nickel content when the nickel content was increased beyond 5 wt%. The lifetimes of the various catalysts were also examined. From the results obtained. over the first 10 h. the lifetime of HOD type catalysts was superior to that of the other catalysts studied. The activity and selectivity of the various catalysts were sensitive to the reaction conditions. Thus moving into the vapour phase. by either increasing the temperature at a fixed pressure or decreasing the pressure at a fixed temperature. was in each case acCompanied by a shift to heavier products and a decrease in activity.