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Complex oxidation effects in polymer degradation

Description: The authors are working to understand why predictions of degradation behaviors and rates, based on accelerated thermal aging experiments, often fail to match with aging of polymers under service conditions. A main goal of these studies is to develop more reliable lifetime prediction methodologies.
Date: September 1, 1994
Creator: Clough, R. L.; Gillen, K. T. & Wise, J.
Partner: UNT Libraries Government Documents Department

The Gas-Phase Thermal Chemistry of Tetralin and Related Model Systems

Description: The thesis is divided into 5 papers: gas-phase thermal decomposition of tetralin; flash vacuum pyrolysis of 3-benzocycloheptenone and 1,3, 4,5-tetrahydro-2-benzothiepin-2,2-dioxide (model systems for gas-phase pyrolysis of tetralin); high-temperature gas-phase reactions of o-allylbenzyl radicals generated by flash vacuum pyrolysis of is(o-allylbenzyl) oxalate; flash vacuum pyrolysis of 1,4-diphenylbutane; and flash vacuum pyrolysis of o-allyltoluene, o-(3-butenyl)toluene and o-(pentenyl)toluene were also used.
Date: May 1, 1993
Creator: Malandra, James
Partner: UNT Libraries Government Documents Department

Charge distribution analysis of catalysts under simulated reaction conditions. Fourth quarterly technical progress report, July 1--September 30, 1993

Description: Only moderate progress was made in collecting data using the Charge Distribution Analysis (CDA) apparatus. Initial runs performed with the furnace built on a boron nitride (BN) support showed unacceptable limitations. A new furnace design was immediately begun; the new microfurnace gave rapid heating and cooling rates almost 4 times faster than the BN furnace. Baseline data runs with fused silica were made.
Date: December 31, 1993
Creator: Freund, F.
Partner: UNT Libraries Government Documents Department

Photoinduced charge separation in linked donor-chromophore-acceptor systems. Progress report, September 1, 1993--May 31, 1993

Description: Focus has been mainly on preparation and characterization of triply bridged dinuclear complexes containing a tris-2-2`- bipyridineruthenium chromophore and a second tris-bipyridine metal complex which is to serve as electron donor or acceptor, and of linked RuL{sub 3}-containing D-C-A complexes where D is a phenothiazine donor and A is a diquat type acceptor. (DLC)
Date: June 1, 1993
Creator: Elliott, C. M.
Partner: UNT Libraries Government Documents Department

Catalytic oxidation of secondary alcohols

Description: The dioxygen oxidation of alcohols over platinum catalysts has been known for a long time. While of potential importance in synthetic procedures, this process has never found extensive use except in carbohydrate oxidations. Some reasons for this is the fact that this reaction only appears to work well in an aqueous medium in the presence of rather large amounts of a Pt black catalyst. Results obtained here show that supported Pt catalysts can be used to promote this oxidation in organic solvents provided a small amount of water is added to the reaction medium. It was also estabilished that the reaction takes place on the more coordinately unsaturated corner atoms on the Pt surface.
Date: November 1, 1992
Creator: Augustine, R. L. & Doyle, L. K.
Partner: UNT Libraries Government Documents Department

Dynamic NMR studies of restricted arene rotation in the chromiu tricarbonyl thiophene and selenophene complexes

Description: This thesis contains the results of organometallic studies of thiophene and selenophene coordination in transition metal complexes. Chromium tricarbonyl complexes of thiophene, selenophene, and their alkyl-substituted derivatives were prepared and variable-temperature {sup 13}C NMR spectra of these complexes were recorded in dimethyl ether. Bandshape analyses of these spectra yielded activation parameters for restricted rotation of the thiophene and selenophene ligands in these complexes. Extended Hueckel molecular orbital calculations (EHMO) of the free thiophene and selenophene ligands and selected chromium tricarbonyl thiophene complexes were performed to better explain the activation barriers of these complexes. The structure of Cr(CO){sub 3}({eta}{sup 5}-2,5-dimethylthiophene) was established by a single crystal X-ray diffraction study.
Date: May 27, 1994
Creator: Sanger, M. J.
Partner: UNT Libraries Government Documents Department

Novel process for depolymerization of coal to C{sub 2}--C{sub 4} hydrocarbons. Progress report No. 13, September 1--November 30, 1992

Description: An envelope of parameter values has been experimentally identified in our laboratory, heretofore unexplored, for the catalytic depolymerization of coal which leads to yields of C{sub 2}-C{sub 4} hydrocarbons in excess of 50 weight percent of the coal, in a direct, single-stage process under mild conditions. The chemistry observed is fundamentally different from all coal conversion processes, both liquefaction and gasification, previously reported in the literature. The process-derived recycle liquid solvent will be characterized, and is expected to constitute a super-critical phase under conditions of temperature and pressure imposed by the chemistry of the system. Using a special reactor incorporating windows for visual observation, the operation of a catalyst bed fluidized by super-critical, coal-derived fluids will be examined. The capability of such a supercritical, coal-derived fluid to control agglomeration of a strongly caking coal, in the catalyst bed, will be evaluated, and satisfactory control developed. Solvent upgrading of the recycled liquids will be applied as may be required.
Date: December 1, 1992
Creator: Wiser, W. H. & Oblad, A. G.
Partner: UNT Libraries Government Documents Department

Synthesis of 6-Methyl-9-n-propyldibenzothiophene-4-ol. Quarterly technical progress report No. 5, July 28--October 28, 1991

Description: The material presented here has been described to some extent in Status Reports 12, 13, and 14 and covers the progress toward the synthesis of the modified target molecules 9-isopropyl-4-methoxy-6-methyldibenzothiophene (13) and 9-isopropyl-6-methyldibenzothiophene-4-ol (14). It is divided into three parts: (a) Dehydrogenation experiments On tetrahydrodibenzothiophene 12. (b) methoxyl methyl cleavage of 13 to 14 using boron tribromide. (c) isolation and purification of methoxydibenzothiophene 13.
Date: October 28, 1991
Partner: UNT Libraries Government Documents Department

Mechanism of hydrodenitrogenation preparation of supported Ru catalysts. Twelfth quarter report, July 1--August 31, 1992

Description: A series of Ru oxide catalysts has been prepared and partially characterized. Starting from Ru(NO)(NO{sub 3}){sub 3} to avoid residual Cl in the catalysts, Ru{sup +3} oxides have been prepared in loadings of 1,4 and 8 wt%, over silica, gamma-alumina and silica-aluminas of controlled acidity. The highly dispersed oxides are produced in order to study the controllability of the various types of catalytic functionalities present on HDN catalysts.
Date: December 31, 1992
Creator: Miranda, R.
Partner: UNT Libraries Government Documents Department

Control of catalytic hydrotreating selectivity with ammonia. [Quarterly] report, April 1, 1993--June 30, 1993

Description: We have chosen as our standard reaction conditions: T = 3600, total pressure about 6.9 MPa, partial pressure of PBz = 24.4 kPa, partial pressure of H{sub 2}S = 13.3 kPa, partial pressure of NH{sub 3} = 13.3 kPa, space-time = 200 h. g. cat/mol PBz. The carrier liquid is hexadecane (C{sub 16}H{sub 34}). As before, the H{sub 2}S and NH{sub 3} are generated in situ by hydrogenation of 1-dodecane thiol and n-propyl amine, respectively, added to the C{sub 16} feed. The activity of the fresh catalyst dropped to a steady state level after about 120 hours on stream following which four runs were carried out at p.p. NH{sub 3} values of 0, 13.3, 24.4 and 48.8 kPa, respectively. For each NH{sub 3} p.p., space-times were varied at the following levels: 50, 100, 200, 400 and 600. Analyses were made for propylcyclohexene (C{sub A}), propylcydohexane (C{sub B}) and benzene (C{sub D}). No other products were found in any significant amounts. The ratio C{sub B}/C{sub D} is a measure of the activity for ring hydrogenation relative to hydrocracking. The data are shown in four tables that follow. The results will be analyzed kinetically in the next quarter. However, the following generalizations are evident: NH{sub 3} significantly reduces the activity of the catalyst for both types of reaction. The activity for hydrocracking is reduced more than that for ring hydrogenation, a favorable result, but the effect is not large at the conditions studied thus far. The effect is most evident at low NH{sub 3} concentrations.
Date: September 1, 1993
Creator: Satterfield, C. N. & Gultekin, S.
Partner: UNT Libraries Government Documents Department

Investigations of hydrodenitrogenation of quinoline over molydenum nitride

Description: An investigation has been carried out of the reaction pathway for the hydrodenitrogenation of quinoline over Mo{sub 2}N. Quinoline is found to undergo a rapid hydrogenation to form 1,2,3,4,-tetrahydroquinoline. This product then reacts more slowly to form 2-propylanaline, which in turn undergoes hydrogenolysis of the C-N bond in the saturated ring to form propylbenzene. No evidence is found for propylcyclohexane.
Date: December 1, 1991
Creator: Lee, K. S.; Reimer, J. A. & Bell, A. T.
Partner: UNT Libraries Government Documents Department

Effects of delocalization on intrinsic barriers for H-atom transfer: Implications for the radical hydrogen transfer reaction

Description: PM3 calculations of transition states (TS) for both normal H-atom transfer and radical hydrogen transfer (RHT) reactions of a a wide-variety of hydrocarbon structures have enabled development of quantitative structure-reactivity relationships. Results indicate that activation barriers for RHT reactions are large enough that thermoneutral and endothermic reactions should not compete with alternative multistep pathways.
Date: August 1, 1992
Creator: Camaioni, D. M.; Autrey, S. T.; Ferris, K. F. & Franz, J. A.
Partner: UNT Libraries Government Documents Department

Adsorption of a binary gas mixture which laterally interacts on a random heterogeneous surface

Description: Analytical expressions for the adsorption of a binary gas mixture which laterally interacts on a heterogeneous surface are developed. The lateral interactions are of the Bragg-Williams type and the surface heterogeneity is modeled via a random distribution of sites described by a uniform distribution of Henry`s Law constants. The parametric study shows that complex phase behavior can be predicted, including azeotropes and sigmoidal shaped X-Y diagrams. Also, this model may be useful for modeling and designing adsorption processes as it requires few iterations to simultaneously solve the implicit and coupled algebraic expressions.
Date: October 1, 1992
Creator: Ritter, J. A.
Partner: UNT Libraries Government Documents Department

Particle-like absorption spectra in small transition metal clusters

Description: Research at Argonne has found that small clusters of certain transition metal atoms display optical absorption spectra that are fundamentally different from those typically observed for other small molecules. A new laser technique known as photodissociation spectroscopy was used to record the absorption spectra of nickel clusters containing three to seven atoms and of niobium clusters containing between seven and twenty atoms. Instead of displaying spectra with distinct and separate absorption {open_quotes}bands{close_quotes} as is usually seen for small molecules, these metal clusters possess absorption spectra that are continuous and smooth throughout the visible and near ultraviolet regions, indicating that they absorb light at every wavelength. This behavior is in fact more like that displayed by much larger metal particles containing hundreds or thousands of atoms. This surprising result may indicate that the electronic structures of these small clusters are much closer to those of a corresponding macroscopic piece of nickel or niobium metal than was previously thought. These studies are aimed at understanding the electronic structure of the active metal cluster sites in catalysts, and may in addition provide valuable insights into the design and properties of new cluster assembled materials.
Date: February 1, 1995
Creator: Knickelbein, M. B.
Partner: UNT Libraries Government Documents Department

Interaction of Carbon and Sulfur on Metal Catalysts. Progress Report

Description: Goal is to study selective poisoning by fractional monolayers of chemisorbed sulfur on metal catalysts. A Pt catalyst on alumina support has been synthesized. Stabilized Fe catalysts without and with half monolayers of chemicsorbed S have been prepared. These catalysts, along with a Ni-alumina reference catalyst, will be used in experimental studies. 2 figs.
Date: January 21, 1988
Creator: McCarty, J. G.
Partner: UNT Libraries Government Documents Department

Organometallic chemistry of bimetallic compounds. Progress report, January 1992--July 1995

Description: Four main projects at the interface between organometallic chemistry and homogeneous catalysis were pursued. All were designed to give increased understanding of the mechanisms of organometallic reactions related to homogeneous and heterogeneous catalysis. In addition, a minor study involving {eta}{sup 5}-to {eta}{sup 1}-cyclopentadienyl ring slippage in catalysis was completed.
Date: July 1, 1994
Creator: Casey, C. P.
Partner: UNT Libraries Government Documents Department

Experimental determination of cluster geometrical structure

Description: Chemical probes have been developed to provide insight into the geometrical structure of isolated transition metal clusters. By determining as a function of cluster size the number of adsorbate molecules that saturate a cluster, and/or the binding energy of molecules to cluster surfaces, it is often possible to propose geometrical structures consistent with the experimental observations. The authors review recent studies of the reactions of cobalt, nickel, and copper clusters with ammonia, water, and nitrogen that provide structural information. It is found that small (between 50 and 150 atoms) cobalt, nickel, and copper clusters generally adopt icosahedral packing. However, for even smaller (less than 20 atoms) clusters, cobalt and nickel differ in their structure. The authors also see evidence for adsorbate-induced structural changes. These changes may allow the properties of materials fabricated from such clusters to be tailored to specific needs. A preliminary illustration of the dramatic effect that heteroatoms can have on metal cluster chemical properties is presented.
Date: February 1, 1995
Creator: Riley, S. J.
Partner: UNT Libraries Government Documents Department