Desulfurization of coal-derived pyrite using solutions containing dissolved oxygen. (open access)

Desulfurization of coal-derived pyrite using solutions containing dissolved oxygen.

The effect of alkaline solutions containing dissolved oxygen on coal-derived pyrite was investigated in a tubular reactor. The rate of total sulfur conversion seems to be affected by oxygen partial pressure, oxygen flow rate, particle size, pyrite charge size and system temperature. A shrinking core model was chosen to represent this chemical leaching process. From the results obtained, it seems that ash or product-layer difusion is the rate-limiting step for leaching with the alkaline solution/oxygen system. The effective diffusivity is about 10/sup -5/ cm/sup 2//sec. The apparent activation energy for this process is 7.97 kcal/mole in the temperature range from 121/sup 0/ to 175/sup 0/C. For the tubular reactor system used, the rate of sulfur extraction appears to be proportional to the oxygen partial pressure. The rate of conversion increases as the oxygen flow rate decreases to a limit of 3 ml/sec. The rate also increases as the pyrite charge size decreases. The leaching solutions flow rate has a negligible effect on the total sulfur conversion.
Date: July 1, 1979
Creator: Chen, M. C.
System: The UNT Digital Library
Methanation reaction on ruthenium thin films: a mechanistic investigation. (open access)

Methanation reaction on ruthenium thin films: a mechanistic investigation.

The kinetics of the methanation reaction were measured on thin ruthenium films in the temperature range 548 to 623K. The pressures of the reactant gases were varied over the ranges 1.5 to 1500 ..mu..m for CO and 300 to 75000 ..mu..m for H/sub 2/ to yield kinetic orders for each gas. The CO kinetic order varied from +1 at low pressures to -2 at high pressures. As the H/sub 2/ pressure was increased its kinetic order varied from +2 to -1. Both of these order plots had unusually sharp maxima. The reaction is zero order in both CH/sub 4/ and H/sub 2/O. The apparent activation energy was dependent upon temperature with a value of 21.9 kcal/mole at 573K. Auger spectroscopy (AES) and x-ray photoelectron spectroscopy (XPS) indicated that the surface was always covered with carbon. This carbon could be divided into two types based upon its reactivity toward hydrogen. Type-1 was very reactive to 3.5 torr hydrogen doses at 573K and was completely removed in less than 300 seconds. Type-2 was less reactive and required about 48 hours under the same conditions for removal. No oxygen was ever detected on the surface after methanation. Low energy electron diffraction (LEED) and …
Date: July 1, 1979
Creator: Slaughter, M. D.
System: The UNT Digital Library
Neutron-capture gamma-ray analysis of coal for sulfur, iron, silicon and moisture. (open access)

Neutron-capture gamma-ray analysis of coal for sulfur, iron, silicon and moisture.

Samples of coal weighing approximately 200 grams placed in a collimated beam of neutrons from the thermal column of the Ames Laboratory Research Reactor produced capture gamma-rays which could be used for the simultaneous determination of sulfur and iron. Spectra from NaI(Tl) and Ge(Li) detectors were used and interferences were located by examining spectra of the major elemental components of coal. In determining sulfur, iron is a potential source of interference when gamma-ray spectra are collected with a NaI(Tl) detector. Corrections for iron interference were made by use of a higher energy iron peak. The possibility of determining silicon in coal was investigated but this element determination was unsuccessful since capture gamma-ray spectrometry lacked the necessary sensitivity for silicon. A linear relation was found between the area of the hydrogen capture peak at 2.23 MeV and the amount of water added to coal.
Date: May 1, 1979
Creator: Fay, D. A.
System: The UNT Digital Library
Desulfurization of coal model compounds and coal liquids. (open access)

Desulfurization of coal model compounds and coal liquids.

Most US coals contain sulfur concentrations that prevent their being burned without some form of sulfur removal. Current coal-cleaning technology can only remove the fairly reactive pyritic (inorganic) and aliphatic (organic) sulfur. A process which removes the more refractory hetero-aromatic sulfur could substantially increase the amount of coal reserves amenable to chemical cleaning. Sodium metal dispersions convert refractor model compounds into lighter desulfurized products and non-volatile sulfur-rich char. When treated with sodium, coal-derived solids show substantial desulfurization. The same treatment applied to coal-derived liquids, when combined with vacuum distillation of the reaction product, yields a desulfurized light distillate, an increase in absolute amount of distillate, and retention of sulfur in the vacuum residue. The presence of sodium in the residue allows fixation of the residual sulfur as Na/sub 2/SO/sub 4/ upon combustion, eliminating production of SO/sub 2/ in the flue gas. Intimate contacting of sodium salts with high sulfur coal also fixes 97 to 99% of the sulfur as Na/sub 2/SO/sub 4/ upon combustion. This technique takes advantage of the high energy available for carbon-sulfur bond cleavage during combustion and the reaction of SO/sub 2/ to form Na/sub 2/SO/sub 4/ to provide an inexpensive method for complete coal desulfurization.
Date: April 1, 1979
Creator: Wrathall, James Anthony & Peterson, Eugene E.
System: The UNT Digital Library
Impact of surface coal mining and reclamation on the hydrogeology at Iowa Coal Project Demonstration Mine No. 1, Mahaska County, Iowa (open access)

Impact of surface coal mining and reclamation on the hydrogeology at Iowa Coal Project Demonstration Mine No. 1, Mahaska County, Iowa

The groundwater effects of surface mining at ICP No. 1 can be classified primarily as water quality and water quantity effects. The water quantity effects are: the loss of groundwater saturation in spoil materials that were initially removed from over the coal and later replaced; the dewatering of high permeability geologic strata up gradient of mining area; the increase in porosity and possibly permeability in refilled spoil materials; and the change in groundwater gradients in mined areas and near the sediment pond. The water quality effects are: the generation of slightly mineralized enclaves near the sediment pond and spoil accumulations; the generation of thin zones of highly mineralized water near the base of reclaimed spoil probably due mostly to remnant acid mine water; and reduction of water quality in coal seams as a result of dewatering at the time of mining and subsequent oxidation of their pyrite content. Most effects of water quantity loss in and around the mine are not permanent. Water quality disturbances of the fringe areas of reclaimed mine areas will be very slow in attenuating because of the slow groundwater flow through these materials. Adulterated groundwaters in high permeability areas such as the flood plain alluvium …
Date: July 1, 1979
Creator: Stangl, D. W.
System: The UNT Digital Library
Applications of solid state nuclear magnetic resonance techniques to the study of coals and polymers. (open access)

Applications of solid state nuclear magnetic resonance techniques to the study of coals and polymers.

The use of Nuclear Magnetic Resonance (NMR) to study molecules in the solid state has grown rapidly over the past several years. This is due to the advent of techniques which allow for the removal of certain interactions in the solid state which previously have thwarted most attempts at obtaining chemical shift or their anisotropies. With these parameters and others now available, NMR has become an important tool to be used in the understanding of the chemistry of solids. The work reported in this dissertation applies the techniques of solid state NMR to a number of chemical systems. Specific applications are made to crystallinity in polymers, to combined sample spinning and multiple pulse techniques, and to aromatic and aliphatic content of vitrain portions of coals of varying carbon content.
Date: January 1, 1979
Creator: Pembleton, R. G.
System: The UNT Digital Library
Studies of Electron Correlation in the Photoionization Process (open access)

Studies of Electron Correlation in the Photoionization Process

Electron correlation is a result of the interaction of two or more electrons confined in a region of space, and may conveniently be treated under the formalism of configuration interaction (CI). Photoionization provides a rather direct experimental method for studying configuration interaction. The types of CI involved in the photoionization process can be divided into three categories: initial state configuration interaction (ISCI), final ionic state configuration interaction (FISCI), and continuum state configuration interaction (CSCI). This thesis deals with experimental studies which reveal how the various types of CI may become manifested in photoionization. The experimental methods utilized in this work are photoelectron spectroscopy (PES), electron impact spectroscopy (EIS), and time-resolved fluorescence spectroscopy. The EIS was carried out following the discovery that the UV lamp on a Perkin-Elmer photoelectron spectrometer could be utilized as a source of low energy electrons. The time-resolved fluorescence work utilized both the tunability and the time structure of the radiation available at the Stanford Synchrotron Radiation Laboratory (SSRL). A commercial photoelectron spectrometer equipped with a conventional UV lamp (Hei, Nei) was employed for some of the PES studies, and a novel time-of-flight photoelectron spectrometer was developed for the PES work performed using synchrotron radiation. The PES …
Date: March 1, 1979
Creator: Rosenberg, Richard Allen
System: The UNT Digital Library
THE INTERACTION OF THE Eco RI RESTRICTION ENZYME FROM E.coli WITH NUCLEOTIDES (open access)

THE INTERACTION OF THE Eco RI RESTRICTION ENZYME FROM E.coli WITH NUCLEOTIDES

The Eco R1 restriction enzyme can be shown to be inhibited by nucleotides which correspond to any part of its known site of phosphodiesterase activity. A series of di-, tetra-, and hexa-nucleotide fragments were synthesized and their effect on the activity of the enzyme upon superhelical Co1 E1 DNA studied. The inhibition caused by the individual mononucleotides were also studied. In general all the nucleotide fragments showed some form of interaction with the enzyme system. Tetranucleotides were stronger inhibitors than dinucleotides, which in turn were stronger inhibitors than the mononucleotides. Within each category of inhibitors, those containing the phosphodiester bond which is acted upon by the enzyme were the strongest inhibitors. Only those fragments which were consistent with the enzymes site of activity showed competitive inhibition kinetics. Nucleotides which do not fit within the site of phosphodiesterase activity show non-competitive inhibition kinetics.
Date: November 1, 1979
Creator: Hollis, Donald F.
System: The UNT Digital Library
INDEPENDENT PARTICLE ASPECTS OF NUCLEAR DYNAMICS (open access)

INDEPENDENT PARTICLE ASPECTS OF NUCLEAR DYNAMICS

A generalization of the independent particle model from nuclear statics to nuclear dynamics is sought. Attention is centered on the average behavior of nuclear dynamics, as opposed to detailed behavior, such as that characteristic of shell effects in nuclear statics. In many situations, all that is needed is a model of dissipation in nuclear dynamics. Completely independent nucleons produce dissipation only when they interact with the surface of a nucleus or when they cross from one nucleus to another. The first possibility manifests itself whenever a nuclear surface deforms. Dissipation is then described by a simple 'wall formula.' The second mechanism for dissipation is relevant whenever two nuclei are moving relative to one another and are in sufficient contact that nucleons can move between them. Another simple expression, the 'window formula,' describes dissipation in this case. Neither of the two formulae has any free parameters.
Date: May 1, 1979
Creator: Robel, M.C.
System: The UNT Digital Library
Reactivity patterns of transition metal hydrides and alkyls (open access)

Reactivity patterns of transition metal hydrides and alkyls

The complex PPN/sup +/ CpV(CO)/sub 3/H/sup -/ (Cp=eta/sup 5/-C/sub 5/H/sub 5/ and PPN = (Ph/sub 3/P)/sub 2/) was prepared in 70% yield and its physical properties and chemical reactions investigated. PPN/sup +/ CpV(CO)/sub 3/H/sup -/ reacts with a wide range of organic halides. The organometallic products of these reactions are the vanadium halides PPN/sup +/(CpV(C)/sub 3/X)/sup -/ and in some cases the binuclear bridging hydride PPN/sup +/ (CpV(CO)/sub 3/)/sub 2/H/sup -/. The borohydride salt PPN/sup +/(CpV(CO)/sub 3/BH/sub 4/)/sup -/ has also been prepared. The reaction between CpV(CO)/sub 3/H/sup -/ and organic halides was investigated and compared with halide reductions carried out using tri-n-butyltin hydride. Results demonstrate that in almost all cases, the reduction reaction proceeds via free radical intermediates which are generated in a chain process, and are trapped by hydrogen transfer from CpV(CO)/sub 3/H/sup -/. Sodium amalgam reduction of CpRh(CO)/sub 2/ or a mixture of CpRh(CO)/sub 2/ and CpCo(CO)/sub 2/ affords two new anions, PPN/sup +/ (Cp/sub 2/Rh/sub 3/(CO)/sub 4/)/sup -/ and PPN/sup +/(Cp/sub 2/RhCo(CO)/sub 2/)/sup -/. CpMo(CO)/sub 3/H reacts with CpMo(CO)/sub 3/R (R=CH/sub 3/,C/sub 2/H/sub 5/, CH/sub 2/C/sub 6/H/sub 5/) at 25 to 50/sup 0/C to produce aldehyde RCHO and the dimers (CpMo(CO)/sub 3/)/sub 2/ and (CpMo(CO)/sub 2/)/sub …
Date: May 1, 1979
Creator: Jones, WIlliam Davidson, II
System: The UNT Digital Library