Effects of pressure on product transport and enhanced secondary reactions are described, includin... more Effects of pressure on product transport and enhanced secondary reactions are described, including simple ways of modeling them and the beneficial effect of H2. Fractionation of molecular types during vaporization is summarized. Cracking kinetics for oil and model compounds are reviewed. Nearly all results are consistent with an effective activation energy of 56–60 kcal/mol, although a higher energy may be appropriate at the low temperatures and higher pressures associated with cracking in the subsurface. The consequences of ignoring isoconversional character are described.
Hypothetical molecular structures of humic coal, sapropelic kerogens, and asphaltenes are describ... more Hypothetical molecular structures of humic coal, sapropelic kerogens, and asphaltenes are described, including how they change with maturity and how they have been refined over the past 75 years with advances in characterization methods. Due to their importance for modeling oil and gas expulsion , Hildebrand solubility theory and results are outlined. The relationship between aromaticity and coke yield is described. A link is made also between the fundamental mechanism of kerogen decomposition and the types of appropriate global chemical kinetic models.
After introducing the basis of the Arrhenius equation and its relationship to transition-state th... more After introducing the basis of the Arrhenius equation and its relationship to transition-state theory, forms of global chemical kinetic models are summarized, including shrinking core and pseudo nth-order reactions; sigmoidal reactions such as sequential, random scission, autocatalytic, logistic, and nucleation-growth model; and distributed reactivity models, including continuous and discrete activation energy distribution models. Isoconversional and model fitting methods for deriving chemical kinetic models are described, including how to use simple kinetic analyses to derive initial guesses for nonlinear regression of complex models. Common errors that lead to erroneous Arrhenius parameters are outlined.
Methods are reviewed for how to measure pyrolysis kinetics under atmospheric or lower pressure. T... more Methods are reviewed for how to measure pyrolysis kinetics under atmospheric or lower pressure. The effects of heat and mass transfer on apparent chemical reaction rates are discussed, including limits for heating rates and sample size and geometry that result in the sufficiently accurate temperature measurements. Evidence for sequential versus parallel reaction mechanisms is described, including common misinterpretations in the literature. The competition between oil and tar vaporization and coking is outlined, including how it affects product yields and composition. Kinetic parameters for coal, sapropelic kerogens, and asphaltenes are reviewed, with the conclusion that principal activation energies outside the range of about 50-56 kcal/mol are not credible. Relevant global models range from sigmoidal to distributed reactivity depending on the kerogen structure. Keywords Open-system kinetics Á Pyrolysis kinetics Á Kerogen pyrolysis Á Coal pyrolysis Á Activation energy distributions Á DAEM Á Asphaltenes Á Extended Prout-Tompkins model Á Bitumen intermediate Á Oil coking Á Pyromat II Historically, the most common way to measure pyrolysis kinetics is in an open system, i.e., a vessel that allows the products to escape the hot zone as soon as they are volatile. Ordinarily, the surrounding gas is at atmospheric pressure, but in some cases, it is at some level of vacuum or even at elevated pressure, depending on the purpose of the experiment. For this chapter, only experiments at or below atmospheric pressure will be considered in order to concentrate on the kinetics of primary generation reactions. Even under these conditions, however, there is a volatility requirement that means some secondary reactions will occur. Many types of reactors have been used to measure open-system pyrolysis of coal, organic-rich rock, and kerogen. These include fixed beds with or without purge gas, fluidized beds, entrained flow and free-fall reactors, heated grids, shock tubes, and illumination by light sources. Many are not particularly useful for kinetic measurements because the temperature of the sample is poorly known. Reaction extent has been measured by weight loss, heat flow, and evolved product analysis.
Abstract Thermal decomposition of TATB (1,3,5-triamino-2,4,6-trinitrobenzene) and its formulation... more Abstract Thermal decomposition of TATB (1,3,5-triamino-2,4,6-trinitrobenzene) and its formulation LX-17 is studied at pressures from 0.1 to 7 MPa for both isothermal heating at 340 K and ramped heating at 1 to 6 K min-1. Conditions that eliminate self-heating are thoroughly explored to avoid experimental artifacts. The increase in pressure accelerates the rate of decomposition by only about 10%, but it substantially increases the enthalpy of the reaction, presumably because of longer volatile product residence times in the heated zone. The narrowness of the decomposition profile and the acceleratory phase during isothermal pyrolysis are consistent with a multistep autocatalytic mechanism, and the lack of a significant pressure effect suggests that the autocatalytic species have low volatility.
h i g h l i g h t s Equation proposed for oil shale conductivity as a function of grade and tempe... more h i g h l i g h t s Equation proposed for oil shale conductivity as a function of grade and temperature. Equation captures all experimental measurements in the literature for Green River. Developed new approach for mapping conductivity from optical photographs of cores. Approach was used to upscale conductivities for a core in the Green River Formation. Developed analytical expressions obviating costly numerical upscaling in the future.
h i g h l i g h t s Kerogen content of organic-rich shales is quantifiable from near-infrared ima... more h i g h l i g h t s Kerogen content of organic-rich shales is quantifiable from near-infrared images. Spectral models are developed for the thermally immature Green River Formation. Models are used to map organic content for an entire core at high resolution.
Several regions of the world have abundant oil shale resources, but accessing this energy supply ... more Several regions of the world have abundant oil shale resources, but accessing this energy supply poses a number of challenges. One particular difficulty is the thermomechanical behavior of the material. When heated to sufficient temperatures, thermal conversion of kerogen to oil, gas, and other products takes place. This alteration of microstructure leads to a complex geomechanical response. In this work, we develop a thermoplasticity model for oil shale. The model is based on critical state plasticity, a framework often used for modeling clays and soft rocks. The model described here allows for both hardening due to mechanical deformation and softening due to thermal processes. In particular, the preconsolidation pressure—defining the onset of plastic volumetric compaction—is controlled by a state variable representing the kerogen content of the material. As kerogen is converted to other phases, the material weakens and plastic compaction begins. We calibrate and compare the proposed model to a suite of high-temperature uniaxial and triaxial experiments on core samples from a pilot in situ processing operation in the Green River Formation. We also describe avenues for future work to improve understanding and prediction of the geomechanical behavior of oil shale operations.
h i g h l i g h t s Estimate compaction and porosity during diagenesis as a function of organic c... more h i g h l i g h t s Estimate compaction and porosity during diagenesis as a function of organic content. Calculate porosity as a function of oil shale grade and kerogen conversion during in-situ retorting. Estimate permeability from porosity using simple engineering correlations.
Various silica sols, with different surface chemistries, were reacted in solvent dispersions with... more Various silica sols, with different surface chemistries, were reacted in solvent dispersions with hexamethyldisilazane (HMDS) or ethoxytrimethylsilane (ETMS) to produce hydrophobic, trimethylsilyl (TMS) functionalized sols. 1 H and 29 Si nuclear magnetic resonance were used to quantify the surface species and the TMS surface coverage. The amount of TMS surface coverage, which ranged from 5% to 33%, was a strong function of the starting silica-surface chemistry and the HMDS reaction time. Sols with a greater hydrogen-bonded silanol surface (as opposed to an ethoxy surface or isolated silanol surface) resulted in greater TMS coverage. HMDS reacts with both the solvent (ethanol) and the silica surface. Reaction rate measurements suggested that the silica surface reacts with HMDS at short times (minutes) and then with ETMS, which is a product of the HMDS/ethanol reaction, at long times (days). High TMS coverage is required for sol stability in non-polar solvents; the colloid size was found to increase in decane for sols with poor TMS coverage. In addition, coatings made from TMS sols showed an 80Â slower remaining ethoxy-surface hydrolysis rate upon exposure to humidity than untreated sols. These TMS sol films will be utilized as anti-reflection coatings on moisture sensitive optics (e.g., potassium dihydrogen phosphate (KDP) crystals) used in high-peak-power laser systems.
Vacuum degrades the transmittance and catastrophic damage performance of fused-silica surfaces, b... more Vacuum degrades the transmittance and catastrophic damage performance of fused-silica surfaces, both bare and silica-sol anti-reflective coated. These effects may be important in certain space application of photonics devices. When exposed to hundreds of 355-rim, 10-ns laser pulses with fluences in the 2-15 J/cm2 range, transmittance loss is due to both increased reflectance and absorption at the surface. Spectroscopic measurements show that the absorbed light induces broadband fluorescence from the visible to infrared and that the peak photohuninescence wavelength depends cumulative fluence. The effect appears to be consistent with the formation of surface SiO. (x<2) with progressively lower x as cumulative fluence increases. Conversely, low fluence CW UV irradiation of fluorescent sites in air reduces the fluorescence signal, which suggests a photochemical oxidation reaction back to Si02. The occurrence of catastrophic damage (craters that grow on each subsequent pulse) also increases in a vacuum relative to air for both coated and uncoated samples. In both cases, the 50% damage probability for 100 one-mm sites decreases from about 45 to 35 J/cm2 for superpolished fused silica at pressures in the 10-6 Torr range. The damage probability distribution in 10 Torr of air is close to that at one atmosphere of air. The damage morphology of the crater formed in vacuum differs substantially from that in air and has a more melted appearance and does not show cracking and flaking. These differences are possibly due to more coupling of the plasma shock wave into the surface with air present but slower heat dissipation in a vacuum. While it is attractive to propose that formation of sub-stoichiometric silica on the surface in a vacuum environment enhances the probability of catastrophic damage, initial experiments have not yet been able to establish a mechanistic link between the two phenomena.
Yields of gases, water, water-soluble organics, and water-insoluble char are reported for hydroth... more Yields of gases, water, water-soluble organics, and water-insoluble char are reported for hydrothermal pretreatment of paper dunnage at several conditions. Chars are characterized in terms of chemical composition, slurry-forming properties, and pyrolysis properties. Pyrolysis yields, relative reactivities, and kinetic parameters for evolution of volatile organic components from isolated chars were determined by Pyromat micropyrolysis. For both the water-insoluble chars and solvent-extracted chars, pyrolysate yields decreased with increasing pyrolysis severity, and the temperature of maximum evolution rate for a constant heating rate (T max) increased. The extracted residues have less low-temperature evolution and narrower evolution profiles overall. Kinetic analysis used the T max shift (approximate) and discrete distribution methods. Except for one sample, all of the extracted chars have similar kinetic parameters, i.e., activation energies in the range of 54-56 kcal/mol and frequency factors in the range of 10 15 s-1. The exception was from the most severe pretreatment conditions and exhibited much higher activation energies. FTIR analyses of the extracted chars and isolated extracts indicate the structures of the extracted chars are very similar, except for the most severe pretreatment sample. The results are used to assess the suitability and limitations of a parallel reaction model for pyrolysis of paper, especially for modeling hydrothermal pretreatment of gasifier slurry feeds.
ÐRate constants for thermal decomposition of isotopically labeled dodecylbenzene and dodecylcyclo... more ÐRate constants for thermal decomposition of isotopically labeled dodecylbenzene and dodecylcyclohexane doped in n-C 16 and crude oil matrices were measured in sealed glass tubes at 310± 3608C. The rate varied by a factor of 1.5 in the various matrices, but there was no clear relationship with matrix composition. The decomposition rate of dodecylcyclohexane is very close to that of n-C 16 , and comparison to literature data suggests that the activation energy is similar as well. The decomposition rate of dodecylbenzene is about 4 times faster than of n-C 16 , and the activation energy may also be lower. This is consistent with the dealkylation of aromatics to form additional saturates as being a signi®cant reaction during the early stages of oil maturation.
Journal of vacuum science & technology, Nov 1, 1987
Glass shells have been used traditionally as the deuterium-tritium fuel container for direct-driv... more Glass shells have been used traditionally as the deuterium-tritium fuel container for direct-drive laser fusion experiments because oftheir convenience and a vailabili ty, but lower-Z fuel containers have superior implosion characteristics and diagnostic possibilities. Unfortunately, polymers such as polystyrene (PS) that produce shells easily have very high permeabilities so require cryogenics to retain fuel, and impermeable polymers such as polyvinyl alcohol (PV A) are difficult to make into high-quality shells. We have developed improved methods of making PS shells with diameters from 0.2 to 0.7 mm and coating them with a 3-,um layer ofPV A to obtain the advantages of both. Both the PS shells and the PV A coating are made in drop towers using gasstripped nozzles. Details of the procedures and product quality are discussed.
We use chemical kinetic parameters for oil generation derived from modified Rock-Eval and Pyromat... more We use chemical kinetic parameters for oil generation derived from modified Rock-Eval and Pyromat instruments, coupled with thermal history models, to predict the timing and extent of oil generation in the Maracaibo Basin of Venezuela. The vitrinite reflectance model developed at Lawrence Livermore National Laboratory is used to calibrate thermal history models with measured vitrinite reflectance profiles. We examine the way differences in the kinetic parameters affect predictions of maturation in several parts of the basin with different thermal histories. Maturity indicators, such as H/C atomic ratio of residual kerogen and API gravity of reservoired oil, are compared to the calculated extent of oil generation. We use the comparison to check the accuracy of the coupled oil generation and thermal history models.
This is a preprint of a paper intended for publication in a journal or proceedings. Since changes... more This is a preprint of a paper intended for publication in a journal or proceedings. Since changes may be made before publication, this preprint is made available with the understanding that it will not be cited or reproduced without the permission of the author.
Journal of Thermal Analysis and Calorimetry, Jul 19, 2007
Current work at the Energetic Materials Center, EMC, at Lawrence Livermore National Laboratory (L... more Current work at the Energetic Materials Center, EMC, at Lawrence Livermore National Laboratory (LLNL) includes both understanding properties of old explosives and measuring properties of new ones [1]. The necessity to know and understand the properties of energetic materials is driven by the need to improve performance and enhance stability to various stimuli, such as thermal, friction and impact insult. This review will concentrate on the physical properties of RX-55-AE-5, which is formulated from heterocyclic explosive, 2,6-diamino-3,5dinitropyrazine-1-oxide, LLM-105, and 2.5 % Viton A. Differential scanning calorimetry (DSC) was used to measure a specific heat capacity, C p , of ≈ 0.950 J/g•˚C, and a thermal conductivity, κ, of ≈ 0.475 W/m•˚C. The LLNL kinetics modeling code Kinetics05 and the Advanced Kinetics and Technology Solutions (AKTS) code Thermokinetics were both used to calculate Arrhenius kinetics for decomposition of LLM-105. Both obtained an activation energy barrier E ≈ 180 kJ mol-1 for mass loss in an open pan. Thermal mechanical analysis, TMA, was used to measure the coefficient of thermal expansion (CTE). The CTE for this formulation was calculated to be ≈ 61 µm/m•˚C. Impact, spark, friction are also reported.
Effects of pressure on product transport and enhanced secondary reactions are described, includin... more Effects of pressure on product transport and enhanced secondary reactions are described, including simple ways of modeling them and the beneficial effect of H2. Fractionation of molecular types during vaporization is summarized. Cracking kinetics for oil and model compounds are reviewed. Nearly all results are consistent with an effective activation energy of 56–60 kcal/mol, although a higher energy may be appropriate at the low temperatures and higher pressures associated with cracking in the subsurface. The consequences of ignoring isoconversional character are described.
Hypothetical molecular structures of humic coal, sapropelic kerogens, and asphaltenes are describ... more Hypothetical molecular structures of humic coal, sapropelic kerogens, and asphaltenes are described, including how they change with maturity and how they have been refined over the past 75 years with advances in characterization methods. Due to their importance for modeling oil and gas expulsion , Hildebrand solubility theory and results are outlined. The relationship between aromaticity and coke yield is described. A link is made also between the fundamental mechanism of kerogen decomposition and the types of appropriate global chemical kinetic models.
After introducing the basis of the Arrhenius equation and its relationship to transition-state th... more After introducing the basis of the Arrhenius equation and its relationship to transition-state theory, forms of global chemical kinetic models are summarized, including shrinking core and pseudo nth-order reactions; sigmoidal reactions such as sequential, random scission, autocatalytic, logistic, and nucleation-growth model; and distributed reactivity models, including continuous and discrete activation energy distribution models. Isoconversional and model fitting methods for deriving chemical kinetic models are described, including how to use simple kinetic analyses to derive initial guesses for nonlinear regression of complex models. Common errors that lead to erroneous Arrhenius parameters are outlined.
Methods are reviewed for how to measure pyrolysis kinetics under atmospheric or lower pressure. T... more Methods are reviewed for how to measure pyrolysis kinetics under atmospheric or lower pressure. The effects of heat and mass transfer on apparent chemical reaction rates are discussed, including limits for heating rates and sample size and geometry that result in the sufficiently accurate temperature measurements. Evidence for sequential versus parallel reaction mechanisms is described, including common misinterpretations in the literature. The competition between oil and tar vaporization and coking is outlined, including how it affects product yields and composition. Kinetic parameters for coal, sapropelic kerogens, and asphaltenes are reviewed, with the conclusion that principal activation energies outside the range of about 50-56 kcal/mol are not credible. Relevant global models range from sigmoidal to distributed reactivity depending on the kerogen structure. Keywords Open-system kinetics Á Pyrolysis kinetics Á Kerogen pyrolysis Á Coal pyrolysis Á Activation energy distributions Á DAEM Á Asphaltenes Á Extended Prout-Tompkins model Á Bitumen intermediate Á Oil coking Á Pyromat II Historically, the most common way to measure pyrolysis kinetics is in an open system, i.e., a vessel that allows the products to escape the hot zone as soon as they are volatile. Ordinarily, the surrounding gas is at atmospheric pressure, but in some cases, it is at some level of vacuum or even at elevated pressure, depending on the purpose of the experiment. For this chapter, only experiments at or below atmospheric pressure will be considered in order to concentrate on the kinetics of primary generation reactions. Even under these conditions, however, there is a volatility requirement that means some secondary reactions will occur. Many types of reactors have been used to measure open-system pyrolysis of coal, organic-rich rock, and kerogen. These include fixed beds with or without purge gas, fluidized beds, entrained flow and free-fall reactors, heated grids, shock tubes, and illumination by light sources. Many are not particularly useful for kinetic measurements because the temperature of the sample is poorly known. Reaction extent has been measured by weight loss, heat flow, and evolved product analysis.
Abstract Thermal decomposition of TATB (1,3,5-triamino-2,4,6-trinitrobenzene) and its formulation... more Abstract Thermal decomposition of TATB (1,3,5-triamino-2,4,6-trinitrobenzene) and its formulation LX-17 is studied at pressures from 0.1 to 7 MPa for both isothermal heating at 340 K and ramped heating at 1 to 6 K min-1. Conditions that eliminate self-heating are thoroughly explored to avoid experimental artifacts. The increase in pressure accelerates the rate of decomposition by only about 10%, but it substantially increases the enthalpy of the reaction, presumably because of longer volatile product residence times in the heated zone. The narrowness of the decomposition profile and the acceleratory phase during isothermal pyrolysis are consistent with a multistep autocatalytic mechanism, and the lack of a significant pressure effect suggests that the autocatalytic species have low volatility.
h i g h l i g h t s Equation proposed for oil shale conductivity as a function of grade and tempe... more h i g h l i g h t s Equation proposed for oil shale conductivity as a function of grade and temperature. Equation captures all experimental measurements in the literature for Green River. Developed new approach for mapping conductivity from optical photographs of cores. Approach was used to upscale conductivities for a core in the Green River Formation. Developed analytical expressions obviating costly numerical upscaling in the future.
h i g h l i g h t s Kerogen content of organic-rich shales is quantifiable from near-infrared ima... more h i g h l i g h t s Kerogen content of organic-rich shales is quantifiable from near-infrared images. Spectral models are developed for the thermally immature Green River Formation. Models are used to map organic content for an entire core at high resolution.
Several regions of the world have abundant oil shale resources, but accessing this energy supply ... more Several regions of the world have abundant oil shale resources, but accessing this energy supply poses a number of challenges. One particular difficulty is the thermomechanical behavior of the material. When heated to sufficient temperatures, thermal conversion of kerogen to oil, gas, and other products takes place. This alteration of microstructure leads to a complex geomechanical response. In this work, we develop a thermoplasticity model for oil shale. The model is based on critical state plasticity, a framework often used for modeling clays and soft rocks. The model described here allows for both hardening due to mechanical deformation and softening due to thermal processes. In particular, the preconsolidation pressure—defining the onset of plastic volumetric compaction—is controlled by a state variable representing the kerogen content of the material. As kerogen is converted to other phases, the material weakens and plastic compaction begins. We calibrate and compare the proposed model to a suite of high-temperature uniaxial and triaxial experiments on core samples from a pilot in situ processing operation in the Green River Formation. We also describe avenues for future work to improve understanding and prediction of the geomechanical behavior of oil shale operations.
h i g h l i g h t s Estimate compaction and porosity during diagenesis as a function of organic c... more h i g h l i g h t s Estimate compaction and porosity during diagenesis as a function of organic content. Calculate porosity as a function of oil shale grade and kerogen conversion during in-situ retorting. Estimate permeability from porosity using simple engineering correlations.
Various silica sols, with different surface chemistries, were reacted in solvent dispersions with... more Various silica sols, with different surface chemistries, were reacted in solvent dispersions with hexamethyldisilazane (HMDS) or ethoxytrimethylsilane (ETMS) to produce hydrophobic, trimethylsilyl (TMS) functionalized sols. 1 H and 29 Si nuclear magnetic resonance were used to quantify the surface species and the TMS surface coverage. The amount of TMS surface coverage, which ranged from 5% to 33%, was a strong function of the starting silica-surface chemistry and the HMDS reaction time. Sols with a greater hydrogen-bonded silanol surface (as opposed to an ethoxy surface or isolated silanol surface) resulted in greater TMS coverage. HMDS reacts with both the solvent (ethanol) and the silica surface. Reaction rate measurements suggested that the silica surface reacts with HMDS at short times (minutes) and then with ETMS, which is a product of the HMDS/ethanol reaction, at long times (days). High TMS coverage is required for sol stability in non-polar solvents; the colloid size was found to increase in decane for sols with poor TMS coverage. In addition, coatings made from TMS sols showed an 80Â slower remaining ethoxy-surface hydrolysis rate upon exposure to humidity than untreated sols. These TMS sol films will be utilized as anti-reflection coatings on moisture sensitive optics (e.g., potassium dihydrogen phosphate (KDP) crystals) used in high-peak-power laser systems.
Vacuum degrades the transmittance and catastrophic damage performance of fused-silica surfaces, b... more Vacuum degrades the transmittance and catastrophic damage performance of fused-silica surfaces, both bare and silica-sol anti-reflective coated. These effects may be important in certain space application of photonics devices. When exposed to hundreds of 355-rim, 10-ns laser pulses with fluences in the 2-15 J/cm2 range, transmittance loss is due to both increased reflectance and absorption at the surface. Spectroscopic measurements show that the absorbed light induces broadband fluorescence from the visible to infrared and that the peak photohuninescence wavelength depends cumulative fluence. The effect appears to be consistent with the formation of surface SiO. (x<2) with progressively lower x as cumulative fluence increases. Conversely, low fluence CW UV irradiation of fluorescent sites in air reduces the fluorescence signal, which suggests a photochemical oxidation reaction back to Si02. The occurrence of catastrophic damage (craters that grow on each subsequent pulse) also increases in a vacuum relative to air for both coated and uncoated samples. In both cases, the 50% damage probability for 100 one-mm sites decreases from about 45 to 35 J/cm2 for superpolished fused silica at pressures in the 10-6 Torr range. The damage probability distribution in 10 Torr of air is close to that at one atmosphere of air. The damage morphology of the crater formed in vacuum differs substantially from that in air and has a more melted appearance and does not show cracking and flaking. These differences are possibly due to more coupling of the plasma shock wave into the surface with air present but slower heat dissipation in a vacuum. While it is attractive to propose that formation of sub-stoichiometric silica on the surface in a vacuum environment enhances the probability of catastrophic damage, initial experiments have not yet been able to establish a mechanistic link between the two phenomena.
Yields of gases, water, water-soluble organics, and water-insoluble char are reported for hydroth... more Yields of gases, water, water-soluble organics, and water-insoluble char are reported for hydrothermal pretreatment of paper dunnage at several conditions. Chars are characterized in terms of chemical composition, slurry-forming properties, and pyrolysis properties. Pyrolysis yields, relative reactivities, and kinetic parameters for evolution of volatile organic components from isolated chars were determined by Pyromat micropyrolysis. For both the water-insoluble chars and solvent-extracted chars, pyrolysate yields decreased with increasing pyrolysis severity, and the temperature of maximum evolution rate for a constant heating rate (T max) increased. The extracted residues have less low-temperature evolution and narrower evolution profiles overall. Kinetic analysis used the T max shift (approximate) and discrete distribution methods. Except for one sample, all of the extracted chars have similar kinetic parameters, i.e., activation energies in the range of 54-56 kcal/mol and frequency factors in the range of 10 15 s-1. The exception was from the most severe pretreatment conditions and exhibited much higher activation energies. FTIR analyses of the extracted chars and isolated extracts indicate the structures of the extracted chars are very similar, except for the most severe pretreatment sample. The results are used to assess the suitability and limitations of a parallel reaction model for pyrolysis of paper, especially for modeling hydrothermal pretreatment of gasifier slurry feeds.
ÐRate constants for thermal decomposition of isotopically labeled dodecylbenzene and dodecylcyclo... more ÐRate constants for thermal decomposition of isotopically labeled dodecylbenzene and dodecylcyclohexane doped in n-C 16 and crude oil matrices were measured in sealed glass tubes at 310± 3608C. The rate varied by a factor of 1.5 in the various matrices, but there was no clear relationship with matrix composition. The decomposition rate of dodecylcyclohexane is very close to that of n-C 16 , and comparison to literature data suggests that the activation energy is similar as well. The decomposition rate of dodecylbenzene is about 4 times faster than of n-C 16 , and the activation energy may also be lower. This is consistent with the dealkylation of aromatics to form additional saturates as being a signi®cant reaction during the early stages of oil maturation.
Journal of vacuum science & technology, Nov 1, 1987
Glass shells have been used traditionally as the deuterium-tritium fuel container for direct-driv... more Glass shells have been used traditionally as the deuterium-tritium fuel container for direct-drive laser fusion experiments because oftheir convenience and a vailabili ty, but lower-Z fuel containers have superior implosion characteristics and diagnostic possibilities. Unfortunately, polymers such as polystyrene (PS) that produce shells easily have very high permeabilities so require cryogenics to retain fuel, and impermeable polymers such as polyvinyl alcohol (PV A) are difficult to make into high-quality shells. We have developed improved methods of making PS shells with diameters from 0.2 to 0.7 mm and coating them with a 3-,um layer ofPV A to obtain the advantages of both. Both the PS shells and the PV A coating are made in drop towers using gasstripped nozzles. Details of the procedures and product quality are discussed.
We use chemical kinetic parameters for oil generation derived from modified Rock-Eval and Pyromat... more We use chemical kinetic parameters for oil generation derived from modified Rock-Eval and Pyromat instruments, coupled with thermal history models, to predict the timing and extent of oil generation in the Maracaibo Basin of Venezuela. The vitrinite reflectance model developed at Lawrence Livermore National Laboratory is used to calibrate thermal history models with measured vitrinite reflectance profiles. We examine the way differences in the kinetic parameters affect predictions of maturation in several parts of the basin with different thermal histories. Maturity indicators, such as H/C atomic ratio of residual kerogen and API gravity of reservoired oil, are compared to the calculated extent of oil generation. We use the comparison to check the accuracy of the coupled oil generation and thermal history models.
This is a preprint of a paper intended for publication in a journal or proceedings. Since changes... more This is a preprint of a paper intended for publication in a journal or proceedings. Since changes may be made before publication, this preprint is made available with the understanding that it will not be cited or reproduced without the permission of the author.
Journal of Thermal Analysis and Calorimetry, Jul 19, 2007
Current work at the Energetic Materials Center, EMC, at Lawrence Livermore National Laboratory (L... more Current work at the Energetic Materials Center, EMC, at Lawrence Livermore National Laboratory (LLNL) includes both understanding properties of old explosives and measuring properties of new ones [1]. The necessity to know and understand the properties of energetic materials is driven by the need to improve performance and enhance stability to various stimuli, such as thermal, friction and impact insult. This review will concentrate on the physical properties of RX-55-AE-5, which is formulated from heterocyclic explosive, 2,6-diamino-3,5dinitropyrazine-1-oxide, LLM-105, and 2.5 % Viton A. Differential scanning calorimetry (DSC) was used to measure a specific heat capacity, C p , of ≈ 0.950 J/g•˚C, and a thermal conductivity, κ, of ≈ 0.475 W/m•˚C. The LLNL kinetics modeling code Kinetics05 and the Advanced Kinetics and Technology Solutions (AKTS) code Thermokinetics were both used to calculate Arrhenius kinetics for decomposition of LLM-105. Both obtained an activation energy barrier E ≈ 180 kJ mol-1 for mass loss in an open pan. Thermal mechanical analysis, TMA, was used to measure the coefficient of thermal expansion (CTE). The CTE for this formulation was calculated to be ≈ 61 µm/m•˚C. Impact, spark, friction are also reported.
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Papers by Alan Burnham