Search

The Bakken Formation is a major unconventional tight oil play in North America. The potential for the Bakken to serve as a target for CO 2 storage and CO 2 -based enhanced oil recovery was examined using advanced characterization techniques, laboratory experiments, and modeling. Bakken rocks are dominated by nanoscale pore throats, and although porosity is low, much of the nanoscale porosity is connected. Collectively, the characterization, experimental, and modeling results suggest the nanoscale pore throats make important contributions as transport pathways for CO 2 storage and oil mobilization in the Bakken.

Many depleted oil and gas reservoirs are targets for commercial CO 2 enhanced oil recovery, resulting in associated CO 2 storage which occurs as part of the process. These oil fields have legacy wellbores that may contain a leakage pathway. Corrosion or degradation can occur anywhere along the wellbore through or along the cement, casing, tubing, or plugs and is a challenging issue facing the oil and gas industry. Two case studies presented here are legacy wells in the Weyburn oil field with substantially different CO 2 injection rates. These case studies aim to help understand casing corrosion in CO 2 -rich environments.

Many depleted oil and gas reservoirs are targets for CO2 enhanced oil recovery, resulting in CO2 storage as part of the commercial enhanced oil recovery process. These oil fields have legacy wellbores that may contain a leakage pathway. Corrosion or degradation can occur anywhere along the wellbore through or along the cement, casing, tubing, or plugs and is a challenging issue facing the oil and gas industry. Two case studies presented here evaluate legacy wells in the Weyburn oil field. One well has injected over 263 million cubic meters of CO2, and the second well has not been exposed to CO2. These case studies aim to help understand casing corrosion in CO2-rich environments. Both wellbores exhibited signs of corrosion, with corrosion ranging from small pits to complete penetration through the casing. Contributing factors to corrosion in these wells range from exposure to injected fluids, injected CO2, packer placements, formation fluid exposure, and the corrosive environment that is present in the perforated area of the well.

An image-based volumetric equation for estimating the prospective CO2 mass storage resource potential for organic-rich shale formations has been developed using data obtained from advanced image analysis of Bakken Formation shale samples. The equation is a modification of the U.S. Department of Energy (DOE) National Energy Technology Laboratory’s (NETL’s) volumetric equation methodology for estimating the prospective CO2 mass storage resource for shale formations. The current equation enhances DOE’s version by systematically deriving expressions for calculating efficiency factors based on analysis of high-resolution field-emission scanning electron microscopy (FESEM) shale images. FESEM images are used to obtain improved nanoscale porosity estimates for the shale matrix and OM. The calculation of the efficiency factors associated with free-phase storage and CO2 adsorption onto solid surfaces are based on a ratio of connected-to-nonconnected porosity and the newly developed shared border analysis (SBA) method, respectively. The image-based equation described herein is structured so that it can be adapted and applied to other formation types by considering the specific mineralogy or matrix characteristics. Preliminary data used to illustrate the newly developed equation show that the Upper Bakken Shale (UBS) may have a lower prospective CO2 storage resource potential than the Lower Bakken Shale (LBS) by about 65 %. Although these results are neither optimized for each lithofacies nor represent the Bakken formation regional scale, they are encouraging for unfractured shale samples and serve as a useful starting point for future evaluations at the regional scale.

Two new Pt(II) 4,4'-di(5,9-diethyltridecan-7-yl)-2,2'-bipyridine complexes (1 and 2) bearing 9,9-diethyl-2-ethynyl-7-(2-(4-nitrophenyl)ethynyl)-9H-fluorene ligand and N-(4-(2-(9,9-diethyl-7-ethynyl-9H-fluoren-2-yl)ethynyl)phenyl)-N-phenylbenzeneamine ligand, respectively, were synthesized and characterized. Their photophysical properties were investigated systematically by UV-vis absorption, emission, and transient absorption (TA) spectroscopy, and the nonlinear absorption was studied by nonlinear transmission technique. Theoretical TD-DFT calculations using the CAM-B3LYP functional were carried out to determine the nature of the singlet excited electronic states and to assist in the assignment of significant transitions observed in experiments. Complex 1 exhibits an intense, structureless absorption band at ca. 397 nm in CH2Cl2 solution, which is attributed to mixed metal-to-ligand charge transfer ((1)MLCT)/ligand-to-ligand charge transfer ((1)LLCT)/intraligand charge transfer ((1)ILCT)/(1)π,π* transitions, and two (1)MLCT/(1)LLCT transitions in the 300-350 nm spectral region. Complex 2 possesses an intense acetylide ligand localized (1)π,π* absorption band at ca. 373 nm and a moderately intense (1)MLCT/(1)LLCT tail above 425 nm in CH2Cl2. Both complexes are emissive in solution at room temperature, with the emitting state being tentatively assigned to the predominant (3)π,π* state for 1, whereas the emitting state of 2 exhibits a switch from (3)π,π* state in high-polarity solvents to (3)MLCT/(3)LLCT state in low-polarity solvents. Both 1 and 2 exhibit strong singlet excited-state TA in the visible to NIR region, where reverse saturable absorption (RSA) is feasible. The spectroscopic studies and theoretical calculations indicate that the photophysical properties of these Pt complexes can be tuned drastically by extending the π-conjugation of the acetylide ligands. In addition, strong RSA was observed at 532 nm for nanosecond (ns) laser pulses from 1 and 2, demonstrating that the RSA of the Pt(II) diimine complexes can be improved by extending the π-conjugation of the acetylide ligands.

Based on information obtained about the technical aspects of the technologies, several challenges are expected to be faced by any potential CO 2 utilization technologies intended for North Dakota lignite plants. The weather, alkaline content of lignite fly ash, and space limitations in the immediate vicinity of existing power plants are challenging hurdles to overcome. Currently, no CO 2 utilization option is ready for implementation or integration with North Dakota power plants. Mineralization technologies suffer from the lack of a well-defined product and insufficient alkalinity in lignite fly ash. Algae and microalgae technologies are not economically feasible and will have weather- related challenges.

A platinum complex with the 6-(7-benzothiazol-2'-yl-9,9-diethyl-9H-fluoren-2-yl)-2,2'-bipyridinyl ligand (1) was synthesized and the crystal structure was determined. UV/Vis absorption, emission, and transient difference absorption of 1 were systematically investigated. DFT calculations were carried out on 1 to characterize the electronic ground state and aid in the understanding of the nature of low-lying excited electronic states. Complex 1 exhibits intense structured (1)π-π* absorption at λ(abs)440 nm, and a broad, moderate (1)MLCT/(1)LLCT transition at 440-520 nm in CH(2)Cl(2) solution. A structured (3)π-π*/(3)MLCT emission at about 590 nm was observed at room temperature and at 77 K. Complex 1 exhibits both singlet and triplet excited-state absorption from 450 nm to 750 nm, which are tentatively attributed to the (1)π-π* and (3)π-π* excited states of the 6-(7-benzothiazol-2'-yl-9,9-diethyl-9H-fluoren-2-yl)-2,2'-bipyridine ligand, respectively. Z-scan experiments were conducted by using ns and ps pulses at 532 nm, and ps pulses at a variety of visible and near-IR wavelengths. The experimental data were fitted by a five-level model by using the excited-state parameters obtained from the photophysical study to deduce the effective singlet and triplet excited-state absorption cross sections in the visible spectral region and the effective two-photon absorption cross sections in the near-IR region. Our results demonstrate that 1 possesses large ratios of excited-state absorption cross sections relative to that of the ground-state in the visible spectral region; this results in a remarkable degree of reverse saturable absorption from 1 in CH(2)Cl(2) solution illuminated by ns laser pulses at 532 nm. The two-photon absorption cross sections in the near-IR region for 1 are among the largest values reported for platinum complexes. Therefore, 1 is an excellent, broadband, nonlinear absorbing material that exhibits strong reverse saturable absorption in the visible spectral region and large two-photon-assisted excited-state absorption in the near-IR region.

Alzheimer disease elevates lipid peroxidation in the brain and data indicate that the resulting lipid-aldehydes are pathological effectors of lipid peroxidation. The disposition of 4-substituted nonenals derived from arachidonate (20:4, n-6) and linoleate (18:2, n-6) oxidation is modulated by their protein adduction targets, their metabolism, and the nature of the 4-substitutent. Trans-4-oxo-2-nonenal (4-ONE) has a higher toxicity in some systems than the more commonly studied trans-4-hydroxy-2-nonenal (HNE). In this work, we performed a structure-function analysis of 4-hydroxy/oxoalkenal upon mitochondrial endpoints. We tested the hypotheses that 4-ONE, owing to a highly reactive nature, is more toxic than HNE and that HNE toxicity is enantioselective. We chose to study freshly isolated brain mitochondria because of the role of mitochondrial dysfunction in neurodegenerative disorders. Whereas there was little effect related to HNE chirality, our data indicate that in the mitochondrial environment, the order of toxic potency under most conditions was 4-ONE>HNE. 4-ONE uncoupled mitochondrial respiration at a concentration of 5μM and inhibited aldehyde dehydrogenase 2 (ALDH2) activity with an IC(50) of approximately 0.5μM. The efficacy of altering mitochondrial endpoints was ALDH2 inhibition>respiration=mitochondrial swelling=ALDH5A inhibition>GSH depletion. Thiol-based alkenal scavengers, but not amine-based scavengers, were effective in blocking the effects of 4-ONE upon respiration. Quantum mechanical calculations provided insights into the basis for the elevated reactivity of 4-ONE>HNE. Our data demonstrate that 4-ONE is a potent effector of lipid peroxidation in the mitochondrial environment.

Recent advances in the mechanistic understanding of mercury oxidation on a carbon surface in flue gas are reviewed in this paper. Theoretical calculations were performed to determine whether the energetics are feasible for a proposed detailed model for oxidative addition of elemental mercury on a carbon edge structure. The results of the calculation show that mercury complexation with a carbenium ion formed at a zigzag edge carbon has a small positive ΔG, but attack of chloride on the complex will proceed with negative ΔG. The energetics rule out a direct covalent bond formation between mercury and the carbenium ion. Alternative concerted reaction models and double-charged models for the mechanism are also feasible but have not yet been computed.

A series of platinum 4,6-diphenyl-2,2'-bipyridine complexes (6-10) with alkoxyl substituent on the 6-phenyl ring have been synthesized and characterized. The influence of the alkoxyl substituent on the nature of the low-lying excited states, and thus the photophysical properties, have been systematically investigated spectroscopically and theoretically. Complexes 6-10 exhibit a broad low-energy charge-transfer absorption band from 400 to 500 nm, which shows weak negative solvatochromic effect. They all emit at about 590 nm in fluid solutions at room temperature, with the emission energy essentially independent of the nature of the monodentate ligand and the polarity of solvent. The excited-state lifetimes of 6 and 7 are much longer (approximately 460-570 ns) than those of their corresponding "alkoxyl free" analogues 12 and 13 (approximately 40-100 ns) in CH(3)CN. Additionally, the emission quantum yields of 7-9 in CH(2)Cl(2) are quite high (0.15-0.21). Spectroscopic studies and Time-Dependent Density Functional Theory (TDDFT) calculations indicate that these unique photophysical properties are induced by the electron-donating ability of the alkoxyl substituent, which causes a mixture of the intraligand charge transfer (ILCT) with the metal-to-ligand charge transfer (MLCT)/ligand-to-ligand charge transfer (LLCT) in their low-lying excited states. Complexes 6-10 exhibit broad triplet transient difference absorption in the near-UV to the near-IR region, where reverse saturable absorption (RSA) could occur. Nonlinear absorption experiments at 532 nm for nanosecond laser pulses demonstrate that 6-9 are strong reverse saturable absorbers, while 10 exhibits weak RSA because of its larger ground-state absorption cross-section and its low triplet excited-state quantum yield.

Ab initio calculations of the potential energy curve for the dissociation of methane have been performed using second-order generalized Van Vleck multireference perturbation theory (GVVPT2), based on CASSCF reference functions, with the cc-pVDZ and cc-pVTZ basis sets. The results show that the GVVPT2 method provides a correct description of the entire curve, including the region of 2.0–3.0 A, which is known to be problematic even for high-order many-body perturbation theories, including full fourth order. Non-parallelity errors (NPEs) calculated relative to MRCISD show that GVVPT2, MRD-CI extrapolated to full CI, and coupled cluster with iterative triples have curves similar to MRCISD, with NPEs of 4–5 kcal mol−1. The predicted D e of 109.8 kcal mol−1 at the GVVPT2/cc-pVTZ level is in close agreement with that seen at previous high levels of theory, e.g. 109.5 kcal mol−1 at the MRD-CI/6-31G* extrapolated to full CI level and 109.2 kcal mol−1 at the CCSDT-1a/DZP level, and is close to the experimental valu...

The stereochemistry of the OH groups in 17α,20S-dihydroxypregn-4-ene-3, 16-dione 1 (named Turraesterodione) has been predicted by quantum chemical calculations. Turraesterodione is a natural product found in the stem bark of Turraeanthus africanus, which is found in the equatorial rain forest in Africa. The results of our calculations show that the OH groups at centers C17 and C20 are syn-oriented, in support of a recent X-ray analysis that found the OH groups to be on the same side of the molecule. Additionally, another isomer with the two OH groups anti-oriented with respect to the methyl group at C18, as is the orientation in the X-ray structure, was found to be energetically comparable to the X-ray structure. Equilibrium geometries and thermodynamic stabilities of five isomers, including the one found in the X-ray study, have been calculated at the MP2 and B3LYP levels of theory, using the 6-311G** basis set. Harmonic vibrational frequencies have been calculated at the B3LYP/6-311G** level, and the predicted IR spectrum shows very good agreement with experiment.

The Energy & Environmental Research Center (EERC) has been conducting research on gasification for six decades. One of the objectives of this gasification research has been to maximize carbon conversion and the water–gas shift process for optimal hydrogen production and syngas quality. This research focus and experience were a perfect fit for the National Center for Hydrogen Technology ® (NCHT®) Program at the EERC for improving all aspects of coal gasification, which ultimately aids in the production and purification of hydrogen. A consortia project was developed under the NCHT Program to develop an improved predictive model for ash formation and deposition under the project entitled “Coal Ash Behavior in Reducing Environments (CABRE) III: Development of the CABRE III Model.” The computer-based program is now applicable to the modeling of coal and ash behavior in both entrained-flow and fluidized-bed gasification systems to aid in overall gasification efficiency. This model represents a significant improvement over the CABRE II model and runs on a Microsoft Windows PC platform. The major achievements of the CABRE III model are partitioning of inorganic transformations between various phases for specific gas cleanup equipment; slag property predictions, including standard temperature–viscosity curves and slag flow and thickness; deposition ratesmore » in gasification cleanup equipment; provision for composition analysis for all input and output streams across all process equipment, including major elements and trace elements of interest; composition analysis of deposit streams for various deposit zones, including direct condensation on equipment surfaces (Zone A), homogeneous particulate deposition (Zone B), and entrained fly ash deposition (Zone C); and physical removal of ash in cyclones based on D50 cut points. Another new feature of the CABRE III model is a user-friendly interface and detailed reports that are easily exportable into Word documents, Excel spreadsheets, or as pdf files. The user interface provides stepwise guides with built-in checks for efficient entry of required input data on fuels of interest to allow a successful execution of the model. The model was developed with data from several fuels selected by the sponsors, including bituminous coal, subbituminous coal, lignite, and petroleum coke (petcoke). The data from these fuels were obtained using small pilot-scale entrained-flow and fluidized-bed gasifiers at the Energy & Environmental Research Center (EERC). The CABRE III model is expected to further advance the knowledge base for the NCHT® Program and, more importantly, allow for prediction of the slagging and fouling characteristics of fuels in reducing environments. The information obtained from this program will potentially also assist in maintaining prolonged gasifier operation free from failure or facilitate troubleshooting to minimize downtime in the event of a problem.« less

Selenoenzymes are required to prevent and reverse oxidative damage in the brain and neuroendocrine system, but these enzymes are vulnerable to irreversible inhibition by methylmercury (MeHg). Selenoenzyme inhibition appears likely to cause most if not all of the pathological effects of mercury toxicity. This biochemically based understanding seems to explain why certain tissues are affected by mercury, why the latency effect is unique to mercury poisoning, why selenium status is inversely related to mercury toxicity, why fetal exposures are so much more harmful than adult exposures, and why prenatal inhibition of selenoenzymes by high MeHg results in sustained loss of their activities.

Long-term demonstration tests of advanced sorbent enhancement additive (SEA) technologies have been completed at five coal-fired power plants. The targeted removal rate was 90% from baseline conditions at all five stations. The plants included Hawthorn Unit 5, Mill Creek Unit 4, San Miguel Unit 1, Centralia Unit 2, and Hoot Lake Unit 2. The materials tested included powdered activated carbon, treated carbon, scrubber additives, and SEAs. In only one case (San Miguel) was >90% removal not attainable. The reemission of mercury from the scrubber at this facility prevented >90% capture.

Zeolites are an economical mineral used in several applications, primarily as molecular sieves because of their crystalline structure. Southwestern North Dakota has several localities of volcanic ash deposits (tuffs) that have undergone physical and chemical changes forming some zeolites in the process. Of particular interest is the zeolite mineral erionite, but not because of its economic potential. Erionite is highly carcinogenic and was found to be responsible for extremely high mortality rates in two Turkish villages in close proximity to erionite rock and dust. Erionite has traditionally been identified using x-ray diffraction (XRD) methods. The presence of swelling clays can interfere with the identification of erionite by XRD giving false positive results. Scanning electron microscopy (SEM) was used to identify the distinctive needlelike form of erionite. In some cases, erionite was identified using SEM techniques where erionite was present, but in quantities that are lower than the lower detection limits. Conversely, erionite was identified by XRD in some instances where the erionite was somewhat masked in a clay matrix. Both XRD and SEM methods should be used to properly identify erionite. Erionite was identified in sandstones and siltstones from buttes in Dunn, Stark, and Slope Counties of North Dakota, but more » no definitive correlation was noted between these occurrences and health effects that may be attributed to erionite. « less

Platinum terpyridyl (tpy) phenylacetylide complexes with –Cl, –CN, and –NMe2 substituents on the 4′-position of the tpy ligand were synthesized and characterized. Their photophysical properties were systematically investigated. In addition, theoretical electronic structure calculations using density functional theory (DFT) and time-dependent (TD-DFT) approaches were carried out for complexes 3 and 6; the results of these calculations provided additional information on the nature of the electronic structures of the low-lying electronic states of these complexes, including the electron density distribution and the composition of the frontier molecular orbitals. Complexes 4–6 exhibit moderately intense charge-transfer bands in the visible region, which are assigned to the 1MLCT/1LLCT transitions. In comparison to their corresponding chloride complexes 1–3, these charge-transfer bands become broadened and red-shifted. Complexes 4–6 emit at room temperature in CH3CN and CH2Cl2 solutions and at 77 K in butyronitrile glassy solutions. At room temperature, the emission is tentatively attributed to 3MLCT for 4 and 5, and to a mixture of 3MLCT/3ILCT/3π,π* for 6. Due to the admixture of 3ILCT/3π,π* characters in its emitting state, 6 displays a much higher emission quantum yield and longer emission lifetime compared to 4 and 5. Replacing the chloride co-ligand in 1–3 by phenylacetylide co-ligand clearly enhances the emission and prolongs the lifetime. 3–6 exhibit a broad and moderately intense triplet excited-state absorption in the visible to the NIR region, with large excited-state absorption coefficients and moderately high triplet excited state quantum yields. Therefore, complexes 3–6, especially 6, have potential applications in organic light emitting devices (OLED) and as reverse saturable absorbing materials.

The geometries and electronic energies of six singlet carbenes, with methyl and phenyl substituents, and the corresponding carbenium ions were obtained using several density functional theory (DFT) variants and the second-order Møller-Plesset method for electron correlation and compared with G3 results, with the aim to determine a relatively low-cost computational protocol that is sufficiently accurate for the specific molecules and ions of interest. Some additional calculations were performed at the CCSD(T) level. Results for diphenylcarbene, methylphenylcarbene, and their cations, which were not previously investigated by ab initio methods, are reported as are calculations on methylene, methylcarbene, dimethylcarbene, and phenylcarbene. The MPW3LYP/6-311+G(d,p) hybrid DFT level was found to give results that were in close agreement with those obtained using G3 theory, with a mean absolute deviation (MAD) of 1.76 kcal/mol for the calculated proton attachment energies (PAEs). Equilibrium geometries obtained with this method were compared with those obtained at the MP2/6-311G(d,p) level of theory, and bond lengths and bond angles had MADs of 0.005 A and 1.0 degrees, respectively. Harmonic vibrational frequencies of all the carbene molecules and the corresponding ions were computed to verify that the stationary points were true minima, to obtain zero-point corrected energies, to assist in infrared studies of the molecules. The recommended combination of method and basis set is expected to be a useful framework that uses modest amounts of computer resources to obtain usable thermochemical data on moderate-sized hydrocarbons and hydrocarbon cations, including coal-mimetic species.

The characterization and control of emissions from combustion sources are of significant importance in improving local and regional air quality. Such emissions include fine particulate matter, organic carbon compounds, and NO{sub x} and SO{sub 2} gases, along with mercury and other toxic metals. This project involved four activities including Further Development of Analytical Techniques for PM{sub 10} and PM{sub 2.5} Characterization and Source Apportionment and Management, Organic Carbonaceous Particulate and Metal Speciation for Source Apportionment Studies, Quantum Modeling, and High-Potassium Carbon Production with Biomass-Coal Blending. The key accomplishments included the development of improved automated methods to characterize the inorganic and organic components particulate matter. The methods involved the use of scanning electron microscopy and x-ray microanalysis for the inorganic fraction and a combination of extractive methods combined with near-edge x-ray absorption fine structure to characterize the organic fraction. These methods have direction application for source apportionment studies of PM because they provide detailed inorganic analysis along with total organic and elemental carbon (OC/EC) quantification. Quantum modeling using density functional theory (DFT) calculations was used to further elucidate a recently developed mechanistic model for mercury speciation in coal combustion systems and interactions on activated carbon. Reaction energies, enthalpies, free energies andmore » binding energies of Hg species to the prototype molecules were derived from the data obtained in these calculations. Bimolecular rate constants for the various elementary steps in the mechanism have been estimated using the hard-sphere collision theory approximation, and the results seem to indicate that extremely fast kinetics could be involved in these surface reactions. Activated carbon was produced from a blend of lignite coal from the Center Mine in North Dakota and sunflower hulls for the biomass material to be carbonized. The ability to remove mercury from a bituminous coal's derived flue gas was low. Removals of only 15% were attained while injecting 6 lb/Macf of activated carbon upstream of an electrostatic precipitator. Poisoning of sites on the activated carbon by SO{sub 2} and SO{sub 3} contributed to the poor mercury capture performance.« less

Platinum(II) diimine complexes with naphthalimide substituted fluorenylacetylide ligands are synthesized and characterized. The complexes exhibit long-lived (3)ILCT or (3)ILCT/(3)MLCT/(3)LLCT excited states (τ = ~20-30 μs) and broadband triplet transient absorption in the visible-NIR region. Nonlinear transmission experiments at 532 nm demonstrate that these complexes are efficient nonlinear absorbing materials.