10 results on '"Serena K. Stephenson"'
Search Results
2. Extraction of ethanol with higher alcohol solvents and their toxicity to yeast
- Author
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Diana Franqui, Jessica L. Cline, George H. Robertson, Serena K. Stephenson, William J. Orts, and Richard D. Offeman
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Ethanol ,Chromatography ,Aqueous solution ,Extraction (chemistry) ,Filtration and Separation ,Alcohol ,Oleyl alcohol ,Yeast ,Analytical Chemistry ,Solvent ,chemistry.chemical_compound ,chemistry ,Organic chemistry ,Ethanol fuel - Abstract
In a solvent extraction screening study, several β-branched alcohols in the 14–20 carbons range show improved extractive performance to recover ethanol from aqueous solutions compared to commonly studied solvents such as oleyl alcohol and 1-dodecanol. These β-branched alcohols were selected for screening based on extrapolation of results in earlier work with lower molecular weight aliphatic alcohol solvents, that indicated higher separation factors should be realized when hydroxyl position is mid-chain, and there is branching. Solvent toxicity to a commercial yeast commonly used in fuel ethanol production also was evaluated for these as well as several lower molecular weight alcohols. For the alcohols studied, those containing 12 or fewer carbons were toxic or inhibitory to the yeast; those containing 14 or more carbons were non-toxic and non-inhibitory.
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- 2008
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3. Ethanol and water capacities of alcohols: A molecular dynamics study
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William J. Orts, George H. Robertson, Serena K. Stephenson, and Richard D. Offeman
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Ethanol ,Stereochemistry ,Hydrogen bond ,Applied Mathematics ,General Chemical Engineering ,Extraction (chemistry) ,chemistry.chemical_element ,Alcohol ,General Chemistry ,Industrial and Manufacturing Engineering ,Molecular dynamics ,chemistry.chemical_compound ,chemistry ,Liquid–liquid extraction ,Physical chemistry ,Ternary operation ,Carbon - Abstract
The extended hydrogen bond networks formed by alcohols are good indicators of their capacities to hold water. Results from molecular dynamics simulations on 24 linear alcohol isomers containing 6–12 carbon atoms show the effects of hydroxyl location on bulk hydrogenbonded structures. Calculated oxygen–oxygen radial distributions obtained from simulations were correlated to experimental liquid–liquid solvent extraction studies involving ternary water/ethanol/alcohol systems. It was found that hydroxyl group location determines the primary structure of the bulk alcohol’s hydrogen bond network and that an alcohol’s capacity for water correlates directly to the size of this network. 2006 Elsevier Ltd. All rights reserved.
- Published
- 2006
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4. Solvent extraction of ethanol from aqueous solutions using biobased oils, alcohols, and esters
- Author
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William J. Orts, Serena K. Stephenson, Richard D. Offeman, and George H. Robertson
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Chromatography ,Ethanol ,General Chemical Engineering ,Organic Chemistry ,Extraction (chemistry) ,Fatty alcohol ,Alcohol ,Oleyl alcohol ,Solvent ,chemistry.chemical_compound ,Vegetable oil ,chemistry ,Castor oil ,medicine ,Organic chemistry ,medicine.drug - Abstract
Distribution coefficients and separation factors were determined for the partitioning of ethanol and water from aqueous mixtures into several vegetable oils and their fatty alcohol and fatty ester derivatives. Castor oil, ricinoleyl alcohol, and methyl ricinoleate all show higher ethanol distribution coefficients, and similar or reduced separation factors, relative to other oils and derivatives studied here or reported by others. Of particular interest, ricinoleyl alcohol has an ethanol distribution coefficient 50% higher than that of oleyl alcohol, a commonly studied solvent for ethanol extraction from fermentation broths.
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- 2006
- Full Text
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5. Velocity Modulation Spectroscopy of Ions
- Author
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Serena K. Stephenson and Richard J. Saykally
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Velocity modulation ,Chemistry ,Analytical chemistry ,Mineralogy ,General Medicine ,General Chemistry ,Spectroscopy ,Ion - Published
- 2005
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6. Solvent Extraction of Ethanol from Aqueous Solutions. I. Screening Methodology for Solvents
- Author
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Serena K. Stephenson, George H. Robertson, William J. Orts, and Richard D. Offeman
- Subjects
Physics::Biological Physics ,Ethanol ,Aqueous solution ,Chromatography ,General Chemical Engineering ,Extraction (chemistry) ,General Chemistry ,Aqueous ethanol ,Industrial and Manufacturing Engineering ,Condensed Matter::Soft Condensed Matter ,Partition coefficient ,chemistry.chemical_compound ,chemistry ,Screening method ,Fermentation ,Physics::Chemical Physics ,Solvent extraction - Abstract
The evaluation of the potential for separation of aqueous ethanol mixtures by liquid−liquid solvent extraction has been complicated by inconsistent results and differing experimental methodologies among researchers developing distribution coefficient data. A screening method for measuring equilibrium distribution coefficients for solvent extraction of ethanol from dilute aqueous solutions is presented to minimize potential sources of variation. These include entrainment, incomplete equilibration, impurities, and temperature changes during the preparation of samples for analysis. Multiple literature sources of data exist for each of 10 solvents. Results for these 10 solvents are compared among sources and to results generated from this method. The method also has general utility for the screening of solvents for extraction of other useful fermentation products.
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- 2005
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7. Solvent Extraction of Ethanol from Aqueous Solutions. II. Linear, Branched, and Ring-Containing Alcohol Solvents
- Author
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George H. Robertson, William J. Orts, Serena K. Stephenson, and Richard D. Offeman
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Aqueous solution ,Ethanol ,General Chemical Engineering ,Chemical structure ,Alcohol ,General Chemistry ,Branching (polymer chemistry) ,Industrial and Manufacturing Engineering ,chemistry.chemical_compound ,Chain length ,chemistry ,Organic chemistry ,Branch structure ,Solvent extraction - Abstract
Distribution coefficients have been measured for the partitioning of ethanol and water from aqueous mixtures into 57 different alcohol solvents. The study has focused on the effects of systematic variations in chemical structure of the alcohols. Factors found to be important include chain length and hydroxyl position for the x-alcohols (i.e., 1-heptanol through 1-dodecanol, 2-heptanol through 2-undecanol, etc.), branch structure (e.g., methyl, ethyl, n-propyl, i-propyl, etc.) for a branch located on the hydroxyl carbon, location of the branch relative to the hydroxyl carbon, and multiple branching.
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- 2005
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8. Terahertz laser velocity modulation spectroscopy of ions
- Author
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Richard J. Saykally and Serena K. Stephenson
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Velocity modulation ,Materials science ,Nuclear magnetic resonance ,Terahertz radiation ,Far-infrared laser ,Physical and Theoretical Chemistry ,Atomic physics ,Spectroscopy ,Modulation efficiency ,Atomic and Molecular Physics, and Optics ,Doppler broadening ,Ion - Abstract
Velocity modulation spectroscopy has been investigated in the terahertz region, employing pure rotational transitions of ArH + and rotation-tunneling transitions of H3O + to study the competition between pressure broadening and Doppler broadening on the lineshapes, neutral suppression, and modulation efficiency. Velocity modulation is demonstrated to be effective to frequencies as low as 60 cm � 1 , yielding S/N values for ArH + (770/1) that surpass published terahertz FM results by an order
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- 2005
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9. Continuous online Fourier transform infrared (FT-IR) spectrometry analysis of hydrogen chloride (HCl), carbon dioxide (CO2), and water (H2O) in nitrogen-rich and ethylene-rich streams
- Author
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Serena K. Stephenson, Kipchirchir Boit, and Maria Pollard
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Spectrometer ,Absorption spectroscopy ,Continuous operation ,Parts-per notation ,Analytical chemistry ,chemistry.chemical_compound ,symbols.namesake ,Fourier transform ,chemistry ,symbols ,Fourier transform infrared spectroscopy ,Hydrogen chloride ,Absorption (electromagnetic radiation) ,Instrumentation ,Spectroscopy - Abstract
The prevalence of optical spectroscopy techniques being applied to the online analysis of continuous processes has increased in the past couple of decades. The ability to continuously “watch” changing stream compositions as operating conditions change has proven invaluable to pilot and world-scale manufacturing in the chemical and petrochemical industries. Presented here is an application requiring continuous monitoring of parts per million (ppm) by weight levels of hydrogen chloride (HCl), water (H2O), and carbon dioxide (CO2) in two gas-phase streams, one nitrogen-rich and one ethylene-rich. Because ethylene has strong mid-infrared (IR) absorption, building an IR method capable of quantifying HCl, H2O, and CO2 posed some challenges. A long-path (5.11m) Fourier transform infrared (FT-IR) spectrometer was used in the mid-infrared region between 1800 and 5000 cm−1, with a 1 cm−1 resolution and a 10 s spectral update time. Sample cell temperature and pressure were controlled and measured to minimize measurement variability. Models using a modified classical least squares method were developed and validated first in the laboratory and then using the process stream. Analytical models and process sampling conditions were adjusted to minimize interference of ethylene in the ethylene-rich stream. The predictive capabilities of the measurements were ±0.5 ppm for CO2 in either stream; ±1.1 and ±1.3 ppm for H2O in the nitrogen-rich and ethylene-rich streams, respectively; and ±1.0 and ±2.4 ppm for HCl in the nitrogen-rich and ethylene-rich streams, respectively. Continuous operation of the instrument in the process stream was demonstrated using an automated stream switching sample system set to 10 min intervals. Response time for all components of interest was sufficient to acquire representative stream composition data. This setup provides useful insight into the process for troubleshooting and optimizing plant operating conditions.
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- 2013
10. Use of Online Spectroscopy to Control Polymerization in Industrial Processes
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John W. Weston, Rich Harner, Brenda Colegrove, Liane Mikolajczyk, J. D. Tate, Kishori Deshpande, and Serena K. Stephenson
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chemistry.chemical_classification ,Optical fiber ,Polymers and Plastics ,Fouling ,Process (engineering) ,business.industry ,General Chemical Engineering ,Process chemistry ,Analytical chemistry ,02 engineering and technology ,General Chemistry ,Polymer ,021001 nanoscience & nanotechnology ,law.invention ,Chemometrics ,chemistry.chemical_compound ,020401 chemical engineering ,chemistry ,Polymerization ,law ,Polystyrene ,0204 chemical engineering ,0210 nano-technology ,Process engineering ,business - Abstract
Online analyzers enable manufacturers to operate modern polymerization processes as safely, reliably, and profitably as possible. The most critical application of this technology involves monitoring the reactor itself to determine the molecular weight and comonomer content of the polymer produced. Polymer process streams introduce unique challenges for online analyzers because the process chemistry, sample transport, and stream conditions are harsher, prone to fouling, and pose unique safety hazards. Spectroscopy lends itself very well to online analysis of polymers because the data it provides is information rich and can be deployed using fiber optics for remote sampling of gases, liquids, and solids. Additionally, it is relatively fast and reliable if well designed and installed properly. The combination of spectroscopy, fiber optics, and chemometrics gives manufacturers the ability to use modern spectrometers and statistical models to analyze and monitor diverse types of polymerization processes. Several examples are provided in this article, including application to polyethylene, polycarbonate, polyurethane, and polystyrene processes.
- Published
- 2017
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