89,743 research outputs found
Comparative Investigation of the High Pressure Autoignition of the Butanol Isomers
Investigation of the autoignition delay of the butanol isomers has been
performed at elevated pressures of 15 bar and 30 bar and low to intermediate
temperatures of 680-860 K. The reactivity of the stoichiometric isomers of
butanol, in terms of inverse ignition delay, was ranked as n-butanol >
sec-butanol ~ iso-butanol > tert-butanol at a compressed pressure of 15 bar but
changed to n-butanol > tert-butanol > sec-butanol > iso-butanol at 30 bar. For
the temperature and pressure conditions in this study, no NTC or two-stage
ignition behavior were observed. However, for both of the compressed pressures
studied in this work, tert-butanol exhibited unique pre-ignition heat release
characteristics. As such, tert-butanol was further studied at two additional
equivalence ratios ( = 0.5 and 2.0) to help determine the cause of the
heat release.Comment: 4 pages, 4 figures, presented at the 2011 Meeting of the Eastern
States Sections of the Combustion Institut
Charged Higgs production with a boson or a top quark
I present theoretical results for charged Higgs production in association
with a boson or a top quark at the LHC. I calculate higher-order threshold
corrections and show that they are very significant. I present detailed results
for total cross sections as well as transverse-momentum and rapidity
distributions for various LHC energies.Comment: 5 pages, 4 figures; presented at the EPS Conference on High Energy
Physics (EPS-HEP2017), Venice, Italy, July 5-12, 201
Low-energy electron scattering from C_4H_9OH isomers
We present differential, integral, and momentum-transfer cross sections for elastic scattering of low-energy electrons by three butanol isomers, isobutanol, t-butanol, and 2-butanol. Our results were calculated with the Schwinger multichannel method in the static-exchange plus polarization approximation for collision energies from 1 to 50 eV. The present results are compared with previous calculations and measurements for the remaining C_4H_9OH isomer, n-butanol [Khakoo et al., Phys. Rev. A 78, 062714 (2008)]. Distinctive behavior is observed in the differential cross sections at collision energies between 5 and 10 eV. In particular, whereas n-butanol exhibits an f-wave scattering pattern, the other isomers exhibit d-wave behavior. A similar pattern is found in the related alkanes when comparing straight-chain versus branched isomers. We discuss the possible connection of this behavior to shape resonances that influence the scattering
Reduced chemistry for butanol isomers at engine-relevant conditions
Butanol has received significant research attention as a second-generation
biofuel in the past few years. In the present study, skeletal mechanisms for
four butanol isomers were generated from two widely accepted, well-validated
detailed chemical kinetic models for the butanol isomers. The detailed models
were reduced using a two-stage approach consisting of the directed relation
graph with error propagation and sensitivity analysis. During the reduction
process, issues were encountered with pressure-dependent reactions formulated
using the logarithmic pressure interpolation approach; these issues are
discussed and recommendations made to avoid ambiguity in its future
implementation in mechanism development. The performance of the skeletal
mechanisms generated here was compared with that of detailed mechanisms in
simulations of autoignition delay times, laminar flame speeds, and perfectly
stirred reactor temperature response curves and extinction residence times,
over a wide range of pressures, temperatures, and equivalence ratios. The
detailed and skeletal mechanisms agreed well, demonstrating the adequacy of the
resulting reduced chemistry for all the butanol isomers in predicting global
combustion phenomena. In addition, the skeletal mechanisms closely predicted
the time-histories of fuel mass fractions in homogeneous compression-ignition
engine simulations. The performance of each butanol isomer was additionally
compared with that of a gasoline surrogate with an antiknock index of 87 in a
homogeneous compression-ignition engine simulation. The gasoline surrogate was
consumed faster than any of the butanol isomers, with tert-butanol exhibiting
the slowest fuel consumption rate. While n-butanol and isobutanol displayed the
most similar consumption profiles relative to the gasoline surrogate, the two
literature chemical kinetic models predicted different orderings.Comment: 39 pages, 16 figures. Supporting information available via
https://doi.org/10.1021/acs.energyfuels.6b0185
Production of butanol by fermentation in the presence of cocultures of clostridium
Sugars are converted to a mixture of solvents including butanol by a fermentation process employing a coculture of microorganisms of the Clostridium genus, one of said microorganisms favoring the production of butyric acid and the other of which converts the butyric acid so produced to butanol. The use of a coculture substantially increases the yield of butanol over that obtained using a culture employing only one microorganism
Adding Salt to an Aqueous Solution of t-Butanol: Is Hydrophobic Association Enhanced or Reduced?
Recent neutron scattering experiments on aqueous salt solutions of
amphiphilic t-butanol by Bowron and Finney [Phys. Rev. Lett. {\bf 89}, 215508
(2002); J. Chem. Phys. {\bf 118}, 8357 (2003)] suggest the formation of
t-butanol pairs, bridged by a chloride ion via
hydrogen-bonds, and leading to a reduced number of intermolecular hydrophobic
butanol-butanol contacts. Here we present a joint experimental/theoretical
study on the same system, using a combination of molecular dynamics simulations
and nuclear magnetic relaxation measurements. Both theory and experiment
clearly support the more intuitive scenario of an enhanced number of
hydrophobic contacts in the presence of the salt, as it would be expected for
purely hydrophobic solutes [J. Phys. Chem. B {\bf 107}, 612 (2003)]. Although
our conclusions arrive at a structurally completely distinct scenario, the
molecular dynamics simulation results are within the experimental errorbars of
the Bowron and Finney work.Comment: 15 pages twocolumn revtex, 11 figure
Coupled oxidationâreduction of butanolâhexanal by resting Rhodococcus erythropolis NCIMB 13064 cells in liquid and gas phases
Rhodococcus erythropolis is a promising Gram-positive bacterium capable of numerous bioconversions including those involving alcohol dehydrogenases (ADHs). In this work, we compared and optimized the redox biocatalytic performances of 1-butanol-grown R. erythropolis NCIMB 13064 cells in aqueous and in non-conventional gas phase using the 1-butanolâhexanal oxidationâreduction as model reaction. Oxidation of 1-butanol to butanal is tightly coupled to the reduction of hexanal to 1-hexanol at the level of a nicotinoproteinâADH-like enzyme. Cell viability is dispensable for reaction. In aqueous batch conditions, fresh and lyophilized cells are efficient redox catalysts (oxidationâreduction rate = 76 micromol minâ1 g cell dry massâ1) being also reactive towards benzyl alcohol, (S)-2-pentanol, and geraniol as reductants. However, butanol hexanal oxidationâreduction is strongly limited by product accumulation and by hexanal toxicity that is amajor factor influencing cell behavior and performance. Reaction rate is maximal at 40 âŠC pH 7.0 in aqueous phase and at 60 âŠC- pH 7.0â9.0 in gas phase. Importantly, lyophilized cells also showed to be promising redox catalysts in the gas phase (at least 65 micromol minâ1 g cell dry massâ1). The system is notably stable for several days at moderate thermodynamic activities of hexanal (0.06â0.12), 1-butanol (0.12) and water (0.7)
Structural and spectroscopic characterisation of C4 oxygenates relevant to structure/activity relationships of the hydrogenation of α,ÎČ-unsaturated carbonyls
In the present work, we have investigated the conformational isomerism and calculated the vibrational spectra of the C4 oxygenates: 3-butyne-2-one, 3-butene-2-one, 2-butanone and 2-butanol using density functional theory. The calculations are validated by comparison to structural data where available and new, experimental inelastic neutron scattering and infrared spectra of the compounds. We find that for 3-butene-2-one and 2-butanol the spectra show clear evidence for the presence of conformational isomerism and this is supported by the calculations. Complete vibrational assignments for all four molecules are provided and this provides the essential information needed to generate structure/activity relationships for the sequential catalytic hydrogenation of 3-butyne-2-one to 2-butanol
Heterogeneous photocatalytic oxidation of atmospheric trace contaminants
The following subject areas are covered: (1) design and construction of continuous flow photoreactor for study of oxidation of trace atmospheric contaminants; (2) establishment of kinetics of acetone oxidation including adsorption equilibration, variation of oxidation rate with acetone concentration and water (inhibitor), and variation of rate and apparent quantum yield with light intensity; (3) exploration of kinetics of butanol oxidation, including rate variation with concentration of butanol, and lack of inhibition by water; and (4) exploration of kinetics of catalyst deactivation during oxidation of butanol, including deactivation rate, influence of dark conditions, and establishment of photocatalytic regeneration of activity in alcohol-free air
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