: The unpolarized absorption and circular dichroism spectra of the fundamental vibrational transitions of the chiral molecule, 4-methyl-2-oxetanone, are calculated ab initio. Harmonic force fields are obtained using Density Functional Theory (DFT), MP2, and SCF methodologies and a 5S4P2D/3S2P (TZ2P) basis set. DFT calculations use the Local Spin Density Approximation (LSDA), BLYP, and Becke3LYP (B3LYP) density functionals. Mid-IR spectra predicted using LSDA, BLYP, and B3LYP force fields are of significantly different quality, the B3LYP force field yielding spectra in clearly superior, and overall excellent, agreement with experiment. The MP2 force field yields spectra in slightly worse agreement with experiment than the B3LYP force field. The SCF force field yields spectra in poor agreement with experiment.The basis set dependence of B3LYP force fields is also explored: the 6-31G* and TZ2P basis sets give very similar results while the 3-21G basis set yields spectra in substantially worse agreements with experiment. jg

Ab initio calculation of vibrational absorption and circular dichroism spectra using density functional force fields

Trends in bioconversion of lignocellulose: Biofuels, platform chemicals & biorefinery concept

Hemicelluloses for fuel ethanol: A review.

Room-temperature ionic liquids (RTILs) are organic salts that are characterized by low melting points. They are considered to possess a homogeneous microscopic structure. We provide the first experimental evidence of the existence of nanoscale heterogeneities in neat liquid and supercooled RTILs, such as 1-alkyl-3-methyl imidazolium-based salts, using X-ray diffraction. These heterogeneities are of the order of a few nanometers and their size is proportional to the alkyl chain length. These results provide strong support to the findings from recent molecular dynamics simulations, which proposed the occurrence of nanostructures in RTILs, as a consequence of alkyl chains segregation. Moreover, our study addresses the issue of the temperature dependence of the heterogeneities size, showing a behavior that resembles the density one only below the glass transition, thus suggesting a complex behavior above this temperature. These results will provide a novel interpretation approach for the unique chemical physi...

Nanoscale Segregation in Room Temperature Ionic Liquids

Energy resources and their utilization intimately relate to sustainable development. In attaining sustainable development, increasing the energy efficiencies of processes utilizing sustainable energy resources plays an important role. The utilization of renewable energy offers a wide range of exceptional benefits. There is also a link between exergy and sustainable development. A sustainable energy system may be regarded as a cost-efficient, reliable, and environmentally friendly energy system that effectively utilizes local resources and networks. Exergy analysis has been widely used in the design, simulation and performance evaluation of energy systems. The present study comprehensively reviews exergetic analysis and performance evaluation of a wide range of renewable energy resources (RERs) for the first time to the best of the author's knowledge. In this regard, general relations (i.e., energy, exergy, entropy and exergy balance equations along with exergy efficiency, exergetic improvement potential rate and some thermodynamic parameters, such as fuel depletion ratio, relative irreversibility, productivity lack and exergetic factor) used in the analysis are presented first. Next, exergetically analyzed and evaluated RERs include (a) solar energy systems; (a1) solar collector applications such as solar water heating systems, solar space heating and cooling, solar refrigeration, solar cookers, industrial process heat, solar desalination systems and solar thermal power plants), (a2) photovoltaics (PVs) and (a3) hybrid (PV/thermal) solar collectors, (b) wind energy systems, (c) geothermal energy systems, (c1) direct utilization (district heating, geothermal or ground-source heat pumps, greenhouses and drying) and (c2) indirect utilization (geothermal power plants), (d) biomass, (e) other renewable energy systems, and (f) country based RERs. Studies conducted on these RERs are then compared with the previously ones in tabulated forms, while the Grassmann (or exergy flow) diagrams, which are a very useful representation of exergy flows and losses, for some RERs are given. Finally, the conclusions are presented. It is expected that this comprehensive study will be very beneficial to everyone involved or interested in the exergetic design, simulation, analysis and performance assessment of RERs.

A key review on exergetic analysis and assessment of renewable energy resources for a sustainable future

Thermodynamic functions for 1-butyl-3-methylimidazolium hexafluorophosphate ([C4mim][PF6]) are reported in a range of temperatures from (5 to 550) K, based on new measurements by calorimetry. Heat capacities of the crystal, glass, and liquid phases for [C4mim][PF6] were measured with a pair of calorimeters. A vacuum-jacketed adiabatic calorimeter was used at temperatures between (5 and 310) K, and a heat bridge-scanning calorimeter was used from (300 to 550) K. With the adiabatic calorimeter, the fusion Tfus = 283.51 K, = 19.60 kJ·mol-1, and the glass transition Tg = 190.6 K were observed. The [C4mim][PF6] test sample was determined to have a mole fraction purity of 0.9956 by a fractional melting analysis. Densities of the liquid were measured in a range of temperatures from (298 to 353) K with a pycnometer equipped with a capillary neck. An unexpected endothermal transition, with a very small enthalpy change of 0.25 J·g-1 (0.071 kJ·mol-1), was observed in a range of temperatures from (394 to 412) K. He...

Thermodynamic Properties of 1-Butyl-3-methylimidazolium Hexafluorophosphate in the Condensed State

Heat capacities of 1-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide [C6mim][NTf2] have been measured with a new adiabatic calorimeter in a range of temperatures of (5 to 370) K. The substance was found to form glass with Tg = 184.3 K and Cs,m = (170.7 ± 2.8) J·K-1·mol-1. At different modes of crystallization [C6mim][NTf2] forms at least three crystals, the heat capacities of which differ up to 2 % in the temperature range of (220 to 250) K but coincide within 0.1 % in the temperature range of (80 to 220) K. Triple-point temperature for all the crystals is T0 = (272.03 ± 0.01) K, but the enthalpies of fusion are somewhat different. Thermodynamic properties for [C6mim][NTf2] are calculated based on the obtained data.

Thermodynamic Properties of [C6mim][NTf2] in the Condensed State

Thermodynamic properties and polymorphism of 1-alkyl-3-methylimidazolium bis(triflamides)

The heat capacities of nine room-temperature ionic liquids (ILs) were measured in an adiabatic calorimeter. The obtained results were compared with the literature data. It was demonstrated that in most works the uncertainty of the heat capacity measurements for ILs is underestimated, and the possible causes of this were discussed. With the use of the set of 19 ILs for which the reliable heat capacity data and the density data are available, it was found that the quotient of heat capacity at constant pressure to volume for these liquids remains constant within ± 5 % at a given temperature and linearly changes with temperature in the temperature range of (258 to 370) K. It was demonstrated that the selection of an IL for technical applications is limited not by its heat capacity but by the other parameters.

Andrey V. Blokhin

Papers

Thermodynamic Properties of 1-Butyl-3-methylimidazolium Hexafluorophosphate in the Condensed State

Thermodynamic Properties of [C6mim][NTf2] in the Condensed State

Thermodynamic properties and polymorphism of 1-alkyl-3-methylimidazolium bis(triflamides)

Heat Capacity of Ionic Liquids: Experimental Determination and Correlations with Molar Volume

Thermodynamic properties of 1-alkyl-3-methylimidazolium bromide ionic liquids