Experimentation and thermodynamic representations of binaries containing compounds of low boiling points: pentane and alkyl methanoates

[EN]This work presents experimental mixing properties, hEand vE, at several temperatures and the iso-baric vapor–liquid equilibria (iso-p VLE) at 101.32 kPa for four binaries containing pentane and four alkyl(methyl to butyl) methanoates. Particular conditions are established to work with these solutions withhighly volatile compounds, especially for the case of methyl methanoate + pentane system, for whicha continuous feeding device is designed and constructed for measuring the densities.

A Simple Method to Evaluate, Correlate and Predict Boiling and Flash Points of Alkynes

Boiling points (T-B) of acyclic alkynes are predicted from their boiling point numbers (Y-BP) with the relationship T-B(K) = -16.802Y(BP)(2/3) + 337.377Y(BP)(1/3) - 437.883. In turn, Y-BP values are calculated from structure using the equation Y-BP = 1.726 + A(i) + 2.779C + 1.716M(3) + 1.564M + 4.204E(3) + 3.905E + 5.007P - 0.329D + 0.241G + 0.479V + 0.967T + 0.574S. Here A(i) depends on the substitution pattern of the alkyne and the remainder of the equation is the same as that reported earlier for alkanes. For a data set consisting of 76 acyclic alkynes, the correlation of predicted and literature T-B values had an average absolute deviation of 1.46 K, and the R-2 of the correlation was 0.999. In addition, the calculated Y-BP values can be used to predict the flash points of alkynes.

A simple method to evaluate, correlate and predict boiling and flash points of alkynes

Boiling points (T B) of acyclic alkynes are predicted from their boiling point numbers (Y BP) with the relationship T B(K) = -16.802Y BP2/3 + 337.377Y BP1/3 - 437.883. In turn, Y BP values are calculated from structure using the equation Y BP = 1.726 + Ai + 2.779C + 1.716M3 + 1.564M + 4.204E3 + 3.905E + 5.007P - 0.329D + 0.241G + 0.479V + 0.967T + 0.574S. Here Ai depends on the substitution pattern of the alkyne and the remainder of the equation is the same as that reported earlier for alkanes. For a data set consisting of 76 acyclic alkynes, the correlation of predicted and literature T B values had an average absolute deviation of 1.46 K, and the R² of the correlation was 0.999. In addition, the calculated Y BP values can be used to predict the flash points of alkynes.

Calculating Flash Point Numbers from Molecular Structure: An Improved Method for Predicting the Flash Points of Acyclic Alkanes

We report a novel method for calculating flash points of acyclic alkanes from flash point numbers, N(FP), which can be calculated from experimental or calculated boiling point numbers (Y(BP)) with the equation N(FP) = 1.020Y(BP) - 1.083 Flash points (FP) are then determined from the relationship FP(K) = 23.369N(FP)(2/3) + 20.010N(FP)(1/3) + 31.901 For it data set of 102 linear and branched alkanes, the correlation of literature and predicted flash points has R(2) = 0.985 and an average absolute deviation of 3.38 K. N(FP) values can also be estimated directly from molecular structure to produce an even closer correspondence of literature and predicted FP values. Furthermore, N(FP) values provide a new method to evaluate the reliability of literature flash point data.

Simple Method to Evaluate and to Predict Flash Points of Organic Compounds

Flash points (T(FP)) of organic compounds are calculated from their flash point numbers, N(FP), with the relationship T(FP) = 23.369N(FP)(2/3) + 20.010N(FP)(1/3) + 31.901. In turn, the N(FP) values can be predicted from boiling point numbers (Y(BP)) and functional group counts with the equation N(FP) = 0.974Y(BP) + Sigma(i)n(i)G(i) + 0.095 where G(i) is a functional group-specific contribution to the value of N(FP) and n(i) is the number of such functional groups in the structure. For a data set consisting of 1000 diverse organic compounds, the average absolute deviation between reported and predicted flash points was less than 2.5 K.

Candidate radial-inflow turbines and high-density working fluids for geothermal power systems

Optimisation of Organic Rankine Cycles (ORCs) for binary-cycle geothermal applications could play a major role in the competitiveness of low to moderate temperature geothermal resources. Part of this optimisation process is matching cycles to a given resource such that power output can be maximised. Two major and largely interrelated components of the cycle are the working fluid and the turbine. Both components need careful consideration. Due to the temperature differences in geothermal resources a one-size-fits-all approach to surface power infrastructure is not appropriate. Furthermore, the traditional use of steam as a working fluid does not seem practical due to the low temperatures of many resources. A variety of organic fluids with low boiling points may be utilised as ORC working fluids in binary power cycle loops. Due to differences in thermodynamic properties, certain fluids are able to extract more heat from a given resource than others over certain temperature and pressure ranges. This enables the tailoring of power cycle infrastructure to best match the geothermal resource through careful selection of the working fluid and turbine design optimisation to yield the optimum overall cycle performance. This paper presents the rationale for the use of radial-inflow turbines for ORC applications and the preliminary design of several radial-inflow turbines based on a selection of promising ORC cycles using five different high-density working fluids: R134a, R143a, R236fa, R245fa and n-Pentane at sub- or trans-critical conditions. Numerous studies published compare a variety of working fluids for various ORC configurations. However, there is little information specifically pertaining to the design and implementation of ORCs using realistic radial turbine designs in terms of pressure ratios, inlet pressure, rotor size and rotational speed. Preliminary 1D analysis leads to the generation of turbine designs for the various cycles with similar efficiencies (77%) but large differences in dimensions (139289 mm rotor diameter). The highest performing cycle (R134a) was found to produce 33% more net power from a 150°C resource flowing at 10 kg/s than the lowest performing cycle (n-Pentane).

Near infrared spectroscopy as a rapid tool to measure volatile aroma compounds in Riesling wine: Possibilities and limits

Volatile chemical compounds responsible for the aroma of wine are derived from a number of different biochemical and chemical pathways. These chemical compounds are formed during grape berry metabolism, crushing of the berries, fermentation processes (i.e. yeast and malolactic bacteria) and also from the ageing and storage of wine. Not surprisingly, there are a large number of chemical classes of compounds found in wine which are present at varying concentrations (ng L-1 to mg L-1), exhibit differing potencies, and have a broad range of volatilities and boiling points. The aim of this work was to investigate the potential use of near infrared (NIR) spectroscopy combined with chemometrics as a rapid and low-cost technique to measure volatile compounds in Riesling wines. Samples of commercial Riesling wine were analyzed using an NIR instrument and volatile compounds by gas chromatography (GC) coupled with selected ion monitoring mass spectrometry. Correlation between the NIR and GC data were developed using partial least-squares (PLS) regression with full cross validation (leave one out). Coefficients of determination in cross validation (R 2) and the standard error in cross validation (SECV) were 0.74 (SECV: 313.6 μg L−1) for esters, 0.90 (SECV: 20.9 μg L−1) for monoterpenes and 0.80 (SECV: 1658 ?g L-1) for short-chain fatty acids. This study has shown that volatile chemical compounds present in wine can be measured by NIR spectroscopy. Further development with larger data sets will be required to test the predictive ability of the NIR calibration models developed.

Vapor pressure of liquid metals and alloys

The Gibbs-Bogoliubov formalism in conjunction with the pseudopotential theory is applied to the calculation of the vapour pressure of eight liquid metals from Groups I to IV of the periodic table and of alloys (Na-K). The calculated vapour pressure of the elements and their temperature dependencies, the partial pressures, activities and boiling points of the alloys are all found to be in reasonable agreement with measured data.

Liquid fuel visualization using laser-induced fluoresence during cold start

The presence of liquid fuel inside the engine cylinder is believed to be a strong contributor to the high levels of hydrocarbon emissions from spark ignition (SI) engines during the warm-up period. Quantifying and determining the fate of the liquid fuel that enters the cylinder is the first step in understanding the process of emissions formation. This work uses planar laser induced fluorescence (PLIF) to visualize the liquid fuel present in the cylinder. The fluorescing compounds in indolene, and mixtures of iso-octane with dopants of different boiling points (acetone and 3-pentanone) were used to trace the behavior of different volatility components. Images were taken of three different planes through the engine intersecting the intake valve region. A closed valve fuel injection strategy was used, as this is the strategy most commonly used in practice. Background subtraction and masking were both performed to reduce the effect of any spurious fluorescence. The images were analyzed on both a time and crank angle (CA) basis, showing the time of maximum liquid fuel present in the cylinder and the effect of engine events on the inflow of liquid fuel. The results show details of the liquid fuel distribution as it enters the engine as a function of crankangle degree, volatility and location in the cylinder. A. semi-quantitative analysis based on the integration of the image intensities provides additional information on the temporal distribution of the liquid fuel flow. © 1998 Society of Automotive Engineers, Inc.

Separation of ethyl acetate-ethanol azeotropic mixture using hydrophilic ionic liquids

The separation of ethyl acetate and ethanol (EtOH) is important but difficult due to their close boiling points and formation of an azeotropic mixture. The separation of the azeotropic mixture of ethyl acetate and EtOH using the hydrophilic ionic liquids (ILs) 1-alkyl-3-methylimidazolium chloride (alkyl = butyl, hexyl, and octyl) ([C(n)mim]Cl, n = 4, 6, 8) and 1-allyl-3-methylimidazolium chloride and bromide ([Amim]Cl and [Amim]Br) has been investigated. Triangle phase diagrams of five ILs with ethyl acetate and EtOH were constructed, and the biphasic regions were found as follows: [Amim]Cl > [Amim]Br > [C(4)mim]Cl > [C(6)mim]Cl > [C(8)mim]Cl. The mechanisms of the ILs including cation, anion, and polarity effect were discussed.

Study on QSPR of alcohols with a novel edge connectivity index F-m

A novel edge degree f(i) for heteroatom and multiple bonds in molecular graph is derived on the basis of the edge degree delta(e(r)). A novel edge connectivity index F-m is introduced. The multiple linear regression by using the edge connectivity index F-m and alcohol-type parameter delta, alcohol-distance parameter L can provide high-quality QSPR models for the normal boiling points (BPs), molar volumes (MVs), molar refraction (MRs), water solubility(log(1/S)) and octanol/water partition (logP) of alcohols with up to 17 non-hydrogen atoms. The results imply that these physical properties may be expressed as a liner combination of the edge connectivity index and alcohol-type parameter, 6, alcohol-distance parameter, L. For the models of the five properties, the correlation coefficient r and the standard errors are 0.9969,3.022; 0.9993, 1.504; 0.9992, 0.446; 0.9924,0.129 and 0.9973,0.123 for BPs, MVs, MRs, log(1/S) and logP, respectively. The cross-validation by using the leave-one-out method demonstrates the models to be highly reliable from the point of view of statistics.

Predicted properties of the superheavy elements. III. Element 115, Eka-Bismuth

Element 115 is expected to be in group V-a of the periodic table and have most stable oxidation states of I and III. The oxidation state of I, which plays a minor role in bismuth chemistry, should be a major factor in 115 chemistry. This change will arise because of the large relativistic splitting of the spherically symmetric 7p_l/2 shell from the 7P_3/2 shell. Element 115 will therefore have a single 7p_3/2 electron outside a 7p^2_1/2 closed shell. The magnitude of the first ionization energy and ionic radius suggest a chemistry similar to Tl^+. Similar considerations suggest that 115^3+ will have a chemistry similar to Bi^3+. Hydrolysis will therefore be easy and relatively strongly complexing anions of strong acids will be needed in general to effect studies of complexation chemistry. Some other properties of 115 predicted are as follows: ionization potentials I 5.2 eV, II 18.1 eV, III 27.4 eV, IV 48.5 eV, 0 \rightarrow 5^+ 159 eV; heat of sublimation, 34 kcal (g-atom)^-1; atomic radius, 2.0 A; ionic radius, 115^+ 1.5 A, 115^3+ 1.0 A; entropy, 16 cal deg^-1 (g-atom)^-l (25°); standard electrode potential 115^+ |115, -1.5 V; melting and boiling points are similar to element 113.

Obtenção de pós de tântalo metálico a partir da redução aluminotérmica com ignição a plasma

Metallic tantalum has a high commercial value due to intrinsic properties like excellent ductility, corrosion resistance, high melt and boiling points and good electrical and thermal conductivities. Nowadays, it is mostly used in the manufacture of capacitors, due to excellent dielectric properties of its oxides. In the nature, tantalum occurs in the form of oxide and it is extracted mainly from tantalite-columbite ores. The tantalum is usually produced by the reduction of its oxide, using reductants like carbon, silicon, calcium, magnesium and aluminum. Among these techniques, the aluminothermic reduction has been used as the industrial method to produce niobium, tantalum and their alloys, due to the easy removal of the Al and Al2O3 of the system, easing further refining. In conventional aluminothermic reduction an electrical resistance is used to trigger the reaction. This reaction self-propagates for all the volume of material. In this work, we have developed a novel technique of aluminothermic reduction that uses the hydrogen plasma to trigger the reaction. The results obtained by XRD, SEM and EDS show that is possible to obtain a compound rich in tantalum through this technique of aluminothermic reduction in the plasma reactor

Determinação de benzeno, tolueno, etilbenzeno e xilenos em gasolina comercializada nos postos do estado do Piauí

Automotive gasoline consists of a complex mixture of flammable and volatile hydrocarbons derived from crude oil with carbon numbers within the range of 4-12 and boiling points range of 30-225 ºC. Its composition varies with the kind of crude oil and the type of refinery process that they undergone. Aromatics hydrocarbons, in particular benzene, toluene, ethylbenzene and isomeric xylenes (BTEX) are the toxic group constituents presents. GC-FID was employed to quantify these hydrocarbons in 50 commercial gasoline samples from Piauí state. Statistical analysis techniques, such as PCA and HCA were used to analyze the data. Moreover, several validation parameters were evaluated.

Destilação fracionada do óleo essencial de P. aduncum L. rico em dilapiol

A espécie Piper aduncum L. é uma planta de porte arbustivo, popularmente conhecida na região amazônica como pimenta-de-macaco. Dela, pode ser extraído um óleo essencial, rico em dilapiol, de grande interesse econômico pela sua ação inseticida e combate às pragas na agricultura. Esse bioinseticida surge como alternativa para substituir os inseticidas sintéticos, pois sendo de origem natural não causam danos ao meio ambiente e à saúde do homem. Neste trabalho, foram analisadas as propriedades físicas do óleo essencial de pimenta-de-macaco, obtido por destilação por arraste com vapor que apresentou valores médios do índice de refração igual a 1,516 e massa específica igual a 1,08 g/cm³. Estudou-se o processo de destilação fracionada do óleo essencial, visando concentrar o composto de interesse agregando maior valor econômico, o que viabiliza seu emprego na produção de novos produtos. Nesse processo o composto principal é obtido com elevado grau de pureza. Avaliou-se um modelo matemático para a concentração de dilapiol no fundo do balão de destilação, via análise de regressão, em função do tempo de operação, o qual ajustou muito bem os dados experimentais. A análise dos resultados permite afirmar que o processo de destilação fracionada pode ser empregado para separar os constituintes úteis de óleos essenciais. Isso só é possível, pois os óleos essenciais são constituídos por vários compostos orgânicos voláteis de pontos de ebulição e pressões de vapor diferentes, tornando a separação viável. O maior teor de dilapiol obtido experimentalmente pelo processo de destilação fracionada a vácuo foi de 95 %, operando-se nas condições de vácuo (40 mmHg) e temperatura média da coluna de 122 ºC, obtendo-se um rendimento médio do processo de 41 % (v/v).