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This study focuses on the mineral carbonation to capture CO2 using an alkaline industrial waste, the grits, formed during the kraft pulp production process. An indirect mineral carbonation route was adopted, composed by two steps: first the extraction of calcium from the grits and second the precipitation of calcium carbonate. Firstly, four solvents were analyzed (HNO3, CH3COOH, NaOH and NH4Cl). Only HNO3 and CH3COOH have shown significant extraction efficiencies of 79.4 and 73.2 %, respectively, after 2 h at 30 °C. Kinetic tests demonstrated that equilibrium conditions are reached after 60 min. Since the nitric acid is a corrosive acid and with high associated costs, the acetic acid was selected for the dissolution of grits and extraction of calcium. The optimal conditions determined were an acetic acid concentration of 2 M, solid/liquid ratio of 30 g/L and temperature of 45 °C with an efficiency approximately of 77 %. In the second step, carbonation experiments were performed contacting the Ca-rich liquor, obtained from the extraction step, with a flux of pure CO2 gaseous in a stainless inox reactor. The optimal conditions determined were 30 °C and 30 bar, reaching a carbonation efficiency of 74 %, corresponding a CO2 sequestration capacity of 460 kg CO2/ton of grits.

Syngas production has been investigated via oxidative steam reforming of concentrated glycerol aqueous solutions (Steam-to-Carbon molar ratio = 4 and 6 vol% O2 in N2). Results obtained using different (bulk) bed materials (SiO2, SiC and γ-Al2O3) were compared with results achieved while using a cobalt aluminate catalyst prepared by coprecipitation dispersed in each of those same bed fillers. The effects on conversion and gas production of the filler bed material, activation temperature (1023 K, 1073 K and 1123 K) and reaction temperature (823 K, 923 K and 1023 K) were studied, as well as the catalyst reuse (at 1023 K) to assess its performance after regeneration. High glycerol conversion levels (above 80%) were attained at 1023 K without the catalyst. The main gaseous products were H2, CO, CO2 and CH4. Using a bed of commercial γ-Al2O3, around 90% of the C fed into the reactor could be converted into gaseous products, yielding syngas with H2/CO molar ratio close to 1. In what concerns the use of the Co aluminate catalyst in the oxidative steam reforming of glycerol, very high overall conversion levels (above 90% in all cases) were achieved, as well as significantly higher H2/CO molar ratios (within the 2.0–2.5 range). The Co catalyst helped in effectively converting approximately 90% of the glycerol in the feed into product gases at temperatures as low as 823 K, and up to 94% of overall C conversion to gas could be achieved at 1023 K. Higher activation or reforming reaction temperatures did not improve the catalyst performance, the glycerol conversion or gas production. The catalyst could be effectively used during 20 h on stream in four consecutive reaction/regeneration cycles. Catalyst deactivation by encapsulating carbon caused drastic changes in the catalyst structure, which evolved into a core-shell configuration when deactivated. Upon regeneration by air oxidation and subsequent activation, the catalyst recovered its original structure and initial activity. These new insights allowed to propose the use of a pre-reforming step over relatively inexpensive bulk bed materials, where thermal decomposition of glycerol processes dominate followed by the catalytic oxidative steam reforming, to obtain high syngas production at moderate conditions (823 K).

This review article presents the state-of-the-art on the catalytic oxidative steam reforming (OSR) of glycerol to produce syngas. Concerning the different technologies proposed for the catalytic OSR of glycerol, the following key points can be highlighted: (1) the robustness is much higher than other reforming technologies, (2) several catalysts can work with low deactivation, some of which can recover almost full activity by suitable regeneration, (3) syngas production by catalytic OSR of glycerin is higher than with concurrent technologies, (4) their scaling-up remains an unrealized task, (5) the thermodynamics of the process has been sufficiently covered in the literature, (6) there is a significant lack of kinetic and mechanistic studies that could help gaining deeper insight on the process, (7) novel concepts and reactor designs must be proposed for their development at larger scales, (8) new catalyst formulations must be developed for attaining higher resistance against oxidation and (9) process intensification could help developing them at larger scales. António Portugal and Rui Moreira are grateful to the Portuguese Foundation for Science and Technology (FCT) and the European Development Regional Fund (ERDF) for funding under the scope of the MultiBiorefinery project (POCI-01-0145-FEDER-016403). Luis M. Gandía thanks Banco de Santander and Universidad Pública de Navarra for their financial support under the 'Programa de Intensificación de la Investigación 2018' initiative. Fernando Bimbela and Luis M. Gandía wish to thank financial support from Spanish Ministerio de Ciencia, Innovación y Universidades , and the European Regional Development Fund ( ERDF / FEDER ) (grant RTI2018-096294-B-C31). José Luis Sánchez expresses his gratitude to Aragón Government (Ref. T22_20R), co-funded by FEDER 2014–2020 'Construyendo Europa desde Aragón' for providing frame support for this work.

The cottonseed oil (CSO) extraction and processing areas including biodiesel (CSB) production created the need for density availability over wide ranges of temperature and pressure. In this work, densities of CSO and CSB were measured. The measurement of CSO density under pressure has never been reported in the literature. To address this limitation, this work reports new experimental data of densities of CSO measured at temperatures from 278 to 358 K and pressures from atmospheric up to 30 MPa using a vibrating tube densimeter. The measured densities of CSO were correlated with the Goharshadi–Morsali–Abbaspour equation of state (GMA EoS) with an absolute average relative deviation of 0.02%. The coefficients of GMA EoS for CSO and CSB were used to calculate the thermal expansivity and isothermal compressibility which influence power and fuel injection and they are rarely presented for vegetable oils and biodiesel, especially at high pressures. The group contribution method GCVOL, Halvorsen model, and Zong...

A recent study published by the authors, where correlation methods are proposed to reproduce the density, vapour pressure, and viscosity of glycerol over wide ranges of temperature and pressure, here we present a similar methodology that was applied to the speed of sound in liquid glycerol. The speed of sound in liquid glycerol was calculated from the propagation time measured by using two 5 MHz ultrasonic transducers in through transmission mode, up to 20 MPa and at temperatures ranging from (303.15 to 373.15) K. The density, isothermal compressibility, and isobaric heat capacity were evaluated in the temperature range (298.15 to 348.15) K and pressures up to 100 MPa, from the measured speed of sound starting from the density and specific heat capacity data at 0.1 MPa available in literature, and using a computational method originally developed by Davis and Gordon. The derived density and speed of sound data made the molar compressibility calculation possible, from which a new method was developed for the speed of sound estimation for pressures up to 100 MPa. The proposed method provided speed of sound with high accuracy (AARD% = 0.2%).

The dynamic viscosities of glycerol were measured over the temperature range (293–394) K and atmospheric pressure using a Brookfield thermosel system. The combined expanded uncertainty of reported viscosity is better than 3.0% with a level of confidence 0.95 (k = 2). The presented results are in good agreement with most values from the literature. An extensive viscosity database for this substance was developed combining the values of this work with those published in literature covering a wide range of temperatures at atmospheric pressure from the calculated glass transition temperature (Tg = 188 K), and measurements of viscosity reported over the temperature range (263–398) K at pressures from (10−4 to 3) GPa. The main purpose of database construction was the development and evaluation of reliable correlation models of viscosity valid in wide ranges of temperature and pressure. The physically sound equations of Mauro (MYEGA) and the Bond Strength-Coordination Number Fluctuation (BSCNF) model were used to correlate values selected from the database. From BSCNF the structural effects taking place near the glass transition were discussed in light of results obtained by recent experimental techniques. Some of the tested equations give overall absolute deviations less than 6% in the range (190–440) K, a value which is close the experimental uncertainty. Stickel derivatives were calculated for the correlation equations and they were compared with values found from viscosity data using numerical techniques. High-pressure viscosity data allowed studying the temperature, pressure and density dependences of this property using the free volume theory and the thermodynamic scaling of viscosity. The free volume proved to be more accurate in the calculation of viscosity in wide T and p ranges with average absolute percentual deviations (AADs) ranging from 4% to 14% for data from different authors. The pressure dependence of glass transition temperature and fragility index of glycerol were calculated from model equations being the results in good agreement with data selected from the literature.

This work is inserted in a research program that consists mainly in the experimental and theoretical study of gas/liquid solubility in ionic liquids (ILs). In this study the experimental data of hydrogen sulfide solubility in ammonium-based ionic liquids, namely 2-hydroxyethylammonium acetate [2-HEA][Ace], bis(2-hydroxyethyl)ammonium acetate [B-2-HEA][Ace] and 2-hydroxyethyldiethylammonium hydrogen diacetate [2-HEDEA][H(Ace)2], were determined using a volumetric method in the 298 K to 318 K temperature range and at atmospheric pressure. The ionic liquids are functionalized with the OH group in the ammonium-based cations, in order to study the influence of hydroxyl group in the formation of hydrogen bonds between the IL-IL and IL-gas. The data gathered is modelled with the Cubic Plus Association Equation of State (CPA EoS), considering the association schemes four-sites (4C) for hydrogen sulfide and two-sites (2B) for the ILs ([2-HEA][Ace], [B-2-HEA][Ace] and [2-HEDEA][H(Ace)2]).

Fuel viscosity is an important property that has a significant effect in fuel injection, spray development and combustion in Compression Ignition (CI) engines. Current and future injector designs of diesel engines (such as rail injection systems) work at high pressures (>100 MPa), meaning that fuel viscosity increases substantially over the atmospheric values. The estimation of biodiesel (BD) viscosity based on the knowledge of its composition would be of great potential in the optimization of biodiesel production processes, particularly in the blending of raw materials and refined products. In this work, comprehensive data sets were chosen from literature regarding several BD classes, in order to establish new correlations and new predictive methods of viscosity. The proposed methodologies were validated using available viscosity data of BDs having different chemical compositions in wide ranges of temperature and pressure. The new methods developed at atmospheric pressure for predicting BD viscosity were found to have better predictive ability than those commonly used in literature. In particular, the models developed with the Lewis and Squires equation fitted to biodiesel feedstock (LSDB model) and the same equation using the predicted degree of unsaturation (DU) (LSDU1 model) presented a very good performance with average relative deviation (ARD)

In spite of the importance of glycerol in industry, only limited consistent information on its pVT data seems to be available in the literature. In this work, the density of glycerol (1,2,3-propanetriol) was measured within the temperature range 298.15–348.15 K and over the pressure range from atmospheric pressure up to 25.0 MPa by means of a vibrating tube densimeter. The estimated combined standard uncertainty of measurements is 0.86 kg m3 . The experimental pVT values of this study combined with selected values from the literature covering the ranges of T = (278–373) K and of p = (0.1–200) MPa were fitted using the Goharshadi–Morsali–Abbaspour equation of state (GMA EoS). The measured density in this work correlates with deviations of ±0.05% (less than 0.5 kg m3 ) and in the range ±0.1% with the overall results. From the GMA EoS, the mechanical coefficients as thermal expansivity, isothermal compressibility and internal pressure were calculated. Vapour pressures selected from the literature covering the temperature range between the triple point and the normal boiling point were correlated with the Wagner equation. This equation was used in conjunction with the Clapeyron equation to calculate the molar enthalpies of vapourisation from the triple point to the normal boiling point. Fil: Talavera Prieto, Nieves María del Carmen. Universidad de Coimbra; Portugal. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste. Centro de Ecología Aplicada del Litoral. Universidad Nacional del Nordeste. Centro de Ecología Aplicada del Litoral; Argentina Fil: Souza, Thiago A.. Universidade Federal Rural Do Rio de Janeiro; Brasil Fil: Egas, Ana P.. Universidad de Coimbra; Portugal Fil: Ferreira, Abel G. M.. Universidad de Coimbra; Portugal Fil: Lobo, Lélio Q.. Universidad de Coimbra; Portugal Fil: Portugal, Antonio T. G.. Universidad de Coimbra; Portugal

The main route for industrial production of biodiesel is through the transesterification reaction of different source of triglycerides. Continuous monitoring of the process is very important in order to optimize operational parameters, foresee troubles and guarantee the quality of final product. In this work, the transesterification of cottonseed oil at 50 °C and 70 °C, with methanol/oil molar ratios of 4.5, 6.0 and 7.5 was carried out, and the oil conversion as a function of reaction time was evaluated by 1H NMR. The density of the reaction mixture, at these experimental conditions, was measured as a function of the reaction time by an off-line methodology. From the density-time and oil conversion-time profiles an operative relationship between conversion, density, alcohol to oil ratio and temperature was established.

The knowledge of biodiesel density over large ranges of temperature and pressure is important for predicting the behavior of fuel injection and combustion systems in diesel engines, and for the optimization of such systems. In this study, cottonseed oil was transesterified into biodiesel and its density was measured at temperatures between 288 K and 358 K and pressures between 0.1 MPa and 30 MPa, with expanded uncertainty estimated as ±1.6 kg m−3. Experimental pressure–volume–temperature (pVT) cottonseed data was used along with literature data relative to other 18 biodiesels, in order to build a database used to test the correlation of density with temperarure and pressure using the Goharshadi–Morsali–Abbaspour equation of state (GMA EoS). To our knowledge, this is the first that density measurements are presented for cottonseed biodiesel under such high pressures, and the GMA EoS used to model biodiesel density. The new tested EoS allowed correlations within 0.2 kg m−3 corresponding to average relative deviations within 0.02%. From these results of correlation with the GMA EoS mechanical coefficients such as thermal expansivity, isothermal compressibility and internal pressure were calculated. In spite of their effect in power and fuel injection, those properties are rarely presented for biodiesel, especially at high pressures. As a remarkable result of this study, it was found a crossing point for the thermal expansivity, where isothermic curves cross. The built database was used to develop and test two new full predictive models valid up to 373 K and 130 MPa. One of the proposed predictive methods (4PGMA) followed from the GMA EoS, and the other (DU) was derived from the observed linear relation between density and degree of unsaturation (DU), which depended from biodiesel FAMEs profile. The average density deviation of 4PGMA was only about 2 kg m−3, and 3 kg m−3 for the DU method within the temperature and pressure limits of application. These results represent appreciable improvements in the context of density prediction at high pressure when compared with other equations of state.

In this work, experimental values of gas solubility of hydrofluorocarbons (CHF 3 , CH 2 F 2 and CH 3 F) in three room-temperature ionic liquids (RTILs) were determined within the temperature range 288 K to 308 K and at atmospheric pressure. The RTILs used were trihexyltetradecylphosphonium chloride ([P 6,6,6,14 ][Cl]), tributyl(methyl)phosphonium methylsulfate ([P 4,4,4,1 ][C 1 SO 4 ]), and tributyl(ethyl)phosphonium diethylphosphate ([P 4,4,4,2 ][(C 2 ) 2 PO 4 ]). The data gathered have been modelled using two approaches: the Cubic plus Association equation of state (CPA EoS) and the regular-solution theory (RST). The experimental measurements were then discussed critically and the modelling results compared.

New shape-memory materials (SMMs) for applications in active control and morphing structures have been attracting special attention due to its unique properties. These SMM can be metallic alloys (SMAs), piezoelectric, and polymers such as polyurethanes (SMPUs). The latter detain higher recovery rates but better processability, however, the reaction time is longer when compared with the SMA. The addition of carbon nanotubes (CNTs) to SMPU seems to improve its overall properties with a great deal of potential in what concerns improved shape memory. There are two main techniques to attain SMPU/CNts nanocomposites: in situ polymerization and mechanical melt mixing. The study here presented establishes a comparison between these two techniques. To assess the suitability of the latter a rather extensive characterization was carried out. The homogeneity of the CNTs dispersion into the polymer matrix was established through SEM and the thermal characterization has shown a rise in the glass transition temperature consistent with CNT loading. Furthermore, shape memory seems to improve with the nanoparticle reinforcement. Within the two processing techniques it could be referred that melt processing seems to be simpler to use with better laboratory repeatability, thus detaining a greater potential should nanocomposite tailoring at a larger scale be envisaged.

Numerous geological features that could be evaporitic in origin have been identified on the surface of Titan. Although they seem to be water–ice poor, their main properties – chemical composition, thickness, stratification – are essentially unknown. In this paper, which follows on a previous one focusing on the surface composition (Cordier, D., Barnes, J.W., Ferreira, A.G. [2013b]. Icarus 226(2),1431–1437), we provide some answers to these questions derived from a new model. This model, based on the up-to-date thermodynamic theory known as “PC-SAFT”, has been validated with available laboratory measurements and specifically developed for our purpose. 1-D models confirm the possibility of an acetylene and/or butane enriched central layer of evaporitic deposit. The estimated thickness of this acetylene–butane layer could explain the strong RADAR brightness of the evaporites. The 2-D computations indicate an accumulation of poorly soluble species at the deposit’s margin. Among these species, HCN or aerosols similar to tholins could play a dominant role. Our model predicts the existence of chemically trimodal “bathtub rings” which is consistent with what it is observed at the south polar lake Ontario Lacus. This work also provides plausible explanations to the lack of evaporites in the south polar region and to the high radar reflectivity of dry lakebeds.

The speed of sound in the protic ionic liquids (PILs) N-methyl-2-hydroxyethylammonium butyrate (m2HEAB) and N-methyl-2-hydroxyethylammonium pentanoate (m2HEAP) was measured at atmospheric pressure, and over the range of temperatures T = (293.15 to 343.15) K. The speed of sound and density of aqueous mixtures of the ionic liquid were also determined throughout the entire concentration range, within the (298.15 to 333.15) K temperature range and at atmospheric pressure. The excess molar volume, excess isentropic compressibility, excess speed of sound, apparent molar volume and apparent molar isentropic compressibility were calculated from the experimental density and speed of sound values. Furthermore, all the properties were correlated with selected analytical functions. The apparent molar volume of aqueous PILs was analysed by Pitzer-Simonson theory. The speed of sound of the PILs was predicted with the Wu et al. model and the molar compressibility of the same PILs and their aqueous mixtures were calculated from Wadas model. The results demonstrate that the molar compressibility calculated from Wadas model is almost a linear function of mole fraction and can be considered as temperature independent for a fixed mole fraction over the whole composition range. The results were analysed and discussed from the structural changes point of view in aqueous medium. (C) 2016 Elsevier Ltd. All rights reserved.

In spite of the great importance of the volumetric, transport, and surface properties of phosphonium-based ionic liquids, only limited information on these values seems to be available in the open literature. In this work, we present the results for the density measurements of the trihexyltetradecylphosphonium tris(pentafluoroethyl)trifluorophosphate, [(C6)3PC14][(C2F5)3PF3, FAP] over the ranges of temperature and pressure, T = (293.15 to 343.15) K and p = (0.1 to 25.0) MPa, respectively with an estimated uncertainty of ±0.5 kg · m−3. The viscosity and the surface tension were measured over the ranges T = (283.10 to 363.17) K and T = (298.51 to 343.29) K with maximum uncertainties of ±2.0% and ±0.4 mN · m−1. The experimental results on density were correlated using the Goharshadi–Morsali–Abbaspour equation of state. From this equation, thermomechanical coefficients as the isothermal compressibility, thermal expansivity, thermal pressure, and internal pressure were calculated. The Sanchez–Lacombe equation of state was also used for (pVT) correlation and the estimation of the free volume of [(C6)3PC14][FAP] which has been compared with other [(C6)3PC14]-based ionic liquids with variable anions. The Vogel–Fulcher–Tammann (VFT) equation for viscosity was used to correlate the viscosity. From the analysis of viscosity results for [(C6)3PC14]-based ionic liquids, a new prediction method has been developed for this property. Using the linear variation of the surface tension with the temperature, the surface entropy and enthalpy of [(C6)3PC14][FAP] were found. The reciprocal of dynamic viscosity (or fluidity) was correlated with temperature and a new relation between fluidity and surface tension was tested to [(C6)3PC14] ionic liquids.

In spite of the great importance of calorimetric data on phosphonium-based ionic liquids (PBILs), the information available in the literature is quite limited. This work reports the study of the thermal stability and the determination of heat capacity of the following (PBILs): tributyl(methyl)phosphonium methyl sulfate, [(C4)3PC1][MeSO4], trihexyl-tetradecylphosphonium chloride, [(C6)3PC14][Cl], trihexyl-tetradecyl-phosphonium dicyanamide, [(C6)3 PC14][DCA], trihexyl-tetradecylphosphonium bis((trifluoromethyl)sulfonyl) imide, [(C6)3 PC14][NTf2], and trihexyl-tetradecylphosphonium tris(pentafluoroethyl)trifluorophosphate, [(C6)3 PC14][FAP]. Measurements on the well-known IL 1-ethyl-3-methylimidazoliumbis((trifluoromethyl)sulfonyl)imide, [EMIM][NTf2], were also performed for comparative purposes. The thermal stability was assessed by conventional and high resolution modulated thermogravimetric analysis within the interval (303 to 873) K. The heat capacity was measured by modulated differential scanning calorimetry within the range (310 to 515) K with an uncertainty in the range (1 to 5) J · K−1 · mol−1. The experimental results were correlated using polynomial expressions. The Joback method for predicting ideal gas heat capacities was used in conjunction with the principle of corresponding states and the modified Lydersen–Joback–Reid method to predict the heat capacity of the ILs. The methods due to Valderrama et al. were also used with the same purpose.

In spite of the great importance of the (P, V, T) data of phosphonium–based ionic liquids, only limited information on these data seems to be available in the open literature. In this work, we present the results for the density measurements of the trihexyltetradecylphosphonium chloride, [(C6H13)3P(C14H29)][Cl] and trihexyltetradecylphosphonium dicyanamide, [(C6H13)3P(C14H29)][N(CN2)] with an estimated uncertainty of ±0.5 kg · m−3. The ranges of temperature and pressure are T = (273.15 to 318.15) K and p = (0.1 to 25) MPa for [(C6H13)3P(C14H29)][Cl] and T = (273.15 to 318.15) K and p = (0.1 to 35) MPa for [(C6H13)3P(C14H29)][N(CN2)]. The high consistency of our data for [(C6H13)3P(C14H29)][Cl] compared with those measured by other authors allowed all the experimental data for this IL to be combined and correlated using the Goharshadi–Morsali–Abbaspour equation of state over a wide range of temperature and pressure. From this equation, thermomechanical coefficients as the isothermal compressibility, thermal expansivity, thermal pressure, and internal pressure were calculated for the two ILs. The Sanchez–Lacombe equation of state was used also for (P, V, T) correlation and the estimation of the free volume in these phosphonium ionic liquids. Finally ionic volumes for trihexyltetradecylphosphonium cation and several anions available in the literature made possible the calculation of the free (hole) volume.

The experimental values of the (p, T) phase diagram of sulfur have been assessed through empirical equations commonly used. This treatment shows insufficiencies, namely those leading to significant uncertainties in the coordinates of the low-pressure triple points. An alternative way to try and find reliable equations for the phase equilibrium curves is provided by the exact integration of Clapeyron equation established and developed in a previous work. No fitting to (p, T) experimental data is then necessary. According to this method equations have been found to all the sulfur low-pressure equilibrium lines, and at the same time providing the enthalpies of transition between the phases as functions of temperature, and reliable values for the coordinates of the low-pressure triple points. The details of all these calculations and of the corresponding results are the object of the present paper. The (p, T) low-pressure phase diagram of sulfur is reconstructed on the basis of the results of the calculations carried out following these lines.

An unexpected feature of Titan's atmosphere is the strong depletion in primordial noble gases revealed by the Gas Chromatograph Mass Spectrometer aboard the Huygens probe during its descent on 2005 January 14. Although several plausible explanations have already been formulated, no definitive response to this issue has been yet found. Here, we investigate the possible sequestration of these noble gases in the liquid contained in lakes and wet terrains on Titan and the consequences for their atmospheric abundances. Considering the atmosphere and the liquid existing on the soil as a whole system, we compute the abundance of each noble gas relative to nitrogen. To do so, we make the assumption of thermodynamic equilibrium between the liquid and the atmosphere, the abundances of the different constituents being determined via {\bf } regular solution theory. We find that xenon's atmospheric depletion can be explained by its dissolution at ambient temperature in the liquid presumably present on Titan's soil. In the cases of argon and krypton, we find that the fractions incorporated in the liquid are negligible, implying that an alternative mechanism must be invoked to explain their atmospheric depletion., Comment: 11 pages, 1 figure

This work is a continuation of our studies on experimental measurements of physical properties on binary mixtures of the ionic liquid (IL) family 1-alkyl-3-methyl imidazolium tetrafluoroborate (CnMIM-BF4) with water and ethanol. Here, we present density for the ternary system Butyl-MIM-BF4 + ethanol + water at two temperatures (298.15 K and 323.15 K) and seven pressures (from 0.1 to 30 MPa). It should be noted that BMIM-BF4 is the only IL of the family CnMIM-BF4 that can be mixed with water and ethanol in all range of concentrations at room conditions. From the density data measured in function of pressure and temperature other important derived thermodynamic properties can be calculated, such us excess molar volumes, isothermal compressibility, isobaric expansion and the thermal pressure coefficients. These properties for selected ternary mixtures will be discussed and compared with data from the scarce number of published results for similar ternary mixtures with this same IL.

In this work, the results of density, viscosity, and surface tension measurements for ethanol are presented. Ethanol with stated mass fraction purity greater than 0.998 was further purified using molecular sieves. Density was measured within the temperature and pressure ranges, respectively, T = (278.15 to 353.15) K and p = (0.1 to 35) MPa by means of a vibrating tube densimeter, model DMA 512P from Anton Paar with an estimated uncertainty of ±0.5 kg · m−3. The experimental (p, ρ, T) results have been correlated by Tait equation. From this equation the isobaric expansivity, the isothermal compressibility, and the thermal pressure coefficient have been calculated. Viscosity was measured over the range T = (273.15 to 346.15) K using an Ubbelohde viscometer with a Schott–Gerate automatic measuring unit (Model AVS-470) with the associated uncertainty of ±0.001 mPa · s. The measured values were combined with selected values from the literature covering the range T = (223 K to 503) K, and the VTF model has been fitted to all the data. The surface tension of the liquid was measured using a tensiometer KSV Sigma 70 with a Du-Nouy ring for the range of T = (274.77 to 318.99) K with an uncertainty of ±0.01 mN · m−1. Using these data and critically assessed data of other authors compiled from the literature, a form of the IAPWS equation was used to correlate the surface tension within the temperature range 223 K up to the critical temperature.

Carbon nanotubes (CNTs) – perhaps the most enticing class of nano-materials, can be added in small volume fractions to enhance the thermal properties of fluids when process intensification or even device miniaturization is required. This work reports on the results obtained when measuring viscosity, and thermal conductivity of homogenous CNTs – water based nanofluids. The influence of CNTs volume concentration on the nanofluid thermo-physical properties is studied and measurements are undertaken at different temperatures, ranging from 283.15 K to 333.15 K. The nanofluids have been prepared by adding different volume concentrations of treated CNTs to water. The latter has been then sonicated for one hour and the colloidal stability monitored via UV – vis spectrophotometer. The absorbance of the nanofluid was observed at 263 nm, and the average concentration of CNTs was maintained at 9.35 mg/l, even after 200 hours, over 97% when compared with the initial concentration. The viscosity was measured using a controlled stress rheometer, and the measurements were performed in the shear rate ranging from 0 to 600 sec-1. At the same shear rate and temperature, the viscosity was observed to rise with increasing CNTs volume concentration. In what concerns thermal conductivity, it was assessed with a KD2 pro thermal property tester from Decagon Devices and the results clearly show that thermal conductivity rises with CNTs volume fraction, reaching its maximum at 2.5%vol where it represents more than 100% enhancement when the comparison is established with the corresponding value for the base fluid, at the same temperature conditions (i.e. 283.15 – 303.15 K). Furthermore, at higher temperatures (i.e. 313.15 – 333.15 K), the latter, for up to 1%vol concentration represents a 70% enhancement in thermal conductivity.

In this article the Unit Operations and Separation Processes area of a virtual platform called LABVIRTUAL(http://labvirtual.eq.uc.pt) is presented aiming to support the autonomous study of undergraduate students engaged in a Chemical Engineering degree, especially in Portuguese-speaking countries. The main features, subjects, computational applications, and examples in the platform are described, as well as a first assessment by the students. © 2009 Wiley Periodicals, Inc. Comput Appl Eng Educ 20: 175–186, 2012

The need to develop the capacity for autonomous and critical thinking in students and introduce practical approaches that complement the scientific background, have been acting as driving-forces that motivate engineering educators to develop new teaching methodologies. The Chemical Engineering Departments of both the Universities of Coimbra and Porto have been experimenting in this area and addressing these concerns. Recently, they have been engaged in a broader project, involving a large group of academics with complementary competencies. This project is aimed at developing a virtual platform directed towards the learning of Chemical Processes with a wide scope. From the functional point of view the platform is organized into four main areas: Chemical Engineering, Chemical Processes, Virtual Experiments and Simulators. The Chemical Processes area is further divided into four different sections: Unit Operations and Separations, Chemical Reaction, Process Systems Engineering and Biological Processes. These sections include simulators, applications and case studies to better understand the chemical/biochemical processes. The Virtual Experiments area considers both the laboratory visualization of the basic phenomena related to the processes in the other four sections, and the remote monitoring of laboratory experiments. This platform, constructed around a dynamic Web Portal, allows discussion forums and is also aimed at sharing experiences with other schools. This paper describes the different subjects included in the web platform, as well as the simulation strategies and the web methodologies used for its construction, and also presents examples of application in the classroom.

In spite of their interest, viscosities of fluorocarbon compounds are scarce, and the available data are unreliable and of poor accuracy. In this work, viscosity measurements of linear, cyclic, aromatic, and R-substituted perfluorocarbons were carried out in the temperature range between (298.15 and 318.15) K using an Ubbelohde viscometer. The experimental results show that fluorinated compounds present viscosities considerably higher than their hydrocarbon homologues as expected. The viscosities increase from linear to aromatic to cyclic perfluorocarbons and within each family with the molecule size. The R-fluorine substitution by bromine increases the fluorocarbon viscosity due to the molecular weight increase. The Sastri-Rao method, a group contribution method for the liquid viscosity prediction, was applied for all the fluorocarbons where the viscosity was experimentally measured in this work. Using the new experimental data from this work, new group contribution values are proposed for fluorocarbon compounds allowing for a reduction of the average relative deviation from 12.0 % to 1.3 %.

The speed of sound in the ionic liquid (IL) N-methyl-2-hydroxyethylammonium propionate (m2HEAPr) was measured at atmospheric pressure, and over the range of temperatures T = (293.15 to 343.15) K. The speed of sound and density were also measured for aqueous mixtures of the ionic liquid throughout the entire concentration range at temperatures T = (298.15 to 333.15) K and atmospheric pressure. The excess molar volume, excess isentropic compressibility, excess speed of sound, apparent molar volume, and isentropic apparent molar compressibility were calculated from the values of the experimental density and speed of sound. The results were analyzed and are discussed from the point of view of structural changes in the aqueous medium. All the above mentioned properties were correlated with selected analytical functions. The Jouyban-Acree model was used to correlate the density of the mixtures studied with the temperature. The model accuracy was evaluated by calculating the absolute average deviation (AAD) for the correlation, which is 0.4%. The speed of sound of the m2HEAPr was predicted with the Wu et al. model with a maximum deviation of 2%. The molar compressibility of m2HEAPr and their aqueous mixtures was calculated from the Wada's model. To the authors' knowledge, this is the first time this model is applied to these systems. The results demonstrate that the molar compressibility calculated from Wada's model is almost a linear function of mole fraction and can be considered as temperature independent for a fixed mole fraction over the whole composition range. (C) 2015 Elsevier Ltd. All rights reserved.

The viscosities and the densities of the ternary mixtures water+n-pentyl acetate+methanol and those of the constituent binaries have been measured at 303.15 K and atmospheric pressure in the homogeneous region. The respective viscosity deviations and excess molar volumes were fitted to a Redlich–Kister (RK) type equation. A modified Redlich–Kwong–Soave equation of state due to Fuller was used with the Eyring kinematic viscosity model to correlate viscosities of binary data. The equation of state constants were calculated using the van der Waals one-fluid mixing rules with the cross-parameters, aij, obtained with the classical and a two-parameter Redlich–Kister combining rules. The new model correlates the viscosity of the binaries with an average absolute deviation

In this work, experimental data on the gas solubility of hydrofluorocarbons (CHF3, CH2F2 and CH3F) in four room-temperature ionic liquids (RTILs) were determined within the temperature range 288 K to 308 K and at atmospheric pressure. The RTILs used were 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide([C2mim][NTf2]), (trihexyl)tetradecyl-phosphoniumbis(trifluoro-methylsulfonyl)imide ([P6,6,6,14][NTf2]), and N-methyl-2-hydroxyethylammoniumpropionate ([m-2-HEA][Pr]) and pentanoate ([m-2-HEA][P]). Two modelling approaches, which we denote as predictive and correlative, were compared. In the former, the cubic plus association equation of state (CPA EoS) is used as a predictive model to estimate the solubilities using only pure components physical properties. In the latter, the regular-solution theory is the basis to build an empirical model whose parameters are obtained through least-squares fitting of experimental values.

The property changes associated with the differences in chemical composition of biodiesel may change the fuel injection timing which in turn cause different exhaust emissions and performance of engines. The property that has an important effect on the fuel injection timing is the speed of sound (related with isentropic bulk modulus). Despite the speed of sound of pure fatty acid (methyl and ethyl) esters being reasonably known in a wide range of temperature the experimental data for biodiesel are very scarce in the literature. In this work the speed of sound of six fatty acid methyl esters (FAME = laurate (MeC12:0), myristate (MeC14:0), palmitate (MeC16:0), stearate (MeC18:0), oleate (MeC18:1), linoleate (MeC18:2)) and six biodiesel fuel samples were measured using a non-intrusive ultrasonic methodology. The measurements for FAMEs were made at atmospheric pressure from a minimum of 288.15 K to a maximum of 353.15 K, and in the temperature range 298.15–353.15 K for biodiesel samples. The uncertainty of the measurements was estimated as less than ±1 m s−1. The speed of sound data combined with available density data from literature was used to calculate the isentropic compressibility and the molecular compressibility for the FAMEs and for the biodiesel samples. The results for molecular compressibility evidenced that this property is almost independent of the temperature in the temperature range of calculations both for FAMES and biodiesel. Linear relationships were established between the molar compressibility and the molecular weight for FAMES and biodiesel. The before mentioned behavior of molar compressibility face to temperature and molecular weight make it possible to develop prediction methods for the calculation of the speed of sound.

The thermophysical properties including density, heat capacity, thermal stability and phase behaviour of protic ionic liquids based on the N-methyl-2-hydroxyethylammonium cation, [C2OHC1NH2](+), with the carboxylate anions (propionate, [C2COO] , butyrate, [C3COO] , and pentanoate, [C4COO] ) are reported and used to evaluate structure-property relationships. The density was measured over the temperature and pressure ranges, T = (298.15 to 358.15) K and p = (0.1 to 25) MPa, respectively, with an estimated uncertainty of +/- 0.5 kg . m(-3). The pressure dependency of the density for these ionic liquids (ILs) is here presented for the first time and was correlated using the Goharshadi-Morsali-Abbaspour (GMA) equation of state, from which the isothermal compressibility, thermal expansivity, thermal pressure, and internal pressure were calculated. The experimental PVT data of the protic ILs were predicted by the methods of Gardas and Coutinho (GC), and Paduszynki and Domanska (PD). The thermal stability was assessed by high resolution modulated thermogravimetric analysis within the range T = (303 to 873) K. The heat capacity was measured in the temperature range T = (286.15 to 335.15) K by modulated differential scanning calorimetry with an uncertainty in the range (1 to 5) J . K-1 . mol(-1). The Joback method for the prediction of ideal gas heat capacities was extended to the ILs and the corresponding states principle was employed to the subsequent calculation of liquid heat capacity based on critical properties predicted using the modified Lydersen-Joback-Reid method. The Valderrama's mass connectivity index method was also used for liquid heat capacity predictions. This series of N-methyl-2-hydroxyethylammonium was used to establish the effect of the anion alkyl chain length on the ionic liquid properties. (C) 2013 Elsevier Ltd. All rights reserved.

Titan, the main satellite of Saturn, has an active cycle of methane in its troposphere. Among other evidence for a mechanism of evaporation at work on the ground, dry lakebeds have been discovered. Recent Cassini infrared observations of these empty lakes have revealed a surface composition poor in water ice compared to that of the surrounding terrains --- suggesting the existence of organic evaporites deposits. The chemical composition of these possible evaporites is unknown. In this paper, we study evaporite composition using a model that treats both organic solids dissolution and solvent evaporation. Our results suggest the possibility of large abundances of butane and acetylene in the lake evaporites. However, due to uncertainties of the employed theory, these determinations have to be confirmed by laboratory experiments., Icarus, in press

Between 2004 and 2007 the instruments of the CASSINI spacecraft discovered hydrocarbon lakes in the polar regions of Titan. We have developed a lake-atmosphere equilibrium model allowing the determination of the chemical composition of these liquid areas. The model is based on uncertain thermodynamic data and precipitation rates of organic species predicted to be present in the lakes and seas that are subject to spatial and temporal variations. Here we explore and discuss the influence of these uncertainties and variations. The errors and uncertainties relevant to thermodynamic data are simulated via Monte-Carlo simulations. Global Circulation Models (GCM) are also employed in order to investigate the possibility of chemical asymmetry between the south and the north poles, due to differences in precipitation rates. We find that mole fractions of compounds in the liquid phase have a high sensitivity to thermodynamic data used as inputs, in particular molar volumes and enthalpies of vaporization. When we combine all considered uncertainties, the ranges of obtained mole fractions are rather large (up to ~8500%) but the distributions of values are narrow. The relative standard deviations remain between 10% and ~300% depending on the compound considered. Compared to other sources of uncertainties and variability, deviation caused by surface pressure variations are clearly negligible, remaining of the order of a few percent up to ~20%. Moreover no significant difference is found between the composition of lakes located in north and south poles. Because the theory of regular solutions employed here is sensitive to thermodynamic data and is not suitable for polar molecules such as HCN and CH3CN, our work strongly underlines the need for experimental simulations and the improvement of Titan's atmospheric models., Comment: Accepted in Planetary and Space Science

Experimental density measurements are reported along with the derived thermodynamic properties (isothermal compressibility, isobaric expansivity, and thermal pressure coefficient) for trihexyltetradecylphosphonium-based ionic liquids—chloride, bromide, bis(trifluoromethylsulfonyl)imide, dicyanamide and methyl sulfonate—in the pressure range (0.10 to 45.00 MPa) and temperature range (283.15 to 333.15) K. The effect of the anion of the ionic liquid on the properties under study was evaluated. Experimental densities were correlated using the Tait equation, the modified cell model equation of state, and the Sanchez−Lacombe equation of state, and compared against the predictive method proposed by Gardas and Coutinho. It is shown that the three correlations describe well all the ILs studied, with the Tait equation providing the lowest average relative deviation (less than 0.004 %) and the Sanchez−Lacombe equation of state the highest (inferior to 0.5 %), and that the predicted densities estimated by Gardas and ...

The experimental results on the fusion of the heavier rare gases at very high pressures, obtained in the last 20 years, are examined and analysed in conjunction with the measurements made at lower pressures from 1940 onwards. The parameters in the Simon equation for the melting curves of Xe, Kr, and Ar are determined, and the coordinates of a possible high-pressure {s(fcc) + s(hcp) + l} triple-point are identified for each one of these three elements. The enthalpies of transition of the transformations involved are estimated as well as their respective values of the entropies of transition. http://www.sciencedirect.com/science/article/B6WHM-4R6B2R8-1/1/b0b0f09c6f21e6deaf5d2a51875db54f

Experimental density measurements are reported, and the derived thermodynamic properties, such as the isothermal compressibility, the isobaric expansivity, and the thermal pressure coefficient are presented as Supporting Information for several imidazolium-based ionic liquids (ILs), namely, 1-ethyl-3-methyl-imidazolium bis(trifluoromethylsulfonyl)imide [C2mim][NTf2], 1-heptyl-3-methyl-imidazolium bis(trifluoromethylsulfonyl)imide [C7mim][NTf2], 1-octyl-3-methyl-imidazolium bis(trifluoromethylsulfonyl)imide [C8mim][NTf2], 1-ethyl-3-methyl-imidazolium tetrafluoroborate [C2mim][BF4], and 1-butyl-3-methyl-imidazolium tricyanomethane [C4mim][C(CN)3] in the pressure (0.10 < p/MPa < 30.00) and temperature (293.15 < T/K < 393.15) domains. These ILs were chosen to provide an understanding of the influence of the cation alkyl chain length and the anion influence on the properties under study. Experimental densities are correlated with the Tait equation with an average absolute deviation (AAD) less than 0.04 %. Experimental densities are in good agreement with the densities obtained by some recent predictive methods proposed in the literature.

The results of PVT measurements of the liquid phase within the temperature range of (298 to 393) K and up to 35 MPa are presented for some aliphatic esters. Measurements were made by means of a vibrating-tube densimeter, model DMA 512P from Anton Parr. The calibration of the densimeter was performed with water and n-heptane as reference fluids. The experimental PVT data have been correlated by a Tait equation. This equation gives excellent results when used to predict the density of the esters using the method proposed by Thomson et al. (AIChE J. 1982, 28, 671−676). Isothermal compressibilities, isobaric expansivities, thermal pressure coefficients, and changes in the isobaric heat capacity have been calculated from the volumetric data.

The surface tension in the homogeneous domain of the ternary liquid mixtures water + n-butyl acetate + methanol and water + n-pentyl acetate + methanol as well as of the constituent binaries has been measured at 303.15 K and atmospheric pressure. The respective excess surface tension was correlated as a function of the composition using empirical and thermodynamic-based relations. The liquid interfacial tension was measured in the liquid–liquid equilibrium range at the same conditions of temperature and pressure. A new equation is proposed to correlate the excess surface tension of binary mixtures. This equation can be obtained from the Butler equation and correlates well the excess surface tension data. The prediction of the surface tension of the binary and ternary systems has been made using the Sprow and Prausnitz model. The Fu et al. and Li et al. models were also applied to predict that property in the ternary systems. The liquid interfacial tension of the ternary systems was correlated and predicted using the relations proposed by Li and Fu and Fu et al., respectively, with satisfactory results.

In this work, the exactly integrated form of the Clapeyron equation found by Mosselman et al. has been used in a systematic manner to derive a comprehensive set of equations describing the first-order transition curves of pure substances. The application of each of these equations requires the knowledge of only one (reference) point on the particular equilibrium line, of the corresponding enthalpy of transition, and some ancillary data (molar volumes and heat capacities of the phases at equilibrium). No fitting to (p, T) experimental data is needed. In this respect the equations developed here can be regarded as a source for calculating a priori the phase equilibrium curves. The results have been tested for a number of selected pure substances of variable molecular complexity, and the uncertainties attached to the calculations have been assessed. Empirical equations currently used for first-order transitions are compared with those obtained from the exact integration. As far as we are aware, no equation was previously proposed for solid + solid equilibrium lines. http://www.sciencedirect.com/science/article/B6WHM-45BCCXR-R/1/35cc4f5c5181134280313d5dd0f7550d

Solubility data for the refrigerants HFC23 (CHF3), HFC32 (CH2F2) and HFC125 (C2HF5) in water have been determined as a function of the temperature in the range of temperatures 288‐303 K at atmospheric pressure. These hydrofluorocarbons (HFCs) are good substitutes of the chlorofluorocarbons (CFCs), which have significant impact to stratospheric ozone depletion. The ‐ approach has been used to predict the experimental results. The fugacity coefficients were calculated using a modified version of the Peng‐Robinson equation of state. © 2000 Elsevier Science B.V. All rights reserved.

As a complement to the teaching of university students, the use of web based tools enhances students’ autonomy, helps in dealing with different learning rhythms and allows reaching students in different locations. Moreover, the web can also be used to attract youngsters (basic and secondary school students) to science subjects. All these functions have been combined in a single web platform “LABVIRTUALâ€, based in the Chemical Engineering Department of the University of Coimbra. Even if the Portal was developed for the Teaching of Chemical Processes, a specific section directed to the secondary school students has been created as well, grounded on the basic concepts they acquire at the secondary level. In addition, the portal possesses an area dedicated to the understanding of Chemical Engineering. By guiding the secondary school students to the use of these tools, they are led to understand the connection between Engineering (Chemical Engineering) and the basic phenomena they are studying. Moreover, the proximity factor can contribute to rouse the curiosity of the users to search for more advanced information about Chemical Engineering science and applications. This approach may motivate them to engineering subjects and also to raise their interest in the study of basic science subjects for which they start finding a practical application.