Band 81, Heft 10

The 20th International Conference on Chemical Thermodynamics (ICCT 2008) was held in Warsaw, Poland, 3-8 August 2008. It was organized jointly by the Institute of Physical Chemistry of the Polish Academy of Science, both Faculties of Chemistry of the Warsaw University of Technology and the Warsaw University, the Polish Chemical Society, and under the auspices of the International Association of Chemical Thermodynamics (IACT). This conference was significant in a line of traditional meetings gathering biennially chemical thermodynamists from all over the world. Almost 300 participants from 39 countries presented 153 oral presentations and 174 posters, among the former ones 12 plenary and 27 invited lectures were given by distinguished researchers. The culminating event was the Rossini lecture given by Prof. Jürgen Gmehling from the University of Oldenburg in Germany, entitled "Present status and potential of group contribution methods for process development". Prof. Gmehling was awarded the prestigious Frederick D. Rossini Award, which has been given biennially to contemporary chemical thermodynamics for an outstanding contribution. Five 2008 IACT Junior Awards were awarded to young scientists for notable achievements presented during the conference in the form of an oral communication. The conference program was grouped into the following symposia: - Molecular simulations of fluid and statistical thermodynamics - Phase equilibria, supercritical fluids, and separation techniques - Electrolyte solutions and non-electrolyte mixtures including reactive chemical systems - Thermodynamics and properties in the biological, medical, pharmaceutical, agricultural, and food sectors - Nanosystems, nanodevices, and advanced materials - Thermochemistry, calorimetry, and molecular energetics - Ionic liquids - Surface and colloid chemistry - Industrial thermodynamics and databases - Thermodynamics frontiers and education - Modulated and oscillation temperature techniques - Environmental thermodynamics This issue of Pure and Applied Chemistry presents 16 papers selected from the plenary and invited lectures delivered at ICCT 2008 with an emphasis on industrial thermodynamics and thermochemistry. We hope that this selection will provide insight into the scientific program of the conference. The 21st International Conference on Chemical Thermodynamics will be held in Tsukuba, Japan, 1-6 August 2010. Tadeusz Hofman Conference Editor

Recent works on evaporation and condensation demonstrate that even these simplest irreversible processes, studied for over 100 years, are not well understood. In the case of a liquid evaporating into its vapor, the liquid temperature is constant during evaporation and the evaporation flux is governed by the heat transfer from the hotter vapor into the colder liquid. Whether liquid evaporates into its own vapor or into the vacuum, the irreversible pathway in the process goes through a number of steps which quickly lead to the steady-state conditions with mechanical equilibrium in most parts of the system—the fact overlooked in all previous studies. Even less is known about general rules which govern systems far from equilibrium. Recently, it has been demonstrated that a work done in an irreversible process can be related to the free energy difference between equilibrium states joined by the process. Finally, a real challenge in thermodynamics is a description of living systems since they do not have equilibrium states, are nonextensive, (i.e., they cannot be divided into subsystems), and cannot be isolated. Thus, their proper description requires new paradigms in thermodynamics.

Experimental data have served two critical roles in chemical process technology: (1) by providing the definitive quantitative basis to evaluate competing processes, to optimize designs, and ultimately to guarantee plant performance; and (2) by guiding the form and structure of applied-thermodynamics correlations. This paper first presents two representative applications to highlight the role of thermodynamic and transport properties in chemical process technology: ammonia recovery from syngas using water as solvent, and design of a caustic-guard system to eliminate small residual concentrations of SO 2 from a gas stream. These applications illustrate the first role of experimental data. The paper next studies the second role by examining the historical contribution of experimental data—over two centuries—in guiding the development of key concepts and correlations, such as Henry’s law (1802), group-contribution methods (Kopp, 1842), Raoult’s law (1878), second-virial-coefficient correlation (Berthelot, 1907), surface-tension correlation (Macleod, 1923), the use of one property to estimate another (Othmer, 1940), cubic equations of state (Redlich and Kwong, 1949), electrolyte systems (van Krevelen, 1949), acentric factor (Pitzer, 1955), and highly accurate equations of state (Span and Wagner, 2003). The analysis reveals that careful, accurate, and wide-ranging experimental data have identified the patterns of the underlying phenomena.

Factual data banks nowadays play an important role as a source for thermophysical property data for use in chemical process simulation, environmental models, and many other computer-based applications. In this work, the historical developments leading to modern factual data banks, the differences compared to other more bibliographically oriented data banks, and their most important applications and future potential will be discussed by using the example of the Dortmund Data Bank (DDB). As the development of the different predictive models for mixtures is covered in a separate publication, this paper focuses on pure-component property estimation, regression of model parameters, test and verification of model parameters prior to process simulation, and advanced topics in process synthesis such as selection of entrainers and data-mining applications.

It is of utmost importance to have accurate experimental data available in order to develop accurate modeling for scientific and engineering purposes as it is emphasized through several herein-reported discussions with reknown scientists and engineers. Many methods are used to determine phase equilibria. Classification of the methods is not straightforward as several basic principles can be mixed in several different ways. In this paper, we have selected some techniques, developed in our laboratory, to illustrate one type of classification. Several apparatuses are described. The techniques where all phases are analyzed are very often preferred to those relying on partial determinations requiring data treatment through models. The internal analyses by means of spectroscopic or other in situ analysis techniques are not applicable every time. Then, sampling devices are necessary. Sampling devices must be reliable and lead to extract sample amounts small enough not to disturb the equilibrium under study. The ROLSI™ sampler developed at MINES ParisTech is a very powerful device allowing one to work up to 100 MPa, 850 K, with corrosive components and with samples from 1 μg to some mg. Applications of this sampler are described for fundamental research (phase equilibrium measurements) and industrial purposes (process control and monitoring).

Extensive application of chemical thermodynamics to exotic aggregation formed in thermotropic liquid crystals is briefly described. Through thermodynamic analyses and considerations of experimental results on liquid crystals, the unexpected sharing of common properties by thermo- and lyotropic liquid crystals is demonstrated. In some thermotropic liquid crystals, the terminal alkyl chain attached to the molecular core is highly disordered, as indicated by the magnitude of configurational entropy. The molten chain serves as intramolecular solvent (self-solvent), as evidenced by the close similarity between phase diagrams against chain length and composition in the binary system with n -alkane. These facts lead to the quasi-binary picture of thermotropic liquid crystals. Consideration of the thermodynamic potential expanded in terms of density fluctuation gives a new insight into the multicontinuous phases formed in simple systems consisting of anisotropic, rodlike particles.

A force field (FF) is reported for hydrazine (N 2 H 4 ) and organic hydrazine derivatives, including monomethylhydrazine, 1,1-dimethylhydrazine, monoethylhydrazine, and 2-hydroxyethylhydrazine. The FF successfully reproduces a range of equilibrium properties, including vapor–liquid coexistence densities, vapor pressures, enthalpies of vaporization, and critical properties. Several dynamic properties, including self-diffusion coefficients and rotational time constants, are reported and found to be qualitatively consistent with experimental viscosities. Using this as a basis, a FF is also developed for the protonated forms of these species, i.e., hydrazinium-based cations. Properties of 1:1 energetic salts formed by pairing these cations with the nitrate anion are computed and compared with a limited amount of experimental data. The simulations indicate that the ionic liquid (IL) 2-hydroxyethylhydrazinum nitrate (2-HEHN) has significantly slower dynamics than the other hydrazinium ILs.

The lower critical solution temperature (LCST) phase behavior of poly(benzyl methacrylate) (PBnMA) in room-temperature ionic liquids (ILs) was studied by considering the effect of the chemical structure of ILs on the phase separation temperature ( T c ). It was found that the LCST behavior of PBnMA was observed in ILs containing [NTf 2 ] anions and PF 6 anions. T c changed significantly with a small change in the chemical structures of the cations. High-sensitivity differential scanning calorimetry (DSC) was successfully performed for studying the LCST phase separation of PBnMA in two different imidazolium-based ILs. Endothermic peaks corresponding to the phase separation of PBnMA from the ILs were clearly observed at ca. 100 °C in the DSC thermograms. It was experimentally verified for the first time that the negative enthalpy and entropy change of mixing of PBnMA in ILs caused the LCST phase separations. The absolute values of the thermodynamic parameters for the phase transition of PBnMA in ILs obtained in this study were much lower than those reported in previous studies for aqueous polymer solutions that exhibit LCST phase behavior, such as poly( N -isopropylarylamide) and poly(vinyl methyl ether). Small changes in the thermodynamic parameters resulted in a large change in the phase separation temperature even by small changes in the chemical structure of the ILs and polymers. The microscopic desolvation process detected from the DSC measurements was inferred to have occurred before the macroscopic phase separation detected from turbidity measurements. The dependence of the endothermic peak temperatures on the DSC scan rate was observed even at slow scan rates. These results indicate that the phase separation of PBnMA from ILs is characterized by extremely slow kinetics.

Calorimetric measurements on biological systems from small molecules to whole organisms lead to a new conception of the nature of live matter that has profound consequences for our understanding of biology. The data show that the differences in Gibbs energy (Δ G ) and enthalpy (Δ H ) are near zero or negative and the difference in entropy (Δ S ) is near zero between a random mixture of molecules and live matter of the same composition. A constant input of energy is required to maintain ion gradients, ATP production, and the other functions of living matter, but because cells are organized in a spontaneous process, no energy input is required to maintain the structure or organization of cells. Thus, the origin of life and evolution of complex life forms occurs by thermodynamically spontaneous processes, carbon-based life should be common throughout the universe, and because there is no energy cost, evolution can occur relatively rapidly.

The combination of experimental calorimetric measurements, particularly of the standard energies and enthalpies of combustion and formation, and theoretical examination of model molecules constitutes a powerful tool for the understanding of the conformational and chemical behavior of organic molecules. In this article, several examples are provided where the synergy between experiment and theory made possible the comprehension of various fundamental interactions in oxygen- and sulfur-containing six-membered heterocyclic compounds, the determination of the strain energy in two C 8 H 8 derivatives, dimethyl cubane-1,4-dicarboxylate and dimethyl cuneane-2,6-dicarboxylate, and the calculation of the enthalpies of formation of the parent compounds, cubane and cuneane, and the study of the energy–structure relationship in barbituric acid.

Heat capacity properties of some nanostructured oxides, metals, and zeolites were studied, mainly with the aid of low-temperature adiabatic calorimetry. Obvious enhancement in the heat capacity of nanostructured materials to different degrees was observed as compared with the corresponding coarse-grained materials. The contributions of enhanced heat capacity of nanostructured materials toward properties such as density, thermal expansion, sample purity, surface effect, and size effect are discussed.

Thermoanalytical methods have found increasing application in medicine due to the improved sensitivity and usability of the available instrumentation. Studies have identified important findings applied to medicine, including information on the thermal properties of the skin and the effect of insertion into body cavities of implants and prosthetics. These studies have explored the thermal stability of various materials to provide insight into drug penetration in order to design drug delivery systems, which are not only safe but capable of delivering improved and predictable therapeutic outcomes for patients. Differential scanning calorimetry (DSC) has also been applied to the study of disease states such as diabetes, where changes in the collagen structure of the skin which may lead to long-term complications in these patients, can be detected. Although these results may at this stage not have significant clinical implications, they do provide medical researchers with a starting point for future investigations. The application of these techniques has been further extended to examinations of body systems and other disease states. The key for the future will be the ability of these techniques not only to provide information on alterations in these biological systems, but also to determine whether these alterations are clinically relevant.

The thermodynamics of adsorption of gaseous organic compounds such as polycyclic aromatic hydrocarbons (PAHs) on water films is reviewed and discussed. The various experimental methods available to determine the thermodynamic equilibrium constant and the structure–activity relationships to correlate and estimate the same are reviewed. The atmospheric implications of the adsorption and oxidation of PAHs at the air–water interface of thin films of water such as existing in fog droplets, ice films, and aerosols are also enumerated.

Thermodynamic principles can be applied for describing the atmospheres and the internal structure of celestial bodies using Saturn's moon Titan as a most appropriate example. Some basic physical data of Titan such as the measured temperature and pressure on its surface, the atmospheric composition, Titan’s density and diameter, and other information allow us to predict further properties which have not been determined directly by measurements. The existence of a liquid phase covering smaller parts of the surface can be confirmed, and the composition of the liquid can be predicted. The change of temperature with the height over the surface and the appearance of clouds and rainfall in the atmosphere consisting essentially of CH 4 + N 2 mixtures can also be predicted. By developing a new method of calculation of atmospheric scenarios, the chemical history of Titan’s surface and atmosphere can be roughly reconstructed taking into account the known rate of methane destruction caused by radiative absorption of sunlight. Finally, some estimations concerning the material structure and the pressure behavior of Titan’s interior can be made. Only basic knowledge of thermodynamics and physics is required to understand essential features in a strange world that is more than one billion kilometers away from us.

Ordinary macroscopic thermodynamics is applied when the number of atoms in the studied systems is "large". Conditions where nanosystems are "large" with respect to thermodynamics definition are first discussed. In the thermodynamical regime, size and shape effects are known to be important. It has been known for a long time that the melting temperature of nanosystems decreases when their size decreases. A generalization of this leads to the conclusion that phase diagrams are also size- and shape-dependent. In nanosystems, the number of atoms is limited. This differs from classical thermodynamics, where the number of atoms is assumed to be unlimited. The consequences of this difference for the definition of phase diagrams are discussed. In particular, the liquidus and solidus lines have to be carefully defined. The structure of the two-phase nanoparticles also plays a role in the calculation of the phase diagrams.

With standard differential scanning calorimetry (DSC), it is possible to derive calorimetric data for equilibrium or metastable samples. The introduction of temperature-modulated DSC (TMDSC) permits in its quasi-isothermal (non-scanning) mode (TMDC), long-time apparent heat capacity measurements of high precision (±1 %). For flexible molecules, heat capacity measurements from the various calorimetric methods could be combined in the ATHAS Data Bank, which now contains experimental data for over 200 materials. These data were linked to the vibrational and large-amplitude motion of the constituent atoms and molecules, to provide a base for the judgement of the thermal analyses, extending outside the range of equilibrium or metastability with an error of only 2-5 %. The TMDC together with DSC is now able to quantitatively assess the reversibility of thermal processes. A sufficient number of systems have been analyzed in this fashion to develop better understanding of macro-, micro-, and nanophases of flexible macromolecules. The new concepts discussed are: (1) multiple glass transitions due to possible rigid-amorphous fractions (RAFs) and glass transitions within crystals, both observed in semicrystalline macromolecules, and (2) locally reversibly melting on the surface of chain-folded crystals. The locally reversible melting decreases with crystal perfection and also disappears when the chains become rigid.

We report experimental measurements of the melting of mixtures confined in nanoporous materials. Dielectric relaxation spectroscopy (DRS) was used to determine the solid–liquid phase diagram of bromobenzene/carbon tetrachloride (C 6 H 5 Br /CCl 4 ) mixtures confined in controlled pore glasses (CPGs) with an average pore diameter H = 7.5 nm. Our results show that the phase diagram of the confined mixture is of the same type as that for the bulk, but the solid–liquid coexistence lines are located at different temperatures. These results are compared with those previously obtained for CCl 4 /C 6 H 6 mixtures in activated carbon fibers (ACFs).