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Chemistry International
Vol. 23, No. 6
November 2001

 

News from IUPAC

Report on Second Workshop on Thermochemical, Thermodynamic, and Transport Properties of Halogenated Hydrocarbons and Mixtures, 9-11 April 2001, Paris, France

by Dr. John H. Dymond

The objective of this IUPAC project (2000-027-1-100) is to increase knowledge and understanding of the thermodynamic and transport properties of halogenated organic compounds, especially halogenated aliphatic hydrocarbons, of their mixtures, and also of their mixtures with hydrocarbons.

In the first workshop, which was held in Pisa, Italy, 15-18 December 1999 (and reported in Chemistry International, Vol. 22, p. 162, 2000), all the submitted papers that related to this general topic were accepted for oral communication or poster presentation. A final, roundtable discussion considered the priorities for further research. As a result of this effort, a Certificate of Research Needs was drawn up. The main goals are to present and discuss new experimental measurements, particularly for the following systems:

  • propane/butane + refrigerants
  • binary and ternary hydrofluorocarbons (HFCs)
  • higher alkanes/ethers + refrigerants
  • lubricant oils + refrigerants
  • gas + perfluorocompounds, with medical application

The goals also include presenting and discussing the results of calculations, particularly the following:

  • intermolecular potential calculations for methane-, ethane-, and propane-derived HCFCs using ab initio methods, to develop models for theory-based calculation of macroscopic properties
  • molecular simulations, particularly for methane derivatives
  • improved correlation methods

Further details are given on the web site (see http://www.iupac.org/projects/2000/2000-027-1-100.html).

This second workshop was structured with four main themes: i) environmental constraints and regulation, ii) new products, iii) new measurements, and iv) fundamentals and simulation.

There were 11 invited lectures. In the opening lecture, Dr. C. Ewald (Ministère de l’Aménagement du Territoire et de l’Environnement, Paris, France) described the objectives of the French policy to stabilize greenhouse gas emissions by prevention of leakage, confinement, recovery, and recycling. For the longer term, there is a need to encourage use of fluids with low global warming potential, consistent with the requirements of safety, energy efficiency, and reasonable investment costs.

Dr. P. Horrocks (European Commission, Brussels, Belgium) described the main groups of provisions in regulation EC 2037/00, which has applied in all Member States since 1 October 2000.

First, it will ban all hydrochlorofluorocarbon (HCFC) use within four years, except for the maintenance of existing equipment, which is well before that agreed in the Montréal Protocol.

Second, it will introduce a slightly faster reduction schedule, but the same phaseout date, as that of the Montréal Protocol for methyl bromide use in agriculture.

Third, there are measures to minimize emissions of all ozone-depleting substances.

Dr. N. Campbell (ATOFINA, Paris la Défense, Paris) reviewed existing European legislation on chlorofluoro-carbons (CFCs) and HCFCs, and detailed existing discussions on hydrofluorocarbons (HFCs) taking place within the European Union. A subgroup of the European Commission has been set up to recommend policies and measures to control the emissions of HFCs as part of its European Climate Change Program. Dr. J. Morley (DuPont Fluoroproducts, Hemel Hempstead, England, UK) addressed the question "Are we near an industry standard for refrigerant properties?" He discussed the various important worldwide activities that were taking place to determine accurate thermophysical properties of candidate alternative refrigerant working fluids.

Prof. K. Watanabe (Keio University, Yokohama, Japan) reported P, r, T, x measurements for R-134a (1,1,1,2-tetrafluoroethane) + R-290 (propane) and R-125 (pentafluoropropane) + R-290. Determination of such thermodynamic properties of binary mixtures of hydrocarbons (HCs) blended with nonflammable HFCs is important in solving the problem of the flammability of HCs, which otherwise are promising alternative fluids in refrigerationbased applications, as they have zero ozone-depletion potential and negligible global warming potential.

Prof. S. I. Sandler (University of Delaware, Newark, Delaware, USA) discussed the use of computational chemistry to make phase behavior predictions. He illustrated his talk with two examples of ab initio quantum mechanical calculation methods. The first example used interaction energies determined from quantum mechanics to compute thermodynamic properties by molecular simulation. In the second example, the chemical potential for dense fluids was calculated in Monte Carlo simulations in a Gibbs ensemble, as a result of moving molecules from a gas-like box to a liquid-like box.

Prof. Th. de Loos (Delft University of Technology, The Netherlands) gave examples of complex fluid phase behavior to be observed for binary systems of alkanes, ethers, alkanols, and ammonia with halocarbons. He showed that systematic changes in the type of behavior are found in families of a light gas (e.g., a halocarbon) with members of a homologous series. Prof. G. M. Schneider (University of Bochum, Germany) described the continuity that exists between phase equilibria in fluid mixtures (liquid-liquid, liquid-gas, and gas-gas), and illustrated it with examples where a particular fluid (e.g., a fluorocompound) was combined with a second fluid that was systematically altered in molecular mass, size, shape, structure, or polarity, by selecting compounds from different homologous series.

Prof. E. Wilhelm (University of Vienna, Austria) spoke about the importance of molecular models for interpreting thermodynamic properties. He showed how data analysis had led to information on the rotational behavior of tetrachloromethane, on the transgauche equilibrium in 1,2-dihaloethanes, and on the significantly enhanced solubility of oxygen in perfluorinated hydrocarbons, which is of interest for artificial blood systems. Dr. A. Laesecke (National Institute of Standards and Technology, Boulder, Colorado, USA) reported observations of the dielectric behavior of ten binary and ternary mixtures composed of difluoromethane, 1,1,1,2-tetrafluoroethane, pentafluoroethane, and propane. Such results give insights into the molecular interactions of these systems and are important for the development of more realistic potential models for property calculation.

Prof. G. Scalabrin (Universita di Padova, Italy) demonstrated "conformality" within a corresponding states format in different thermodynamic functions for fluids belonging to the alkane and halogenated alkane series. A volumetric model, a heat of vaporization model, and two further models, for enthalpy and entropy, for pure fluids and mixtures provide a high level of prediction accuracy with the given scaling parameters.

There were an additional 27 oral communications, which included measurements on pure fluids [density for compressed difluoromethane; vapor-liquid equilibria for difluoromethane; thermodynamics of vaporiza tion and heat capacities of hydrofluorocarbons; activity coefficients at infinite dilution in perfluoroalkanes; and dipole moment of liquid HFC-227ea (1,1,1,2,3,3,3- heptafluoropropane)] and on mixtures (high-pressure vapor-liquid equilibria for 1,1,1,2-tetrafluoroethane + propane; thermodynamic properties of refrigerants + lubricant oils).

Results were presented for theoretical calculations (perturbation theory applied to thermodynamic properties of alkane + haloalkane systems, thermodynamic and dielectric properties of fluoromethanes from Monte Carlo simulations, prediction of thermodynamic properties of mixtures of alternative refrigerants by molecular simulations, and new intermolecular potentials for chlorofluorocarbon fluids), and other papers were concerned with data correlation and prediction (use of density data to calculate an equation of state through a new extended corresponding states-neural network technique, correlation and prediction of transport properties based on consideration of hard-sphere models, and viscosity equations for refrigerants based on an extended corresponding states model).

A poster discussion session was held for the 60 poster presentations, and the workshop closed with a panel discussion of the main points of the workshop. The proceedings of this workshop will be published as a special issue of Fluid Phase Equilibria.

This highly successful workshop, which attracted about 120 participants, was excellently organized by Professor D. Richon (École Nationale Supérieure des Mines de Paris) and his Scientific and Local Organizing Committees. A followup workshop, to be organized by Profs. U. K. Deiters (University at Cologne, Germany) and M. J. Assael (Aristotle University, Thessaloniki, Greece), is planned for July-August 2002 in Rostock, Germany.

Dr. John H. Dymond (Department of Chemistry, University of Glasgow, University Avenue, Glasgow, Scotland G12 8QQ, UK; E-mail: johnd@chem.gla.ac.uk), Secretary of the IUPAC Commission on Thermodynamics (I.2), has submitted the following report:

 

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