Thermodynamic Aspects of Supercritical Fluids Processing: Applications of Polymers and Wastes Treatment F. Cansell, S. Rey, P. Beslin To cite this version: F. Cansell, S. Rey, P. Beslin. Thermodynamic Aspects of Supercritical Fluids Processing: Applications of Polymers and Wastes Treatment. Revue de l’Institut Français du Pétrole, EDP Sciences, 1998, 53 (1), pp.71-98. 10.2516/ogst:1998010. hal-02078897 HAL Id: hal-02078897 https://hal.archives-ouvertes.fr/hal-02078897 Submitted on 25 Mar 2019 HAL is a multi-disciplinary open access L’archive ouverte pluridisciplinaire HAL, est archive for the deposit and dissemination of sci- destinée au dépôt et à la diffusion de documents entific research documents, whether they are pub- scientifiques de niveau recherche, publiés ou non, lished or not. The documents may come from émanant des établissements d’enseignement et de teaching and research institutions in France or recherche français ou étrangers, des laboratoires abroad, or from public or private research centers. publics ou privés. THERMODYNAMIC ASPECTS OF SUPERCRITICAL FLUIDS PROCESSING: APPLICATIONS TO POLYMERS AND WASTES TREATMENT F. CANSELL and S. REY ASPECTS THERMODYNAMIQUES DES PROCƒDƒS METTANT EN ÎUVRE DES FLUIDES SUPERCRITIQUES : CNRS, Université Bordeaux I1 APPLICATIONS AUX TRAITEMENTS DES POLYMéRES ET DES DƒCHETS P. BESLIN La mise en Ïuvre des fluides supercritiques est d'un intŽr•t crois- sant dans de nombreux domaines : pour la sŽparation (sŽparation 2 APESA et purification en pŽtrochimie, industrie alimentaire) et la chroma- tographie par fluides supercritiques (sŽparation analytique et prŽ- paratoire, dŽtermination des propriŽtŽs physicochimiques), comme milieux rŽactifs aux propriŽtŽs continžment ajustables allant du gaz au liquide (polyŽthyl•ne de faible densitŽ, Žlimination des dŽchets, recyclage des polym•res), en gŽologie et en minŽralogie (volcano- logie, Žnergie gŽothermique, synth•se hydrothermique), dans la formation des particules, fibres et substrats (produits pharmaceu- tiques, explosifs, rev•tements), pour le sŽchage des matŽriaux (gels). Cet article prŽsente les propriŽtŽs physicochimiques exception- nelles des fluides supercritiques en rapport avec leurs applications en ingŽnierie. Apr•s un bref rappel des concepts fondamentaux relatifs au comportement critique des fluides purs, nous dŽvelop- pons d'une mani•re plus dŽtaillŽe les propriŽtŽs physicochimiques ajustables des fluides dans le domaine supercritique. La deuxi•me partie de lÕarticle dŽcrit les applications en ingŽnierie des fluides supercritiques relatives aux rŽactions chimiques et au traitement des polym•res. Chaque prŽsentation d'application est divisŽe en deux parties : la premi•re rappelle les concepts de base et le contexte gŽnŽral ainsi que les propriŽtŽs physicochimiques, la seconde dŽveloppe les applications en ingŽnierie se rapportant au domaine concernŽ. THERMODYNAMIC ASPECTS OF SUPERCRITICAL FLUIDS PROCESSING: APPLICATIONS TO POLYMERS AND WASTES TREATMENT Supercritical fluid processes are of increasing interest for many fields: in supercritical fluid separation (petroleum-chemistry (1) Institut de chimie de la mati•re condensŽe de Bordeaux separation and purification, food industry) and supercritical fluid Ch‰teau Brivazac, 33608 Pessac Cedex - France chromatography (analytical and preparative separation, determination of physicochemical properties); as reaction media (2) P™le Environnement Sud Aquitaine, with continuously adjustable properties from gas to liquid (low- HŽlioparc, 64000 Pau - France density polyethylene, waste destruction, polymer recycling); in REVUE DE L’INSTITUT FRANÇAIS DU PÉTROLE VOL. 53, N° 1, JANVIER-FÉVRIER 1998 71 THERMODYNAMIC ASPECTS OF SUPERCRITICAL FLUIDS PROCESSING: APPLICATIONS TO POLYMERS AND WASTES TREATMENT geology and mineralogy (volcanoes, geothermal energy, INTRODUCTION hydrothermal synthesis); in particle, fibber and substrate formations (pharmaceuticals, explosives, coatings); in drying The capability of some supercritical fluids to replace materials (gels). toxic industrial solvents, the ability of tuning solvent This paper presents the unusual physicochemical properties of supercritical fluids in relation to their engineering applications. After characteristics for highly specific separation or a short report of fundamental concepts of critical behavior in pure reactions and the possibility to make new materials at fluids, we develop in more details the tunable physicochemical mild conditions are the main considerations which lead properties of fluid in the supercritical domain. The second part of to the current industrial and scientific interest in this paper describes the engineering applications of supercritical supercritical fluids. Often viewed as “dense gases”, fluids relevant of chemical reactions and polymer processing. Each application presentation is divided in two parts: the first one recalls these fluids possess physicochemical properties, such the basic concepts including general background, physicochemical as density, viscosity or diffusivity, which are properties and the second one develops the engineering intermediate between those of liquids and gases, as applications relevant of the advocated domain. outlined in Table 1. ASPECTOS TERMODINçMICOS DEL TRATAMIENTO DE TABLE 1 LOS FLUIDOS SUPERCRêTICOS : APLICACIONES PARA Characteristic magnitudes of thermophysical properties of fluids LOS TRATAMIENTOS DE LOS POLêMEROS Y DE LOS RESIDUOS Liquid Supercritical Gas* La implementaci—n de los fluidos supercr’ticos presenta un interŽs . -3 cada vez mayor en numerosos campos : para la separaci—n r (kg m ) 1000 100-800 1 (separaci—n y purificaci—n en petroqu’mica, industria alimentaria) y h (Pa.s) 10-3 10-5-10-4 10-5 la cromatograf’a de los fluidos supercr’ticos (separaci—n anal’tica y Dw (m2.s-1)10-9 10-8 10-5 preparatoria, determinaci—n de las propiedades fisicoqu’micas) ; en los medios reactivos con propiedades continuamente Symbols used: r for density; h for viscosity; D for diffusion coefficient: ajustables, que van desde el gas l’quido (polietilenos de baja * at ambient conditions; w for small-molecule solute. densidad, eliminaci—n de los residuos, reciclado de los pol’meros) ; en geolog’a y en mineralog’a (vulcanolog’a, energ’a geotŽrmica, s’ntesis hidrotŽrmica) ; en la formaci—n de part’culas, fibras y Supercritical fluid processes are of increasing interest substratos (productos farmacŽuticos, explosivos, revestimientos) ; for many fields [1] such as supercritical fluid separation para los materiales deshidratantes (geles). (petroleum-chemistry separation and purification, En este art’culo se presentan las excepcionales propiedades food industry) [2, 3, 4, 5] and supercritical fluid fisicoqu’micas de los fluidos supercr’ticos con respecto a sus aplicaciones en ingenier’a. Tras un breve resumen de los chromatography (analytical and preparative separation, conceptos fundamentales relativos al comportamiento cr’tico de determination of physicochemical properties) [6] los fluidos puros, hemos desarrollado con mayor detalle las and [7]. Supercritical fluids are used as reaction media propiedades fisicoqu’micas ajustables de los fluidos en el aspecto with continuously adjustable properties from gas to supercr’tico. En la segunda parte del art’culo se describen las liquid (low-density polyethylene, waste destruction, aplicaciones en ingenier’a de los fluidos supercr’ticos relativas a polymer recycling) [8, 9, 10, 11, 12, 13], in geology las reacciones qu’micas y para el tratamiento de los pol’meros : en la primera se hacen destacar los conceptos b‡sicos y el contexto and mineralogy (volcanoes, geothermal energy, general as’ como las propiedades fisicoqu’micas y, en la segunda hydrothermal synthesis) [14], in formation of particles, parte, se desarrollan las aplicaciones en ingenier’a referentes al fibbers and substrates (pharmaceuticals, explosives, aspecto correspondiente. coatings) [15, 16, 17, 18] or in drying materials (gels) [19] and [20]. The further development of supercritical fluid applications depends both on the ability to exploit their unusual properties towards making products with characteristics and specifications that cannot be obtained by other means and on the evolution of financial, legislative and even psychological aspects which may become decisive elements. In this paper, we present the unusual physicochemical properties of REVUE DE L’INSTITUT FRANÇAIS DU PÉTROLE VOL. 53, N° 1, JANVIER-FÉVRIER 1998 72 THERMODYNAMIC ASPECTS OF SUPERCRITICAL FLUIDS PROCESSING: APPLICATIONS TO POLYMERS AND WASTES TREATMENT supercritical fluids in relation to their engineering Each point of this surface corresponds to a state of applications. After a short report of fundamental the system. Generally, to study the thermodynamic concepts of critical behavior in pure fluids, we develop behavior of a system, it is easier to use only in more details the tunable physicochemical properties two variables and so to work in a two-dimensional of fluids in the supercritical domain. The second part of space such as (P, V ) (Clapeyron diagram) or (P, T ) this paper describes the engineering applications of (see section 1.2, Fig. 3). supercritical fluids relevant to watses treatment and On the phase surface presented on Figure 1, the polymer processing. Each application presentation is supercritical domain corresponds to a pressure and a divided in two parts: the first one recalls the basic temperature superior to the critical coordinates of the concepts including general background and physico-