Whatever the supercritical fluid is, the performance of structural materials is a key issue for industrial applications. An overview is carried out on the corrosion behavior of metallic metals and alloys under pressure and temperature conditions appropriate for supercritical fluids. Steels, including stainless steels, and nickel base alloys are the main alloys investigated in supercritical environments. In supercritical water (SCW), the review highlights how SCW density changes the corrosion mechanisms. Beside the density, temperature and impurities (especially chlorine) play key roles. SCW oxidation is promised to a strong development if corrosion issues are solved, as illustrated with the DELOS process (French acronym for destruction of organic fluids) applied to radioactive organics. At low temperatures, in supercritical fluids like supercritical CO2, authors observed that no corrosion occurs in pure fluids but the water content is a key parameter. Temperature, water and pollutants are the major factors leading to increase the uniform or localized corrosion rates. (C) 2016 Published by Elsevier B.V.

Nanofiltration using inorganic membranes was conducted to develop a continuous process in supercritical CO,. Inorganic membranes of various sizes (1, 5, 50, 300 kDa), materials (Al(2)O(3)/TiO(2)/ZrO(2), Al(2)O(3)/ZrO(2)/TiO(2)), and modules (one and three channels) were used for the experiments. The effects of fluid viscosity and density, membrane active layer thickness, number of channels, pore size, and the flux of a fluid were analyzed when supercritical CO(2) (sc-CO(2)) passed through the membrane. In the case of PE6100 surfactant, it was confirmed that SC-CO(2) passed through the membrane at a flow rate and transmembrane pressure (Delta P) greater than 10 mL/min and 0.04 MPa, respectively, although the size of the surfactant was larger than that of the membrane pore. The phenomena were proven to have been caused by the folding effect. In the case of microemulsions using NP-4 and H(2)O, it was confirmed that water adsorbed on the membrane surface passed through at Delta P greater than 0.7 MPa. Based on these findings, experiments were conducted to separate microemulsions and dispersions. The experimental results indicated that microemulsions achieved 47% separation efficiency and 90% surfactant recovery efficiency due to the displacement of metal ions through the water adsorbed on the membrane surface. Conversely, dispersions yielded high separation efficiency. Also, the correlation between the contaminant size and the membrane pore size was confirmed through SEM images.

We describe in this paper a process of filtration of highly viscous liquids assisted by pressurized CO2, and we present preliminary results obtained during the treatment of motor oils (two mineral oils and one used motor oil). Filtration and concentration runs are commentated in terms of permeate flux enhancement and metal retention. The behavior of these fluids during filtration exhibits significant discrepancies from the one observed with previously investigated model compounds. The permeate flux improvement is about 400% for mineral oils and about 200% for the used motor oil (PCO2 = 15 MPa, DELTAP = 1 MPa, T = 353 K, cutoff of the membrane: 300 kDa). The presence of many pollutants can explain the lower improvement in the latter case. The performance of the membrane with regard to the retention of metals is very satisfactory: in the case of zinc and copper, the separation is higher than 99.5%. The 32 h concentration run carried out at 393 K made it possible to regenerate 96% in mass of the used oil and to confine the majority of the metals in a black gum extremely viscous.

We report the synthesis of new gradient fluorinated copolymers with complexing groups and soluble in supercritical carbon dioxide (scCO(2)). Poly(1,1,2,2-tetrahydroperfluorodecyl acrylate-co-acetoacetoxyethyl methacrylate) (poly(FDA-co-AAEM)) and poly(1,1,2,2-tetrahydroperfluorodecyl acrylate-co-vinylbenzylphosphonic acid diethylester) (poly(FDA-co-VBPDE)) gradient copolymers were synthesized by reversible addition fragmentation chain transfer polymerization in a,a,a-trifluorotoluene. Poly(1,1,2,2-tetrahydroperfluorodecyl acrylate-co-vinylbenzylphosphonic diacid) (poly(FDA-co-VBPDA)) gradient copolymer was efficiently obtained by cleavage of the phosphonic ester groups of poly(FDA-co-VBPDE). The cloud points of these gradient copolymers in dense CO(2) were measured in a variable volume view cell at temperatures between 25 and 65 C. The gradient copolymers show very good solubility in compressed CO(2) with the decreasing order: poly(FDA-co-AAEM).:; poly(FDA-co-VBPDE) > poly(FDA-co-VBPDA). Following a green chemistry strategy, poly(FDA-co-AAEM) gradient copolymer was successfully synthesized in scCO(2) with a good control over number-average molecular weight and composition. (C) 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 5448-5460, 2009

The increasing interest of supercritical (SC) fluids for inorganic materials synthesis recently stimulated the development of innovative synthesis processes and strategies The supercritical CO(2) aided sol-gel process, developed for preparing various ceramic oxide powders with attractive applications in cosmetics, chromatography, catalysis or solid oxide fuel cells, usually suffer from both reproducibility problems and poor knowledge of the key parameters defining the final powder characteristics In the present work a specific effort has been put on the understanding of reaction mechanisms and process parameters like co-solvent polarity and ageing time of the starting solution, which appeared to play a crucial role for the control of powder characteristics Two different reaction mechanisms have been proposed to explain the formation of tetragonal yttria-doped zirconia powders by a batch process in either CO(2)/pentane or CO(2)/isopropanol mixtures The first mechanism corresponds to a CO(2) anti-solvent precipitation process while the other one is based on a condensation reaction as in the conventional sol-gel process This improved understanding in particle formation allows better control of powder characteristics and reproducibility (C) 2010 Elsevier Ltd All rights reserved

A novel "On-Stream Supercritical Fluid Deposition" (OS-SFD) process has been investigated in this work coupling the sal gel chemistry and a filtration/compression operation in supercritical CO2 (sc-CO2), for the production of uniform membranes on/in porous ceramic tubular supports. The versatility of this process allows both the direct formation of thin coatings on porous tubular membrane supports but also their internal modification. An attractive on-line control of the deposition process was operated by recording the transmembrane pressure evolution during membrane formation. Silica membranes were directly deposited on macroporous supports (155 mm long alpha-Al2O3, with 200 nm pore sizes) from TEOS derived sols dissolved in sc-CO2 and transported to the tubular support where the condensation/gelation and deposition occurred. The deposition mechanism has been correlated with the sol-gel transition in sc-CO2 conditions and the impact of the deposition temperature, sol formulation and sc-CO2 flow rate on the membrane characteristics (morphology, weight increase and single gas permeance) have been discussed. Supersaturation and precipitation of transported clusters followed by their condensation and gelation were found as key parameters controlling the silica-based membrane design and microstructure/compacity of the silica network. (C) 2013 Elsevier B.V. All rights reserved.