Search results for "Supercritical"
showing 10 items of 236 documents
NOVEL PROCESSES FOR THE MODIFICATION AND THE STERILIZATION OF MACROMOLECULAR MATRICES
Combined Oxidation-Gasification system for waste treatment with supercritical water: LCA and performance analysis
2020
In this study the environmental performance of a first of a kind integrated process based on supercritical water gasification and supercritical water oxidation, was evaluated using Life Cycle Assessment (LCA). The process was applied to the treatment of carbon black and used oil as model waste. Mass and energy balances were performed using Aspen Plus, and the environmental assessment was carried out through SimaPro. For the analysis was chosen a “From cradle to grave” approach, considering impact categories like climate change, ozone depletion, human toxicity, particulate matter, land use, resource depletion and others relevant indicators. The environmental profile of SCW-GcO process was co…
PLANT FOR WASTE DISPOSAL AND ASSOCIATED METHOD
2016
Described herein is a plant for the disposal of wastes including: a supercritical water oxidation reactor (SCWO), a supercritical water gassification reactor (SCWG), a feeding system configured for feeding at least two organic currents of wastes to said SCWO and SCWG and configured for feeding at least one aqueous flow within said plant, wherein said feeding system is configured for feeding said at least one aqueous current with a series flow throw said SCWO and SCWG and wherein said feeding system is furthermore configured for feeding said at least two organic currents of wastes with a parallel flow through said SCWO and SCWG and so as to selectively feed each of said organic currents of w…
USE OF SUPERCRITICAL CO2 AS DISSOLVED GAS FOR THE ATOMIZATION OF ETHANOL
2011
Supercritical dissolved gas atomization (SDGA) is an atomization process in which carbon dioxide at temperatures and pressures above its critical point is used as atomizing gas. In this work SDGA has been experimentally studied when ethanol is used as the liquid to be atomized. The spray characteristics in terms of droplets size and distribution have been investigated using a droplet size analyzer based on a laser diffraction method. Very narrow droplet size distributions were produced down to 2.5 μm. The main parameter that influences the droplets size is the gas to liquid mass ratio. From the point of view of the atomization mechanism, mean droplet diameter is mainly influenced by the two…
Power Consumption in Uncovered Unbaffled Stirred Tanks: Influence of the Viscosity and Flow Regime
2013
Notwithstanding the increasing industrial interest toward unbaffled tanks, available experimental information on their behavior is still scant, even for basic quantities such as the mechanical power drawn. In this work, the influence of the Reynolds and Froude numbers on the power consumption characteristics is presented for unbaffled stirred tanks operating both in nonaerated conditions (subcritical regime) and in aerated conditions (supercritical regime), i.e., when the free surface vortex has reached the impeller and the gas phase is ingested and dispersed inside the reactor. Experimental results obtained at various liquid viscosities show that power numbers obtained in subcritical condi…
Catalytic Functionalization of Methane and Light Alkanes in Supercritical Carbon Dioxide
2014
International audience; The development of catalytic methods for the effective functionalization of methane yet remains a challenge. The best system known to date is the so-called Catalytica Process based on the use of platinum catalysts to convert methane into methyl bisulfate with a TOF rate of 10−3 s. In this contribution, we report a series of silver complexes containing perfluorinated tris(indazolyl)borate ligands that catalyze the functionalization of methane into ethyl propionate upon reaction with ethyl diazoacetate (EDA) by using supercritical carbon dioxide (scCO2) as the reaction medium. The employment of this reaction medium has also allowed the functionalization of ethane, prop…
Supercritical hydrothermal synthesis of ZnO nanopowders beyond the critical point : understanding of nucleation and growth steps
2014
The supercritical hydrothermal synthesis of nanopowders (especially metal oxide) has been widely studied. To the best of our knowledge, no nanoparticle formation mechanism has been published yet. In this prospect, this study is dedicated to the understanding of metal oxide nanoparticle nucleation and growth mechanisms. For this purpose, zinc oxide is used as a model material. First, the influence of synthesis operating conditions such as pressure, temperature, pH, precursor concentrations and solution flow rates on particle morphological properties (size, particle size distribution or morphologies) has been investigated. Hence, two approaches have simultaneously been carried out. The first …
On the ionizing properties of supercritical carbon dioxide: uncatalyzed electrophilic bromination of aromatics
2014
Supercritical carbon dioxide (scCO2), a solvent with a zero dipole moment, low dielectric constant, and no hydrogen bonding behavior, is a suitable medium to perform the uncatalyzed electrophilic bromination of weakly activated aromatics with no interference of radical pathways. The ability of scCO2 to promote these reactions matches those of strongly ionizing solvents such as aqueous acetic and trifluoroacetic acids. Conversely, carbon tetrachloride, with similar polarity parameters to scCO2, leads exclusively to side chain functionalization. The strong quadrupole moment, and the acidic, but non basic, Lewis character of carbon dioxide, are proposed as key factors for the singular performa…
ChemInform Abstract: Epoxidation of Olefins with a Silica-Supported Peracid in Supercritical Carbon Dioxide under Flow Conditions.
2012
Anhydrous 2-percarboxyethyl-functionalized silica (2b), a recyclable supported peracid, is a suitable reagent to perform the epoxidation of alkenes 1 in supercritical carbon dioxide at 250 bar and 40 °C under flow conditions. This procedure simplifies the isolation of the reaction products and uses only carbon dioxide as a solvent under mild conditions. The solid reagent 2b can be easily recycled by a reaction with 30% hydrogen peroxide in an acid medium.
Epoxidation of Olefins with a Silica-Supported Peracid in Supercritical Carbon Dioxide under Flow Conditions
2012
Anhydrous 2-percarboxyethyl-functionalized silica (2b), a recyclable supported peracid, is a suitable reagent to perform the epoxidation of alkenes 1 in supercritical carbon dioxide at 250 bar and 40 °C under flow conditions. This procedure simplifies the isolation of the reaction products and uses only carbon dioxide as a solvent under mild conditions. The solid reagent 2b can be easily recycled by a reaction with 30% hydrogen peroxide in an acid medium.