Effect Of Supercritical CO Research Articles

Effects of Supercritical CO2 Conditioning on Cross-Linked Polyimide Membranes

The effects of supercritical CO2 (scCO2) conditioning on high-performance cross-linked polyimide membranes is examined through gas permeation and sorption experiments. Under supercritical conditions, the cross-linked polymers do not exhibit a structural reorganization of the polymer matrix that was observed in the non-cross-linkable, free acid polymer. Pure gas permeation isotherms and mixed gas permeabilities and selectivities show the cross-linked polymers to be much more stable to scCO2 conditioning than the free acid polymer. In fact, following scCO2 conditioning, the mixed gas CO2 permeabilities of the cross-linked polymers increased while the CO2/CH4 separation factors remained relatively unchanged. This response highlights the stability and high performance of these cross-linked membranes in aggressive environments. In addition, this response reveals the potential for the preconditioning of cross-linked polymer membranes to enhance productivity without sacrificing efficiency in practical applicatio...

Modelling biofilm growth in the presence of carbon dioxide and water flow in the subsurface

The concentration of greenhouse gases – particularly carbon dioxide (CO 2) – in the atmosphere has been on the rise in the past decades. One of the methods which have been proposed to help reduce anthropogenic CO 2 emissions is the capture of CO 2from large, stationary point sources and storage in deep geological formations. The caprock is an impermeable geological layer which prevents the leakage of stored CO 2, and its integrity is of utmost importance for storage security. Due to the high pressure build-up during injection, the caprock in the vicinity of the well is particularly at risk of fracturing. Biofilms could be used as biobarriers which help prevent the leakage of CO 2 through the caprock in injection well vicinity by blocking leakage pathways. The biofilm could also protect well cement from corrosion by CO 2-rich brine. The goal of this paper is to develop and test a numerical model which is capable of simulating the development of a biofilm in a CO 2 storage reservoir. This involves the description of the growth of the biofilm, flow and transport in the geological formation, and the interaction between the biofilm and the flow processes. Important processes which are accounted for in the model include the effect of biofilm growth on the permeability of the formation, the hazardous effect of supercritical CO 2 on suspended and attached bacteria, attachment and detachment of biomass, and two-phase fluid flow processes. The model is tested by comparing simulation results to experimental data.

Effects of Supercritical CO2 Conditioning on Un-Cross-Linked Polyimide Membranes for Natural Gas Purification

ADVERTISEMENT RETURN TO ISSUEPREVAddition/CorrectionORIGINAL ARTICLEThis notice is a correctionEffects of Supercritical CO2 Conditioning on Un-Cross-Linked Polyimide Membranes for Natural Gas PurificationAdam M. Kratochvil, Shilpa Damle-Mogri, and William J. Koros*Cite this: Macromolecules 2010, 43, 5, 2642Publication Date (Web):January 20, 2010Publication History Received10 January 2010Published online20 January 2010Published inissue 9 March 2010https://doi.org/10.1021/ma902847wCopyright © 2010 American Chemical SocietyRIGHTS & PERMISSIONSArticle Views544Altmetric-Citations1LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (537 KB) Get e-AlertsSUBJECTS:Membranes,Natural resources,Polyimides,Purification Get e-Alerts

Effects of Supercritical CO2Conditioning on Un-Cross-Linked Polyimide Membranes for Natural Gas Purification

The effects of supercritical CO2 (scCO2) conditioning are examined through changes in gas permeability and solubility for 6FDA-based polyimide membranes. At pressures above the supercritical point, both CO2 permeability and sorption unexpectedly decline, suggesting a structural rearrangement of the polymer facilitated by the presence of a highly soluble species. High-pressure permeability isotherms for He and N2 do not exhibit a similar decline. Upon depressurization, a typical hysteresis is not observed; rather, CO2 permeability remains at reduced levels compared to the original pressurization. Permeability isotherms of the conditioned polymer show a reduction in transport compared to unconditioned samples; however, sorption isotherms show an increase in penetrant solubility following scCO2 conditioning. Pre- and post-CO2/CH4 mixed gas permeation testing at 35 °C shows a reduction in membrane permeability with a corresponding increase in the separation factor after scCO2 conditioning.

Effects of supercritical CO 2 fluid parameters on chemical composition and yield of carotenoids extracted from pumpkin

Pumpkin is a traditional food that is grown extensively worldwide and is believed to be beneficial to human health due to its high contents of carotenoids. The carotenoids in pumpkin were extracted by organic solvents and by supercritical carbon dioxide (SC-CO 2), and then they were identified, quantified, and compared. β-carotene (31 to 40 g per 100 g of total carotenoids) was the predominate carotenoid in pumpkin. Lutein and lycopene contents were much higher in SC-CO 2 extracts than those in organic solvent extract. Cis-β-carotene increased by more than two times in the SC-CO 2 extracts, even at a relatively low temperature of 40 °C, over those in the solvent extracts, indicating both enhanced solubility and isomerization from trans- to cis-β-carotene. The influences of modifier (10 mL/100 mL), temperature (40–70 °C), and pressure (25–35 MPa) of SC-CO 2 extraction on the change of carotenoid yields were also investigated. The highest yield (109.6 μg/g) was obtained at 70 °C and 35 MPa, with a 73.7% recovery. Selective extraction could be achieved by adjusting the temperature and pressure. Higher proportions of all- trans-β-carotene extracts were achieved at 40 °C under both 25 MPa and 35 MPa conditions. In order to extract more cis-isomers, a higher temperature of 70 °C was preferred.

Effects of supercritical CO 2 and N 2O pasteurisation on the quality of fresh apple juice

Supercritical pasteurisation is receiving increasing attention as an alternative technology for foodstuff pasteurisation, but often the possible effects on the perceptible quality are not sufficiently considered. To address this latter issue, besides standard microbial analysis, we here investigate the impact of CO 2/N 2O supercritical pasteurisation (100 bar, 36 °C and 10 min treatment time) on the quality traits of fresh apple juice, linked to consumer perception. Discriminative sensory analysis (triangle test) and basic chemical characterization (total solids, sugars, organic acids, polyphenols) could not clearly demonstrate any induced modification of the treated juice, while head space analysis of volatile compounds (both by GC–MS and PTR–MS) indicated a general depletion of the volatile compounds that must be considered in the development of a stabilization method based on supercritical gases.

614 超臨界二酸化炭素による高分子溶融体の可塑化効果の測定と推算(1)(OS6-4 非ニュートン流体の流動現象,OS6 非ニュートン流体の流動現象,オーガナイズドセッション)

614 超臨界二酸化炭素による高分子溶融体の可塑化効果の測定と推算(1)(OS6-4 非ニュートン流体の流動現象,OS6 非ニュートン流体の流動現象,オーガナイズドセッション)

Effect of Supercritical CO2 in Modified Polystyrene 3D Latex Arrays

The effect of supercritical CO(2) (scCO(2)) in 3D latex arrays formed by monodispersed particles of polystyrene (PS), PS cross-linked with divinylbenzene (PS-DVB), and PS block copolymers with 2-hydroxyethyl methacrylate (PS-HEMA), methacrylic acid (PS-MA), acrylic acid (PS-AA), itaconic acid (PS-IA), and a mixture of methacrylic and itaconic acid (PS-IA-MA) has been studied. Sorption of CO(2) into the polymer particles leads to a decrease in the glass transition temperature of the polymer and the swelling of the particles and induces their coalescence. 3D-latex arrays of the former compositions were treated in scCO(2) at temperatures and pressures ranging from 40 to 80 degrees C and from 85 to 197 bar, respectively. The effect of CO(2) on the polymeric template was assessed by scanning electron microscopy and N(2) adsorption analysis. Bare PS and PS-HEMA particles sintered readily in scCO(2) at 40 degrees C and 85 bar. On the other hand, particles containing carboxylic acid groups on their surface (PS-MA, PS-AA, PS-IA, and PS-IA-MA) were, at the same temperature and pressure, more resistant to the CO(2) treatment. For a given polymer composition, the sorption of CO(2) inside the polymer particles, the swelling, and the degree of coalescence depend on the pressure, temperature, and time of the CO(2) treatment. Analysis of the pore size distributions from the N(2) adsorption data has allowed us to quantify the degree of coalescence of the particles in the matrix. By careful control of the experimental variables, the coalescence of the 3D latex array could be finely tuned using CO(2).

Modification of morphology of polycarbonate/thermoplastic elastomer blends by supercritical CO 2

The effect of supercritical CO 2 on the morphological features of blends of polycarbonate and a commercial thermoplastic elastomer was investigated. The as-prepared films of the blend showed phase separated domains of the elastomer. With the combination of pressure and temperature, the large domains were “burst” into smaller domains. Temperatures higher than the critical temperature are required to cause any change in the morphology. The size distribution of the elastomer domains is effectively narrowed by the supercritical CO 2 treatment. The time of exposure also plays a role. It was also seen that above 60 °C, crystallization of polycarbonate begins. Based on the previous work on this system, it is proposed that enhancement of elongation, Young’s modulus and abrasion resistance would occur due to the reduction in the domain size and distribution.

The effect of supercritical CO 2 as a reversible plasticizer and foaming agent on the hot stage extrusion of itraconazole with EC 20 cps

The aim of the current research project was to explore the possibilities of combining pressurized carbon dioxide with hot stage extrusion during manufacturing of solid dispersions of itraconazole and ethylcellulose 20 cps (EC 20 cps), to evaluate the ability of the pressurized gas to act as a reversible plasticizer and to produce a foamed extrudate. The physicochemical characteristics of the extrudates with and without injection of carbon dioxide were evaluated with reference to the morphology of the solid dispersion, release characteristics of the drug, and particle properties. Carbon dioxide acted as a plasticizer for itraconazole/EC 20 cps, reducing the processing temperature during the hot stage extrusion process. The macroscopic morphology changed to a foam-like structure due to expansion of the carbon dioxide at the extrusion die. This resulted in increased specific surface area and porosity and as a consequence milling efficiency was improved.

Transesterification reaction catalysed by Novozym 435 in supercritical carbon dioxide

Transesterification reaction between a substrate having two functional groups (ethylene glycol) with ethyl acetate in the presence of lipase Novozym 435 was carried out to study the effect of supercritical CO 2 (scCO 2) on the conversion and selectivity of the reaction. It was demonstrated that in the presence of scCO 2 the equilibrium conversion could be considerably higher than that in the absence of scCO 2. scCO 2 could also enhance the selectivity of ethylene glycol monoacetate (EGMA) and suppress the formation of ethylene glycol diacetate (EGDA), and selectivity could be tuned by CO 2 pressure.

Supercritical carbon dioxide essential oil extraction of Lamiaceae family species: Mathematical modelling on the micro-scale and process optimization

Abstract In this paper the essential oil supercritical carbon dioxide extraction from leaves of Lamiaceae family species was studied. Recent investigations of Lamiaceae family essential oil storage have shown that most of the oil is found in peltate glandular trichomes on the leaf surface. The effect of supercritical CO 2 on the peltate glands was investigated by Scanning Electron Microscopy. It was observed that exposure to supercritical CO 2 led to disruption of the peltate glands and essential oil release. This phenomenon was used as a basic hypothesis of the mathematical model of the supercritical fluid extraction with CO 2 . The model was applied to simulate basil, rosemary, marjoram and pennyroyal supercritical CO 2 extraction on the existing experimental data. An average deviation from the experimental data was less than 0.83%. The model results indicated a possibility of a decrease in the supercritical CO 2 consumption by modified and optimized processing of Lamiaceae family herbaceous material.

Effect of supercritical CO 2 as the organic solvent on cap rock sealing performance for underground storage

Supercritical CO 2 fluid is capable of extracting organic matter from rocks. Although the sealing performance of cap rock is essential for CO 2 underground storage, typical cap rock such as shale or mudstone usually contains organic matter. To determine how well cap rocks can seal supercritical CO 2, cap rock samples from the Nagaoka injection test site were treated with supercritical CO 2, and then the porosity and pore radius distribution of the samples were measured by mercury porosimetry. The results showed that the pore radius distributions slightly shifted to a larger size after treatment, while the porosity and permeability changed less than 1%.

Effect of supercritical CO2 on bulk hydrogenation of nitrile butadiene rubber catalyzed by RhCl(PPh3)3

AbstractThe effect of supercritical (SC) CO2 on the bulk hydrogenation of NBR entrapped with the catalyst (RhCl(PPh3)3) was investigated under various reaction times, reaction temperatures, hydrogen pressures and loadings of the catalyst and the thicknesses of the polymer films. CO2 helps in improving the transport behaviour of catalyst in polymer matrices, as well as helping to move catalyst into or out of the polymer. A method for the measurement of the dissolution extent or the apparent solubility of the Rh based catalyst in SC‐CO2 was developed. It is found that high temperatures and high SC‐CO2 densities would enhance the apparent solubility. Cosolvents, such as acetone, are also found to increase the apparent solubility. Details on the hydrogenation process are also presented.

Effect of supercritical CO 2 on morphology of compatible crystalline/amorphous PEO/PMMA blends

The effect of supercritical CO 2 on the morphological structure of compatible crystalline/amorphous poly(ethylene oxide) (PEO)/poly(methyl methacrylate)(PMMA) blends was investigated by means of small angle X-ray scattering (SAXS) with the measurement of absolute scattering intensity. The morphological structure of PEO/PMMA exhibited a considerable change upon CO 2 treatment as demonstrated by the drastic increase of scattering intensity, or the enhancement of electron density contrast between the crystalline and amorphous layers in the lamellar stacks, resulting from the swelling of amorphous PEO via the incorporation of CO 2 into the interlamellar (IL) regions. Upon CO 2 treatment, both the crystal and amorphous layer thickness ( l c and l a, respectively) were increased with the extents depending on the blend composition. The increasing of l a upon CO 2 treatment was decreased with increasing PMMA content, suggesting that PEO was much easier to be swollen by CO 2 than PMMA. Compared with the increase of l a, the increase of l c was much more significant and was attributed to the occurrence of melting and recrystallization during CO 2 treatment that led to thicker PEO crystals caused by an increased crystal surface free energy. The measured electron density contrast revealed that the distance of segregation in the PEO/PMMA blends involved the extralamellar segregation before CO 2 treatments and the swelling of IL region dominated the drastic increase of scattering intensity after CO 2 treatments. The finding of extralamellar morphology was consistent with the magnitude of volume fraction of lamellar stacks in the blends. The CO 2 treatment could increase the distance of segregation for neat PEO and PEO-rich blends. The lamellar size distribution appeared to be broader and the lamellar stacks more disorganized for the blends after CO 2 treatments according to SAXS one-dimensional correlation function profiles.

Effects of Supercritical CO2 Drying and Photoresist Strip on Low-k Films

AbstractFuture interlayer dielectric (ILD) requirements necessitate reductions in dielectric constant to 2.1 within four years. Due to gaseous-like transport properties and near liquid-like densities, supercritical methods have been developed to dry and strip resist from these highly porous materials. Although a non-polar molecule, the solvating capability of supercritical CO2 (SCCO2) can be tailored by varying pressure, temperature, and co-solvents. This flexibility has been employed to remove photoresist and moisture from porous low-k films. The results of these experiments have been characterized using FTIR, ellipsometry, and SEM.

Corrosive effects of supercritical carbon dioxide and cosolvents on metals

With the eventual phase-out of chlorofluorocarbons and hydrochlorofluorocarbons, and restrictive regulations concerning the use of other volatile organic compounds as cleaning solvents, it is essential to seek new, environmentally acceptable cleaning processes. We are investigating supercritical carbon dioxide (C02) as an alternative solvent for precision cleaning of machined metal parts in governmental and industrial cleaning processes. The compatibility of metals in supercritical-fluid cleaning media with respect to corrosion must be addressed. In this work, a screening study of the corrosive effects of supercritical CO 2 and several supercritical cosolvents on selected metals was conducted. Sample coupons of stainless steel (grades 304LSS, 316SS), aluminum (grades 2024, 6061, 7075), carbon steel (1018), and copper (CDA 101) were statically exposed to pure supercritical C0 2, water-saturated supercritical C02, 10 wt % methanol/CO 2 cosolvent, and 4 wt % tetrahydrofurfuryl alcohol (THFA)/C0 2 at 24,138 kPa (3500 psig) and 323 K (50 °C) for 24 h. Gravimetric analysis and magnified visual inspection of the coupons were performed before and after the exposure tests. Surface analyses including electron microprobe analysis (EMPA), X-ray photoelectron spectroscopy (XPS), and Auger electron spectroscopy (AES) were done where visual and gravimetric changes were indicative of corrosive attack. The metal alloys were found to be compatible with the supercritical test media barring a few exceptions. Corrosive attack was observed on 1018 carbon steel in the water-saturated CO 2 environment, and also on 2024 aluminum and CDA 101 copper, both in the 10 wt % methanol-CO 2 cosolvent. The results of all compatibility testing are reported, and hypotheses are formed in an attempt to explain possible corrosion mechanisms.

Effect of Supercritical CO2 on Myrosinase Activity and Glucosinolate Degradation in Canola

The effect of supercritical carbon dioxide (SC-CO2) extraction conditions (temperature, pressure, extraction time, and moisture content of the samples) on the myrosinase activity and glucosinolate hydrolysis in flaked and whole canola seeds was studied. Combined effects of high temperature (75 °C), pressure (62.1 MPa), and moisture (∼20% w/w) were necessary to achieve 90% enzyme inactivation in canola flakes in 3 h. Similar extraction conditions resulted in only 44% enzyme inactivation in whole canola seeds. Significant glucosinolate degradation was observed after 5 h of extraction of low moisture content (8.5% w/w) whole canola seeds. Glucosinolate degradation in canola flakes was minimal at all moisture levels studied. Therefore, myrosinase inactivation prior to SC-CO2 extraction of canola flakes may not be necessary. However, the presence of enzyme activity in canola extracted at low moisture or temperature should be taken into account for further utilization of meal. Keywords: Supercritical CO2; myros...