Differences in reactivity of pulverised coal in air (O2/N2) and oxy-fuel (O2/CO2) conditions

The reactivity of four pulverised Australian coals were measured under simulated air (O₂/N₂) and oxy-fuel (O₂/CO₂) environments using a drop tube furnace (DTF) maintained at 1673 K and a thermogravimetric analyser (TGA) run under non-isothermal (heating) conditions at temperatures up to 1473 K. The oxygen concentration, covering a wide and practical range, was varied in mixtures of O₂/N₂ and O₂/CO₂ in the range of 3 to 21 vol.% and 5 to 30 vol.%, respectively. The apparent volatile yield measured in CO₂ in the DTF was greater than in N₂ for all the coals studied. Pyrolysis experiments in the TGA also revealed an additional mass loss in a CO₂ atmosphere, not observed in a N₂ atmosphere, at relatively high temperatures. The coal burnout measured in the DTF at several O₂ concentrations revealed significantly higher burnouts for two coals and similar burnouts for the other two coals in oxy-fuel conditions. TGA experiments with char also revealed higher reactivity at high temperatures and low O₂ concentration. The results are consistent with a char–CO₂ reaction during the volatile yield experiments, but additional experiments are necessary to resolve the mechanisms determining the differences in coal burnout.     

Textural study of a coal from villanueva de rio y minas (sevilla,spain) and of samples prepared from it by acid and heat treatments

A coal with high inorganic matter content from the mine of Villanueva de Rio y Minas (Sevilla, Spain) (VRMO) was classified by following the ASTM norms as a high volatile matter A bituminous coal. The starting coal was treated either with HCl (VRMH) or thermally at 1000°C for 2 h (VRMOC), the resultant yield values (referred to as VRMO, dry) being, respectively, 97 and 79%; also VRMH was either treated with HNO₃ (VRMN) or HF (VRMF), and the yield values (referred to as VRMH, dry) of the process were then 95 and 59%. The textural characterization of samples was effected by adsorption of CO₂ at 273 K and of N₂ at 77 K, as well as by mercury porosimetry. VRMN presents the highest value of the apparent surface area (S_D-R=219 m² g^?1) (CO₂, 273 K) and of the specific surface area of mesopores and macropores (S_me+ma=5.2 m² g^?1) (N₂, 77 K), while the greatest value of the cumulative specific surface area of macropores (S_ma=1.2 m² g^?1) (mercury porosimetry) corresponds to VRMOC; S values are expressed on a per gram of original sample basis. The micropore volume accessible to CO₂ at 273 K increases in both the HCl and the HNO₃ treatment and decreases in the HF and heat treatments. The HCl and HNO₃ treatments produce an increase of the mesoporosity; the HF treatment seems to affect in a special way the mesoporous texture. Furthermore, the heat treatment gives rise to a notable development of the macroporosity.     

Effects of membrane thickness and heat treatment on the gas transport properties of membranes based on P84 polyimide

P84 polyimide membranes with thicknesses ranging from 6 to 310 μm were successfully fabricated by spin coating. The glass transition temperature of the P84 powder was found to be 315°C using differential scanning calorimetry, whereas its decomposition temperature was 536°C using thermogravimetric analysis. Scanning electron microscopy was used to examine the morphology of the membranes. The permeability of single gas (He, N₂, O₂, and CO₂) and the ideal selectivity of gas pair (O₂/N₂, He/CO₂, CO₂/N₂, and He/O₂), as a function of membrane thickness, were determined. The results showed that the permeability of a single gas increased with increasing membrane thickness, whereas the selectivity of a given gas pair was nearly independent of the membrane thickness. The average selectivity of O₂/N₂, He/CO₂, CO₂/N₂, and He/O₂ were found to be 8.2, 10.0, 12.9, and 15.8, respectively. The effects of heat treatment on the membrane morphology and gas transport properties were investigated for three annealing temperatures, i.e., 80°C, 200°C, and 315°C. The membrane annealed at 315°C was cracked due to the stress sustained either during heating or cooling, thereby resulting in little or no selectivity. The permeabilities of P84‐118 membrane (118 μm thickness) annealed at 80°C were 16.2, 0.196, 1.20, and 2.01 Barrer for He, N₂, O₂, and CO₂, respectively. The permeabilities of P84‐118 membrane annealed at 200°C decreased by 9.75%, 47.96%, 25.83%, and 30.85% for He, N₂, O₂, and CO₂, respectively, as compared with those at 80°C, whereas the ideal selectivities increased by 42.65%, 30.52%, 32.85%, and 21.63% for O₂/N₂, He/CO₂, CO₂/N₂, and He/O₂, respectively. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Pure and mixed gas permeation study of silica incorporated polyurethane-urea membrane modified by MOCA chain extender

Polyurethane-urea (PUU) nanocomposite membranes have been prepared using various loadings of silica (SiO₂) nanoparticles. A Novel PU was fabricated by a two-step bulk polymerization technique based on polycaprolactone (PCL), hexamethylene diisocyanate (HDI), and diamine chain extender, 4,4-methylenebis(2-chloroaniline) (MOCA). The FTIR spectra indicated that the extent of phase separation reduces with increasing SiO₂ content. The presence of crystal regions in the soft and hard segments was confirmed by DSC and XRD analyses. The obtained results illustrated a decrement in the gases' permeation in the presence of SiO₂ particles. By increasing the filler content up to 15 wt% and pressure of 8 bar, the gas permeation value of the CO₂, O₂, and N₂ decreased 36%, 54%, and 59%, respectively. However, the permselectivity of the CO₂/N₂ and O₂/N₂ increased considerably, 55% and 13% respectively. On the contrary, by raising the temperature, a dramatic augmentation in the permeability of all gases with a simultaneous reduction in the selectivity values of both gas pairs was revealed. Increasing the pressure led to a decrease in the permeability values of all membranes for O₂ and N₂, whereas the permeability for CO₂ increased with the pressure. Nevertheless, the selectivity values for the pair of gases increased (at a pressure of 10 bar, 1.66 and 1.17 times the neat PU for CO₂/N₂ and O₂/N₂, respectively). Furthermore, the permeability of the CO₂, O₂, and N₂ for the mixed gases was smaller than for pure ones at the same gas upstream pressure. Nonetheless, like the pure gas, the selectivity of both pair gases increased.     

Dynamic Distribution of HIG2A between the Mitochondria and the Nucleus in Response to Hypoxia and Oxidative Stress

Mitochondrial respiratory supercomplex formation requires HIG2A protein, which also has been associated with cell proliferation and cell survival under hypoxia. HIG2A protein localizes in mitochondria and nucleus. DNA methylation and mRNA expression of the HIGD2A gene show significant alterations in several cancers, suggesting a role for HIG2A in cancer biology. The present work aims to understand the dynamics of the HIG2A subcellular localization under cellular stress. We found that HIG2A protein levels increase under oxidative stress. H₂O₂ shifts HIG2A localization to the mitochondria, while rotenone shifts it to the nucleus. HIG2A protein colocalized at a higher level in the nucleus concerning the mitochondrial network under normoxia and hypoxia (2% O₂). Hypoxia (2% O₂) significantly increases HIG2A nuclear colocalization in C2C12 cells. In HEK293 cells, chemical hypoxia with CoCl₂ (>1% O₂) and FCCP mitochondrial uncoupling, the HIG2A protein decreased its nuclear localization and shifted to the mitochondria. This suggests that the HIG2A distribution pattern between the mitochondria and the nucleus depends on stress and cell type. HIG2A protein expression levels increase under cellular stresses such as hypoxia and oxidative stress. Its dynamic distribution between mitochondria and the nucleus in response to stress factors suggests a new communication system between the mitochondria and the nucleus.     

Flue gas treatment by activated carbon obtained from oil-fired fly ash

The treatment of the solid particulates derived from the combustion of heavy oils (that is, oil-fired fly ash) with acidic solutions (HCl and HF) followed by activation at 900 °C with CO₂ and then with O₂ (1%) in N₂ at 800 °C, produces activated carbon having high surface area values (measured both by N₂ adsorption at 77 K and by CO₂ adsorption at 273 K) and surface basic characteristics. This carbon appears to be suitable for SO₂ and NO_X adsorption and hence for industrial flue gas treatment processes. By submitting the activated carbon thus obtained to some adsorption/desorption cycles of gaseous mixtures having a similar composition to that of flue gases, its general characteristics (surface areas, sorbent properties etc.) change as expected of a typical activated carbon. Based on the results obtained, these particulate materials, produced in large amounts by heavy oil combustion, are assumed to be fully exploitable for flue gas treatment.     

Gas permeability of NH3‐plasma‐treated poly(methyl methacrylate) membranes

The effect of NH₃ plasma treatment on glassy poly(methyl methacrylate) (PMMA) membranes on the diffusion process for penetrant gases (CO₂, O₂, and N₂) was investigated from mean permeability data. The mean permeability coefficient for CO₂ definitely depended on the upstream pressure, whereas those for O₂ and N₂ remained constant regardless of the upstream pressure. For O₂ transport, the permeability increased a little with increasing treatment power, and for N₂ transport, it was not affected by the treatment power. For CO₂ transport, NH₃ plasma treatment promoted the transport of Langmuir mode, presumably through an increased Langmuir capacity constant for CO₂. NH₃ plasma treatment for PMMA membranes resulted in an increase in the separation factor of CO₂ relative to N₂ and in the permeability to CO₂. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 1068–1072, 2003     

Properties of char particles obtained under O2/N2 and O2/CO2 combustion environments

Pulverized coal combustion in O₂/N₂ and O₂/CO₂ environments was investigated with a drop tube furnace. Results present that the reaction rate and burn-out degree of O₂/CO₂ chars (obtained in O₂/CO₂ environments) are lower than that of O₂/N₂ chars (obtained in O₂/N₂ environments) under the same experimental condition. It indicates that a higher O₂ concentration in O₂/CO₂ environment is needed to achieve the similar combustion characteristic to that in O₂/N₂ environment. The main differences between O₂/N₂ and O₂/CO₂ chars rely on the pore structure determined by N₂ adsorption and chemical structure measured by FT-IR. For O₂/CO₂ char, the surface is thick and the pores are compact which contribute to the fragmentation reduction of particles burning in O₂/CO₂ environment. The organic functional group elimination rate from the surface of O₂/CO₂ chars is slower or delayed. The present research results might have important implications for further understanding the intrinsic kinetics of pulverized coal combustion in O₂/CO₂ environment.     

Similarity and differences in the oxidative dehydrogenation of C2–C4 alkanes over nano-sized VOx species using N2O and O2

The effect of O₂ and N₂O on alkane reactivity and olefin selectivity in the oxidative dehydrogenation of ethane, propane, n-butane, and iso-butane over highly dispersed VO_x species (0.79 V/nm²) supported on MCM-41 has been systematically investigated. For all the reactions studied, olefin selectivity was significantly improved upon replacing O₂ with N₂O. This is due to suppressing CO_x formation in the presence of N₂O. The most significant improving effect of N₂O was observed for iso-butane dehydrogenation: S(iso-butene) was ca. 67% at X(iso-butane) of 25%.Possible origins of the superior performance of N₂O were derived from transient experiments using ¹⁸O₂ traces. ¹⁸O¹⁶O species were detected in ¹⁸O₂ and ¹⁸O₂–C₃H₈ transient experiments indicating reversible oxygen chemisorption. In the presence of alkanes, the isotopic heteroexchange of O₂ strongly increased. Based on the distribution of labeled oxygen in CO_x and in O₂ as well as on the increased CO_x formation in sequential O₂–C₃H₈ experiments, it is suggested that non-lattice oxygen species (possibly of a bi-atomic nature) originating from O₂ are non-selective ones and responsible for CO_x formation. These species are not formed from N₂O.     

Preparation of C/CMS composite membranes derived from Poly(furfuryl alcohol) polymerized by iodine catalyst

C/CMS composite membranes derived from poly(furfuryl alcohol) (PFA) polymerized by iodine catalyst were prepared. Gas separation performance was investigated by molecular probe study with pure gases (H₂, CO₂, O₂, N₂, and CH₄) at 25 °C. The pyrolysis behaviour of PFA was studied by TG and DTG. The surface morphology of C/CMS composite membranes was observed by SEM and HRTEM. The results show a C/CMS composite membrane with uniform and defect-free thin top layer can be prepared by the PFA liquid in only one coating step. The C/CMS composite membranes have excellent gas separation properties for the gas pairs such as H₂/N₂, CO₂/N₂, O₂/N₂ and CO₂/CH₄, the permselectivities for above gas pairs in same sequence were 124.72, 12.74, 9.12 and 15.91 respectively. Compared to carbon membranes derived from PFA polymerized by acid catalyst, the carbon membranes obtained from PFA polymerized by iodine catalyst have slightly lower permselectivity, but higher permeance.     

Mixed matrix membranes based on 6FDA polyimide with silica and zeolite microsphere dispersed phases

Mixed matrix membranes (MMMs) prepared with 6FDA‐DAM polymer using ordered mesoporous silica MCM‐41 spheres (MSSs), Grignard surface functionalized MSSs (Mg‐MSSs) and hollow zeolite spheres are studied to evaluate the effects of surface modification on performance. Performance near or above the so‐called permeability‐selectivity trade‐off curve was achieved for the H₂/CH₄, CO₂/N₂, CO₂/CH_4, and O₂/N₂ systems. Two loadings (8 wt % and 16 wt %) of MSSs were tested using both constant volume and Wicke–Kallenbach sweep gas permeation systems. Besides single gas H₂, CO₂, O₂, N₂, and CH₄ tests, mixed gas (50/50 vol %) selectivities were obtained for H₂/CH₄, CO₂/N₂, CO₂/CH₄, and O₂/N₂ and found to show enhancements vs. single gases for CO₂ including cases. Mg‐MSS/6FDA‐DAM was the best performing MMM with H₂/CH₄, CO₂/N₂, CO₂/CH₄, and O₂/N₂ separation selectivities of 21.8 (794 Barrer of H₂), 24.4 (1214 Barrer of CO₂), 31.5 (1245 Barrer of CO₂), and 4.3 (178 Barrer of O₂), respectively. © 2015 American Institute of Chemical Engineers AIChE J, 61: 4481–4490, 2015     

Antioxidative degradation mechanism of 2-mercaptobenzimidazole modified TEPA-MCM-41 adsorbents for carbon capture from flue gas

Solid amine adsorbents can efficiently adsorb CO₂, but a significant problem is that amine groups are oxidized. In this research, tetraethylenepentamine-impregnated MCM-41 adsorbents (TEPA-MCM-41) were functionally modified with sulphur-containing antioxidant 2-mercaptobenzimidazole (described as antioxidant MB) and tns-(2.4-di-tert-butyl)-phosphite (defined as antioxidant 168), respectively. The antioxidative degradation mechanism of 8% MB–50% TEPA-MCM-41 was analyzed by in situ diffuse reflectance infrared Fourier transform (in situ DRIFT) spectrum and high-performance liquid chromatography/mass spectrometry (HPLC/mass). The CO₂ adsorption capacity of 50% TEPA-MCM-41 was 4.30 mmol/g under 15% CO₂/85% N₂, but decreased to 1.38 mmol/g after oxidation at 100°C for 42 h under 95% N₂/5% O₂ certain condition. The CO₂ capacity of 8% MB–50% TEPA-MCM-41 reduced from 3.90 to 2.86 mmol/g. After 30 adsorption cycles under 5% O₂/15% CO₂/80% N₂, the capacity of 8% MB–50% TEPA-MCM-41 also only decreased by 16.8%, while 50% TEPA-MCM-41 decreased by 63.2%. The reason for the excellent antioxidant stability of 8% MB–50% TEPA-MCM-41 is that MB scavenged free radicals from amine oxidation and decomposed the hydroperoxides produced by free radical reactions. The hydroperoxides were decomposed into alcohols (non-radical products), which were eventually oxidized to sulphonic compounds. The MB modification inhibited the oxidative degradation of solid amine adsorbents guided for the production of antioxidant-efficient adsorbents.     

Gas separation properties of aromatic polyetherimides from 1,4-bis(3,4-dicarboxyphenoxy)benzene dianhydride and 3,5-diaminobenzic acid or its esters

The gas transport properties of a series polyetherimides, which were prepared from 1,4-bis(3,4-dicarboxyphenoxy)benzene dianhydride (HQDPA) with 1,3-phenylenediamine or 3,5-diaminobenzic acid (DBA) or its esters are reported. The effects of carboxylic group (—COOH) and carboxylic ether groups (—COOR), at five positions of 1,3-phenylenediamine moiety, on H₂ CO₂, O₂, and N₂ permeability, diffusivity, and solubility of the polyetherimides were investigated. The gas permeability, diffusion, and solubility coefficients of the polyetherimides containing COOR are bigger than those of HQDPA-PDA, but the ideal separation factors and ideal diffusivity selectivity factors are much smaller than that of HQDPA-PDA because COOR decreases chain segmental packing efficiency and increases chain segmental mobility. The permeability coefficients of HQDPA-DBA to H₂, CO₂, and O₂ are bigger than those of HQDPA-PDA; the ideal separation factors for gas pairs H₂/N₂, CO₂/N₂, and O₂/N₂ are also much bigger than those of HQDPA-PDA. Both the diffusion coefficients of CO₂ and O₂ and the ideal diffusivity selectivity factors for CO₂/N₂ and O₂/N₂ are bigger than those of HQDPA-PDA because COOH decreases both chain segmental packing efficiency and chain segmental mobility. The copolyimides, which were prepared from 3,5-diaminobenzic acid and 3,5-diaminobenzic esters, have both high permeability and high permselectivity. © 1997 John Wiley & Sons, Inc.     

Preparation of poly(ether‐block‐amide)/poly(amide‐co‐poly(propylene glycol)) random copolymer blend membranes for CO2/N2 separation

A series of poly(amide‐co‐poly(propylene glycol)) (PA‐PPG) random copolymers with different content of PPG were designed by polycondensation reaction. These random copolymers were blended up to 60% with commercially available Pebax 2533. The blend membranes were characterized by Fourier‐transform infrared (FTIR) spectroscopy, X‐ray diffraction (XRD), scanning electron microscope (SEM). Gas permeation properties of these blend membranes were investigated using five single‐gases (CO₂, H₂, O₂, CH₄, and N₂) at different temperature of 25–55°C and 1.0 atm. The impacts of content of PA‐PPG with different PPG content and operating temperature on CO₂ separation properties of Pebax/PA‐PPG blend membranes were studied. The results showed that CO₂ permeability gradually increased with the increasing operating temperature, whereas CO₂ permeability gradually decreased with the increase in content of PA‐PPG. CO₂/N₂ selectivity gradually increased with the increase in content of PA‐PPG. In particular, Pebax/PA‐PPG (50)–60% displayed excellent CO₂ and O₂ separation properties (P_CO2 = 79.7 Barrer and P_O2 = 13.6 Barrer, CO₂/N₂ = 34.7 and O₂/N₂ = 5.9) at 25°C and 1.0 atm. POLYM. ENG. SCI., 59:E14–E23, 2019. © 2018 Society of Plastics Engineers     

Biophotofuel cell (BPFC) generating electrical power directly from aqueous solutions of biomass and its related compounds while photodecomposing and cleaning

A biophotofuel cell (BPFC) generating electrical power directly from aqueous solutions of biomass and its related compounds with simultaneous photodecomposition and cleaning was investigated. The BPFC had a nanoporous TiO₂ photoanode and an O₂-reducing cathode. As long as the compounds were either liquid or water-soluble they were photodecomposed and generated electrical power simultaneously. Various biomasses and related compounds such as glucose, amino acids, polysaccharides, proteins, lignin derivatives, cellulose derivatives and some polymers were investigated in the BPFC. Glucose was photodecomposed almost completely into CO₂ under O₂ within 20 h while generating electrical power. The incident photon-to-current conversion efficiency (IPCE) value of a 0.5 M glucose solution in the BPFC under O₂ was 29% based on the incident monochromatic light at 350 nm (intensity 3.6 mW cm⁻²). A glycine aqueous solution could be decomposed photochemically into CO₂/N₂ in a nearly stoichiometric 4:1 (CO₂:N₂) molar ratio. The photodecomposition yield of 0.01 wt% lignosulfonic acid sodium salt was 86.5% in 24 h as estimated from the CO₂ evolved. The cellulose (sulfate) gave similar BPFC characteristics under air as under 1 atm O₂. Among the compounds the highest V_oc (open circuit voltage) value was 0.90 V for glutamic acid and phenylalanine.     

Single‐Pot Ethane Carboxylation Catalyzed by New Oxorhenium(V) Complexes with N,O Ligands

The oxorhenium(V) chelates [ReOCl(N,O‐L)(PPh₃)] [N,O‐L=(OCH₂CH₂)N(CH₂CH₂OH)(CH₂COO) ( 2 ), (OCH₂CH₂)N(CH₂COO)(CH₂COOCH₃) ( 3 )] and [ReOCl₂(N,O‐L)(PPh₃)] [N,O‐L=C₅H₄N(COO‐2) ( 4 ) C₅H₃N(COOCH₃‐2)(COO‐6) ( 5 )] have been prepared by reaction of [ReOCl₃(PPh₃)₂] ( 1 ), in refluxing methanol, with N,N‐bis(2‐hydroxyethyl)glycine [bicine; N(CH₂CH₂OH)₂(CH₂COOH)], N‐(2‐hydroxyethyl)iminodiacetic acid [N(CH₂CH₂OH)(CH₂COOH)₂], picolinic acid [NC₅H₄(COOH‐2)] or 2,6‐pyridinedicarboxylic acid [NC₅H₃(COOH‐2,6)₂], respectively, with ligand esterification in the cases of 3 and 5 . All these complexes have been characterized by IR and multinuclear NMR spectroscopy, FAB⁺‐MS, elemental and X‐ray diffraction structural analyses. They act as catalysts, in a single‐pot process, for the carboxylation of ethane by CO, in the presence of potassium peroxodisulfate K₂S₂O₈, in trifluoroacetic acid (TFA), to give propionic and acetic acids, in a remarkable yield (up to ca. 30%) and under relatively mild conditions, with some advantages over the industrial processes. The picolinate complex 4 provides the most active catalyst and the carboxylation also occurs, although much less efficiently, by the TFA solvent in the absence of CO. The selectivity can be controlled by the ethane and CO pressures, propionic acid being the dominant product for pressures about ca. 7 and 4 atm, respectively (catalyst 4 ), whereas lower pressures lead mainly to acetic acid in lower yields. These reactions constitute an unprecedented use of Re complexes as catalysts in alkane functionalization.     

CFD modelling of oxy-coal combustion in an entrained flow reactor

Oxy-fuel combustion is seen as one of the major options for CO₂ capture for both new and existing coal fired power stations. Coal is burned with a mixture of oxygen and recycled flue gas to obtain a rich CO₂ stream ready for sequestration. Computational fluid dynamics (CFD) tests for coal combustion under different O₂/CO₂ (21-35% vol O₂) atmospheres in an entrained flow reactor (EFR) were carried out using three coals of different volatile matter content. The temperature profiles, burning rates, burnout and concentration of major species, such as O₂, CO₂, CO, were predicted and compared with an air reference case. A decrease in gas temperature and burning rate was observed for 21% O₂/79% CO₂ environment in comparison to the air reference case due to the difference in gas properties between N₂ and CO₂. Experimental coal burnouts obtained in the EFR, were used to test the accuracy of the CFD model. The numerical results showed a decrease in coal burnout when N₂ was replaced by CO₂ for the same oxygen concentration (21%), but an improvement in the O₂/CO₂ atmosphere for an oxygen concentration higher than 30%. The numerical results for oxy-coal combustion were in good agreement with the experimental results.     

Characterization and transport properties of a novel aliphatic polyamide with an ethyl branch

The CO₂ gas and water vapor transport properties of a novel aliphatic polyamide with an ethyl branch were investigated. The polymer was characterized with density measurements, differential scanning calorimetry, thermogravimetric analysis, and wide‐angle X‐ray diffraction analyses, and the amorphous and glassy nature of the polymer at the ambient temperature were confirmed. The CO₂ sorption isotherm of the polymer appeared to obey the dual‐mode sorption isotherm, which was characteristic of the glassy state. The water vapor sorption below a relative humidity of 0.4 or 0.5 was explained in terms of the Brunauer–Emmett–Teller sorption mechanism, whereas that at a high relative humidity demonstrated a dissolution type of water vapor into the polyamide. The permeability coefficients of He, CO₂, O₂, and N₂ gases through the membrane were as follows: P(He) > P(CO₂) > P(O₂) > P(N₂). The novel polyamide membrane was more permeable to CO₂, O₂, and N₂ gases than nylon 6 and nylon 66 membranes, containing a crystalline and hydrogen‐bonding nature. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 1955–1960, 2005     

Gas permeation properties of a composite membrane filled with poly(ethylene oxide) into a porous membrane

The permeability coefficients of O₂, N₂, and CO₂ gases at 25°C were examined for composite membranes that were prepared by filling poly(ethylene oxide)(PEO) with different molecular weights into a porous membrane. The permeability coefficients of O₂, N₂, and CO₂ were 2 × 10⁻¹⁰ – 4 × 10⁻¹⁰, 5 × 10⁻¹¹ – 9.5 × 10⁻¹¹, and 6 × 10⁻¹⁰ – 1 × 10⁻⁹ (cm³ STPcm/cm² s cmHg), respectively. The higher permeability coefficients of CO₂ are explained in terms of high solubility of CO₂ in filled PEO. The permeability coefficient of CO₂ was affected by the degree of crystallinity of PEO in the composite. On the other hand, there was little effect of crystallinity on O₂ and N₂ permeability coefficients. Some probable relationships between selectivities of O₂ to N₂ and CO₂ to N₂ and the degree of crystallinity of PEO were observed. The CO₂ gas permeability coefficients of the composite membrane for PEO50000 (M_w = 5 × 10⁴) showed a marked change due to melting or crystallization of PEO. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 2733–2738, 1999     

Gas permeability and permselectivity of plasma‐treated polypropylene membranes

The effects of NH₃‐plasma and N₂‐plasma treatment on rubbery polypropylene (PP) membrane upon permeation behavior for CO₂, O₂, and N₂ were investigated from their permeability measurements. The NH₃‐plasma and N₂‐plasma treatment on PP membranes could increase both the permeability coefficient for CO₂ and the ideal separation factor for CO₂ relative to N₂. For O₂ transport, both the permeability coefficient for O₂ and the ideal separation factor for O₂ relative to N₂ also increased. NH₃‐plasma and N₂‐plasma treatment on PP membranes possibly brings about an augmentation of permeability for CO₂ and permselectivity of CO₂ relative to N₂ simultaneously, but unfortunately the plasma‐treated PP membrane does not reach the level of CO₂ separation membrane. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007