Indium(III)-hexacyanoferrate(III, II) as an inorganic material analogous to redox polymers for modification of electrode surfaces

Polynuclear indium(III)-hexacyanoferrate(III, II) films were prepared electrochemically on a glassy carbon substrate. The deposition was performed by cycling the potential between 0.85 and 0.0 V vs sce in a fresh 0.5 mM InCl₃/0.5 mM K₃Fe(CN)₆/0.5 M KCl mixture at pH 2. During the negative scans, the cationic In³⁺ species interact with the simultaneously generated anionic Fe(CN)⁴⁻₆ to yield sparingly soluble mixed-valent coatings on the electrode surfaces. Different thicknesses, typically corresponding to 1–100 nmol cm⁻², could be obtained by varying the cycling times. The modified electrode exhibits a single set of well-defined and highly reversible voltammetric peaks (related to the hexacyanoferrate redox transitions) in K⁺-containing electrolytes. Electrochemical charging is accompained by the cation motion, leading to the cation storage in the reduced state and its release upon oxidation. The results are consistent with high ionic conductivity of potassium in the film. Experiments in the other alkali metal electrolytes show that the cataion transport, necessary for the charge compensation during redox transitions, cannot be simply related to the size of a cation and the zeolitic structure of indium hexacyanoferrate.     

Swollen-state polymerization of poly(ethylene terephthalate) in fibre form

The swollen-state polymerization of poly(ethylene terephthalate) in fibre form was performed in hydrogenated terphenyl as the swelling solvent. Ultra-high-molecular-weight poly(ethylene terephthalate) (CHMW-PET) fibre with an intrinsic viscosity of 3–4dl g⁻¹ (M_n = 2–3 × 10⁵) was obtained. The polymerization rate of as-spun PET fibres in the swollen state was greater than that of PET granules in the swollen state. It was clarified that the polymerization rate was related to the chain mobility of the starting materials. The chain mobility was influenced by various conditions, such as changing rigidity of the segments during copolymerization, the chain orientation of the starting fibre before swollen-state polymerization and the temperature of pretreatment with the solvent. Pretreatment with solvent before polymerization was effective in increasing the chain mobility. The relation between chain mobility and polymerization rate was examined by wide-angle X-ray diffraction, density, differential scanning calorimetry, solvent content and viscoelastic measurements. Undrawn UHMW-PET fibres could be drawn 10 times or more by the zone drawing technique in spite of their high crystallinity, and the drawn fibre showed high tensile strength (12 g d⁻¹) and high modulus (240 g d⁻¹).     

Ionic conductivity of PEO9: Cu(CF3SO3)2: Al2O3 nano-composite solid polymer electrolyte

Cu⁺⁺ ion containing solid polymer electrolytes exhibit interesting electrochemical properties. In particular, the polymer electrolyte PEO₉:Cu(CF₃SO₃)₂ made by complexing copper triflate (CuTf₂) with PEO appears to show scientifically intriguing transport properties. Although some copper ion transport in these systems has been seen from plating stripping processes, the detailed mechanism of ionic transport and the species involved are yet to be established. In order to obtain enhanced ionic conductivities and also to contribute towards understanding the ionic transport process in Cu⁺⁺ ion containing, PEO based composite polymer electrolytes, we have studied the system PEO₉: CuTf₂: Al₂O₃ incorporating 10 wt.% of alumina filler particles of grain size 10 μm, 37 nm, 10–20 nm and also particles of pore size 5.8 nm. Thermal and electrical measurements show that the system remains amorphous down to room temperature. The composite electrolyte is predominantly an ionic conductor with electronic conductivity less than 2%. The triflate (CF₃SO₃⁻) anions appear to be the dominant carriers. The presence of alumina grains has enhanced the conductivity significantly from room temperature up to 100 °C. The nano-porous grains with 5.8 nm pore size and 150 m²/g specific surface area exhibited the maximum conductivity enhancement. This enhancement has been attributed to Lewis acid–base type surface interactions of ionic species with O²⁻ and OH⁻ groups on the filler grain surface.     

The influence of pH on reaction pathways for O2 reduction on the Au(100) face

Oxygen reduction on the Au(100) face was studied by the rotating disk-ring electrode technique in solutions of anions which adsorb strongly on gold (HSO₄⁻/SO₄²⁻ and/or OH⁻) over the entire pH range. The specific adsorption of OH⁻ anions, which is a pH dependent process, is found to play the key role in determining the reaction pathways. In the absence of OH⁻ adsorption, for pHs below 6, the reduction of O₂ begins as a 2e-process. Due to the increase in local pH during O₂ reduction, the reaction pathway turns into a 4e-reduction at a certain potential depending on the pH of the solution. For pHs higher than 6, O₂ reduction begins as a 4e-process in the potential region where specifically adsorbed OH⁻ anions are present.     

Methacryl-terminated macromers by living polymerization as precursors of IPN polymer electrolytes

A new class of polymer electrolytes, based on the interpenetrating polymer network approach, was obtained starting from functionalised macromers, of poly-ether nature, in the presence of a lithium salt (LiBF₄, LiClO₄, LiCF₃SO₃) and propylene carbonate (PC) or tetraethyleneglycol dimethylether (TGME), as plasticizers.

The macromers were synthesised by living polymerisation employing a HI/I₂ system as the initiator. The macromer has a polymerisable end group, which can undergo radical polymerisation, attached to a monodisperse poly-vinylether, containing suitable ethylene oxide groups for ion coordination. Monomers and macromers were characterised by FTi.r., u.v.–vis, ¹H- and ¹³C-n.m.r.

Self-consistent and easily handled membranes were obtained as thin films by a dry procedure using u.v. radiation to polymerise and crosslink the network precursors, directly on suitable substrates, in the presence of the plasticizer and the lithium salt. The electrolytic membranes were studied by complex impedance and their thermal properties determined by differential scanning calorimetry analysis.

Ionic conductivities (σ) were measured for PC and TGME-based membranes at various plasticizer and salt contents as a function of T (60 to −20°C). LiClO₄/PC/PE electrolytes, with 3.8% (w/w) salt and 63% PC, have the highest σ (1.15×10⁻³ and 3.54×10⁻⁴ S cm⁻¹ at 20°C and −20°C, respectively). One order of magnitude lower conductivities are achieved with TGME; samples with 6% (w/w) LiClO₄ and 45% (w/w) TGME exhibit σ values of 2.7×10⁻⁴ and 2.45×10⁻⁵ S cm⁻¹ at 20°C and −20°C.     

Poly(ethylene oxide)–LiX rubbery electrolytes with X–X disulfonamide anions having two or three ether groups in their structures

This work deals with poly(ethylene oxide), PEO–MX (M=Li, K and Cs) amorphous electrolytes with ⁻X–X⁻, [CF₃SO₂NCH₂(CH₂OCH₂)₂CH₂NSO₂CF₃]²⁻ (EDSA) and [CF₃SO₂NCH₂CH₂(CH₂OCH₂)₃CH₂CH₂NSO₂CF₃]²⁻ (TTSA) disulfonamide anions. These dianions have X⁻ end-groups identical to anions [CF₃SO₂N(CH₂)₂OCH₃]⁻ (MESA) and [CF₃SO₂N(CH₂)₃OCH₃]⁻ (MPSA), one of which (MPSA) was reported to yield chelate-like associated species (presumably LiX₂⁻ triplets) at concentrations above EO/Li=20 in PEO. This feature of LiMPSA, evidenced through glass transition temperature (T_g) measurements, does not apply to Li₂EDSA and Li₂TTSA. Though none of these lithium salts form crystalline intermediate compounds with PEO, the limit of solubility of LiMESA (EO/Li=16) does not allow a clarification of this point for this salt. At lower concentrations, however, a conductivity comparison with the potassium and caesium salts shows that the apparent degree of dissociation (=C_Li+/C_Li) of LiMESA is comparable to that of LiMPSA. As opposed to both these salts and to some extent to Li₂EDSA, a much greater dissociation takes place for Li₂TTSA, the anion of which contains an inner, third ether group in its structure.     

Hydroxyapatite photocatalytic degradation of calmagite (an azo dye) in aqueous suspension

The hydroxyapatite (HAP) is prepared by precipitation method and examined for the photocatalytic degradation of calmagite, a toxic and non-biodegradable azo-dye compound. The physicochemical properties of hydroxyapatite material were characterized using BET surface area, XRD, FT-IR, and SEM analysis. The FT-IR analysis of the hydroxyapatite revealed that the peak intensity due to absorbance of surface PO₄³⁻ group centered at wave number 1030 cm⁻¹ is drastically decreased upon exposure to UV for 1 h. The study includes dark adsorption experiments at different pH conditions, influence of the amount of catalyst, and effect of pH on photocatalytic degradation of dye, chemical oxygen demand (COD) removal, biological oxygen demand (BOD₅) increase and SO₄²⁻ and NO₃⁻ ions evolution during the degradation. At optimum photocatalytic experimental conditions the same is compared with commercial degussa P-25 TiO₂. The photocatalytic treatment significantly reduced the COD (92% removal) and increased the BOD₅/COD ratio to 0.78. Considerable evolution of SO₄²⁻ (8.5 mg L⁻¹) and NO₃⁻ (12.2 mg L⁻¹) ions are achieved during the degradation process, thus reflecting the usefulness of the hydroxyapatite photocatalytic treatment in calmagite removal in wastewater.     

Efficient destruction of bacteria with Ti(IV) and antibacterial ions in co-substituted hydroxyapatite films

Hydroxyapatite (Ca₁₀(PO₄)₆(OH)₂: HAP) was co-substituted with Ti(IV) and antibacterial ions (Ag⁺, Cu²⁺ or Zn²⁺) (HAPTiM), by coprecipitation and ion-exchange methods. Both HAPTiAg and HAPTiCu coated on porous spumous nickel film showed high efficiency for killing Escherichia coli and Staphylococcus aureus in the dark and under weak UVA irradiation, respectively. Moreover, their bactericidal activities were much higher than that of P25-TiO₂ film. The studies of ESR revealed that not only O₂⁻ was formed on HAPTiM, HAPTi, HAP and P25-TiO₂ films under weak UVA irradiation, but also at ambient temperature without light O₂⁻ was generated on HAPTiCu, HAPTiAg, and HAPTi. The redox couples of Cu⁰/Cu²⁺ and Ag⁰/Ag⁺ in the structure of HAPTiCu (Ag) caused the transfer of electron leading to the O₂⁻ generation under the above conditions. The higher bactericidal activities of HAPTiM were due to the synergy of the oxidation role of the O₂⁻ and the bacteriostatic action of antibacterial ions. The process of the damage of the cell wall and the cell membrane was directly observed by TEM, and further confirmed by the determination of potassium ion (K⁺) leakage from the killed bacteria.     

Phase behaviour in poly(ethylene oxide-b-t-butyl methacrylate) block copolymers

The lamellar thickness of the poly(ethylene oxide)-poly(t-butyl methacrylate) (PEO-PTBMA) diblock copolymer system, obtained by differential scanning calorimetry and small angle X-ray scattering investigations, is correlated with the degree of polymerization of the amorphous (PTBMA) and crystallizable (PEO) sequences. The non-equilibrium exponents obtained immediately after bulk crystallization are different to those from extrapolated equilibrium results. Within the experimental standard deviations, the theoretical predictions of DiMarzio et al. and of Whitmore and Noolandi could be confirmed. The molecular weights of PEO and PTBMA ranged from 250 to 21000 g mol⁻¹ and from 1500 to 17000 g mol⁻¹, respectively. Both the equilibrium lamellar thickness l and the PEO domain size d_PEO increase with increasing PEO and decreasing PTBMA degrees of polymerization Z according to d_PEO l Z^0.97±0.08_EOZ^{−(0.53±0.19)}_TBMA.     

Production of Ultra Clean Coal: Part I—Dissolution behaviour of mineral matter in black coal toward hydrochloric and hydrofluoric acids

The mineral matter in an Australian black coal has been isolated using a low-temperature ashing (LTA) procedure. This LTA procedure is a modification of the Australian Standard for LTA at 370°C, and alleviates adverse effects to the minerals caused by the heat of combustion. The leaching behaviour of the mineral matter towards aqueous HCl and hydrofluoric acid (HF) is presented. HCl can dissolve simple compounds such as phosphates and carbonates, yet it cannot completely dissolve the clays. HF reacts with almost every mineral in the mineral matter, except pyrite, and most of the reaction products are water soluble. However, at HF concentrations greater than that required to dissolve the aluminosilicate compounds in the mineral matter, insoluble compounds form. These compounds include CaF₂, MgF₂ and a compound containing Na, which is believed to be NaAlF₄. It is proposed that HF reacts preferentially with the aluminosilicates in the mineral matter to form largely AlF₂⁺, AlF₃ and SiF₄, and that the concentrations of free fluoride (F⁻) and AlF₄⁻ are not high enough to complex cations such as Ca²⁺, Mg²⁺ and Na⁺. When the mineral matter is treated with HF concentrations greater than that required to dissolve all of the aluminosilicates, AlF₃, AlF₄⁻ and SiF₆²⁻ form, the concentration of F⁻ is high enough to complex Ca²⁺ and Mg²⁺ and form insoluble CaF₂ and MgF₂, and the concentration of AlF₄⁻ is high enough to complex Na⁺ and form insoluble NaAlF₄. This work has application toward the development of a process for producing Ultra Clean Coal with less than 0.1% by weight mineral matter.     

Passivity behavior of melt-spun Mg–Y Alloys

Several Mg–Y binary ribbons with Y content up to 17.9 at.% were fabricated by melt-spinning. X-ray diffraction (XRD) revealed that the phase structure changes with increasing Y content from extended solid solution to partially amorphous, and then fully intermetallic Mg₂₄Y₅. Anodic potentiodynamic polarization performed in 0.01 M NaCl electrolyte (pH=12) revealed improved anodic passivity behavior compared to pure Mg for all the Mg–Y alloys. X-ray photoelectron spectroscopy (XPS) revealed that the improved passivity of Mg–Y was more related to the elemental oxidation state rather than the concentration of the surface components. To study the effect of Cl⁻ ion on the passivity behavior, anodic potentiodynamic and potentiostatic polarization were performed on Mg–17.9 at.% Y in alkaline (pH=12) NaCl electrolytes containing Cl⁻ ion in the concentration range from 0.00 to 0.50 M. The passive films formed in 0.01 M NaCl electrolyte were similar to the native film, which were composed of MgO and Y₂O₃. No CO₃²⁻ and Cl⁻ ions were incorporated into the passive film. The passivity was significantly degraded in the electrolytes containing higher Cl⁻ concentration (0.1 and 0.5 M). Detailed XPS revealed that the surface films under these conditions were composed of much hydrated species Mg(OH)₂ and YOOH and/or Y(OH)₃ and CO₃²⁻ was incorporated into the surface film. The incorporation of Y₂O₃ in the passive film was given as the reason for the enhanced passivity properties of Mg–Y ribbons. The mechanism of Cl⁻ and CO₃²⁻ ions to the degradation of the passivity was discussed.     

Alumina-supported catalysts for propane oxidative dehydrogenation from mixed VXM(6−X)O19 (M=W, Mo) hexametalate precursors

γ-Al₂O₃ supported vanadium oxides were modified by tungsten and molybdenum oxides in order to improve dispersion and selectivity towards olefins in propane oxidative dehydrogenation (ODH). Both vanadium–tungsten and vanadium–molybdenum catalysts were obtained by adsorption of mixed isopolyanions (VW₅O₁₉⁵⁻, V₂W₄O₁₉⁴⁻, VMo₅O₁₉⁵⁻ and V₂Mo₄O₁₉⁴⁻) from aqueous solutions. The isopolyanion solutions were characterized by UV-Vis and ⁵¹V NMR spectroscopy. Vanadium, vanadium–tungsten and vanadium–molybdenum precursors and catalysts were also characterized by UV-Vis (diffuse reflectance) and solid state ⁵¹V NMR spectroscopy. An improved selectivity to propene in the presence of tungsten and molybdenum in VO_x/γ-Al₂O₃ was observed and attributed to dilution of vanadium by tungsten or molybdenum oxides on the γ-Al₂O₃ surface.     

Transport numbers and oxygen permeability of SrCe(Y)O3-based ceramics under oxidising conditions

Partial conductivities in the SrCe(Y)O_3−δ system have been studied in oxidising conditions in the temperature range 923–1273 K. Compositions with variable Y content (5 and 10 at.%), Sr deficiency (3 at.%), and with the addition of Fe₂O₃ as sintering aid (2 mol%) were analysed. A modified Faradaic efficiency method and oxygen permeation measurements were employed to appraise the oxide-ionic transport. Oxide-ion transference numbers in air lie in the range 0.19–0.80 and decrease with increasing temperature in the range 973–1223 K. Modelling of total conductivity as a function of oxygen partial pressure (p(O₂)) confirmed that protonic transport is minor under the studied conditions. SrCe_0.95Y_0.05O_3−δ exhibits greater oxide-ion conductivity than SrCe_0.9Y_0.1O_3−δ, indicative of dopant–vacancy association at high dopant contents. Conversely, oxygen permeability is slightly higher for SrCe_0.9Y_0.1O_3−δ as a result of faster surface-exchange kinetics. The oxygen flux through Fe-free membranes is dominated by the bulk in low p(O₂) gradients, when the permeate-side p(O₂) is higher than 0.03 atm, but surface exchange plays an increasing role with increasing p(O₂) gradient. Addition of Fe₂O₃ to SrCe(Y)O_3−δ lowers the sintering temperature by 100 K but results in the formation of intergranular second phases which block oxide-ionic and electronic transport, and thus oxygen permeation. The average thermal expansion coefficients (TECs) are (10.8–11.6) × 10⁻⁶ K⁻¹ in the temperature range 373–1373 K for all studied compositions.     

Anodic reactions of several reducing agents on illuminated cadmium sulfide electrode

Anodic reactions of several reducing agents occurring in competition with the electrode dissolution at an illuminated CdS electrode were studied under the potentiostatic condition. S²⁻, SO²⁻₃, and S₂O²⁻₃ ions, which can effectively suppress the photoanodic dissolution of CdS, shift the flatband potential of this electrode to the cathodic direction, leading to the shift of the onset potential for the anodic photocurrent. This shift is attributed to the adsorption of these ions on the electrode surface. Two- or three-step wave appeared in the photoanodic polarization curves in the electrolytes containing low concentration of these ions. The mechanism for these electrodic reactions was discussed in detail in terms of the energy band structure. It can be concluded that the reducing agents which interact so strongly with the CdS electrode surface that the energy band structure at the electrode/electrolyte interface is changed can suppress effectively the photoanodic dissolution of the electrode. The tendency of this interaction was S²⁻ > SO²⁻₃ > S₂O²⁻₃.     

Mechanistic approach of the combined (iron–TiO2) photocatalytic system for the degradation of pollutants in aqueous solution: an attempt of rationalisation

Kinetics of oxidative photodegradation of Monuron (3-(4-chlorophenyl)-1,1-dimethylurea) in different photocatalytic systems (iron, TiO₂ and combined system iron + TiO₂) were investigated and compared. The influence of iron addition on TiO₂ photocatalyst and of TiO₂ on the photocatalytic cycle Fe(III)/Fe(II) were carefully studied. A very positive effect of iron addition was observed. This phenomenon was more and more pronounced when TiO₂ concentration was lower. In a suspension of TiO₂ (24 mg L⁻¹) with addition of Fe(III) (3 × 10⁻⁴ mol L⁻¹) the measured rate constant was similar to that obtained in a suspension of TiO₂ with a concentration more than 20 times higher (500 mg L⁻¹). The mechanistic approach carried out in this study allows us to identify the main reactions governing the combined system and a photochemical cycle was proposed. The optimisation of the photocatalytic systems was obtained when each photocatalyst plays a specific role: Fe(III) as a main OH radicals source and TiO₂ as an oxidizing agent of Fe(II).     

Additive effects of trialkylaluminum on propene polymerization with (t-BuNSiMe2Flu)TiMe2-based catalysts

Propene polymerization was conducted by [η³:η¹-tert-butyl(dimethylfluorenylsilyl)amido]dimethyltitanium combined with B(C₆F₅)₃ or methylaluminoxane (MAO) as a cocatalyst in the presence or absence of various trialkylaluminums: Me₃Al, Et₃Al, ⁱBu₃Al (triisobutylaluminum) and Oct₃Al (trioctylaluminum). In the case of living polymerization with B(C₆F₅)₃ at −50°C, addition of Oct₃Al and Et₃Al increased the propagation rate. Et₃Al also acted as a chain transfer reagent and selectively gave Al-terminated polymers, while Oct₃Al induced chain transfer reaction only in high concentration. Little polymer was obtained in the presence of Me₃Al or ⁱBu₃Al. When MAO was used as a cocatalyst, polymerization did not proceed at −50°C. The MAO system, however, showed high activity at 40°C and selectively gave low molecular weight polymers terminated with Al–C bonds. Contrary to the low temperature polymerization with B(C₆F₅)₃ at −50°C, the polymer yield was enhanced by the addition of Me₃Al and ⁱBu₃Al, while the molecular weight was reduced by Me₃Al and enlarged by ⁱBu₃Al. On the other hand, Et₃Al and Oct₃Al significantly decreased both the polymer yield and the molecular weight under these conditions. It was found that additive effects of trialkylaluminums were strongly dependent on polymerization temperature as well as on the structure of the alkyl group.     

The elastic modulus of the poly(phosphonitrilic chloride) crystal

The Young's modulus for a crystal of poly(phosphonitrilic chloride) (poly-dichlorophosphazene) (NPCl₂)_n has been calculated using force constants derived from spectroscopy. Assuming that the molecule is a uniform helix the value of the modulus is 1.38 × 10⁹ dyne cm⁻² [dyne cm⁻² = 0.1 N m⁻²]; the result is 1.66 × 10¹⁰ dyne cm⁻² if a cis-planar structure is assumed for the molecule. Neither value is close to those obtained experimentally (1.8 × 10⁶ to 6.5 × 10⁶ dyne cm⁻²). This is because experimental values relate to the amorphous polymer whereas the calculated values are those for the crystal. There is good agreement between the values calculated for the (NPCl₂)_n crystal and those for other polymer crystals.     

Effective Au-Au-Clx/Fe(OH)y catalysts containing Cl for selective CO oxidations at lower temperatures

Supported Au catalysts Au-Au⁺-Cl_x/Fe(OH)_y (x < 4, y ≤ 3) and Au-Cl_x/Fe₂O₃ prepared with co-precipitation without any washing to remove Cl⁻ and without calcining or calcined at 400 °C were studied. It was found that the presence of Cl⁻ had little impact on the activity over the unwashed and uncalcined catalysts; however, the activity for CO oxidation would be greatly reduced only after Au-Au⁺-Cl_x/Fe(OH)_y was further calcined at elevated temperatures, such as 400 °C. XPS investigation showed that Au in catalyst without calcining was composed of Au and Au⁺, while after calcined at 400 °C it reduced to Au⁰ completely. It also showed that catalysts precipitated at 70 °C could form more Au⁺ species than that precipitated at room temperatures. Results of XRD and TEM characterizations indicated that without calcining not only the Au nano-particles but also the supports were highly dispersed, while calcined at 400 °C, the Au nano-particles aggregated and the supports changed to lump sinter. Results of UV–vis observation showed that the Fe(NO₃)₃ and HAuCl₄ hydrolyzed partially to form Fe(OH)₃ and [AuCl_x(OH)_4−x]⁻ (x = 1–3), respectively, at 70 °C, and such pre-partially hydrolyzed iron and gold species and the possible interaction between them during the hydrolysis may be favorable for the formation of more active precursor and to avoid the formation of Au–Cl bonds. Results of computer simulation showed that the reaction molecular of CO or O₂ were more easily adsorbed on Au⁺ and Au⁰, but was very difficultly absorbed on Au⁻. It also indicated that when Cl⁻ was adsorbed on Au⁰, the Au atom would mostly take a negative electric charge, which would restrain the adsorption of the reaction molecular severely and restrain the subsequent reactions while when Cl⁻ was adsorbed on Au⁺ there only a little of the Au atom take negative electric charge, which resulting a little impact on the activity.     

Separation and enrichment of carbon dioxide by capillary membrane module with permeation of carrier solution

A novel facilitated transport membrane for gas separation using a capillary membrane module is proposed in which a carrier solution is forced to permeate the membrane. Both a feed gas and a carrier solution are supplied to the lumen side (high pressure side, feed side) of the capillary ultrafiltration membrane and flow upward. Most of the carrier solution which contains dissolved solute gas, CO₂ in the present case, permeates the membrane to the permeate side (low pressure side, shell side), where the solution liberates dissolved gas to form a lean solution. The lean solution is circulated to the lumen side. This type of capillary membrane module was applied to the separation of CO₂ from model flue gases consisting of CO₂ and N₂. Monoethanolamine (MEA), diethanolamine (DEA) and 2-amino-2-methyl-1-propanol (AMP) were used as carriers or absorbents of CO₂. The feed side pressure was atmospheric and the permeate side was evacuated at about 10 kPa. CO₂ in the feed gas was successfully concentrated from 5–15% to more than 98%. The CO₂ permeance was as high as 2.7×10⁻⁴ mol m⁻² s⁻¹ kPa⁻¹ (8.0×10⁻⁴ cm³ cm⁻² s⁻¹ cmHg⁻¹) when the CO₂ mole fraction in the feed was 0.1 and temperature was 333 K. The selectivity of CO₂ over N₂ was in the range from 430 to 1790. The membrane was very stable over a discontinuous one-month testing period.     

Nanosized perovskite-type oxides La1−xSrxMO3−δ (M = Co, Mn; x = 0, 0.4) for the catalytic removal of ethylacetate

Nanometer perovskite-type oxides La_1−xSr_xMO_3−δ (M = Co, Mn; x = 0, 0.4) have been prepared using the citric acid complexing-hydrothermal-coupled method and characterized by means of techniques, such as X-ray diffraction (XRD), BET, high-resolution scanning electron microscopy (HRSEM), X-ray photoelectron spectroscopy (XPS), temperature-programmed desorption (TPD), and temperature-programmed reduction (TPR). The catalytic performance of these nanoperovskites in the combustion of ethylacetate (EA) has also been evaluated. The XRD results indicate that all the samples possessed single-phase rhombohedral crystal structures. The surface areas of these nanomaterials ranged from 20 to 33 m² g⁻¹, the achievement of such high surface areas are due to the uniform morphology with the typical particle size of 40–80 nm (as can be clearly seen in their HRSEM images) that were derived with the citric acid complexing-hydrothermally coupled strategy. The XPS results demonstrate the presence of Mn⁴⁺ and Mn³⁺ in La_1−xSr_xMnO_3−δ and Co³⁺ and Co²⁺ in La_1−xSr_xCoO_3−δ, Sr substitution induced the rises in Mn⁴⁺ and Co³⁺ concentrations; adsorbed oxygen species (O⁻, O₂⁻, or O₂²⁻) were detected on the catalyst surfaces. The O₂-TPD profiles indicate that Sr doping increased desorption of the adsorbed oxygen and lattice oxygen species at low temperatures. The H₂-TPR results reveal that the nanoperovskite catalysts could be reduced at much lower temperatures (<240 °C) after Sr doping. It is observed that under the conditions of EA concentration = 1000 ppm, EA/oxygen molar ratio = 1/400, and space velocity = 20,000 h⁻¹, the catalytic activity (as reflected by the temperature (T_100%) for EA complete conversion) increased in the order of LaCoO_2.91 (T_100% = 230 °C) ≈ LaMnO_3.12 (T_100% = 235 °C) < La_0.6Sr_0.4MnO_3.02 (T_100% = 190 °C) < La_0.6Sr_0.4CoO_2.78 (T_100% = 175 °C); furthermore, there were no formation of partially oxidized by-products over these catalysts. Based on the above results, we conclude that the excellent catalytic performance is associated with the high surface areas, good redox properties (derived from higher Mn⁴⁺/Mn³⁺ and Co³⁺/Co²⁺ ratios), and rich lattice defects of the nanostructured La_1−xSr_xMO_3−δ materials.