Electro-electrodialysis of hydriodic acid using the cation exchange membrane cross-linked by accelerated electron radiation

Electro-electrodialysis (EED) of hydriodic acid with HI molality of ca. 9.5 mol/kg was examined in the presence of iodine using a commercial cation exchange membrane (CMB) as a separator. For the increase of the selectivity of proton permeation, the membrane was cross-linked by accelerated electron radiation. The membrane properties (area resistance, ion exchange capacity (IEC), water content) of the cross-linked membranes were measured. The area resistance in 2 mol/dm³ KCl solution of the cross-linked membranes decreased as compared with that of the non-cross-linked membrane (original of CMB membrane). The IEC and water content of cross-linked membranes at each dose rate had almost the same value as that of non-cross-linked membrane. Electro-electrodialysis of hydriodic acid with HI molality of ca. 9.5 mol/kg was examined at 75 °C with 9.6 A/dm². The cross-linked cation exchange membrane by accelerated electron radiation had higher selectivity of the proton permeation by cross-linking structure of polymer than that of the non-cross-linked membrane.     

Phosphoric acid doped high temperature proton exchange membranes based on sulfonated polyetheretherketone incorporated with ionic liquids

A composite membrane was fabricated using a novel approach based on the ionic liquids 1-butyl-3-methylimidazolium chloride or 1-butyl-3-methylimidazolium hexafluorophosphate, sulfonated polyetheretherketone (SPEEK), and phosphoric acid. This proton conducting composite membrane shows promise for operation in high temperature proton exchange membrane fuel cells at working temperatures up to 160 °C without humidification. Proton conductivity at a level of 2.0 × 10^? 2 S/cm was achieved at 160 °C by the composite membrane with a molar ratio of 1:0.6:9 for SPEEK, 1-butyl-3-methylimidazolium (BMIM) cation and phosphoric acid, respectively. The sulfonation degree was 0.643 per polymer repeat unit with over 90% of the sulfate fixed anions forming a salt complex with BMIM cations. The tensile stress at break of the composite membrane was 15.5 MPa at room temperature, and it decreased from 4.1 to 1.9 MPa when the temperature increased from 110 to 160 °C, respectively.     

Pervaporation separation of aromatic/aliphatic hydrocarbons by crosslinked poly(methyl acrylate-co-acrylic acid) membranes

Copolymers of methyl acrylate and acrylic acid were synthesized to fabricate membranes ionically crosslinked using aluminum acetylacetonate for the separation of toluene/i-octane mixtures by pervaporation at high temperatures. The formation of the ionic crosslinking via bare aluminum cations was characterized by UV–VIS spectroscopy and solubility tests. Reproducibility and the reliability of the methodology for membrane formation and crosslinking were confirmed. The effects of acrylic acid content, crosslinking conditions, pervaporation temperature, and feed composition on the normalized flux and the selectivity for toluene/i-octane mixtures were determined. A typical crosslinked membrane showed a normalized flux of 26 kg μm m⁻² h⁻¹ and a selectivity of 13 for a 50/50 wt.% feed mixture at 100°C. The pervaporation properties including solubility selectivity and diffusivity selectivity are discussed in terms of swelling behavior. The performance of the current membranes were benchmarked against other membrane materials reported in the literature.     

Solvation of sulphonic acid groups in Nafion® membranes from accurate conductivity measurements

The wide degree of scatter of experimental data shows unambiguously that Nafion^®117 conductivity is very sensitive to climatic conditions, temperature and relative humidity. In order to allow equilibrium with the surrounding atmosphere to be reached rapidly, a conductivity cell, adapted to a small size membrane samples, has been designed. Conductivity measurements have been carried out by electrochemical impedance spectroscopy (EIS) between 10 °C and 95 °C in a broad domain of relative humidity, i.e., 10–98%. The measurement set up provides reproducible data with a total uncertainty of 30% in a large range of conductivity values. These accurate data enable a power relationship to be proposed at constant temperature between conductivity and relative humidity. This suggests that the solvation process of a sulphonic acid group involves four water molecules. Based on the assumption that a proton mobility depends weakly on temperature, a solvation enthalpy of a sulphonic acid group by water of −135 kJ mol⁻¹ is deduced from conductivity variations with the temperature.     

Thermal stability of fatty acids in subcritical water

In this work, hydrolytic reaction conditions of various temperatures (300–370 °C) and times (0–30 min) at a constant pressure of 20 MPa were applied to the thermal decomposition of three kinds of fatty acids (FAs), stearic acid, oleic acid, and linoleic acid, in subcritical water. The degradation characteristics were investigated from the derived data, and the thermal stability of FAs in subcritical water was estimated. The primary reactions we observed were isomerization and pyrolysis of FAs. The main pathway of degradation was deduced by analyzing the contents of pyrolyzed products. We found that more saturated FAs have greater thermal stability in subcritical water. All FAs remained stable at 300 °C or below. Based on these results, we recommend that hydrolysis of vegetable oils and fats using subcritical water should be carried out below 300 °C (at 20 MPa) and for less than 30 min to obtain high-yield FA production.     

Proton-conducting membranes based on poly(2,5-benzimidazole) (ABPBI) and phosphoric acid prepared by direct acid casting

We report the preparation of phosphoric acid doped poly(2,5-benzimidazole) (ABPBI) membranes for PEMFC by simultaneously doping and casting from a poly(2,5-benzimidazole)/phosphoric acid/methanesulfonic acid (MSA) solution. The evaporation of MSA yields a very homogeneous membrane having a better controlled composition, avoiding the use of solvent-intensive procedures. Membranes have been prepared with contents of up to 3.0H₃PO₄ molecules per ABPBI repeating unit. These membranes achieve a maximum conductivity of 1.5 × 10⁻² S cm⁻¹ at temperatures as high as 180 °C in dry conditions. These ABPBI membranes are more conveniently prepared than those conventionally formed and doped in separate steps while featuring comparable conductivities (ABPBI × 2.7H₃PO₄ prepared by the soaking method showed a conductivity of 2.5 × 10⁻² S cm⁻¹ at 180 °C in dry conditions).     

Experimental low temperature water content in gaseous methane,liquid ethane,and liquid propane in equilibrium with hydrate at cryogenic conditions

In low temperature gas processing, the presence of water can result in the formation of gas hydrate plugs. To avoid this problem, it is important to know the water solubility in natural gas components in equilibrium with gas hydrate. In this study experimental measurements of water content in gaseous methane in equilibrium with hydrate at 3.45 MPa (500 psia) and 6.90 MPa (1000 psia) and temperatures ranging from −3.2 °C (26.2 °F) to −80 °C (−112 °F) are presented. Similar measurements are presented for liquid ethane at 3.45 MPa (500 psia) and temperatures from −2.2 °C (28.0 °F) to −70 °C (−94 °F), and for liquid propane at 0.86 MPa (125 psia) and temperatures down to −60 °C (−76 °F), respectively.In measuring the water content, a Panametrics moisture sensor (calibrated to 1 ppb water content in nitrogen) has been used in flowing streams of the hydrocarbon-rich phases that are saturated with water. The results obtained with the Panametrics hygrometer show good agreement (normally better than ±4%) with previous measurements, which were obtained by a gas chromatographic technique for methane, ethane, and propane at temperatures ranging from −2.0 °C (28.4 °F) to −30 °C (−22 °F), which are within the hydrate region.     

Effect of quarantine treatments on the carbohydrate and organic acid content of mangoes (cv. Tommy Atkins)

Brazil is one of the largest mango producers and the third largest mango exporter worldwide. Irradiation treatment and its commercial feasibility have been studied in our country to make it possible to develop new markets and, consequently, to compete with the major exporters of mangoes, Mexico and India. This work was designed to compare irradiation treatment with the hot water dip treatment in mangoes cv. Tommy Atkins for export and to verify that the main attributes for acceptance, color and texture, as well as carbohydrate and organic acid contents, were maintained. In this study, the fruit was divided into groups: control, hot water dip-treated (46 °C for 90 min), and irradiation-treated at doses of 0.4 kGy and 1.0 kGy. The fruit was stored at low temperature (11 °C±2) for 14 days and then at room temperature (23 °C±2) until the end of the study. The results indicated that the fruit given a dose of 1.0 kGy remained in a less advanced stage of ripening (stage 3) throughout the storage period, but experienced a greater loss of texture in the beginning of the experiment. It was noted that only the control group had higher levels of citric acid and succinic acid on the last day of the experiment. There were no significant differences in the total sugar content between any treatment groups. Gamma radiation can be used as a quarantine treatment and does not interfere negatively with the quality attributes of mangoes.     

Effects of H3PO4 and KOH in carbonization of lignocellulosic material

Samples of lignocellulosic material, stem of date palm (Phoenix dactylifera), were carbonized at different temperatures (400–600 °C) to investigate the effects of their impregnation with aqueous solution of either phosphoric acid (85 wt%) or potassium hydroxide (3 wt%). The products were characterized using BET nitrogen adsorption, helium pycnometry, Scanning Electron Microscopy (SEM) and oil adsorption from oil–water emulsion (oil viscosity, 60 mPa s at 25 °C). True densities of the products generally increased with increase in carbonization temperature. Impregnated samples (acid/base) showed wider differences in densities at 400 (1.978/1.375 g/cm³) than at 600 °C (1.955/2.010 g/cm³). Without impregnation, the sample carbonized at 600 °C showed higher density of 2.190 g/cm³. This sample has impervious surface with BET surface area of 124 m²/g. Acid-impregnated sample carbonized at 500 °C has the highest surface area of 1100 m²/g and most regular pores as evidenced by SEM micrographs. The amounts of oil adsorbed decreased with increase in carbonization temperature. Without impregnation, sample carbonized at 400 °C exhibited equilibrium adsorption of 4 g/g which decreases to about a half for sample carbonized at 600 °C. Impregnation led to different adsorptive capacities. There are respective increase (48 wt%) and decrease (5 wt%) by the acid- or base-impregnated samples carbonized at 600 °C. This suggests higher occurrence of oil adsorption-enhancing surface functional groups such as carbonyl, carboxyl and phenolic in the former sample.     

Hydrogen production by catalytic steam reforming of acetic acid,a model compound of biomass pyrolysis liquids

An environmentally friendly and cost-competitive way of producing hydrogen is the catalytic steam reforming of biomass pyrolysis liquids, known as bio-oil, which can be separated into two fractions: ligninic and aqueous. Acetic acid has been identified as one of the major organic acids present in the latter, and catalytic steam reforming has been studied for this model compound. Three different Ni coprecipitated catalysts have been prepared with varying nickel content (23, 28 and 33% expressed as a Ni/(Ni + Al) relative at.% of nickel). Several parameters have been analysed using a microscale fixed-bed facility: the effect of the catalyst reduction time, the reaction temperature, the catalyst weight/acetic acid flow rate (W/m_HAc) ratio, and the effect of the nickel content. The catalyst with 33% Ni content at 650 °C showed no significant enhancement of the hydrogen yield after 2 h of reduction compared to 1 h under the same experimental conditions. Its performance was poorer when reduced for just 0.5 h. For W/m_HAc ratios greater than 2.29 g catalyst min/g acetic acid (650 °C, 33% Ni content) no improvement was observed, whereas for values lower than 2.18 g catalyst min/g acetic acid a decrease in product gas yields occurred rapidly. The temperatures studied were 550, 650 and 750 °C. No decrease in product gas yields was observed at 750 °C under the established experimental conditions. Below this temperature, the aforementioned decrease became more important with decreasing temperatures. The catalyst with 28% Ni content performed better than the other two.     

Preparation of aqueous crosslinked dispersions of functionalized poly(d,l-lactic acid) with a thermomechanical method

Aqueous crosslinked microparticle dispersions were prepared from a copolymer of d,l-lactic acid, 1,4-butanediol, and itaconic acid with a thermomechanical method. The copolymer was prepared in one step polycondensation reaction using Sn(Oct)₂ as a catalyst. A polymer with M_n of 2800 g mol^?1 and a molecular weight distribution of 1.41 was obtained (as determined by SEC), that contained double bonds introduced by the itaconic acid monomer units (6 mol-%, as determined by NMR). Crosslinking ability of the prepared copolymer was demonstrated in bulk by adding a thermal initiator and altering amounts of ethylene glycol dimethacrylate (EGDMA) crosslinking agent into molten polymer at 60–150 °C. A crosslinked gel was formed in less than 15 min at 80 °C when 10 wt.% of EGDMA was added and benzoyl peroxide (BPO) was used as the initiator. Aqueous dispersions were prepared of the non-crosslinked copolymer with a thermomechanical method that involved slow addition of aqueous polyvinyl alcohol (PVA) solution into molten copolymer at 60 °C under shear. Dispersions were prepared with 10 wt.% of EGDMA and 2 wt.% of BPO. Crosslinking of the dispersed microparticles was achieved by heating the dispersions at 80 °C for 30 or 60 min. The dispersions were characterized by SEM, DSC, TGA, FT-IR, solid state NMR, and gel content measurements. The effect of crosslinking was clearly seen in SEM images of films cast from the dispersions. The films cast from non-crosslinked dispersions had smooth morphology whereas in films cast from crosslinked dispersions separate spherical particles were observed. During the crosslinking reactions, glass transition temperatures increased (as determined by DSC), thermal stability of the samples increased (as determined by TGA), and the gel content of the samples increased.     

Stability of NF membranes under extreme acidic conditions

Two commercial nanofiltration (NF) membranes (FilmTec NF-45 and Desal-5 DK) and two new NF-1 membranes made by BPT (Bio Pure Technology) for the purpose of a European Union funded research project (RENOMEM) were tested under extreme acidic conditions. The polyethersulphone (PES) ultrafiltration (UF) supports used for casting the BPT-NF-1 membranes were also tested under similar conditions. The 006 and 015 UF supports were found to be stable in 5% nitric acid at 20 and 80 °C for 4 and 3 months, respectively. Both supports (006 and 015) showed a significant reduction in flux after immersion in sulphuric acid at both temperatures. The BPT-NF-1 membranes showed excellent resistance to 20% sulphuric acid for up to 4 months at 20 °C but were attacked by the nitric acid solution. The resistance of the two commercial membranes in 20% sulphuric acid at 20 °C was generally lower than that of the BPT-NF-1 membranes. The NF-45 membrane was slightly more stable in 5% nitric acid at 20 °C. Degradation of the membrane occurred only after 2 months while both the Desal-5 DK and BPT-NF-1 membranes degraded during the first month. At the higher temperature of 80 °C in 5% nitric acid all membranes degraded in the first month.The cause of membrane degradation was attributed to oxidation of the thin NF selective skin layer in nitric acid and to acid-catalysed hydrolysis of this layer in sulphuric acid. Knowing the cause of membrane degradation is a step forward in developing a better and more stable nanofiltration membrane.     

Thermal behaviour of malonic acid,sodium malonate and its compounds with some bivalent transition metal ions

Characterization, thermal stability and thermal decomposition of transition metal malonates, MCH₂C₂O₄·nH₂O (M = Mn(II), Fe(II), Co(II), Ni(II), Cu(II), Zn(II)), as well as, the thermal behaviour of malonic acid (C₃H₄O₄) and its sodium salt (Na₂CH₂C₂O₄·H₂O) were investigated employing simultaneous thermogravimetry and differential thermal analysis (TG-DTA), differential scanning calorimetry (DSC), infrared spectroscopy, TG-FTIR system, elemental analysis and complexometry. The dehydration, as well as, the thermal decomposition of the anhydrous compounds occurs in a single step. For the sodium malonate the final residue up to 700 °C is sodium carbonate, while the transition metal malonates the final residue up to 335 °C (Mn), 400 °C (Fe), 340 °C (Co), 350 °C (Ni), 520 °C (Cu) and 450 °C (Zn) is Mn₃O₄, Fe₂O₃, Co₃O₄, NiO, CuO and ZnO, respectively. The results also provided information concerning the ligand's denticity, thermal behaviour and identification of some gaseous products evolved during the thermal decomposition of these compounds.     

Gold & silver nanoparticles supported on manganese oxide: Synthesis,characterization and catalytic studies for selective oxidation of benzyl alcohol

Nano-gold and silver particles supported on manganese oxide were synthesized by the co-precipitation method. The catalytic properties of these materials were investigated for the oxidation of benzyl alcohol using molecular oxygen as a source of oxygen. The catalyst was calcined at 300, 400 and 500 °C. They were characterized by electron microscopy, powder X-ray diffraction (XRD) and surface area. It was observed that the calcination temperature affects the size of the nanoparticle, which plays a significant role in the catalytic process. The catalyst calcined at 400 °C, gave a 100% conversion and >99% selectivity, whereas catalysts calcined at 300 and 500 °C gave a conversion of 69.51% and 19.90% respectively, although the selectivity remains >99%.     

Sulfonated polyethersulfone Cardo membranes for direct methanol fuel cell

Novel proton conducting membranes, sulfonated polyethersulfone Cardo (SPES-C), were prepared with concentrated sulfonic acid at room temperature. The degree of sulfonation was controlled by reaction time. Their proton conductivity and methanol permeability as a function of temperature were investigated. The SPES-C membranes with 70% DS were still not water soluble and had low degree of swelling. With the level of 70% sulfonation, proton conductivity was 0.011 S/cm at 80 °C, 0.0338 S/cm at 110 °C, which approached that of Nafion^® 115 membrane at the same conditions. Methanol permeability of SPES-C membranes was considerably smaller than that of Nafion^® 115 membrane over the temperature 25–80 °C.     

Lewis acid mediated asymmetric Diels–Alder reactions of chiral 2-phosphonoacrylates

2-Phosphonoacrylates containing four chiral alcohol auxiliaries were efficiently prepared and evaluated in Lewis acid mediated Diels–Alder reactions. Under the activation of SnCl₄, all reactions performed in CH₂Cl₂ at ?65 °C exclusively afforded the endo (endo-to-carboxylate) cycloadducts with dr’s ranging from 50:50 to >99:1. The best facial selectivity was obtained from the substrate bearing a (?)-phenylmenthyl group, to give adducts as (dr >99:1) or almost as (dr = 99:1) single diastereomers. Detailed strategies for the structural elucidation of the cycloadducts as well as a rationalization of the observed stereoselectivity are described.     

Investigation of steam reforming of acetic acid to hydrogen over Ni–Co metal catalyst

Catalytic generation of hydrogen by steam reforming of acetic acid over a series of Ni–Co catalysts have been studied. The catalyst with the molar ratio of 0.25:1 between Ni and Co was superior to other catalysts. The effects of reaction temperature, liquid hourly space velocity (LHSV) and molar ratios of steam-to-carbon (S/C) were studied in detail over this catalyst. At T = 673 K, LHSV = 5.1 h⁻¹, S/C = 7.5:1, the catalyst exhibited the best performances. Acetic acid was converted completely to hydrogen, while H₂ selectivity reached up to 96.3% and CO₂ selectivity up to 98.1% was obtained, respectively. Ni–Co catalyst showed rather stable performances for the 70 h time-on-stream without any deactivation.     

Swelling and thermodynamic studies of temperature responsive 2-hydroxyethyl methacrylate/itaconic acid copolymeric hydrogels prepared via gamma radiation

The copolymeric hydrogels based on 2-hydroxyethyl methacrylate (HEMA) and itaconic acid (IA) were synthesized by gamma radiation induced radical polymerization. Swelling and thermodynamic properties of PHEMA and copolymeric P(HEMA/IA) hydrogels with different IA contents (2, 3.5 and 5 mol%) were studied in a wide pH and temperature range. Initial studies of so-prepared hydrogels show interesting pH and temperature sensitivity in swelling and drug release behavior. Special attention was devoted to temperature investigations around physiological temperature (37 °C), where small changes in temperature significantly influence swelling and drug release of these hydrogels. Due to maximum swelling of hydrogels around 40 °C, the P(HEMA/IA) hydrogel containing 5 mol% of IA without and with drug-antibiotic (gentamicin) were investigated at pH 7.40 and in the temperature range 25–42 °C, in order to evaluate their potential for medical applications.     

Curie-point pyrolysis–gas chromatography–mass spectroscopic analysis of theabrownins from fermented Zijuan tea

Zijuan tea theabrownins (ZTTBs) was extracted from a type of fermented Zijuan tea and separated into fractions according to molecular weight. The extract was found to contain predominantly two fractions: <3.5 kDa and >100 kDa. These two fractions were analyzed for chemical composition, structural characteristics by Curie-point pyrolysis–gas chromatography–mass spectroscopy (CP-Py–GC/MS). The affects of pyrolysis temperature on pyrolytic products were also investigated. The fraction >100 kDa produced 50 GC/MS peaks during pyrolysis at 280 °C, 70 peaks at 386 °C, and 134 peaks at 485 °C. Fourteen of the products formed at 280 °C, 12 of those formed at 386 °C, and 21 of those formed at 485 °C were identified with match qualities of greater than 80%. The fraction <3.5 kDa gave 51 peaks during pyrolysis at 280 °C, 99 peaks at 386 °C, and 257 peaks at 485 °C. Six products formed at 280 °C, four products formed at 386 °C, and 61 products formed at 485 °C were identified with match qualities of greater than 80%. Pyrolysis temperatures of 485 °C and 386 °C were found suitable for the two fractions respectively. CP-Py–GC/MS revealed that, the fraction >100 kDa mainly consisted of phenolic pigments, esters, proteins, and polysaccharides, while the fraction <3.5 kDa contained no polysaccharide. CP-Py–GC/MS is an effective tool for the composition difference and structural characteristics of ZTTBs as well as other complex macromolecular plant pigments.     

Synthesis of aryl alkynyl carboxylic acids and aryl alkynes from propiolic acid and aryl halides by site selective coupling and decarboxylation

The coupling of propiolic acid with aryl iodides afforded the aryl alkynyl carboxylic acids and aryl alkynes in generally good yields. Aryl alkynyl carboxylic acids were obtained when the reaction was performed in the presence of Pd(PPh₃)₂Cl₂ (2.5 mol %), dppb (5.0 mol %) and DBU (5 equiv) at 50 °C. For the synthesis of the terminal aryl alkynes, the reaction was conducted in the presence of Pd(PPh₃)₂Cl₂ (2.5 mol %), dppb (5.0 mol %), DBU (5.0 equiv), and Cu(acac)₂ (10 mol %) at 25 °C for 5 h, and further reacted at 60 °C for 6 h.