Producing ashless coal extracts by microwave irradiation

To produce ashless coal extracts, three Turkish coals were extracted with N-methyl-2-pyrrolidinone (NMP), NMP/ethylenediamine (EDA) (17/1, vol/vol) mixture and NMP/tetralin (9/1, vol/vol) mixture through thermal extraction and microwave extraction. Solvent extraction by microwave irradiation (MI) was found to be more effective than that by thermal extraction. Extraction yield of coals in NMP enhanced by addition of a little EDA, but tetralin addition showed variances according to extraction method used. While tetralin addition caused a decrease in the thermal extraction yield, it increased the yield of the extraction by MI. Following the extraction, the solid extracts were produced with ash content ranging from 0.11% to 1.1%. Ash content of solid extract obtained from microwave extraction are less than ash contents of solid extracts obtained from thermal extraction.     

Possible fatty acyl pheromone precursors in Spodoptera littoralis. Search for 11- and 12-hydroxytetradecanoic acids in the pheromone gland

Lipidic extracts of Spodoptera littoralis pheromone glands submitted to acid methanolysis using: (i) sulfuric acid/methanol/benzene (0.1∶4∶2, by vol) at 90°C for 1 h; (ii) 12 N HCl/methanol (1∶2; vol/vol) at 90°C for 1 h, or (iii) 14% BF₃-MeOH at 90°C for 1 h did not reveal the presence of either 11- or 12-hydroxytetradecanoic acid in the extracts, as concluded from the gas chromatography-mass spectrometry analyses. Under the above methanolysis conditions, a synthetic sample of methyl (14, 14, 15-²H₃) 12-hydroxytetradecanoate remained unaltered. These results may indicate that formation of (E)-11-tetradecenoic acid from tetradecanoic acid does not occur in the pheromone gland by dehydration of an intermediate hydroxyacid. Acid methanolysis of a lipidic extract using BF₃-MeOH led to the formation of a mixture of methoxy fatty acid methyl esters, identified by gas chromatography-mass spectrometry. These methoxy derivatives should arise from BF₃-catalyzed addition of methanol to the double bond of the natural monounsaturated fatty acyl derivatives present in the gland. Thus, under the same conditions, a synthetic sample of methyl (Z)-11-tetradecenoate was partially transformed into methyl 11-methoxytetradecanoate and methyl 12-methoxytetradecanoate. This reaction might be a useful alternative procedure to obtain methoxy derivatives of olefins, which are very helpful for the structural characterization of the parent alkenes.     

Characterization of the heavy products of coal pyrolysis

In order to obtain information about the production mechanism of large molecules in coal pyrolysis, a subbituminous and two bituminous coals were heated at 500 ° C for 30 s under vacuum. The heavy products were dissolved in tetrahydrofuran (THF) and analysed by ¹H n.m.r. spectroscopy and gel-permeation chromatography in an atmospheric-pressure column. Parallel GPC, ¹H n.m.r. and ¹³C n.m.r. studies were conducted with THF extracts of the same coals. The results are combined with elemental analysis data to obtain structural parameters of the extracts and pyrolysates.     

Prediction of the Elution Profile of Aromatic Compounds in RP‐HPLC

Abstract

An efficient prediction method for the elution profile was used to separate aromatic compounds such as benzene, toluene, chlorobenzene, o‐xylene, and 1,2‐dichlorobenzene by RP‐HPLC. The retention factor and bandwidth were predicted under linear‐gradient condition with the three retention models. The elution profiles were calculated based on the linear and quadratic equations of retention factor, lnk=lnk _w +S?, lnk=L+M?+N?², k=A+B/?, where ? was the vol.% of methanol. The elution profiles were calculated by the Gaussian distribution with obtained retention factor and bandwidth. Two kinds of experiments were performed; one is the isocratic runs to estimate the coefficients of three retention models, and the other is the linear gradient runs that were carried out with same initial mobile phase composition (water/methanol=96/4, vol.%), two final mobile phase compositions (water/methanol=24/76 and 40/60, vol.%), and three gradient times (20, 40, and 60 min). The predicted elution profiles by the three retention models and new prediction method have good agreement with experimental data in the employed gradient conditions. The minimum average errors of calculated and experimental results of aromatic compounds were lower than 3.5% by Bi‐poly equation.     

Radical scavenging activity of canola hull phenolics

Possible use of canola hulls as a source of natural anti-oxidants was explored. Cyclone canola hulls were extracted with methanol (30 to 80%, vol/vol) and acetone (30 to 80%, vol/vol). The free radical-scavenging activity of phenolic extracts so prepared was evaluated using the 2,2′-azinobis-(3-ethylbenzothiazoline-6-sulfonate) (ABTS) radical ion (ABTS^o−), 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical, and chemiluminescence assays. The total content of phenolics in prepared extracts from canola hulls ranged from 15 to 136 mg sinapic acid equivalents per gram of extract. Higher levels of condensed tannins were detected in the acetone extracts than in the corresponding methanolic counterparts. Seventy and 80% (vol/vol) acetone extracts displayed markedly stronger antioxidant activity than any of the other extracts investigated. Statistically significant linear correlations were found between TEAC (Trolox equivalent antioxidant capacity) values (expressed in mM of Trolox equivalents per gram of extract) and total pehnolics, TEAC and total condensed tannins (i.e., determined using the modified vanillin and pronthocyanidin assays), as well as TEAC and protein precipitation activity of phenolic extracts (i.e., measured using the dye-labeled assay). The antioxidant activities of extracts as determined by the ABTS^o− radical ion assay correlated highly with those of the chemiluminescence and DPPH radical assays.     

Analysis of soybean lecithins and beef phospholipids by HPLC with an evaporative light scattering detector

Linear (r > 0.99) calibration curves were obtained for 10–150 μg of phosphatidylethanolamine (PE), 10–75 μg of phosphaditylinositol (PI), phosphaditylserine (PS) and lysophosphatidylethanolamine, 10–100 μg of phosphatidic acid (PA) and 10–250 μg of phosphatidylcholine (PC) by high-performance liquid chromatography analyses with an evaporative light scattering detector, a Zorbax 7-μm silica column and gradient elution with two solvents. One solvent (A) contained 415 mL isooctane (IOCT), 5 mL tetrahydrofuran (THF), 446 mL isopropanol (IPA), 104 mL CHCl₃ and 30 mL H₂O; and the other solvent (B) contained 216 mL IOCT, 4 mL THF, 546 mL IPA, 154 mL CHCl₃ and 80 mL H₂O. The gradient in which 100% A linearly changed to 100% B in 20 min followed by 12 min of 100% B and then a linear change to 100% A during 5 min separated PE, PS and PC in soybean lecithins and beef lipids, but failed to resolve PI and PA. In these same samples, less polar lipids were separated from phospholipids (PL) by elution from Bond-Elut silica columns with diethyl ether/hexane (20:80, vol/vol), and PL were recovered by elution with methanol. This procedure is useful for concentration of minor lipid components. Levels of PE, PI-PA, PS and PC were higher in granular than in liquid lecithin, and PC was the most abundant PL in soybean lecithins and beef lipids.     

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.     

Influence of the dilute‐solution properties of cellulose acetate in solvent mixtures on the morphology and pervaporation performance of their membranes

The pervaporation performance of cellulose acetate (CA) membranes prepared from acetone (AC), acetone/tetrahydrofuran (AC/THF), acetone/chloroform (AC/CF), and acetone/cyclohexane (AC/CYH) was studied for separating MeOH/MTBE (methyl tert‐butyl ether) mixture with 5 (wt) % MeOH. The dilute‐solution properties and Huggins constant (K_H) of CA dissolved in AC and AC/solvent mixtures with 15 vol % of the second solvent (tetrahydrofuran, chloroform, or cyclohexane) were examined. J and α of the CA membranes were affected by the types of solvent mixtures used to prepare the casting solutions. Under the same conditions, the membrane with AC/CYH had the highest J value and the lowest α value, and it was followed by the membranes with AC/CF, AC/THF, and AC. The increasing value of J and decreasing value of α for the CA membranes from different solvent mixtures were in good agreement with the increasing value of K_H of CA in corresponding solvent mixtures. Furthermore, differences in the morphology from scanning electron microscopy images of the cross sections or from atomic force microscopy photographs of the surfaces of the membranes existed, and they provided proof of the different pervaporation performances of the CA membranes prepared from AC and AC/solvent mixtures. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97:1891–1898, 2005     

Thermodynamic and hydrodynamic properties of the the systems polymer—tetrahydrofuran—water: 1. Solution properties of polystyrene

Tetrahydrofuran (THF) is a solvent widely applied in polymer science and technology. However, because of its hygroscopic nature THF may often contain water considerably influencing the properties of the corresponding polymer solutions. In the first part of a series devoted to this problem, cloud point titrations and viscosity measurements were performed in the system polystyrene (PS)-THF-water. The limiting viscosity numbers of polystyrene considerably depended on the water content already in the domain of azeotropic composition, i.e. at about 4.5 vol.% of water. The constants of the Mark—Houwink equation, K and a were determined in pure THF and in mixtures containing up to 8.2 vol.% of water and compared with those for PS-THF found in the literature. The corresponding unperturbed dimensions were determined by various extrapolation procedures and were found to depend on solvent composition. Simultaneously, polymer-mixed solvent interaction parameters B were determined and discussed. Two theta compositions were observed: at about 7.7 vol.% of water for second virial coefficient A₂ = 0, and about 8.12 vol.% for a = 0.5. This agrees with the hypothesis of Dondos and Benoit and indicates the presence of preferential solvation in the system.     

Structural analysis of quinoline and pyridine extracts of coals

Various ranks of coals were extracted in an autoclave with quinoline at 350–380°C for 1–4 h. More than 50% of bituminous coals were dissolved, and almost 100% of Japanese bituminous coals in particular were dissolved. These quinoline extracts were further extracted by shaking with pyridine at room temperature for 8 h and the extraction yield attained a maximum of 85%. NMR spectra of these extracts were recorded using deuteroquinoline and deuteropyridine as solvent. The structural indices calculated from the observed spectra showed a good agreement between quinoline extracts and pyridine extracts, which indicates that the coal structure is almost homogeneous. The aromatic ring number in structural units varied from 1–2 in younger coals to 5 in coking coals. f_a increased from 0.7 for younger coals to 0.9 for coking coals. The aliphatic carbon number per structural unit increased from younger to older coals, but foreign coals had smaller values than Japanese coals, which corresponds well with higher values of H/C in Japanese coals.     

Chemical looping combustion characteristics and kinetic behaviour of Sr-doped perovskite-type CaFeO3 oxygen carriers: Theoretical and experimental investigations

Oxygen carriers (OCs) with typical perovskite structures have attracted attention for use in chemical looping combustion (CLC) owing to their unique tunable structures and excellent performance. Thus, a further improvement in the reactivity and a deep understanding of the kinetic behaviour in CLC are highly desirable for such perovskite OCs. In this study, a series of Sr-doped perovskite-structured CaFeO₃ OCs (denoted as Sr_xCa_1−xFeO₃) were synthesized. The CLC characteristics, kinetic behaviour, and doping mechanism were systematically investigated via experiments and density functional theory (DFT) calculations. The activation energies of Sr_xCa_1−xFeO₃ OCs with various Sr contents were found to be in the range of 36.6–40.1 kJ/mol and lower than that of CaFeO₃ (62.7 kJ/mol), indicating that the Sr doping enhanced the reactivity of CaFeO₃. Among the OCs, Sr_0.4Ca_0.6FeO₃, which had the lowest activation energy and the fastest release of lattice oxygen, was regarded as the optimum OC. DFT calculations indicated that the reaction energy barrier of Sr_xCa_1−xFeO₃ (0.73–1.06 eV) was lower than that of CaFeO₃ (2.18 eV). This suggests that Sr doping and the regulation of the reaction pathways are essential drivers for enhancing the reactivity of Sr_xCa_1−xFeO₃, which affects the release of lattice oxygen and the morphological properties of OC particles.     

Radiation-induced graft polymerization of 4-vinyl pyridine to styrene–butadiene–styrene triblock copolymer

The radiation-induced graft polymerization of 4-vinyl pyridine to styrene–butadiene–styrene triblock copolymer (SBS) was investigated. Relations between the rate of grafting and the dose rate when SBS was irradiated in 4-vinyl pyridine–methanol solution, and between the rate of grafting and 4-vinyl pyridine concentration of 4-vinyl pyridine–methanol solution have been investigated. An experiment that had been carried out on SBS immersed in various 4-vinyl pyridine concentration of 4-vinyl pyridine–methanol solutions showed that the extent of swelling of SBS by the various 4-vinyl pyridine–methanol solutions increased with increasing 4-vinyl pyridine concentration. The largest rate was found at 20 vol % 4-vinyl pyridine–methanol solution. The rate was smaller at the volume percent of 4-vinyl pyridine higher or lower than 20 vol %. On the assumption that the theory of homogeneous homopolymerization could be applied to this grafting reaction, the value of k_p²/k_t was obtained, where k_p and k_t are the propagation and termination constant, respectively. The value of k_p²/k_t greatly decreased with increasing adsorbed concentration of vinyl pyridine–methanol solution. This decrease of k_p²/k_t was explained by the fact that 4-vinyl pyridine and methanol absorbed in SBS acted as a plasticizer which increased the molecular motion of the polymer. The solvent effect on the graft polymerization was also investigated. The result was explained by solubility parameter. When the chosen solvent had better solubility with the polymer, the degree of grafting was smaller. That was connected with the extent of the polymer chain mobility.     

Low-temperature phase behavior of vegetable oil/co-solvent blends as alternative diesel fuel

Vegetable oils (triacylglycerols) have many characteristics that make them attractive candidates as renewable alternative fuels for compression-ignition (diesel) engines. Unfortunately, vegetable oils are too viscous to be compatible with modern direct-injection diesel fuel systems and engines. Co-solvent blending is a simple and flexible technology that reduces viscosity by mixing the oil with low molecular weight alcohol. A co-solvent (A), consisting, of surfactant plus an amphiphilic compound, is added to solubilize otherwise nearly immiscible oil-alcohol mixtures into a single-layer (isotropic) solution. This work examines low-temperature phase behavior of two soybean oil (SBO)/methanol mixtures solubilized by A=unsaturated long-chain (C₁₈) fatty alcohol/medium-chain alkanol (n-butanol and 2-octanol), one SBO/methanol mixture solubilized by A=triethylammonium linoleate/2-octanol, and one SBO/95 wt% ethanol (E95) mixture solubilized by n-butanol. The E95-blend was further blended in 1∶1 (vol/vol) mixtures with No. 2 diesel fuel. Two types of anisotropic phase behavior were observed; formation of a cloudy layer of solid crystals suspended in bulk solution (Type 1) and formation of two immiscible liquid layers (Type II). The type of phase separation in a given solution was influenced by phase separation temperature (T _ϕ) relative to the crystallization characteristics of compounds in the SBO and fatty alcohol or amine constituents present in solution. Solutions with relatively low T _ϕ values experienced crystallization of small solid particles favoring Type 1 separations. Conversely, solutions with T _ϕ sufficient to avert crystallization of high melting point compounds favored Type II separations where T _ϕ=critical solution temperature (T _critical). Increasing the A/oil (SBO or No. 2 diesel/SBO mixture) mass ratio decreased T _ϕ while increasing the mass fraction of alcohol (methanol or E95) increased T _ϕ. This work shows that vegetable oil/A-based blends can be formulated with cold flow properties superior with respect to cloud point and comparable with respect to kinematic viscosity (v) of methyl soyate (biodiesel), either neat or blended with petroleum middle distillates. Retired     

Free radical-scavening activity of phenolics by reversed-phase TLC

A method was developed to measure the radicalscavenging activity of compounds separated by reversed-phase TLC (RP-TLC) using phenolic acids as model analytes. TLC separation was followed by dipping the plate in a 0.04% (wt/vol) solution of 1,1-diphenyl-2-picrylhydrazyl (DPPH) in methanol. The compounds possessing radical-scavenging activity were detected as bright yellow bands against a purple background. A video documentation system based on a CCD video camera was used for the detection and quantification of the activity. The developed RP-TLC-DPPH method was compared to the widely used spectrophotometric DPPH assay. The results obtained by the two methods correlated well, apart from syringic acid, ascorbic acid, and n-propyl gallate, which proved to be outliers in the regression analyses. The correlation coefficient, after, excluding outliers, was r ²=0.923. The RP-TLC-DPPH method was applied for the measurement of free radical-scavenging activity of rapeseed meal fractions. A total of 10 separated zones with free radical-scavening activity were detected, with R _f values ranging from 0.04 to 0.85. The results show that the method can be used for the effective fractionation and analysis of potential antioxidative compounds in natural extracts.     

Rapid separation of the major phospholipid classes on a single aminopropyl cartridge

A rapid method for the separation of the individual phospholipid classes phosphatidylcholine (PC), phosphatidylethanolamine (PE), phosphatidylserine (PS) and phosphatidylinositol (PI) by a single solid-phase extraction was developed. PC, PE, PS and PI were sequentially eluted from aminopropyl bonded silica with acetonitrile/n-propanol (2∶1, vol/vol), methanol, isopropanol/methanolic HCl (4∶1, vol/vol) and methanol/methanolic HCl (9∶1, vol/vol). Standard recoveries were over 95% for PC and PE and over 85% for PS and PI with undistorted fatty acid composition. The separation of complex lipid mixtures on aminopropyl minicolumns can be refined to the level of individual phospholipid classes.     

Extraction of coals with CS2-N-methyl-2-pyrrolidinone mixed solvent at room temperature Effect of coal rank and synergism of the mixed solvent

Coals (from lignite to anthracite) were extracted at room temperature with CS₂-N-methyl-2-pyrrolidinone (MP) mixed solvent (1:1 by volume), which was found to be a very efficient solvent for the extraction of bituminous coals in a previous study. High yields of 30–66% (daf) were obtained for 29 of the 49 bituminous coals (C%76.9–90.6% daf) examined. The anthracite, subbituminous coals and lignites did not give high yields. The results of the characterization of the raw coals, extracts and residues suggest that reactions between the coals and the solvents do not occur to a significant extent during the extraction. The synergistic effect, i.e. the large increase in yield and rate for the mixed solvent compared with those for CS₂ and MP alone has been explained by increasing solubility and diffusibility of the extracts and increasing swelling of the coals, in the mixed solvent. The mixed solvents of CS₂ with quinoline, pyridine and THF gave lower extraction yields than the CS₂-MP mixed solvent.     

Chromatographic separation of glucopyranosyl sinapate from canola meal

The compound 1-O-β-D glucopyranosyl sinapate (GPS), a phenolic glycoside, was separated from ethanolic extracts of defatted canola meal by a two-step chromatographic method. The first step involved Sephadex LH-20 chromatography with methanol as the eluting solvent. The solvent from the fraction containing GPS was evaporated, and glucopyranosyl sinapate was subsequently separated by a semi-preparative high-performance liquid chromatography method with an RP-18 column and a mobile phase consisting of water/acetonitrile/acetic acid (88∶10∶2, vol/vol/vol).     

Characterization of coals from the Luzhki section of the Zabitui deposit

The composition and properties of coals from the Luzhki section of the Zabitui deposit in the Irkutsk Basin were studied. It was found that Luzhki coals are sulfur coals (S ^d to 4.76%) with a high yield of volatile substances (V ^daf = 42.8–53.6%) and the heat of combustion Q _s ^daf = 26.0–31.8 MJ/kg. Sulfur species in coals and semicokes obtained in a Fischer retort were determined. The concentrations of trace elements, including toxic elements, were evaluated.     

Low-temperature flow properties of vegetable oil/cosolvent blend diesel fuels

Vegetable oils are an attractive renewable source for alternative diesel fuels. However, the relatively high kinematic viscosity of vegetable oils must be reduced to make them more compatible with conventional compression-ignition engines and fuel systems. Cosolvent blending is a low-cost and easy-to-adapt technology that reduces viscosity by diluting the vegetable oil with a low-M.W. alcohol (methanol or ethanol). The cosolvent (A), which consists of one or more amphiphilic compounds, is added to solubilize the otherwise nearly immiscible oil-polar alcohol mixture. This work investigates cold flow properties and phase equilibrium behavior associated with blends consisting of soybean oil (SBO) and methanol where A=8∶1 (mol) n-butanol/oleyl alcohol; 6∶1 (mol) 2-octanol/triethylammonium linoleate; and 4∶1 (mol) 2-octanol/Unadol 40 (alcohols from SBO FA); and a blend of 2∶1 (vol/vol) No. 2 diesel fuel/SBO and 95% ethanol where A=n-butanol. Cloud point (CP), pour point, cold filter plugging point (CFPP), and low-temperature flow test (LTFT) results were compared with corresponding phase separation temperature (T _ϕ) data measured at equilibrium. Although CP data were measured under non-equilibrium experimental conditions, a nearly linear correlation was found between T _ϕ and CP. Statistical analysis showed that T _ϕ may also be correlated with CFPP and LTFT. Analysis of heating and cooling DSC curves indicated that peak temperatures may be employed to predict cold flow properties and T _ϕ behavior for SBO/cosolvent blends. Cooling curve parameters correlated more readily than heating curve parameters. Finally, relatively low quantities of heat evolved during freezing indicated that crystallization in the SBO/cosolvent blends studied in this work occurs easily during cooling.     

Biodiesel synthesis via homogeneous Lewis acid-catalyzed transesterification

Lewis acids (AlCl₃ or ZnCl₂) were used to catalyze the transesterification of canola oil with methanol in the presence of terahydrofuran (THF) as co-solvent. The conversion of canola oil into fatty acid methyl esters was monitored by ¹H NMR. NMR analysis demonstrated that AlCl₃ catalyzes both the esterification of long chain fatty acid and the transesterification of vegetable oil with methanol suggesting that the catalyst is suitable for the preparation of biodiesel from vegetable oil containing high amounts of free fatty acids. Optimization by statistical analysis showed that the conversion of triglycerides into fatty acid methyl esters using AlCl₃ as catalyst was affected by reaction time, methanol to oil molar ratio, temperature and the presence of THF as co-solvent. The optimum conditions with AlCl₃ that achieved 98% conversion were 24:1 molar ratio at 110 °C and 18 h reaction time with THF as co-solvent. The presence of THF minimized the mass transfer problem normally encountered in heterogeneous systems. ZnCl₂ was far less effective as a catalyst compared to AlCl₃, which was attributed to its lesser acidity. Nevertheless, statistical analysis showed that the conversion with the use of ZnCl₂ differs only with reaction time but not with molar ratio.