Conversion of brown coals in aqueous and toluene-containing media under supercritical conditions in the presence of catalysts

The conversion of brown coals from the Borodino and Kangalas deposits in an aqueous medium and in a mixture of toluene with water was studied under supercritical conditions over the temperature range of 375–550°C and at pressures from 22 to 40 MPa. It was found that the methanation, hydrolysis, and oxidation reactions of brown coals with the predominant formation of gaseous products (methane, carbon dioxide, and hydrogen) prevailed in an aqueous medium. Liquid substances were formed in an insignificant amount. In the toluene solvent under supercritical conditions at 440°C, the addition of a small water amount (15%) stimulated the degradation of coals with the predominant formation of liquid products and moderate gas formation. The use of calcium oxide and sodium hydroxide as catalysts increased the yields of liquid products. It was noted that the reactivity of Kangalas coal in this process was higher than that of Borodino coal.     

Pyrolysis of kraft lignin in molten ZNCL2-KCL media with tetralin vapor addition

Kraft lignin was pyrolyzed in molten salt media of ZnCl₂-KCl mixture with tetralin vapor added in 0.4 and 4 mol% diluted with N₂ in the temperature range of 400 to 700°C. The gas chromatographic analyses of pyrolysis products revealed that the yield of H₂ was not increased by tetralin vapor addition. This fact implies that the hydrogen radical produced from tetralin is consumed in the formation of phenolic compounds and light liquids but not in the formation of H₂. p-Cresol was the most abundant phenolic compound. The yield of total phenolic compounds with 4 mol% tetralin vapor added was increased by ca. 80% as compared to that in neat pyrolysis of Kraft lignin.     

Production of hydrocarbons by pyrolysis of methyl esters from rapeseed oil

The pyrolysis of a mixture of methyl esters from rapeseed oil has been studied in a tubular reactor between 550 and 850°C and in dilution with nitrogen. A specific device for the condensation of cracking effluents was used for the fractionated recovery of liquid and gaseous effluents, which were analyzed on-line by an infrared analyzer and by gas chromatography. The cracking products in the liquid effluent were identified by gas chromatography/mass spectrometry coupling. The effects of temperature on the cracking reaction were studied for a constant residence time of 320 ms and a constant dilution rate of 13 moles of nitrogen/mole of feedstock. The principal products observed were linear 1-olefins,n-paraffins, and unsaturated methyl esters. The gas fraction also contained CO, CO₂, and H₂. The middle-chain olefins (C₁₀–C₁₄ cut) and short-chain unsaturated esters, produced with a high added value, had an optimum yield at a cracking temperature of 700°C.     

Effects of hydrogen pressure on hydrogasification of Taiheiyo (Japan) coal

The non-isothermal hydrogasification of Taiheiyo coal is studied at hydrogen pressures up to 5 MPa and temperatures of 900 °C using a high-pressure thermobalance and tubular reactor. Gaseous products are analysed and liquid products obtained from the mass balance. Rates of formation of methane increased with temperature to two maxima, at 550 °C and at 750 °C. Corrections to rate are necessary because of appreciable weight losses. In the temperature range 650–800 °C the activation energy of methane formation is ≈ 115 kJ mol^?1. Below 55 °C, the pressure dependence of reaction is 0.3, becoming first order at higher temperatures. Rates of formation of methane and ethane indicate a similar mechanism of formation. Rates of formation of liquid hydrocarbons maximize at ≈ 450 °C and increase with hydrogen pressure.     

HYDROGENOLYSIS OF DIPHENYL ETHER

Hydrogenolysis of diphenyl ether was investigated at 550°C and 620°C and at pressures up to 1850 psig. Primary interest was the elucidation of cracking patterns at a hydrogen to diphenyl ether molar ratio of 2:1.

The primary reaction was C—O—C bond cleavage resulting in the formation of benzene and phenol. The secondary reaction was ring cracking resulting in the formation of gaseous components namely, carbon monoxide, carbon dioxide and lighter hydrocarbons.     

Hydrogenation of liddell vitrinite: Effects of metal halide catalysts in the temperature range 200–480°C

A vitrinite concentrate prepared from the Liddell Seam (high volatile bituminous coal, NSW, Australia) has been hydrogenated in an unstirred 50 cm³, batch autoclave at reaction temperatures between 200 and 480°C in the presence of metal halides (SnCl₁ or ZnCl₁) and/or alumina (α-Al₁O₃). A vehicle was not used. The influence of reaction temperature, metal halide and alumina on the composition of the products was studied by gas chromatography (GC), gel permeation chromatography (gpc), ¹H solution and ¹³C solid-state cross polarization (CP) nuclear magnetic resonance (nmr) spectroscopy and optical microscopy.The metal halides lower the temperature at which softening and agglomeration of vitrinite takes place. The resultant plastic isotropic material forms mesophase at temperatures above 400°C unless an inert diluent, i.e. alumina, is added. The alumina inhibits reactions involved in the formation of mesophase which would otherwise compete with hydrogenation reactions that yield hexane soluble material (oil).Above 400°C carbon monoxide, carbon dioxide and C₁-C₅ alkanes are the principal gaseous products. At lower temperatures, in the presence of alumina, ethylene is formed in the catalysed experiments; the ethylene is converted to ethane at higher temperatures. The structure of the hexane soluble products derived from vitrinite is also temperature dependent. Above 420°C much of the aliphatic component decomposes to yield further quantities of hydrocarbon gases. Tin(II) chloride and zinc chloride produce hexane soluble products of similar molecular composition, which suggests that they operate through a similar mechanism.The addition of alumina to the reaction mixture results in a more aromatic liquid product with shorter aliphatic carbon chains. Whether or not alumina is present, the aromaticity of the solid residues increases with increase in hydrogenation temperature. Thus the increased aromaticity of the liquid products is not caused by the extraction of a greater proportion of aromatic material from the coal with increase in the hydrogenation temperature. It follows that with increase in hydrogenation temperature an increasing proportion of the aliphatic material becomes transformed into aromatic compounds and/or gas.In summary, the results show that over a wide range of temperatures (200–480°C) the structure of the hexane soluble product depends on the thermal stability of the products and the degree of competition from reactions leading to mesophase formation, and not on the nature of the halide catalyst.     

Reduced Silver Salt of Wells-Dawson Heteropolyacid H6P2W18O62 as a Bi-Functional Catalyst

Silver salt preparation was obtained by neutralizing solution of H₆P₂W₁₈O₆₂ in water with solid Ag₂CO₃. In the introductory experiments the conditions of silver salt reduction with ethanol vapours were studied at 170–290 °C. At 250 °C and 2.5 h complete reduction to silver and free heteropolyacid was observed. During reduction with ethanol the initially not active salt became catalyst on which typical for free acid alcohol dehydration to ethylene occurred. In a series of experiments carried out within temperature range 210–290 °C ethanol conversion was studied on the catalyst previously reduced at 250 °C. When air was used as the carrier gas the bi-functional behavior of the catalyst was distinct, besides ethylene, diethyl ether and water, typical products of acid–base type catalytic reaction also comparable amount of acetaldehyde, the product of redox type reaction, was observed.     

Degradation of polystyrene in supercritical n-Hexane

Degradation of polystyrene was carried out in supercritical n-hexane under reaction temperature ranging from 330 °C to 390 °C, pressure ranging from 30 bar to 70 bar and reaction duration of 90 min. The conversion of polystyrene increased with rising temperature and pressure. The degradation performance was influenced by the temperature rather than applied pressure. Polystyrene rapidly degraded in 30 min after reaching a prescribed temperature ranging from 350 °C to 390 °C. At a prescribed temperature of 390 °C, the degree of degradation was higher than 90%. The degradation reaction was examined experimentally at a relatively low temperature of 330 °C. The degradation of polystyrene by using supercritical n-hexane has been found to be more effective compared to general pyrolysis (thermal degradation). Among the selectivity of liquid products, that of a single aromatic ring group like styrene at 390 °C increased up to 65% in 90 min. It was found from the analysis by a gel permeation Chromatograph (GPC), that high molecular-weight compounds decreased but oligomers increased with rising temperature.     

A non-isothermal experimental technique to study coal extraction with solvents in liquid and supercritical state

A non-isothermal experimental technique is presented to study the mechanism of coal extraction with solvents at sub- and super-critical temperatures between 20 °C and 550 °C and pressures up to 15 MPa. With slowly rising temperature, the formation rates of extract and gaseous coal decomposition products are measured in a fixed bed of coal, which is percolated by a pressurized solvent. Since the extraction temperature rises above the solvent critical temperature, both sub- and super-critical extraction are covered in one experiment. The formation rate profiles exhibit characteristic differences depending on coal type, solvent and extraction conditions. An interpretation of these differences makes it possible to separate overlapping effects of chemical reactions, phase equilibria and mass transport during coal extraction.     

Antioxidant Activities and Phenolic Compositions of Wheat Germ as Affected by the Roasting Process

Wheat germ is a good source for wheat germ oil, and it is a by‐product with highly concentrated nutrients from the wheat flour‐milling industries. In the present study, raw wheat germ was firstly heat‐treated at 180 °C for 20 min in a fluidized bed dryer, and further roasted at 180 °C for different periods of time. Roasting influence on total phenolic content (TPC), antioxidant activities, and phenolic compositions of wheat germ were evaluated. The roasting process significantly increased the TPC and antioxidant activities including free radical scavenging against DPPH and ABTS radicals, FRAP, and ORAC. In particular, the wheat germ roasted at 180 °C for 20 min showed higher antioxidant activity than those roasted at 180 °C for 5 and 10 min. Three major phenolic acids, namely, ferulic, chlorogenic, and caffeic acid, and four main flavonoids, namely, schaftoside and its isomers or adduct of sinapic acid were identified by HPLC. In general, the content of individual phenolic compounds decreased with prolongation of the roasting time except for ferulic acid. The results suggest that the antioxidant activities of wheat germ can be enhanced by roasting, and the enhancement effect might be partially attributed to the formation of Maillard reaction products (MRP).     

Enzymatic Production of Cocoa Butter Equivalents High in 1-Palmitoyl-2-oleoyl-3-stearin in Continuous Packed Bed Reactors

This study aimed to optimize the lipase-catalyzed transesterification of high oleic sunflower oil (A) with a mixture of ethyl palmitate and ethyl stearate (B) to produce cocoa butter equivalents with a weight ratio of 1-palmitoyl-2-oleoyl-3-stearoyl-rac-glycerol (POS) to total symmetric monounsaturated triacylglycerols (SMUT) that is similar to that of cocoa butter by response surface methodology. The reaction was performed in a continuous packed bed reactor, using 0.45 g of Lipozyme RM IM as the biocatalyst. The effects of temperature (Te), residence time (RT), substrate molar ratio (SR, B/A), and water content (WC) of the substrates on the composition of reaction products were elucidated using the models established. Optimal reaction conditions for maximizing total SMUT and POS contents while minimizing the levels of diacylglycerol formation and acyl migration were: Te, 60 °C; RT, 28.5 min; SR, 8.5; WC, 300 mg/kg. The contents of total SMUT, POS, and diacylglycerol in the reaction products and the content of palmitoyl and stearoyl residues at the sn-2 position of triacylglycerols in the products were 52.0, 25.1, 9.4, and 4.8 %, respectively, under these conditions. Successful scale-up of the reaction was achieved under the optimal conditions, using 5 g of the lipase. A silver-ion high performance liquid chromatography analysis showed that the products obtained by the larger scale reaction contained 49.1 % total SMUT and 6.1 % of their positional isomers.     

Thermogravimetric characteristics and kinetic study of biomass co-pyrolysis with plastics

The pyrolysis of pure biomass, high density polyethylene (HDPE), polypropylene (PP) and polyethylene terephthalate (PET), plastic mixtures [HDPE+PP+PET (1: 1: 1)], and biomass/plastic mixture (9: 1, 3: 1, 1: 1, 1: 3 and 1: 9) were investigated by using a thermogravimetric analyzer under a heating rate at 10 °C/min from room temperature to 800 °C. Paper was selected as the biomass sample. Results obtained from this comprehensive investigation indicated that biomass was decomposed mainly in the temperature range of 290–420 °C, whereas thermal degradation temperature of plastic mixture is 390–550 °C. The percentage weight loss difference (W) between experimental and theoretical ones was calculated, which reached a significantly high value of (−)15 to (−)50% at around 450 °C in various blend materials. These thermogravimetric results indicate the presence of significant interaction and synergistic effect between biomass and plastic mixtures during their co-pyrolysis at the high temperature region. With increase in the amount of plastic mixture in blend material, the char production has diminished at final pyrolysis temperature range. Additionally, a kinetic analysis was performed to fit with TGA data, the entire pyrolysis processes being considered as one or two consecutive first order reactions.     

Crosslinking and thermal stability of thermosets based on novolak and melamine

The crosslinking under pressure of a mixture of novolak with melamine resin has been investigated by means of several techniques, including differential scanning calorimetry, thermal gravimetric analysis, X‐ray diffraction, and infrared spectroscopy. The crosslinking of the mixture essentially follows two steps. The former occurs at 150°C and leads to resin networks composed of di‐ and trisubstituted phenols without significant reaction with melamine polymers. The latter, at 200°C, mainly involves the direct crosslinking of melamine polymers with disubstituted phenols. High pressure, applied to the reaction cell, slows down the crosslinking extent, by inhibiting the formation of trisubstituted phenols. This is probably due to the formation of gaseous by‐products of crosslinking. Moreover, a certain structuring effect due to high pressure was observed by means of X‐ray diffraction.© 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Synthesis and characterization of a new class of thermosetting resins: Allyl and propargyl substituted cyclopentadiene derivatives

A series of all-hydrocarbon resins were synthesized by reacting cyclopentadiene allyl chloride, propargyl chloride, or a mixture of allyl chloride and propargyl ide, under phase transfer conditions. Phase transfer reactions with and without added solvents, and with either quaternary ammonium or crown ether catalysts, yielded similar products consisting of a mixture of 1,1-disubstituted cyclopentadiene (minor amount) and 2-3 isomers each of tri-, tetra-, penta-, and hexa-substituted derivatives. No further reaction of each these components possible. The overall substitution pattern varied little with changes in reaction conditions although limiting the allyl chloride content led to still reactive, partially substituted products. Incorporation of all-propargyl and high propargyl-to-allyl mixed functionalities on cyclopentadiene yielded products whose stability was very hindering their thorough characterization. Preliminary evaluation was there-carried out for mixed resins with lower propargyl functionality. The allyl substituted resin (allylated cyclopentadiene, ACP) underwent thermal cure lout initiator at around 200°C while allyl/propargyl substituted resin (7:1 ratio, APCP) showed a faster, lower temperature cure at around 120°C. Cationic cure of ACP was also initiated by a novel sulfonium salt at around 100°C. Neat resin when cured at 200°C gave material with a flexural storage modulus 2 of about 300 MPa. Further cure at 250°C raised the modulus to 1.2 GPa. resin gave composites with excellent properties when used with glass and on fibers. Flexural modulus values (by DMA) of ∼ 66 GPa were obtained for ACP/carbon fiber composites compared with 42 GPa for epoxy/carbon composites made in our laboratories using commercially available materials. The modulus values at 300°C dropped to 10% of the room temperature value for the epoxy composites, while the ACP/carbon composite maintained 60% of its room temperature value at 300°C. When brought back to ambient temperature, the modulus of latter sample had increased to 80 GPa and that of the epoxy composite dropped to 23 GPa. Glass fiber ACP composites performed similar to an epoxy composite up to 200°C but maintained properties up to 300°C while those of the epoxy were drastically reduced. TGA analysis of both cured ACP resin and its composites showed decomposition beginning at 375°C. Three-point-bending tests indicated very high modulus with brittle failure for ACP composites. Scanning electron micrographs showed moderate bonding of the new resin to both carbon glass fiber surfaces. This new class of thermosetting resins offers excellent potential for application in low-cost glass and carbon composites with good thermal and physical properties.     

Formation and decomposition of stigmasterol hydroperoxides and secondary oxidation products during thermo‐oxidation

The oxidation mechanisms of stigmasterol at 100 and 180 °C were investigated by using the HPLC‐UV‐FL method. An overall picture of the oxidation status was achieved with a single HPLC analysis, enabling us to monitor the formation and decomposition of both primary and secondary oxidation products. The oxidation behavior of stigmasterol was different at the two temperatures. At 180 °C, the amounts of hydroperoxides increased sharply during the first 10 min and then began to decrease. At 100 °C, the amounts of hydroperoxides increased over the entire experimental period. At 180 °C, all major secondary oxidation products, except 7‐ketostigmasterol, reached a plateau after 40 min of oxidation, while at 100 °C their amounts increased constantly. The same oxidation products were formed at both temperatures, but their distribution differed. At 180 °C, the formation of free radicals at position 7 was more favorable than formation of radicals at position 25. The situation was the opposite at 100 °C; radicals formed more easily at the tertiary position 25. At 180 °C, 7‐ketostigmasterol was dominant after 40 min of oxidation, whereas at 100 °C it was the main oxidation product over the entire experiment.     

Steam Reforming of Bio‐Oil for Hydrogen Production: Effect of Ni‐Co Bimetallic Catalysts

Various Ni‐Co bimetallic catalysts were prepared by incorporating sol‐gel and wet impregnation methods. A laboratory‐scale fixed‐bed reactor was employed to investigate their effects on hydrogen production from steam reforming of bio‐oil. The catalyst causes the condensation reaction of bio‐oil, which generates coke and inhibits the formation of gas at temperatures of 250 °C and 350 °C. At 450 °C and above the transformation of bio‐oil is initiated and gaseous products are generated. The catalyst also can promote the generation of H₂ as well as the transformation of CO and CH₄ and plays an active role in steam reforming of bio‐oil or gaseous products from bio‐oil pyrolysis. The developed 3Ni9Co/Ce‐Zr‐O catalyst achieved maximum hydrogen yield and lowest coke formation rate and provided a better stability than a commercial Ni‐based catalyst.     

Synthesizing carbon nanotubes and carbon nanofibers over supported-nickel oxide catalysts via catalytic decomposition of methane

Supported-NiO catalysts were tested in the synthesis of carbon nanotubes and carbon nanofibers by catalytic decomposition of methane at 550 °C and 700 °C. Catalytic activity was characterized by the conversion levels of methane and the amount of carbons accumulated on the catalysts. Selectivity of carbon nanotubes and carbon nanofiber formation were determined using transmission electron microscopy (TEM). The catalytic performance of the supported-NiO catalysts and the types of filamentous carbons produced were discussed based on the X-ray diffraction (XRD) results and the TEM images of the used catalysts. The experimental results show that the catalytic performance of supported-NiO catalysts decreased in the order of NiO/SiO₂ > NiO/HZSM-5 > NiO/CeO₂ > NiO/Al₂O₃ at both reaction temperatures. The structures of the carbons formed by decomposition of methane were dependent on the types of catalyst supports used and the reaction temperatures conducted. It was found that Al₂O₃ was crucial to the dispersion of smaller NiO crystallites, which gave rise to the formation of multi-walled carbon nanotubes at the reaction temperature of 550 °C and a mixture of multi-walled carbon nanotubes and single-walled carbon nanotubes at 700 °C. Other than NiO/Al₂O₃ catalyst, all the tested supported-NiO catalysts formed carbon nanofibers at 550 °C and multi-walled carbon nanotubes at 700 °C except for NiO/HZSM-5 catalyst, which grew carbon nanofibers at both 550 °C and 700 °C.     

Noncatalytic Hydrolysis of Iminodiacetonitrile in Near‐Critical Water – A Green Process for the Manufacture of Iminodiacetic Acid

The hydrolysis of iminodiacetonitrile (IDAN) in near‐critical water, without added catalysts, has been successfully conducted with temperature and residence time ranges of 200–260 °C and 10–60 min, respectively. The effects of temperature, pressure, and initial reactant/water ratio on the reaction rate and yield have been investigated. The final reaction products primarily included iminodiacetic acid (IDA) and ammonia associated with other by‐products; gas formation was negligible. The maximum yield of IDA was 92.3 mol.‐% at 210 °C and 10 MPa, with a conversion of almost 100 %.The apparent activation energy and ln A of IDAN hydrolysis were evaluated as 45.77 ± 5.26 kJ/mol and 8.6 ± 0.1 min^–1, respectively, based on the assumption of first‐order reaction. The reaction mechanism and scheme were similar to those of base‐catalyzed reactions of nitriles examined in less severe conditions.     

Bismuth‐Doped Ceria,Ce0.90Bi0.10O2: A Selective and Stable Catalyst for Clean Hydrogen Combustion

Bismuth‐doped cerias are successfully applied as solid “oxygen reservoirs” in the oxidative dehydrogenation of propane. The lattice oxygen of the ceria is used to selectively combust hydrogen from the dehydrogenation mixture at 550 °C. This process has three key advantages: it shifts the dehydrogenation equilibrium to the desired products side, generates heat, aiding the endothermic dehydrogenation, and simplifies product separation (water vs. hydrogen). Furthermore, the process is safer, since it uses the catalyst’s lattice oxygen instead of gaseous oxygen. We show here that bismuth‐doped cerias are highly active and stable towards hydrogen combustion, and explore four different approaches for optimising their application in the oxidative dehydrogenation of propane: first, the addition of extra hydrogen which lowers hydrocarbon conversion by suppressing both combustion and coking; second, the addition of tin which completely inhibits coking; third, the addition of platinum which increases selectivity, but at the expense of lower activity. The best results are obtained through tuning the reaction temperature. At 400 °C, high activity and selectivity were obtained for the bismuth‐doped ceria Ce_0.90Bi_0.10O₂. Here, 90% of the hydrogen feed is converted at 98% selectivity. This optimal reaction temperature can be rationalised from the hydrogen and propene temperature‐programmed reduction (TPR) profiles: 400 °C lies above the reduction maximum of hydrogen, yet below that of propene. That is, this temperature is sufficiently high to facilitate rapid hydrogen combustion, but low enough to prevent hydrocarbon conversion.     

Low-temperature oxidation of brown coal. 3. Reaction with molecular oxygen at temperatures close to ambient

Yallourn brown coal was oxidized with pure molecular oxygen at temperatures of 35 and 70 °C until, after about 45 days, no further gain in mass occurred. At this stage, despite the loss of considerable quantities of carbon and hydrogen from the coal as carbon dioxide, carbon monoxide and water, the coal had gained in mass by 15 g per kg of dry coal. Virtually all the gain was accounted for by increases in the content of carboxyl, carbonyl and phenolic groups. These functional groups, which subsequently break down to yield the stable products already mentioned, are formed apparently by attack on the aliphatic structures of the coal. At 35 °C, reactions leading to the formation of functional groups such as phenolic groups, and their breakdown to water, predominated; however, at 70 °C, the formation of carboxyl groups and their breakdown to carbon dioxide became more important, the amount of water formed being less than that at 35 °C. The general course of these reactions was qualitatively similar to that observed by other workers using bituminous coals, but the extent of the reactions was an order of magnitude greater.