Synthesis of rigid polyurethane foams from oligoester alcohols obtained from dimethyl terephthalate production wastes

A study was conducted to synthesize oligoester alcohols from dimethyl terephthalate production wastes via transesterification with diethylene glycol and trimethylol propane. The oligoester alcohols obtained are suitable for preparing rigid polyurethane foams. The oligoester alcohols from trimethylol propane possess good physical and mechanical properties. The oxygen indices indicate that the polyurethane foams exhibit improved resistance to combustion due to the increased content of aromatic nuclei in the oligoester alcohols.     

Preparation and application of glycolysed polyurethane integral skin foams recyclate from automotive wastes

Summary Glycolysis of isocyanate derived foams with glycol and amine mixture is a simple and economically attractive chemical recycling process. A mixture of diethylene glycol (DEG) and diethanol amine (DEA) is used as solvent system and sodium hydroxide as the catalyst. The obtained polyols can be completely reused in the formulation of integral skin foams in blend with virgin polyol.     

Solvent-blown,rigid urethane foams from low cost castor oil-polyol mixtures

The preparation of solvent-blown rigid urethane foams from low cost castor oil-polyol mixtures was investigated. Solutions of triisopropanolamine, and of mixtures of triisopropanolamine and triethanolamine in castor oil, were used as the polyol component of these foams. Foams were prepared by reacting these polyol mixtures, in the presence of catalyst, surfactant, and trichlorofluoromethane, with prepolymers prepared from toluenediisocyanate and certain polyether polyols or mixtures of these polyether polyols with castor oil. The effect of polyol and prepolymer composition and blowing agent concentration on such foam properties as density and compressive strength was investigated. The properties of the castor oil-based foams were comparable to those of foams obtained from more costly polyols. Presented at the Spring Meeting of the American Oil Chemists' Society, St. Louis, Missouri, May 1–3, 1961. A laboratory of the Western Utilization Researchand Development Division, Agricultural Research Service, U. S. Department of Agriculture.     

Formation mechanism of carbon foams derived from mesophase pitch

Carbon foams were prepared from mesophase pitch using foaming, carbonization and graphitization processes. The physical and chemical properties of the mesophase pitch during thermal treatment were studied by Fourier transform infrared spectroscopy, thermogravimetry, mass spectroscopy, rheometry and scanning electron microscopy. The results suggest that gases released from the pitch dissolve, saturate, nucleate and grow in the molten pitch during foaming. Then the resultant bubbles coalesced with the neighboring bubbles driven by the surface tension of the molten pitch. This coalescence generates a shear stress to force aromatic planes of the pitch to arrange regularly and paralleled to the axis of a ligament. The growth of bubbles stopped when the pitch became semi-coke at a temperature above 733 K. The viscosity and surface tension of the molten pitch are major factors that influence the growth of bubbles. After carbonization at 1073 K and graphitization at 2873 K, the well aligned aromatic planes in the foams evolve into highly aligned graphitic structures.     

Methane production from citrus wastes: process development and cost estimation

BACKGROUND: Because of its extreme toxicity for microorganisms, the limonene content of citrus wastes (CWs) has been a major obstacle to the conversion of CWs to biofuels. The main objective of this study was to develop a new process for the utilization of CWs that can be economically feasible when the supply of CW is low. RESULTS: Steam explosion pre‐treatment was applied to improve the anaerobic digestibility of CWs, resulting in a decrease of initial limonene concentration by 94.3%. A methane potential of 0.537 ± 0.001 m³ kg^?1 VS (volatile solids) was obtained during the following batch digestion of treated CWs, corresponding to an increase of 426% compared with that of the untreated samples. Long‐term effects of the treatment were further investigated by a semi‐continuous co‐digestion process. A methane production of 0.555 ± 0.0159 m³ CH₄ kg^?1 VS day^?1 was achieved when treated CWs (corresponding to 30% of the VS load) were co‐digested with municipal solid waste. CONCLUSION: The process developed can easily be applied to an existing biogas plant. The equipment cost for this process is estimated to be one million USD when utilizing 10 000 tons CWs year^?1. 8.4 L limonene and 107.4 m³ methane can be produced per ton of fresh citrus wastes in this manner. Copyright © 2011 Society of Chemical Industry     

Sorptional properties of carbon nanotubes produced from corn wastes

The sorption capacity of multiwalled nanotubes synthesized in the mechanical activation of amorphous carbon from corn wastes is investigated. The sorptional effectiveness of the nanotubes depends on their storage time. The use of carbon from corn waste as chelators is considered.     

Activated carbon from solid wastes using a pilot-scale batch flaming pyrolyser

Activated carbon has been prepared from solid wastes carbonised in a pilot-scale batch flaming pyrolyser. Wood furniture waste (chipboard and plywood), scrap tyres, urban sewage, and straw were selected as pollutant solid wastes for this study. Burn-off levels, porosity, and BET surface were determined. From furniture waste derived char, a highly microporous solid was obtained at 850°C with a BET surface area of 855 m²/g. A medium surface area (431 m²/g) activated solid was obtained from tyre derived char at 1000°C. An FT-IR spectroscopic study of activated tyre and furniture derived chars showed different chemical structures and a higher water adsorption capacity for furniture derived solids than for those derived from tyres. The low cost flaming pyrolyser can produce, at pilot scale, chars suitable for activation from furniture wastes and tyres.     

Preparation and characterization of carbon foams derived from aluminosilicate and phenolic resin

Aluminosilicate-reinforced carbon foams have been prepared by chemical foaming with phenolic resin as matrix precursor and aluminosilicate as the additive. The effects of the amount of aluminosilicate used on the microstructure, mechanical properties and oxidation resistance of the carbon foams have been investigated by scanning electronic microscopy, mechanical testing, and oxidation weight loss, respectively. The results show that the amount of aluminosilicate added has a significant influence on the surface roughness and the structure uniformity of carbon foams. The compressive strengths are usually higher than that of the pure carbon foam sample by as much as 60%. The percentage of weight loss of the carbon foams drops with increasing aluminosilicate content up to 11 wt%, but then increases.     

Carbon foams prepared from coal tar pitch for building thermal insulation material with low cost

A new approach is provided to resolve the large-scale applications of coal tar pitch. Carbon foams with uniform pore size are prepared at the foaming pressure of normal pressure using coal tar pitch as raw materials. The physical and chemical performance of high softening point pitch(HSPP) can be regulated by vacuumizing owing to the cooperation of vacuumizing and polycondensation. Results indicate that the optimum softening point and weight ratio of quinoline insoluble are about 292℃ and 65.7%, respectively. And the optimum viscosity of HSPP during the foaming process is distributed in the range of 1000-10000 Pa·s. The resultant carbon foam exhibits excellent performance, such as uniform pore structure, high compressive strength(4.7 MPa), low thermal conductivity(0.07 W·m~(-1) ·K~(-1)), specially, it cannot be fired under the high temperature of 1200 ℃.Thus, this kind of carbon foam is a potential candidate for thermal insulation material applied in energy saving building.     

Removal of cupric ions from acidic sulfate solution using reticulated vitreous carbon rotating cylinder electrodes

The potentiostatic deposition of copper from acid sulfate solutions (0.50 mol dm^?3 Na₂SO₄ at pH 2 and 298 K) was studied at four porosity grades (10, 30, 60 and 100 pores per linear inch, ppi) of reticulated vitreous carbon (RVC) rotating cylinder electrode (RCE). The rate of removal of cupric ions from a 200 cm³ volume of electrolyte was examined as a function of the grade of RVC foam, the electrode potential and the initial cupric ion concentration. For the 100 ppi material, the product of the mass transport coefficient and the electroactive area per unit volume of electrode (k_mA_e) was equal to 0.28 s^?1 at a potential of ?500 mV vs SCE for an initial cupric ion concentration of 0.85 mmol dm^?3 and a constant rotation speed of 1500 rev min^?1. Under the experimental conditions, an initial dissolved copper concentration of 63.5 ppm could be reduced to <0.1 ppm in approximately 60 min using a 100 ppi RVC RCE. SEM studies showed some non‐uniform deposition of metal due to heterogeneous nucleation of copper together with the development of rough deposits. Copyright © 2004 Society of Chemical Industry     

Extraction of caffeine from tea stalk and fiber wastes using supercritical carbon dioxide

The purpose of this study was to investigate obtaining of caffeine from tea plant wastes by supercritical carbon dioxide extraction. Experiments were carried out with tea stalk and fiber wastes of Turkish tea plants that has no economical value. Stalk and fiber wastes were supplied from tea factories. These wastes were ground, sieved and dried at 105 °C temperature in an oven. Parameters affecting caffeine leaching from tea wastes were determined to be, extraction time, extraction temperature, carbon dioxide flow rate, process pressure and particle size. The maximum yield of caffeine from tea stalk wastes and fiber wastes were 14.9 mg/g tea stalk and 19.2 mg/g tea fiber, respectively. The yield increase had been recorded as 61.9% and 65.5%, respectively, in comparison with the chloroform extraction of tea stalk and fiber wastes.     

Removal of formaldehyde from aqueous solutions via oxygen reduction using a reticulated vitreous carbon cathode cell

The removal of formaldehyde from waste streams to <0.3 ppm has been demonstrated using a cell with a reticulated vitreous carbon cathode; the formaldehyde is oxidized by hydrogen peroxide, formed at the cathode by reduction of oxygen. In most electrolytes studied (e.g. NaOH, NaCl and Na₂SO₄), the formaldehyde is oxidised only to formic acid. On the other hand, the addition of a low concentration of an iron salt (i.e. 0.5 mm), catalyses the complete oxidation to carbon dioxide. The removal of formaldehyde can be achieved in media of low ionic strength (< 10 mm) although the use of iron salts necessitates the adjustment of pH to 3 to maintain the catalyst in solution.     

Extraction of caffeine from tea stalk and fiber wastes using supercritical carbon dioxide

The purpose of this study was to investigate obtaining of caffeine from tea plant wastes by supercritical carbon dioxide extraction. Experiments were carried out with tea stalk and fiber wastes of Turkish tea plants that has no economical value. Stalk and fiber wastes were supplied from tea factories. These wastes were ground, sieved and dried at 105 °C temperature in an oven. Parameters affecting caffeine leaching from tea wastes were determined to be, extraction time, extraction temperature, carbon dioxide flow rate, process pressure and particle size. The maximum yield of caffeine from tea stalk wastes and fiber wastes were 14.9 mg/g tea stalk and 19.2 mg/g tea fiber, respectively. The yield increase had been recorded as 61.9% and 65.5%, respectively, in comparison with the chloroform extraction of tea stalk and fiber wastes.     

Electrodeposition of mesoscopic Pt-Ru on reticulated vitreous carbon from reverse emulsions and microemulsions: Application to methanol electro-oxidation

High surface area Pt-Ru (between 120 and 400 cm² mg⁻¹) meso-sized particles and mesoporous coatings were electrodeposited on reticulated vitreous carbon (RVC) three-dimensional electrodes using reverse emulsions and microemulsions. The organic phase of the colloidal media was composed of cyclohexane, Triton X-100 non-ionic surfactant and tetrabutylammonium perchlorate (for ionic conductivity) while the aqueous phase contained H₂PtCl₆ and RuCl₃ (or (NH₄)₂RuCl₆). For microemulsification to occur isopropanol was also added as co-surfactant. The catalytic activity for the electro-oxidation of methanol was assessed by cyclic voltammetry and chronopotentiometry in conjunction with surface area measurement by Cu underpotential deposition. The composition and morphology of the Pt-Ru deposit was analyzed by inductively coupled plasma atomic emission spectroscopy and scanning electron microscopy, respectively. The effects on the catalytic activity of the deposition current density, temperature, RVC pretreatment and plating bath composition are presented. It was found that the electrodeposition of Pt-Ru in reverse microemulsion yielded the highest specific surface area (400 cm² mg⁻¹) and catalytic activity toward CH₃OH electro-oxidation as shown, for example, by a 50-200 mV more negative anode potential determined by chronopotentiometry compared to a catalyst obtained by pure aqueous and emulsion electroplating.     

Recent advances in low‐cost carbon fiber manufacture from lignin

The confluence of two US energy policy mandates, the 2012 Corporate Average Fuel Economy Standards and Renewable Fuels Standard #2, provide the opportunity to examine the possibility of high‐value materials from lignin with increased depth. In this case, the desire to provide lighter, low‐cost materials for automobiles to reduce fuel consumption, and to improve the economics of biorefineries for fuel production, have led to an increased interest in low‐cost carbon fiber manufacture from lignin. For this review the authors provide the context of subject matter importance, a cost comparison of potential low‐cost carbon fibers, a brief review of historical work, a review of more recent work, and a limited technical discussion followed by recommendations for future directions. As the available material for review is limited, the author includes many references to publicly available government documents and reviewed proceedings that are generally difficult to locate. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 713‐728, 2013     

The application of reticulated vitreous carbon rotating cylinder electrodes to the removal of cadmium and copper ions from solution

The removal of cadmium and cupric ions from 0.50 mol dm^?3 Na₂SO₄ at pH 2 and 298 K was studied using a reticulated vitreous carbon (RVC) rotating cylinder electrode (RCE). The cathode was a 100 pores per linear inch porosity grade with a radius of 0.5 cm, a height of 1.2 cm and a volume of 0.94 cm 3 . The cathode was rotated a constant speed of 1500 rev min^?1. A rate enhancement of approximately three times is reported for the removal of cupric ions from a chloride solution (0.05 mol dm^?3 cupric ions in 0.1 mol dm^?3 NaCl at pH 7) when compared with the analogous reaction in acid sulfate solutions (0.50 mol dm^?3 Na₂SO₄ at pH 2). SEM images of the metal deposit morphology allow the morphology of the metal deposits to be characterised. The deposits showed incomplete coverage of the RVC surface and appreciable roughness developed with time due to dendritic growths. Copyright © 2004 Society of Chemical Industry     

Recovery of carbon fibres and production of high quality fuel gas from the chemical recycling of carbon fibre reinforced plastic wastes

A solvolysis process to depolymerize the resin fraction of carbon fibre reinforced plastic waste to recover carbon fibre, followed by hydrothermal gasification of the liquid residual product to produce fuel gas was investigated using batch reactors. The depolymerisation reactions were carried out in ethylene glycol and ethylene glycol/water mixtures at near-critical conditions of the two solvents. With ethylene glycol alone the highest resin removal of 92.1% was achieved at 400 °C. The addition of water to ethylene glycol led to higher resin removals compared to ethylene glycol alone. With an ethylene glycol/water ratio of 5, at 400 °C, resin removal was 97.6%, whereas it was 95.2% when this ratio was 3, at the same temperature. The mechanical properties of the recovered carbon fibre were tested and showed minimal difference in strength compared to the virgin carbon fibre. The product liquid, containing organic resin degradation products was then subjected to catalytic supercritical water gasification at 500 °C and 24 MPa in the presence of NaOH and Ru/Al₂O₃ as catalysts, respectively. Up to 60 mol.% of H₂ gas was produced with NaOH as catalyst, and 53.7 mol.% CH₄ gas was produced in the presence of Ru/Al₂O₃.     

Heteroadagulation of microdrops of compressor oil and the cleaning of water from them on carbon fabric

The process of the microdrop coarsening of KhA-30 compressor oil on carbon fabric is studied. The problem is connected with the necessity of the cleaning of air and water from the microdrops of oils cooling the compressors. The heteroadagulation method allowed for the separation of water from compressor oil particles with a diameter 0.8–7.6 μm over the course of a few minutes. The oiling of the carbon fabric is reduced to a minimum. For the first time, by an order of magnitude, finer discontinuities, which can behave as stable cluster origination centers, are observed on the surface of micron-sized oil drops.     

Effect of ethanol content on supercritical carbon dioxide extraction of caffeine from tea stalk and fiber wastes

This study presents the effect of ethanol content on supercritical carbon dioxide extraction of caffeine from tea plant wastes. Tea stalk and fiber wastes of Turkish tea plants that have no economical value were evaluated as raw material throughout the caffeine extraction experiments. These wastes were supplied from tea factory marked “Çaykur” in the east blacksea region. They were separately ground, sieved and dried at 105 °C temperature in an oven. Parameters affecting caffeine leaching from tea wastes were determined to be, ethanol flow rate, extraction time, extraction temperature, carbon dioxide flow rate, process pressure and particle size. The maximum yield of caffeine from tea stalk wastes and fiber wastes were 14.95 mg/g tea stalk and 18.92 mg/g tea fiber, respectively. When the supercritical extraction conditions used of ethanol as cosolvent have been compared with the conditions of used only carbon dioxide, approximately the same yield has been reached at 2 h extraction period instead of 7 h. Beside of saving of the time and the amount of carbon dioxide, the supercritical extraction yield with cosolvent increase had been recorded as 62.5% and 63.1%, respectively, in comparison with the chloroform extraction as conventional method of tea stalk and fiber wastes.