Showing papers on "Hexane published in 2006"

Extraction, Characterization and Modification of Castor Seed Oil

Abstract: This paper carried out experimental study, through extraction and characterization of both crude and refined castor oil. Normal hexane was used as solvent for the extraction process. The oil produced was refined through degumming, neutralization and bleaching process using local adsorbent (activated clay). The characterization analysis revealed that tested parameters, which include specific gravity, refractive index, acid value, saponification value and iodine value for both crude and refined castor oil produced, were within the ASTM standard specifications. In fact the iodine value obtained (84.8) for the refined oil indicates that the oil could certainly be used as lubricant, hydraulic break fluid and protecting coatings. The oil was modified via sulphation method to produce Turkey – red oil that was tested on wooden material, paper and cloth. The test revealed that the Turkey – red oil produced is suitable to be used as a good dying agent and polish.

Catalytic purification of waste gases containing VOC mixtures with Ce/Zr solid solutions

Abstract: This study has been undertaken to investigate the efficiency of ceria, zirconia, and Ce x Zr 1− x O 2 mixed oxides as catalysts for the vapour-phase destruction in air of single model VOCs ( n -hexane, 1,2-dichloroethane and trichloroethylene) and non-chlorinated VOC/chlorinated VOC binary mixtures. Considering all catalyst compositions examined for the individual destruction of these compounds, activity for complete oxidation decreased in the following order: n -hexane 0.5 Zr 0.5 O 2 and Ce 0.15 Zr 0.85 O 2 ) were different than that with the best performance for n -hexane oxidation (CeO 2 ). Concerning chlorinated VOCs conversion, it was observed that notable improvements in catalyst activity of CeO 2 could be achieved through structural doping with Zr ions. Mixed oxides exhibited promoted redox and acid properties, which resulted catalytically relevant for the oxidation of 1,2-dichloroethane and trichloroethylene. In contrast, the combustion of n -hexane was essentially controlled by surface oxygen species, which were more abundant on CeO 2 . Attainment of high n -hexane conversions with CeO 2 was also attributed in part to the hydrophobicity of the support and the reduced interaction with carbon dioxide. Significant ‘mixture effects’ on both activity and selectivity were noticed when a given chlorinated feed was decomposed in the presence of n -hexane. On one hand, each VOC decreased the reactivity of the other relative to that of the pure compound resulting in higher operating temperatures to achieve adequate destruction. Competitive adsorption played an important role in the reciprocal inhibition effects detected with all catalysts. On the other hand, the selectivity to HCl was noticeably enhanced when n -hexane was co-fed, probably due to the increased presence of water generated as an oxidation product.

Gaseous hexane biodegradation by Fusarium solani in two liquid phase packed-bed and stirred-tank bioreactors

Abstract: Biofiltration of hydrophobic volatile pollutants is intrinsically limited by poor transfer of the pollutants from the gaseous to the liquid biotic phase, where biodegradation occurs. This study was conducted to evaluate the potential of silicone oil for enhancing the transport and subsequent biodegradation of hexane by the fungus Fusarium solani in various bioreactor configurations. Silicone oil was first selected among various solvents for its biocompatibility, nonbiodegradability, and good partitioning properties toward hexane. In batch tests, the use of silicone oil improved hexane specific biodegradation by approximately 60%. Subsequent biodegradation experiments were conducted in stirred-tank (1.5 L) and packed-bed (2.5 L) bioreactors fed with a constant gaseous hexane load of 180 g center dot m(reactor)(-3)center dot h(-1) and operated for 12 and 40 days, respectively. In the stirred reactors, the maximum hexane elimination capacity (EC) increased from 50 g center dot m(reactor)(-3)center dot h(-1) (removal efficiency, RE of 28%) in the control not supplied with silicone oil to 120 g center dot m(reactor)(-3)center dot h(-1) in the biphasic system (67% RE). In the packed-bed bioreactors, the maximum EC ranged from 110 (50% RE) to 180 g center dot m(reactor)(-3)center dot h(-1) (>90% RE) in the control and two-liquid-phase systems, respectively. These results represent, to the best of our knowledge, the first reported case of fungi use in a two-liquid-phase bioreactor and the highest hexane removal capacities so far reported in biofilters.

Absorption and adsorption of hydrophobic organic contaminants to diesel and hexane soot.

Abstract: Soot particles vary in pore structure, surface properties, and content of authigenic (native) extractable organic chemicals. To better understand the effects of these properties on sorption, aqueous sorption isotherms for 14C-labeled phenanthrene and 1,2,4-trichlorobenzene were obtained for four soots of varying properties: two diesel reference soots, a hexane soot, and an ozonated hexane soot. Substantial isotherm nonlinearity was observed. In comparison to diesel soot SRM 2975, diesel soot SRM 1650b had a much higher content of extractable authigenic organic chemicals, showed less sorption of 14C-labeled sorbate at low relative concentrations (Ce/Sw), and showed higher sorption at high Ce/Sw. In comparison to normal hexane soot, the ozonated hexane soot had a higher surface O/C ratio and showed substantially less sorption at all concentrations studied. The sorption differences were attributed to the noted differences in properties, and results were interpreted through a dual-mode sorption model that in...

Separation by Fixed-Bed Adsorption of Hexane Isomers in Zeolite BETA Pellets

Abstract: An experimental study of single and binary fixed-bed adsorptions of hexane isomers n-hexane (nHEX), 3-methylpentane (3MP), 2,3-dimethylbutane (23DMB) and 2,2-dimethylbutane (22DMB) was performed in

Measurement and Correlation of CO2 Solubility in the Systems of CO2 + Toluene, CO2 + Benzene, and CO2 + n-Hexane at Near-Critical and Supercritical Conditions

Abstract: The solubility of CO2 in the systems of CO2 + benzene, CO2 + n-hexane, and CO2 + toluene was meticulously measured at (293.15, 298.15, and 308.15) K and different pressures using a pressure−volume−...

A novel multisensing optical approach based on a single phthalocyanine thin films to monitoring volatile organic compounds

Abstract: This paper reports the use of optical trasduction techniques to characterise solid state chemo-optical sensors prepared by Langmuir–Schafer technique (LS) in thin film form based onto Cu(II) tris-(2,4-di- t -amylphenoxy)-(12-hydroxy-1,4,7,10-tetraoxadodecyl)-phthalocyanine macromolecules CuPcOH as active layers. The study consists in the UV–vis optical absorption monitoring of the active LS layers in the presence of specific five volatile organic compounds (VOCs) mixed in dry air in controlled atmosphere; in particular tert -butylamine, methanol, ethanol, hexane and ethyl acetate, all analytes of interests in the food quality control. The UV–vis spectra have been monitored by recording the dynamic variation in the integral of the absorbance curves in well defined spectral regions: 300–400 nm, 550–600 nm, 600–640 nm, 640–700 nm, covering the whole spectrum and centred around the typical absorption bands of phthalocyanine thin films. This simultaneous UV–vis four channel monitoring allowed to use only one active layer as sensing element where each selected spectral region generates independent sensors. The dependency of the above mentioned outputs towards the analytes has been discussed. A base optical characterisation of the investigated LS thin films has been performed.

Isomerisation of n-hexane over sulphated zirconia modified by noble metals

Abstract: Isomerisation of n -hexane has been studied at industrially relevant conditions over sulphated zirconia promoted with Pt, Rh, Ir, and Ru. The Pt-promoted sample showed the highest activity, and it was considerably more active than a commercial, zeolite-based catalyst. The samples promoted with rhodium and iridium showed a lower, and similar activity, while ruthenium was less efficient and gave a less stable catalyst. The selectivities were similar for all the samples, with the methylpentanes and 2,3-dimethylbutane as main and primary products. Measured kinetic parameters for the reaction were in agreement with a conventional bifunctional mechanism: Positive order in n -hexane, negative in hydrogen and an activation energy around 90 kJ/mol. Prereduction of the samples was necessary to achieve a high activity, but if the activation temperature was too high the activity was lost, probably due to the loss of sulphate groups through excessive reduction.

Oil Water Separation

Abstract: Oil and grease (O&G) is a common pollutant frequently found in the effluent of a wide range of industries. Oil and grease concentrations in wastewater, as recommended by the US Environmental Protection Agency, are not determine as the presence of specific compounds but are measured by their extractability using a particular solvent. Hexane and Freon are primary solvents used to extract oily compounds from wastewaters. Therefore, the term “oil and grease” contains a wide range of contaminants, which may include but are not limited to fatty acids, surfactants, petroleum hydrocarbons, phenolic compounds, animal and vegetable oils, etc. Many industries such as steel, aluminum, food, textile, leather, petrochemical, and metal finishing were reported as sources of high concentrations of oil and grease in their wastewaters as shown in Table 1.

Oxyfunctionalization of n-pentane and n-hexane by oxovanadium complexes supported on carbamated modified silica gel

Abstract: The bis(maltolato)oxovanadium complexes cis -[VO(OCH 3 )(ma) 2 ] 1 , cis -[VO(OC 2 H 5 )(ma) 2 ] 2 , [VO(ma) 2 ] 3 and [VO(py)(ma) 2 ] 4 have been anchored to chemically modified silica gel and are shown to act as supported catalysts for the oxidation of n -pentane and n -hexane, with molecular oxygen under relatively mild reaction conditions, to the corresponding ketones (with good selectivities) and alcohols (in smaller amounts). cis -[VO(OCH 3 )(ma) 2 ] 1 provides the best results in both cases and the effects of various factors (temperature, time, O 2 pressure, catalyst amount) were also investigated towards the optimization of the reaction conditions. 2-pentanone (84% selectivity) and a small amount of 2-pentanol are formed from n -pentane at 150 °C, p (O 2 ) = 15 atm, while 2-hexanone (58% selectivity), 1-hexanol and acetic acid are obtained from n -hexane at 160 °C, p (O 2 ) = 10 atm. The involvement of a carbon- and oxygen-centred radical mechanism is suggested by experiments with free radical traps. Heteroaromatic acids were tested as possible co-catalysts and 2-pyrazinecarboxylic acid was the most effective one. Thermogravimetric analysis (TGA) indicates the catalyst is stable up to ca. 220 °C and inductive couple plasma (ICP) shows a notable extensive vanadium loss from the supported catalyst after the reaction, allowing further use of the catalyst even without reactivation.

Thermodynamics of Mixtures Containing a Strongly Polar Compound. 8. Liquid−Liquid Equilibria for N,N-Dialkylamide + Selected N-Alkanes

Abstract: The coexistence curves of the liquid−liquid equilibria (LLE) for systems of dimethylformamide (DMF) with hexane, heptane, octane, or nonane and of dimethylacetamide (DMA) with heptane have been determined visually. All the curves show an upper critical solution temperature (UCST) and have a rather horizontal top. The measured LLE curves for DMF mixtures show that their symmetry depends on the size of the alkane. For a given alkane, the UCST is higher for systems with DMF. This reveals that dipole−dipole interactions between amide molecules are stronger in such solutions. The DISQUAC model represents fairly well the LLE curves.

Measurement and Correlation of Solubilities of Luteolin in Organic Solvents at Different Temperatures

Abstract: The solubilities of luteolin in methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, acetone, hexane, and dimethyl sulfoxide (DMSO) at T = (273.15, 283.15, 298.15, 313.15, and 333.15) K were measured. The solubility of luteolin increases with increasing temperature, but there was no correlation with the number of carbon in the solvents. The nonideal solution model and an empirical equation were used to correlate the solid−liquid equilibrium data.

Crystallization of β-sitosterol using a water-immiscible solvent hexane

Abstract: Cooling crystallization of β-sitosterol that is a kind of phytosterol was carried out, where a water-immiscible solvent hexane containing a ppm level of water was used as a solvent. The initial ratio of water and β-sitosterol concentration adopted in this work was 330/10, 1315/10 and 645/20 ppm/(g/L), which corresponded to 0.51, 2.0, and 0.50 in water/β-sitosterol mole ratio, respectively. When the initial ratio of water and β-sitosterol concentration was 1315/10 ppm/(g/L), thin plate-like crystals were precipitated and were identified as the monohydrate crystals of β-sitosterol. On the other hand, when the initial ratio of water and β-sitosterol concentration was 645/20 ppm/(g/L), needle-like crystals of hemihydrate were precipitated. This result meant that the ppm level of water plays an important role for the pseudo-polymorphism. Since the crystal structure of β-sitosterol hemihydrate had never been reported, we determined it by a single crystal XRD analysis.

Fluorescence responses of 1-methyl-1,2,3,4,5-pentaphenylsilole thin layer to vapors of common solvents

Abstract: The fluorescence responses of 1-methyl-1,2,3,4,5-pentaphenylsilole (MPS) thin layers on thin-layer chromatography silica plates in the sealed atmospheres of toxic, inflammable, and explosive solvents at room temperature were investigated. The MPS thin layer showed large fluorescence responses to approximately saturated vapors of solvents such as dichloromethane, chloroform, tetrahydrofuran, diethyl ether, benzene, n -hexane, acetone, toluene, and ethyl acetate with fluorescence quenching close to 100% within 180 s. Vapors of methanol and ethanol quenched the MPS fluorescence less than 40% within 180 s and n -butanol and DMF caused very limited response with fluorescence quenching less than 10% within 180 s. The solvent vapor molecules activated the rotational relaxations of the peripheries of MPS, causing the fluorescence quenching. The quenching ability or speed of a solvent was mainly determined by its affinity for the periphery rotations and its vapor pressure. Higher affinity for the periphery rotations or higher vapor pressure would enhance the quenching. The different fluorescence responses showed the possibility to differentiate different solvents.

Hexane isomerization and cracking activity and intrinsic acidity of H-zeolites and sulfated zirconia-titania

Abstract: Adsorption of N2 was studied on zeolite H-Y, ultrastabilized H-Y (H-USY), H-mordenite, H-ZSM-5, H-beta, and on sulfated zirconia-titania (SZT) mixed oxide by diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) at 298 K and at N2 pressures up to 9 bar. The adsorption-induced DeltanuOH red-shift of the nuOH bands was used as a measure of the intrinsic acid strength of the Brnonsted acid sites. The intrinsic acid strength of the solids follows the order of H-ZSM-5 approximately H-mordenite approximately H-beta > H-USY > SZT approximately H-Y. The solids were characterized by their hexane conversion activities at 553 K and 6.1 kPa hexane partial pressure. The reaction was shown to proceed predominantly by a bimolecular mechanism, while the reaction was first order in hexane and zero order in alkenes. The site-specific apparent rate constant of the bimolecular hexane conversion was shown to parallel the intrinsic acid strength of the samples, suggesting that the ratio of the apparent and the intrinsic activity, that is, the KA' equilibrium constant of alkane adsorption on the hydrocarbon-covered sorption sites, is hardly dependent on the catalyst structure.