Showing papers on "Hexane published in 2012"

Valorization of Coffee Grounds for Biodiesel Production

Abstract: This work evaluates the use of spent coffee grounds (SCG) for biodiesel production. The SCG were characterized for their moisture content (12.1 wt%), total carbon (TC) and total nitrogen (TN) (52.2 and 2.1 wt% respectively), cellulose and total lignin contents (33.6 wt% and 13.8 wt% respectively), carbon/nitrogen mass ratio (C/N = 24.8) and higher heating value (HHV, of 19.3 MJ/kg). For extracting the oil from the SCG, several solvents were tested at different contact times: hexane, ethanol, isopropanol, heptane and a mixture of hexane/isopropanol in the proportions of 50:50; 60:40; 70:30 and 80:20 (vol/vol). Results revealed an oil content ranging from 6.3 to 28.3 wt%, depending on the extraction conditions. For example, using hexane/isopropanol (50:50, vol/vol) a 21.5 wt% of oil recovery was obtained after 3 h of contact time, while using isopropanol a 21.0 wt% of oil recovery was obtained in 6.8 h, but at higher operating cost, considering the energy and solvent consumption. Regarding the oil characterization the following parameters can be highlighted: HHV of 36.4 MJ/kg, iodine value of 54.4 (g I2)/(100 g oil), water content of 2004 ppm and acid value of 118.4 (mg KOH)/(g oil). Finally, the possibility of using the recovered coffee oil for biodiesel production was evaluated. In this regard it was performed the oil esterification in three consecutive steps (using 1% of H2SO4 and 40 % of methanol for 2 h of reaction time at 60 oC and 500 rpm) followed by one transesterification step (1 % of NaOH and 40 % of methanol during a 2 h reaction time at 60 oC and 500 rpm). The resulting biodiesel was characterized for its acid value, density, viscosity at 40 oC, iodine value and esters content (65.7 to 72.9 %), of which only the iodine value of 26 and 58.4 (g I2)/(100 g biodiesel) was within the NP EN14214:2009 standard limits. The reaction yield varied between 58.8 and 62.2 wt%. Results suggest the need for a further process optimization in order to obtain a biodiesel complying with this standard quality requirements.

Effect of the extraction solvent polarity on the sesame seeds oil composition

Abstract: This study highlights the effect of solvent polarity on the yield (Y%) and properties of oil extracted from Algerian sesame seeds. Extractions were carried out under Soxhlet conditions with the following solvents: hexane (Hx), ethanol (Eth), acetone (Ac), dichloromethane (Di), isopropanol (Iso), hexane:isopropanol (Hx:Iso), and chloroform:methanol (Chf:Me). The sesame oil yield obtained using different solvents ranged from 28.86 to 52.83%. Fatty acids and sterols analyses were performed by GC on capillary column. γ-Tocopherol was the major tocochromanol compound detected by HPLC-fluorescence. Fourteen fatty acids were identified, with the predominance of oleic and linoleic acids. The main sterol in sesame oil was β-sitosterol, followed by stigmasterol, campesterol, and Δ5-avenasterol which were present in lower concentrations. High correlations were found between arachidic, gadoleic, behenic, and lignoceric acids concentrations; these results were explained by the metabolic biosynthesis pathway of the biologically active long-chain PUFA by successive elongation and desaturation. Principal component analysis (PCA) of the data obtained from sesame oil composition enabled an easy comparison of the different extraction solvents, and correlated their properties with the most characteristic components of the extracted oils with a view to understand solvent–oil interaction, and to establish the effects of extracting solvent on such oil composition. Practical applications: This study showed that the choice of solvent depends largely on the desired fraction to be extracted. Sesame oil was better extracted with less-polar solvents but membrane-associated lipids are more polar and require polar solvents capable of breaking hydrogen bonds or electrostatic forces. Owing to the differences in solvent capacity, the fatty acids, sterols, and tocopherols extracted along with the oil vary, leading to differences in the quality of the extracted oil. The results obtained in this study could be applied in industrial extraction to encourage the use of alternative extraction solvents.

Dispersion Property of CO2 in Oil. 1. Volume Expansion of CO2 + Alkane at near Critical and Supercritical Condition of CO2

Abstract: To investigate the effect of alkane molecular structure on the volume expansion of CO2 + alkane systems, the solubility of CO2 in hexane, octane, decane, and cyclohexane and the volume of CO2 + alkanes at different temperature and pressure was measured with a PVT apparatus. The results imply that the dispersion state of CO2 molecules in the alkane phase under near critical or supercritical condition of CO2 plays a dominate role in increasing the volume of CO2 + alkane systems. The solubility of CO2 in the alkanes, the volume expansion of the CO2 + alkane systems, and the London force operating within alkane molecules are strongly influenced by molecular structure of the alkanes and pressure.

Determination of Total Phenolic Content in Olive Oil Samples by UV–visible Spectrometry and Multivariate Calibration

Abstract: The viability of determining the total phenolic content in olive oil samples by chemometric analysis of UV–vis spectral data was studied. As a result, a novel spectrophotometric method that does not require prior analyte separation is proposed. The method uses partial least squares (PLS) regression modeling in conjunction with UV–vis absorption spectral data obtained on oil samples dissolved in hexane. The resulting PLS model was developed by correlating the total phenolic content determined by Folin–Ciocalteu assay with the spectral data of oil solution between 210 and 340 nm. The predictive ability of the model was good as indicated by the root mean square error of prediction (RMSEP) and relative error (6.7 mg kg−1 and 6.1%, respectively) obtained for analysis of the validation set of samples. The principal figures of merit, namely limit of detection (7.3 mg kg−1), analytical sensitivity (1.0 mg kg−1) and precision (<10% RSD) were considered adequate for routine analysis. The proposed method was applied in the determination of total phenolic content in Chilean extra virgin olive oil (VOO) samples from the 2009 and 2010 harvest period. The results were compared to those determined with liquid chromatography.

Influence of different immobilization techniques for Candida cylindracea lipase on its stability and fish oil hydrolysis

Abstract: The type of enzyme immobilization has been associated with the degree of stabilization/modification of the protein structure, which ultimately determines its activity and stability under different conditions (temperature, solvent and substrate). The thermal stability and the stability in solvated reaction medium of different derivatives of Candida cylindracea lipase (CCL) were evaluated for their hydrolysis activity of p-nitrophenyl butyrate and in obtaining Omega-3 fatty acids EPA and DHA from fish oil triacylglycerols. CCL was immobilized by hydrophobic interactions and by covalent binding. In addition, hydrophobic derivatives were cross linked with functional polymers, such as dextran aldehyde and dextran sulfate, after chemical amination of its surface to prevent lipase desorption. Fish oil hydrolysis reactions were carried out using 35 U of biocatalyst per gram of oil, at 37 °C and with a 1:1 aqueous/organic phase ratio. The aqueous phase was a 40% polyethylene glycol/phosphate buffer solution, pH 7, and the organic phase a 1:4 fish oil/hexane solution. According to its half-life time, the most thermostable derivative corresponds to CCL immobilized in glyoxyl-agarose. Derivatives of CCL immobilized on octyl-agarose (O-CCL) and CCL immobilized on octyl-agarose cross linked with dextran sulfate (O-CCL-NH 2 -DxSO 4 ) showed an activation effect of about 10 folds compared to its initial activity when they were incubated in solvent and co-solvent biphasic reaction media. After 48 h of reaction, O-CCL and O-CCL-NH 2 -DxSO 4 were those derivatives with highest yields of fish oil hydrolysis; its differential rate of hydrolysis detected for polyunsaturated fatty acids make them a valuable tool for EPA/DHA glycerides concentration.

Extraction of Mucuna seed oil using supercritical carbon dioxide to increase the concentration of l-Dopa in the defatted meal

Abstract: The main aim of this investigation was to extract oil from seeds of Mucuna in order to increase the concentration of l -Dopa in the defatted Mucuna meal. Three different varieties of Mucuna ( aterrima , cinerium , deeringiana ) and solvents (supercritical carbon dioxide, dichloromethane, hexane) were used. The experiments under supercritical CO 2 conditions were performed in a laboratory scale unit at 40 and 60 °C over the pressure range from 150 to 250 bar. A constant flow rate of CO 2 close to 3 mL/min was always kept. The results revealed that temperature, pressure and density were important variables for CO 2 extraction. The concentration of l -Dopa in the defatted meal from supercritical fluid extraction was always higher than those without oil extraction or extracted using organic solvents. Quantitative and qualitative analyses of the oil extracted under the different investigated experimental conditions shown no significant differences in terms of fatty acid and free glycerol compounds. The same analyses indicated linoleic acid (omega-6) as the major oil component and a content of free fatty acids in the oil extracted with supercritical CO 2 close to 5%. The kinetics of oil extraction with CO 2 was also investigated at all the considered operating conditions.

Characterization of oil including astaxanthin extracted from krill (Euphausia superba) using supercritical carbon dioxide and organic solvent as comparative method

Abstract: Krill oil including astaxanthin was extracted using supercritical CO2 and hexane. The effects of different parameters such as pressure (15 to 25MPa), temperature (35 to 45 °C), and extraction time, were investigated. The flow rate of CO2 (22 gmin−1) was constant for the entire extraction period of 2.5 h. The maximum oil yield was found at higher extraction temperature and pressure. The oil obtained by SC-CO2 extraction contained a high percentage of polyunsaturated fatty acids, especially EPA and DHA. The acidity and peroxide value of krill oil obtained by SC-CO2 extraction were lower than that of the oil obtained by hexane. The SC-CO2 extracted oil showed more stability than the oil obtained by hexane extraction. The amount of astaxanthin in krill oil was determined by HPLC and compared at different extraction conditions. The maximum yield of astaxanthin was found in krill oil extracted at 25 MPa and 45 °C.

Selective Extraction of 1-Hexene Against n-Hexane in Ionic Liquids with or without Silver Salt

Abstract: This paper presents an extensive study on the feasibility of ionic liquids (ILs) for the extractive separation of a 1-hexene/n-hexane mixture. Seventeen ILs were tested at 313 K. The extraction sel...

Syntheses, structures, and photoluminescence of three cadmium(II) coordination polymers with flexible bis(benzimidazole) ligands

Abstract: Three cadmium(II) coordination polymers, [CdBr2(L1)] n (1), [CdI2(L2)] n (2), and Cd2Br4(L3)2 (3), where L1 = 1,3-bis(5,6-dimethylbenzimidazole)propane, L2 = 1,4-bis(5,6-dimethylbenzimidazole)butane, and L3 = 1,6-bis(5,6-dimethylbenzimidazole)hexane, have been synthesized by hydrothermal methods and characterized by elemental analyses, IR spectra, TGA, PXRD, and X-ray crystallographic diffraction. Complex 1 contains a 1-D helical chain in which CdBr2 units are linked by L1. For 2, each CdI2 is connected by two different conformations of L2 to form a 1-D zigzag chain. For 3, each CdBr2 is linked by L3 bridges to afford a binuclear structure. These results indicate that the spacer length of the ligands play important roles in assembly of Cd(II) coordination polymers. Thermogravimetric analyses and solid-state luminescent properties of the complexes have also been investigated.

Lipase-catalyzed esterification of lactic acid in supercritical carbon dioxide

Abstract: Lactate esters can be used in food industry for preservation and flavouring purpose, as well as in the pharmaceutical and cosmetic industries. Direct esterification of n -butanol and lactic acid (LA), catalyzed by immobilized lipase B from Candida antarctica (Novozyme 435), was performed in supercritical carbon dioxide (SC CO 2 ) with or without co-solvent. Process conditions (pressure and temperature) were optimized performing experiments in a high-pressure batch stirred-tank reactor. Experiments were carried out in the operative pressure range from 7.5 to 40 MPa and at temperatures 35 °C and 55 °C. The highest conversion of LA after 26 h of reaction performance was obtained in SC CO 2 with n -hexane serving as a co-solvent, at 40 MPa and 55 °C. The optimal temperature and pressure for butyl lactate (BL) synthesis in SC CO 2 medium was determined at 55 °C and 30 MPa. Phase behavior for LA/ n -butanol/SC CO 2 system and LA/ n -butanol/ n -hexane/SC CO 2 system at different pressures and temperatures was also studied.

Adsorption Characteristics of Pentane, Hexane, and Heptane: Comparison of Hydrophobic Hypercrosslinked Polymeric Adsorbent with Activated Carbon

Abstract: The adsorption isotherm data of light hydrocarbons (C5's–C7’s, pentane, hexane, and heptane), which are the main composition of gasoline vapor, onto hydrophobic hypercrosslinked polymeric adsorbent (HY-1) were measured at temperatures ranging from (293 to 323) K and pressures up to 60 kPa and compared with granular activated carbon (NucharWV-A 1100). The experimental data were fitted to the Langmuir, Freundlich, and Dubinin–Astakhov (DA) equations, respectively. The DA isotherms correlated with the experimental data within 1.85 % root-mean-square deviation (rmsd) and presented a better fitting than Langmuir and Freundlich equations. The experimental results indicated that HY-1 had good adsorption capacities for three hydrocarbon VOCs, which were about 85 % of those of NucharWV-A 1100. The average adsorption heats of three hydrocarbon VOCs onto HY-1 were smaller than those of NucharWV-A 1100, implying three hydrocarbon VOCs were adsorbed onto HY-1 more weakly and HY-1 could be regenerated more easily. Take...

Pentane-hexane solvent in situ recovery of heavy oil

Abstract: An integrated thermal recovery process using a solvent of a pentane or hexane or both as an additive to, or sole component of, a gravity-dominated process for recovering bitumen or heavy oil from a reservoir. A pentane-hexane specific solvent fraction is extracted at surface from a diluent stream. That pentane-hexane solvent fraction is then injected into the reservoir as part of a gravity-dominated recovery process within the reservoir, and when that solvent fraction is subsequently produced as part of the oil or bitumen blend, it is allowed to remain within the blend to enhance the subsequent blend treating and transportation steps. Meanwhile, the remainder of the diluent from which the solvent stream had been extracted is utilized at surface as a blending stream to serve as an aid in treating of produced fluids and also to serve as a means of rendering the bitumen or heavy oil stream pipelineable.

Factors Affecting the Stability of Crude Oil Emulsions

Abstract: Crude oils are typically water in crude oil (w/o) emulsions, which are often very stable. Among the indigenous natural surfactants contained in the crude oils, asphaltenes and resins are known to play an important role in the formation and stability of w/o emulsions. Asphaltenes are defined as the fraction of the crude oil precipitating in pentane, hexane, or heptane, but soluble in toluene or benzene. Asphaltenes are the most polar and heaviest compounds in the crude oil. They are composed of several poly nuclear aromatic sheets surrounded by hydrocarbon tails, and form particles whose molar masses are included between 500 and 20,000 g mol-1. They contain many functional groups, including some acids and bases. Resins are molecules defined as being soluble in light alkanes (pentane, hexane, or heptane), but insoluble in liquid propane. They consist mainly of naphthenic aromatic hydrocarbons; generally aromatic ring systems with alicyclic chains. Resins are effective as dispersants of asphaltenes in crude oil. It was postulated that asphaltenes stabilize w/o emulsions in two steps. First, disk-like asphaltene molecules aggregate into particles or micelles, which are interfacially active. Then, these entities upon adsorbing at the w/o interface aggregate through physical interactions and form an interfacial network.