Presence Of N-hexane Research Articles

Lipase-Catalyzed Synthesis of Cetyl Palmitate in the Presence of n-Hexane and Ethyl Ether

Cetyl palmitate was produced by the esterification of palmitic acid with cetyl alcohol using n-hexane and ethyl ether as solvents and a commercial lipase as a catalyst. The effect of solvents to reagents mass ratio (0.5 : 1–3 : 1), percentage of n-hexane in the solvent mixture (0–100%), and reaction temperature (25–55°C) on the reaction rate were evaluated for a fixed amount of enzyme (1 wt% related to the total mass of substrates) in an equimolar mixture of palmitic acid and cetyl alcohol. Temperature and n-hexane percentage in the solvent had positive effects on the reaction rate. The total solvent-to-reagent mass ratio showed a negative effect on the reaction rate when a solvent mixture rich in ethyl ether was used. The higher the concentration of n-hexane, the lower the effect of the mass ratio of solvents to reagents on the reaction rate. Although the amount of ethyl ether in the solvent mixture had a negative effect on the reaction rate, it had a positive effect on the solubility of the system, that is, the more ethyl ether in the mixture, the lower the solvent to reagents mass ratio required to ensure a homogeneous mixture. A ping-pong bi-bi mechanism-based model was proposed to represent the system kinetics and was well fitted to the experimental data.

Analytical Method for Melengestrol Acetate in Livestock Products Using LC-MS/MS

The present study verified that it is possible to analyze melengesterol acetate using the existing multi-residue method. Melengestrol acetate was extracted from livestock products using acidic acetonitrile acidified with acetic acid in the presence of n-hexane and anhydrous sodium sulfate. The crude extracts were cleaned up using an octadecylsilanized silica gel cartridge column. Separation by HPLC was performed using an octadecylsilanized silica gel column with linear gradient elution of 0.1 vol% formic acid and acetonitrile containing 0.1 vol% formic acid. For the determination of the analyte, tandem mass spectrometry with positive ion electrospray ionization was used. In recovery tests using four livestock products fortified with maximum residue limits levels of melengestrol acetate (0.001-0.02 mg/kg), the truenesses ranged from 82% to 100%, and the repeatabilities for the entire procedure ranged from 0.5 RSD% to 5.6 RSD%. In recovery tests using 11 livestock products fortified with 0.0005 mg/kg of melengestrol acetate, the truenesses ranged from 88% to 99%, and the repeatabilities ranged from 1.3 RSD% to 5.4 RSD%. The limit of quantification for melengestrol acetate in livestock products was 0.0005 mg/kg.

In Situ Transesterification from Soybean Seed Using Mechanochemical Methods toward Producing Biodiesel.

The research and development of new routes of biodiesel synthesis have been increasingly in line with the principles of green chemistry. In this sense, mechanochemistry is a promising technique, able to ally the energetic potential with reductions in the use of solvents and steps of treatment of the sample and the purification of the product. To date, this is the first work using mechanochemistry directly in extracting soybean oil from its seed and the in situ transesterification reaction by applying a reactive soybean oil extraction process. The presence of n-hexane was studied in different molar proportions (relative to the oil content), and a low solvent consumption in a 3:1 ratio was adopted. Mechanochemistry favored oil diffusion in the n-hexane solvent, resulting in a mean triglyceride content equal to 90%, against 66% obtained in the tests without spheres in the planetary ball mill. The catalyst content was also evaluated, and 4% NaOH (weight, concerning the oil) was the concentration that presented less residue of nontransesterified glycerides in the samples for ethyl ester preparation. Additionally, the protein content was determined on the residual soybean cake, with no loss of nutritional potential when subjected to the mechanochemical process.

Исследование активности бифункциональных катализаторов на превращение н-гексана

The production of various motor fuels is carried out by processing light fractions of oil with an initial temperature of boiling to 350°С. The current trend shows that oil in new fields has more weight than before. New oil reservoirs are deeper with a greater proportion of dark fraction with a boiling point of 350°С. This situation stimulates to find new ways of increasing the processing depth light fractions for synthesis target product. One of the main solution path for the problem is creation of new catalytic systems or modernization of existing ones. Motor fuels must meet the necessary operational and environmental characteristics, which is determined by their chemical composition. This article is devoted to the study of bifunctional catalyzers for the conversion of n-hexane. High molecular zeolite CVM (ZSM-5) was used as a carrier, which has functionality due to the presence of various active centers. Platinum (Pt/CVM), praseodymium (Pr/CVM) were also applied to the carrier, and praseodymium and platinum (Pt,Pr/CVM) were successively applied by impregnation. Normal hexane was used as a raw material. The choice of this raw material is associated with the ability to aromatization reaction, as well as the presence of n-hexane in the raw materials of the process of obtaining motor fuels-catalytic reforming. As a result of the transformation of raw materials, liquid fuel of multicomponent composition with the number of carbon atoms in the chain from 3 to 14, as well as gases containing C1 – C5 hydrocarbons, was obtained. When n-hexane is converted on the catalyzers under study, both the octane number and the content of aromatic hydrocarbons increase with increasing temperature. It has been found that when the process is carried out at a temperature of 450°C, the highest yield of the catalysate is (33.8% by weight.) on a Pt,Pr/CVM catalyzer. With an increase in temperature, the yield of benzene increases. Minimum benzene yield (0.6 wt. %) is achieved at 450°C marked by a bimetallic catalyzer, which corresponds to the EURO-5 gasoline standard. The highest degree of conversion was observed during the conversion of n-hexane on the Pt,Pr/CMC catalytic system at a temperature of 450° C, which was (97%).

Interactive effects of dual short-chain n-alkanes on removal performances and microbial responses of biotrickling filters

Enhanced biotrickling filtration at the presence of surfactants could be competitive in treatment of waste gas streams polluted by hydrophobic volatile organic compounds (VOCs) such as light hydrocarbons, while few such reports are available. Herein, biotrickling filters (BTFs) were applied to investigate the removal performances for binary-component n-alkanes (n ≤ 6) at the presence of sodium dodecyl benzene sulfonate (SDBS), and the microbial responses were also examined. Interestingly, results showed that the existence of shorter chain n-alkanes promoted the removal of longer chain n-alkanes, as the elimination capacities (EC) of BTF for n-hexane increased by 44 ± 1.2 % when there was methane in incoming gas stream. While the presence of longer chain n-alkanes antagonistically affected shorter chain n-alkane removal, as EC for methane decreased by 65 ± 8.1 % at the presence of n-hexane. Additionally, the presence of SDBS improved the mixed n-alkane removal. EC of the BTF with 15 mg/L SDBS for mixed propane and n-hexane reached 55 ± 1.4 and 31 ± 0.5 g/m3·h respectively, which increased by 90 ± 4.6 % and 47 ± 0.9 % compared with those without SDBS. The richness of Bacillus and Sporosarcina was improved in the BTF fed with SDBS. Moreover, the presence of SDBS improved the content of hydrophobic proteins and the activity of fluorescent substances inextracellular polymeric substances. Also, both the activities of ATPase and the antioxidant capacity of microbial cells exhibited higher than that when SDBS was not added. These data could lead to a better understanding and more reasonable design of biotrickling filtration to remove n-alkanes from waste gas streams of refinery wastewater treatment plants.

Honge Oil Biodiesel as a Promising feedstock – An Experimental Investigation

The performance, combustion and emission characteristics of a vertical air-cooled single-cylinder four-stroke diesel engine fueled with karanja (honge) and diesel oil blends with B20 (20% biodiesel and 80% diesel), B50 (50% biodiesel and 50% diesel) and B100 were experimental tested (100% biodiesel). The bio-oil was extracted using soxhlet extractor and mechanical pressing in the presence of n-hexane. The transesterification process was accomplished through two stage process with NaOH and methanol. Performance parameters evaluated include Thermal Braking Efficiency (BTE), Specific Fuel Consumption (SFC), Total Fuel Consumption (TFC) and Braking Performance (BP). Heat Release Rate (HRR) and pressure-crank angle diagram are two of the combustion properties evaluated. Carbon dioxide (CO2), carbon monoxide (CO), hydrocarbons (HC), nitrogen oxides (NOx) and oxygen (O2) are among the emission characteristics examined. These parameters were determined under constant load conditions of 0%, 25%, 50%, 75% and 100% at the rated speed of 1500 rpm and the results for each karanja oil blend (B20, B50, B100) were compared to diesel. As a result, it is concluded that B20 blend offers superior performance, combustion and emission characteristics compared to other test fuel blends.

Genomic analysis of Acinetobacter pittii CEP14 reveals its extensive biodegradation capabilities, including cometabolic degradation of cis-1,2-dichloroethene.

Halogenated organic compounds are naturally occurring in subsurface environments; however, accumulation of the degradative intermediate cis-1,2-dichloroethene (cDCE) at soil and groundwater sites contaminated with xenobiotic chlorinated ethenes is a global environmental and public health issue. Identifying microorganisms capable of cDCE degradation in these environments is of interest because of their potential application to bioremediation techniques. In this study, we sequenced, assembled, and analyzed the complete genome of Acinetobacter pittii CEP14, a strain isolated from chloroethene-contaminated groundwater, that has demonstrated the ability for aerobic cometabolic degradation of cDCE in the presence of n-hexane, phenol, and toluene. The A. pittii CEP14 genome consists of a 3.93Mbp-long chromosome (GenBank accession no. CP084921) with a GC content of 38.9% and three plasmids (GenBank accession no. CP084922, CP084923, and CP084924). Gene function was assigned to 83.4% of the 3,930 coding DNA sequences. Functional annotation of the genome revealed that the CEP14 strain possessed all genetic elements to mediate the degradation of a range of aliphatic and aromatic compounds, including n-hexane and phenol. In addition, it harbors gene clusters involved in cytosol detoxification and oxidative stress resistance, which could play a role in the mitigation of toxic chemical intermediates that can arise during the degradation of cDCE. Gene clusters for heavy metal and antibiotic resistance were also identified in the genome of CEP14. These results suggest that CEP14 may be a versatile degrader of xenobiotic compounds and well-adapted to polluted environments, where a combination of heavy metal and organic compound pollution is often found.

Development of an Analytical Method for Simultaneous Determinationof Quinolones and Tetracyclines in Livestock and Fishery Products

In this study, we developed an analytical method for simultaneous determination of 14 quinolones and 4 tetracyclines in livestock and fishery products using LC-MS/MS. The analytes were extracted from food samples with citrate buffer (containing EDTA)-methanol-acetonitrile (3 : 1 : 1, v/v/v) in the presence of n-hexane, and the extract was purified with an Oasis PRiME HLB cartridge column. It was suggested that this analytical method can also extract analytes from solid samples containing fat by using n-hexane. In addition, using methanol-acetonitrile (3 : 7, v/v) containing 0.1 vol% formic acid as an eluent from the cartridge column, the purification effect could be improved, while minimizing the impairment of the recovery rate. As a result of the validation using six types of food samples, trueness (accuracy) was 70.6%-113.8%, the RSD of repeatability was 9.0% or less, and the RSD of within-laboratory reproducibility was 15.5% or less. Using this approach, the standard values mentioned in the Japanese guideline were successfully met.

Enhanced dispersion and antibacterial activity of mechanically exfoliated graphite flakes in the presence of n-hexane and NaCl

We report on the high dispersion and antibacterial performance (AP) of graphite flakes prepared by the mechanical exfoliation of bulk graphite materials using wet high energy ball milling (BM) in the presence of NaCl and n-hexane. Synergic effects of functionalized surfaces and sharp edges of well-dispersed carbon flakes offer high dispersion, and promising AP against Escherichia coli (E. coli) through damaging its cell membrane. This paper reports on the facile and green preparation of exfoliated graphitic flakes with enhanced AP.

Enhancement of pyocyanin production by Pseudomonas aeruginosa via the addition of n-hexane as an oxygen vector

Abstract Pseudomonas aeruginosa is capable of producing a wide range of industrially important biotechnological products like pigment, biosurfactants, enzymes, etc. Pyocyanin is a pigment produced by P. aeruginosa and widely used in many industries such as food, agriculture, pharmaceuticals and cosmetics. In order to increase the production of pyocyanin, in this study, the effects of previously untested oxygen vectors on P. aeruginosa OG1 pyocyanin production were studied. The oxygen vectors (n-hexadecane, n-dodecane and n-hexane) were compared in terms of pyocyanin production. All of the oxygen vectors were found to exhibit a stimulatory effect on pyocyanin production and the best result (11.96 mg/L) was obtained with n-hexane. In the next step, pyocyanin production in the presence of n-hexane, was optimized by response surface methodology. In addition to the n-hexane concentration, the optimum size of inoculum and the time of n-hexane addition to the fermentation liquid were investigated. Experimental design and the results were analysed by using Box-Behnken design of Response Surface Methodology (RSM). Accordingly, the optimum size of inoculum was found to be 2.07%, n-hexane concentration was 3.48% and the addition time was 33.93 h and at these optimum values, the amount of pyocyanin increased 2-fold (21.2 mg/L). According to these results, n-hexane addition as an oxygen carrier could be a useful technique in industrial production of pyocyanin.

Fabrication of Magnetic CLEA-protease Nanocomposite: High Progression in Biotechnology and Protein Waste Management

Magnetic nanocomposite opens ample opportunities for large scale application in industrial biocatalyst market. In this study, we isolated a high potent protease producing Bacillus cereus from several slaughterhouse wastes located in Kerman province, Iran. Results showed that, it was an organic solvent tolerant, thermophile protease which showed 20% increase in protease stability in the presence of n-hexane. It was active in a wide range of pHs and temperatures. A magnetic CLEA-protease nanocomposite (mCLEA-P-NC) was constructed successfully which confirmed by SEM and FTIR analysis. mCLEA-P-NC displayed Km value 4.6 folds lower than free enzyme. Biotechnological applications showed nearly 44% of proteins which obtained from waste water of local yogurt were degraded by mCLEA-P-NC. In addition, it showed high potential in silver recovery and de-haring process. A simple mechanic system was manifested to use mCLEA-P-NC in washing performance. These results indicated high potential of this protease nanocomposite in biotechnological application especially in recycling of waste proteins and washing performance.

Determination of Hexazinone and Its Major Metabolites in Livestock Products by LC-MS/MS

A method for the determination of hexazinone and three metabolites (hexazinone metabolite B, hexazinone metabolite C, hexazinone metabolite F) in livestock products by LC-MS/MS was developed. Hexazinone and the three metabolites were extracted from a sample with acetonitrile in the presence of n-hexane, and lipid was removed by acetonitrile/n-hexane partition. The acetonitrile extract was cleaned up using a SAX/PSA cartridge column. Average recoveries (n=5) of hexazinone and the three metabolites from cattle meat, fat, liver and milk spiked at the maximum residue limits (MRLs) or at 0.0025 mg/kg ranged from 85.6 to 96.0%, and the relative standard deviations ranged from 0.8 to 4.9%.

Modeling Condensed Mode Operation for Ethylene Polymerization: Part III. Mass and Heat Transfer

The polymer flow model is employed to predict the transient behavior of the concentration and temperature profiles within the growing particles during gas-phase ethylene polymerization in the absence and presence of n-hexane as the induced condensing agent. It is demonstrated that by accurate estimation of the model parameters, one can precisely describe the impact of gas phase composition on the reaction rate. The simulation results show that the experimentally observed change in the polymerization rate under the various operating conditions is the direct result of alteration in the average concentration of ethylene in the particle; the average ethylene concentration not only depends on its equilibrium concentration but is also controlled by the significance of the mass transfer resistance through the growing particles. This is while the effect of partial pressure of n-hexane and ethylene on the thermal behavior of the particle is found to be insignificant for the studied experiments.

Incorporation of capric acid in pumpkin seed oil by sn-1,3 regioselective lipase-catalyzed acidolysis

Structured lipids (SLs) are novel triacylglycerols obtained by changing the native fatty acid (FA) profiles or by the incorporation of a new desired FA in the acylglycerol backbone. These modified fats present important medical and functional properties for food applications. This work aimed to synthetize a MLM-type SL, which consists of triacylglycerols containing a medium-chain FA (M) at sn-1,3 positions and a long-chain FA (L) at sn-2 position, by acidolysis of pumpkin seed oil with capric acid, catalyzed by a commercial lipase preparation from Thermomyces lanuginosa (Lipozyme TL IM). Reactions were performed at 45 °C, in solvent-free media, at 1:2 molar ratio (pumpkin seed oil:capric acid) and a fixed amount of immobilized lipase of 5%, 10%, 15% or 20%. Incorporations of C10:0 increased with time up to 31 h (29.9 ± 0.7 mol-%) when 5% lipase load was used. Significant differences were only observed between the results obtained with 5 and 20% of biocatalyst load. The subsequent experiment was carried out with 5% lipase load, at 45 °C, 1:2 molar ratio and in the presence of n-hexane. The results showed slightly higher incorporation yields in the presence of solvent, namely at 48 h-reaction (34.7 ± 1.0 mol-%). However, since the structured lipids are to be used in food products, together with environmental and economic concerns, solvent-free systems are preferred. In this study, the synthesis of a MLM-type SL from pumpkin seed oil for food uses was well succeeded.

Biodiesel: A Cost-effective Fuel Using Waste Materials

The main disadvantage of biodiesel is its high price. The price of biodiesel depends on various factors such as the price of oil, methanol, catalyst, and labor. Among dif-ferent economic factors, oil accounts for the largest share of input costs of biodiesel production. In this study, first, suitable heterogeneous catalysts were identified for biodiesel production. Several studies were carried out on biodiesel production using heterogeneous catalysts. All of these studies were designed to confirm that the pro-duction of biodiesel was cheaper than that of petroleum diesel. Waste materials as feedstock were used for this purpose. In transesterification reaction, waste cooking oil and waste materials were used as catalysts. Alkaline earth metal oxides catalysts are the best kind of heterogeneous catalysts. The catalytic reactivity of alkaline earth metal oxides including waste source of calcium oxide and magnesium oxide, CaO/Al2O3, CaO/SiO2, BaO/SiO2, and MgO/SiO2 were evaluated by the transesterification of oil and methanol. In this study, the costs of produced biodiesel were compared for different sources. The results indicated that the cost of produced biodiesel using synthetic catalysts was 1.26 to 1.49 times that using natural catalysts (1.26 and 1.49 are related to waste cooking oil and refined oil, respectively). Consequently, using waste cooking oils and natural catalysts is recommended for biodiesel production. Also, n-hexane as co-solvent was used to increase the solubility of methanol in oil. In presence of n-hexane, the cost of biodiesel production was approximately reduced by 16%.

Purification and Properties of Extracellular Lipases with Transesterification Activity and 1,3-Regioselectivity from Rhizomucor miehei and Rhizopus oryzae

Rhizomucor miehei NRRL 5282 and Rhizopus oryzae NRRL 1526 can produce lipases with high synthetic activities in wheat bran-based solid-state culture. In this study, the purification and biochemical characterization of the lipolytic activities of these lipases are presented. SDS-PAGE indicated a molecular mass of about 55 and 35 kDa for the purified R. miehei and Rh. oryzae enzymes, respectively. p-Nitrophenyl palmitate (pNPP) hydrolysis was maximal at 40°C and pH 7.0 for the R. miehei lipase, and at 30°C and pH 5.2 for the Rh. oryzae enzyme. The enzymes showed almost equal affinity to pNPP, but the Vmax of the Rh. oryzae lipase was about 1.13 times higher than that determined for R. miehei using the same substrate. For both enzymes, a dramatic loss of activity was observed in the presence of 5 mM Hg2+, Zn2+, or Mn2+, 10 mM N-bromosuccinimide or sodium dodecyl sulfate, and 5-10% (v/v) of hexanol or butanol. At the same time, they proved to be extraordinarily stable in the presence of n-hexane, cyclohexane, n-heptane, and isooctane. Moreover, isopentanol up to 10% (v/v) and propionic acid in 1 mM concentrations increased the pNPP hydrolyzing activity of R. miehei lipase. Both enzymes had 1,3-regioselectivity, and efficiently hydrolyzed p-nitrophenyl (pNP) esters with C8-C16 acids, exhibiting maximum activity towards pNP-caprylate (R. miehei) and pNP-dodecanoate (Rh. oryzae). The purified lipases are promising candidates for various biotechnological applications.

Modeling Condensed Mode Operation for Ethylene Polymerization: Part I. Thermodynamics of Sorption

A process model based on the thermodynamic models of Sanchez–Lacombe and PC-SAFT EoS is developed to simulate and analyze the impact of vaporized n-hexane as an induced condensing agent on the rate of gas phase ethylene polymerization on supported catalyst. The simulation results of the process model indicate that the cosolubility phenomenon (i.e., the enhancement in the equilibrium concentration of ethylene in the amorphous phase of polyethylene in the presence of n-hexane) cannot be the sole reason for the experimentally observed increase in the polymerization rate seen over the entire duration of reaction. At the beginning, the rate of ethylene polymerization is enhanced much more strongly than would be expected simply from the cosolubility effect alone. However, as the reaction proceeds, the enhancement magnitude gradually decreases and reaches a steady-state value corresponding to the promotion magnitude in the equilibrium concentration of ethylene predicted by the two thermodynamic models.

Zinc Oxide Nanoparticles Supported Lipase Immobilization for Biotransformation in Organic Solvents: A Facile Synthesis of Geranyl Acetate, Effect of Operative Variables and Kinetic Study.

The present study describes grafting of zinc oxide (ZnO) nanoparticles with polyethyleneimine (PEI) followed by modification with glutraldehyde used as the bridge for binding the enzyme to support. The prepared nanocomposites were then characterized using Fourier transform infrared spectroscopy, thermogravimetric analysis, and transmission electron microscopy, utilized for synthesis of geranyl acetate in n-hexane. Among all the three prepared nanocomposites (ZnO + PEI, ZnO + PEI + SAA, ZnO + PEI + GLU), Candida rugosa lipase immobilized on ZnO-PEI-GLU was found to be best for higher ester synthesis. The operating conditions that maximized geranyl acetate resulted in the highest yield of 94% in 6h, molar ratio of 0.1:0.4M (geraniol/vinyl acetate) in the presence of n-hexane as reaction medium. Various kinetic parameters such as V max, K i(G), K m(G), and K m(VA) were determined using nonlinear regression analysis for order bi-bi mechanism. The kinetic study showed that reaction followed order bi-bi mechanism with inhibition by geraniol. Activation energy (E a ) was found to be lower for immobilized lipase (12.31kJmol(-1)) than crude lipase (19.04kJmol(-1)) indicating better catalytic efficiency of immobilized lipase. Immobilized biocatalyst demonstrated 2.23-fold increased catalytic activity than crude lipase and recycled 20 times. The studies revealed in this work showed a promising perspective of using low-cost nanobiocatalysts to overcome the well-known drawbacks of the chemical-catalyzed route.

PERFORMANCE OF LOOFA-IMMOBILIZED Rhizopus oryzae IN THE ENZYMATIC PRODUCTION OF BIODIESEL WITH USE OF OLEIC ACID IN n-HEXANE MEDIUM

The performance of loofa-immobilized Rhizopus oryzae (as a whole-cell biocatalyst) in the synthesis of methyl oleate was evaluated using oleic acid as a model substrate. The activities of the cell-bound lipase in terms of the esterification and hydrolysis reactions were found to be higher for the immobilized cells as compared with those of the free cells. The time to reach equilibrium for methyl oleate synthesis was 12 h in the presence of n-hexane (hexane:oleic acid ratio 9:1(v/v)), and the yield was 80%. In the absence of solvent, equilibrium was reached after 48 h and the yield was only 30%. The moisture repellency and the hydrophilic properties of loofa sponge make this natural fiber a good candidate for cell-enzyme immobilization, especially for lipases as the interfacial enzyme.

ArF excimer laser-induced deposition of Ag/C nanocomposite thin films in the presence of n-Hexane

Abstract Ag/C nanocomposite thin films with different Ag/C molar ratios have been prepared using ArF excimer laser-induced ablation process and silver target under n-Hexane atmosphere. The morphology, crystal structure and composition of as-deposited Ag/C nanocomposite thin films were investigated with high resolution electronic microscopic techniques (including scanning electron microscopy and transmission electron microscopy) and energy-dispersive X-ray spectroscopy, respectively. Laser Raman spectroscopy and Fourier transform infrared spectroscopy techniques were also applied to characterize the final carbonaceous products generated from n-Hexane under laser ablation process. The optical emission of the plume caused by the interaction between excimer laser and silver target in the presence of n-Hexane was studied to understand the possible reaction process. The UV–vis absorption of as-deposited Ag/C thin films, which is attributed to the surface plasmonic excitation, was also investigated in the present work.