Use Of N-hexane Research Articles

Catalytic Oxidative Desulfurization of 4-Methyldibenzothiophene by Ni/Al Modified Titanium Dioxide and Zinc Oxide

In this study, composite layer double hydroxide-metal oxide catalysts (Ni/Al-TiO2 and Ni/Al-ZnO) were successfully prepared and utilized for the oxidative desulfurization of dibenzothiophene. The catalysts were characterized using XRD, FTIR, and SEM-EDS analysis. The diffraction patterns confirmed the successful synthesis of the composite materials, while the FTIR spectra exhibited absorption bands at specific wavenumbers 3480 cm-1, 1630 cm-1, 1376 cm-1, 830 cm-1, 775 cm-1, and 683 cm-1. The surface morphology of the catalysts showed variations, with Ni/Al-LDH having a smooth particle surface and long particle shape, while Ni/Al-ZnO and Ni/Al-TiO2 formed grain-like or aggregated structures. EDS analysis confirmed the presence of Ni/Al, Ti, and Zn elements in the composites, with Ti and Zn accounting for 29.3% and 10.7% of the composite mass, respectively. The optimized reaction conditions included a reaction time of 40 minutes, catalyst dosage of 0.25 g, temperature of 50°C, and the use of n-hexane as the solvent. The catalysts demonstrated a heterogeneous nature and proved to be reusable, as the conversion of dibenzothiophene remained above 90% even after three catalytic reactions, with Ni/Al-TiO2 and Ni/Al-ZnO composites maintaining conversion rates of 99.36% and 99.32%, respectively.

Synthesis of Highly Dispersed Spherical Metal Granules by Laser Ablation Method

The work is devoted to the problem of synthesis of highly dispersed spherical powder granules by laser ablation. The formation of microspheres is carried out by the action of femtosecond laser radiation on the surface of a titanium target in a two-component reaction medium. The process of titanium treatment in n-hexane by ultrashort laser pulses is investigated. It is shown that the use of n-hexane as a working medium component allows the synthesis of micro-and nanopowders containing titanium carbide, which are resistant to atmospheric environment during prolonged exposure. The presented method provides the possibility of synthesis of high-purity powder materials with typical sizes from 1 to 3 microns.

Cleaning Fabricated Metal Thread: A Post‐treatment Stability Assessment after Artificial Deterioration and the Application of Synthetic Soil

To study the cleaning effects and post-treatment stability assessment of various methods of cleaning textiles with metal thread, six naturally-soiled historical textiles with metal thread were investigated at the Metropolitan Museum of Art, New York. Prior to the cleaning of fabricated gold, silver, and copper thread that had been glued onto a paper substrate, the artificial deterioration was carried out in a controlled environment with light(UV and daylight), and temperature and humidity factors which would weaken and damage the samples. A synthetic soil mixture was applied to the samples to imitate soil found on the historic and archaeological textiles with metal thread; the cleaning effect and post-treatment assessment were investigated by use of three textile cleaning methods: mechanical cleaning, wet cleaning, and solvent cleaning. While investigating the naturally-soiled textiles with metal thread, it was determined that the soil colors and sizes of contaminating particles of each textile were different due to the diversity of original environmental factors and conditions. After cleaning with kneaded rubber, Stoddard solvent, n-decane or n-hexane, a bright, clean effect was apparent. Kneaded rubber was successful in picking up both large and small particles, but its stickiness caused some of the metal leaf to peel off. Stoddard solvent produced a good cleaning effect, but after use of n-hexane and n-decane in the cleaning process, a white layer of residue remained on the textile’s surface. Wet cleaning was not effective and the rapid humidity changes between wet and dry conditions caused the edges of the paper substrate to lose their original shape.

Optimisation of Croton gratissimus Oil Extraction by n-Hexane and Ethyl Acetate Using Response Surface Methodology.

The extraction of oil from Croton gratissimus seeds was studied using the three-factor five-level full-factorial central composite rotatable design (CCRD) of the response surface methodology (RSM). The effect of the three factors selected, viz., extraction time, extraction temperature and solvent-to-feed ratio on the extraction oil yield was investigated when n-hexane and ethyl acetate were used as extraction solvents. The coefficients of determination (R2) of the models developed were 0.98 for n-hexane extraction and 0.97 for ethyl acetate extraction. These results demonstrated that the models developed adequately represented the processes they described. From the optimized model, maximum extraction yield obtained from n-hexane and ethyl acetate extraction were 23.88% and 23.25%, respectively. In both cases the extraction temperature and solvent-to-feed ratio were 35°C and 5 mL/g, respectively. In n-hexane extraction the maximum conditions were reached only after 6 min whereas in ethyl acetate extraction it took 20 min to get the maximum extraction oil yield. Oil extraction of Croton gratissimus seeds, in this work, favoured the use of n-hexane as an extraction solvent as it offered higher oil yields at low temperatures and reduced residence times.

Influence of the Support on the Catalytic Characteristics of the Deposited Palladium in the Liquid-Phase Hydrogenation of Diphenylacetylene

Palladium catalysts on various types of supports were studied in the liquid-phase hydrogenation of diphenylacetylene. Samples of Pd/SiO2–Al2O3, Pd/MgAl2O4, Pd/Al2O3, and Pd/TiO2 were characterized by the chemisorption of the CO and IR spectroscopy of adsorbed CO. The use of n-hexane as the solvent increases the reaction rate, which can be explained by the better solubility of hydrogen in the liquid phase. It is established that the acid–base properties of the support do not affect the activity and selectivity of the catalysts in the reaction under study. However, they alter the electronic state of palladium. According to the catalytic tests, Pd/TiO2 has the highest activity (turnover frequency) and selectivity to alkene. The comparison of the obtained catalytic data and the results of IR spectroscopy made it possible to conclude that this is due to the electron density redistribution between the palladium and TiO x particles, which is caused by the strong metal–support interaction.

Phospholipase A1-catalyzed hydrolysis of soy phosphatidylcholine to prepare l-α-glycerylphosphorylcholine in organic-aqueous media

This study aimed to optimize the preparation of l-α-glycerylphosphorylcholine (l-α-GPC) via phospholipase A1 (Lecitase Ultra)-catalyzed hydrolysis of soy phosphatidylcholine (PC). The reaction was performed in n-hexane–water biphasic media in a stirred batch reactor, and modeling and optimization were conducted using response surface methodology. Optimal conditions to completely hydrolyze PC to l-α-GPC were: temperature, 50°C; reaction time, 30h; water content, 69g/100g of PC weight; and enzyme loading, 13g/100g of PC weight. The optimal n-hexane-to-water ratio in the medium was 5.8:1 (v/v), and 21.3g of PC was treated as the substrate in 100mL of the medium. l-α-GPC with purity 99.3g/100g was obtained from the reaction products after diethyl ether extraction and silica column chromatography. These findings suggest that the use of n-hexane–water media increases the productivity of l-α-GPC compared to the aqueous media used in enzymatic reaction systems in other published studies.

Electrochemical, HR-XPS and SERS study of the self-assembly of biphenyl 4,4′-dithiol on Au(111) from solution phase

We report a comparative study of 4,4′-biphenyldithiol adlayers grown on Au(111) substrates in solution phase by different methods. Layers prepared by immersion in solutions of ethanol and n-hexane, with and without the use of a disulfide reducing agent (tris-carboxyethyl phosphine, TCEP), were characterized by electroreductive desorption, impedance spectroscopy, redox activity, high-resolution photoemission spectroscopy, and surface-enhanced Raman spectroscopy. It is shown that the simple immersion in an ethanolic solution leads to the formation of, at least, a bilayer with a high number of SS bonds. The use of n-hexane as solvent produces a drastic reduction of these undesired bonds, and a similar result is obtained if the substrates prepared in the ethanolic solution are then washed with TCEP. The best results were obtained when the reducing agent was added into the ethanol solution, in which case all the characterizations were coincident in the formation of a single layer of standing-up molecules free of SS bonds. The charge of the desorption peak and the relative intensity of the S2p and Au4f photoemission peaks both indicate a surface coverage θ≈0.2. In the case of multilayers formed by immersion in pure ethanolic solutions, the Raman experiments indicate that intralayer SS bonds are not formed, and hence that all the SS bonds are of the interlayer type.

Characterization and Evolution of Exposure to Volatile Organic Compounds in the Spanish Shoemaking Industry over a 5-Year Period

This study measured inhalation exposure to 13 volatile organic compounds (VOCs) among workers in the leatherwear industry in Spain, examined the changes in those exposures over a 5-year period, and documented local exhaust ventilation practices that affected exposure. In collaboration with an occupational risk prevention company, air samples were collected from 849 workers’ personal breathing zones using personal air pumps with activated charcoal tubes. VOCs were analyzed using a GC/MS-optimized method modified in our laboratory from that proposed by Spanish authorities (INSHT). Airborne concentrations were compared with occupational exposure limit (OEL) values from the European authorities. The most frequently detected VOCs were acetone (98.1%), toluene (94.8%), n-hexane (71.2%) and other C6-C7 branched alkyl hydrocarbons (97.5%). Other frequently detected VOCs were MEK (64.9%), ethylacetate (60.7%), and cyclohexane (29.3%). Benzene was detected in 24.6% of samples. Although all the samples were taken while workers performed tasks judged to have the highest VOC exposure potential, only 14% of samples showed excessive aggregate exposure, and chemical-specific OELs were exceeded in a relatively small number of cases: 7.2% for n-hexane, 2.8% for toluene, 0.6% for acetone, and 0.4% for hexane isomers. Over the study period, a diminished use of n-hexane in solvent formulations and an increased use of branched hexane and heptane isomers were observed. Six factors relating to work location conditions and types were evaluated. Most high-exposure cases were associated with three task types. The presence of local exhaust ventilation was an important exposure control, but significant exposures despite the use of local exhaust were observed. Although n-hexane exposures significantly decreased over the study period, the overall level of VOC exposure did not decrease. More effective exposure prevention measures need to be implemented. [Supplementary materials are available for this article. Go to the publisher's online edition of Journal of Occupational and Environmental Hygiene for the following free supplemental resource: a file containing a descriptive analysis of the results, the influence of several workplace factors in the exposure and the accomplishment of the regulations in terms of occupational exposure limits.]

Approach to develop a standardized TLC-DPPH test for assessing free radical scavenging properties of selected phenolic compounds

TLC-DPPH(•) test belongs to a group of frequently performed assays aimed at detection of compounds with desired activity (effect directed analysis). Despite its popularity a standard procedure has not been elaborated so far causing difficulties in comparing results obtained in different laboratories. Thus the aim of the presented research was an approach to develop a standardized procedure for assessing free radical scavenging properties of plant polyphenols. It was observed that specifically positive adsorbent (silica gel) strengthened the observed result of radical-antioxidant reaction, while polar bonded stationary phase CN-silica weakened it. Based on the observed results it was concluded that the TLC-DPPH(•) assay should be preferably performed on the surface of non-specific adsorbents (e.g.: RP-18) with the use of n-hexane for DPPH(•) dissolution. It is also proposed to document the results every 5 min after staining, as they change in time.

Case-control study of intracranial tumors among employees at a petrochemical research facility.

This case-control study evaluated the relation between potential exposure to chemical and physical agents and the occurrence of intracranial tumors among employees at a petrochemical research facility. Cases were employees with glioma (n = 6) or benign intracranial tumors (n = 6). Controls (n = 119) were individually matched to cases on gender and birth year, and they were alive and did not have an intracranial tumor at the case's diagnosis date. Exposure information came from interviews with subjects or surrogates and from corporate records on agents used in research projects. Analyses computed matched odds ratios (ORs) and corresponding 95% confidence intervals (CIs) for self-reported exposure to 15 agents and project-based estimates of exposure to 29 agents. For gliomas, the OR was elevated for self-reported exposure to ionizing radiation (OR, 15.7; CI, 1.4 to 179.4), n-hexane (OR, infinity; CI, 1.4 to infinity), organometallics (OR, 9.4; CI, 1.5 to 59.7), and amines other than nitrosamines (OR, 6.0; CI, 1.0 to 35.7). The OR also was elevated for project-based potential use of ionizing radiation (OR, 9.6; CI, 1.7 to 55.2) and for potential use of n-hexane lasting at least 4 years (OR, 16.2; CI, 1.1 to 227.6). For benign intracranial tumors, the OR was elevated only for self-reported exposure to ionizing radiation (OR, 5.4; CI, 1.7 to 43.1) and other amines (OR, 5.2; CI, 0.9 to 29.5). Occupational exposure may have contributed to the glioma excess, but the specific causal agents remain unknown. The study indicated that benign intracranial tumors were unlikely to be work-related.

Mass spectrometric characterization of polyhedral oligosilsesquioxanes and heterosilsesquioxanes

Silsesquioxanes constitute a diverse range of Si-O frameworks with a wide variety of intriguing possibilities as models for catalysis. These topologically interesting molecules are formed by the hydrolytic condensation of trifunctional organosilanes. Heterosilsesquioxanes are formally derived by substitution of a main-group, transition-metal, or f-element atom for one or more Si atoms in a silsesquioxane. A number of silsesquioxanes and their metal-containing derivatives, metallasilsesquioxanes (Si-O-M), were characterized using atmospheric pressure chemical ionization (APCI) and turbo ion-spray (TISP) mass spectrometry. The use of n-hexane or n-hexane/ethanol (90:10, v/v) allowed the techniques to be utilized to characterize a large number of complexes. In some cases addition of trace amounts of ammonium acetate, sodium chloride, or sodium acetate to the ethanolic portion of the solvent allowed the detection of [M + NH4]+ or [M + Na]+ ions. Copyright © 1999 John Wiley & Sons, Ltd.

A Microbial Sensor Based on Pseudomonas putida for Phenol, Benzoic Acid and Their Monochlorinated Derivatives Which Can Be Used in Water and n-Hexane

A microbial sensor for the detection of phenol, benzoic acid and their monochlorinated derivatives was developed. Detection was based on oxygen consumption in relation to analyte oxidation. To this end, induced cells of Pseudomonas putida DSM 548 were immobilized on Clark-type oxygen electrodes. The sensors were linear in their current signal up to a phenol concentration of 50 μM and had a detection limit of 0.1μM. Monochlorophenols could be detected at a concentration of 8 μM with a strong dependency on the growth substrate used for cell cultivation. Further variations in cell induction protocols resulted in microbial sensors with different selectivities. Using sensors equipped with cells grown on benzoic acid, this substance was detectable in the range of 2–16 μM, whereas 3- and 4-chlorobenzoic acid were detected at concentrations of 7 μM. The sensors were found to be stable under storage at 4°C for over 21 days. The use of n-hexane as a solvent increased the sensitivity for phenol five fold, the measurement frequency six fold, and operational stability was 7 hrs. Preliminary experiments using screen-printed thick film electrodes as disposable oxygen sensors resulted in a wider detection range from 6.3 μM to 90 μM phenol.

A study of low hydrocarbon content gas mixtures for streamer tubes

Several gas mixtures have been tested in order to reduce the hydrocarbon content for the operation of 1 × 1 cm 2 streamer tubes for the Aleph hadron calorimeter. It has been found that the use of n-hexane in place of n-pentane allows a safer operation of streamer tubes at reduced fractions of hydrocarbon. The use of nonflammable gas mixtures is discussed.

The use of n-hexane in the gas mixture for streamer tubes

We have investigated the use of n-hexane as a quencher in the gas mixtures for streamer tubes. We discuss the advantages of this choice from the point of view of safety.

An automated calorimeter for the measurement of isobaric expansivities and of isothermal compressibilities of liquids by scanning pressure from 0.1 to 400 MPa at temperatures between 303 and 503 K

A pressure-scanning calorimeter operating in the pressure range from 0.1 to 400 MPa at temperatures from 303 to 503 K is described. Information collection from, and control of, the calorimeter is done with a computer and a stepping motor. The calorimeter was tested by determining the isobaric expansivity of n-hexane over nearly the entire range of accessible pressures and temperatures. Expansivities for a mixture of n-hexane and hexane isomers are also presented. The sample cell and pressurizing equipment associated with the calorimeter can also be used to determine the compressibilities of liquids near room temperature. A method for calibration of the system for this purpose is demonstrated by use of n-hexane as a calibrating fluid.

Preparative GPC in fundamental polymer synthesis

A simple efficient preparative gel permeation chromatography assembly (prep GPC) has been built using largely commercially available components, (i.e., pump, columns, all glass solvent recirculating system) and its usefulness in fundamental polymer synthesis was demonstrated. The operating cost of prep GPC has been reduced and the safety much improved by the use of n-hexane as the mobile phase. Rapid one-recycle narrow fractionation (Mw/Mn=1.1–1.2) and purification of relatively large quantities (up to 20 g/loading) of polyisobutylene (PIB) samples is described. Operating parameters and efficiency are illustrated by examples. By the use of this equipment sufficient quantities of narrow MWD polyhydrocarbons can be conveniently and rapidly obtained for meaningful structure/property research.

Reasons for the High Proportion of Pheophytin in Edible Plant Oils

To reduce the pheopytin (Phy) level in oils, it is necessary to understand the reasons of the high proportion of Phy in refined edible oils. In this investigation, the compositional changes in chlorophyll (Chl) and Phy during extraction and some refining processes were evaluted by photofluorometric analysis.The composition of Chl pigments in crude oils was examined when Canola seed oil was extracted with 6 kinds of organic solvents. The proportion of Phy was found to be the highest (97%) in oil extracted with n-hexane, but 38% in hexane-ethanol (3 : 1) extracts, and 13 % in chloroform-methanol (2 : 1) extracts. Especially, when the residue following extraction with n-hexane was further extracted with chloroform-methanol (2 : 1), the proportion was only 3%. From these results, it is concluded that the use of n-hexane as a solvent reduces the extraction of Chl from oil seeds.Next, Canola seed oil was extracted with n-hexane for different extraction times and at different temperatures. Moreover, the changes in Chl during acid treatment of the crude oil were investigated in a model system. A portion of the Chl was converted into Phy during heat or acid treatments. However, in our previous study, a relatively constant compositional ratio between Chl pigments was observed in rapeseed oils throughout the process of mass production. The conversion of Chl to Phy during heat or acid treatment in model experiments may thus be assumed insignificant in practical refining for mass production.

Utilization of n-Alkanes by Cladosporium resinae

Four different isolates of Cladosporium resinae from Australian soils were tested for their ability to utilize liquid n-alkanes ranging from n-hexane to n-octadecane under standard conditions. The isolates were unable to make use of n-hexane, n-heptane, and n-octane for growth. In fact, these hydrocarbons, particularly n-hexane, exerted an inhibitory effect on spore germination and mycelial growth. All higher n-alkanes from n-nonane to n-octadecane were assimilated by the fungus, although only limited growth occurred on n-nonane and n-decane. The long chain n-alkanes (C(14) to C(18)) supported good growth of all isolates, but there was no obvious correlation between cell yields and chain lengths of these n-alkanes. Variation in growth responses to individual n-alkane among the different isolates was also observed. The cause of this variation is unknown.

ノルマルヘキサンの末梢神経毒性に関する電気生理学的研究

n-Hexane (hexyl hydride, caproyl hydride) is an ingredient of petroleum, and volatile. It is widely used as a safe solvent in the industrial fields. Rcently 17 cases of peripheral neuropathy caused by industrial use of n-Hexane have been reported in Japan. In these cases, n-Hexane vapour concentrations in the work rooms were 500 to 1, 000 p.p.m. and local concentrations near the sources were 1, 000 to 2, 000 p.p.m.. The aim of this experiment was to study the neurotoxicity of n-Hexane through animal experiments, and to confirm the critical level of the vapour concentration of n-Hexane which just causes these pathological states. The animals used in this experiment were SMA strain male mice, and were separated into 6 groups of 10 mice each. Each gorup of animals was housed in a gas-chamber. These groups were kept in n-Hexane vapour for 24 hours a day, 6 days a week, and for one year. The vapour concentrations of n-Hexane in these chambers were as follows; (the values outside the parenthesis indicate the planned concentrations and those inside indicate the mean vapour concentrations which were measured throughout the total experiment period of one year.) group 1:100 (98.6) p.p.m., group 2:250 (272.0) p.p.m., group 3:500 (551.9) p.p.m., group 4:1, 000 (1030.1) p.p.m., group 5:2, 000 (1903.6) p.p.m., and group 6: the control. The examinations were made on the distal part of the lower extremities of the animals. The examinations used were electromyography, stregthdurations curves, electrical reaction time, and flexor / extensor chronaxy ratio. Other investigations performed were that on gait posture and measurement of the grade of muscle atrophy of the lower extremities. Histological examinations of the distal muscles of the lower extremities were performed in some of the animals. The results of these examinations were as follows; 1) Electromyography: Complex N.M.U. voltages were observed frequently in NO. 3, 4, and NO. 5 groups and less frequently in NO.2 groups. Fibrillation voltages were observed in NO. 4 and NO 5 groups. Low voltages were rarely observed. 2) Strength-duration curves: in most of the animals of NO.4 and NO.5 groups the curves showed type. The curves showed mixed denervation (incomplete denervation) types in most of the animals of NO. 2 and 3 groups an in some of the NO. 4 group. 3) Electrical reaction time: it was clearly longer in NO. 4 and 5 groups. 4) Flexor/extensor chronaxy ratio: it was significantly lower than 1.0 in NO. 4 and 5 groups, while it was near 2.0 in the control group. 5) Gait posture: in NO.4 and 5 groups animals showed abnormal gait posture which might be understood as the result of muscle weakness caused by n-Hexane. 6) Muscle atrophy: decreased muscle volumes of the lower extremities were seen more or less than in the animals of NO.4 and 5 groups. 7) Histological examinations: histological specimens of distal muscles of the lower extremities of NO.5 group animals showed neural muscular atrophy. The diagnosis was made in each animal according to the results of these examinations. The results of the examinations mentioned above might lead to a conclusion that peripheral nerve disorders of the animals were brought about through one year exposure of n-Hexane and that the effective toxic concentration of n-Hexane was 250 p.p.m. or more. Far more study might be necessary to discuss about the effects of n-Hexane on the central nervous system including the spinal cord. In view of the fact that man is several times more sensitive concerning the toxicological nervous changes than the mice, which were used in these experimental studies, the results of this sutdy might lead to the conclusion that the vapour concentration of n-Hexane in the work room should be 100 p.p.m. or less. The electrophysiological examinations mentioned above might be interesting methods to investigate the biological effects of industrial organic solvents.

Chemistry of Positive Ions. III. The Radiation Chemistry of Solidn-Hexane at 77°K

The mechanism of the chemical effects of ionizing radiation on solid straight-chain saturated aliphatic hydrocarbons such as polyethylene was studied by use of n-hexane. This hydrocarbon was short enough to allow analysis of the cross-link C12 products and of the hexenes formed. It was thought to be long enough to serve as a legitimate substitute for polyethylene. In any case, the yields of H2, olefines, and cross linkages were very similar in the two systems and we believe the mechanistic implications found here for solid n-hexane at 77°K should apply even to polyethylene.The results indicate: (a) the active species is the original ion radical produced by the ionizing radiation (Co60 gammas); (b) the ion radical reacts before relaxing to redistribute the positive charge or to isomerize in any way, and the products show that there are three primary ions formed corresponding to the first, second, and third carbon atoms in the chain; (c) the ion radical reacts with nearest neighboring groups to bond and release H2, thus forming olefines by reaction with neighboring C atoms in the same molecule four times out of five, but reacting with neighboring chains to form C12 dimers one time out of five; the dimers being only the five hydrocarbons possible by close-neighbor interaction: the 1,1 interaction being n-dodecane; the 1,2 being 5-methylundecane; the 2,2 being 5,6-dimethyldecane; the 2,3 being 4-ethyl-5-methylnonane; the 3,3 being 4,5-diethyloctane and no others; (d) the principal mechanism of the fast interaction of the primary ion is the direct elimination of H2 and formation of a bond due to charge exchange attraction between the primary ion and the neutral group with which it interacts; (e) the second most important mechanism is the abstraction of H to form the electronically saturated analog of CH5+ which when neutralized eliminates H2 and leaves a free radical to combine with the neighboring free radical left by the H abstraction; (f) free radicals seem to play a minor role in the solid hydrocarbon, n-hexane.