Hexane

About: Hexane is a research topic. Over the lifetime, 3759 publications have been published within this topic receiving 57996 citations. The topic is also known as: CH3-[CH2]4-CH3 & hexyl hydride.

Electron spectroscopy of sulfated zirconia, its activity in n-hexane conversion and possible reasons of its deactivation

Abstract: Sulfated zirconia catalysts were prepared and characterized by X-ray photoelectron spectroscopy taken in the dried state (fresh) and after calcination at 900 K (calc.). A maximum activity was observed as a function of the calcination temperature. The Zr 3d region showed that any Zr hydroxide in the dried catalyst transformed into zirconium oxide upon calcination. The O 1s peak could be fitted by two components corresponding to ZrO 2 and sulfate, respectively. Sulfur was present as sulfate. Both catalysts showed activity in n -hexane conversion (including isomerization) between 300 and 473 K. The activity of the calcined catalyst was much higher. The main products were isopentane and isobutane, along with 2-methyl- and 3-methylpentane. The activity was not stable and only a limited amount of n -hexane transformed before final deactivation. This observation pointed to a limited amount of active sites able to start the reaction. The activity could be fully regenerated by oxygen treatment. Thus, the “oxidative” start of the reaction [ A. Ghenciu, D. Farcasiu, Catal. Lett. 44 (1997) 29] may have also played a role apart from those on strong acid sites. Deactivation may have been due to a partial reduction of sulfate groups rather than to carbon accumulation, as shown also by the minor amounts of S 4+ detected by XPS. Parallel isomerization and splitting of hexane into two C 3 units may occur, followed by the formation of surface C 9 units, the latter being intermediate of larger fragments.

Resonant-surface second-harmonic generation studies of phenol derivatives at air/water and hexane/water interfaces

Abstract: Resonant-surface second-harmonic generation and surface tension measurements have been used to study the adsorption of p-nitrophenol, phenol and p-propylphenol at the air/water and hexane/water interfaces at full monolayer coverage. The determining forces defining the angle of orientation of the moieties are the solute–solvent interactions at both interfaces. In particular, we observed the screening effect of the hexane phase on the solute–water interactions. Surface tension measurements performed on these interfaces showed that the number of molecules per unit surface at full coverage follows from the angle of orientation. From a wavelength analysis of the SH response of the monolayers, we are led to the conclusion that partial hydration of the aromatic rings of phenol and p-propylphenol occurs at both the air/water and the hexane/water interfaces, whereas p-nitrophenol remains largely within the water phase at both interfaces.

Experimental investigation of the low temperature oxidation of the five isomers of hexane.

Abstract: The low-temperature oxidation of the five hexane isomers (n-hexane, 2-methyl-pentane, 3-methyl-pentane, 2,2-dimethylbutane, and 2,3-dimethylbutane) was studied in a jet-stirred reactor (JSR) at atmospheric pressure under stoichiometric conditions between 550 and 1000 K. The evolution of reactant and product mole fraction profiles were recorded as a function of the temperature using two analytical methods: gas chromatography and synchrotron vacuum ultraviolet photoionization mass spectrometry (SVUV-PIMS). Experimental data obtained with both methods were in good agreement for the five fuels. These data were used to compare the reactivity and the nature of the reaction products and their distribution. At low temperature (below 800 K), n-hexane was the most reactive isomer. The two methyl-pentane isomers have about the same reactivity, which was lower than that of n-hexane. 2,2-Dimethylbutane was less reactive than the two methyl-pentane isomers, and 2,3-dimethylbutane was the least reactive isomer. These ob...

Determination of triazole pesticide residues in edible oils using air-assisted liquid-liquid microextraction followed by gas chromatography with flame ionization detection.

Abstract: In the present study, a rapid, simple, and highly efficient sample preparation method based on air-assisted liquid-liquid microextraction followed by gas chromatography with flame ionization detection was developed for the extraction, preconcentration, and determination of five triazole pesticides (penconazole, hexaconazole, diniconazole, tebuconazole, and triticonazole) in edible oils. Initially, the oil samples were diluted with hexane and a few microliter of a less soluble organic solvent (extraction solvent) in hexane was added. To form fine and dispersed extraction solvent droplets, the mixture of oil sample solution and extraction solvent is repeatedly aspirated and dispersed with a syringe. Under the optimum extraction conditions, the method showed low limits of detection and quantification between 2.2-6.1 and 7.3-20 μg/L, respectively. Enrichment factors and extraction recoveries were in the ranges of 71-96 and 71-96%, respectively. The relative standard deviations for the extraction of 100 and 250 μg/L of each pesticide were less than 5% for intraday (n = 6) and interday (n = 3) precisions. Finally edible oil samples were successfully analyzed using the proposed method, and hexaconazole was found in grape seed oil.

Phase Equilibria of the Azeotropic Mixture Hexane + Ethyl Acetate with Ionic Liquids at 298.15 K

Abstract: This work reports the results of a study on the use of the two ionic liquids as an extraction solvent in the separation of the azeotropic mixture of hexane with ethyl acetate. Experimental densities, speeds of sound, and refractive indices of the binary mixtures of ethyl acetate + hexane or + 1-hexyl-3-methylimidazolium hexafluorophosphate (HMIM PF6) were determined from (293.15 to 303.15) K, since they are necessary to determine liquid-liquid equilibria. Excess molar volumes, changes of refractive index on mixing, and deviations in isentropic compressibility for the above systems were calculated. Liquid-liquid equilibria (LLE) were determined for the ternary systems hexane + ethyl acetate + HMIM PF6 or 1-octyl-3methylimidazolium hexafluorophosphate (OMIM PF6) at 298.15 K and atmospheric pressure. The values of selectivity and distribution ratio were derived from the tie-line data. Experimental liquid-liquid equilibria data were correlated with the NRTL and UNIQUAC equations. These equations were verified to accurately correlate the experimental data.