Acid In N-heptane Research Articles

Catalytic properties of the platinum catalyst supported on alumina modified by oxalic acid in n-heptane reforming

Structural modification of alumina was carried out by the decomposition of the products of the reaction of aluminum hydroxide with the organic acid used simultaneously as a peptizer and a “burnable” additive. The modification changes the acidity of the support surface and induces the formation of pentacoordinate Al3+ cations interacting with platinum, which increases the fraction of platinum atoms with electron deficiency. The alumina-platinum catalyst based on the support treated with oxalic acid shows an enhanced selectivity to aromatization in n-heptane reforming.

Characterization of an immobilized recombinant lipase from Rhizopus oryzae: Synthesis of ethyl-oleate

Abstract In recent years there has been a surge of interest in using lipases to catalyze the synthesis of biodiesel, as the biocatalytic route has several advantages over the chemical route. The principal objective of this work was to study the synthesis of ethyl-oleate, as a model ester of biodiesel, using a recombinant lipase of Rhizopus oryzae (rROL) that had been expressed in Pichia pastoris. This lipase was immobilized on the hydrophobic support Accurel MP 1000. Best results were obtained with a protein to support ratio of 15 mg g−1, giving a p-nitrophenyl palmitate-hydrolyzing activity in n-heptane of 220 U g−1. This immobilized enzyme (I-rROL) showed good stability in n-heptane, with a residual activity of 77% after 24 h incubation at 40 °C. The best result for the synthesis of ethyl-oleate, in terms of the specific productivity of esters (i.e. per mass of catalyst preparation), was 10,664 mg h−1 g−1. This result corresponded to 79% conversion of the fatty acid in 30 min and was obtained with 560 mM oleic acid in n-heptane, with a molar ratio of ethanol to oleic acid of 1.4:1, with the ethanol being added in 6 equal aliquots at 5-min intervals. This reaction was done with 30 mg mL−1 of I-rROL at 30 °C. The high productivities obtained in the presence of n-heptane indicate that the recombinant lipase of R. oryzae has a good potential for application in biocatalytic processes undertaken in organic media, however, it appears to be susceptible to denaturation by the alcohol.

Kinetic resolution of ( R, S)-1,2- O-isopropylideneglycerol by esterification with dry mycelia of moulds

The esterification of ( R, S)-1,2- O-isopropylideneglycerol catalysed by dry mycelia of different moulds in organic solvent was studied. Dry mycelium of Rhizopus oryzae CBS 112.07 and Aspergillus oryzae MIM gave the ( R)-ester with moderate optical purity; the kinetic data of the esterification with butyric acid in n-heptane showed an enantiomeric ratio of 3.4 with Rhizopus oryzae and 8.0 with Aspergillus oryzae. The esterification catalysed by Aspergillus oryzae was performed on larger scale (operative volume 2.3 l) allowing for the production of 2.3 g l −1 of ( R)-IPG butyrate with an e.e. = 56% and a molar conversion of 52%. The enantiomerically enriched ester was hydrolysed with thermally-treated cells of Bacillus coagulans: the ( S)-ester was obtained as enantiomerically pure molecule, while the alcohol was recovered with e.e. = 90%.

Group Contribution Analysis of Xenon NMR Solvent Shifts

129Xe gas-to-solution NMR chemical shifts for xenon dissolved in pure n-alkanes, n-alkyl alcohols, n-alkyl carboxylic acids, di-n-alkyl ketones, and cycloalkanes and in solutions of lauric acid in n-heptane are reported. The medium effect corrected for solvent density is found to be linearly dependent on the number of carbon atoms except for the shortest members of the series of linear solvents. The same slope is observed for all the linear solvents; the slope for the cycloalkanes is significantly different. These results are interpreted on the basis of a group contribution analysis. The relative contribution of methyl and methylene groups in linear solvents is found to be in very good agreement with the relative Xe−CH3 and Xe−CH2 dispersive interaction energies. The 129Xe chemical shifts for solutions of lauric acid in n-heptane calculated from the group contributions are in excellent agreement with the experimental values. The deshielding effect of the methylene group in cycloalkanes and the 129Xe chemical shift measured in the shortest members of the linear series of solvent are discussed in terms of intermolecular shielding functions and distributions of groups in the solvation shell of the Xe atom.

Characterization of a Single Sample by Combining Thermodynamic and Spectroscopic Information in Spectral Analysis

We have previously shown that chemical equilibria can be characterized spectroscopically, even when the component spectral responses are unknown and overlapping, by exploiting appropriate thermodynamic relations (Kubista, M.; Sjoback, R.; Albinsson, B. Anal. Chem. 1993, 65, 994−998). Application of this strategy requires sets of samples that differ in a physical property, such as pH or total concentration. In this work, we show that a similar strategy can be applied to characterize a single sample. Utilizing the van't Hoff relation, which describes the dependence of the equilibrium constant on temperature, we show that spectra recorded at different temperatures can be deconvoluted into contributions from the individual components. To illustrate the approach, we characterize two monomer/dimer equilibria, thiazole orange in aqueous solution and benzoic acid in n-heptane, by studying the effect of temperature on the absorption spectrum. We determine the spectral responses of the monomer and dimer species, th...

Squarete complexes of uranyl ions in aqueous solution

The stability constants of UO 2 2+ -squarate complexes are measured at ionic strengths of 0.05M, 0.06M, 0.075M, 0.09M, 0.1M (squaric acid-perchloric acid) using a solvent extraction method at a pH of 1.1 and a temperature of 25 °C. The extractant used is dinonylnaphthalenesulfonic acid in n-heptane. The aqueous phase was made of a mixture of squaric and perchloric acid and233U radio tracer. The stability constants of squarate complexes of UO 2 2+ is seen to decrease linearly with the square root of the ionic strength.

The kinetics of zinc extraction in the di(2-ethylhexyl) phosphoric acid, n-heptane-Zn(ClO 4) 2, HClO 4, H 2O system using the rotating diffusion cell

The kinetics of zinc extraction from perchlorate solutions by di(2-ethylhexyl) phosphoric acid in n-heptane were measured using the rotating diffusion cell technique. The extraction of zinc is controlled by the mass transfer of reactants (Zn 2+ and D2EHPA) to the interface: bulk pH has little effect. It appears that the chemical reaction rate is so fast that it has a negligible effect on the overall extraction rate. A mass transfer mathematical model was developed which is adequate for predicting the extraction rate under variable conditions of zinc concentration, D2EHPA concentration and pH. The effect of using a partially loaded organic extractant was investigated and the system was found to be mass transfer controlled. A second mathematical model was developed which predicts that the speciation of organic-complexed zinc changes with increasing preload and, at high loadings, the direction of ZnL 2·HL and ZnL 2·(HL) 2 flux reverses, with these species providing extractant to the interface. At very high loadings, ZnL 2·HL provides almost all the extractant to the interface. Experimental studies of the effect of temperature on the rate of zinc extraction resulted in calculation of an activation energy of 12.4 kJ/mol, which is consistent with a diffusion-controlled mechanism. The extraction rate decreases significantly for a very small filter pore size, while there appears to be little or no effect for larger filter pore sizes. It was therefore concluded that, for the filter pore size used in this study, the filter pores do not pose an additional resistance to mass transfer.

Determination of equilibrium constants by chemometric analysis of spectroscopic data

We describe a chemometric method to determine equilibrium constants with high accuracy from spectroscopic titrations. Knowledge of component spectra is not required for the analysis, and titrations can be analyzed even when the titration end points are not reached. In fact, the component spectra are determined in the analysis. The analysis is based on a decomposition of the recorded spectra into a product of target and projection matrices using NIPALS. The matrices are then rotated to give the correct concentrations and spectral profiles of the components utilizing the functional form of the equilibrium expression. The output of the analysis is the equilibrium constant and the component spectral profiles. The analysis is highly accurate and can be performed on a standard personal computer. As examples, we determine the protolytic constant for the equilibrium between the anionic and dianionic forms of fluorescein in aqueous solution and the dimerization constant of benzoic acid in n-heptane.

Extraction mechanism of rare earth metals in the presence of diethylenetriaminepentaacetic acid in aqueous phase.

The extraction rates of Er3+ and Y3+ from an aqueous phase containing diethylenetriaminepentaacetic acid (DTPA) to an organic phase containing di(2,4,4-trimethylpentyl) phosphinic acid in n-heptane were experimentally determined with both a transfer cell having a constant interface area and an agitated vessel in which organic phase was dispersed finely. The selectivity obtained was about 5.5, which was much larger than that by the usual solvent extraction: The selectivities for the various cases were studied in detail. The extraction rates and selectivity were quantitatively analyzed by taking account of the dissociation reactions of the rare earth metal DTPA complexes in the aqueous stagnant layer.

Effect of pressure on the dimerization of benzoic acid in n-heptane

Ultraviolet absorption spectra of benzoic acid in n-heptane were measured at 25°C and up to 640 MPa. The reaction volume for the cyclic dimerization of benzoic acid was estimated as 0.4 ±0.9 cm 3 mol −1 from the pressure dependence of the dimerization constant. This is much more positive than those for noncylic hydrogen-bond formations which are from −3 to −6 cm 3 mol −1. It is ascribed to a compensation between a reduction in the volume accompanying the hydrogen-bond formation and an increase accompanying the cyclization. These two contributions to the reaction volume are estimated quantitatively.

5f state interaction with inner coordination sphere ligands: Es 3+ ion fluorescence in aqueous and organic phases

The interaction between the 5f electron states of the Es 3+ ion and coordinated ligands in solution was probed using laser-induced fluorescence. The aquo-Es 3+ ion was observed to fluoresce from its first excited J = 5 state in a broad band peaking at 9260 cm −1. The observed fluorescence lifetimes were 1.05 us and 2.78 μs in H 2O and D 2O (minimum isotopic purity, 99 at.% D) respectively. The non-radiative decay rates derived from the lifetime data are compared with previously reported data for hydrated Cm 3+, Sm 3+, Eu 3+, Tb 3+ and Dy 3+ ions. The 5f actinide states exhibit substantially greater non-radiative decay rates than do lanthanide 4f states with a similar energy gap. This provides evidence that actinide 5f electrons interact more strongly with their inner coordination sphere than do lanthanide ion 4f electrons. The fluorescence lifetime of Es 3+ complexed with 1 formal (1g formula weight (1 mol) dissolved in sufficient solvent to give 1 dm 3+ of solution) di(2-ethylhexyl)orthophosphoric acid in n-heptane was 2.34 μs.

Empirical model for the extraction system YCl 3ErCl 3HClH 2ODI-(2-ethylhexyl)phosphoric acid—n-heptane

Equilibrium data were obtained for the extraction of the binary rare earth mixture yttrium chloride-erbium chloride from 2 kmol/m 3 HClH 2O solutions by 1 kmol/m 3 di(2-ethylhexyl)phosphoric acid in n-heptane. Total rare earth concentration in the aqueous phase was 0.5 kmol/m 3. It was found that yttrium concentrations in the organic phase exhibit negative deviations whereas erbium concentrations exhibit positive deviations from ideality. Empirical correlations for predicting these deviations were developed. The separation factor was calculated.

ChemInform Abstract: THE EXTRACTION OF SELECTED M(III) METALS BY BIS 2‐ETHYLHEXYL PHOSPHORIC ACID IN N‐HEPTANE

Chemischer InformationsdienstVolume 8, Issue 4 Physical Inorganic Chemistry ChemInform Abstract: THE EXTRACTION OF SELECTED M(III) METALS BY BIS 2-ETHYLHEXYL PHOSPHORIC ACID IN N-HEPTANE G. W. MASON, G. W. MASONSearch for more papers by this authorD. N. METTA, D. N. METTASearch for more papers by this authorD. F. PEPPARD, D. F. PEPPARDSearch for more papers by this author G. W. MASON, G. W. MASONSearch for more papers by this authorD. N. METTA, D. N. METTASearch for more papers by this authorD. F. PEPPARD, D. F. PEPPARDSearch for more papers by this author First published: January 25, 1977 https://doi.org/10.1002/chin.197704011Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article. Volume8, Issue4January 25, 1977 RelatedInformation

The extraction of selected M(III) metals by bis 2-ethylhexyl phosphoric acid in n-heptane

The extraction of Y 3+, Pm 3+, Eu 3+, Tm 3+, Lu 3+, Am 3+ and Cm 3+ from an aqueous chloride phase into a solution of (2-C 2H 5·C 6H 12O) 2PO(OH), HDEHP, in n-heptane has been studied as a function of the concentration of extractant in the organic phase and of hydrogen ion in the aqueous phase. From these data the stoichiometries of extraction have been deduced as: M A 3++2.5(HY) 2 o ⇌MY(HY 2) 2 o +3H A + where the subscripts A and O refer, respectively, to mutually equilibrated aqueous and organic phases. (The formulation of extracted entities is based solely upon established ratios and is in no sense to be interpreted in terms of established structure.) Corresponding to the stoichiometries, values of K, F and [H +] obtained from the hydrogen ion dependency plots were inserted in the equation: K= K s F a /[H +] b to obtain values of K s . ( K is the observed distribution ratio, F the equilibrium concentration of HDEHP in the organic phase, [H +] the equilibrium concentration of hydrogen ion in the aqueous phase, and a and b the respective extractant and hydrogen ion dependencies.) The equation is applied specifically to a system embodying 1.0F (NaCl + HCl) at 22±2°C. The K s ( n-neptane) value is higher than the K s (benzene) value for each of the cations studied. Comparisons with extraction systems employing ( n-C 8H 17O) 2PO(OH) and [C 4H 9C(CH 3) 2CH 2O] 2PO(OH), respectively symbolized as HDOP and HDNOP, are made.

Distribution equilibria of SmCl 3EuCl 3HCl and EuCl 3GdCl 3HCl systems with 1M di(2-ethylhexyl) phosphoric acid in n-heptane

Distribution equilibrium data have been obtained for the systems LnCl 3HClH 2O1M D2EHPA in n-heptane ( Ln: Sm, Eu and Gd). The equilibrium curves were described using equilibrium acid concentration as a parameter. It was shown that the distribution ratios of the lanthanides were proportional to C H X 2.2 or C H X 2.5 (C H X represents the concentration of the extractant) according to the estimated value for the ratio of the extractant to the metal in the extracted species. Equilibrium data for the systems involving SmCl 3EuCl 3 and EuCl 3GdCl 3 have been obtained. In these systems the concentrations of individual lanthanides in the organic phase deviated from the expected values based on the assumption that the distribution ratio of each lanthanide was not varied by adding the other lanthanides. The concentrations of the heavier lanthanides, Eu in SmEu system and Gd in EuGd system, in the organic phase were higher than the expected values, and those of the lighter lanthanides were lower than the expected values. These behaviors of the lanthanides were explained in terms of the change of the concentrations of the hydrogen ion and the extractant.

A solvent-extraction method for the determination of manganese-54 in sea water

A solvent-extraction procedure for the determination of manganese-54 in sea water is described. The water (1 l) is buffered to pH 3.8, and extracted with di(2-ethylhexyl)phosphoric acid in n-heptane. The manganese-54 with carrier is stripped from the organic phase, and eventually precipitated as the dioxide; the precipitate is dissolved in hydrochloric acid and counted in a scintillation counter. Chemical recovery is determined colorimetrically. Samples spiked with manganese-54 showed quantitative recovery from 1 l of sea water with a typical recovery of 70–75% of carrier. The method is applicable to sea water containing many other ions, and decontamination factors for a wide range of radionuclides are reported. The limit of detection is ca. 10 -8 μCi ml -1.

Acidic organophosphorus extractants extraction of molybdenum(VI) by di(2-ethylhexyl) phosphoric acid from weakly acid solutions

The distribution of molybdenum(VI) between solutions of di(2-ethylhexyl) phosphoric acid in n-heptane and other diluents and weakly acid perchlorate and nitrate solutions has been studied as a function of the hydrogen ion, extractant, nitrate and perchlorate concentrations and of the nature of the diluent. The extraction mechanism and the composition of extracted complexes of Mo(VI) are discussed.

Distribution Equilibria of PrCl3-NdCl3-SmCl3-HCl System with 1.0MDi(2-Ethylhexyl)Phosphoric Acid inn-Heptane

The presence of one lanthanide has been found to inhibit or promote the extraction of the other lanthanide present in the two salt extraction systems of PrCl3-SmCl3-HCl and NdCl3-SmCl3-HCl, with 1.0 M di (2-ethylhexyl) phosphoric acid in n-heptane. This mutual interference effect has been quantitatively expressed by means of a new parameter. The three salt system of PrCl3-NdCl3-SmCl3-HCl can be reduced virtually to a “two salt” system of (Pr + Nd)Cl3-SmCl3-HCl and a rough estimation of distribution equilibrium of this system is possible with the use of the above-mentioned parameters.

Separation factor for the extraction systems, YCl 3-ErCl 3-HCl, YCl 3-HoCl 3-HCl and some lanthanide chlorides-hydrochloric acid with 1 M di(2-ethylhexyl) phosphoric acid in n-heptane

The distribution coefficients of Y, Er and Ho and the separation factors of some lanthanides with respect to Y are given at macro-concentrations when the lanthanides are extracted by 1·0 M di(2-ethylhexyl) phosphoric acid (D2EHPA) in n-heptane from their chloride solutions. It has been shows that the separation of Er and Ho from Y is difficult with D2EHPA. However, the values of the separation factors of Sm, Gd, Dy and Yb to Y indicate that removal of these lanthanides from Y is rather easy.

Application of solvent extraction to the refining of precious metals: I. Purification of rhodium

A procedure for purification of rhodium based on its extraction from dilute hydrochloric acid solution by dinonylnaphthalenesulphonic acid in n-heptane has been developed. Separation of the element from iridium, platinum, palladium and silver has been shown to be essentially complete. A scaled-up version of the procedure could be incorporated with advantage into the process for the commercial refining of rhodium.