Higher alcohol and paraffin synthesis on cobalt based catalysts: Comparison of mechanistic aspects

Syngas reaction mechanism studies on cobalt based catalysts suggested that the CO dissociation step and the (alcohol and/or hydrocarbon) chain growth can be well mimicked by CO disproportionation and temperature programmed desorption (TPD) of acetaldehyde. Correlation between C₂₊ hydrocarbon selectivity and CO disproportionation on the one hand, C₂₊ alcohol selectivity and TPD after acetaldehyde adsorption on the other hand could be evidenced.     

醇/烃系统的分子热力学(Ⅱ)1-2-4模型应用于汽液平衡

建立了1个醇/烃系统的分子热力学模型,用红外光谱法获得的醇的标准缔合常数应用于汽液平衡,能够很好地区分醇类缔合物质的化学作用和物理作用,所得化学参数和物理参数具有明确的物理意义.计算表明:本文提出的1-2-4缔合模型在应用1个二元可调参数的情况下能较好地描述含醇系统的汽液平衡性质.即使对于不同链长的正构醇采用统一的缔合常数,同样可获得较好的结果.     

Cu(II) Binding Increases the Soluble Toxicity of Amyloidogenic Light Chains

Light chain amyloidosis (AL) is caused by the aberrant overproduction of immunoglobulin light chains (LCs). The resulting abnormally high LC concentrations in blood lead to deposit formation in the heart and other target organs. Organ damage is caused not only by the accumulation of bulky amyloid deposits, but extensive clinical data indicate that circulating soluble LCs also exert cardiotoxic effects. The nematode C. elegans has been validated to recapitulate LC soluble toxicity in vivo, and in such a model a role for copper ions in increasing LC soluble toxicity has been reported. Here, we applied microscale thermophoresis, isothermal calorimetry and thermal melting to demonstrate the specific binding of Cu²⁺ to the variable domain of amyloidogenic H7 with a sub-micromolar affinity. Histidine residues present in the LC sequence are not involved in the binding, and yet their mutation to Ala reduces the soluble toxicity of H7. Copper ions bind to and destabilize the variable domains and induce a limited stabilization in this domain. In summary, the data reported here, elucidate the biochemical bases of the Cu²⁺-induced toxicity; moreover, they also show that copper binding is just one of the several biochemical traits contributing to LC soluble in vivo toxicity.     

二元液液系统界面张力

采用悬滴技术分别测量了正己烷-水、正庚烷-水、正辛烷-水、正壬烷-水和正己醇-水、正庚醇-水、正辛醇-水、正壬醇-水8个系统常压下温度为293.15～343.15 K之间的界面张力.讨论了界面张力与温度的关系,发现烷烃-水系统界面张力随温度的升高呈直线下降趋势,而醇-水系统的界面张力则随温度的升高呈先增加后又变小的规律.另外,对目前广受关注的、估算界面张力的N-A法作了进一步的验证和讨论.     

非对称烃类体系高压汽液平衡的预测

本文基于London色散力理论和Pitzer对比态原理等统计力学基础提出了一个RKS方程改进的混合规则,进而导出一个非对称烃类体系通用二元相互作用参数的表达式:使用该RKS方程改进的混合规则,较满意地预测了21个非对称烃类的高压汽液平衡,从而显著地提高了原RKS方程假定K_(ij)=0时的预测精度。     

Physicochemical criteria for reverse osmosis separation of monohydric and polyhydric alcohols in aqueous solutions using porous cellulose acetate membranes

Reverse osmosis data using different samples of Loeb-Sourirajan-type porous cellulose acetate membranes and single-solute aqueous solution systems involving 16 monohydric alcohols, 4 phenols, 18 polyhydric alcohols, pyrogallol, ethylene glycol monoethyl ether, 6 aldehydes, and 8 carbohydrates (sugars) have been studied. The solute concentrations used were in the range of 0.0005 to 0.003 g mole/l. (～100 ppm), and operating pressure used was 250 psig in all cases. The results show that correlations of acidity and basicity parameters (obtained from IR spectra) with solute separation data are equivalent, and they have predictive capability. A method is given for estimating Taft numbers (Σσ^*) for monohydric and polyhydric alcohols from available data based on the additive nature of σ^*. Data on solute transport parameters (D_AM/Kδ) for the different solutes were calculated from membrane performance data. For all the alcohols studied, the Σσ^*-versus-log (D_AM/K)δ correlation was found to be a straight line with a slope different for different ranges of Σσ^*, but independent of the porous structure of the membrane. Based on this result, it is shown that the parameters of the Taft equation can serve as a basis for expressing solute transport parameter, and this basis offers a means for predicting membrane performance for all alcohol–water systems from a single set of experimental data for a reference solute system. This prediction technique is illustrated using experimental data for 1,3-butanediol taken as the reference solute. The general applicability of the technique has been tested for predicting the separation of some aldehydes and carbohydrates.     

Vapour—liquid equilibrium of H2S-Hydrocarbon mixtures using a generalized cubic equation of state

A generalized cubic equation of state proposed by one of the authors has been applied to the calculation of vapour-liquid equilibrium (VLE) of hydrogen sulfide-containing systems. Experimental VLE data for hydrogen sulfide + hydrocarbons, taken from the literature, have been systematically studied using the generalized equation and conventional van der Waals's mixing rules. The interaction parameter required in the mixing rules was obtained for thirteen systems at different temperatures, and a correlation for the interaction parameter as a function of the reduced temperature of the hydrocarbon solvent is proposed. The correlation for the interaction parameter is recommended for predicting VLE in processes in which hydrogen sulfide mixtures are involved.     

乙酸乙酯与CnH2n+1OH（n=1,2,3）双系统在0.3MPa下的气液平衡（英文）

Vapor-liquid equilibrium data for the binary systems of ethyl acetate + methanol,ethyl acetate + ethanol and ethyl acetate + 1-propanol at 0.3 MPa were determined.The experimental data were verified with the point-to-point test of van Ness(1973).All these systems present an azeotropic point at 0.3 MPa that increases in ester composition for longer alcohol chains.The UNIFAC in different versions and ASOG prediction models were applied.     

Thermodynamics of associated solutions—II alcohol-active solvent solutions

The modified Wiehe-Bagley expressions for G^E, H^E and V^E of alcohol-inert solvent solutions are applied to alcolhol-active solvent solutions. Excellent agreement with experimental data is obtained, even for H^E and V^E curves showing a maximum and minimum in the composition plots. The alcohol polymerization equilibrium constant depends both on the alcohol and solvent. The physical interaction parameter is calculable from pure component properties using a proposed correlation equation, which is similar to that for alcohol-inert solvent solutions. The Kretschmer-Wiebe theory for alcohol-active solvent solutions, which has been formulated incorrectly, is rederived. In our theory a chemical linking between the alcohol complex and solvent molecule through hydrogen bonding is considered in addition to the self-association of the alcohol molecules. The rederived expression for G^E fits well with the experimental data. However, the hydrogen bonding strength between the alcohol and active solvent molecules calculated is negative for the systems investigated, which is difficult to be justified.     

Correlation and prediction of the viscosity of pure hydrocarbons

A relationship is identified between the effective carbon number (ECN) and parameter b in the one-parameter viscosity euation: log (μ + 0.8) = 100 (0.0lT)^b. The generalized correlation, b = -5.745 + 0.616 In (ECN) - 40.468 (ECN)^?15, provides an equation to predict parameter b, which gives values that are within the maximum deviation of 5% for ECN < 10 and 1% for 10 < ECN < 44 of the empirically-determined values for 70 liquid hydrocarbons. The calculated viscosities are within 5% of literature data. The viscosity prediction method is simple to use, and it can be extrapolated reliably to heavier hydrocarbons.     

Reverse osmosis separation of hydrocarbons in aqueous solutions using porous cellulose acetate membranes

A physicochemical parameter, represented by the symbol Σs^*, based on molar solubility in water and molar attraction constants of Small, has been developed to express quantitatively the relative hydrophobicity, or nonpolar character, of the hydrocarbon molecule. The value of Σs^* can be calculated for a hydrocarbon from its chemical structure. The scale of Σs^* is consistent within each group of aromatic, cyclic, and noncyclic hydrocarbons. Reverse osmosis data have been obtained at 250 psig for single-solute aqueous feed solution systems involving low concentrations of 39 different hydrocarbons (including 13 aromatics, 10 cyclic, and 16 noncyclic compounds) and several samples of cellulose acetate membranes of different surface porosities. The effect of operating pressure on membrane performance has also been studied for two aromatic hydrocarbon solutes. The values of Σs^* for the solutes used were in the range of 425 to 924 for aromatic hydrocarbons, 521 to 931 for cyclic hydrocarbons, and 369 to 960 for noncyclic hydrocarbons. The reverse osmosis data have been correlated with Σs^* for each group of hydrocarbons studied. In all cases, positive solute separations were obtained, and the ratio [PR]/[PWP] was less than 1. With respect to each film, solute separation increased with increase in Σs^*, and decreased with increase in operating pressure. Also, solute separation decreased in the order aromatic hydrocarbon > cyclic hydrocarbon > noncyclic hydrocarbon at any given value of Σs^*. At a given operating pressure, for low values of Σs^* (～500 or less) solute separation increased with progressive decrease in average pore size on the membrane surface. For high values of Σs^* (～800 or more), solute separation initially increased with decrease in average pore size, then passed through a maximum and minimum with further decrease in average pore size, and again increased with still further decrease in average pore size. The results are discussed on the basis of preferential sorption of solute at the membrane–solution interface under the experimental conditions studied.     

Methanol-Water Solution Transport in Nafion Membranes with Different Cationic Forms

Measurements of liquid transport were made with a Nafion membrane at different cationic forms. The experimental data are used to estimate the alcohol permeability when the membrane is separating water and water-methanol solutions. The obtained permeability coefficient values were useful for analyzing the influence of the substituted cations on the transport process in the membranes. In the present article, the permeability coefficient of methanol in Nafion substituted by Na⁺, K⁺, Cs⁺, Mg²⁺, Ca²⁺, Ba²⁺, Fe²⁺, Fe³⁺, and Al³⁺ were reported at different methanol concentration values. The analysis of the results revealed that, in general, for ions with the same period in the periodic table, the alcohol permeability decreases with increasing the valence. In contrast, when ions with the same valence are compared, the alcohol permeability decreases when the atomic mass increases, with the exception of the Mg²⁺. As a general trend, similar alcohol permeability variation with the concentration is observed for all the cationic forms of the membrane. There is an initial increase in the permeability, and, when the methanol concentration in the solutions is about 60%, the permeability decreases with the alcohol concentration. However, in the case of trivalent ions, the methanol permeability decreases with the methanol concentration.     

L'équation NRTL pour le calcul des équilibres liquide-liquide à n-constituants

We propose a new method for the application of the NRTL equation⁽¹⁾ to the representation of phase equilibria, especially between two liquid phases, of multicomponent mixtures including polar substances; it is based on the determination of the parameters from the tie-lines in ternary liquid-liquid equilibria. The advantage of this method is to give three parameters by pair of components, in agreement with binary phase equilibria, and to allow, without any additional parameter, the prediction of liquid-liquid equilibria with more than three components. Comparison of calculated and experimental data shows that the prediction of quaternary liquid-liquid equilibria is good for the two systems found in the literature: cyclohexane, benzene, isooctane, furfural⁽²⁾ and water, benzene, heptane, dimethylformamide⁽³⁾.     

Preparation of composites of liquid‐crystalline matrix of poly(p‐phenylene‐sulfoterephthalamide) and CaCO3 by In situ mineralization

Liquid‐crystalline (LC) hydrogels were obtained from an aqueous solution of poly(p‐phenylene‐sulfoterephthalamide) (PPST) by the addition of calcium ions (Ca²⁺). The critical hydrogel formation ratio of Ca²⁺ to the sulfonic acid group in PPST (^crtR_Ca = [Ca²⁺]/[ ]) depended on the concentration of PPST, and was independent of the molecular weight of PPST. When the LC hydrogel was prepared at a concentration of 0.5 wt % and ^crtR_Ca = 0.6, and was exposed to ammonium carbonate vapor for 96 h, all Ca²⁺ in the LC hydrogel were converted into calcite crystals. The alternate soaking process for the LC hydrogel induced the formation of two mesocrystal morphologies on and in the Ca²⁺ cross‐linked LC hydrogel. Plate‐like calcite mesocrystals grew at the hydrogel/solution interface and cubic mesocrystals were present in the inner space of the hydrogel, thus composites with some ordered structures of LC matrix and CaCO₃ have been prepared through in situ mineralization. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41455.     

Gas-liquid chromatography study of poly(ethylene oxide)-solvent interactions: estimation of polymer solubility parameter

The thermodynamics of the interactions in the liquid state (70°–150°C) between poly(ethylene oxide) ($\text{M}\text{?}{}_{\mathrm{n}}\text{= 10}{}^4$) and 32 solvents covering a wide range of structure and polarity (from n-hexane to 2,2,2-trifluoroethanol) were studied by gas-liquid chromatography. The regular solution theory, in spite of its well known limitations, does allow a very self-consistent interpretation of all the data for the systems characterized by a positive Flory parameter χ, including systems of poly(ethylene oxide) and a self-associated alcohol where specific hydrogen bonding is well known. The polymer solubility parameter δ₂ (δ₂ = 9.6 ± 0.1 (cal cm^?3)^0.5 at 70°C and its temperature dependence are easily derived with good accuracy.     

Effect of Medium on Transients and on Observed Quantum Yields in Photoreduction of Benzophenone by 2-Propanol

The quantum yield for photoreduction of 0.1 M benzophenone by 2-propanol, at 313 mμ, light intensity 1 × 10¹⁶ quanta/sec cm² is ?1.16. The quantum yield increases on dilution with benzene to 1.70 at 3.13 M 2-propanol. A Stern-Volmer plot of data below 3 M 2-propanol leads to an extrapolated limiting quantum yield of ?1.9. The quantum yield in 2-propanol decreases with extent of conversion from 1.1 at 17% to 0.74 at 37% photoreduction. Quantum yields for photoreduction of 0.1 M benzophenone by 1 M 2-propanol and by 1 M benzhydrol in benzene remain constant with conversion. A light absorbing transient builds up strongly and progressively during photoreduction in 2-propanol, and to a much lesser extent in 1 M 2-propanol and 1 M benzhydrol in benzene. Photoreduction in 1 M 2-propanol in t-butyl alcohol appears to behave like that in 2-propanol; 1 M 2-propanol in acetonitrile shows behavior intermediate between that in alcoholic and in hydrocarbon solutions. Efficiency of quenching by naphthalene in alcoholic and in hydrocarbon media indicates that k_r is about twice as great in the hydrocarbon as in the alcohol solvents. The effect of the hydrocarbon in diminishing build up of the light absorbing intermediate, which may mask and possibly quench, is largely responsible for the increase in quantum yield on dilution with hydrocarbon.     

Neural network prediction of cetane number and density of diesel fuel from its chemical composition determined by LC and GC-MS

Neural networks were used to correlate and predict the cetane number and the density of diesel fuel from its chemical composition. Cetane number (CN) and density were correlated with 12 hydrocarbon groups in diesel fuel determined by liquid chromatography (LC) and gas chromatography-mass spectrometry (GC-MS). In total, 69 diesel fuels were available for this study: 48 diesel fuels were included in the training data set and 21 in the test data set. Various neural network architectures were trained using the training data set, and the accuracy of the model obtained was examined by using the test data set. For correlating both CN and density in this study, the best neural network architecture was a general regression neural network (GRNN). With the test data set, the mean absolute errors were 1.23 (CN) and 0.002 g/cm³ for the CN and density, respectively. Predictive equations for CN and density of diesel fuel from its chemical composition were also developed with a standard multiple linear regression method. The comparison of the neural network method with the multiple linear regression method, using this data set, revealed that for complex nonlinear problems such as the correlation of the CN with the hydrocarbon type characterization, the neural network approach could provide a better model. However, for a simpler correlation problem like the density of a diesel fuel, which is approximated well by the sum of the contributions of individual components, the predictive equations produced by multiple linear regression and neural network methods gave similar results.     

EQUILIBRIUM OF METALS WITH IMINODIACETIC RESIN IN BINARY AND TERNARY SYSTEMS

ABSTRACT

Experiments of binary and ternary ion exchange equilibrium of heavy metals and sodium were carried out in a complexing iminodiacetic resin Lewatit TP 207. First, binary equilibrium data were obtained at different temperatures and ionic strength and fixed to models considering two different ion exchange stoichiometrics. For ternary equilibrium data, two distinct simple models were applied. One to be applied to systems showing very different selectivity for the metals (for instance, Cu²⁺/Co²⁺/Na⁺) and the other for systems with similar selectivity for the metals (such as Zn²⁺/Co²⁺/Na⁺). The ternary equilibrium data obtained is presented in this work and fitted using the two above mentioned models. These models allow us to obtain the equilibrium parameters for binary and ternary system to be used in the design of equipment using this iminodiacetic resin.     

Liquid–liquid equilibria of ternary mixtures of methanol + MEG + n-C5, ethanol + MEG + n-C5, and n-butanol + MEG + n-C5

New liquid–liquid equilibrium data of ternary systems of mono ethylene glycol + n-pentane + methanol, mono-ethylene glycol (MEG) + n-pentane + ethanol, and mono ethylene glycol + n-pentane + n-butanol from 283.15 to 293 K are presented in this work. Binodal curves were obtained by the cloud point titration method. Tie-line compositions were obtained through density and sound velocity measurements of phases in equilibrium. Results show that the solubility increases with temperature in all systems and decreases as the alcohol chain increases. The relative solubility data indicate that the alcohols are more soluble in MEG than in n-C5. The obtained experimental data were successfully correlated using the CPA and the PC-SAFT equation with appropriate binary interaction parameters.     

Structure/Enthalpy of Formation Relationships for Hydrocarbons Containing Benzene Rings

Simple protocols to convert molecular mechanics (MMX/PCMODEL), semiempirical PM3, and HF ab initio energies to accurate heats of formation for hydrocarbons with benzene rings are described. The data set consists of every hydrocarbon benzene derivative with an experimentally determined ΔH_f^o (g), and the ΔH_f^o (g)'s cover a range of -140 to +410 kJ/mol. The molecular structures are comprised of numerous structural types. Hierarchical sets of molecular structure parameters are defined to describe these molecules. The independent variables include atom types (level 1), group and ring terms (level 2), nonbonded atom interactions (level 3), and the calculated MMX, PM3 or ab initio HF energies, which contribute a final level 4 parameter for rectification of the ΔH_f^o (g) data. The additivity, level 1-3 parameters give an excellent correlation of the experimental ΔH_f^o (g)'s, average error = 3.4 kJ, and maximum error = 12.1 kJ. However, the correlations are further enhanced by addition of any level 4 parameter, with maximum improvement coming at the 6-31G*//STO-3G HF level of calculation.