A comparison of Nylon-66-supported platinum and palladium catalysts for the hydrogenation of 1-octyne in the liquid phase

A number of Nylon-66 fibre-supported platinum (Pt) catalysts were prepared by refluxing solutions of ammonium chloroplatinite with Nylon-66 fibres. The resulting Pt-Nylon-66 catalysts were used for the hydrogenation of 1-octyne in n-propanol and n-heptane at 70°C and 1 atm. total pressure. They, like their palladium (Pd) counterparts, exhibited solvent sensitivity in respect of their selectivity for 1-octyne production. However, both activity and selectivity trends, as metal concentration increased, were different from those exhibited by Pd-Nylon-66 catalysts. Pd-Nylon-66 catalysts gave an activity maximum, whereas Pt-Nylon-66 catalysts did not, activity increasing with metal concentration. Both catalysts gave constant selectivity, independent of metal concentration in n-heptane (Pd-Nylon-66 = 0.99–1.00; Pt-Nylon-66=0.75–0.76). In n-propanol Pd catalysts gave high selectivity (0.99–1.00) for low metal concentrations. Pt-Nylon-66 catalysts exhibited the opposite tendency, giving low selectivity (0.46–0.50) at low metal concentrations and higher selectivity (0.75–0.76) at high metal concentrations. It is concluded that, whereas Pd-Nylon-66 catalysts exist as some form of Pd(II) complex over a wide concentration range, Pt-Nylon-66 only exists as a complex at low concentrations and becomes predominantly zero-valent (metallic) Pt supported on the Nylon-66 at higher concentrations.     

Effect of Alkylate Isomerism upon Surfactant Retention in an HPLC Column and Partitioning between Water and Oil

Abstract

The degree of isomerization in the alkyl chain of ethoxylated alkylphenol surfactants influences the retention time in a HPLC silica column and the partitioning coefficient between n-heptane and water. HPLC analysis of isomer species with different alkyl groups allows the deduction of some general trends in the influence of isomerization and branching on the surfactant properties. The alkyl group interaction with the solvent and the heptane-water partitioning data show that direct interaction between the surfactant “tail” and the solvent is also of importance.     

Extraction of toluene and n-heptane mixture using ionic liquid Aliquat 336 and mathematical modeling for solvent selection

Liquid–liquid equilibrium data for the system consisting of toluene, n-heptane and Aliquat 336 ionic liquid was obtained at 303.15 K and atmospheric pressure. The values of distribution coefficient and selectivity were evaluated. Mathematical model relating distribution coefficient and dispersion, dipolar interaction and hydrogen bonding has been developed. Hansen’s solubility parameters were used to determine the parameters. The model was applied for various ionic liquids as solvents. The model predicted the trends similar to the trend reported in the literature. Thus model can predict better solvent for the given extraction application. This methodology has great potential to act as a knowledge-based framework to aid development of new tailor-made solvents. This will save cost and time in experimentation and analysis.     

INFLUENCE OF SOLVENT POLARITY ON INTERFACIAL MECHANISM AND EFFICIENCY OF SUCCINIC ACID REACTIVE EXTRACTION WITH TRI-n-OCTYLAMINE

This article presents the results of a comparative study of reactive extraction of succinic acid with tri-n-octylamine (TOA) dissolved in solvents with different dielectric constants (dichloromethane, n-butyl acetate, and n-heptane), with and without octan-1-ol addition as phase modifier. The positive effect of octan-1-ol on extraction efficiency was quantified by means of amplification factors. For all studied systems, the addition of octan-1-ol into the solvent phase led to an increase of extraction efficiency, the most important effect being recorded for the solvent with the lowest polarity, namely n-heptane. The maximum value of amplification factor was reached for pH = 6 and indicated an increase of reactive extraction yield of about 1.26 times for dichloromethane, 1.55 times for n-butyl acetate, and 2.88 times for n-heptane.     

Physico-Chemical Studies on Microemulsion: Effect of Cosurfactant Chain Length on the Phase Behavior,Formation Dynamics,Structural Parameters and Viscosity of Water/(Polysorbate-20 + <Emphasis Type="Italic">n</Emphasis>-Alkanol)/<Emphasis Type="Italic">n</Emphasis>-Heptane Water-in-Oil Microemulsion

The pseudo-ternary water-in-oil microemulsion system, comprising water/polyoxyethylene sorbitan monolaurate (Polysorbate-20) + n-alkanol/n-heptane, have been studied by phase manifestation, method of dilution, viscosity and dynamic light scattering measurements. Polysorbate-20, in combination with equal mass of cosurfactants (of varying chain length, from n-butanol to n-octanol) were used in studying the systems in the temperature range 303–323 K. Appearance of turbidity was noted visually, which indicated the attainment of immiscibility or phase separation; a clear dependence of the different phases on cosurfactant chain length was noted. By employing the method of dilution, associated thermodynamic parameters for the formation of water-in-oil microemulsion droplets were derived. Different associated structural parameters were derived through further computation of the data derived from the method of dilution. Unusual behavior of Polysorbate-20, compared to the conventional ionic surfactants, was noted. Viscosity measurements, as carried out with different compositions and temperatures, revealed the temperature and water pool size dependency of the microemulsion systems. Viscosity data did not follow the same trend during heating and the cooling process, due to the condensation effect. This phenomenon was further confirmed by dynamic light scattering measurements.     

Monodisperse monocomponent fuel droplet heating and evaporation

The results of numerical and experimental studies of heating and evaporation of monodisperse acetone, ethanol, 3-pentanone, n-heptane, n-decane and n-dodecane droplets in an ambient air of fixed temperature and atmospheric pressure are reported. The numerical model took into account the finite thermal conductivity of droplets and recirculation inside them based on the effective thermal conductivity model and the analytical solution to the heat conduction equation inside droplets. The effects of interaction between droplets are taken into account based on the experimentally determined corrections to Nusselt and Sherwood numbers. It is pointed out that the interactions between droplets lead to noticeable reduction of their heating in the case of ethanol, 3-pentanone, n-heptane, n-decane and n-dodecane droplets, and reduction of their cooling in the case of acetone. Although the trends of experimentally observed droplet temperatures and radii are the same as predicted by the model taking into account the interaction between droplets, the actual values of the predicted droplet temperatures can differ from the observed ones by up to about 8 K, and the actual values of the predicted droplet radii can differ from the observed ones by up to about 2%. It is concluded that the effective thermal conductivity model, based on the analytical solution to the heat conduction equation inside droplets, can predict the observed average temperature of droplets with possible errors not exceeding several K, and observed droplet radii with possible errors not exceeding 2% in most cases. These results allow us to recommend the implementation of this model into CFD codes and to use it for multidimensional modelling of spray heating and evaporation based on these codes.     

Recent progress in the manufacture of alkanesulfonates: Photosulfochlorination of single-chain length (C12−C16) n-alkanes using SO2Cl2 at high conversion rates in pure phase and in the presence of solvent

Increasing concentration of sulfuryl chloride during the photosulfochlorination reaction under visible light shows that under these conditions n-alkanes react at high conversion rates instead of the conversion rate of 15% reported in the literature. This photosulfochlorination with sulfuryl chloride leads to better and more interesting results compared with those of photosulfochlorination by gas mixture. Indeed, nearly total conversion of n-alkanes, specifically n-heptane, n-dodecane, n-tetradecane, and n-hexadecane, occurred in pure phase, with a quantitative global yield, a sulfochlorination-to-chlorination molar ratio of about 1, and a relative reactivity of secondary to primary hydrogen of about 2.5, at a reaction temperature of 30°C and a reaction time of 120 min, using 2×10⁻² mol L⁻¹ of pyridine. Under these conditions, no polysulfochlorinated compounds are detected. These results are further improved using chlorobenzene as the solvent, instead of benzene. Indeed, the sulfochlorination of n-heptane at a conversion rate of 80% in the presence of chlorobenzene leads also to a quantitative reaction yield, a higher RSO₂Cl/RCl molar ratio, and, as expected, a high selectivity of secondary over primary hydrogen. Under these conditions, sulfochlorination of long-chain n-alkanes leads to the highest RSO₂Cl/RCl molar ratio for n-dodecane, n-tetradecane, and n-hexadecane belonging to detergent range, and the value of the molar ratio for these is between 1.45 and 1.7. The isomeric distribution of sulfochlorinated compounds obtained during sulfochlorination in the presence of solvent resembles that of secondary alkanesul-fonates produced by sulfoxidation reaction, whereas that obtained in pure phase has a similar conversion rate, is rich in primary isomer, and thus is different from that of classic radical reactions such as photochlorination or photosulfochlorination with gas mixture.     

Liquid-phase adsorption and isomerization of C<Subscript>5</Subscript>-C<Subscript>8</Subscript><Emphasis Type="Italic">n</Emphasis>-paraffins

The liquid-phase adsorption of n-pentane, n-hexane, n-heptane, and n-octane from natural gasoline on zeolite CaA and their catalytic isomerization has been investigated experimentally and theoretically with the aim of increasing the octane number of a low-octane gasoline. An integrated process flowsheet combining processes in an adsorber and in an isomerization reactor has been developed. The basic results are as follows: the ultimate activity of CaA with respect to n-pentane, n-hexane, n-heptane, and n-octane in the case of their simultaneous adsorption at 25.0°C is 4.2, 4.7, 5.1, and 6.3 kg/100 kg, respectively. Kinetic and outlet adsorption data are also presented. The maximum yield of C₅, C₆, C₇, and C₈ iso-paraffins is 62.0, 70.0, 66.0, and 47.0%, respectively. A mathematical model of the processes has been developed, and their parameters have been calculated. Calculated and experimental data are in satisfactory agreement.     

Ga2O3/HZSM5 propane aromatization catalysts. Influence of the hydrogen pretreatment on the acid and redox functions

The activity and selectivity of a mechanical Ga₂O₃/HZSM5 mixture in four model reactions (propane aromatization at 803 K,n-heptane cracking and meta-xylene isomerization at 623 K, methylcyclohexane transformation at 773 K) were compared after pretreatment at 873 K under nitrogen and under hydrogen flow. It was thus demonstrated that the hydrogen treatment provoked a significant increase in the dehydrogenating activity of the gallium species but only a small decrease in the protonic acidity. Moreover this hydrogen treatment created a significant hydrogenolysis activity.     

Active sites on Pt containing sulfated zirconia

The influence of the Pt and sulfate concentration on the activity of Pt containing sulfated zirconia for n-heptane conversion was investigated. Pt was deposited on the support by impregnation and by photocatalytic deposition. The amount deposited was 2.5 and 0.4 wt% respectively. For comparison a hybrid catalyst consisting of sulfated zirconia and Pt on SiO₂ was prepared. As supports a commercial sulfated zirconia with a fixed sulfate concentration, a commercial and self synthesized Zr(OH)₄ were used. The sulfate content varied between 20 and 60% of a monolayer. The shifts to higher frequency in the IR spectra of CO adsorbed on Pt correlate with the increasing amounts of sulfates on zirconia and are attributable to the changes in the electron density of the supported metal, i.e. the electron deficiency of Pt increases with increasing concentration of acid sites. After activation in air and reduction in hydrogen two SO₂ peaks were detected by a temperature programmed heating procedure (TPE—temperature programmed evolution). The lower the desorption temperature of the first SO₂ peak, the higher the activity. The shift to lower temperature is connected with a higher Pt and sulfate concentration, furthermore with the proximity of the metal to acid sites. The catalysts with a low sulfate concentration possess only Lewis acid sites and are inactive for n-heptane conversion. At higher sulfate concentration, Br?nsted acid sites are present and the catalysts are active. The concentration of these acid sites is related to the concentration of sulfates, which desorb at lower temperature. Dedicated to Professor Konrad Hayek.     

Measurement of the PVTx properties of n-heptane in supercritical water

By means of a constant-volume piezometer, measurements have been made of the PVTx properties of water-n-heptane mixtures at supercritical conditions. The measurements cover the temperature range from 573 to 673 K and pressures from 2 to 30 MPa. Values of excess, partial, and apparent molar volumes were obtained from these measurements. Tests on the piezometer and consistency tests on the measurements suggest that the results are free from significant ‘dead volume’ error. The PVT data for the pure components (water and n-heptane) obtained using the piezometer are in excellent agreement with results obtained by other investigators. The overall accuracy of the pressure, density, temperature, and mole fraction are ± 0.15%, ± 0.5%, ± 10 mK and ± 0.002, respectively.Analysis of the results for dilute water-n-heptane mixtures show that the partial molar volume of n-heptane (solute) and the excess molar volume of the mixture near the critical point of pure water (solvent) exhibit remarkable anomalies. Our results contribute to the formulation of supercritical solubility in near-critical fluids.     

Synthesis and characterization of solid-phase super acid catalysts and their application for isomerization of n-alkanes

In the present work, first, the reference catalyst super acidic nanostructured sulfated zirconia (SZ) and super acidic nanostructured aluminum chloride impregnated sulfated zirconium oxides in mole ratios of Zr⁴⁺:Al³⁺ as 2:1 (ACSZ-1), 1:1 (ACSZ-2), and 1:2 (ACSZ-3) were synthesized by a simple precipitation method. The catalytic performance of these four catalysts were evaluated during the isomerization of n-hexane, n-heptane, and n-octane to their corresponding branched chain isomers at low temperature and pressure conditions. ACSZ-2 shows high activity toward isomerization of n-hexane, n-heptane, and n-octane into their corresponding branched chain isomers. The reference catalyst SZ was proved to be less effective compare to the other three synthesized ACSZ catalysts. Ammonia-temperature-programmed desorption of these two materials ensures that the super acidity of ACSZ-2 is higher than that of SZ. Atomic force microscopic and scanning electron microscopic pictures predict the nature of the surface of the catalysts. Transmission electron micrographic analysis indicates the presence of particle-bulks having average size 12–20?nm, presenting an amorphous nature and having no definite surface morphology of ACSZ-2. Fourier transform infrared provides an outline regarding different linkages and bond connectivities between atoms and groups in ACSZ-2 and SZ. After catalyst evaluation and characterization a probable reaction mechanism has been proposed theoretically. The reactivity and selectivity of ACSZ-2 and SZ as well as the order and activation energy of the isomerization reactions in presence of ACSZ-2 have been calculated. The use of ACSZ-2 is beneficial from the point of cost efficiency as well as its use is energy saving.     

Catalytic Hydroprocessing of p-Cresol: Metal, Solvent and Mass-Transfer Effects

A systematic study of the comparative performances of supported Pt, Pd, Ru and conventional CoMo/Al₂O₃, NiMo/Al₂O₃, NiW/Al₂O₃ catalysts as well as the effects of solvent, H₂ pressure and temperature on the hydroprocessing activity of a representative model bio-oil compound (e.g., p-cresol) is presented. With water as solvent, Pt/C catalyst shows the highest activity and selectivity towards hydrocarbons (toluene and methylcyclohexane), followed by Pt/Al₂O₃, Pd and Ru catalysts. Calculations indicate that the reactions in aqueous phase are hindered by mass-transfer limitations at the investigated conditions. In contrast, with supercritical n-heptane as solvent at identical pressure and temperature, the reactant and H₂ are completely miscible and calculations indicate that mass-transfer limitations are eliminated. All the noble metal catalysts (Pt, Pd and Ru) show nearly total conversion but low selectivity to toluene in supercritical n-heptane. Further, conventional CoMo/Al₂O₃, NiMo/Al₂O₃ and NiW/Al₂O₃ catalysts do not show any hydrodeoxygenation activity in water, but in supercritical n-heptane, CoMo/Al₂O₃ shows the highest activity among the tested conventional catalysts with 97?% selectivity to toluene. Systematic parametric investigations with Pt/C and Pt/Al₂O₃ catalysts indicate that with water as the solvent, the reaction occurs in a liquid phase with low H₂ availability (i.e., low H₂ surface coverage) and toluene formation is favored. In supercritical n-heptane with high H₂ availability (i.e., high H₂ surface coverage), the ring hydrogenation pathway is favored leading to the high selectivity to 4-methylcyclohexanol. In addition to differences in H₂ surface coverage, the starkly different selectivities between the two solvents may also be due to the influence of solvent polarity on p-cresol adsorption characteristics.     

Development of nonwovens for water treatment

The sorption capacity of binder polymer with respect to organic contaminants was established on the example of the n-butanol—water model system with different concentrations of n-butanol. It was shown that bonded nonwovens filled with activated carbon fabricated with latex impregnating compounds can sorb organic contaminants from aqueous media.     

A rigorous kinetic model for β-carotene oxidation in the presence of an antioxidant, α-tocopherol

Oxidation of β-carotene in an inert solvent, n-decane, in the presence of various concentrations of the antioxidant α-tocopherol was studied. The progress of carotene oxidation was suppressed as long as the tocopherol remained in the system. A rigorous kinetic model for carotene oxidation in the presence of an antioxidant was proposed based on a reaction mechanism in which not only the antioxidation but also the co-oxidation and radical-exchange reaction of tocopherol with carotene were incorporated. The model quantitatively described the oxidation behavior of carotene over a wide range of temperatures, oxygen compositions, and initial antioxidant concentrations.     

Liquid-liquid equilibria for toluene-heptane-N-methyl pyrrolidone and benzene-heptane solvents

The liquid-liquid equilibria for toluene-n-heptane-N-methyl pyrrolidone containing 10 and 20% water at 298 and 313 K, and of benzene-n-heptane with N-methyl pyrrolidone-ethylene glycol and γ-butyrolactone-ethylene glycol, which is a new solvent combination, have been determined at 303 K.     

Experimental study on the auto-ignition and combustion characteristics in the homogeneous charge compression ignition (HCCI) combustion operation with ethanol/n-heptane blend fuels by port injection

This article investigates the auto-ignition, combustion, and emission characteristics of homogeneous charge compression ignition (HCCI) combustion engines fuelled with n-heptane and ethanol/n-heptane blend fuels. The experiments were conducted on a single-cylinder HCCI engine using neat n-heptane, and 10%, 20%, 30%, 40%, and 50% ethanol/n-heptane blend fuels (by volume) at a fixed engine speed of 1800 r/min. The results show that, with the introduction of ethanol in n-heptane, the maximum indicated mean effective pressure (IMEP) can be expanded from 3.38 bar of neat n-heptane to 5.1 bar, the indicated thermal efficiency can also be increased up to 50% at large engine loads, but the thermal efficiency deteriorated at light engine load. Due to the much higher octane number of ethanol, the cool-flame reaction delays, the initial temperature corresponding the cool-flame reaction increases, and the peak value of the low-temperature heat release decreases with the increase of ethanol addition in the blend fuels. Furthermore, the low-temperature heat release is indiscernible when the ethanol volume increases up to 50%. In the case of the neat n-heptane and 10% ethanol/n-heptane blends, the combustion duration is very short due to the early ignition timing. For 20–50% ethanol/n-heptane blend fuels, the ignition timing is gradually delayed to the top dead center (TDC) by the ethanol addition. As a result, the combustion duration prolongs obviously at the same engine load when compared to the neat n-heptane fuel. At overall stable operation ranges, the HC emissions for n-heptane and 10–30% ethanol/n-heptane blends are very low, while HC emissions increase substantially for 40% and 50% ethanol/n-heptane blends. CO emissions show another tendency compared to HC emissions. At the engine load of 1.5–2.5 bar, CO emissions are very high for all fuels. Beside this range, CO emissions decrease both for large load and light load. In terms of operation stability of HCCI combustion, for a constant energy input, n-heptane shows an excellent repeatability and light cycle-to-cycle variation, while the cycle-to-cycle variation of the maximum combustion pressure and its corresponding crank angle, and ignition timing deteriorated with the increase of ethanol addition.     

Supercritical Fischer-Tropsch synthesis: The effect of nonideality of the reaction mixture on the reaction rate

A kinetic model is derived from experimental data for the Fischer-Tropsch reaction on a precipitated iron catalyst. In this model, the effect of nonideality of the reaction medium on the reaction rate is taken into account by introducing fugacity coefficients derived from a modified Redlich-Kwong-Soave equation of state. Coefficients of the Schulz-Flory distribution for saturated and unsaturated hydrocarbon products were calculated as functions of CO and H₂ fugacities in the reaction mixture. The proposed kinetic model is applicable atT= 523–623 K andP = 6–100 atm. A method based on the calculated critical parameters of the reaction mixture is proposed for the selection of suitable supercritical solvent and for the optimization of its concentration. The reaction rate and the total yield of C_nH_2n (n ≥ 2) olefins (including the desired fraction C₅–C₁₁) under supercritical conditions were demonstrated to be essentially higher than those for the reference process carried out in the absence of solvent.     

Zeolite beta catalysts for n-C7 hydroisomerization

Zeolite β with Si/2Al ratios of 60, 100, and 200 were synthesized using tetraethlammonium hydroxide (TEAOH) as the structure-directing agent (SDA) in the absence of alkali metal cations. Pt, Pd and Pt-Pd catalysts supported on the zeolite β samples were studied in n-heptane (n-C7) hydroisomerization. The Pt/β catalysts showed a higher catalytic activity than the Pd/β catalysts. For the Pt/β with a Si/2Al ratio of 100, its n-C7 conversion and selectivity of C7 isomers were observed to be 87.06% and 75.48% respectively at 250^∘C. The activity of n-C7 conversion was stable for at least 82 h. However, the selectivity of C7 isomers was gradually decreased with the reaction time. Experimental data also showed that the addition of Pd to catalyst Pt/β enhanced the n-C7 conversion, but lowered the selectivity of C7 isomers. Pd catalyst was also observed to minimize the formation of aromatics in comparison with Pt catalyst.