Branched-chain Paraffins Research Articles

Fischer-Tropsch Synthesis on Co/SBA-15 Catalyst: Characterization and Oligomerization Modeling

In this study, we investigated the oligomerization mechanism of the Fischer-Tropsch synthesis catalyzed by a cobalt-based catalyst supported by SBA-15. The Co/SBA-15 catalyst contained 20% w/w of cobalt. It was prepared by the wet impregnation method and characterized by X-ray diffraction (XRD), N2 adsorption-desorption, temperature-programmed reduction (TPR), and scanning electron microscopy coupled to X-ray energy dispersion spectroscopy (SEM-EDS). The FT synthesis was conducted in a slurry bed reactor operating at 240–270°C, 2.0–3.0 MPa, and 1:1–2:1 H2:CO ratio (mol:mol). An oligomerization model, based on alkyl and alkenyl mechanisms for hydrocarbon chain propagation, was used for product distribution. Impregnation with cobalt and calcination did not alter the structure of SBA-15. Cobalt oxides, including Co2O3 and Co3O4, were the active phases of the reaction. Adding cobalt to the support lowered the specific surface area and the pore volume of the support but did not change the structure of SBA-15. Fischer-Tropsch synthesis and C5+ hydrocarbon selectivity increased at a low H2:CO ratio (1.0) and low temperatures (240–255°C). The content of branched-chain paraffin and olefins increased with a decrease in the H2:CO ratio and temperature. The parameters of the model were estimated, and the assumption of a dual mechanism was satisfied.

Nonthermal Plasma-Assisted Photocatalytic Conversion of Simulated Natural Gas for High-Quality Gasoline Production near Ambient Conditions.

We report a novel nonthermal plasma-assisted photocatalytic approach that could efficiently convert the main components of natural gas, methane and propane, into high-quality gasoline chemicals abundant with C6-C9 branched-chain paraffins at low temperature and atmospheric pressure. The conversions of methane and propane can reach up to 15.0% and 48.6%, respectively. A 58.4 C% yield of gasoline products with limited coke deposition (6.3 C%) can be achieved via the combination of plasma with photocatalysis. Isotope labeling experiments show that methane prefers to be incorporated into 1-C or 2-C of the formed alkanes as a terminal group. Our work demonstrates an industrially promising strategy for the cost-efficient utilization of natural gas.

Response surface models for synthetic jet fuel properties

Jet fuel is a mixture of different hydrocarbon groups, and the mass contribution of each of these groups toward the overall chemical composition of the fuel dictates the bulk physical properties of the fuel after completion of the refining and blending processes. The fluidity properties of jet fuel mixtures at low temperatures are critical in understanding and mitigating the safety risks and performance attributes of aircraft engines, which may lead to the introduction of more stringent specification limits in the near future. Therefore, in this study the low-temperature viscosity and freeze point properties of jet fuels were investigated by variation of the linear to branched chain paraffin mass ratio, in conjunction with variation of the carbon number distribution according to a mixture by process variables experimental design. Furthermore, response surface models were developed and discussed for the two main fluidity properties of interest and inferences were made from the models for the potential generation of optimal jet fuel mixtures.

Catalytic cracking reaction of used lubricating oil to liquid fuels catalyzed by sulfated zirconia

The conversion of used lubricating oil to transport fuel by direct cracking is a suitable way to dispose of waste oil. The aim of this research was to study the catalytic cracking of used lubricating oil, and thus change its classification from a waste produce to a liquid fuel as a new alternative for the replacement of petroleum fuels. The experiments were carried out in a 70-cm3 batch microreactor at a temperature of 648-698 K, initial hydrogen pressure of 1-4 MPa, and reaction time of 10-90 min over sulfated zirconia as a catalyst. The conditions that gave the highest conversion of naphtha (~20.60%) were a temperature of 698 K, a hydrogen pressure of 2 MPa, and a reaction time of 60 min, whereas, under the same conditions, kerosene, light gas oil, gas oil, long residues, hydrocarbon gases, and a small amounts of solids were present (~9.04%, 15.61%, 5.00%, 23.30%, 25.58%, and 0.87%, respectively). The liquid product consisted of C7-C15 of n-paraffins, C7-C9 of branched chain paraffin and aromatic compounds such as toluene, ethylbenzene and xylene. The kinetic study reveals that the catalytic cracking of waste lubricating oil follows a second order reaction, and the kinetic model is defined as k(s−1)=2.88×104exp[−(103.68 kJmol−1)/(RT)].

99/01900 Molecular sieve-based catalyst and process for the selective hydroisomerization of long straight chain and/or branched chain paraffins using this catalyst: Marcilly, C. et al. Eur. Pat. Appl. EP 863,198, (Cl. C10G45/64), 9 Sep 1998, FR Appl. 97/2,598, 5 Mar 1997, 9 pp. (In French)

99/01900 Molecular sieve-based catalyst and process for the selective hydroisomerization of long straight chain and/or branched chain paraffins using this catalyst: Marcilly, C. et al. Eur. Pat. Appl. EP 863,198, (Cl. C10G45/64), 9 Sep 1998, FR Appl. 97/2,598, 5 Mar 1997, 9 pp. (In French)

The seasonal variation of nonmethane hydrocarbons in the free troposphere over the North Atlantic Ocean: Possible evidence for extensive reaction of hydrocarbons with the nitrate radical

Detailed observations have been made of the seasonal variation in concentration of a wide range of nonmethane hydrocarbons over the North Atlantic Ocean in air with a predominantly polar maritime origin. The results bear out many of the findings of our previous studies [Lightman et al., 1990] with the observation of a concentration maximum in the winter and a minimum in the summer. The more recent results indicate that the amplitude of the seasonal cycle is remarkably constant. Also the total concentration of reactive carbon in the various forms of nonmethane hydrocarbons probably exceeds 20 ppbC. This constitutes a substantial reservoir of material which could take part in ozone production in the relatively remote troposphere, if sufficient nitrogen oxides are copresent. The hydrocarbon composition of air in winter is strongly dependent on its origin, with tropical air having a composition similar to polar air in the spring months. The relative magnitude of the seasonal cycles for some hydrocarbons is proportional to their rates of reaction with hydroxyl radicals. This is true for straight chain paraffins up to C5, acetylene and benzene, and it suggests that the removal of these molecules from the atmosphere occurs predominantly by reaction with hydroxyl radicals. For other molecules, particularly branched chain paraffins and substituted aromatic molecules, there is evidence that other removal processes are operating in competition with the hydroxyl radical, especially in winter. Arguments are advanced that in the case of the branched chain paraffins this may be caused by reaction with nitrate radicals.

Biodegradation in South Texas Eocene oils — Effects on aromatics and biomarkers

The Eocene oil producing trend in South Texas provides an excellent area for studying sequential effects of biodegradation on crude oil composition. Many small fields contain oils of a common genetic type which exhibit a broad range of biodegration stages. Gas chromatograms of 26 oils from Eocene Jackson reservoirs in Duval County, Texas, show that n-paraffins are missing in 23 oils, while the other three appear to be undegraded. Among the degraded samples, a progressive increase in degradation is indicated by first a gradual disappearance of isoprenoids, then by disappearance of other prominent peaks in the C 13–C 17 range. Gas chromatography-mass spectrometry analyses were on nine oils, selected on the basis of their gas chromatograms to represent various biodegradation stages. Changes in distributions of geochemically important compound types, including the more common biomarkers, were related to extent of biodegradation. Significant observations include: (1) two- and three-ring aromatics, including benzo- and dibenzothiophenes show selectivity in degradation and disappear during adjacent degradation stages; (2) a series of adamantanes is unaffected; (3) steranes and aromatized steroid hydrocarbons remain undegraded; (4) tricyclic and tetracyclic terpanes are not degraded, but ammong pentacyclic triterpanes, a a slight decrease in C 29 and C 30 hopanes can be seen; and (5) bicyclic and diterpanes are degraded irregularly and less rapidly than aromatics. Aside from an early loss of straight-chain and branched-chain paraffins, biodegradation may follow quite different routes at different locations, particularly with regard to aromatics. Therefore, criteria for correlating biodegraded oils and assessing biodegradation stages on the basis of aromatic hydrocarbon distributions must be carefully selected.

A Review of Unique Male Rat Hydrocarbon Nephropathy

There is a diverse group of hydrocarbons that induce a specific spectrum of nephropathic alterations. Examples include decalin, an alicyclic hydrocarbon; JP5 jet fuel, a mixture of C12-15 straight and branched chain hydrocarbons; C10-11 isoparaffinic hydrocarbons; Stoddard solvent, a mixture of straight and branched-chain paraffins, naphthenes, and alkyl aromatic hydrocarbons; 2,2,4-trimethylpentane, a branched chain hydrocarbon and d-limonene, an aromatic hydrocarbon. Only male rats develop kidney alterations upon exposure to these chemicals. Other mammals such as female rats, mice, guinea pigs, dogs and monkeys evidently are refractory to kidney injury upon exposure. The primary effect of decalin is to specifically exacerbate the accumulation of alpha 2 mu-globulin, a unique protein occurring spontaneously in proximal convoluted tubular epithelial cells only in the mature male rat. Thus, the male rat hydrocarbon nephropathy should not be predictive of a normal human renal response.

Peak shapes and adsorption kinetics: Gas-solid chromatography with a coated anatase stationary phase

Experiments are described with a novel gas-solid stationary phase consisting of anatase coated with a carbonaceous material resulting from the disproportionation reaction of 1,3-butadiene. At 204°C, tailing peaks are observed for branched-chain paraffins while the peaks of straight-chain isomers are symmetrical. Changes of peak shape and of the adsorption coefficient with gas flow-rate are accounted for in terms of variations in the kinetics of adsorption and desorption on different surface sites.

ZEOLITE SUPPORTED Ru–Pt CATALYSTS FOR SELECTIVE FISCHER-TROPSCH SYNTHESIS

Abstract Ruthenium–platinum bimetallic catalysts, prepared by simultaneous ion-exchange on zeolite HY, selectively produced from synthesis gas branched-chain paraffins in the C4–C10 range, Exception to this was found for a catalyst with 4% Ru and 2% Pt by weight, which was highly active in exclusive formation of CH4.

Temperature dependence of the retention indices of branched-chain paraffins on non-polar stationary phases: A method for its calculation on the basis of molecular structure

The temperature dependence, ΔI/°C, of the retention indices of manybranches paraffins with six to eight carbon atoms was investigated using SF-96 columns, in the temperature range 80-120°. Linear relationships were observed for all the compounds examined, and the calculation of the correct analysis observed for all the compounds examined, and the calculation of the correct analysis temperature for the separation of interesting pairs of isomers was therefore possible. The dependence of ΔI/°C on the skeletal structure of the compounds permitted the determination of characteristic additive terms correlated with structural groups in the molecules, which could be added to give the overall temperature dependence of the index of any isometric compound. The effect of temperature programming on the separation of interesting pairs of isomers was also investigated.

A method for the identification of branched-chain paraffins by calculation of their retention index values on the basis of molecular structure and physical properties

The retention times of branched-chain paraffins were shown to depend on their physical properties, especially molecular volume, when non-polar phases were used for their separation. As the molecular volume depends strongly on structure, the calculation of additive terms, which are characteristic of every structural group in a molecule, can permit the theoretical calculation of the retention indices of any branched isomer. The additive terms can be calculated both by solving a system of equations and by comparison of the retention indices of selected compounds. The general application of the method to retention data taken from the literature is also possible.

CNDO, INDO and RCNDO-CI calculations on the electronic spectra of saturated hydrocarbons

CNDO, INDO and RCNDO (CNDO including higher (Rydberg) atomic orbitals in the basis) calculations completed by first order configuration interaction were performed on straight chain and branched chain paraffins. The results interpret reasonably the main characteristics of the observed electronic spectra. The importance of outer atomic orbitals is stressed and it is found that the first singlet-singlet transition of highly branched paraffins leads to an excited state with considerable Rydberg character.

Ionization of liquids by radiation: measurement by a clearing field.

A method has been developed for determining the yield of free ions formed by irradiation of a liquid with high-energy x-rays. Contrary to expectation, branched-chain paraffins produce many more free ions than straight-chain paraffins do, and the ether 1,4-dioxane produced only a third as many free ions as its hydrocarbon analog, cyclohexane.

The far-ultraviolet spectra of branched chain paraffins

The far ultraviolet spectra of gaseous isobutane, isopentane and neopentane were measured up to 1150 angstroms. They are compared to the related normal isomer in each case. A tentative interpretation of the spectra is given.

Analysis of cold-pressed orange oil paraffin waxes

The paraffins in cold-pressed Valencia orange oil were isolated by column chromatography, separated by gas chromatography, and identified by mass spectroscopy. Normal and branched chain paraffins from C 21 to C 29 were found. The normal and the branched C 23 and C 25 predominate; n-C 23 is the major component. The preponderance of the low carbon number paraffins and, in particular the isoparaffins are characteristic to the orange in the plant kingdom. These isoparaffins are identified for the first time in natural products.

Thermodynamic properties of urea-hydrocarbon adducts. Part 2.—Heat capacities of adducts of n-pentadecane and 2-methyl-pentadecane from 12 to 300°K

The heat capacities of the adducts of urea with n-pentadecane and 2-methyl-pentadecane have been measured from 12 to 300°K. The n-pentadecane adduct showed a region of anomalously high heat absorption at 158.4°K; the adduct of the branched-chain paraffin, on the other hand, had no significant thermal anomaly. The entropies of both adducts at 298.15°K have been calculated. A comparison is made of the entropies of adduction of n-C15H32, n-C10H22, n-C12H26 and n-C16H34 as calculated from the heat capacity data with the corresponding values obtained from equilibrium constant measurements by Redlich. The discrepancies between the two sets of values are within the limits of error set by the equilibrium constant data for the decane compound, but for the other substances the values from the heat capacity data are up to 22 % smaller in magnitude.

Solubility in Water of C1–C9 Hydrocarbons

THE solubilities in water of C1–C8 paraffin and branchedchain paraffin, 4 cycloparaffin, and 5 aromatic hydrocarbons have been determined using a gas-liquid partition chromatographic technique.

G-and F-Matrices of Branched Chain Paraffins

G-and F-Matrices of Branched Chain Paraffins

Constituents of the trunk bark of Melia azadirachta Linn. and the structure of the ketophenol, nimbiol

From the trunk bark of Melia azadirachta Linn. have been isolated a branched chain paraffin alcohol, C 26H 54O, nimbosterol, sugiol (I, R = H) and a new ketophenol, nimbiol having the molecular formula, C 18H 24O 2. Nimbosterol has been identified as β-sitosterol and nimbiol has been shown to possess the structure (II, R = H). The biogenetic considerations for the possible formation of sugiol and nimbiol in the same plant have also been discussed.