Hydrocarbon Part Research Articles

Composition and structure of resins in lube distillates from west siberian crudes

As a result of the lower contents of lube components in the crudes being processed today, along with a steady increase of demand for high-quality oils and solid hydrocarbons, as well as the trend toward processing crudes with unregulated composition, it has become necessary to develop new technology for the manufacture of lube stocks, along with the use of additives for various purposes. The effectiveness of additives is determined by their properties and also by the chemical composition of the raw material in each stage of oil production. Resins are important components of raw lube stocks. These resins are complex in composition, and vary in the nature and number of heteroatoms in the molecule and in the structure of the hydrocarbon part of the molecule. The hydrocarbon radicals may include aromatic and naphthenic rings, as well as chains with various configurations. Depending on the structural features of the resin molecules, they may vary in their effects on processes of selective solvent treating, dewaxing, and deoiling with the use of additives. The authors have investigated the resins present in the intermediate and final products of lube oil production.

Phase transition behavior in the perovskite-type layer compound (n-C 12H 25NH 3) 2CuCl 4

The solid state phase transitions in the perovskite-type layer compound ( n-C 12H 25NH 3 2CuCl 4, have been studied by X-ray diffraction, differential scanning calorimetry and i.r. spectroscopy. Two-step reversible phase transitions are observed at T c 1 = 327.9 K and T c 2 = 335.7 K on heating whereas at T c 1 = 324.4 K and T c 2= 330.1 K on cooling, accompanied with the increase of interlayer distance ( Δ d 1≅ 1.8 A ̊ and Δ d 2≅ 0.85 A ̊ , respectively). In the first transition important melting of the hydrocarbon chains occurs together with the flipping of polar NH 3 groups. Defects of the gt 3 g′ and end gauche forms are found. The weakening of the NH-Cl hydrogen bonds is also observed. Further conformational changes of the hydrocarbon part are dominantly observed in the second phase transition. As the interlayer spacing is increased, only short gtg ' kinks are allowed. The mechanism of conformational transition for this compound can be therefore suggested as follows: gt 9 or tgt 8 → 2g − 2 kink (−gt 3g′−) → 2g −1 kink (−gtg′−) .

Salting-out thin-layer chromatography of transition metal complexes. III: Investigation of the behaviour of mixed aminocarboxylato cobalt(III) complexes on cellulose

Salting-out thin-layer chromatography of fourteen mixed aminocarboxylato cobalt(III) complexes (three homologous series) on cellulose has been investigated with eight aqueous ammonium sulphate solutions. A pronounced salting-out effect, with reversed-phase order, was observed with bis(aminocarboxylato) complexes, whereas with mono(aminocarboxylato) complexes such a behaviour was noticeable only at higher salt concentrations. In both cases a positive linear dependence between the RM values of the complexes and mol % of the salt in the solvent system, and between the RM values and the number of carbon atoms in the hydrocarbon part of the complexes belonging to the same homologous series, were found. These phenomena were explained by the mechanism of non-specific hydrophobic interactions.

High-boiling fractions of crude from Tengiz field as raw material for lube oil production

Tengiz crude, as has been shown by classification studies [1, 2], is light, medium-sulfur, low-resin, and medium-wax. Its content of light fractions distilling below 350~ is 75-78% by weight, which is 1.5 times the content in the major West Siberian crudes. Therefore, it has been recommended that the Tengiz should be processed in the "fuel variant," i.e., primarily to obtain fuels. In order to evaluate the high-boiling fractions of Tengiz crude as a raw material for lube oil production, its atmospheric resid was subjected to vacuum distillation, taking 300-400, 400-450, and 450-500~ distillate cuts. The residue above 500~ (vacuum resid) was propane-deasphalted. Such distillates and deasphalted oil are commonly used as raw materials for the production of lube oil components. Judging from the data of Table 1, the Tengiz atmospheric resid has greater amounts of lube distillates but a considerably smaller amount of deasphalted resid in comparison with the atmospheric resids from largevolume West Siberian crudes [3]. Another distinctive feature of the Tengiz atmospheric resid is the gradual decrease of the lube distillate content with increasing boiling point. As a result, the content of low-viscosity distillate is more than twice that of viscous distillate or deasphalted oil. The comparatively low dewaxing yields from the distillates and deasphalted oil are evidence of higher wax contents in the original distillates and deasphalted oil in comparison with the analogous products from major medium-sulfur medium-wax crudes. The high density, refractive index, and specific dispersion that are observed for the dewaxed distillates and deasphalted oil can be attributed to specific features of their hydrocarbon composition (Tables 2 and 3): high contents of saturated hydrocarbons (47-54% by weight) and comparatively low contents of aromatic hydrocarbons with specific dispersion in the 125-160 interval. Because of the high content of isoparaffins (Table 4), we observe high viscosity indexes (120-140) for the saturated part, which is the main part of the oils. The saturated and aromatic hydrocarbons of the deasphalted oil from the Tengiz crude differ from the corresponding groups of hydrocarbons in the deasphalted oils from large-volume crudes that are used in lube oil production; also, the hydrocarbons from the Tengiz crude have lower viscosities. The heavy polycyclic hydrocarbons with specific dispersion above 160 have high densities and refractive indexes and very low viscosity indexes -a considerable difference from the properties of the corresponding hydrocarbons in major medium-sulfur medium-wax crudes. On the whole, the aromatic part of the Tengiz hydrocarbons includes considerable quantities of naphthenoaromatic hydrocarbons (10-11% by weight), aromatic hydrocarbons (15-16%), and sulfur-containing compounds (12-15 %). The sulfur is present mainly in the form of thiophene derivatives, along with thiocyclanes and sulfides.* The distillates and residue from vacuum distillation of the atmospheric resid of Tengiz crude are also characterized by high contents of resinous compounds, 7-11%, in comparison with the 4-5 % in the analogous products from vacuum distillation of atmospheric resids of other crudes that are used in lube oil production. The hydrocarbon groups that were segregated in these studies were blended to obtain samples characterizing the potential content of oils in both the distillate and residual stocks, with different levels of viscosity. The quality indexes of these products are listed in Table 5.

The Micellar Properties of α,ω-Alkanediammonium Bis(dodecyl sulfate) in Aqueous Solutions

Abstract The micellar properties of α,ω-alkanediammonium bis(dodecyl sulfate) with hydrocarbon chain length (n) from 3 to 6 were studied by conductivity, surfactant ion activity, and fluorescence quenching measurements. The critical micelle concentration (CMC) decreases gradually with increasing n in such a way that ln CMC vs. n plot gives a straight line above n = 3. The binding degree of counterion head group to the micelle remains virtually constant of 0.95 regardless of n studied. The estimated value of −0.36 kT for the transfer free energy per methylene group of counterion from aqueous to micellar environments suggests that the hydrocarbon part of the counterion participates in the weak hydrophobic interaction with micellar core. Although the micelle aggregation number is always larger than those of bivalent metal dodecyl sulfates, it tends to decrease as n increases.

Density fluctuations and rotational isomerization in phospholipid bilayers as studied by ultrasonic absorption spectroscopy

Broadband ultrasonic absorption spectra are discussed for some aqueous solutions of single-walled phospholipid bilayer vesicles. It is shown that the excess absorption found with all samples can be represented by a sum of a Debye-type relaxation term with discrete relaxation time and a Fixman-Kawasaki term. The former term reflects the kinetics of structural isomerization of the hydrocarbon chains. The values of its relaxation time (0.09–0.56 ns) agree with those for pure n-alkanes of comparable length. The latter terms seems to be due to density fluctuations in the hydrocarbon part of the double layer. Fluctuation correlation lengths between 1 and 30 Å result from the analysis of the ultrasonic spectra.

External silane donors in Ziegler‐Natta catalysis. Computerbased molecular model calculations on alkoxysilanes

The electronic factors of external alkoxysilane donors used in modern Ziegler-Natta catalyst systems were estimated by quantum mechanical MNDO (modified neglect of diatomic overlap) calculations on model compounds. The calculated electron densities of oxygen atoms in alkoxy groups were plotted against the experimental activity and the isotacticity of propene polymerization. The steric hindrance and the volume of the compounds were investigated as structural factors important to the polymerization. The results indicate that the performance of the external alkoxysilane donor is affected by both electronic and structural factors. The average electron density around the electron-donating oxygens has some influence on the deactivating power of the donor, but when the hydrocarbon part is sterically large the sterical effects apparently dominate.

Interactions between drugs and nonionic lamellar liquid crystals as studied by dielectric spectroscopy and phase equilibria

Dielectric properties of nonionic lamellar liquid crystals with and without electrolytes and pharmaceutical drugs are reported in the frequency range 40 MHz to 2 GHz. In the aqueous C 12EO 3 lamellae sodium chloride and pilocarpine chloride both give rise to a dielectric dispersion. The nonionic chloramphenicol is completely incorporated into the interfacial region or imbedded into the hydrocarbon part of the model membrane, without giving rise to any dispersion. With added ionic surfactants the membrane surface becomes charged and all systems show a dielectric dispersion. Qualitatively, the findings can be explained by means of counterion behavior at the membrane surface (surface diffusion) or freely diffusing counterions in the aqueous layer. When the lamellar liquid crystalline phase is melted the dielectric dispersions vanish.

Critical temperatures related to monomer composition in mixtures of nonionic surfactants with water

A three-parameter equation is proposed to describe the separation temperatures and hexagonal-mesophase melting temperatures of nonionic n-alkyl oligo-oxyethylene surfactants in water. The temperature of the separation point is well reproduced by the equation starting from a simple balance principle of hydrophilic and hydrophobic parts in the amphiphile monomer. The oxyethylene of the amphiphile contributes a stabilizing effect. This part tends to increase the separation temperature. Increasing the size of the hydrocarbon part lowers the separation temperature. Thus, micelle size or form (spheres or cylinders), or the properties of the critical process (critical exponents) are not primary determinants of the separation temperature. The hexagonal-phase melting temperature depends strongly on the length of the monomer-oxyethylene part; the hydrocarbon part has a smaller effect.

Conformation of condensed polycyclic aromatic hydrocarbons Part III. The molecular and crystal structure of tribenzo [ a,h,rst] phenanthra [1,2,10- cde] pentaphene: a simple analysis of the in-plane distortions due to overcrowding

The crystal and molecular structure of tribenzo [ a,h,rst] phenanthra [1,2,10- cde] pentaphene was determined by X-ray diffraction with final agreement factor R=0.057 for 2842 reflections. The molecule is largely distorted from a planar structure owing to a steric repulsion between the overcrowded hydrogen atoms. The deviations of the atoms from the mean plane of the whole molecule range from −1.78 to 1.52 Å. The molecule has an approximate twofold axis perpendicular to the mean molecular plane and takes a saddle form. A simple analysis of the out-of-plane and in-plane distortions shows that the latter should not be neglected.

Conversion of Light Naphtha into Aromatic Hydrocarbons (Part 1) Kinetic Studies on Hexane Conversion on Zn/H-ZSM-5.

Conversion of light naphtha into aromatic compounds was studied on series of ZSM-5 catalysts loaded with various metal species. Among the catalysts, Zn-, Cd- and Ga-loaded ZSM-5 exhibited. high performances for aromatization of n-hexane. The mechanism of conversion of n-hexane into aromatic compounds over Zn/H-ZSM-5 catalyst was investigated. It is found that aromatization of n-hexane involves dehydrocracking of n-hexane into lower olefins, oligomerization of lower olefins, and dehydrogenation of higher olefins to aromatic compounds. In order to investigate the reaction pathway for aromatization of higher olefins, a series of conversion of n-hexane, 1-hexene, hexadiene, hexatriene, and cyclohexane over Zn/H-ZSM-5, H-ZSM-5, and Pt/H-ZSM-5 were conducted. It is suggested that aromatization proceeds in successive dehydrogenation of higher olefins, and that Zn species play a role to promote formation of hydrogen molecule. On the basis of experimental results, a general reaction model in transformation of light naphtha over Zn/H-ZSM-5 was developed. From results of the kinetic analysis, it is found that promoting the activities for dehydrocracking of n-hexane, dehydrogenation of lower paraffins, and formation of hydrogen molecules may make the catalyst more selective in aromatization of light naphtha.

Influence of stigmastanol and stigmastanyl-phosphorylcholine, two plasma cholesterol lowering substances, on synthetic phospholipid membranes. A 2H- and 31P-NMR study

Cholesterol, stigmastanol, and stigmastanyl-phosphorylcholine (ST-PC) were incorporated into model membranes composed of 1-palmitoyl-2-oleoyl- sn-glycero-3-phosphocholine (POPC) or 1,2-dioleoyl- sn-glycero-3-phosphocholine (DOPC), POPC and ST-PC were deuterated at the lipid headgroup, DOPC at the cis-double bonds. The influence of the three sterols on the motion and conformation of the lipid headgroups and the hydrocation chains was monitored with 2H- and 31P-NMR. All three sterols were freely miscible with the lipid matrix in concentrations of up to 50 mol% without inducing phase separations or nonbilayer structures. However, the molecules exert quite different effects on the phospholipid bilayer. Cholesterol and stigmastanol are largely buried in the hydrocarbon part of the membrane, distinctly restricting the flexing motions of the fatty acyl chains whereas the conformation of the phospholipid headgroups is little affected. In contrast, ST-PC is anchored with its headgroup in the layer of phospholipid dipoles, preventing an extensive penetration of the sterol ring into the hydrocarbon layer. Hence ST-PC has almost no effect on the hydrocarbon chains but induces a characteristic conformational change of the phospholipid headgroups. The 2H- and 31P-NMR spectra of mixed phospholipid/ST-PC membranes further demonstrate that the PC headgroup of ST-PC has a similar orientation as the surrounding phosphatidylcholine headgroups. For both types of molecules the −P-N + dipole is essentially parallel to the membrane surface. Addition of ST-PC induces a small rotation of the POPC headgroup towards the water phase.

External silane donors in Ziegler‐Natta catalysis. An approach to the optimum structure of the donor

AbstractOur earlier work about alkoxysilanes as external donors in high‐activity Ziegler‐Natta catalysts is broadened with studies on the performance of some other oxygen‐containing silane compounds and with some studies on the effect of the structure of the hydrocarbon part of the alkoxysilane compounds: There are new informations about the optimum structure of an external silane‐type donor. The alkoxy group proved to be the best electron‐donating group, whereas the other oxygen‐containing electron‐donating groups tested worked less effectively. In some structures the oxygen atoms were sterically too hindered for effective deactivation. Some increase in the isotacticity was nevertheless observed even with the poor performance donors, which indicates that there could be a population of active centres that are very easy to deactivate. All the para‐substituted alkoxy phenyl silane donors tested gave polypropene with high isotacticity and activity. Therefore, we conclude that the nature of the substituent does not markedly affect the performance of the donor — at least as long as the substituent has not a sterically free electron‐donating group.

Enumeration and classification of benzenoid hydrocarbons Part XIII. Catacondensed dihedral systems

Catacondensed benzenoids with symmetry D 2h are enumerated: those of the first type (i) odd numbers of hexagons (h) up to 49, and those of the second type (ii) even numbers of hexagons up to 52.

Oil and Gas Potential of the Pre-Caspian Depression

The Pre-Caspian depression is one of the largest basin of the Soviet Union measured by sedimentary volume. The area of basin is more than 500,000 km{sup 2}, and the thickness of sedimentary mantle is 20 km in the central part of depression (Central-Pre-Caspian graben). About one-tenth of the initially recoverable hydrocarbons in the Soviet Union hook up with this basin. The sequence of sedimentary mantle of the depression is divided by salt massives of Kungarian age on subsalt (Riphean-Aptian) and supersalt (Upper Permian-Quaternary) structural-formational complexes. The first complex contain a large part (96%) of the initial recoverable hydrocarbons of the region; the remaining resources are in the supersalt complex. Deposits from Middle Devonian to Aptian age are productive in the subsalt complex. More than 30 fields of hydrocarbons (including giant fields: Astrakhan gas-condensate, Tengiz oil and gas-condensate, and Karachaganak oil and gas condensate) have been discovered in these deposits. Most commercial oil and gas reserved have been found in the carbonate reservoirs, but development of capacious terrigenous reservoirs have been predicted for the subsalt complex. Terrigenous reservoirs have received exceptional development in the supersalt complex, but large oil and gas accumulation areas are absent there. Discovered commercial oil fields (aboutmore » 50) have, usually, small reservoirs in this complex. On the whole, the Pre-Caspian depression is characterized by poorly known oil and gas potential. This permits the authors to predict discoveries of new, hydrocarbon accumulations.« less

Zeolite L preperation

Binderless zeolite L particles are prepared by a method in which particles are formed from silica and from 0 to 95 wt % preformed zeolite L crystallites, and the particles are thereafter reacted with an alkaline solution comprising a source of alumina to convert the silica binder to zeolite L. These particles may comprise cylindrical zeolite L crystallites with a mean diameter of at least 0.05 micron in a zeolite L matrix and may be used as catalyst. Also acyclic hydrocarbons are dehydrocyclized and/or isomerized by contacting them at a temperature of from 370° C. to 600° C. with this catalyst incorporating at least one Group VIII metal having dehydrogenating activity to convert at least part of the acyclic hydrocarbons into aromatic hydrocarbons.

Unusual, oil-bearing inclusions in fluorite from Baluchistan, Pakistan

AbstractPhenomenally large (up to 2 mm) oil-bearing and associated brine inclusions in fluorite from carbonate-hosted, epigenetic, fluorite-calcite-(baryte) deposits of the Koh-e-Maran area are investigated using a combination of microthermometry, UV-microscopy and FTIR microspectroscopy. The liquid hydrocarbon phase in primary ‘oil’ inclusions is brown in colour and is dominated by saturated, low molecular weight, aliphatic hydrocarbons.Two types of mixed aqueous and ‘oil’ inclusions occur. Aqueous/oil types represent co-eval trapping of immiscible drops of oil and brine during primary growth. In oil/aqueous inclusions the oil appears to ‘wet’ the aqueous phase resulting in an odd ‘dish-shaped’ meniscus. The oil or liquid hydrocarbon part of the inclusion is primary but the aqueous part is thought to represent a secondary infill. The fluid inclusion evidence suggests that fluorite precipitated from a dilute (3.5 wt.% NaCl) brine at temperatures around 110–140°C in the presence of an immiscible liquid hydrocarbon phase dominated by saturated, light hydrocarbons. This ‘oil’ was present as an emulsion in the aqueous fluid and the phenomenal size of the inclusions is thought to reflect the large droplet size in the emulsion. Infiltration of a more saline, calcium-enriched brine into pre-existing oil inclusions resulted in complex oil-water inclusions showing a reversal in the nature and shape of the oil-water interface due to the presence of unspecifed surfactants in the brine which affected the wetting characteristics of the oil.The homogenization temperatures and the presence of liquid petroleum inclusions are characteristic of Mississippi Valley-type (MVT) and manto-type fluorite deposits in many other parts of the world.

Carbon-13 cross-polarization magic-angle-spinning NMR study on the chain packing in anhydrous and hydrated DL- and L-dipalmitoylphosphatidylcholine

With I3C cross-polarization magic angle spinning (CP-MAS) NMR it is demonstrated that the anhydrous forms of DL- and L-DPPC show pronounced packing differences in both the headgroup region and the hydrocarbon part of the bilayer. In DL-DPPC the acyl chains and more specifically their end groups are more closely packed than in the L modification. The anhydrous L- and DL-DPPC structures show a completely different behavior toward the addition of 1 equiv of water. DL-DPPC is far less hygroscopic and forms small domains of dihydrated and anhydrous DPPC as was concluded from the combined results of the NMR and a DSC study. The dihydrated form of DL-DPPC is arranged according to a similar structure as is observed for anhydrous L-DPPC. On the other hand, L-DPPC did not show any packing changes in the acyl chains on going from the anhydrous state to the hydrated forms. These results reveal that stereospecific interactions can be responsible for different lipid packing modes and hence in their behavior toward the uptake of water.

Thermal analysis and mass spectra of sulfur-containing iron carbonyl complexes

1. The activation energy for the thermal decomposition of complexes with Fe2(CO)6S2 frameworks amounts to 103–144 kJ/mole. 2. Decarbonylation and splitting off of the hydrocarbon part of the molecule is the general pattern of behavior of iron carbonyl compounds with sulfur ligands on heating and under electron bombardment. 3. In complexes containing a norbornadiene fragment, a reverse Diels-Alder reaction takes place under electron bombardment, in addition to splitting off of norbornadiene.

Distribution of K , the Number of Kekulé Structures in Benzenoid Hydrocarbons Part IV. Benzenoids with 10 and 11 Hexagons

An approximate asymptotic formula is derived for the number of normal benzenoids. For this category and h (number of hexagons) = 10 and 11 all numbers of Kekulfe structures were computer and systematized.