Naphthenic Structures Research Articles

Structural Analysis of Petroleum Deasphalted Oils and Their Thermal Cracking Properties.

To provide an insight into the relation between structural characteristics of petroleum heavy oils and their thermal cracking properties, structural analysis of three kinds of deasphalted oils (DAO) by chromatographic separation, followed by 1H and 13C NMR and Curie-point pyrolysis of the oils and their fractions (S: saturates, A: aromatics, and P: polar compounds), was carried out. The oils employed were prepared from the vacuum residues of two Indonesian crudes (Minas and Duri) and an Arabian mixture (AL/AM) using pentane as solvent. The results of structural analysis suggested that aliphatic portion of Minas and Duri-DAO consisted mainly of straight paraffins, whereas a considerable portion of AL/AM-DAO consisted of naphthenic structures. The Curie-point pyrolysis at 670°C indicated that, irrespective of the oils, the amount of coke from their fractions decreased following the order P>A>S. It was also found that the coke formation from each P or A fraction could be suppressed by adding the saturate fraction, AL/AM-DAO-S, whereas in the case of using Minas- or Duri-DAO-S, no effect of the addition was observed. These results suggest a possibility that unique properties of AL/AM-DAO-S observed may be due to the presence of a considerable amount of active hydrogen in the naphthenic components.

Structural features of Alberta oil sand bitumen and heavy oil asphaltenes

Ru ion catalyzed oxidation (RICO) has been used to probe the structural details of asphaltene molecules from Athabasca bitumen. The ability of RICO to remove nearly quantitatively aromatic carbons while leaving aliphatic and naphthenic structures essentially unaffected has been exploited for the quantitative determination of the following structural features : (1) the distribution of n-alkyl chains attached to aromatic carbons with respect to chain length, total number of n-alkyl chains and the number of carbon atoms in them; (2) the distribution of polymethylene bridges connecting two aromatic units with respect to bridge length, total number of bridges, and the number of carbon atoms in them; (3) the fractional amount of total sulfur present as saturated sulfides

Mesophase Pitch Derived from Isotropic Anthracene Pitch Produced Catalytically with HF/BF3

Abstract The thermal preparation of the mesophase pitch from the isotropic anthracene pitch produced catalytically from anthracene with HF/BF3 was studied through both single- and two-stage heat-treatments. The single stage under vacuum provided a mesophase pitch (SMAP-2) of 100% anisotropy and excellent spinnability at yield as high as 59%. The present mesophase pitch maintained the naphthenic structure to some extent, although thermal preparation, which tends to induce dehydrogenative aromatization, was employed. The two-stage preparation, comprising heat-treatments under pressure (2.1 MPa) and then under vacuum (1 Torr, 1 Torr≈ 133.322 Pa) increased the yield of the mesophase pitch to 64%. The resultant mesophase pitch (TMAP) of 100% anisotropy and excellent spinnability carried fewer aliphatic groups than that of the single stage. SMAP-2 was sufficiently stabilized for 30 min at 300 °C, superior to that of the mesophase pitches derived from FCC-DO and the isotropic naphthalene pitch. The complete stabilization of TMAP with a smaller aliphatic structure was achieved within a slightly longer time of 45 min. The number of aliphatic groups is closely related to the stabilization reactivity. It is worth noting that the present mesophase pitches prepared from the isotropic anthracene pitch retained the structure of the starting pitch to an extent which depended on the procedure, influencing the stabilization reactivity.

石炭液化用触媒に関する研究 ＳＲＬの水素化分解反応に対する各種触媒の接触作用の比較

The hydrogenolysis of Solvent-Refined Lignite (SRL) obtained from Morwell coal was conducted in the presence of four kinds of catalysts with tetra-lin or creosote oil as solvent at 693 K. The products were separated into five compo-nents and each of them was analyzed by 1H-NMR. With Adkins' catalyst, hydrogena-tion of aromatic nuclei predominates over cleaving linkages between the structural units. The catalysis of Fe2O3+ S is similar to that of Adkins' catalyst but the former is less active. MoO3-TiO2 is the most powerful catalyst for the hydrogenolysis of SRL among the catalysts employed here and it seems to contribute to cleaving linkages be-tween the structural units. The catalysis of MoS3-Al2O3 is similar to that of MoO3-TiO2 in the presence of solvent. Asphaltenes and Insolubles decrease with reaction time. However, after a certain composition of the products reaches, decom-position of naphthenic structures seems to occur accompanied by its dehydrogenation. It was concluded that the specific behavior of each catalyst for the hydrogenolysis of the SRL agrees with that for the reactions of the model compounds.

STRUCTURAL GROUP ANALYSIS OF PRODUCTS FROM TWO-STAGE LIQUEFACTION OF HIGHVALE COAL

ABSTRACT Products from liquefaction of Highvale Coal (Alberta. subbituminous) in anthracene oil and recycled product, with iron oxide catalyst, were studied using a structural group analysis method. The various functional groups were determined using a combination of proton NMR. carbon-13 NMR. IR. elemental analysis and nitrogen titration analysis. The liquefaction reactions in anthracene oil and in recycled product oil were compared on the basis of three solvent quality Indices and the predominant structural groups in the resulting liquids. The results show that major structural changes occur at both stages of liquefaction. Processing in anthracene oil showed much greater structural changes than liquefaction in the recycled product. The structural profiles Indicated a reduction in aromatic structures and a dramatic increase in aliphatic and naphthenic structures during processing in anthracene oil. These changes were attributed to the hydrogenation of aromatic structures and the dissolution of aliphatic ...

Carbonization in the tube bomb leading to needle coke: III. Carbonization properties of several coal-tar pitches

Carbonization properties of several coal-tar pitches of different origins were studied, by using tube bomb, to correlate their analytical characteristics with their carbonization properties and to find their respective optimum carbonization conditions for the production of excellent needle coke. The pitch rich in naphthenic structure produced an excellent needle coke of low CTE and uni-axially arranged flow texture under a wider range of carbonization conditions, whereas the pitches of high oxygen and alkyl contents or of very high aromaticity gave cokes of larger CTE under the standard carbonization conditions of 500 °C, 8 kg/cm 2, because of more mosaic texture or poor uni-axial orientation in the resultant cokes. However, the two kinds of poor pitches were found to produce better cokes under their respective appropriate conditions. The former one did at a slightly lower carbonization temperature of 480 °C and the latter one did under a lower carbonization pressure of 4 kg/cm 2. A lower temperature allowed the development of bulk mesophase through the moderation of carbonization reactions for the former reactive pitch. The lower pressure improved uni-axial arrangement of mesophase molecules at the solidification stage through the sufficient gas evolution of good timing for the latter highly aromatic pitch. The higher pressure of carbonization delayed the solidification to be off-timing to the gas evolution. The mechanism of needle coke formation was discussed to explain the respective optimum conditions for the pitches of different analytical characteristics.

Study on the aluminium chloride-modification for heavy fraction of light diesel oil using tandem mass spectrometry

Tandem mass spectrometry was used to follow the low temperature catalytic modification of the diesel oil heavy fraction in the presence of aluminium chloride. The molecular distribution from chemical ionization mass spectroscopy (c.i.m.s.) of raw feedstock ranges from 150 to 250, with an average molecular weight of 219 (v.p.o.). That of the finally modified pitch ranges from 200 to 800, mainly concentrated between 200 and 500 with v.p.o. molecular weight of 452. The m.s.-m.s. fragmentation analysis of three dominant, characteristic protonated parent ions m z 207, 373, 385, showed ethyl phenanthrenes (-anthracenes), dimers from phenanthrene (anthracene) and C 1-phenanthrene with substantial naphthenic groups, dimers from C 1-phenanthrenes and copolymers from hexahydropyrene with phenanthrene, chrysene with C 2-naphthalene, etc., respectively, to be the main structural types of these parent mass numbers. This modified pitch material, with a characteristic low degree of condensation and extensive naphthenic structures proved to be suitable for transformation into mesophase pitch with high fluidity and a large domain-type anisotropic texture.

Liquefaction reaction of coal: 2. Structural correlation between coal and its liquefaction products

The structural correlation between coal and its liquefaction products has been examined using cross-polarization, magic angle spinning (CP/MAS) 13C n.m.r. and field ionization mass spectrometry (f.i.m.s.). The CH 2/aromatic carbon ratios of all solid products (asphaltene, preasphaltene and residue) were close to the corrected +CH 2/aromatic carbon ratio for the coal. This suggests that the ring structure of the structural unit of each solid product is essentially similar to that of the parent coal, except for a difference in the degree of polymerization of the structural units. The CH 2/aromatic carbon ratios of aromatic ring-type oil fractions also correlated with the corrected ratio for the coal, although they were larger. The z series distribution obtained from the f.i.m.s. of oil fractions revealed that coal with a higher CH 2/aromatic carbon ratio produced an oil rich in naphthenic structures.

Pyrolysis of naphthenic hydrocarbons

Summary 1. Pyrolysis of individual naphthenic hydrocarbons — cyclohexane, decalin, adamantane and naphthenic concentrates containing polycyclic naphthenic hydrocarbons was studied using a continuous micro-apparatus. 2. Polycyclic naphthenic hydrocarbons from petroleum were demonstrated to form during pyrolysis lower olefins and monocyclic aromatic hydrocarbons, ethylene from naphthenic structures formed about 80 wt.% of the total yield. Alkylbenzenes made up some 53 wt.% of the pyrolytic resin from the naphthenic concentrate. The addition of polycyclic naphthenic hydrocarbons to petroleum fractions does not “inhibit” the formation of lower olefins during pyrolysis. 3. Mass spectrometry revealed that the naphthenic hydrocarbons in the naphthenic concentrate have a sterane structure and contain two-to-three C 1 -C 2 alkyl substituents as well as a C 5 -C 8 substituent chain.

Characteristics of naphthenic and paraffinic hydrocarbons of residual oil from west Siberian crudes

This article examines the naphthenic/paraffinic hydrocarbons segregated by liquid chromatography from a residual oil after removal of the resins and solid hydrocarbons. The studied hydrocarbons were fractionated on the basis of molecular weight (by molecular distillation) and on the basis of the content of rings (by thermal diffusion separation in a laboratory column). The results of mass-spectrometric analysis indicate that the first fraction consists mainly of isoparaffins and naphthenes with few rings. The polycyclic condensed naphthenes are concentrated in the last fraction. The content of isoparaffins drops off and the content of condensed polycyclic naphthenic structures increases from the second fraction to the next to the last. It is concluded that the naphthenic/paraffinic hydrocarbons of the residual oil from mixed West Siberian crudes have a relatively narrow composition and therefore have similar physicochemical properties.

Naphthenic/paraffinic hydrocarbons of residual lube stock from West Siberian crudes

The lube stocks from West Siberian crudes are characterized by high contents of aromatic hydrocarbons and by high viscosity indexes of the naphthenic/paraffinic and aromatic hydrocarbons. Mass spectrometric analysis showed that isoparaffins account for one-third of the total naphthenic/paraffinic hydrocarbons. The study showed that the naphthenic/paraffinic hydrocarbons of the residual lube stock from West Siberia crudes, even with a variation of molecular weight over broad limits, are relatively uniform in composition. They consist mainly of isoparaffinic and monocyclic and noncondensed naphthenic structures.

The nature and origin of harbolite and a related asphaltite from southeastern Turkey

Bitumens solvent extracted from harbolite and Avgamasya asphaltite after treatment with acid under reducing conditions were separated by solvent partition and column chromatography. The principal fractions, together 77 and 82% of the bitumens, were sulphur-rich neutral oil and asphaltene fractions which were shown by size-exclusion chromatography and spectroscopy, particularly 1H and 13C nuclear magnetic resonance, to consist of high-molecular-weight structures carrying alkyl (some with long chains) and naphthenic structures. The alkane fractions were analysed by high-resolution gas chromatography and contain n-alkanes, isoprenoids and triterpanes. The asphaltite bitumens are classified as aromatic-asphaltic oils derived by alteration during migration of aromatic intermediate oils originating from open-water marine sediments laid down in an anoxic environment.

D.c. electrical conductivity of Green River oil shales

The recent interest in the kinetics and mechanistic aspects of the thermal decomposition of oil shale kerogen1 derives largely from its importance as an alternative energy source to petroleum. In spite of considerable research effort, how oil shale kerogen decomposes to gaseous and liquid hydrocarbon fuels is still not fully understood1. The present study considers the d.c. electrical conduction behaviour of Green River oil shales. The observed trends in the electrical behaviour of these materials are correlated with a two-step decomposition model in which the rate-determining processes are shown to be (1) breakdown of an outershell polar bridge structure with an activation energy of 15 ± 2 kcal mol–1 (180–350°C) and (2) cleavage of an inner core naphthenic structure also involving polar groups with an activation energy of 35 ± 3 kcal mol–1 (350–500°C). These structural changes are shown to correspond to the chemical transformation of kerogen to liquid and gaseous hydrocarbons through a bitumen intermediate. Although the present data pertain to Green River oil shales in particular, the observed trend of charge transfer mechanisms in the thermal decomposition behaviour of thermally unstable materials may be indicative of how thermal and electrical properties of all solid materials in general are closely coupled. The common mechanistic origin identified in the present study for the processes of thermal decomposition and electrical conduction, offers the possibility of improving the thermal stability characteristics of a solid by appropriate changes in the electric field surrounding it.

Hydrocarbon composition of fractions obtained by thermal diffusion of the isoparaffin-naphthene portion of Korobkov gas oil distillate

1. Thermal diffusion fractions of the isoparaffin-naphthene portion of the gas oil distillate from Korobkov crude were investigated by infrared and mass spectrometry. 2. The refractive index and density of thermal diffusion fractions differ sharply for each 50°-cut, but the molecular weights are similar. 3. An increase in the degree of condensation of naphthenic structures and a decrease in isoparaffinic hydrocarbon content is observed with progressing thermal diffusion fraction number. 4. Mono- and dicyclic hydrocarbons constitute the main bulk of naphthenic structures. 5. The longest chains of the type R-(CH2)n-CH3 belong most probably to isoparaffinic structures. 6. The prevalence of sixmembered rings over fivemembered rings is observed in the investigated fractions of Korobkov crude.

Quantitative Relationship between Mineral Oil Composition and Elastomer-Extender Interaction Parameter

Abstract Among the synthetic rubbers, the styrene-butadiene elastomers (SBR) extended with oil have grown more and more important in these last years. These elastomers are obtained by masterbatching an SBR latex of high Mooney viscosity with a mineral oil before coagulation, the oil content normally ranging between 37.5% and 50%. The mineral oil can be classified as predominantly paraffinic, naphthenic, or aromatic according to the ratio of carbon atoms involved in the paraffinic, naphthenic, or aromatic structures. The oil composition greatly affects both the processing and the final-product properties of the extended elastomer. It is well known, for instance, that SBR extended with paraffinic oil is more critical in processing than when extended with naphthenic or aromatic oils, and, on the other hand, that SBR extended with paraffinic oil shows better resistance to the discoloration caused by exposure to light. Leaving the long list of the effects on elastomeric properties of oil composition to the many papers existing on this subject, we prefer to deal here with a very important subject not very much studied on any quantitative basis until now. The oil composition affects many characteristics of the polymer because it brings controllable variation to the physical-chemical interaction between the polymer and the extender, measurable by the Flory-Huggins interaction parameter and strictly related to the more commonly known compatibility meaning. This work deals with the quantitative relationship between the composition of various mineral oils (determined by a well-known method) and their interaction parameters with SBR which greatly affect the main properties of the extended elastomer and which we determine by a swelling measurement of the crosslinked elastomer.