Himmat Singh

Influence of base oil refining on the performance of viscosity index improvers

Abstract The effect of three viscosity index (VI) improvers of different chemical type on kinematic viscosity at 98.9°C was studied in lube base stocks from Darius crude oil. These base stocks differed in their degree of refining and finishing, i.e. whether they had been hydrofinished or clay treated. They covered a wide range of viscosities from spindle oil to heavy neutral with VI from Low VI stock to Extra High VI stock. The thickening effect at high temperature and the viscosity temperature relationship were evaluated. Differences observed in the performance of VI improvers have been explained on the basis of the variation in specific viscosity and of the changes in the polymer coil dimensions in terms of the reduced viscosity as a function of temperature following Mullers criteria based on the chemistry of lubricating oil base stocks.

Low field anisotropic colossal magnetoresistance in Sm0.53Sr0.47MnO3 thin films

SSMO5347 thin films (thicknesses ~200 nm) were deposited by on-axis dc magnetron sputtering on the single crystal LSAT (001) substrates. These films are oriented along the out of plane c-direction. The ferromagnetic and insulator-metal transition occurs at 96 K and 91 K, respectively. The magnetization easy axis is observed to lie in the plane of the film while the magnetic hard axis is found to be along the normal to this. The magnetotransport of the SSMO films, which was measured as a function of angle (theta) between the magnetic field (H) and plane of the film, shows colossal anisotropy. Magnetoresistance (MR) decreases drastically as theta increases from 0 degree (H//easy axis) to 90 degree (H//hard axis). The out-of-plane anisotropic MR (AMR) is as high as 88 % at H=3.6 kOe and 78 K. The colossal anisotropy has been explained in terms of the magnetic anisotropies at play and the magnetic domain motion in applied magnetic field.

Fullerenes: Synthesis, separation, characterization, reaction chemistry, and applications -- A review

The recently discovered third allotrope of carbon, the fullerenes, are a subject of very active research, particularly for chemists. They have a closed-cage structure, made by interlocking pentagonal and hexagonal panels, and are the only soluble form of carbon. In this review an attempt has been made to summarize ongoing fullerene research. The review covers methods of fullerene production and separation, mechanisms leading to closed-cage structure formation, structural characterization, reaction chemistry, and applications of this novel material. The emerging directions of research are also discussed.

Structural changes during hydrogenation of lube distillates: n.m.r. studies

13C and 1H n.m.r. spectra of raw and hydrogenated lube distillates of intermediate and heavy viscosity ranges along with their aromatic concentrates were recorded. Structural changes occurring during hydrogenation were derived and used to explain the reactions taking place. Besides hydrogenation of aromatics, hydrodesulphurization and hydrodenitrogenation are also seen under the conditions used. While some hydrocracking/dealkylation of aromatic structures is observed in the intermediate viscosity lube distillate, conversion of higher condensed aromatics into hydroaromatics is predominant in the heavy viscosity lube distillate.

Tribological behaviour of base oils and their separated fractions

Abstract The tribological behaviour of five base oils and their chromatographically separated hydrocarbon type fractions was investigated during steel-steel tribocontact using a fourball machine. It was found that the clay finished base oils, in comparison with the hydrofinished stocks, showed better wear behaviour owing to partial hydrodesulphurization which occurred during refining. The parent base oils gave higher wear rates than the saturate and monoaromatic fractions separated from the clay finished base oils. All the test data are analysed and discussed, and the observations are supported by scanning electron microscopy. Possible correlations between the lubrication properties of the stocks and the average number of alkyl carbon atoms per alkyl substituent and the molecular weight are reported.

Tribological behaviour of some hydrocarbon compounds and their blends

Abstract Friction and wear characteristics of some individual hydrocarbon compounds and their blends during sliding of steel on steel were investigated using a four-ball machine. It was found that the isoparaffins exhibit better lubrication properties than do the n -paraffins, while aromatics give higher friction values and wear. Studies with the blends of hydrocarbons showed that blends containing the same hydrocarbon-type molecules of different carbon numbers have lower coefficient of friction and wear scar diameter than shown by the individual hydrocarbons of the same series. Blends containing different hydrocarbon-type compounds also show a beneficial synergistic effect.

PHYSICO-CHEMICAL AND COMPOSITIONAL ASPECTS OF BITUMEN BEARING CRUDES AND THEIR INSTRUMENTAL CHARACTERISATION

Abstract In India the production of bitumen is primarily based on middle-east crude oils which normally have a right balance of bitumen constituents (i.e. asphaltenes and maltenes). In general, bitumens obtained from such crude oil sources have a good balance of rheological and physico-chemical properties at both low and high temperatures. Bitumen is a complex mixture consisting of compounds ranging from non-polar aliphatic and naphthenic hydrocarbons to highly polar aromatic molecules containing heteroatoms such as oxygen, nitrogen, and sulfur; and, several attempts have been reported to fractionate and characterise bitumens into broadly defined compound groups. The separation method adopted in the present study is based on the polarity of the constituent compounds comprising the bitumen. The separated groups of compounds which progressively increase in their polarities are saturates, aromatics, resins and asphaltenes. In the present study three important (middle-east) bitumen bearing short residues have...

Impact of Growth Conditions on the Nature of Magnetism and Magnetotransport of Sm

The impact of growth conditions on the magnetic and electrical transport properties of oriented polycrystalline Sm0.55Sr0.45MnO3 thin films prepared on nearly lattice matching LSAT(100) single crystal substrates by nebulized spray pyrolysis has been studied.

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Abstract Some selected petroleum based feedstocks have been characterized by 1H and 13C NMR spectroscopy for their possible use as carbon black feedstock (CBFS). Feedstocks studied are pyrolysis tars, clarified oils, aromatic extracts and vacuum residue. Analysis of average structural NMR parameters show that pyrolysis tars because of their being highly aromatic in character (high BMCI) are the most suitable feedstock for carbon black. Aromatic extracts rank the next. Clarified oils of Indian refinery origin needs further processing due to middle distillate mode refining severity.

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Abstract Bitumen is a fine dispersion of high molecular weight hydrocarbon species, known as asphaltenes, in a medium called maltenes, which in turn consists of resins and oils. Air blowing is an extensively used process to upgrade and achieve specifications of final bitumen product. The air blowing process is accompanied by hardening of bitumen, with corresponding changes in chemical composition thereby yielding product having acceptable consistency and temperature susceptibility. The main reactions accompanying air blowing are polymerization of unsaturated species, dehydrogenation, and condensation. The asphaltenes fraction generally acts as a filler in bitumen, whereas resins impart adhesive properties due to inherent unsaturation present in their cyclic group and oils are responsible for the fluidity. Hence, the relative proportion of these components plays a significant role in deciding upon physico-chemical characteristics of the final blown bitumen. Air blowing as such is a time consuming process. Depending upon the grade of final product, many solid catalysts are used to increase the rate of reaction and improve physico-chemical properties of bitumen. FeCl3 is known to be one of the most effective and least expensive catalysts in this process. This paper presents the results of an extensively carried out experimental study in a batch reactor. Blends of Bombay High short residue in admixture with Iran, Arab mix and Dubai short residues have been studied in detail. Kinetics of air blowing process of bitumen deduced from physical and chemical properties, measured during the process is described. The use of catalyst, enabled the reaction time to reduced significantly and increases the rate of reaction about three to four times depending upon feed stock composition without affecting the properties of bitumens. Kinetic parameters of the model used to describe the process are presented quantifying the effect of catalyst in accelerating the air blowing reactions.