Akhilesh Kumar Bhatnagar

Chemical structure of bitumen-derived asphaltenes by nuclear magnetic resonance spectroscopy and X-ray diffractometry

Abstract Asphaltene samples obtained from bitumen processed at three Indian refineries were characterized for chemical composition and structure by nuclear magnetic resonance (n.m.r.) spectroscopy and X-ray diffractometry (XRD). The average structural parameters were obtained by combined 1H, 13C and DEPT spectral editing techniques. New equations were used for the estimation of n.m.r. average structure parameters. The macrostructure and crystalline parameters of these samples were obtained by XRD. A combined n.m.r. and XRD procedure was used to estimate the size of the average aromatic structural unit. Asphaltenes from one of the bitumens (ASP-D) was found to have different structural parameters from those of the asphaltenes from the other two bitumens. The number of aromatic rings per unit sheet in ASP-D was eight, compared with 13 for both ASP-M and ASP-H. XRD data indicated that the aromatic sheets are randomly oriented in ASP-D. The structural parameters allowed a model structure of the asphaltenes to be constructed.

Hydrocarbon characterization of hydrocracked base stocks by one- and two-dimensional n.m.r. spectroscopy

Abstract Characterization of a number of unconventional catalytically hydrogenated base stocks of low aromatic content and high viscosity index is discussed in terms of hydrocarbon types, with emphasis on isoparaffinic structural analysis. The analysis was carried out using multipulse one- and two-dimensional n.m.r. spectral techniques. Various spectral regions characteristic of different structural units were assigned based on DEPT, 2D COSY and HETCOR spectroscopy. The presence of eleven different types of branched structures was established. The analysis of 1D and 2D n.m.r. spectra further provided reliable average structural parameters. The aromatic carbon (C A ) content of these samples was found to be

Synthesis and performance evaluation of O, O-dialkylphosphorodithioic disulphides as potential antiwear, extreme-pressure and antioxidant additives

Abstract The ashless antiwear/EP additives based on phosphorodithioic acids are preferred to their heavy metal complexes, due to operational problems and enviromental restrictions being enforced in many countries. Four O, O-dialkylphosphorodithioic disulphides with varying alkyl chain length from C5 to C10 have been synthesized and their antiwear, EP and antioxidant performance examined vis-a-vis a commercial ZDDP in a mineral base oil. The synthesized products have been found to exhibit appreciable antiwear and antioxidant properties and mild EP performance, which are comparable to that of commercial ZDDP.

Prediction of biodegradability of mineral base oils from chemical composition using artificial neural networks

Abstract Biodegradability studies of base oils are important for designing and development of environment-friendly lubricants. Biodegradability of base oils and lubricants have been determined by a large number of test methods. Among these, the 21 day test developed by Coordinating European Council and designated as CEC-L-33-A-93 has been accepted worldwide. In this work, artificial neural network (ANN) technique has been used to construct mathematical models for predicting biodegradability of base oils based upon their chemical composition, viscosity and viscosity index. The chemical composition has been determined either by NMR or mass spectrometry and two models have been developed. Thirty-one base oils of different origin and processing schemes, and their blends with polyalphaolefin (PAO) were analyzed for chemical composition and biodegradability. Part of the data was used for developing the models using backpropagation ANN, while the remaining data were used for evaluating the predictive ability of the models (correlation coefficient, R 2 ∼0.97). The models can serve as useful tools for screening base oils before subjecting them to 21 day biodegradability test.

Additive-additive interactions : search for synergistic FM-EP-AW composition

Abstract A recent trend and need is towards formulating energy efficient lubricants as fuel efficiency has become a critical component of industrys operating efficiency. However, compatibility of friction modifiers (FM) with existing additives, specially surface-active types, needs to be examined beforehand. The effect of oil-soluble commercial organomolybdenum compounds on the extreme pressure (EP) and antiwear (AW) properties of most commonly used S-containing EP/AW agents has been investigated on a four-ball machine. While mostly complementary and exclusory interactions were observed in some cases graded response was also noticed. Based on this extensive study, involving three oil-soluble organomolybdenum FM and four EP/AW agents of varying chemistries, the most synergistic FM-AW-EP combination was identified. The selected combination, when incorporated into a fully formulated industrial gear oil formulation, resulted in marked enhancement in EP/AW properties and a substantial improvement in frictional characteristics.

Molybdenum dialkylphosphorodithioates: synthesis and performance evaluation as multifunctional additives for lubricants

Abstract Phosphorodithioate complexes of various metals are used as lubricant additives to impart anti-wear, anti-friction, anti-oxidant and extreme-pressure properties in lubricating oils. Four molybdenum dialkylphosphorodithioate (MoDTP) complexes with varying alkyl chain length from C5 to C10 have been synthesized and their anti-friction, anti-wear and anti-oxidant performance examined vis-a-vis a commercial MoDTP in a mineral oil, base oil and finished engine oil. The synthesized products have been found to exhibit appreciable anti-friction, anti-wear and anti-oxidant properties, which are comparable to that of commercial MoDTP.

Antiwear/extreme pressure performance of graphite and molybdenum disulphide combinations in lubricating greases

Abstract Additive-additive interaction of MoS 2 and graphite has been investigated for the synergistic/antagonistic effect on antiwear and extreme pressure (EP) characteristics of two greases, i.e. lithium and organo clay base. In general, the combinations have exhibited synergism. The level of synergism has been found to depend on the nature of the base grease and the ratio of the two components in the combination.

Gas chromatographic determination of residual hydrazine and morpholine in boiler feed water and steam condensates

SummaryHydrazine, an oxygen scavenger in boiler water, was derivatised to the corresponding acetone azine and determined at the ng ml−1 level by gas chromatography. Morpholine, a corrosion inhibitor used in steam boilers, was estimated either directly (if >2.0 μg ml−1) or by quantitative preconcentration (0.1 ng – 2.0 μg ml−1). To obtain symmetrical peaks for these amines, the column packing was coated with KOH. Use of a nitrogen-specific detector improved accuracy of estimation of hydrazine and morpholine, giving a RSD of 1.9–3.6%. Chromatographic analysis of these amines in boiler feed water and steam condensate samples collected from boilers servicing a petroleum refinery is described. Environmental safety regulations calls for monitoring of hydrazine and the methods developed can easily be adapted for this purpose.

Sulphur-phosphous components in gear oils: part 1, oxidation stability studies by 31P-NMR spectroscopic techniques

Abstract In the present investigations, the mechanism of oxidation stability of sulphur and phosphorus-based additives such as S-alkyl O,O-dialkyl phosphorodithioate, alkyl amine salt of dialkyl dithiophosphoric acid, dialkyl hydrogen phosphite and zinc dialkyl dithiophosphate used in lubricants has been studied by liquid and solid state 31 P/ l H-NMR spectroscopic techniques. These techniques have enabled to monitor the complex changes that occur during oxidation at different intervals during long duration oxidation tests and provide qualitative and quantitative information of products formed during degradation of S–P based additives. The nature of both soluble and insoluble products of decomposition has been /determined. The studies have revealed few important aspects regarding thermal stability of these additives. The ashless S-alkyl O,O-dialkyl phosphorodithioate have better thermal oxidative stability and retain their identity for longer period compared to other similar ashless additives and zinc dialkyl dithiophosphates. The loss of additives during oxidation is 12% in case of S-alkyl O,O-dialkyl phosphorodithioate compared to other mentioned additives (40–100%) during 64 h of heating at 165 °C in the presence of air and catalyst. The decomposed products are also solublised in case of S-alkyl O,O - dialkyl phosphorodithioate and dialkyl hydrogen phosphite, and small amount of solids are formed compared to other additives. During oxidation the main components are being converted into more complex insoluble polyphosphates. The nature of soluble and insoluble products of decomposition as a result of thermal degradation are similar irrespective of the types of additive used. The mechanism of degradation and subsequent composition and structure of products formed has been discussed in detail. These studies will facilitate correlation of the structure and performance of these additives in lubricants.

DIRECT ESTIMATION OF AROMATIC CARBON (Ca) CONTENT OF BASE OILS BY 1H-NMR SPECTROSCOPY

ABSTRACT A direct and fast method for the estimation of aromatic carbon content (Ca) in base oils produced through different processes has been developed based on 1H-NMR spectroscopy. The identity of the complex and overlapped 1H-NMR region of 2.0−3.5 ppm, which constitutes resonances from α-substituents (−CH, −CH2 and −CH3 groups), has been revealed by 2D HetCor spectral analyses. This information has facilitated the estimation of quaternary (Cq) and bridgehead (Cb) aromatic carbons from 1H-NMR spectrum using the derived equations. The complete and unambiguous assignment of the 1H-NMR spectrum led to the estimation of Ca content of base oils. The classical Brown-Ladner (BL) equation for Ca estimation has been modified by taking the actual contribution of −CH, CH2 and CH3 groups, instead of using average values. The proposed 1H-NMR, and the modified BL methods correlate very well (R2 = 0.97) with the standard 13 C-NMR method for Ca estimation.