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

Sarpal, A. S.; Kapur, G. S.; Chopra, Anju; Jain, S. K.; Srivastava, S. P.; Bhatnagar, A. K.

doi:10.1016/0016-2361(96)87624-1

Cited by 53 publications

(58 citation statements)

References 16 publications

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“…Recently, heteronuclear correlated two-dimensional (2D) NMR methods have been shown to be an excellent tool for the identification of oil fraction substructures. 2 However, the use of 2D NMR spectra for quantitative analysis is not straightforward. The major sources of interference on the correlation signal integrals are variation in the values of heteronuclear couplings, the number and magnitude of J H,H couplings and relaxation effects during the pulse sequence.…”

Section: Introductionmentioning

confidence: 99%

Quantitative determination of aliphatic hydrocarbon compounds by 2D NMR

Koskela

Väänänen

2002

Magnetic Reson in Chemistry

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Quantitative analysis of complex mixtures by NMR is often hampered by heavily overlapping signals in 1D1 H or 13 C spectra. To resolve the overlap problem, we have been looking at the possibilities of using heteronuclear correlated 2D NMR methods for quantification. In this work, we applied 2D INEPT to analyze mixtures of tetradecane and squalane, which represent typical substructures of lube oil fractions. The factors affecting correlation peak volumes, namely the polarization transfer delays within pulse sequence, multiplicity of CH n group and the magnitude of 1 J .C,H/ couplings were taken into account by product operator formalism calculations. The results indicate that if absolute precision in quantification is not essential, the current approach can be used for the quantitative analysis of the molecular composition of complex mixtures when conventional 1D NMR methods fail.

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Section: Introductionmentioning

confidence: 99%

Quantitative determination of aliphatic hydrocarbon compounds by 2D NMR

Koskela

Väänänen

2002

Magnetic Reson in Chemistry

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“…2-6 It has been proved that not only the total aromatics, paraffins and naphthenes influence these properties, but also their types, nature and their relative distribution in a particular grade of base oil are equally important. 1,2,4 Groups II and III base oils are having specific types of CH 3 branching at position numbers 2, 3 and 4 and at the centre of the carbon chain at position number 6 or 7. The structures having methyl branching at the terminal end of the chain provide higher molecular mobility or flexibility at low temperature compared with structures having branching at the centre of the chain, which impose mobility restrictions.…”

mentioning

confidence: 99%

“…The CH 3 branching is non-uniformly distributed along the carbon chain in the case of solvent refined group I base oil. 1,2,[5][6][7] The distribution of CH n (n = 1 to 3), normal and isoparaffin contents and types of isoparaffins determine the low and high temperature rheological properties of the base oils. [2][3][4]6,8 For example, the presence of high content of S 2 and S 3 structures decreases the ppt without much affecting the VI.…”

mentioning

confidence: 99%

“…branches at the centre of the molecules, definitely increase the VI. 1,2,4 The better low temperature properties such as ppt and CCS are achieved by the presence of lower amount of normal paraffins and higher amount of isoparaffins with the methyl branching on the centre, i.e. the presence of long side chain and short chain on the terminal carbon of the alkyl chain.…”

mentioning

confidence: 99%

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Correlation of structure and properties of groups I to III base oils

Sarpal

Sastry

Bansal

et al. 2012

Lubrication Science

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The understanding of the relationship between molecular structure and viscosity–temperature behaviour of a lubricant system is a subject of considerable importance. The quantitative distribution and types of different classes of hydrocarbons such as aromatics, paraffins (normal and iso) and naphthenes determine the physico‐chemical behaviour of a lubricant system. The study of molecular structure and molecular alignment of hydrocarbons constituting a lubricant helps in the development of lubricating oil with desired physico‐chemical properties. The present study highlights the application of nuclear magnetic resonance spectroscopic technique for deriving detailed hydrocarbon structural features present in API groups II and III base oils produced through catalytic hydrocracking/isodewaxing processes. The viscosity–temperature and viscosity–pressure properties, such as viscosity index, pour point, elastohydrodynamic film thickness and cold cranking simulator viscosity, were determined. The structural features of these base oils such as various methyl branched structures of isoparaffins and branching index, which are characteristics of high performance molecules, were correlated with the above‐mentioned properties to explain their physico‐chemical properties, particularly low temperature properties. The molecular dynamics parameters such as diffusion coefficient and T1 relaxation times estimated from the nuclear magnetic resonance spectral studies have provided sufficient evidence for the dependence of these properties on these high performance molecules present in various types of methyl structures of isoparaffins of groups II and III base oils compared with conventional group I base oils. Results are explained on the basis of molecular structural differences of hydrocarbons present in these base oils and diffusion measurement studies. On the basis of the studies, molecular engineering concept for the designing of a high performance base oil molecule is proposed. Copyright © 2012 John Wiley & Sons, Ltd.

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“…'H and 13 C-NMR techniques have been used to estimate structural parameters in petroleum cuts [8][9][10] but they have the limitations in resolving the resonance of CH" (n = 0-3) groups in the aliphatic region.…”

Section: Introductionmentioning

confidence: 99%

NMR molecular characterization of lubricating base oils: Correlation with their performance

et al. 1998

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The NMR technique was used to characterize some base oils of different nature (mineral, saturated polyolefins, hydrocracked and from waxes hydroisomerization) at the molecular level. Base oils are used in the formulation of lubricants with the addition of suitable additives which improve the final products performance. The studied base oils are used particularly in the formulation of engine oils. In this paper we have compared two "NMR editing" techniques which allow one to quantify the CH" (n = 0-3) fractions of an "average" base oil molecule: 1) the gated spin echo (GASPE) and 2) the distortionless enhancement by polarization transfer (DEPT). We found that the quantitative data obtained from GASPE have a better accuracy than those from DEPT and so we chose GASPE to study the molecular characteristics of the aliphatic moieties of the base oils. On the basis of the GASPE data and of the average molecular mass obtained via VPO (Vapor Pressure Osmometry), the average number of branches and aliphatic rings were calculated. Moreover, on the basis of GASPE the distribution of side chain lengths and the positions of the methyl groups along the straight chain (methyls are the only groups for which the positions are directly obtained from NMR spectra) were obtained. A confirmation of the reliability of the NMR approach was achieved by comparing the branching degree, found with the NMR approach, of some base oils with their heats of fusion measured with the Differential Scanning Calorimetry (DSC). The heats of fusion are expected to be directly related to the length of straight CH2 sequence and therefore to be lower for more branched molecules. We found that for base oils with similar aliphatic moieties, the heats of fusion are lower for more branched base oil molecules with a nearly linear correlation. The exception to this rule is represented by the two olefinic oils. Besides, we found that the fraction of the methyls on aliphatic chains longer than three carbons, determined with GASPE, correlates very well with the pour points values, with the only exception of the mineral oil.

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

Cited by 53 publications

References 16 publications

Quantitative determination of aliphatic hydrocarbon compounds by 2D NMR

Quantitative determination of aliphatic hydrocarbon compounds by 2D NMR

Correlation of structure and properties of groups I to III base oils

NMR molecular characterization of lubricating base oils: Correlation with their performance

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