In the present work, a new method based on 1 H NMR spectroscopy has been developed for the estimation of total aromatics and their distribution as mono-and polynuclear (di-ring plus) aromatics in diesel-range fuel products. Multipulse NMR techniques such as, distortionless enhancement by polarization transfer and 2-dimensional heteronuclear correlation have been applied for the unambiguous assignment of the 2.0-3.5 ppm region due to R-substituents on the aromatic ring in the 1 H NMR spectra. The estimation of polynuclear aromatics is based on the estimation of bridgehead aromatic (Ar b ) and substituted aromatic (Ar q ) carbons using equations developed. The proposed 1 H NMR-based method correlates very well with the standard IP-391/ 90-and mass-spectrometric-based method (R 2 ) 0.99).

The present studies highlight the applications of N M R spectroscopic techniques for unravelling the unique structural features present in base oils responsible for imparting lubricant properties. The viscosity-temperature and viscosity-pressure properties of base oils of API groups I-N; such as viscosity, viscosity index, pour point, elastohydrodynamic film thickness, and pressure-viscosity coefficient, have been correlated with the detailed hydrocarbon composition of base oils with a n emphasis on the various types of methyl branched structures. Molecular dynamics parameters, such as diffusion coefficient and energy of activation, estimated from the N M R spectral studies have provided evidence of the factors responsible for the different viscosity-temperature or viscosity-pressure characteristics of base oils.

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A direct and easy-to-grasp methodology based on the combination of quantitative 1H and 13C nuclear magnetic resonance (NMR) has been developed for the estimation of total aromatics, saturates, and several important structural parameters, such as aromaticity, average number of aromatic rings per molecule, average number of aromatic carbon atoms per molecule, average molecular weight, degree of aromatic substitution, degree of aromatic condensation, nature of condensation, and substitution to aromatic ring, etc. for clarified oil (CLO) from Indian oil refineries. These parameters, along with HPLC analysis data for di- to penta-ring aromatics, provide a molecular-level understanding of this potentially valuable feedstock, which can thus be correlated with process parameters for needle coke production from CLO. The method exploits the concept of group molecular weight (GMWt) and uses three empirical equations governing the nature of aromatic condensation. The various types of CLO that originated from Indian oil refineries have been classified into three major classes, by virtue of their differential nature and composition. Two-dimensional (2D) HSQC NMR has been extensively studied for accurate assignment of different classes of protons in 1H NMR spectra of CLOs. The method was validated by SARA analysis using TLC-FID (IP-469) (R 2 = 0.9698) and by open column chromatography (ASTM D-2549) (R 2 = 0.9887) for hydrocarbon types.

The present study is focused on the quantification of glycerides and free fatty acid in oils extracted from various seeds for biodiesel production from Indian territory. A new method based on 1 H-and 13 C-NMR spectroscopic techniques was developed in order to estimate triglycerides (TG), diglycerides, monoglycerides, free fatty acids (FFA) and various other components such as para-substituted phenols, silylated methyl esters, aromatic acids, naphthalenes, etc. Iodine values of the extracted oils were estimated using the developed 1 H-NMR spectroscopic method, which was correlated with the TG content present in the sample. Results by the NMR method were validated by the blend preparation, fatty acid composition determined by the GC and from the iodine value of the samples. The developed method is direct, rapid and no sample treatment is required. The results from these comprehensive studies indicated that NMR spectroscopic technique is useful for the quantification of extracted oils and can be used effectively for the development and monitoring of biodiesel production and determining the fuel quality.