Gurpreet Singh Kapur

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.

Determination of aromatics and naphthenes in straight run gasoline by 1H NMR spectroscopy. Part I

A 1H NMR-based method has been developed for determining the composition (aromatics, naphthenes and paraffins) of straight run gasoline fractions. The equations required for the calculations have been derived based on the assignment of the overlapped 1H NMR spectra of the samples with particular emphasis on signals from naphthenes and iso-paraffins. The 1H NMR results have been compared with those obtained from GC method. The absolute standard deviations between the NMR and GC methods are1.7 and 2.1% for total aromatics and naphthenes, respectively.

Characterization by 13C n.m.r. spectroscopy of base oils produced by different processes

Abstract The hydrocarbon composition of base oils produced by different processes—hydrotreatments (hydrocracking and wax isomerization), solvent refining plus hydrofinishing, and severe hydrofinishing—were determined by 13 C n.m.r. spectroscopy. Structural parameters such as normal and iso-paraffin contents, average chain length and number of branching sites were estimated by new equations derived after complete assignment of signals in the 5–21 ppm 13 C n.m.r. region. Quantitative differences in various types of branched structures among different categories of base oils were established. Relations between specific iso-paraffinic structures responsible for very high viscosity index and low pour point are discussed in terms of mobility behaviour and spin-lattice relaxation time measurements.

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

Studies On Competitive Interactions and Blending Order of Engine Oil Additives by Variable Temperature 31P-NMR and IR Spectroscopy

Interactions between various engine oil additives including dispersant, detergent, antiwear/antioxidant, and viscosity index improvers have been investigated through changes in the 31P-NMR and IR spectra. Significant changes in the 31P-NMR and IR spectra of zinc dialkyldithiophosphate (ZDDP) have been observed by varying the blending order of additives. Dispersant-detergent (polyisobutylene succinimide-calcium overbased sulfonate) and viscosity index improver-detergent (dispersant olefin copolymer-calcium overbased sulphonate) interactions were found to be strong and irreversible in nature. Variable temperature 31P-NMR spectra have provided enough evidence to suggest that the actual performance of an additive may not be decided by its bulk interactions with other additives at room temperature, and that tribochemical reactions occurring at higher temperature play a greater role.

Modified method for hydrocarbon type analysis of blended base stocks by infrared spectroscopy

Abstract A modified method is described for the determination of the aromatic, naphthenic and paraffinic carbon contents of blended base oils by infrared spectroscopy. These oils are blends of mineral base oils and linear alkylbenzenes (LAB) or heavy alkylated benzenes (HAB). The Brandes equation has been modified to account for the absorptivity of LAB/HAB, using 13 C n.m.r. data as a reference. The results obtained by applying the new equation to such blends agree well with those obtained by n.m.r. This new method can be used for rapid and convenient quality control during base oil production.

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.

High-density polyethylene/needle-like sepiolite clay nanocomposites: effect of functionalized polymers on the dispersion of nanofiller, melt extensional and mechanical properties

The present article reports the preparation of high density polyethylene (HDPE)/sepiolite-clay nanocomposites with improved mechanical performance and melt extensional properties by melt compounding using a co-rotating twin screw extruder. Maleic anhydride grafted high density polyethylene (HDPE-g-MA) (having different MFI and maleic anhydride content) was used as compatibiliser to investigate systematically the effect of polarity and molecular weight on the properties of HDPE/sepiolite nanocomposites. The influence of sepiolite loading (1–10 wt%) and type of compatibilizer on morphological, mechanical and melt extensional properties (melt strength, drawability and extensional viscosity) were investigated and analyzed. Sepiolite-clay significantly enhanced the mechanical properties, melt strength and extensional viscosity with slight reduction in drawability at 10% w/w loading. For example, ∼40% increase in tensile modulus and ∼50% improvement in flexural modulus was obtained at 10% w/w sepiolite loading. The compatibiliser having lower MFI showed significant improvement in melt extensional properties as compared to compatibiliser having higher MFI. Scanning electron microscopy and transmission electron microscopy revealed the better dispersion of sepiolite in the presence of compatibiliser, however it was much better when HDPE-g-MA having higher MFI was used as compared to compatibiliser having lower MFI. Thermal stability increased in the presence of sepiolite which was further improved in the presence of compatibiliser.

Use of HPLC to monitor olefins, dienes, and aromatics in the dehydrogenated products of higher n-paraffins

ABSTRACT The linear higher olefins are generated through catalytic dehydrogenation of long-chain linear paraffins. During the catalytic dehydrogenation, a variety of dienes and aromatics are also formed. These side products not only cause coking of the catalyst, but also hamper in the reaction course of olefins with other substrate. A method has been developed based on the High-Performance Liquid Chromatography with Refractive Index detection for simultaneous estimation of olefins, dienes, and aromatics in the catalytic dehydrogenated product of model compound decane. The application of method for monitoring of the dehydrogenated stream from C10-C14 n-paraffins has also been discussed.

Novel HPLC-RI-UV based method for simultaneous estimation of saturates, olefins, conjugated dienes and aromatics in full range cracked gasoline

Abstract A fast method based on High performance liquid chromatography technique for the estimation of Saturates, Olefins, Conjugated dienes and Aromatics in Cracked gasoline samples has been developed. In this work, the focus was on choosing the right reference standard against which olefin could be estimated. The olefin reference standard was first shortlisted using Nuclear Magnetic Resonance spectroscopy and Gas chromatography based Simulated Distillation analysis as per ASTM D2887. The values estimated against shortlisted standards using HPLC were compared with values obtained using standard Flourescent Indicator Adsorption(FIA) based ASTM D1319 method to select one. The aromatics were estimated against o-Xylene.