A. S. Sarpal

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.

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.

Structural Aspects of Crude Oil Derived Asphaltenes by NMR and XRD and Spectroscopic Techniques

Abstract Asphaltene samples obtained from crude processed at two Indian refineries were characterized for chemical composition and structure by nuclear magnetic resonance (NMR), X-ray diffractometry (XRD), fluorescence spectroscopic techniques, and chromatographic (column and GPC) techniques. Estimation of NMR average structural parameters were obtained by combined 1H, NMR 13C, NMR DEPT-45, and QUAT pulse sequence spectral editing techniques. The macrostructure and crystalline parameters of these samples were obtained by XRD. The nature of the functional groups have been obtained by IR technique. A combined NMR and XRD parameters were used to estimate the size of average aromatic structural units. Asphaltenes from one of the crudes (ASP-A) was found to be highly pericondensed, highly substituted, and higher molecular size compared to ASP-B asphaltene molecules. The number of aromatic sheets per unit sheets are 3.7 and 2.5 in the sample ASP-A and ASP-B, respectively. Both the asphaltene molecules in the samples have periodically and systematic arrangement of aromatic sheets in the unit sheet. The number of aromatic rings per unit sheet in ASP-A and ASP-B are 6.0 and 5.0, respectively. The fluorescence spectral studies has also exhibited λ max (the wavelength of maximum intensity) at 505 and 509 nm confirming to pericondensed higher polycondensed aromatic ring system in both the samples. The analysis of liquid chromatographic fractions of these samples show that each sample is composed of several polycondensed aromatic systems where unit sheet of ring sizes vary from 1.8 to 6.3 with varying molecular sizes. These structural parameters allowed a model structure of the asphaltenes to be constructed.

Molecular Dynamics of Synthetic-Based Lubricant System by Spectroscopic Techniques—Part 1

This article describes the structure–property relationships of synthetic pentaerythritol polyol esters (PEE) and polyalphaolefins (PAO) as established by the diffusion and mobility measurement and tilt angle results obtained by nuclear magnetic resonance (NMR) and infrared (IR) spectroscopic techniques, respectively. The diffusion coefficients (D) were found to be dependent on the molecular structure, alkyl chain length, shape and size, hydrodynamic volume, and alignment of the molecules in a lubricant system constituting these base stocks. The viscosity–temperature and viscosity–pressure properties such as viscosity index (VI), pour point (PP), elastohydrodynamic (EHD) film thickness, pressure–viscosity coefficient (α), hydrodynamic volume, and radius are explained on the basis of the variation in D with temperature and tilt angle on the smooth surfaces. The study has enabled us to propose a molecular structure of a synthetic molecule that can be molecularly engineered to have high-performance physicochemical properties.

Quality Control Aspects: A Simple Method for Estimation of Ethyl Alcohol in Oxy Diesel by NMR Spectroscopy

A direct and rapid method for the estimation of ethyl alcohol in oxy diesel based on NMR (1H, 13C) spectroscopic techniques has been developed. The estimation has been carried out by the methods (a) based on the determination of average group molecular weight (GMW) of the diesel and alcohol and (b) with precalibration of quantitative alcohol-diesel blends. Both the methods are independent of source, type, and nature of diesel (conventional, hydrocracked, hydrodesulfurization) produced by any of refinery processes. The precalibration method requires the use of standards for calibration, where as the GMW method does not require any. The methods have been tried on alcohol-diesel blends in the range of 1.0–10.0% w/w and will be applicable for quality control purposes in blending plant. The statistical treatment of theoretical and estimated values have shown excellent correlation (R 2 = .99). The effects of the spectral interference of emulsifier and coupler, which are added to emulsify the blends, on the chemical shift of alcohol signals in the 1H/13C-NMR spectra have also been studied.

Characterization of Metal Phthalocyanine Catalysts Using Field Desorption Mass Spectrometry

Abstract Metal phthalocyanines are a very important class of compounds due to their ability to activate oxygen, which enables them to become useful chemical reagents and largely-accepted catalysts for many chemical reactions. Phthalocyanines containing metals like iron, cobalt, manganese and vanadium are useful catalysts in many refinery processes. In the petroleum industry mercaptans are oxidized to disulfides by aerobic oxidation in an alkaline medium in the presence of a metal phthalocyanine. A number of analytical techniques have been explored to characterize metal phthalocyanines. In this article, we have for the first time successfully used field desorption mass spectrometry (FDMS) techniques for the characterization simple metal phthalocyanines and substituted metal phthalocyanines. For this purpose metal phthalocyanines were prepared in the laboratory and the conditions were optimized for the characterization of metal phthalocyanines containing cobalt, nickel, copper and zinc by FDMS. This technique was also successfully applied to characterize sulfato, nitro, and chloro substituted phthalocyanines. This technique has been found to be a useful tool for the characterization of phthalocyanines.

Monitoring of trace levels of p-dioxan in high purity benzene feedstock by capillary gas chromatography

SummaryA procedure has been standarized for the determination of p-dioxan (1,4-dioxan) in benzene feedstock in the range of 1 to 100 ppm by capillary GC. The GC conditions such as oven temperature, length of the column etc were optimized to achieve better resolution of p-dioxan from hydrocarbons. The standard addition method of quantitation, was used to determine the amount of p-dioxan and was found to give better results than those obtained by external standardization. Prior to analysis the identity of the p-dioxan peak was established by GC-MS. The proposed method has been applied for the monitoring of p-dioxan in high purity benzene feedstock produced by the Udex extraction process in the refinery. The data were used for optimization of plant conditions for the production of high purity benzene feedstock. By using this method, the p-dioxan content down to 0.5 ppm can be determined in the benzene feedstock.