Mitra Bhanu Patel

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.

A 1H NMR method for the estimation of hydrogen content for all petroleum products

AbstractBackgroundHydrogen content is an important parameter for all petroleum products, because the performance of the products for specific application depends on the concentration of hydrogen in it. Further, hydrogen content can be used as a measure for quality control during the production process and assess the quality of the products, which is governed by the catalyst used. Therefore, to get the desired petroleum products like MS and HSD, pilot scale evaluation of different catalysts plays an important role in problem solving during troubleshooting in refineries. During evaluation studies the performance of catalyst depends upon the hydrogen consumption and mass balance in any catalytic process. In order to calculate total hydrogen consumption during production of different petroleum products an effort has been made to develop a universal method based on nuclear magnetic resonance (NMR) technique, that allows estimating hydrogen content in all petroleum fractions, ranging from IBP to 530+ °C.MethodsThe method uses hexamethyldisiloxane (HMDSO) for the first time as a quantitative reference standard respect to which the H content of unknown samples has been estimated. The newly developed method can also determine H/C and O/C ratio of ethanol blended fuel in a given sample without any additional experimentation.ResultsHydrogen content for twenty five model compounds was determined along with nearly hundred petroleum fractions. There has been found to be good correlation between the existing ASTM D5291 and developed NMR spectroscopic based methods. For low boiling petroleum fractions, where ASTM D5291 is not suitable, there is no direct way to correlate the data. However, as the hydrogen content estimated for some model compounds shows a high degree of correlation R2 = 0.998, between theoretical values and estimated values, indirectly validate the developed method.ConclusionsA universal NMR based method for the estimation of hydrogen content in all sort of petroleum products irrespective of their origin, composition, boiling range has been developed. Graphical AbstractH-Content of petroleum products:1H NMR vs. ASTD D5291 combustion method.

HPLC Method for Monitoring the Conjugated Dienes and Olefins in FCC, Coker Gasolines, and their Hydrogenated Products

The conjugated dienes if present in gasoline have the tendency to polymerize and cause fouling during various refinery processes. Therefore the conjugated dienes need to be reduced. While the conjugated dienes in gasoline are undesirable, the olefins are desirable and act as octane booster. The selective hydrogenation unit selectively reduces conjugated dienes keeping the content of olefins more or less intact. A method based on HPLC-UV-RI has been reported to simultaneously monitor the conjugated dienes and olefins content in the gasoline range samples. The reported method has the detection level of 0.02 (w/W)% for the total conjugated dienes with respect to 2,4-dimethyl 1,3-pentadiene (DMP). The calibration curve for DMP is drawn in the range 0.2–2.5% (w/W) and the R2 is found to be 0.9972. The method is also applicable for the estimation of olefins content above 10% (w/W) level with respect to 1-octene. The calibration curve is drawn in the range 10–50% (w/W) of 1-octene and the R2 is found to be 0.9995.

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.

Elemental analysis of FCC catalysts by XRF & ICP techniques - A statistical comparison

Abstract FCC catalysts obtained from different refineries were analysed by ICP and XRF techniques for the elements Al, Ni, V, Ti & Fe and the results were compared statistically by Paired t-test, Regression analysis and F-test. It was observed that both the techniques are equivalent and there is no significant difference between the results for the analysis of Al, Ni, V, Ti & Fe in FCC catalysts. However, statistical analysis indicates that XRF is more precise compared to ICP. Therefore, XRF technique can be used routinely for the analysis of Al, Ni, V, Ti and Fe in FCC catalysts in place of ICP with advantage.