Molecular-Level Structural Insight into Clarified Oil by Nuclear Magnetic Resonance (NMR) Spectroscopy: Estimation of Hydrocarbon Types and Average Structural Parameters

Abstract

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.

Empirical Models to Characterize the Structural and Physiochemical Properties of Vacuum Gas Oils with Different Saturate Contents

“…The verification of the correctness of measurement of saturate content of FCC SLO (sample Nr 57 from Table S1 from Supplementary material) by juxtaposing its hydrogen content against the relation established for FCC slurry oils (data extracted from Ref. [38]), shown in Figure S1, indicates that this FCC SLO should have saturate content of 19 wt.%. This value almost completely coincides with that predicted by Equation (37)-19.4 wt.%.…”

“…A total of 74 vacuum gas oils characterized by HPLC-MS, NMR, SARA analysis and density, refractive index, aromatic carbon content, hydrogen content, molecular weight as reported in [2][3][4]15,[33][34][35][36][37][38][39][40] were used in this study (Table S1 from Supplementary material). The empirical models evaluated in this research are summarized below: The n-d-M method was originally developed by Van Nes and van Westen [41] and relates the structural group composition determined by the use of NMR in terms of the contents of paraffinic, naphthenic and aromatic carbon to three oil physical properties: refractive index, density and molecular weight.…”

“…The verification of the good fit of ARI to the number of aromatic rings in hydrocarbons and in vacuum gas oils (fluid catalytic cracking slurry oils (FCC SLOs); data taken from Ref. [38]) is illustrated in Figure 3a,b. As apparent from the data in Figure 3b, one sample of FCC SLO deviates from the regression line (Sample Nr 56 from Table S1 from Supplementary material).…”

“…The yield of the least valuable product from the VGO conversion processes-the unconverted VGO (bottoms) product-is defined by the content of heavy aromatics because it is difficult to crack [7,29]. Considering that the conversion level and the yields of valuable products from the VGO conversion processes depend on the contents of the saturates, aromatic carbon and heavy aromatics we investigated the properties of 74 VGOs published in the open literature [2][3][4]15,[30][31][32][33][34][35][36][37][38][39][40]. The studied VGOs had been characterized by HPLC-MS (high-performance liquid chromatography-mass spectrometry), NMR (nuclear magnetic resonance), SARA (saturates, aromatics, resins, asphaltenes) analysis and the typical physicochemical properties like density, distillation, refractive index, etc.…”

Research on a Multinode Joint Vibration Control Strategy for Controlling the Steering Wheel of a Commercial Vehicle

“…In subsequent real vehicle tests, the vibration sensor was uniformly distributed on these nodes, and combined with the test data, the abnormal vibration link interval of the steering wheel and the corresponding engine excitation speed were found in turn under the condition of the idling test. Based on the studies on the redesign of the vibration parameters [24][25][26] and modal frequency offset optimization [27][28][29], the structures existing in these abnormal vibration link intervals further improved. After obtaining the vibration modal information with the FEA and modal analysis methods, along with the results of the actual vehicle test, the analysis results show that the overall modal frequency of the improved steering system deviated from the excitation frequency of the engine, realising the offset frequency damping design of the steering system and verifying the effectiveness of the improved scheme and MDVC.…”