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For the first time, the development of prediction models of the penetration grade and the softening point of vacuum residues (VRs) and pavement asphalts, from the structural data obtained with prot...

This paper reports the findings of a one-year long study, that every week measured the physicochemical properties (P: penetration; A: softening; Ip: penetration index; V: rotational viscosity, R: mass loss), and the spectroscopic and the relaxometry properties via nuclear magnetic resonance, of the vacuum residues (VR) produced in a refinery and those modified into asphalts to fabricate pavements with penetration grade 60/70. The evolution of the structural changes, along the time of study, was measured via high-field and low-field 1H NMR and analyzed through multivariate statistical methods. The attained results with high-field 1H NMR showed that when the VR are oxidized, the proportion of protons associated with the high-molecular-weight polyaromatic increases. On the other hand, the low-field 1H NMR results, through a greater number of unimodal distribution plots of T2 relaxation time, showed the homogenization of the aggregation as well as of the dynamic properties of the molecules, thus indicating th...

In our previous articles (Energy & Fuels 2017, 31, 133–139 and Energy & Fuels 2017, 31, 8997–9005), it was presented that the asphaltenes of the Colorado field have different chemical structures, and these change the properties of crystallization of the paraffins. In this paper, we present a new way to understand the effects of the chemical structure of the asphaltenes on crude oil rheology, which includes correlating the average molecular parameters (AMPs) and the concentration of the asphaltenes with rheological properties using chemometric methods such as the partial least squares method. The asphaltenes were separated from six crude oil samples (average °API of 38) and were characterized using nuclear magnetic resonance to determine their main molecular parameters. Rheological properties including viscosity, yield stress, and gel temperature were experimentally determined for each of the crude oil samples and their respective maltenes. The results of a multivariate analysis show that the AMPs of the a...

In a previous article (Molina V., D.; Energy Fuels 2017, 31, 133−139; DOI: 10.1021/acs.energyfuels.6b01887) the structural differences of asphaltenes in Colombian light crude oils from the same field, i.e., the Colorado oilfield, were presented. Colorado crude oil is a light crude with very low content of asphaltenes (

The aim of this work was to demonstrate that the average chemical structure of the asphaltenes of a crude oil sample is unique compared with crudes of other wells from the Colorado Oil field, Colombia. Six crude oils extracted from several depths (from 2112 to 6178 ft) were studied; these crude oils have a very critical problem of deposition of paraffins and very low concentrations of asphaltenes (

Naphthenic acids and sulfur compounds cause corrosion problems in the crude distillation units. Their heterogeneity in the concentration and reactivity makes it difficult to predict the corrosivity of crude oils. In this paper, the areas of resonance signals belonging to 12 chemical shift regions of the proton nuclear magnetic resonance (1H NMR) spectra of crude oils were correlated with the corrosion rate of AISI SAE 1005 carbon steel using a partial least squares regression. The corrosion rates were determined by weight loss tests at 350 °C for 12 h. In addition, a correlation to calculate the corrosion rate based only on the acidity and sulfur percentage of crude oils was proposed for the same crude oil samples. A statistical comparison of the proposed correlations indicates that the 1H NMR-based correlation has better quality in predicting corrosivity of crude oils. The combination of 1H NMR spectroscopy with chemometric techniques provides a fast alternative method for quantitative prediction of the ...

Various methods were developed to predict the stability of Colombian crude oils, in which the integral areas of the resonance signals from 12 regions of 1H nuclear magnetic resonance (NMR) spectra of 29 widely different crude oils were correlated with the stability parameter of Heithaus (Po) and the colloidal instability index (CII). Correlations between the NMR spectra and properties were obtained using partial least-squares (PLS) regression and multiple linear regression (MLR). The prediction models for Po and CII by PLS had coefficients of determination (R2) of >98 and >99%, respectively, while the cross-validation values (CV, q2) ranged from 89 to 90%, respectively. The models obtained from MLR showed a high adjusted R2 (R2ad) for Po and a lower R2ad for CII. The R2 values of the prediction models for Po ranged from 97 to 98%. The use of these predictive methods is faster, more environmentally friendly, and less expensive than conventional methods. Of the set of crude oils used in this study, it was o...