Recent Advances in the Characterization of Gaseous and Liquid Fuels by Vibrational Spectroscopy (original) (raw)
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Environmental biotechnology, 2012
The use of mixtures of oil-based fuels with organic chemical components (e.g. ethanol, methanol) has been gaining ground in recent years. Several countries try nowadays to replace part of the fossil fuels for various reasons including economics, sustainability or optimization of resources. The characteristics of these combustiblerelated chemical component blends can be analyzed by different means. Optical spectral analysis (e.g. Raman, Fourier-transform infrared, etc.) can extract in many cases most of the required information concerning the molecular structure of a determined chemical sample in an effective and clean manner. Experimental detailed Raman spectra from various gasoline-ethanol blends and a gasoline-ethanolmethanol blend are presented. The Raman spectral information obtained has been used for approximated quantitative analysis with no additional chemical marker or complicated calibration methods. The analysis has been performed using a self-designed, low-cost, robust an...
Prediction of diesel fuel properties by vibrational spectroscopy using multivariate analysis
Journal of Analytical Chemistry, 2012
Partial least squares regression (PLS) calibration models based on Fourier transform infrared (FTIR ATR) and Raman spectra (FT Raman) were applied to the rapid and accurate simultaneous determi nation of the main properties of diesel fuels. Training sets were composed of over ninety commercial diesel fuel samples. The methods use baseline uncorrected, raw FTIR ATR and FT Raman spectra. Two spectral regions were studied: full spectral region and "fingerprint" region. The models were validated using the cross validation process. Based on the correlation coefficient and root mean square error of cross validation (RMSECV) values the both developed calibration models, PLS/FTIR ATR and PLS/FT Raman, were very accurate and comparable with standard testing methods. The following diesel fuel properties may be confi dently estimated: cetane number, cetane index, density, viscosity, distillation temperatures at 10% (T10), 50% (T50) and 90% (T90) recovery, as well as the contents of total aromatics and polycyclic aromatic hydrocar bons. As compared to the "fingerprint" spectral region, the PLS/FTIR ATR model using full spectral region displayed slightly better performances with the most of the correlation coefficient values above 0.98.
Infrared Physics & Technology, 2019
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Characterization of gasoline/ethanol blends by infrared and excess infrared spectroscopy
Fuel, 2015
Frequency-shifts and excess absorbance suggest alcohol self-association via hydrogen bonding. High sensitivity and accuracy can be obtained using the alcoholic CO stretching mode for quantitative measurements. FTIR provides a fast and straightforward tool for measuring the chemical composition of a blend. a b s t r a c t Fuels for automotive propulsion are frequently blends of conventional gasoline and ethanol. However, the effects of adding an alcohol to a petrochemical fuel are yet to be fully understood. We report Fouriertransform infrared spectroscopy (FTIR) of ethanol/gasoline mixtures with systematically varied composition. Frequency shifts and excess infrared absorbance are analyzed in order to investigate the mixture behavior at the molecular level. The spectroscopic data suggest that the hydrogen bonding between ethanol molecules is weakened upon gasoline addition, but the hydrogen bonds do not disappear. This can be explained by a formation of small ethanol clusters that interact via Van der Waals forces with the surrounding gasoline molecules. Furthermore, approaches for measuring the chemical composition of ethanol/gasoline blends by FTIR are discussed. For a simplistic approach based on the Beer-Lambert relation, an optimized set of parameters for quantitative measurements are determined. The best compromise between measurement sensitivity and accuracy is found for the CO stretching mode of the alcohol. For the traditional method of calibrating the ratio of integrated band intensities of the CH and OH stretching regions it is found that narrowing the spectral window of the CH stretch can significantly improve the measurement sensitivity.
Journal of Chemical Education, 2012
Biodiesel has gained attention in recent years as a renewable fuel source due to its reduced greenhouse gas and particulate emissions, and it can be produced within the United States. A laboratory experiment designed for students in an upper-division undergraduate laboratory is described to study biodiesel production and biodiesel mixing with conventional petroleum-based diesel fuel using Fourier transform infrared (FTIR) spectroscopy. The production of biodiesel from oil via a transesterification reaction is monitored by the intensity of the C−O ester peak (1098 cm-1), whereas the mixing of biodiesel and petroleum-based diesel is monitored by the CO ester stretch (1746 cm −1). The impact of water on the precision of the biodiesel mixture is determined using a Karl Fischer titration to monitor water content. Students also gain experience with method validation using multiple sampling platforms (liquid cell, ATR-cell, and IR card). At the conclusion of the experiment, students are able to use FTIR to quantitatively monitor reactions and determine mixtures, determine the impact of water content on quantitation, and evaluate the strengths and weaknesses of different sampling platforms for various applications.
Thermochemical Characterization of Bio- and Petro-diesel Fuels using a Novel Laser-Heating Technique
Energy & Fuels, 2015
A state-of-the-art, rapid laser-heating technique, referred to as the laser-driven thermal reactor, was used to characterize National Institute of Standards and Technology Standard Reference Material (SRM) diesel and biodiesel fuels, as well as a prototype biodiesel fuel. Also described are the various issues associated with carrying out these measurements under different operating conditions (i.e., temperature, pressure, heating rate, and sample mass). The technique provides measurement of various relevant thermochemical characteristics; for this investigation the focus was on the sample endothermic/exothermic behavior, specific heat release rate, and total specific heat release. The experimental apparatus consists of a copper sphere-shaped reactor mounted within a vacuum chamber, along with integrated optical, gas-supply, and computer-controlled data-acquisition subsystems. At the center of the reactor, the sample and substrate rest on a thermocouple. The reactor is heated from opposing sides by a near-infrared laser to achieve nearly uniform sample temperature. The change in sample temperature with time (i.e., thermogram) is recorded and compared to a baseline (no sample) thermogram obtained prior to the experiment, and then processed (using an equation for thermal energy conservation) for the thermochemical information of interest. Results indicated that the baseline is affected by residue remaining after completion of reactions and a change in the oxide layer of the reactor sphere outer surface. Thus, the sphere must be pre-oxidized in air using the laser prior to any sample or baseline measurement. This investigation provides preliminary evaluation of SRM biodiesel fuels, with the results being consistent with distillation curve work reported in the literature.
Analytical Chemistry, 2013
There is a critical need for a real-time, nonperturbative probe for monitoring the adulteration of automotive gasoline. Running on adulterated fuel leads to a substantive increase in air pollution, because of increased tailpipe emissions of harmful pollutants, as well as a reduction in engine performance. Consequently, both classification of the gasoline type and quantification of the adulteration content are of great significance for quality control. Gasoline adulteration detection is currently carried out in the laboratory with gas chromatography, which is time-consuming and costly. Here, we propose the application of Raman spectroscopic measurements for on-site rapid detection of gasoline adulteration. In this proof-of-principle report, we demonstrate the effectiveness of Raman spectra, in conjunction with multivariate analysis methods, in classifying the base oil types and simultaneously detecting the adulteration content in a wide range of commercial gasoline mixtures, both in their native states and spiked with different adulterants. In particular, we show that Raman spectra acquired with an inexpensive noncooled detector provides adequate specificity to clearly discriminate between the gasoline samples and simultaneously characterize the specific adulterant content with a limit of detection below 5%. Our promising results in this study illustrate, for the first time, the capability and the potential of Raman spectroscopy, together with multivariate analysis, as a low-cost, powerful tool for on-site rapid detection of gasoline adulteration and opens substantive avenues for applications in related fields of quality control in the oil industry. A utomotive gasoline or petrol is a complex organic compound, composed of volatile liquid hydrocarbons and a variety of additives, obtained through fractional distillation of crude petroleum oil. 1 The octane rating, which is also known as the octane number, is a standard measure of the performance of the automotive fuel, where, typically, gasoline with a higher octane rating is used in high-compression engines that have higher performance. Because of the financial incentives arising from differential taxes, automotive gasoline and diesel is often adulterated to maximize profits. 2−4 In particular, it has been reported that a diverse array of chemicals, ranging from kerosene and industrial solvents to used lubricants, are blended with the gasoline. 4 In addition, the adulteration of gasoline could also involve the blending of higher-grade gasoline with a lower-grade one. In order to avoid detection, the added adulterant has been observed to be typically limited to within 10%−20% by volume. 3 Clearly, this represents a particularly undesirable situation, as automotive engines are designed and manufactured to run on a specified grade of fuel. Therefore, running the same engines on adulterated fuel is likely to increase the air pollution, because of increased tailpipe emissions of harmful pollutants (including hydrocarbons, carbon monoxide, and particulate matter) and