Chemometrics-Based Analytical Method Using FTIR Spectroscopic Data To Predict Diesel and Diesel/Diesel Blend Properties Tulay Y. Inan,* Adnan Al-Hajji, and O. Refa Koseoglu SAUDI ARAMCO, Research and Development, 31311 Dhahran, Saudi Arabia ABSTRACT: In the hydrocarbons downstream business, it is very beneficial to quickly and reliably determine the physical and/or chemical properties of fuels. In this context, a nondestructive method was applied using midband Fourier transform infrared (FTIR) spectroscopy in association with multivariate partial least squares (PLS) chemometrics to determine the properties of nine groups of middle distillates (diesels) boiling in the range 180-370 °C. This method enables identification of one single diesel property at a time or a group of properties (32 properties) simultaneously in the spectral data between 4000-650 cm -1 ; with a minimum number of steps and without any sample preparation. The method was further used for two blends prepared from individual diesel samples. The results showed that using PLS models to process FTIR data is a practical analytical method to predict diesel fuel properties. Statistically, the results obtained showed low standard deviations, a very low root mean square error of cross-validation (RMSECV), low uncertainty values, less than 10 factors, but high correlation coefficient, R 2 , and performance index (PI) values. 1. INTRODUCTION Petroleum products can be grouped into light distillates (LPG, gasoline, and naphtha), middle distillates (kerosene and diesel), heavy distillates, and residuum (heavy fuel oil, lubricating oils, wax, and asphalt). The middle distillate fraction boiling in the nominal range 180-370 °C is called gas oil or simply diesel. Diesel consists of a very complex mixture of thousands of individual chemicals of different hydrocarbon classes (saturates and aromatics) with a wide range of carbon numbers (C 12 -C 20 ). The chemical composition of the diesel influences its properties and hence performance in downstream refining operations. 1 Standard test methods, such as those from the American Society for Testing and Materials (ASTM), the Institute of Petroleum (IP), or other agencies, are traditionally used to determine petroleum product properties. These methods are reliable, accurate, and widely accepted but they also have some disadvantages. These methods require a large amount of sample, consume time, and may involve the use of toxic or environ- mentally dangerous reagents. 2 In experimental analytical chemistry, an interdisciplinary technique of chemometrics has been widely used to determine patterns and relationships. It uses mathematical methods and computer science for the analysis of results to predict the physical and/or chemical properties of the analyzed samples. For analyzing chemical systems, including fuels, multivariate cali- bration has been used as one application of chemometrics. 1-11 FT-IR spectroscopy is a nondestructive, rapid, and easy ana- lytical method that is based on the measurement of character- istic fundamental resonances for different functional groups. It produces well-defined peaks at wavelengths between 2.5 and 25 μm, corresponding to the 4000-650 cm -1 wavenumber region. Use of near-IR and FT-IR spectroscopy to determine diesel and gasoline fuel properties has been extensive. 1-5,7,8 Furthermore, there are some FTIR and/or NIR applications where chemometrics was involved for diesel and diesel/biodiesel quality screening as well as detection of contaminations in gasoline and diesel. 1-5,7-11 FTIR spectral intensities are expected to correlate with diesel properties measured by standard methods. General accepted arguments should be considered in order to illustrate the relationships between the fuel compositions and the spectro- scopic features and, hence, the physical and/or chemical prop- erties. High specific gravity, for example, is known to be asso- ciated with elevated concentrations of straight chain paraffinic hydrocarbons. On the other hand, the higher the aromatic hydrocarbon content in the fuel is, the higher the octane number, but the lower the cetane number becomes. Thus, all these chemical features are reflected in the FTIR spectrum profile. This study applies nondestructive midband Fourier transform infrared (FT-IR) spectroscopy in association with multivariate Received: March 29, 2016 Revised: May 28, 2016 Published: May 31, 2016 Figure 1. Simplified workflow for the development of the correlation models for the fuel properties from FT-IR data. Article pubs.acs.org/EF © 2016 American Chemical Society 5525 DOI: 10.1021/acs.energyfuels.6b00731 Energy Fuels 2016, 30, 5525-5536