Using the Time-Domain Nuclear Magnetic Resonance (TD-NMR) for Quantification of the Diesel Adulteration with Ethanol

Abstract

Diesel is the most important liquid fuel in Brazil, representing 49.6% of the total liquid fuels commercialized in the country and, therefore, is important to have simple and rapid method for diesel quality control. The Brazilian National Agency of Petroleum, Gas and Biofuels verified that 4.0% of the diesel samples did not meet the required specification in 2022. Adulterated fuel increased fuel consumption, cause engine problems, increased emission of polluting gases among others problems. This study presents the use of bench top, time domain nuclear magnetic resonance (TD-NMR) relaxometer as a simple, rapid and non-destructive analytical method to quantify the adulteration of diesel with ethanol, which is the cheapest liquid fuel available in Brazil. The results show that commercial diesel and ethanol have transverse relaxation time (T₂) equal to 0.67 s and 1.75 s, respectively. The addition of 10–90% v/v) ethanol in diesel increased the T₂ linearly. The correlation of T₂ values with the middle infrared band at 1747 cm⁻¹ shows determination coefficient (R² = 0.94). Therefore, TD-NMR relaxometry is a rapid, simple and alternative method to determine the adulteration of the commercial diesel with ethanol.