Application of Near-infrared Spectroscopy to the Quality Assurance of Ethanol and Butanol Blended Gasoline

Abstract

The authors recorded near-infrared spectra of ethanol and butanol blended gasoline in the range of 5–30% of alcohol content. The major peaks in the spectra were assigned to the first CH overtone (~5670, ~5770, ~5810, and ~5870 cm⁻¹), first OH overtone of alcohol (~6320 cm⁻¹, 6720 cm⁻¹), and second CH overtone (~8285, ~8400, and ~8690 cm⁻¹). The OH overtone peak of the recorded spectra was subjected to the partial least squares (PLS) procedure to obtain calibration plots. The correlation coefficients (R ₂) of .9938 and .9634 were obtained for the ethanol and butanol PLS calibrations, respectively. Recently there has been a great interest in butanol as a better gasoline blending alternative to ethanol. To understand the alcohol-gasoline interactions the integrated area of the polymeric OH alcohol band (~6320 cm⁻¹) was plotted against the percentage of the alcohol content and the abrupt changes in the area were explained in terms of the viscosity of the fuel. Based on the OH integrated area plots the authors suggest that between 10 and 15% butanol can be blended with gasoline without compromising the viscosity of the fuel for optimum combustion. The results reveal that the near-infrared spectroscopy technique is a good alternative to the chromatographic methods for the quality assurance of the ethanol blended gasoline and in the future may find its application in the quality control of the butanol blended gasoline. The precision of the near-infrared quantification of ethanol and butanol is ±1%.

Keywords:

• blended gasoline
• butanol
• ethanol
• near-infrared spectroscopy
• partial least squares regression