Test method for determination of different biodiesels (fatty acid alkyl esters) content in diesel fuel using FTIR-ATR

doi:10.1016/j.renene.2018.09.010

Renewable Energy

Volume 133, April 2019, Pages 1231-1235

https://doi.org/10.1016/j.renene.2018.09.010 Get rights and content

Highlights

•
FTIR methods for determination of biodiesel content in blends with diesel fuel.
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Methods are applicable for biodiesels synthetized from different alcohols.
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Influence of alcohol content on quantification of biodiesel in blends with diesel.

Abstract

A novel procedure that uses FTIR-ATR C double bond O signal area (1690–1800 cm⁻¹) and a standard test method that is used for determination of fatty acid methyl ester in diesel were applied for the quantification of ethyl, propyl, butyl, isobutyl, pentyl, isopenyl, hexyl, heptyl, octyl, decyl, and dodecyl fatty acid esters in diesel. These methods were examined in the range from 0.0 to 30.0 vol% of biodiesel in diesel. The obtained correlation between concentration and FTIR absorption was highly linear (R² above 0.993, in most cases 0.999). Considering that diesel blends with butanol or higher alcohols with their corresponding fatty acid alkyl ester can satisfy the requirements for use in diesel engines, we tested if such blending would influence the results of those two methods. The results indicate that biodiesel can be quantified for blends with alcohol content up to 9 vol% of the total volume when signal area calibration is used.

Graphical abstract

Introduction

Methanol is used in biodiesel production due to its availability and low price, but it is also toxic, volatile, and mostly produced from fossil origin. Its main alternative in biodiesel production via transesterification of vegetable oil is ethanol, which is less toxic and produced in large quantities from biomass [1]. Moreover, there are several studies that focus on the use of other alternative alcohol feedstocks for transesterification such as 1-propanol [[2], [3], [4], [5]], 2-propanol [2,3,6,7], 1-butanol [2,3,6], 2-butanol [2,3,5,7], isobutanol [2], tert-butanol [5,6], 2-methyl-1-butanol [2], 2,2-dimethylpropan-1-ol [2,5], 4-methylpentan-2-ol [2], 2-ethylhexanol [7], 1-pentanol [2], 2-hexanol [3], 1-hexanol [3], 1-octanol [3,4], 2-octanol [3], and 1-decanol [3]. Excluding methanol and ethanol which are wildly studied, most of these studies examine the application of butanol because it can be produced from biomass [8,9]. Furthermore, butanol has a number of advantages over ethanol: it is less corrosive, less soluble in water, less volatile, it has a higher energy density, and it can be directly blended with diesel without compromising its application properties [10] eliminating the problem with residual alcohol [11]. Several fermentation process that produce butanol have gained a lot of attention (ABE - acetone/butanol/ethanol fermentation [12] and non-ABE fermentation [11]). One of the drawbacks is the cost of substrate which also may compete with food production. Glycerol was examined as an alternative substrate for butanol production [13,14] as it is readily available at a low price as a by-product of transesterification, becoming an environmental liability because of its massive production [11,15]. This approach could achieve an integrated and more sustainable production of biobutanol and biodiesel. Thus, by replacing methanol, a more environmentally friendly transesterification process and feedstock diversification could be achieved.

Fast and low-cost analytical methods would ease the research and development of these alternative fatty acid alkyl esters (FAAEs) as well as its industrial application. The use of fatty acid methyl ester (FAME) alone or blended with diesel fuels is regulated by European standard EN 590 which states that diesel fuel can contain up to 7.0 vol% of FAME. The specified standard test method for determination of FAME content in diesel fuel uses infrared spectroscopy, a well-known procedure described in standards ASTM D7371-14 [16] and EN 14078 [17]. FTIR is rapid, easy to use and part of standard laboratory equipment. The object of this study is to develop and test the applicability of two quantitative methods for precise determination of biodiesel content in the range from 0 to 30 vol% for ethyl, propyl, butyl, isobutyl, pentyl, isopenyl, hexyl, heptyl, octyl, decyl, and dodecyl fatty acid esters (FAAE) in diesel. Currently such a method is not available; i.e. the determination of higher alcohol fatty acid esters content in the biodiesel/diesel mixture and the influence of alcohol on the determination were not studied. Since alcohol is added in excess to achieve higher yields of biodiesel during transesterification, the influence of (residual or added on purpose) alcohol (1–200 vol%. of corresponding biodiesel) in FAAE/diesel blends on the results was investigated.

Section snippets

Materials

Diesel fuel that satisfies the requirements of EN 590 standard, without FAME and without any additives was obtained from INA Petroleum Industry refinery. The characteristics of the diesel are: density (832.9 kg m⁻³), water content (27 mg kg⁻¹), kinematic viscosity (2.646 mm² s⁻¹), cetane index (51.4), and sulfur content (3.9 ppm). Methyl, ethyl, propyl, butyl, isobutyl, pentyl, isopenyl, heptyl, octyl, decyl, and dodecyl fatty acid esters were synthetized by transesterification of sunflower oil

Calibration curves for quantification of FAAEs in diesel fuel

The FTIR spectra of diesel fuel, glycerol, ethanol, decanol, fatty acid ethyl ester, and fatty acid decyl ester are presented in Fig. 1. All sample spectra have characteristic signals corresponding to C single bond H stretching of alkyl groups in range from 2800 to 3000 cm⁻¹. Signals at 1458 and 1377 cm⁻¹, which correspond to CH_x bending, are also present in all sample spectra, but less pronounced in glycerol and ethanol. Meanwhile, the wide signal from 3050 to 3600 cm⁻¹, which belongs to single bond OH, is present

Conclusion

The method that uses FTIR-ATR C double bond O signal area (1690 - 1800 cm⁻¹) can be used to quantitatively determine the amount of methyl, ethyl, propyl, butyl, isobutyl, pentyl, isopentyl, hexyl, heptyl, octyl, decyl, and dodecyl fatty acid ester in biodiesel diesel blends. The standard test method that is used for determination of fatty acid methyl ester in diesel can also be applied for other alkyl fatty acid ester (ethyl, propyl, butyl, isobutyl, pentyl, isopentyl, hexyl, heptyl, octyl, decyl, and

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Test method for determination of different biodiesels (fatty acid alkyl esters) content in diesel fuel using FTIR-ATR

Highlights

Abstract

Graphical abstract

Introduction

Section snippets

Materials

Calibration curves for quantification of FAAEs in diesel fuel

Conclusion

Renew. Sustain. Energy Rev.

Fuel

Renew. Energy

Process Saf. Environ. Protect.

Appl. Energy

Process Saf. Environ. Protect.

Biotechnol. Rep.

Curr. Opin. Biotechnol.

Energy Convers. Manag.

Renew. Sustain. Energy Rev.

Curr. Opin. Biotechnol.

Biotechnol. Adv.