Investigations on Storage and Oxidative Stability of Biodiesel from Different Feedstocks Using the Rancimat Method, Infrared Spectroscopy, and Chemometry

Abstract

Biodiesel can be altered when exposed to air, light, temperature, and humidity. Other factors, such as microbial or inorganic agents, also interfere with the quality of the product. In the present work, the Rancimat method and mid-infrared spectroscopy associated with chemometry, were used to identify the oxidation process of biodiesel from different feedstocks and to evaluate the antioxidant activity of butylated hydroxytoluene. The study was carried out in four steps: preparation of biodiesel samples with and without the antioxidant agent, degradation of the samples under the effect of light and heating at 70 °C, measurements of the induction period, obtention of infrared spectra, and multivariate analysis. The Fourier transform mid-infrared spectroscopy was used in combination with multivariate analysis, using techniques such as principal component analysis (PCA) and hierarchical clustering analysis (HCA). The Rancimat results showed that babassu biodiesel has a higher resistance to oxidative degradation, while chicken biodiesel is the most susceptible to degradation; on the other hand, the antioxidant activity was more effective with chicken biodiesel, demonstrating that the antioxidant effect depends on the feedstock used in the production of biodiesel. The oxidative stability of babassu oil-, corn oil-, and chicken fat-based biodiesels decreased during storage both in the presence of light and at high temperature. Prior to PCA, all spectra were pre-processed with a combination of Savitzky–Golay smoothing filter with a 7-point window, baseline correction, and mean-centered data. The use of mid-infrared spectroscopy associated with PCA revealed the first two components to explain the greater variability of data, representing over 75% of total variation for all analyzed systems. In addition, it was able to separate the biodiesel samples according to the fatty acid profile of its feedstock, as well as the type of degradation to which it was subjected, the same being confirmed by HCA.

FT-MIR-ATR Associated with Chemometrics Methods: A Preliminary Analysis of Deterioration State of Brazil Nut Oil

“…In a study carried out by De Menezes et al [52], the principal component analysis associated with the FT-MIR-ATR was used to investigate the alteration of biodiesel that can be degraded when exposed to certain weather conditions such as air, light, temperature, and humidity, consequently changing its quality parameters, among them the acidity index. Thus, the model proposed a total variation of 75% of the proposed environmental conditions.…”

Biodiesel production from edible and non-edible biomasses and its characterization

“…Therefore, when the oxidative stability of fuel falls outside the specified limits, it can adversely affect fuel stability during storage as well as vehicle performance. This instability can lead to the formation of deposits on engine parts, potentially causing clogging in the fuel filter [14].…”