USO DE LA CROMATOGRAFÍA GASEOSA BIDIMENSIONAL COMPLETA PARA EVALUAR EL TIEMPO DE VIDA MEDIA DEL ACEITE DE SOYA, SU EFECTO EN LA ELABORACIÓN DE BIODIESEL

Revista Mexicana de Ingeniería Química[pic 1]

USO DE LA CROMATOGRAFÍA GASEOSA BIDIMENSIONAL COMPLETA PARA EVALUAR EL TIEMPO DE VIDA MEDIA DEL ACEITE DE SOYA, SU EFECTO EN LA ELABORACIÓN DE BIODIESEL

USE OF COMPREHENSIVE TWO-DIMENSIONAL GAS CHROMATOGRAPHY TO EVALUATE THE SHELF LIFE OF SOYBEAN OIL, ITS EFFECT IN THE MANUFACTURE OF BIODIESEL

N.G. Salazar-Mogollón 1,2^[1]*, Z. Niño Ruíz 3, R. Torres-Guitierrez 2, J. de Almeida 2, M. Ruilova-Cueva 3, C. Jácome-Pilco 3 y F. Augusto 1

1Instituto de Química, Universidade Estadual de Campinas (UNICAMP), Campinas, São Paulo, Brasil.

2 IKIAM - Universidad Regional Amazónica, Km 7 Via Muyuna, Tena, Napo, Ecuador.

3 Departamento de investigación, Universidad Estatal de Bolívar (UEB), Campus Universitario Laguacoto II, Km 1/2 , via San Simón, Cantón Guaranda, Provincia Bolívar, Ecuador.

Fecha de envío: 16, 10, 2016

Resumen:[pic 2]

El objetivo de este estudio fue determinar la diferenciación del biodiesel preparado a partir de aceites de soja regulares y envejecidos, a través de cromatografía de gases bidimensional integral, combinada con análisis de componentes principales (PCA), así como identificar los compuestos presentes en ambas materias primas. Para evaluar las muestras en el sistema 2D, se establecieron tres fases estacionarias secundarias: SBL-IL61, Supelcowax y HP-50. Los resultados mostraron que sólo el revestimiento secundario polar, SBL-IL61, fue capaz de percibir una diferencia crucial entre las muestras. La mayor diferencia se observó en la identificación en mayor concentración de ésteres metílicos de ácidos grasos poliinsaturados (FAME) en biodiesel de soja envejecido, tales como C20: 4n-6, C20: 5n-3, C20: 3 y C21: 5. Estos compuestos son muy propensos a la oxidación, lo que conduciría a la devaluación del biodiesel como producto final, por lo cual pueden ser utilizados como marcadores para la degradación del biodiesel. En consecuencia, esta técnica analítica es altamente recomendable por proporcionar una mayor detección de estos compuestos dependientes de la calidad del biodiesel.

Palabras clave: Análisis de Componentes Principales Multimódo, Biodiesel. Cromatografía gaseosa bidimensional completa (GC×GC)[pic 3]

Abstract:

The study aimed to determine the differentiation of biodiesel prepared from regular and aged soybean oils, through a comprehensive two-dimensional gas chromatography, combined with a main component analysis (PCA), as well as to identify the compounds present in both raw materials. In order to evaluate the samples in the 2D system, three secondary stationary phases were established: SBL-IL61, Supelcowax and HP-50. Results showed that only polar secondary coating, SBL-IL61, was able to perceive a crucial difference between the samples. The largest difference was observed in the identification of the highest concentration of polyunsaturated fatty acid methyl ester (FAME) in aged soybean biodiesel, such as C20: 4n-6, C20: 5n-3, C20: 3 and C21: 5. These compounds are quite prone to oxidation, which would lead to devaluation of biodiesel as a final product, thus may be used as markers for biodiesel degradation. In consequence, an analytical technique that provides increased detection of these biodiesel quality-dependent compounds is recommended.

Keywords: Biodiesel, Comprehensive Two-dimensional Gas Chromatography (GC×GC), Multiway Principal Component Analysis (MPCA).

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1. Introduction

Fossil-derived fuels, like petroleum and its derivates, they have become natural barriers in the areas of economic, environmental and energy security worlwide (Chhetri and Islam, 2008), thus forcing many countries to search for alternative substitutes, such as the biofuels, between them the biodiesel (Wang et al., 2015; Fungrui et al., 1999). The biodiesel is defined as a mixture of long-chain alkyl esters obtained by the reaction between vegetal or animal lipids. Virtually, many vegetable species may be considered a source for these lipids, such as soy, sunflower, palm, amongst others as animal fat. Hence, these fuels may present diverse chemical compositions, depending on the materials used for their preparation (Leung et al., 2010). However, in Brazil, of the entire production of biodiesel, approximately 85% of the total production comes from soy oil (Paulillo et al., 2007).

In addition, Brazil is among the highers producers and consumers of biodiesel in the world with an annual production of 2.4 billion liters, in 2010, and an installed capacity of roughly 5.8 billions, for the same year (Paulillo et al., 2007).

The quality of biodiesel is evaluated by means of physical-chemical tests, such as the stability offered against oxidation, acidity index, ester content, total glicerol and methanol (or ethanol) content (Ragonese et al., 2009). Thus, for a sample it may be considered appropriate for consumption, it must satisfy all established recommendations by the National Agency for Petroleum (ANP) (Agencia Nacional de Petróleo 2008/ R7, 2003).

However, if the sample shows results outside the specified range of one or more physical and chemical parameters it is considered irregular (Chen et al., 2014). In this sense, the composition of the raw materials can reflect some physical-chemical properties of the fuels, as its stability to the oxidation, density and the combustion efficiency. Thus, ultimately the quality of the biodiesel will be somewhat affected by the origin, age and nature of the raw material.

Therefore, the study of the raw materials is essential to predict the features that can the final product may have, since it is known that biodiesel from raw materials less unsaturated, such as biodiesel from palm oil, are more resistant to oxidation that other materials with a higher concentration of unsaturated compounds, such as soybean, corn and canola biodiesel (Ramos et al., 2009; Serrano et al., 2013)

Additionally, it was found that the time and conditions of storage of biodiesel can lead to a detrimental change in the amount of iodine, oxidation stability, peroxide values and cetane number (Pattamaprom et al., 2012; Bouaid et al., 2007). Therefore, prior knowledge of the status and quality of raw materials more prone to these changes is necessary.

Furthermore, to the knowledge of the authors, the existence of a certification protocol for these materials is still incipient. The percentual determination of the total fatty acid methyl esters (FAME) in biodiesel according to the standard regulatory norm EN 14103 is based on Gas Chromatography coupled with Flame Ionization Detection (GC-FID) where the ester content, expressed as a mass percentage is calculated (Ragonese et al., 2009). However, most of the chromatographic peaks are often a result of overlap of individual constituents and many minoritary compounds are often not detectable, in most conventional runs. In order to increase the reliability of these results a higher separation power is needed (Ragonese et al., 2009).

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