Continuous Catalyst-Free Esterification of Oleic Acid in Compressed Ethanol

Abstract

The esterification of oleic acid in a continuous catalyst-free process using compressed ethanol was investigated in the present study. Experiments were performed in a tubular reactor and variables investigated were temperature, pressure, and oleic acid to ethanol molar ratio for different residence time. Results demonstrated that temperature, in the range of 473 K to 573 K, and pressure had a positive effect on fatty acid ethyl esters (FAEE) production. In the experimental range investigated, high conversions can be obtained at low ethanol concentrations in the reaction medium and it was observed that oleic acid to ethanol molar ratios greater than 1 : 6 show no significant increase in conversion. Nonnegligible reaction conversions (>90%) were achieved at 573 K, 20 MPa, oleic acid to ethanol molar ratio of 1 : 6, and 20 minutes of residence time.

Assessment of process variables on the use of macauba pulp oil as feedstock for the continuous production of ethyl esters under pressurized conditions

“…The FFA content was determined by the Ca 5a-40 method (AOCS, 1998) and FFA conversion was calculated based on the content of free fatty acids in the oil and in samples of the reaction medium, as reported by Abdala et al (2014a). Table 3 presents the matrix of the Plackett and Burman design with 12 assays (PB-12), with coded values for the independent (factors) variables: temperature, pressure, MPO to ethanol mass ratio, water and co-solvent addition, with the response in terms of FAEE yield and FFA conversion.…”

“…Abdala et al (2014a) reported high conversion of oleic acid, i.e. 70%, in the reaction with ethanol at 20 MPa, with 1:1 oleic acid to ethanol mass ratio and 10 minutes at 473 K; this conversion increased to 88% at 573 K.…”

“…The work of Abdala et al (2014a) reported that an increase in pressure from 15 to 20 MPa favors the conversion of oleic acid in ethanol for reaction times of 20 to 30 min using 1:6 oleic acid to ethanol molar ratio and temperatures of 523 and 528 K. Another study of interest is that of Wang et al (2008), who investigated the effect of pressure on the reaction of soybean oil and a mixture of soybean oil+oleic or stearic acid with supercritical methanol and reported an increase in yield after increasing the pressure from 9 to 15 MPa.…”

“…This was also seen in the work by Doná et al (2013) for obtaining macauba biodiesel from interesterification with methyl acetate in supercritical conditions. The esterification reaction rate is faster than transesterification, and higher conversion of FFA can be obtained in subcritical conditions, as reported in the works of Vieitez et al (2012) and Abdala et al (2014a). Thus, since the MPO has high FFA levels, evaluation of the experimental conditions to allow the use of alcohol in subcritical conditions in the process has become a focus of study, and was not evaluated in the work by Navarro-Díaz et al (2014).…”

Evaluation of the use of degummed soybean oil and supercritical ethanol for non-catalytic biodiesel production

“…The acidity of this oil was 0.76%, humidity of 0.16% and phosphorus content of 77.86 ppm. The percentage of free fatty acid (acidity) was determined following the method used by Abdala et al [8], based on the AOCS Official Method Ca 5a-40, which uses an acid-base titration. The titrant is an ethanol solution of potassium hydroxide (KOH) previously standardized.…”