Determination of the Kinetics of Biodiesel Production Using Proton Nuclear Magnetic Resonance Spectroscopy (¹H NMR)

Abstract

Methyl esters were produced at several temperatures (10, 35, and 45 °C) by transesterification batch reactions of soybean oil with methanol utilizing KOH and NaOH catalysts. The reactions were monitored by aliquot removal and subsequent proton nuclear magnetic resonance spectroscopy (1H NMR) analysis. 1H NMR analysis allowed for the calculation of the average degree of fatty acid unsaturation (DU = 1.52) in oil and methyl ester. 1H NMR analysis also provided initial rates of methyl ester formation and an activation energy of 27.2 kJ/mol. The time-dependent concentration data revealed substantial reaction progress toward equilibrium after only 120 s at a reduced temperature of 10 °C. Understanding the resonance shifts in the 1H NMR spectra of starting materials and products allows for quantitation of reaction progress that is in good agreement with results obtained using other analytical methods.

超音波照射によるトリオレインとエタノールのエステル交換反応に与えるモル比，触媒濃度および温度の影響

“…30 kJ/mol based on the slope at 3-20 C and ca. 10 kJ/mol at 20-50 C. Recently, the apparent activation energy was reported as 27.2 kJ/ mol for methyl ester formation with NaOH catalyst under stirring 33) . Therefore, the apparent activation energy at 3-20 C under ultrasonic irradiation was almost the same as that under stirring.…”

“…Here, the initial rate of reaction was used instead of k to analyze the appark to analyze the appark ent activation energy. This calculation method was described by Morgenstern et al 33) . Figure 5 shows the Arrhenius plot of ln(rate) vs. 1/T, T, T where the unit of rate is /min, obtained under ultrasonic irradiation.…”

Biodiesel: parâmetros de qualidade e métodos analíticos

“…A 43 e para identificação dos intermediários produzidos durante a reação. 33 A quantificação de ésteres em biodiesel por 1 H RMN tem sido classificada como mais rápida e mais simples do que quando realizada por HTGC ou HPLC, no entanto deve-se levar em consideração o custo do equipamento e de sua manutenção.…”

“…43 Por outro lado, as técnicas instrumentais associadas permitem uma rápida e fácil aquisição de dados que, quando tratados por análise multivariada, possibilitará a quantificação de analitos, mesmo na presença de interferentes. Estas são condições básicas para o monitoramento da reação de transesterificação in situ.…”

Nuclear Magnetic Resonance (1.40 T) and Mid Infrared (FTIR-ATR) Associated with Chemometrics as Analytical Methods for the Analysis of Methyl Ester Yield Obtained by Esterification Reaction

“…[19][20][21][22][23] It has also been used for identifying intermediates and for quantifying yields of fatty acid methyl esters (FAME) in the esterification and transesterification reactions. [24][25][26][27][28][29] Despite being a great technique for those purposes, it is not still very popular and not applied currently in industry due to the very expensive maintenance of a high-field NMR spectrometer, including cryogens, and the need of deuterated solvents for the analysis.In this work, we used a 1.40 T NMR spectrometer (60 MHz for proton) for the quantification of the reaction yield of the esterification reaction of fatty acids to produce FAME. The results were compared to that obtained on a 7.05 T high field spectrometer (300 MHz for proton) and also with a Fourier transformed infrared (FTIR) method associated with chemometrics analysis.…”