Rapid monitoring of transesterification and assessing biodiesel fuel quality by near‐infrared spectroscopy using a fiber‐optic probe

Knothe, Gerhard

doi:10.1007/s11746-999-0068-5

Cited by 137 publications

(94 citation statements)

References 22 publications

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“…NIR spectroscopy with multivariate analysis is a well-established, fast, reliable, inexpensive and non-destructive analytical technique, and does not require complex pre-treatment [32][33][34]. Among the various parameters which can be investigated, the initial ethanol to oil molar ratio was studied in this work.…”

Section: Introductionmentioning

confidence: 99%

On-line monitoring of the transesterification reaction carried out in microreactors using near infrared spectroscopy

Richard

Dubreuil

Thiébaud‐Roux

et al. 2013

Fuel

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Biodiesel can be produced from vegetable oils, animal fats, and waste cooking oils by transesterification with ethanol (also called ethanolysis) in order to substitute fossil fuels. In this work, the batch ethanolysis of high oleic sunflower oil was transferred into a continuous microstructured device, which induces a better control of heat and mass transfers. Various parameters were studied, notably the initial ethanol to oil molar ratio.An innovative method using NIR spectroscopy was also developed to on-line monitor the transesterification reaction of high oleic sunflower oil with ethanol in microreactors (circular PFA tube 1/16" OD, 0.02" ID). The reactions were monitored directly in the microreactors through sequential scans of the reaction medium by the means of an adequate probe. The asset of the method is that no sample collection or preparation is necessary. Partial least squares regression was used to develop calibration and prediction models between NIR spectral data and analytical data obtained by a reference method (gas chromatography with flame ionization detection, GC-FID). This method is fast, safe, reliable, non destructive and inexpensive contrary to conventional procedures, such as gas chromatography and high performance liquid chromatography generally used to determine the composition of crude transesterification medium.

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Section: Introductionmentioning

confidence: 99%

On-line monitoring of the transesterification reaction carried out in microreactors using near infrared spectroscopy

Richard

Dubreuil

Thiébaud‐Roux

et al. 2013

Fuel

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“…Some chromatographic methods have been created and improved to analyze the biodiesel 6 . Among these, thin layer chromatography (TLC), 7 gas chromatography (GC), 8 high-performance liquid chromatography (HPLC), [9][10][11] gel permeation chromatography (GPC), 12 nuclear magnetic resonance (NMR) 13 and near infrared spectroscopy (NIR) 14 are included.…”

Section: Introductionmentioning

confidence: 99%

Chromatographic analyses of fatty acid methyl esters by HPLC-UV and GC-FID

Carvalho¹,

Mendonça

Pinho³

et al. 2012

J. Braz. Chem. Soc.

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Um método analítico por cromatografia líquida de alto rendimento com detecção ultravioleta (HPLC-UV) (método A) foi utilizado na determinação simultânea dos valores totais de triacilglicerídeos, diacilglicerídeos, monoacilglicerídeos e ésteres metílicos de ácidos graxos na alcólise de diferentes óleos (algodão, canola, girassol, milho e soja). As análises foram realizadas a 40 °C por 20 min usando gradiente de metanol (MeOH) e 2-propanol-hexano 5:4 (v/v) (PrHex): 100% de MeOH em 0 min, 50% de MeOH e 50% de PrHex em 10 min mantido com eluição isocrática por 10 min. Outro método por HPLC-UV (método B) com eluição isocrática de acetonitrila por 34 min foi utilizado na determinação da composição de ácidos graxos de óleos analisando seus derivados de éster metílico. Os conteúdos foram analisados com satisfatória repetibilidade (desvio padrão relativo, RSD < 3%), linearidade (r 2 > 0,99) e sensibilidade (limite de quantificação). O método B foi comparado com o método oficial cromatográfico gasoso com detecção através de ionização por chama (GC-FID) da American Oil Chemists' Society (AOCS) na determinação de ésteres metílicos de ácidos graxos (FAME) em amostras reais de biodiesel.An analytical method using high performance liquid chromatography with UV detection (HPLC-UV) (method A) was used for simultaneous determination of total amounts of triacylglycerides, diacylglycerides, monoacylglycerides and fatty acid methyl esters in alcoholysis of different oil (cotton, canola, sunflower, corn and soybean) samples. Analyses were carried out at 40 °C for 20 min using a gradient of methanol (MeOH) and 2-propanol-hexane 5:4 (v/v) (PrHex): 100% of MeOH in 0 min, 50% of MeOH and 50% of PrHex in 10 min maintained with isocratic elution for 10 min. Another HPLC-UV method (method B) with acetonitrile isocratic elution for 34 min was used to determine the fatty acid composition of oils analyzing their methyl ester derivatives. Contents were determined with satisfactory repeatability (relative standard deviation, RSD < 3%), linearity (r 2 > 0.99) and sensitivity (limit of quantification). Method B was compared with an official gas chromatographic method with flame ionization detection (GC-FID) from American Oil Chemists' Society (AOCS) in the determination of fatty acid methyl esters (FAME) in biodiesel real samples.Keywords: biodiesel, triacylglycerides, gas chromatography, liquid chromatography, methyl ester IntroductionThe direct use of fats and oils (mainly composed by triacylglycerides) in diesel engines is problematic and can lead to many problems, such as carbon deposit due to its poor atomization, high viscosity and thickening of lubricating oil as a consequence of its low volatility. 1,2 There are many possible solutions to address the viscosity problem, which are dilution with diesel fuel, microemulsions with short chain alcohols and pyrolysis or transesterification of triacylglycerides. Transesterification is a widespread process used for obtaining biodiesel and involves the catalyzed reaction of triacylglycerides (TAGs) a...

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“…The authors entirely failed to note that the high acid B100 had a total glycerin level that was nearly six times the value of the on-specification B100 (0.180% vs. 0.029%). The glycerin and partial glycerol species that contribute to total glycerin levels are well known to cause severe engine deposits 121,126 . Although the total glycerin values of both fuels were within the 0.240% maximum allowed specification limit, the much greater difference of that compositional parameter is a more plausible explanation than the small difference in TAN values, based on the data that was explicitly provided, notated, and discussed within the actual text of the paper.…”

Section: Pump Testsmentioning

confidence: 99%

Characterization of Biodiesel Oxidation and Oxidation Products

2005

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This report must be reproduced in full,unless SwRI approves a summary or abridgement. iii EXECUTIVE SUMMARY Stability Chemistry FundamentalsChemical reactivity of fatty oils and esters can be divided into oxidative and thermal instability. Both of these types of instability are determined by the amount and configuration of the olefinic unsaturation on the fatty acid chains. Many of the plant-derived fatty oils, including soy and rapeseed, contain polyunsaturated fatty acid chains that are methylene-interrupted rather than conjugated. This structural fact is key to understanding both oxidative and thermal instability.In oxidative instability, the methylene carbons between the olefinic carbons are the sites of first attack. After hydrogen is removed from such carbons oxygen rapidly attacks and a hydroperoxide is ultimately formed where the polyunsaturation has been isomerized to include a conjugated diene. This reaction is a chain mechanism that can proceed rapidly once an initial induction period has occurred. The greater the level of unsaturation in a fatty oil or ester, the more susceptible it will be to oxidation. Once the hydroperoxides have formed, they decompose and inter-react to form numerous secondary oxidation products including aldehydes, alcohols, shorter chain carboxylic acids, and higher molecular weight oligomers often called polymers. Another polymerization mechanism, vinyl polymerization, has been proposed as being part of the degradation process of fatty oils and esters. However, conventional understanding of oxidation chemistry would imply that such processes would not be significant when oxygen was abundant, so its precise level of importance has not been determined.Metals, free fatty acids, acidic fuel additives, the size of the alcohol group (for mono-esters), and the presence of natural antioxidants can all impact the oxidative stability of fatty oils and/or esters. Oxidation can also be catalyzed by light, but such photo-oxidation should not be a significant factor for the manufacture and transportation of biodiesel fuel.Thermal polymerization of fatty oils and esters does not become important until temperatures of 250-300°C are reached. This is because the methylene-interrupted polyunsaturated structure cannot participate in such reactions until it isomerizes into a conjugated configuration, and such isomerization will not occur until that temperature range is reached. Thermal polymerization occurs by the Diels Alder reaction, and two fatty acid chains are linked by a cyclohexene ring. Higher order oligomers are also possible, although the exact mechanism is still not established. Certain thermal polymerization products in used cooking oils may carry over to non-distilled biodiesel. The verification of such compounds and their impact on fuel quality has not been determined. Thermal polymerization may be of limited importance in biodiesel fuel that is repeatedly heated by the engine and recycled to the fuel tank before actual combustion. However, thermal polymerization will not impact stor...

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Rapid monitoring of transesterification and assessing biodiesel fuel quality by near‐infrared spectroscopy using a fiber‐optic probe

Cited by 137 publications

References 22 publications

On-line monitoring of the transesterification reaction carried out in microreactors using near infrared spectroscopy

On-line monitoring of the transesterification reaction carried out in microreactors using near infrared spectroscopy

Chromatographic analyses of fatty acid methyl esters by HPLC-UV and GC-FID

Characterization of Biodiesel Oxidation and Oxidation Products

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