Quantitative Medium-Resolution NMR Spectroscopy Under Non-Equilibrium Conditions, Studied on the Example of an Esterification Reaction

Dalitz, Franz; Kreckel, Lennart; Maiwald, Michael; Guthausen, Gisela

doi:10.1007/s00723-014-0522-x

Cited by 34 publications

(51 citation statements)

References 24 publications

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“…The dimensions of the NMR probe and magnet system should be appropriate for providing uniform sample excitation and acquisition as well as initial pre-magnetization. On the other hand, measurements for non-equilibrium magnetization can be done [36], which makes a device simpler. In addition, the flow rate should be constant in both cases.…”

Section: Discussionmentioning

confidence: 99%

Molecular Properties of Fatty Acid Mixtures Estimated by Online Time-Domain NMR

Nikolskaya

Hiltunen

2018

Appl Magn Reson

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An approach based on time-domain nuclear magnetic resonance (TD-NMR) enables the estimation of the molecular properties of fatty acid mixtures-kinematic viscosity (µ), heating value (δ), cetane number (CN), and carbon chain length (CL). In this approach, the 1 H NMR spin-spin relaxation rates R 2 or times T 2 were used to determine these molecular properties. Online monitoring of the µ, δ, CN, and CL of fatty acid mixtures was performed using an online TD-NMR system that had been modified for flowing samples. The presented results show the potential of TD-NMR for online quality control during the production of liquid fuels.

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Section: Discussionmentioning

confidence: 99%

Molecular Properties of Fatty Acid Mixtures Estimated by Online Time-Domain NMR

Nikolskaya

Hiltunen

2018

Appl Magn Reson

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“…Reaction monitoring, involving prior knowledge about possible reaction mechanisms are a predestinated application field for IHM. The later approach using prior knowledge about the chemical reaction and the multiplet structure was found to work also for rather signal-to-noise limited MR-NMR spectra [17].…”

Section: Introductionmentioning

confidence: 98%

“…In order to gain the highest possible S/N ratio in a flowing fluid, its flow rate has to be limited with respect to a sufficiently long effective polarisation length, otherwise, non-equilibrium effects have to be considered [17]. The adaption of commercially available devices for online measurements additionally requires considerations on flow effects and optimisation of flow probes in respect to sensitivity and selectivity.…”

Section: Introductionmentioning

confidence: 99%

“…Since only recently promising MR-NMR benchtop instruments with acceptable performance came to market, a process integrated instrument could accordingly be developed on the basis of presently emerging laboratory instruments. Within this study, a different approach from [16][17][18][19][20][21][22] was realised: A simple 1/16 00 FEP tube with an ID of 0.04 00 (1.02 mm) was used as a flow probe. The thermal isolation between the flow tube and the NMR probe was realised with a simple 5 mm glass Dewar tube inserted into a benchtop MR-NMR spectrometer.…”

Section: Introductionmentioning

confidence: 99%

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Simultaneous 19F–1H medium resolution NMR spectroscopy for online reaction monitoring

Zientek

Laurain

Meyer

et al. 2014

Journal of Magnetic Resonance

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“…[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.…”

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confidence: 99%

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

Kollar¹,

Novotny²,

Nascimento³

et al. 2017

J. Braz. Chem. Soc.

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In this work, we compared 1.40 T nuclear magnetic resonance (NMR) to 7.05 T (60 and 300 MHz for proton, respectively), and mid-infrared with attenuated total reflectance (FTIR-ATR), associated with chemometrics methods, for the quantification of the reaction yield during esterification of fatty acids with methanol. The results showed that the integrated intensities of the ester C=O stretching region, relative to the total C=O stretching region, is useful to quantify the fatty acid methyl ester (FAME) concentration. Comparing the results obtained by the different final models: NMR (1.40 T and 7.05 T), FTIR-ATR using multivariate partial last squares regression (PLS) with orthogonal signal correction (OSC), and univariate ordinary least squares (OLS), the NMR of 1.40 T (60 MHz for proton) showed more advantages when compared to a high field spectrometer, due to the non-use of cryogenic and solvents and less laborious work for obtaining results. Keywords: biodiesel, esterification, mid-infrared, q-NMR, chemometrics IntroductionThe interest for using alternative fuels has grown in the last decade. 1 The increasing demand for energy and environmental awareness are leading researchers to look for new environmentally acceptable renewable resources. In this context, the interest for biodiesel has increased a lot since it is produced using renewable resources (oils and fats from both vegetable and animal sources), it is biodegradable, and it can be directly placed on diesel engines without any mechanical modifications, due to their similar physical chemical properties. Also it does not contain sulfur compounds, it releases less particulate matter and it is less toxic. 2,3The most common method used to produce biodiesel is the transesterification of fats and oils, using a strong base as catalyst (like NaOH, KOH or KOCH 3 ). It consists in the reaction between triacylglycerides and short chain alcohols to produce esters and glycerol. It is a reversible process and excess of alcohol is used for moving the equilibrium towards the products. However, this process needs feedstocks containing low concentrations of free fatty acids and water because they react with the basic catalysts forming soaps which hinders the purification of the biodiesel, increasing the cost of the production. 4 An alternative way is the esterification of fatty acids. 5,6 This reaction normally uses homogeneous acid catalysis with strong Brønsted acids such as H 2 SO 4 and HCl that are corrosive and should be neutralized when the process is finished. To overcome this problem, solid Lewis acids can be used allowing easy separation and continuous operation in reactors. 2The most common method used to monitor the reaction yield during the esterification is the determination of the amount of fatty acids, usually performed using chromatographic methods or titration with alcoholic solution of KOH (method described by AOCS Cd 3a-63). 7,8 Despite being very effective methods for this kind of analysis, they have the disadvantage of consuming large amounts of organ...

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Quantitative Medium-Resolution NMR Spectroscopy Under Non-Equilibrium Conditions, Studied on the Example of an Esterification Reaction

Cited by 34 publications

References 24 publications

Molecular Properties of Fatty Acid Mixtures Estimated by Online Time-Domain NMR

Molecular Properties of Fatty Acid Mixtures Estimated by Online Time-Domain NMR

Simultaneous 19F–1H medium resolution NMR spectroscopy for online reaction monitoring

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

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