1H- and 13C-NMR-Spectroscopic Study of Chemical Equilibria in Solutions of Formaldehyde in Water, Deuterium Oxide, and Methanol

Hahnenstein, Immanuel; Hasse, Hans; Kreiter, Cornelius G.; Maurer, Gerd

doi:10.1021/ie00028a033

Cited by 128 publications

(177 citation statements)

References 5 publications

(5 reference statements)

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“…10,11 In this system the selectivity of formaldehyde towards OME is limited by the competing reactions of formaldehyde with methanol and water towards poly(oxymethylene) glycols and poly(oxymethylene) hemiformals. [25][26][27] Zhang et al did not mention these competing reactions. Drunsel et al investigated chemical equilibrium and reaction kinetics for the synthesis of methylal from methanolic formaldehyde solutions with a small amount of water over an acidic heterogeneous catalyst.…”

Section: Introductionmentioning

confidence: 99%

Chemical Equilibrium of the Synthesis of Poly(oxymethylene) Dimethyl Ethers from Formaldehyde and Methanol in Aqueous Solutions

Schmitz

Homberg

Berje

et al. 2015

Ind. Eng. Chem. Res.

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112

176

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Poly(oxymethylene) dimethyl ethers (OME) reduce the soot formation during the combustion process, when added to diesel fuels. OME are a Gas-to-Liquid (GtL) option as they can be produced via methanol from natural gas or renewable feedstocks. This work deals with the synthesis of OME from the educts formaldehyde and methanol in aqueous solutions. The studied mixtures are complex reacting systems in which besides OME, also poly(oxymethylene) glycols and poly(oxymethylene) hemiformals are present. The chemical equilibrium of the OME formation is studied in a stirred batch reactor varying in the educts' overall ratio of formaldehyde to methanol and the amount of water and varying the temperature between 333.15 K and 378.15 K. A mole fraction-based, as well as an activity-based model of the chemical equilibrium of the OME formation are developed, which explicitly account for the formation of poly(oxymethylene) glycols and poly(oxymethylene) hemiformals. Information on the latter reactions from literature are confirmed by NMR experiments in the present work.

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Section: Introductionmentioning

confidence: 99%

Chemical Equilibrium of the Synthesis of Poly(oxymethylene) Dimethyl Ethers from Formaldehyde and Methanol in Aqueous Solutions

Schmitz

Homberg

Berje

et al. 2015

Ind. Eng. Chem. Res.

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112

176

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“…The research group of Maurer recently studied the kinetics and X Deceased. chemical equilibria of the polyoxymethylene glycol formation (Hasse & Maurer, 1991;Hahnenstein, Hasse, Kreitler, & Maurer, 1994b;Hahnenstein, Albert, Hasse, Kreitler, & Maurer, 1994a).…”

Section: Introductionmentioning

confidence: 99%

Kinetics and chemical equilibrium of the hydration of formaldehyde

Winkelman

Voorwinde

Ottens

et al. 2002

Chemical Engineering Science

125

145

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Take-down policy If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim. AbstractThe reaction rate of the hydration of formaldehyde is obtained from the measured, chemically enhanced absorption rate of formaldehyde gas into water in a stirred cell with a plane gas-liquid interface, and mathematically modelling of the transfer processes. Experiments were performed at the conditions prevailing in industrial formaldehyde absorbers, i.e. at temperatures of 293-333 K and at pH values between 5 and 7. The observed rate constants could be correlated as k h = 2:04 × 105 × e −2936=T s −1 . Using the results, and the dehydration reaction rate constant, obtained previously at similar conditions, the chemical equilibrium constant for the hydration is obtained as K h =e 3769=T −5:494 .

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“…Chemical shifts of the species identified in the reaction system 1,3-dimethylurea-formaldehyde, Part I (hydroxymethylation products). The chemical shifts of formaldehyde FA and the methyleneglycols MG 1:::10 can be found elsewhere [4,14,15] [23,24] Because of this evidence, the formation of ether bridges has been taken into account in the present study in the reaction kinetic model. More details on the indications supporting the formation of ether bridges as found during the course of the present work are provided in the Supplementary Information.…”

Section: Ether Bridgesmentioning

confidence: 99%

“…Therefore, the formaldehyde-water system will be discussed here briefly, as it has been studied, characterized, and described in depth elsewhere. [13][14][15] It is usually described by the following reactions:…”

Section: Formaldehyde-watermentioning

confidence: 99%

Investigation of the reaction of 1,3‐dimethylurea with formaldehyde by quantitative on‐line NMR spectroscopy: a model for the urea–formaldehyde system

Steinhof

Scherr

Hasse

2015

Magnetic Reson in Chemistry

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Quantitative on-line NMR spectroscopy is applied to study equilibria and reaction kinetics of the reaction of formaldehyde with 1,3-dimethylurea. This reaction system serves as a model system for the much more complex but industrially relevant urea-formaldehyde system. The aim is to study individual reactions and intermediates. The 1,3-dimethylurea-formaldehyde system undergoes only four reactions and, unlike urea-formaldehyde, does not form polymers. The following reactions are studied in detail: (1) the hydroxymethylation, (2) the formation of hemiformals of the hydroxymethylated intermediate, and (3) two condensation reactions of which the first leads to methylene bridges, the other to ether bridges. NMR spectroscopic chemical shift data of the reacting species are provided for the (1) H, (13) C, and (15) N domains. Equilibrium data of reactions (1), (2), and (3) are determined by quantitative (1) H and (13) C NMR spectroscopy at molar ratios of formaldehyde to 1,3-dimethylurea between 1:2 and 16:1 at a pH value of 8.5. Reaction kinetic experiments using an NMR spectrometer coupled to a batch reactor led to a reaction kinetic model parametrized with true species concentrations. The model takes into account reactions (1), (2), and (3). It describes the reaction system well for molar ratios of 1:1, 2:1, and 4:1, temperatures of 303 to 333K, and pH values from 5.0 to 9.5. Dilution experiments with a micro mixer coupled to the NMR spectrometer are conducted to estimate the time to equilibrium of reaction (2) of which the time constant is significantly lower than those of reactions (1) and (3). Copyright © 2015 John Wiley & Sons, Ltd.

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1H- and 13C-NMR-Spectroscopic Study of Chemical Equilibria in Solutions of Formaldehyde in Water, Deuterium Oxide, and Methanol

Cited by 128 publications

References 5 publications

Chemical Equilibrium of the Synthesis of Poly(oxymethylene) Dimethyl Ethers from Formaldehyde and Methanol in Aqueous Solutions

Chemical Equilibrium of the Synthesis of Poly(oxymethylene) Dimethyl Ethers from Formaldehyde and Methanol in Aqueous Solutions

Kinetics and chemical equilibrium of the hydration of formaldehyde

Investigation of the reaction of 1,3‐dimethylurea with formaldehyde by quantitative on‐line NMR spectroscopy: a model for the urea–formaldehyde system

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