The reaction of phenol with formaldehyde: II. The ratio of <i>ortho‐</i> and <i>para</i>‐hydroxymethylphenol in the base‐catalyzed hydroxymethylation of phenol.

Peer, H. G.

doi:10.1002/recl.19590781102

Cited by 40 publications

(3 citation statements)

References 15 publications

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“…Each amine group can react with up to two F molecules, leading to up to six reaction sites on an individual M molecule ( Figure 5). In theory, the MF reaction, as also expected for RF gels, may undergo a similar stabilisation step ( Figure 6), as previously proposed for phenolic systems [15]. The intermediate structure results from the differences in partial charges on the nitrogen atoms of melamine, potentially further stabilised by the presence of the metal cations, contributed by the catalyst.…”

Section: Melamine-formaldehyde Gelssupporting

confidence: 70%

Effect of Aromatic Amines on the Properties of Formaldehyde-Based Xerogels

Martin

Prostredny

Fletcher

2020

Gels

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This study investigates the synthesis of formaldehyde-based xerogels using alternative aromatic precursors, with comparison to traditional resorcinol-formaldehyde analogues, in order to alter the chemical composition of the resulting gels. By replacing resorcinol with aromatic amine molecules, i.e., ammeline, melamine and melem, each expected to undergo similar reactions with formaldehyde as the substituted species, we found that for all substituted gels, at low additive contents, the gel structure was compromised and non-porous materials were formed, as opposed to the most abundant monomers, and therefore, these additives seem to act as impurities at low levels. Working towards higher additive contents, melem monomers exhibited low solubility (~5%), even at elevated temperatures, thereby limiting the range to which melem could act as a substitute, while melamine could be incorporated up to ~40% under acidic conditions, with enhanced microporosity over this range. Pure gels were successfully synthesised from ammeline, but their performance was inferior to resorcinol-formaldehyde gels, while melamine-formaldehyde analogues required acidic reaction conditions but shrank considerably on sub-critical drying, adversely affecting the gel properties and demonstrating their lack of potential as sorbents. This demonstrates the potential for the inclusion of aminated aromatics within resorcinol-based gel systems, however, only as partial substitutes and not complete replacements.

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Section: Melamine-formaldehyde Gelssupporting

confidence: 70%

Effect of Aromatic Amines on the Properties of Formaldehyde-Based Xerogels

Martin

Prostredny

Fletcher

2020

Gels

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“…Rate constants of all reactions of Figure 1 are reported in literature by Freeman and Lewis (1954), Minami and Ando (1956), Peer (1959), Zavitsas (1968), Eapen and Yeddanapalli (1968), Aldersley and Hope (1972), Higuchi et al (1999), but all are below 100°C. We need the values of rate constants at around 140°C for our kinetic analysis.…”

Section: Estimation Of Reaction Rate Constants At 140°cmentioning

confidence: 62%

Studies on Phenol‐Formaldehyde Gel Formation at a High Temperature and at Different pH

Banerjee¹,

Patil

Khilar

2006

Can J Chem Eng

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une solution de phénol-formaldéhyde dans l'eau à une température élevée proche de 140 °C. On a trouvé expérimentalement qu'à une température entre 135 °C et 140 °C, une solution contenant 3,0 % de phénol avec un rapport molaire de phénol-formaldéhyde de 1,0:3,5 formait un gel ayant un pH compris entre 9,6 et 12,0. Le temps de gélifi cation minimum est observé à une valeur de pH de 10,4. La formation de gel s'avère fortement dépendante du pH à cette température élevée. On présente une explication pour le comportement de gélifi cation, qui s'appuie sur une concentration d'ions optimale de Na+ pour initier la formation de tri-méthylol. On pose comme hypothèse que la formation de gel commence quand la concentration de phénol de tri-méthylol atteint une valeur de concentration seuil. Des observations expérimentales et une analyse cinétique appuient cette hypothèse.

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“…[ 2–5 ] Conventionally, both forms of phenol formaldehyde (PF) namely, resole and novalacs are manufactured through batch reactors. [ 6–10 ] Very high exothermicity and difficulties in controlling polymerization, along with possible runaway reactions, have been identified as the serious disadvantages of batch reactors. [ 11 ] Numerous accidents have occurred due to high exothermic reaction, leading most of the time, to the complete destruction of the chemical plant.…”

Section: Introductionmentioning

confidence: 99%

Novel Protocol for Resole Phenol Formaldehyde Resins Synthesis with Tubular Reactor and Characterization

Pullichola

Varghese

Unnikrishnan

et al. 2021

Macro Reaction Engineering

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A novel strategy has been established, in the laboratory scale, for the generation of the popular thermosetting resin phenol formaldehyde (PF; resole), through a continuous process using a tubular reactor, which is usually developed in the commercial scale through a batch process. A refractive index technique is employed to evaluate the optimum residence time within the tubular reactor to obtain a commercial grade equivalent of PF resin. The unreacted free formaldehyde level has been found to be very low in the resole resin prepared by using the new route. The initial characterization of the resin has been done through Fourier transform infrared spectroscopy and gel permeation chromatography. The cure characteristics of the resin have been analyzed through differential scanning calorimetry. The degradation features of the cured resole are investigated using a thermo gravimetric analyzer and the fractured surfaces are analyzed through scanning electron microscopy. It has been confirmed that the adverse effects of a batch reactor process can be significantly reduced by adopting a continuous resin manufacturing process for PF resin which can be successfully extended to commercialization after optimization.

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The reaction of phenol with formaldehyde: II. The ratio of ortho‐ and para‐hydroxymethylphenol in the base‐catalyzed hydroxymethylation of phenol.

Cited by 40 publications

References 15 publications

Effect of Aromatic Amines on the Properties of Formaldehyde-Based Xerogels

Effect of Aromatic Amines on the Properties of Formaldehyde-Based Xerogels

Studies on Phenol‐Formaldehyde Gel Formation at a High Temperature and at Different pH

Novel Protocol for Resole Phenol Formaldehyde Resins Synthesis with Tubular Reactor and Characterization

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