Impact of synthesis conditions on meso- and macropore structures of resorcinol–formaldehyde xerogels

Awadallah‐F, Ahmed; Elkhatat, Ahmed M.; Al‐Muhtaseb, Shaheen A.

doi:10.1007/s10853-011-5755-6

Cited by 28 publications

(18 citation statements)

References 24 publications

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“…If no additional water was used, the term 'standard synthesis' was used. with other literature data [70].…”

Section: Synthesis Of Native Rf-xerogelsupporting

confidence: 80%

“…The pore volume of 0.16 cm 3 ·g -1 and the BET surface area of 100 m 2 ·g -1 , both calculated from the N 2 adsorption isotherm, are typical values for subcritically dried R,F-xerogels with the following molar ratios of the starting materials: resorcinol/formaldehyde = 0.73, resorcinol/Na 2 CO 3 = 1000, resorcinol/water = 0.031 (Table 1) [60,70,72].…”

Section: Synthesis Of Native Rf-xerogelmentioning

confidence: 97%

“…4c). The morphology can be described as interconnected colloidal-like particles, which do not possess porosity themselves, but generate porosity between the gaps of the particles [60,70].…”

Section: Synthesis Of Native Rf-xerogelmentioning

confidence: 99%

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Hierarchical MOF-xerogel monolith composites from embedding MIL-100(Fe,Cr) and MIL-101(Cr) in resorcinol-formaldehyde xerogels for water adsorption applications

Wickenheisser

Herbst

Tannert

et al. 2015

Microporous and Mesoporous Materials

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Shaping of otherwise powdery metal-organic frameworks is recognized as a more-and-more important issue to advance them to the application stage. Monolithic MOF composites were synthesized using micro-to-mesoporous MIL-100(Fe,Cr) and MIL-101(Cr) as thermally and chemically stable MOFs together with a mesoporous resorcinol-formaldehyde based xerogel as binding agent. The monolithic bodies could be loaded with up to 77 wt% of powdery MIL material under retention of the MIL surface area and porosities (from N 2 adsorption) by prepolymerization of the xerogel solution. The obtained monoliths are mechanically stable and adsorb close to the expected water vapor amount according to the MIL weight percentage.There is no loss of BET surface area, porosity and water uptake capacity especially for the MIL-101(Cr) composites. Water vapor adsorption isotherms show that the 77 wt% MIL-101(Cr) loaded composite even features a slightly increased water vapor uptake compared to pure MIL-101(Cr) up to a relative vapor pressure of P·P 0 -1 = 0.5. These hydrophilic monolithic composites could be applied for heat transformation application such as thermally driven adsorption chillers or adsorption heat pumps.

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“…If no additional water was used, the term 'standard synthesis' was used. with other literature data [70].…”

Section: Synthesis Of Native Rf-xerogelsupporting

confidence: 80%

Section: Synthesis Of Native Rf-xerogelmentioning

confidence: 97%

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Hierarchical MOF-xerogel monolith composites from embedding MIL-100(Fe,Cr) and MIL-101(Cr) in resorcinol-formaldehyde xerogels for water adsorption applications

Wickenheisser

Herbst

Tannert

et al. 2015

Microporous and Mesoporous Materials

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“…Due to the nanoporosity (pore size less than 100 nm) the samples were dried with supercritical carbon dioxide to avoid shrinkage otherwise caused by high surface tension gradients [2]. Several investigations have been published on the impact of synthesis and gelation conditions [3][4][5], influence of catalyst type [6] and pH value [7], catalyst and resorcinol amounts [8,9], and drying method [10,11] on the properties of RF aerogels. In contrast, only few studies exist on mechanical properties of RF aerogels [12][13][14].…”

Section: Introductionmentioning

confidence: 99%

From hard to rubber-like: mechanical properties of resorcinol–formaldehyde aerogels

et al. 2015

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Four types of resorcinol-formaldehyde (RF) aerogels, stiff, brittle, low-flexible, and super-flexible are studied in this work. Despite several studies on mechanical properties on RF aerogels their response when exposed to compressive loading and their fracture behavior are not well investigated. Here, we cover aerogels with a very broad density range of 0.08-0.3 g cm -3 and compressive moduli from 0.12 to 28 MPa. We relate the microstructure of the synthesized aerogels and their behavior under uniaxial compression. Additionally, this work is the first, to our knowledge, to implement the usage of digital image correlation for characterizing the deformation of RF aerogels. The comparison of surface strain distribution of four types of aerogels provides an insight to their reaction on compressive loading.

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“…Physical properties of the pore structure like surface area, pore volume, and pore size distribution (PSD) are drastically altered by different synthesis conditions. The initial gel pH and the resorcinol‐to‐catalyst ratio of the RF solution are important synthesis factors that affect the structural properties of the RF gels . The effect of different chemical catalysts on the gel properties is believed to be due to their effect on the pH of the precursor solution .…”

Section: Introductionmentioning

confidence: 99%

Resorcinol formaldehyde xerogels modified with mercapto functional groups as mercury adsorbent

Motahari

Heidari

Motlagh

2015

J of Applied Polymer Sci

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Resorcinol formaldehyde xerogels are modified by mercaptopropyl-trimethoxysilane during the sol-gel process used to produce the xerogel. The chemical modification is confirmed by Fourier-transform infrared spectroscopy. The xerogel is then used to adsorb mercury ions from aqueous solutions. The effects of the molar ratios of the precursors as well as the catalyst and the modifier are studied on the textural properties of the xerogel and the adsorption efficiency. It is shown that the chemical modification of the resorcinol formaldehyde xerogels creates the chemical sites on the structure of the xerogel to adsorb more mercury ions and increase the adsorption efficiency. At the same time, chemical modification decreases the xerogel surface area which results in a reduction of the mercury adsorption. Therefore, there exists an optimum value for the chemical modification of the xerogel to achieve the highest adsorption efficiency. Adsorption kinetics as well as equilibrium isotherm of xerogels were examined using pseudo-first-and secondorder kinetic equations, and Freundlich and Langmuir isotherm models. The adsorption kinetics was found to follow the pseudosecond-order kinetic equations. The experimental data was also fitted into the Longmuir model more precisely comparing the Freundlich model. Finally, a series of mercury adsorption-desorption tests proved that the optimized mercapto-modified resorcinol formaldehyde xerogel was an efficient reusable adsorbent for mercury ions.

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Impact of synthesis conditions on meso- and macropore structures of resorcinol–formaldehyde xerogels

Cited by 28 publications

References 24 publications

Hierarchical MOF-xerogel monolith composites from embedding MIL-100(Fe,Cr) and MIL-101(Cr) in resorcinol-formaldehyde xerogels for water adsorption applications

Hierarchical MOF-xerogel monolith composites from embedding MIL-100(Fe,Cr) and MIL-101(Cr) in resorcinol-formaldehyde xerogels for water adsorption applications

From hard to rubber-like: mechanical properties of resorcinol–formaldehyde aerogels

Resorcinol formaldehyde xerogels modified with mercapto functional groups as mercury adsorbent

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