Fast synthesis of micro/mesoporous xerogels: Textural and energetic assessment
[Display omitted] •Fast synthesis of micro–mesoporous gels within less than a day.•The gelation/aging step controls the formation of the mesoporous network.•Mild sol–gel polymerization created curvatures in the N2 adsorption isotherms.•Balance of porosity and energy costs is a useful tool for indust...
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| Published in: | Microporous and mesoporous materials 2015-06, Vol.209, p.2-9 |
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| Main Authors: | , , , , , , |
| Format: | Article |
| Language: | eng |
| Subjects: | |
| Online Access: | Get full text |
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| Summary: | [Display omitted]
•Fast synthesis of micro–mesoporous gels within less than a day.•The gelation/aging step controls the formation of the mesoporous network.•Mild sol–gel polymerization created curvatures in the N2 adsorption isotherms.•Balance of porosity and energy costs is a useful tool for industrial scale.•Chemical activation avoided the structural collapse and created bimodal PSDs.
The sol–gel polymerization of resorcinol/formaldehyde mixtures to obtain porous gels is typically a long process performed throughout several days. In this work, we have explored an experimental approach to reduce the time necessary to obtain porous gels based on mild polymerization conditions and direct drying. We have analyzed the effects of the temperature and time of the gelation/aging step on the porosity of the gels, as well as the impact on the overall energetic cost of the process. Data have shown that well-developed micro–mesoporous architectures can be obtained within less than a day. The temperature of the gelation/aging step mainly affects the mesopore network, whereas the microporosity is determined by the composition of the precursor’s mixture. The exclusion of the solvent exchange step yields soft mechanically fragile porous gels with structural limitations upon carbonization at high temperature in inert atmosphere, due to the surface tensions applied to the backbone during the evolution of volatiles. The mesopore structure lost during carbonization is not recovered upon activation in CO2 atmosphere, but it is preserved upon chemical activation in K2CO3 and the resulting gel exhibits a bimodal micro–mesoporous distribution. Furthermore, the energy savings of this route are similar to those obtained using microwave-heating in terms of grams of xerogel per kilowatt hour of energy consumed for similar textural properties. The correlation between the energy power consumed and the textural parameters is a useful tool to optimize the synthesis. |
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| ISSN: | 1387-1811 1873-3093 |