4. Conclusion
D.P. Bezerra et al. / Applied Surface Science 314 (2014) 314–321 321 References
Zeolite 13X has been impregnated with monoethanolamine (MEA) from methanolic solutions with increasing concentrations. Texture and surface chemistry of the thus-prepared materials have been investigated by nitrogen adsorption/desorption isotherms, TGA, FTIR and XPS. It has been shown that MEA tends to obstruct the micropores of the zeolite. TGA and XPS analyses reveal that part of the loaded amine is firmly attached to the adsorbent surface. Nevertheless, not much of this covalently bonded amine is avail- able for chemisorption. As a result, amine loaded zeolites adsorb less than the pristine material at a given temperature, but they tend to increase CO2 uptake as temperature rises. Such behav- ior together with measured calorimetric data confirms that there are chemisorption sites for CO2. The amine-grafted materials did not show superior adsorption capacities than the pristine sample, however they revealed important features and adsorptive prop- erties that can lead to new studies. Therefore, though apparently discouraging, these results confirm that amine functionalization generates much stronger adsorption sites on the surface, which potentially leads to higher CO2 selectivity. Nevertheless, this advan- tage is overcast by the restricted accessibility of such sites in microporous matrices and it is likely mesoporous solids (or rather micro-meso structures) are better options for amine impregna- tion.
Acknowledgements
The authors thank CNPq for funding D.P. Bezerra (554049/2010- 4), the financial support of Grant 295156, FP7-PEOPLE-2011-IRSES of the European Commission and project of excellence RNM 1565 of Junta de Andalucı ́a.
4. ConclusionD.P. Bezerra et al. / Applied Surface Science 314 (2014) 314–321 321 ReferencesZeolite 13X has been impregnated with monoethanolamine (MEA) from methanolic solutions with increasing concentrations. Texture and surface chemistry of the thus-prepared materials have been investigated by nitrogen adsorption/desorption isotherms, TGA, FTIR and XPS. It has been shown that MEA tends to obstruct the micropores of the zeolite. TGA and XPS analyses reveal that part of the loaded amine is firmly attached to the adsorbent surface. Nevertheless, not much of this covalently bonded amine is avail- able for chemisorption. As a result, amine loaded zeolites adsorb less than the pristine material at a given temperature, but they tend to increase CO2 uptake as temperature rises. Such behav- ior together with measured calorimetric data confirms that there are chemisorption sites for CO2. The amine-grafted materials did not show superior adsorption capacities than the pristine sample, however they revealed important features and adsorptive prop- erties that can lead to new studies. Therefore, though apparently discouraging, these results confirm that amine functionalization generates much stronger adsorption sites on the surface, which potentially leads to higher CO2 selectivity. Nevertheless, this advan- tage is overcast by the restricted accessibility of such sites in microporous matrices and it is likely mesoporous solids (or rather micro-meso structures) are better options for amine impregna- tion.AcknowledgementsThe authors thank CNPq for funding D.P. Bezerra (554049/2010- 4), the financial support of Grant 295156, FP7-PEOPLE-2011-IRSES of the European Commission and project of excellence RNM 1565 of Junta de Andalucı ́a.
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