Synthesis of nitrogen enriched porous carbons from urea formaldehyde resin and their carbon dioxide adsorption capacity

- Synthesis of N-enriched carbon adsorbents from UF resin and mesoporous silica.
- CO2 uptake capacity of 1.26 mmol g−1 was obtained for sample UFZ-700 at 30 °C.
- CO2 capture was found to be depending on surface functional group.
- CO2 adsorption kinetics on material follow fractional order kinetic model.
- Adsorbents exhibits complete regenerability over four adsorption/desorption cycles.

Carbon dioxide capture needs development of cost effective CO2 capture technologies. This paper describes nitrogen enriched porous carbons synthesized from nanocasting technique using mesoporous silica as template and urea-formaldehyde resin as precursor. These carbon materials were evaluated as sorbents for CO2 capture by using a thermogravimetric analysis under dynamic conditions. Carbonization and physical activation with CO2 at different temperatures (500-800 °C) were carried out that resulted in the generation of different carbon adsorbents containing nitrogen functional groups. The textural characterization result reveals effect of nanocasting technique, which is confirmed from the generation of mesopores (0.644 cm3 g−1), micropores (0.123 cm3 g−1) and high surface area (337.07 m2 g−1) of adsorbent. The CO2 capture capacity depends more on the nitrogen functionalities in addition to textural properties and nitrogen content, as the sample synthesized at 700 °C shows highest uptake capacity of 1.3 mmol g−1. Furthermore, it was found that adsorbent can be easily regenerated, which was also seen by the lower value of isosteric heat of adsorption. Ten adsorption-desorption cycles show established materials' excellent stability as an adsorbent. Different kinetic models were fitted for the adsorption data and on the basis of correlation coefficient (R2), fractional order provided best fit with the experimental data. The heterogeneous nature of the adsorbent surface was seen by best fitting of Freundlich isotherm and from the pattern of isosteric heat of adsorption. Exothermic, spontaneous and feasible nature was suggested by thermodynamic parameters' values. The thermal energy needed for desorption of CO2 from the adsorbent surface was around 1.28 MJ per kg CO2.

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