CO₂ Adsorption on N-Doped Porous Biocarbon Synthesized from Biomass Corncobs in Simulated Flue Gas

Abstract

This study was to develop a low-cost N-doped porous biocarbon adsorbent that can directly adsorb CO2 in high-temperature flue gas from fossil fuel combustion. The porous biocarbon was prepared by nitrogen doping and nitrogen–oxygen codoping through K2CO3 activation. Results showed that these samples exhibited a high specific surface area of 1209–2307 m2/g with a pore volume of 0.492–0.868 cm3/g and a nitrogen content of 0.41–3.3 wt %. The optimized sample CNNK-1 exhibited a high adsorption capacity of 1.30 and 0.27 mmol/g in the simulated flue gas (14.4 vol % CO2 + 85.6 vol % N2) and a high CO2/N2 selectivity of 80 and 20 at 25 and 100 °C and 1 bar, respectively. Studies revealed that too many microporous pores could hinder CO2 diffusion and adsorption due to the decrease of CO2 partial pressure and thermodynamic driving force in the simulated flue gas. The CO2 adsorption of the samples was mainly chemical adsorption at 100 °C, which depended on the surface nitrogen functional groups. Nitrogen functional groups (pyridinic-N and primary and secondary amines) reacted chemically with CO2 to produce graphitic-N, pyrrolic-like structures, and carboxyl functional groups (−N–COOH). Nitrogen and oxygen codoping increased the amount of nitrogen doping content in the sample, but acidic oxygen functional groups (carboxyl groups, lactones, and phenols) were introduced, which weakened the acid–base interactions between the sample and CO2 molecules. It was demonstrated that SO2 and water vapor had inhibition effects on CO2 adsorption, while NO nearly has no effect on the complex flue gas. Cyclic regenerative adsorption showed that CNNK-1 possessed excellent regeneration and stabilization ability in complex flue gases, indicating that corncob-derived biocarbon had excellent CO2 adsorption in high-temperature flue gas.

CuCl2-Activated Sustainable Microporous Carbons with Tailorable Multiscale Pores for Effective CO2 Capture

“…The selectivity of MC-3 still reaches 42 at 1 bar and 273 K. Notably, MC-2 exhibits a higher CO 2 /N 2 selectivity at 298 K in the low-pressure region below 0.4 bar (Figure d), which results in a higher CO 2 uptake at 0.15 bar and 298 K. Such results further confirm the dominant contribution of ultramicropores on CO 2 capture at low pressure and high temperature. The CO 2 /N 2 IAST selectivity of MC-2 is 78 at 0.15 bar and 298 K and still keeps 48 at 1.0 bar and 298 K, which is comparable or even much higher than those of most of reported porous carbonaceous adsorbents. − Importantly, the CO 2 /N 2 selectivity of MC- x at 298 K has no decrease and even shows an increase, which significantly favors the practical application in capturing CO 2 from the flue gases.…”

Enhanced CO2 Adsorption Capacity in Highly Porous Carbon Materials Derived from Melamine-Formaldehyde Resin

“…It is important to note that the nitrogen content exhibited a slight decrease with the rising activation temperature owing to the unstable discharge of NO 2 and NO x gases from the carbon matrix. Previous research has highlighted that the incorporation of nitrogen groups into porous carbon can enhance CO 2 adsorption capabilities and CO 2 selectivity over N 2 , owing to improved acid–base, quadrupolar, and/or hydrogen bonding interactions. , From Table , the N content of these MFRC- T - m samples ranges from 6.43 to 18.34 wt %, which is much higher than those prepared from the post-treatment N-doping strategy. , …”