Highly Cost-Effective Nitrogen-Doped Porous Coconut Shell-Based CO₂ Sorbent Synthesized by Combining Ammoxidation with KOH Activation

The objective of this research is to develop a cost-effective carbonaceous CO₂ sorbent. Highly nanoporous N-doped carbons were synthesized with coconut shell by combining ammoxidation with KOH activation. The resultant carbons have characteristics of highly developed porosities and large nitrogen loadings. The prepared carbons exhibit high CO₂ adsorption capacities of 3.44–4.26 and 4.77–6.52 mmol/g at 25 and 0 °C under atmospheric pressure, respectively. Specifically, the sample NC-650-1 prepared under very mild conditions (650 °C and KOH/precursor ratio of 1) shows the CO₂ uptake 4.26 mmol/g at 25 °C, which is among the best of the known nitrogen-doped porous carbons. The high CO₂ capture capacity of the sorbent can be attributed to its high microporosity and nitrogen content. In addition, the CO₂/N₂ selectivity of the sorbent is as high as 29, higher than that of many reported CO₂ sorbents. Finally, this N-doped carbon exhibits CO₂ heats of adsorption as high as 42 kJ/mol. The multiple advantages of these cost-effective coconut shell-based carbons demonstrate that they are excellent candidates for CO₂ capture

Role of Hydrogen Peroxide Preoxidizing on CO₂ Adsorption of Nitrogen-Doped Carbons Produced from Coconut Shell

In this work, the coconut shell was preoxidized by hydrogen peroxide, before it was treated by the ammoxidation process and potassium hydroxide activation to synthesize nitrogen-doped porous carbons. The resulting sorbents exhibit significantly higher nitrogen content and narrow microporosity than the control sample without H₂O₂ pretreatment. Consequently, these sorbents are found to demonstrate high carbon dioxide uptake at 1 bar, such as 4.47 mmol g^–1 at 25 °C and 6.79 mmol g^–1 at 0 °C. In addition, these sorbents possess high CO₂/N₂ selectivity, stable reusability, high initial heat of CO₂ adsorption, and high dynamic CO₂ capture capacity under simulated flue gas conditions. These superior CO₂ adsorption properties make them highly competitive among all the carbonaceous adsorbents for CO₂ capture

Tetraethylenepentamine-Modified Silica Nanotubes for Low-Temperature CO₂ Capture

The objective of this research is to develop a new type of CO₂ sorbent. The sorbents were synthesized with mesoporous ethane–silica nanotubes (E–SNTs) and tetraethylenepentamine (TEPA). They were characterized by nitrogen adsorption/desorption, thermogravimetric analysis, and infrared spectroscopy. A fixed-bed reactor equipped with an online mass spectrometer was used to test the CO₂ capture performances of the sorbents. It was found that 75 °C is the optimal CO₂ adsorption temperature for amine-impregnated E–SNT sorbents. The highest CO₂ sorption capacities achieved with E–SNTs with 50 wt % TEPA loading (E–SNTs–50%) without and with uses of water vapor are 3.58 and 4.74 mmol/g, respectively, under the conditions of a 10.0% CO₂/N₂ mixture at 75 °C. Cyclic CO₂ adsorption–desorption test results indicate that the new composite sorbents are stable and regenerable