In order to investigate the influence of support structure properties on CO capture performances of solid amine adsorbents, a novel three-dimensional disordered porous silica (3dd) with hierarchical pore networks was developed and then compared to other three materials as adsorbent support, namely, hierarchical porous silica (HPS), MCM-41, and SBA-15. They were all functionalized with tetraethylenepentaamine (TEPA) to prepare CO adsorbents. The adsorbents' ability to capture CO was examined on a fixed-bed reactor. When these supports had 60 wt% TEPA loading, the amounts of CO captured followed the order 3dd > HPS > SBA-15 > MCM-41 at 75 °C; the adsorption capacities were 5.09, 4.9, 4.58, and 2.49 mmol/g, respectively. The results indicate that a larger pore volume can promote the dispersion of amine species to expose more active sites for CO capture. The larger pore size can decrease the CO diffusion resistance. High surface area is not an important factor in determining capture performance. In addition, compared with conventional single-size mesopores, the hierarchical pore networks can disperse the TEPA species in different levels of the channel to limit undesired loss/aggregation of impregnated TEPA species. Thus, the 3dd support exhibits the best stability and highest regeneration conversion compared to the other three supports. This work demonstrates that the rational design of adsorbent support systems can effectively relieve the trade-off between amine loading and diffusion resistance. One method to surmount this trade-off is to utilize an adsorbent platform with hierarchical pore networks. Thus, this work may provide a feasible strategy for the design of CO solid amine adsorbents with high capture amount and amine utilization efficiency.

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Summary Porous carbon materials have been widely used for CO2 adsorption, but their preparation was subject to conditions such as raw material cost, activator corrosion, and temperature. In this study, nitrogen‐doped porous carbonaceous adsorbents were prepared in a low temperature region (400‐550°C) by one‐step composite nitrogen doping method, using low‐cost oil residue as raw materials and less corrosive NaNH2 as activator. The CO2 adsorption performances of the prepared N‐doped porous adsorbents were systematically explored. The results showed that optimal oil residue‐derived carbonaceous adsorbent owned excellent amount of CO2 adsorption up to 3.51 and 5.63 mmol/g at 298 and 273 K under 1 bar, respectively. It was discovered that the congenerous influences of porous structure, nitrogen content and Vn of the adsorbent affected their CO2 adsorption performances under 1 bar. Importantly, these oil residue porous carbonaceous adsorbent also was verified owning fine selectivity of the CO2 over N2 (15.7), which attributed to its high Vn and nitrogen content. Furthermore, optimal sample OAC‐500‐2.5 owned medium Qst (21‐26 kJ/mol), which was beneficial practical application. This work may inspire new sparks on novel nitrogen‐doped adsorbent with inexpensive precursor, low activation temperature and simple preparative tactic, indicating that the nitrogen‐doped sample is promising in the practical situation of CO2 adsorption.

A novel mesocellular silica foam (MCF) support were synthesized, which has different pore volumes and two different sizes of windows on the spherical cells. Tetraethylenepentamine (TEPA)-functionalized MCF adsorbents were then prepared for CO2 capture. The effects of support structure, capture temperature, SO2, and NO2 on the CO2 capture were investigated. The results show that the hierarchical window structure can improve the dispersion of amine species in the silica foams. In situ diffuse reflectance infrared Fourier transform spectroscopy results indicate that more adsorption sites can be exposed in the pores at high temperature for CO2 capture. The MCF-TEPA60% has the optimal capture amount of 4.75 mmol/g with 15 vol % CO2 at 75 °C. The SO2 and NO2 have a negative influence on the adsorption and regeneration properties of adsorbent due to the production of byproducts. However, the MCF-0.8-TEPA60% can maintain outstanding carbon dioxide adsorption capacity during 10 regeneration cycles.