Article Cite This: Energy Fuels 2019, 33, 5398−5407
pubs.acs.org/EF
Pore Structure Modified CaO-Based Sorbents with Different Sized Templates for CO2 Capture Siyu Wei, Rui Han, Yanlin Su, Jihui Gao,* Guangbo Zhao, and Yukun Qin School of Energy Science and Engineering, Harbin Institute of Technology, Harbin 150001, China
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S Supporting Information *
ABSTRACT: Porous structure is critical for CO2 capture performance of CaO-based sorbents in Ca-looping. The sacrificial template method is an easy and effective way to alter the texture structure of sorbent pellets. To explore the optimal pore size distribution for CO2 sorption, two micron templates, starch and cotton fiber, and two nano templates, carbon nanotubes and carbon nanofibers, were used to modify the pore structure on different scales for the first time. The CO2 capture capacity of CaCNT in the 15th carbonation under severe calcination conditions was 86% more than that of the sorbent without templates. The enhanced CO2 capture performance was attributed to the uniform small mesopores (2−10 nm) produced by nanosized templates. In this case, a large specific surface area is provided for carbonation. Micron templates would produce additional pores ranging from 10 to 100 nm and even large pores (>400 nm). The analysis results suggest that the pore volume (ranging from 2 to 10 nm) would have the linear relationship with CO2 uptake at the reaction control stage; the pore volume of 10−100 nm was positively correlated with the CO2 uptake at the diffusion control stage, and pores larger than 100 nm were ineffective in promoting CO2 capture. Wu et al.21 found that the small particle size of CaO was beneficial to superior CO2 uptake performance. The critical product layer thickness is 50 nm in the carbonation of CaO.22 Theoretically, the CaO sorbent can thus reach 100% conversion at the rapid reaction control stage with the particle size of
