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Synergistic Enhancement of CO2 Adsorption Capacity and Kinetics in Triethylenetetrammonium Nitrate Protic Ionic Liquid Functionalized SBA-15

Zhang, Wei; Gao, Erhao; Li, Yu; Bernards, Matthew T.; Li, Younan; Cao, Guanghan; He, Yi; Shi, Yao

Energy & Fuels, 2019, vol 33, 9, pp. 8967-8975

DOI:10.1021/acs.energyfuels.9b01872

Abstract

A series of triethylenetetrammonium nitrate protic ionic liquid (TNPIL) functionalized, highly ordered mesoporous SBA-15 molecular sieves with different loadings have been synthesized via impregnation. The CO2 capture performance of the hybrid sorbents was evaluated under conditions mimicking a combustion flue gas (15% CO2) over the temperature range of 298–348 K. The breakthrough experiments revealed that the sieves with 66% mass loadings of TNPIL (S15-66TNPIL) exhibited the highest CO2 adsorption capacity of 2.12 mmol g–1 at 333 K, representing a dramatic enhancement compared to the bare support (883%). The intraparticle diffusion model analysis of the hybrid sorbents demonstrated that S15-66TNPIL had the fastest CO2 uptake rate of 131 × 10–3 mmol g–1 s–0.5 in the rate-controlling stage. This was almost 5 times higher than that of the bare support alone and is a significant improvement over other IL-functionalized and amine-modified support systems. This can be attributed to the synergistic effects of the high affinity between the TNPIL and CO2 and the fast diffusion rate from the distribution of TNPIL across the support with a large surface area. In addition, S15-66TNPIL exhibited a great regeneration capacity. The Fourier transform-infrared spectroscopy analysis coupled with isosteric heat and density functional theory simulations revealed that the adsorption state is dominated by chemisorption, and the CO2 preferentially interacts with the primary amine ?N(3)H2 to form carbamate based on the high binding energy. Therefore, this novel TNPIL-supported system represents a promising candidate for CO2 capture and recovery applications.

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