Alkali carbonates promote CO capture by sodium orthosilicate

• Published in: Physical chemistry chemical physics : PCCP Vol. 21; no. 24; pp. 13135 - 13143
• Main Authors: Liu, Jia, Wang, Zhen, Wang, Zirui, Song, Jinwan, Li, Guangshi, Xu, Qian, You, Jinglin, Cheng, Hongwei, Lu, Xionggang
• Format: Journal Article
• Published: 19.06.2019
• ISSN: 1463-9076; 1463-9084
• DOI: 10.1039/c9cp01306g

Sodium orthosilicate was synthesized by a wet chemical method with further calcination at 600 °C. Mixtures of Na 4 SiO 4 and alkali (Li/Na/K) carbonates were prepared by a mechanical mixing method. The CO 2 capture performance of the samples was characterized by dynamic thermogravimetric analyses and in situ XRD and Raman spectroscopy in 80 vol% CO 2 mixed with 20 vol% N 2 . It was found that sodium orthosilicate could be used for CO 2 sorption, and its maximum capacity could reach up to 19.2 wt%. The addition of alkali carbonates, which serve as promoters, led to the enhancement of the CO 2 capture performance of Na 4 SiO 4 , especially at low temperatures, because of the formation of C 2 O 5 2− . The existence of C 2 O 5 2− in the mixture exposed to 80 vol% CO 2 was confirmed by in situ Raman spectra, and its geometric structure was presented by DFT calculations. The formation of C 2 O 5 2− within carbonates exhibited a positive influence on the CO 2 capture at low temperatures and the enhancement of CO 2 diffusion by Grotthuss-like transport through the carbonate product shell at high temperatures besides the formation of eutectic carbonate melts. The C 2 O 5 2− combined with alkali cations are the intermediates during the CO 2 uptake with Na 4 SiO 4 and alkali carbonates.