TBAB-CO<sub>2</sub>水合物形成过程的微观实验

doi:10.3964/j.issn.1000-0593(2019)09-2889-05

Abstract
References
Related Citation (15)

Download: PDF (2791 KB)
Export: BibTeX | EndNote (RIS)

Abstract TBAB semi-clathrate hydrate has a huge potential for effective application of carbon dioxide (CO₂) capture. Because of the complexity of the crystal structure, the kinetics of TBAB hydrate remains poorly understood. In this work, the spectral characteristics of nCO₂·TBAB·26H₂O and nCO₂·TBAB·38H₂O were analyzed by Raman and powder X-ray diffraction (PXRD). To understand the gas storage characteristics of TBAB hydrate, the processes of CO₂ molecules entering 2 kinds of crystal structures were measured using in situ Raman spectroscopy. Results showed that the Raman spectra of 2 crystal structures had high similarity. The Raman peaks at 1 309.5 and 1 326.9 cm^-1 were assigned to be the C—C deformation vibration mode of TBA⁺ cations in nCO₂·TBAB·26H₂O hydrate. They did not shift in nCO₂·TBAB·38H₂O hydrate, but became detached and narrow in half-peak width. Meanwhile, the peaks at 1 446.6 and 1 458 cm^-1 were assigned to be the C—H shear vibration mode of TBA⁺ cations in nCO₂·TBAB·26H₂O hydrate. They shifted away from each other and had lower less overlap region in nCO₂·TBAB·38H₂O hydrate. Those features in Raman spectra were helpful to distinguish the 2 kinds of structures. The PXRD patterns of the 2 TBAB hydrates showed large difference from each other. nCO₂·TBAB·26H₂O hydrate was tetragonal which had the space group of (P4/m), while nCO₂·TBAB·38H₂O hydrate was orthorhombic which had the space group of (Pmma). In the PXRD patterns, the peaks at 2θ=8.406° and 10.941° were (200) and (220) planes of nCO₂·TBAB·38H₂O hydrate respectively. The structure of nCO₂·TBAB·26H₂O hydrate was characterized by the (012) and (003) planes at 2θ=5.976° and 6.969° respectively. During the in situ Raman measurements, nCO₂·TBAB·26H₂O and nCO₂·TBAB·38H₂O hydrates grew directly from the prepared TBAB·26H₂O and TBAB·38H₂O hydrates at 276 K, 2 MPa. The CO₂ molecules were captured by the 5¹² hydrate cages in the 2 kinds of hydrates, formed the characteristic peaks of CO₂ at 1 275.4 and 1 379.3 cm^-1 and increased continuously. The Raman peaks at 1 110.3 cm^-1 were chosen as reference peak to compare the CO₂ concentration growth in the 2 kinds of hydrates. In the initial 75 minutes of in situ Raman measurements, the content of CO₂ in hydrate phase grew linearly with generally the same growth rates in 2 kinds of crystals. As the measuring spots were on the hydrate surface where the gas diffusion resistance in hydrate phase could be neglected and the cage structures used for gas storage were all 5¹² cage, the similar gas storage rates were obtained. The microcosmic experimental study provides a theoretical basis for CO₂ capture technology by forming TBAB semi-clathrate hydrate.

Key words：Natural gas hydrate; Kinetics; Carbon dioxide; Raman; X-ray diffraction

Received: 2018-07-27 Accepted: 2018-12-19

ZTFLH:

O657.3

Corresponding Authors: LIANG De-qing E-mail: liangdq@ms.giec.ac.cn

Cite this article:

URL:

https://www.gpxygpfx.com/EN/10.3964/j.issn.1000-0593(2019)09-2889-05 OR https://www.gpxygpfx.com/EN/Y2019/V39/I09/2889