Title: Evolutions of nanoscale pore and chemical structures of tectonically deformed coals after supercritical CO₂ treatment

Authors: Linlin Wang; Bo Jiang; Run Chen; Yunbo Li

Addresses: Low Carbon Energy Institute, Key Laboratory of Coal-based CO₂ Capture and Geological Storage, Jiangsu Province, China University of Mining and Technology, 1 Jinshan East Road, Xuzhou, 221008, China; Key Laboratory of Tectonics and Petroleum Resources, Ministry of Education, China University of Geosciences, Wuhan, 430074, China ' Ministry of Education Key Laboratory of CBM Resources and Reservoir Formation Process, School of Resources and Geosciences, China University of Mining and Technology, 1 Daxue Road, Xuzhou, 221116, China ' Low Carbon Energy Institute, Key Laboratory of Coal-based CO₂ Capture and Geological Storage, Jiangsu Province, China University of Mining and Technology, 1 Jinshan East Road, Xuzhou, 221008, China ' College of Resources and Environment, Henan Polytechnic University, Jiaozuo, 454000, China

Abstract: Supercritical CO₂ treatments were carried out for four coal samples with different deformation degrees at around 35°C and 10 MPa for 5 h. Nanoscale pore and chemical structures of coals before and after treatments were studied via liquid nitrogen adsorption and X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR) tests. The results showed that coal deformation induced more spaces and contact areas, and thus supercritical CO₂ treatment presents improved effects on pore volume and specific surface area with increasing coal deformation degree. Moreover, supercritical CO₂ treatment mainly induced increased pore volumes of pore types I (< 10 nm) and II (10-50 nm) and specific surface area of pore type I. In addition, supercritical CO₂ treatment exerts substantial effects on chemical structures, including increased aromatic layer spacing, decreased the aliphatic compound or ethers, alcohols, and lipids, which is also related to coal deformation degrees. The experiments revealed that treated tectonically deformed coals present greater growths in gas adsorption and diffusion spaces and more obvious changes in chemical structure than the undeformed coal, which can improve CO₂ storage and seepage. [Received: June 2, 2017; Accepted: February 10, 2018]

Keywords: nanoscale pore; chemical structure; tectonically deformed coal; supercritical CO₂ treatment.

DOI: 10.1504/IJOGCT.2018.095992

International Journal of Oil, Gas and Coal Technology, 2018 Vol.19 No.4, pp.477 - 500

Received: 02 Jun 2017
Accepted: 10 Feb 2018
Published online: 06 Nov 2018 *

Full-text access for editors Full-text access for subscribers Purchase this article Comment on this article