Pore Structure Characterization of Coal by Synchrotron Small-Angle X-ray Scattering and Transmission Electron Microscopy

Abstract

Coal is a porous medium with complex pore structures. The characteristics of the pore structure play an important role in various aspects of coal use, including extraction of methane from coal seams, CO 2 sequestration in coal, and water purification by activated carbon. To describe comprehensively the pore structure of coal, we apply transmission electron microscopy (TEM) and synchrotron small-angle X-ray scattering (SAXS) measurements to six coal samples from medium to high rank. The positive deviation of SAXS data from Porod's law was observed. The positive deviation correction of SAXS data was carried out to quantitatively obtain the pore size distribution and specific surface area. We find that the pore size distribution is independent of the coal rank but varies with the vitrinite content; pores in vitrinite-rich coals are smaller than those in vitrinitepoor coals for the same rank. Channel-like and interconnected pores are observed for both high-and low-volatile bituminous coals. Among all coal samples, the low-volatile bituminous coal has the largest specific internal surface area, indicating the highest gas storage capacity and a favorable role as the best candidate for coalbed methane exploration and coal CO 2 sequestration.

Pore structure characterization of different rank coals using gas adsorption and scanning electron microscopy

“…In this paper, the IUPAC pore standard is adopted. In order to characterize the pore size distribution (PSD) and total porosity of porous media, numerous methodologies have been developed, including gas adsorption [13,14], high-pressure mercury intrusion (MICP) [15,16], synchrotron small-angle X-ray scattering (SAXS) [17,18], small-angle neutron scattering (SANS) [19,20], nuclear magnetic resonance (NMR) [11,21,22], atomic force microscope [23][24][25], microfocus X-ray computed tomography [26], SEM [27], transmission electron microscopy (TEM) [17,28]. Among these methodologies, LP-N 2 GA analysis has been verified to be an effective method to characterize the pore structure of porous medium [29][30][31].…”

Multi scale characterization of coal structure for mass transport

“…Several studies have been presented in the literature on estimating coal microstructure properties and coal microstructure visualization [12][13][14]11,[15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33]. Small angle X-ray scattering has been used to estimate pore size distribution, porosity and interface area of coal [17,24,31].…”

“…Small angle X-ray scattering has been used to estimate pore size distribution, porosity and interface area of coal [17,24,31]. This technique even though informative, does not give complete details about the internal structure of coal.…”

The effect of adsorption-induced swelling on porosity based on the transient coal swelling model

“…Coal is a combustible mineral formed by ancient plants buried underground under complex biochemical, physical, and chemical changes gradually. 1 Coal seam is the reservoir for methane extraction and greenhouse gases sequestration. 2 The coal pore structure is the basis for the study of coalbed methane storage, desorption, diffusion and seepage.…”