Characterization of the surface properties of Illinois basin coals. Final technical report, September 1, 1991--August 31, 1992

Abstract

Surface area and pore volume distributions, surface charge, and surface chemical structure of the eight coals in the Illinois Basin Coal Sample Program (IBCSP) were determined. The IBC-101 coal has the lowest total and micropore (3.5-20.0 {Angstrom}) surface areas. The IBC-103 coal has the lowest mesopore (20-500 {Angstrom}) surface area. The mesopore surface areas of IBC-101, IBC-102, and IBC-107 coals are higher than the other four coals. Pore volume in pores <1800 {Angstrom} in diameter varies almost five-fold with IBC-103 coal having the lowest value. These differences may affect the reactivity of these coals during cleaning, conversion, and combustion processes. Surface charge and isoelectric points vary among the samples. The isoelectric point, where processes such as agglomeration and dewatering is most efficient, shifted to higher pH values for some of the samples upon exposure to air oxidation at room temperature. Diffuse reflectance infrared spectroscopy (DRIS) data indicate that the surfaces of the IBCSP coals contain aromatic hydrocarbon components, aliphatic hydrocarbons, and an aldehyde group. Ball-mill grinding reduced the organic hydroxyls and thus enriched relative concentrations of nonpolar aliphatic functional groups in the samples. The room temperature air oxidation did not cause any significant change on the surface chemical structure ofmore » the coals.« less