Enlargement of the micropores of a caking bituminous coal by controlled oxidation

Abstract

In a study of the enlargement of pores of coals it has been found that treatment of a bituminous coal (PSOC No. 371, from the Pennsylvania State University Coal Section) with a 5:95 O 2:N 2 stream 4 h at 400 °C increases the surface area as measured by nitrogen adsorption at 77K by a factor of at least 50 to a value 52 m 2 g −1. The increase in pore size was accompanied by a 9.7% weight loss. Simultaneously, the area as measured by carbon dioxide at 195K increased from 61 to 136 m 2 g −1 and that measured by carbon dioxide at room temperature increased from 125 to 237 m 2 g −1. Attempts to enlarge the pores by oxidation with hydrogen peroxide or ozone were unsuccessful. A Pittsburgh coal subject to a small percentage of oxygen in nitrogen or steam at 300 to 400 °C showed a surface area as measured by nitrogen adsorption of less than 1 m 2 g −1 both before and after such pretreatment. This same coal with a 5:95 O 2:N 2 stream for 4 h at 450 °C showed a surface area of 110 m 2 g −1 measured by nitrogen adsorption at 77K.