Energy & Fuels, Vol.17, No.5, 1244-1250, 2003
Quantitative analysis of hydrogen in carbonaceous materials: Hydrogen in anthracite
The accurate determination of elemental composition is the first step to elucidate the chemical structure of carbonaceous materials. However, it is generally not easy to obtain reliable data for hydrogen content, especially in hydrogen-lean materials. We attempt to establish a reliable method to determine not only the total hydrogen content, but also the distribution mode of hydrogen in various moieties in carbonaceous materials. As the first example, the hydrogen distribution in Chinese anthracites is determined in this study. In the temperature-programmed oxidation, H2O evolved in two temperature ranges from 50 to 500 degreesC and from 500 to 800 degreesC. The H2O evolution in the low-temperature region was assigned to the desorption of adsorbed water. The dehydration of mineral matter was seen in the high-temperature region, but the quantity was very small. The majority of H2O evolution in the high-temperature region was the result of the oxidation of the polyaromatic hydrocarbon moiety in anthracite. Oxidation of anthracite accompanied CO and CO2 evolution. The H/C atomic ratio of organic moiety in the sample can thus be known from the amount of evolved H2O, CO, and CO2. The ratio obtained for the demineralized samples are 0.08, 0.13, and 0.18 for SWZ, MTG, and GEZ anthracite, respectively. This ratio is directly related to the chemical structure of anthracite, and the above result indicates quite different nature of three anthracites. The hydrogen content determined by the ultimate analysis includes not only organic hydrogen but also hydrogen in adsorbed water and mineral matter, and therefore the H/C ratios calculated from the ultimate analysis data are quite different from the above values. The ratios are 0.15, 0.15, and 0.16 for respective anthracites. There is almost no difference among the three anthracites.