An investigation on the graphitization of lowrank coal:Evolutional characteristics of aromatic structure

Specific properties and structures of graphite contribute to its advantageous performance, which makes graphite to be widely applied in various fields. Coal is the carrier of carbon enrichment, so it is potential for coal to manufacture carbon materials, such as graphite. A lowrank and inertiniterich coal (YJL5) from YJL mine is selected as an object and a high temperature treatment (HTT) is conducted. A X-ray diffraction (XRD) is used to reveal aromatic structural evolution and the effects of minerals. A scanning electron microscope (SEM) is applied to reveal the micromorphological features of samples at different temperatures. The effects of minerals in the YJL5 on the aromatic structural evolution are also discussed. It will provide alternative and fundamental for preparing carbon materials, including graphite. It will be useful information for synthetic graphite from lowrank and inertiniterich coal. Results show that it is feasible to manufacture graphite from lowrank coal, and the graphitization degree of the YJL5 is ＞80%. Most of the hightemperaturetreated products are rodlike graphite. The rodlike graphite is composed of thin layered films. The growth and formation of rodlike graphite are corresponding with the growth of crystalline revealed by XRD. With increasing temperature, the sizes of crystalline width and height (L a, L c) enlarge, the horizontal enlargement of crystalline width and vertical stacking of crystalline height develop simultaneously. The carbonization develops mainly from ambient to 1 800 ℃, noncarbon elements are diminished in the forms of volatiles, while carbon is enriched gradually. During this stage, the horizontal enlargement of crystalline width is prevailing. When the temperature is ＞1 800 ℃, the d 002 value begins to ＜0.344 0 nm, and graphitic structure is preliminarily formed. With increasing temperature, the prevailing enlargement of crystalline height （1 800-2 250 ℃）gradually turns into prevailing enlargement of crystalline width（2 250-2 850 ℃）. Minerals in the YJL5 show a positive effects on its graphitization, but differences exist between growth in horizontal width and vertical height of crystalline. Samples without demineralization show larger La values than that of JP2demineralized samples from 1 800-2 850 ℃, the minerals in the YJL5 have positive effect on the enlargement of aromatic structural width. Samples without demineralization show larger Lc values than that of demineralized samples from 1 800-2 250 ℃, and the Lc values of nondemineralized samples are even smaller than that of demineralized samples when ＞2 250 ℃. Minerals in YJL5 show a positive effect on the stacking of aromatic structural height from 1 800-2 250 ℃. When temperature ＞2 250 ℃, no obvious positive effect is observed.