An investigation on the graphitization of lowrank coal:Evolutional characteristics of aromatic structure
ZHANG Xiaomei,WANG Shaoqing,CHEN Hao,LI Xueqi,ZHANG Yixiu
石墨因其特殊属性及结构赋予的优越性能而被应用广泛。 煤炭是碳的富集物,在制备石墨 等碳材料方面颇具潜力。 以低变质程度且富惰质体的榆家梁煤(YJL5)为研究对象,对其进行高温 热处理,对不同温度下样品进行 X-射线衍射(XRD)测试及扫描电子显微镜(SEM)表征,以探讨在 热处理过程中的芳香结构演化规律及形貌特征,揭示低煤级富惰质体煤芳香结构向石墨结构演化 的轨迹及规律,并分析煤中灰分对芳香结构的影响。 结果表明,低煤级富惰质体煤 YJL5 制备石墨 的石墨化度>80%,可作为制备石墨的原材料煤种来源;YJL5 石墨化产物以棒状石墨为主,其由层 状薄膜组成。 微观形貌特征显示棒状石墨的生长模式与结构参数揭示的微晶结构尺寸的生长模式 一致。 随着石墨化温度升高,YJL5芳香层结构尺寸(La,Lc)增大,芳香结构横向拼接作用和纵向堆 砌作用同时发生。 室温~1 800 °C时,以碳化作用为主,非碳元素逐渐以挥发分形式排出,碳元素逐 渐富集,该阶段芳香结构增长以横向拼接作用为主。 温度高于 1 800 °C 时,层间距 d002 <0.344 0 nm,石 墨结构初步形成。 随着温度升高,芳香结构增长先以纵向堆砌作用为主(1 800~2 250 °C),然后以 横向拼接作用为主(2 250~2 850 °C)。 YJL5 中灰分对其石墨化具有一定的促进作用,但对芳香层 横向拼接和纵向堆砌影响效果不同。 1 800 ~ 2 850 °C ,未脱灰煤样的 La 大于脱灰煤样,可知 YJL5 中灰分对其芳香层横向增长具有持续显著的促进作用。 未脱灰煤样 Lc 仅在温度低于 2 250 °C 时大 于脱灰煤样,高于 2 250 °C 后比脱灰煤样的 Lc 更小,可知 YJL5 中灰分对芳香层纵向增长的促进作 用主要在 1 800~2 250 °C,高于 2 250 °C时无显著促进作用。
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 lowrank and inertiniterich 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 micromorphological 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 lowrank and inertiniterich coal. Results show that it is feasible to manufacture graphite from lowrank coal, and the graphitization degree of the YJL5 is >80%. Most of the hightemperaturetreated products are rodlike graphite. The rodlike graphite is composed of thin layered films. The growth and formation of rodlike 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 ℃, noncarbon 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 [JP2]demineralized 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 nondemineralized 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.
aromatic structure,graphitization,low rank coal,inertinite rich coal,high temperature treatment
主办单位:煤炭科学研究总院有限公司 中国煤炭学会学术期刊工作委员会