煤层气吸附/解吸分馏的从头计算研究  

CARBON ISOTOPE FRACTIONATION DURING COALBED METHANE ADSORPTION/DESORPTION: AN AB INITIO STUDY

作　　者：陈润[1] 苏现波[1] 刘国伟[1] 

机构地区：[1]河南理工大学资源环境学院,河南焦作硕士生454003

出　　处：《煤炭转化》2007年第2期57-60,共4页Coal Conversion

基　　金：国家自然科学基金资助项目(50534070);国家"973"计划项目(2002CB211705);河南省自然科学基金资助项目(0611023500)

摘　　要：根据13CH4与12CH4在煤表面吸附势能的差异性合理解释煤层气吸附/解吸过程中的碳同位素分馏效应,为煤层气运移聚集过程的预测提供了有效途径.根据已建立的甲烷在煤表面的吸附模型,采用量子化学从头计算的方法计算煤表面甲烷吸附势能,绘制煤吸附甲烷的势能曲线,发现13CH4在煤表面的吸附势能普遍高于12CH4,也就是说13CH4与12CH4相比具有优先吸附、滞后解吸的特点.这一研究结果与Polanyi吸附势理论的研究结果一致.从而合理解释了煤层气解吸过程中发现的先解吸δ12C甲烷、后解吸δ13C甲烷的现象,也解释了煤层甲烷碳同位素深部重、浅部轻的地质现象;同时计算结果还表明,甲烷在煤表面是以单分子层吸附的.The carbon isotopic fractionation effect during the process of adsorption/desorption can be explained by the adsorption potential energies difference of ^13 CH4 and ^12 CH4 on coal. It offers an effective way for forecast the movement and accumulation of coalbed gas. Based on the model of methane adsorption on coal, the methane potential energy on coal is calculated with an ab initio, and then the adsorption potential energy carve is drown. The curve suggests that the adsorption potential energy of ^13 CH4 on coal is higher than that of ^12 CH4. This implies that the coal is preference for ^13CH4 adsorption and postponement for ^13CH4 desorption. The conclusion is the same with the conclusion of fractionation between ^13CH4 and ^12CH4 on coal by Polanyi adsorption potential. It explains why the ^12CH4 is firstly released and ^13CH4 is postponement from coal during the process of methane desorption and why the light δ^13C of coalbed methane is distributed in the shallow part of basin and the heavy in the deep part of the basin. Simultaneity, The result indicates that methane adsorption on coal is single molecule layer adsorption. These are approved by an amount of adsorption/desorption experiments.

关 键 词：煤层气 吸附/解吸 甲烷碳同位素分馏效应 从头计算 

分 类 号：O647.3[理学—物理化学]