Explanation of the unusual peak of calorimetric heat in the adsorption of nitrogen, argon and methane on graphitized thermal carbon black.
Explanation of the unusual peak of calorimetric heat in the adsorption of nitrogen, argon and methane on graphitized thermal carbon black.
复制标题
石墨化热炭黑吸附氮气、氩气和甲烷时出现的量热热异常峰的解释。
DOI：
10.1039/b714478d
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发表时间：
2008
期刊：
影响因子：
--
通讯作者：
D. Nicholson
中科院分区：
文献类型：
--
作者：
A. Wongkoblap;D. Do;D. Nicholson
采用大正则蒙特卡罗模拟（GCMC）研究了完美石墨表面和缺陷石墨表面上氩、氮和甲烷的吸附热和吸附等温线。对于完美的表面，等量热量与负载的关系显示了简单流体在石墨上吸附的典型模式。根据吸附物、石墨化程度和温度，当第一层大部分被吸附物分子覆盖时，观察到热曲线与负载的峰值。在 77 K 处观察到氩气和氮气的热尖峰，而在 87.3 K 处的氩气则不再存在。这些模拟结果与J. Rouquerol, S. Partyka和F. Rouquerol, J. Chem的实验数据一致。法拉第传输学会。 1, 1977, 73, 306。就甲烷而言，我们在低温（84.5、92.5 和 104 K）下观察到热峰值。热峰值随着温度的变化而转变为更高的负载，然后在高温下消失。这些观察结果与 A. Inaba、Y. Koga 和 J. A. Morrison、J. Chem 的实验数据定性一致。法拉第传输学会。 2, 1986, 82, 1635。在观察到热尖峰的所有情况下，GCMC 模拟结果表明热尖峰与分子被挤压到已经致密的第一层以及分子重新排列以形成该层的高度结构化流体有关。当这种挤压发生在第一层时，分子继续吸附到相对稀疏的第二层上。
Heats of adsorption and adsorption isotherms of argon, nitrogen and methane on a perfect graphitic surface and a defective graphitic surface are studied with a Grand Canonical Monte Carlo Simulation (GCMC). For the perfect surface, the isosteric heat versus loading shows a typical pattern of adsorption of simple fluids on graphite. Depending on adsorbate, degree of graphitization and temperature, a spike in the heat curve versus loading is observed when the first layer is mostly covered with adsorbate molecules. The heat spike is observed for argon and nitrogen at 77 K while for argon at 87.3 K it is no longer present. These simulation results are consistent with the experimental data of J. Rouquerol, S. Partyka and F. Rouquerol, J. Chem. Soc., Faraday Trans. 1, 1977, 73, 306. In the case of methane we observe heat spikes at low temperatures, 84.5, 92.5 and 104 K. The heat spike shifts to higher loading with temperature and it then disappears at high temperatures. These observations are in qualitative agreement with the experimental data of A. Inaba, Y. Koga and J. A. Morrison, J. Chem. Soc., Faraday Trans. 2, 1986, 82, 1635. In all cases where heat spikes are observed, the GCMC simulation results indicate that the heat spike is associated with the squeezing of molecules into the already dense first layer, and the rearrangement of molecules to form a highly structured fluid of this layer. While this squeezing into the first layer is happening, molecules continue to adsorb onto the relatively sparse second layer.