Quantum Chemical Study on the Influence of Dodecyl Trimethyl Ammonium Bromide on the CH4 Adsorption of Coal

Abstract

The adsorption of dodecyl trimethyl ammonium bromide (DTAB) on coal can affect the wettability of coal and change the water absorption of coal. After DTAB treatment, the change in the CH4 adsorption capacity of coal is worth further study. To reveal the microscopic mechanism of the influence of DTAB on the CH4 adsorption capacity of coal, we employed the density functional theory (DFT) with the 6-311 G (d, p) basis set. DFT-based computations interpreted the adsorption process of CH4 and DTAB on coal molecules and determined the stable structure, adsorption distance, Mulliken overlapping populations, and adsorption energies of the two adsorption configurations. The results showed that the adsorption energies of CH4 and DTAB on the molecular model of coal were 2.15 and 42.69 kJ/mol and the adsorption stability distances were 0.261 and 0.238 nm, respectively. The DTAB–coal configuration was more stable than the CH4–coal configuration. When there was competitive adsorption between DTAB and CH4 on coal, the coal molecules preferentially adsorb the DTAB. Infrared spectroscopy and adsorption experiments were also carried out, and the calculation results of quantum chemistry are consistent with the experimental results.

Pore structure characteristics of deep coal seams under the synergistic effect of high temperature and high pressure and their impact on coalbed methane adsorption

“…Guanwen Lu studied adsorption models for different coal types and found that the most applicable models for raw coal, fission coal and flake coal were the Toth, L-F and D-A models (Lu et al, 2020). Through the study of the adsorption model, Liu Shuo found that the DA model can describe the adsorption features of coal well (Liu et al, 2020). As mentioned above, scholars have mainly focused on the consideration of single factors such as temperature or pressure, with little consideration given to the effect of pore structure.…”