[Bmim][Bf4] and nitric acid synergistic effect on microstructure of coal

Abstract

In order to study the synergistic effect of imidazole based ionic liquids in nitric acid, the coal samples were firstly treated with nitric acid(HNO3) solution, 1-butyl-3-methylimidazoletetrafluoroborate([Bmim][BF4]) solution and its mixed solution respectively. Then the wettability of each solution was tested by contact angle experiment. Finally, the pore-crack damage of coal samples after each solution treatment was observed by scanning electron microscope experiment. The results found that single solution and composite solution have a great influence on the wettability and pore structure of coal samples, and the synergistic effect of composite solution increases the oxygen-containing functional groups in coal and makes the aromatic structure of coal samples more compact. This result is the same as the experimental result of contact angle, and the contact angle of coal dust in composite solution is the smallest. In addition, through the observation of coal sample surface by scanning electron microscope, it is found that the seepage network channel of coal sample under the synergistic effect is more developed than that of coal sample treated with single solution. In the engineering practice of Yuwu Coal Mine, the gas volume fraction of the borehole is increased by more than 20%, the gas flow rate increased by more than one times.

Keywords

• microstructure of coal
• synergistic effect
• condensation reaction
• contact angle
• seepage channel