Experimental study on methane dissolved in surfactant-alkane system

Abstract

A surfactant-polyalkane system is investigated using chemical reagents to dissolve methane and control coal seam gas from low-energy, high-efficiency, safety, and environmental protection perspectives. At different temperatures and pressures, a high-temperature and high-pressure reactor, gas chromatograph, and other related experimental equipment were used to perform methane dissolution experiments, and a single surfactant sodium oleate (NaOA) and n-hexane demonstrated superior results. The single-factor experiments of temperature, pressure, and NaOA addition were performed and fitted via a response surface analysis. The optimal conditions for methane solubility were as follows: temperature of 34 °C, pressure of 4.5 MPa, NaOA addition of 85 g/L, and time of 1 h. The optimal effect of the surfactant-polyalkane system in dissolving methane was achieved with 32.31 mL/100 mL. Meanwhile, the change in the surface structure of coal before and after washing with the system was compared using scanning electron microscopy. The results indicated that the gas after washing with the surfactant-polyalkane system dissolved, and the surface pore structure of the coal changed. Moreover, the specific surface area and pore size of the coal surface increased after washing. Hence, the desorption of gas from the coal surface into the system becomes easy, thereby reducing the gas content in the coal sample.