Improvement of gas hydrate-based CO2 capture from CH4/CO2 mixture using silica and modified silica nanoparticles in the presence of potassium hydroxide

Abstract

Separation of CO2 gas from CO2/CH4 mixture (74 mol% of CH4 and 26 mol% of CO2) was investigated, experimentally using the gas hydrate formation method in a constant-volume vessel. Silica and (3-aminopropyl) teriethoxysilane (APTES) surface-modified silica nanoparticles in the presence of potassium hydroxide were employed as additives. The impacts of various parameters such as initial pressure, gas–liquid ratio, and nanoparticle concentration were studied on gas consumption, separation factor, and recovery factor of CO2 gas in the separation process. Experiments were performed at 277.15 K and two initial pressures of 3.0 and 4.0 MPa. The presence of silica had a positive effect on gas consumption, separation, and recovery factors. The optimum results are obtained for the nanofluids including silica and potassium hydroxide, which at best case improved the gas consumption, separation factor, and recovery factor by 36 %, 29 % and 38 % compared to the pure water, respectively. The optimum nanoparticle concentration was obtained to be 0.1 wt% Besides, as the gas–liquid ratio increased, the gas consumption value raised. However, the relative amount of gas consumption and the recovery factor decreased. While the gas consumption was a direct function of the initial pressure, the separation and recovery factors were inverse functions of that.