The formation of gas hydrates is known as one of the main problems in natural gas traortation pipelines in the industry. The subject of main researches in this area relates to the equilibrium conditions of gas hydrate formation and the effect of inhibitors on the P-T curve of gas hydrate. However, in recent years, the positive features of hydrate for storing and traorting of gases as well as separating the mixture of gases have been considered in the scientific researches. Regarding to the difference of thermodynamic conditions of hydrate formation for various gases, the gas mixtures can be separated by providing the conditions for the formation of hydrate of one of the components of a gas mixture. In this study, the separation of CO 2 from the mixture of CO 2 and CH 4 is investigated using the formation of gas hydrates. Generally, the separation factor has a low value for this mixture, as a result of close values of equilibrium conditions of hydrate formation in the presence of CO 2 and CH 4 . Therefore, increasing the separation efficiency and the process's selectivity is one of the issues that is being investigated. The main objective of this study is related to the investigation of the influence of adding nanoparticles to the aqueous phase on the various parameters such as initial pressure (driving force), gas to liquid ratio and nanoparticle concentration on gas consumption ( n H ), separation factor (S.F) and recovery factor (R) of CO 2 in the process of hydrate based separation of CO 2 from the CO 2 and CH 4 gas mixture. In this work, the process of hydrate based CO 2 capture from CO 2 and CH 4 gas mixture (74 mol% CH 4 and 26 mol% CO 2 ) was studied in the presence of silica nanoparticles (both in pure form and in the presence of KOH) and modified silica. To this purpose, a high pressure vessel was prepared for the gas hydrate formation and dissociation. In order to achieve this aim, all experiments were carried out at a fixed temperature (277.15 K) and two pressures of 30 and 40 bar. It was observed that the presence of nanoparticles enhance the gas consumption, separation factor and recovery factor in all systems, except for the modified silica. The optimum condition was observed for the nanofluid silica + KOH system which in this case, gas consumption, separation factor and recovery factor were improved 36%, 29% and 38%, respectively, compared to the pure water. According to the results of the experiments, the optimum concentration for all systems, including silica and modified silica nanoparticles, was 0.1 weight% and the best results were achieved in this concentration. In the case of the effect of the gas to liquid ratio, it was found that with increasing this ratio, the amount of gas consumption increased and the relative gas consumption (as compared to the amount of feed gas) and the recovery factor decreased, but the separation factor had an optimal amount. On the other hand, the gas consumption is directly related to the initial pressure, but the separation factor and the recovery factor are inversely proportional.