Experimental investigation of CO2 hydrate formation in silica nanoparticle system under static conditions

Abstract

CO2 hydrate has potential applications in air conditioning cold storage, seawater desalination, carbon capture and storage, etc. Research on CO2 hydrate formation is of great significance in order to solve the problems of long introduction time and slow growth rate. This work focuses on the kinetics of CO2 hydrate formation in the presence of silica nanoparticle under static conditions. A total of 17 sets of experiments were performed with the particle size of 5 nm, 25 nm, 50 nm, 100 nm and the concentration of 0.05 wt%, 0.1 wt%, 0.5 wt%, 1 wt%. We found silica nanoparticles can effectively promote the CO2 hydrate formation and the promotion effect is enhanced with the increase of concentration within a certain range (0–0.5 wt%). The experimental results show that the shortest induction time is reduced by 72.3%, the minimum subcooling degree is reduced by 3 K and the maximum conversion rate is increased by 39%. The promotion or inhibitory effect on hydrate formation depends on the concentration of nanoparticles for hydrophilic nanomaterials. Furthermore, the fluctuation–dissipation in gas consumption in the pre-nucleation stage was proposed with the decay of the fluctuation autocorrelation function obeying to the Onsager hypothesis. The variable parameters n and k of the Avrami equation were obtained and compared to explain the experimental results under different nanoparticle systems.