Experimental and computational investigation of hydrophilic monomeric substances as novel CO2 hydrate inhibitors and potential synergists

CO2 hydrate formation in the CO2 transmission pipelines for ocean or geological sequestration can result in pipeline blockage and rupture. Herein, monomeric substances (urea (U), acetamide (A), and glycine (G)) that are easily decomposable were evaluated as kinetic hydrate inhibitors and potential synergists for CO2 hydrate using experimental and computational approaches. The onset temperatures of CO2 + inhibitor hydrates were experimentally measured using a high-pressure autoclave reactor. G showed the best inhibition effect among single inhibitors, and combinations of U + A and A + G made the inhibition synergism for CO2 hydrate. Moreover, molecular dynamics simulations were also conducted to understand the nucleation and formation behaviors of CO2 hydrate in the presence of single and mixed inhibitors at a molecular level. The profiles of F4 order parameters and hydrate counts for each CO2 + inhibitor system followed the experimental results. Analyses of hydrogen bond distributions, radial distribution function, and mean squared displacement were carefully conducted to elucidate the inhibition mechanism of monomeric substances and their inhibition synergism for CO2 hydrate. The experimental and computational results would provide insights into the development of new biodegradable CO2 hydrate inhibitors and contribute to safe transportation and injection of CO2 for long-term storage.