The selective role of multipolar interaction in the formation of CH4 and CO2 clathrate hydrates

Abstract

The interaction of sodium dodecyl sulfate (SDS) with CH4 and CO2 has been ana- lyzed by performing Molecular Dynamics simulations. Results indicate that SDS while promoting the formation of methane clathrate inhibits the formation of the carbon dioxide one. The effect is attributed to the different charge distribution on the gas molecules. The CH4 molecule is, in fact, characterized by the absence of permanent dipole and quadrupole moments (having only a small octupole moment compatible with a very symmetric charge distribution), while the CO2 one has a large quadrupole moment. Accordingly, the SDS-CH4 interaction has almost null electrostatic nature while the SDS-CO2 one has a remarkable electrostatic nature.