Terahertz Irradiation of Liquid Water Inhibits Methane Hydrate Formation

In the general effort toward a low carbon economy, natural gas (NG) may represent a viable solution in a transition scenario. NG is conveyed through pipelines where, under low temperatures and high pressures that are typically found under sea bottom conditions (1–4 °C and 6–8 MPa), ice-like solid gas hydrates may form, grow, accumulate, and eventually cause complete pipe plugging. To avoid such events, chemical inhibitors are generally added, which chemically disrupt the structure of water, preventing the formation and/or growth of hydrates. To identify alternative chemical-free approaches to hydrate inhibition, the effects of electromagnetic radiation in the terahertz (THz) domain are explored. In this paper, we show, for the first time, that hydrate formation is inhibited by irradiating the water/methane system with THz radiation in the spectral region between 1 and 5 THz. In addition, we show that this inhibition persists for many hours after switching off the irradiation. A tentative explanation of this phenomenon is given in terms of THz radiation interaction with vibrational modes of water in hydrate-like cages. The findings reported herein may be developed into a sustainable, chemical-free hydrate inhibition process.