Single-Step Silica Nanofluid for the Improved Thermodynamics and Kinetics of Methane Hydrate Stabilized by a Conventional Promoter

Stable synthesis of methane hydrate is the best technique to store an ample amount of methane during storage and transportation. However, the use of conventional promoters is limited by marginal improvement in the kinetics of hydrate, which can be addressed by the use of solid particles if synthesized by a single-step technique. Single-step technique facilitates control on the size of synthesized nanoparticles (NPs) which is not possible with a two-step technique or commercial NPs. Thus, in this study, a single-step technique was used to synthesize silica nanofluids of different NP sizes (5–100 nm) and concentrations (0.5–2 wt %) and compare their impact on kinetic of hydrate, stabilized by a conventional surfactant, cetyltrimethylammonium bromide (CTAB). Nanofluids exhibited superior stability with zeta potential between −36 and −48 mV. Properties such as mole consumption, gas consumed, rate of gas consumed, and apparent rate constant were studied at 6 MPa and two test temperatures 274.15 and 277.15 K. NPs offered significant improvements in the kinetic properties of CTAB-based hydrates, resulting in improved induction time by 56%, while moles of gas consumption and apparent rate constant increased by 88.4 and 184% with NP inclusion of 1.5 wt % at 274.15 K. With an increase in the test temperature by 3 K, these properties marginally reduced at 277.15 K but remained 36.84% higher (in storage capacity) than those of conventional CTAB. The NP concentration of 1.5 wt % was found optimum in the hydrate stabilized by solid particles as further NP addition showed reverse behavior and was considered uneconomical as evident from the results of sample composition of 2 wt % SiO2. It is also important to highlight that the single-step technique is able to synthesize NPs of desired size, which is difficult to achieve with the two-step technique where particles are externally procured followed by mixing with intensive energy. The insights of the study are extremely useful for the use of promoters in effective energy storage during transportation.