Kinetic study of methane hydrate formation in the presence of carbon nanostructures

Abstract

The effect of synthesized nanostructures, including graphene oxide, chemically reduced graphene oxide with sodium dodecyl sulfate (SDS), chemically reduced graphene oxide with polyvinylpyrrolidone, and multi-walled carbon nanotubes, on the kinetics of methane hydrate formation was investigated in this work. The experiments were carried out at a pressure of 4.5 MPa and a temperature of 0 °C in a batch reactor. By adding nanostructures, the induction time decreases, and the shortest induction time appeares at certain concentrations of reduced graphene oxide with SDS and graphene oxide, that is, at a concentration of 360 ppm for reduced graphene oxide with SDS and 180 ppm for graphene oxide, with a 98% decrease in induction time compared to that in pure water. Moreover, utilization of carbon nanostructures increases the amount and the rate of methane consumed during the hydrate formation process. Utilization of multi-walled carbon nanotubes with a concentration of 90 ppm showes the highest amount of methane consumption. The amount of methane consumption increases by 173% in comparison with that in pure water. The addition of carbon nanostructures does not change the storage capacity of methane hydrate in the hydrate formation process, while the percentage of water conversion to hydrate in the presence of carbon nanotubes increases considerably, the greatest value of which occurres at a 90 ppm concentration of carbon nanotubes, that is, a 253% increase in the presence of carbon nanotubes compared to that of pure water.

Experimental study of methane hydrate generation characteristics in the presence of GO and Re-GO

“…According to the gas law equation and combined with the actual gas parameters, the gas absorption is calculated by the following equation: 39 where Δ n is the gas consumption, R represents the universal gas constant, X 0 and X t are the gas parameters at the initial reaction conditions and time t , respectively, and X can be P , V , and T . Z is the gas compression coefficient, which is calculated using the Peng–Robinson equation.…”

Graphene-Based Kinetic Promotion of Gas Hydrate Formation

“…Moreover, the addition of SDS could improve the stability of nanosheets in aqueous suspensions. Abedi-Farizhendi et al (2019b) synthesized RGO with SDS and polyvinylpyrrolidone (PVP), respectively, which were applied to promote methane hydrate formation at initial conditions of 4.5 MPa and 273.15 K. The results showed that the synthesized promoters both significantly decreased the induction time and considerably increased the water to hydrate conversion while not changing the storage capacity (Figure 2E). On the one hand, the RGO might produce heterogeneous nucleation, which has a lower effective surface energy, causing lower free energy and a lower nucleation barrier than homogeneous nucleation, and is consequently more kinetically favorable than homogeneous nucleation.…”

Effects of Hydrophobic and Hydrophilic Graphene Nanoflakes on Methane Dissolution Rates in Water under Vapor–Liquid–Hydrate Equilibrium Conditions

“…An example of a hydrate-promoting nanomaterial is graphene nanoflakes (GNFs). These carbon nanoparticles have been found to increase the yields of methane hydrates and several other gas hydrate compounds. − However, GNFs are naturally hydrophobic and thus require the addition of surfactants or chemical treatments to improve their stability in solution and avoid settling or agglomeration. , Recent advancements have led to the addition of oxygen-containing groups on GNF powder surfaces through a thermal plasma decomposition and chemical functionalization process. The addition of a specific amount of oxygen-containing groups, typically in the order of 14 at.…”