Probing effects of thermal and chemical coupling method on decomposition of methane hydrate by molecular dynamics simulation

Abstract

Methane hydrate, being a potential alternative energy source has attracted the attention of many researchers. Here, we investigated the decomposition of methane hydrate with and without alcohols at different temperatures. The results showed that the hydroxyl group of alcohol molecules close to methane hydrate tends to reorient toward methane hydrate. The formation of hydrogen bonds between alcohol and water in methane hydrate cages destabilises the (methane hydrate) structure, thus leading to its decomposition. We also studied the effects of temperature on alcohols used during methane hydrate decomposition by comparing the variations in total potential energy with temperature. We observed that 300 K is the turning point, when the temperature is lower than 300 K, the accelerating effect of alcohol on methane hydrate decomposition is more pronounced. Additionally, the effect of temperature was found to vary with alcohols. For methanol, temperature mainly affects the rate of diffusion; a high rate of diffusion accelerates the decomposition of methane hydrate. For glycerol, temperature mainly affects the interaction energy between glycerol and water, which can accelerate the decomposition of methane hydrate. Our work provides a theoretical basis for future researches into exploitation of methane hydrate by combining thermal stimulation and alcohol.