Enhanced methane hydrate formation in the highly dispersed carbon nanotubes-based nanofluid

• Published in: Fuel (Guildford) 2021-02, Vol.285, p.119234, Article 119234
• Main Authors: Song, Yuan-Mei, Liang, Ru-Quan, Wang, Fei, Zhang, Dan-Hui, Yang, Liu, Zhang, Deng-Bo
• Format: Article
• Language: English
• Subjects: Carbon nanotubes; Gas storage efficiency; Growth rate; Methane hydrate
• ISSN: 0016-2361; 1873-7153
• DOI: 10.1016/j.fuel.2020.119234

[Display omitted] •Highly dispersed CNTs grafted by –SO3- groups covalently.•Improved hydrate formation in SCNTs nanofluid.•Great recycling performances of SCNTs used in the repetitive hydrate formations. The hydrate-based technology has been viewed as a great potential approach for the natural gas storage and transportation, whose commercialization however is challenged by the limited energy storage efficiency and slow formation kinetics. In this work, we used carbon nanotubes (CNTs) as carriers and covalently grafted functional group of -SO3- (similar to the hydrophilic group contained in sodium dodecyl sulfate) onto the nano-carriers surface to prepare a novel promoter, sulfonated carbon nanotubes (SCNTs). The SCNTs nanofluid showed higher dispersity and stability than the pristine CNTs (PCNTs). In the methane hydrate formations, the high methane storage capacity of 142 v/v in the SCNTs nanofluid was achieved, whereas 50–65 v/v was obtained with the oxidized CNTs (OCNTs) or PCNTs as promoter. Interestingly, the larger number of sulfonate groups grafted on CNTs, the shorter hydrate formation period and the smaller hydrate reaction stochasticity were obtained. The formation rate was enhanced from 0.237 mmol/(mol water·min) to 0.413 mmol/(mol water·min) when SCNTs concentration grew from 25 mg/L to 150 mg/L. Additionally, the SCNTs kept excellent recycling performance at ten reuses in the methane hydrate formations, which was meaningful to the actual hydrate-based gas storage and transportation.