Amphiphilic-Polymer-Coated Carbon Nanotubes as Promoters for Methane Hydrate Formation

摘要

Despite being a good promoter for methane hydrate formation, carbon nanotubes (CNTs) aggregate easily, which weakens their promotion effect. In this work, highly dispersed carbon nanotubes (CNTs) were prepared by coating the nanotube surface with an amphiphilic copolymer, namely, poly(styrene-co-sodium styrenesulfonate) (PSCS), to accelerate methane hydrate formation. In the presence of functionalized CNTs (f-CNTs), the hydrate storage capacity increased from 46 ± 8 to 138 ± 8 v/v when the PSCS/CNT mass ratio (R) was increased from 0 to 20. In addition, the hydrate formation period gradually shortened as the R value was increased from 5 to 20. The methane uptake was also enhanced from 68 to 135 mmol of gas/(mol of water) as the f-CNT loading was changed from 10 to 150 ppm. Meanwhile, hydrate formation could be completed within 100 min in f-CNT dispersions with high concentrations. Compared with those formed using sodium dodecyl sulfate (SDS) as the promoter, the hydrates formed with f-CNTs as the promoter mainly aggregated at the reactor bottom and generated no foams during the dissociation process. Moreover, the f-CNTs showed excellent recycling performance in eight repeated hydrate formation–dissociation processes with high gas storage capacities of 120–132 v/v, which therefore is of great significance for hydrate-based gas storage and transportation.]]>