Rapid formation of methane hydrates with compact agglomeration via regulating the hydrophilic groups of nanopromoters

Gas hydrates have been endowed with great potential as the medium for natural gas storage & transportation. In this work, we prepared novel nanopromoters by grafting hydrophilic groups (  SO 3 − ,  COO − and  N[CH 3 ] 3 + ) covalently on polystyrene nanospheres (Group@PSNS), and for the first time achieved rapid formation of methane hydrates together compact agglomeration by regulating the hydrophilic groups on the surface of nanopromoters. When  SO 3 − @PSNS was used, methane hydrates formed rapidly but loosely in the reactor; while for  COO − @PSNS and  N(CH 3 ) 3 + @PSNS, even the hydrate formation rate was seriously reduced, the formed hydrates agglomerated compactly in the reactor bottom. Interestingly, when both  SO 3 − and  COO − were fixed on the nanospheres, both the hydrate growth rate and agglomeration compactness were controlled. Especially, the nanopromoter with the  SO 3 − /  COO − molar ratio of 2:1 resulted in the formation of methane hydrates with compact agglomeration morphology within 1–2 hr and with the storage capacity reaching 140–145 vol/vol.