The study on the relationship between the molecular structures of chitosan derivatives and their hydrate inhibition performance

Abstract

Methane hydrate blockage has been a major problem to be solved urgently in the industry of petroleum and natural gas. In this work, seven chitosan derivatives with various hydrophilic/hydrophobic properties were synthesized based on the biodegradable chitosan/carboxymethyl chitosan to study the relationship between the chitosan derivatives’ molecular structures and their hydrate inhibition performance. Our experimental results indicated that the inhibitory effects of chitosan derivatives on methane hydrates were significantly better than that of carboxymethyl chitosan derivatives with similar physicochemical properties or the same functional groups at the same concentration. Moreover, the length and properties of the branched chain of the chitosan derivatives played a vital role in hydrate inhibition, and the long branched chains with hydrophobic functional groups was propitious to enhance the hydrate inhibitory performance of additives. By introducing gas-induced agitation, which created a channel for methane gas to enter the aqueous solution, the hydrate inhibition mechanism of chitosan derivatives was further revealed. The experimental phenomena indicated that the chitosan derivatives with superior hydrate inhibition effects enhanced the interfacial resistance of gas molecules migrating to the liquid phase, thus significantly reducing the gas dissolution velocities and prolonging the induction time of hydrate formation. This study verified the vital role of chitosan derivatives in inhibiting crystallized methane hydrate and provided inspiration for the further research and development of efficient and environmentally friendly kinetic inhibitors.