Cationic starches as gas hydrate kinetic inhibitors

This work investigated the kinetic inhibiting effect of a number of cationic starches in hydrate formation experiments with methane and methane/ethane and methane/propane gas mixtures. The starches were found to exhibit a very weak inhibiting effect except for tapioca starch which increased the induction time (delay of onset of crystallization) by an order of magnitude. The addition of polyethylene oxide (PEO) was found to further enhance the performance of tapioca starch as well as some of the other starches. Finally, the presence of tapioca starch and PEO was found to suppress the memory effect. The results were interpreted based on a mechanism proposed by Zeng et al. [2006a. Effect of antifreeze protein on nucleation, growth and memory of gas hydrates. A.I.Ch.E. Journal 52(9), 3304–3309; 2006b. Effect of antifreeze proteins on the nucleation, growth and the memory during tetrahydrofuran clathrate hydrate formation. Journal of the American Chemical Society 128, 2844–2850] whereby the starches interfere with nucleation through interactions with heterogeneous nucleation sites.