Effect of polymer aggregation on the kinetics of hydrate formation

Abstract Previous studies have highlighted the importance of low-dosage hydrate inhibitors on the kinetic inhibition of gas hydrates. Here, we investigated the polymers poly(diallyldimethylammonium chloride) (PDADMAC) and poly(acrylic acid) (PAA) as well as their mixtures on the kinetics of hydrate formation. The results show that the polymer mixtures considerably improved the inhibition of hydrate formation. The best inhibition occurred for the mixtures with an excess of PAA2k containing aggregates of around 100 nm in size. The fraction of hydrates formed over time was strongly reduced in the presence of the mixtures, reaching values of accumulated gas consumption of 0.0831 mol for a molar charge ratio Z-/+ = 0.67 compared with 0.6025 mol for water experiments after 15 h. The Johnson–Mehl–Avrami–Kolmogorov (JMAK) phenomenological model was implemented to predict the fraction of transformed hydrate and determine the crystal growth dimensionality. The range of values for the Avrami exponent was 0–1.36, indicating diffusion-controlled one-dimensional growth for methane characterized by the thickening of particles with an appreciable initial volume.