Investigation into the inhibition of methane hydrate formation in the presence of hydroxy-terminated poly(N-vinylcaprolactam)

Hydroxy-terminated poly(N-vinylcaprolactam) (PVCap-OH) with a narrow molecular weight distribution (PDI = 1.06) has been synthesized. PVCap-OH gave a cloud point of 51.7 degrees C, 10.6 degrees C higher than that of the synthesized PVCap (41.1 degrees C). Its KHI performance was tested using a high-pressure stainless-steel cell with methane gas. Powder X-ray diffraction (PXRD), Raman spectroscopy, and cryo-scanning electron microscopy (cryo-SEM) were used to characterize the micro-structure of the hydrate. It was found that PVCap-OH provided a better KHI performance than PVCap in the same conditions, which gave a higher maximum subcooling and longer induction time, as well as lowered the growth rate of hydrate. The addition of PVCap-OH did not alter the hydrate crystal structure, but reduced the stoichiometric ratio of the peak intensities of the large (5(12) 6(2)) and small (5(12)) hydrate cages (I-L/I-s) and made the hydrate particles more dispersed, which further ensured the gas transportation smoothly