Differences in nucleator adsorption may explain distinct inhibition activities of two gas hydrate kinetic inhibitors

Pipeline blockage by gas hydrate is a serious problem in petroleum industry. Recently, low-dosage inhibitors have been developed. In particular, poly(NN-vinylcaprolactam) (PVCap) is a stronger inhibitor than poly(NN-vinylpyrrolidone) (PVP). In this study, PVCap was also found to have stronger inhibition activity compared to PVP, but it was less effective during reformation of hydrate. To understand the mechanism, the adsorption of PVCap and PVP on silica, a common nucleating agent, was examined using quartz crystal microbalance with dissipation factor observation function. The results reveal that PVP forms a loose film on silica whereas PVCap forms a relatively more rigid and compact film. However, most of the PVCap film could be rinsed off. These results help explain the different inhibition activities of PVCap and PVP.