This Review presents a comprehensive literature review of an important class of kinetic hydrate inhibitors (KHIs) that is based on cyclic amides (lactams). The major aspects of the KHIs, such as their synthesis, inhibition mechanism, toxicity, biodegradability, performance, and cloud point, are thoroughly discussed. Data for 70 KHIs made of homo/co/terpolymers from 330 experiments are collected and evaluated for performance. The effects of the inhibitor concentration, molecular weight, monomer ratio of the co/terpolymers, and 35 different synergist chemicals on various KHIs are also studied. In conclusion, the top 10 KHIs with the highest performances that had a cloud point above 70 °C are presented. The copolymer (1:1) N-vinylpyrrolidone/N-vinyl-caprolactam (VP/VCap) is found to have the highest induction time (IT) of 13 to 14 h at 0.25 wt % and at a cooling rate of 1 °C/h. Some KHIs like Inhibex BIO-800 and poly­(N-vinyl azacyclooctanone) (PVACO) also have a very high ITs (17 and 13.5 h, respectively) at 0.25 wt % and at a cooling rate of 1 °C/h, but they have low cloud points (<25 °C). Guanidinium salts (n-Bu6GuanCl/n-Bu6GuanBr) and a phosphonium salt, (n-Pe)4PBr, are found to be the best synergists for the cyclic-amide-based KHIs. When used at 0.15 to 0.30 wt % along with the KHIs, they further increase the IT by 3–5 h.

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Three plant-based polysaccharides, pectin, k-carrageenan, and guar gum, are investigated as synergists with four kinetic hydrate inhibitors (KHIs), polyvinylpyrrolidone, polyvinylcaprolactam, Luvicap55w, and HIOP. The enhancement in the hydrate inhibition performance is characterized by measuring the increase in the delay/induction time (IT) taken for hydrate nucleation and the reduction in hydrate growth after nucleation. Standardized constant cooling rate hydrate formation tests are performed. Experimental results provided by 0.5 wt % aqueous solutions of reference KHIs are compared with the results of aqueous solutions made with combining 0.25 wt % reference KHI with 0.25 wt % polysaccharide synergist. K-carrageenan showed exceptional inhibition synergy with all KHIs with ITs enhanced around 20–35% with different reference KHIs and reduced hydrate growth rates up to 90%. Guar Gum did not increase the IT provided by reference KHIs. However, it decreased hydrate growth rates by 77–90% of all KHIs. Pectin showed exceptional hydrate inhibition synergy with HIOP (commercial KHI), boosting its IT by 45%.

A uniformly dense dispersion of few layer BP (FLBP) nanosheets in PDMS (polydimethylsiloxane) matrix is shown to exhibit a remarkably strong mechanical energy harvesting effect with highest peak-to-peak voltage output of about 350 V.

Hydrate formation experiments are carried out to evaluate the synergy between three natural proteins (whey protein, casein peptone, and bovine serum albumin (BSA)) and four standard references kinetic hydrate inhibitors (KHIs) (poly­(vinylpyrrolidone) (PVP), poly­(vinylcaprolactam) (PVCap), Luvicap 55w, and HIOP-1800) that are used commercially as well as in research. Hydrate inhibiting efficiency is appraised by comparing the induction times (delay in hydrate nucleation) provided by the reference KHIs and by the blends of KHIs with the proteins. The induction times (ITs) were measured at 0.5 wt% of the reference KHIs to compare against the blended concentrations with 0.25 wt% of the reference KHIs and 0.25 wt% of the protein synergists (keeping the total concentration equal to 0.5 wt.%). Results showed that all the three proteins have hydrate inhibition synergy with the KHIs. Amongst the three proteins, BSA showed the most consistent synergy with the four KHIs and had the largest increase in the ITs. It significantly enhanced PVP’s and PVCap’s ITs by 32% and 19%, respectively. It showed exceptional synergy with HIOP-1800 and enhanced its IT by 65%. When blended with Luvicap 55w, BSA provided almost the same IT as when Luvicap 55w was used alone. Peptone from casein showed its highest synergy with PVCap, and resulted in its IT increase by 15%. The third protein, whey, showed its best synergy with HIOP-1800 and elevated its IT by 15%. Apart from the benefit of enhanced hydrate inhibition (increase in the ITs of most KHIs), these three natural proteins when blended with KHIs at the same total concentration of the inhibitor product make them cost-effective, partially biodegradable, and more sustainable.