Gas hydrates are considered a major problem in the oil and gas transportation pipelines, and their crystallization involves nucleation and growth of hydrate crystals. Hence, developing inhibitors that can affect nucleation and growth of hydrates is essential to inhibit their formation. Acrylamide polymers are well-known hydrate inhibitors, but they show a low cloud point, causing precipitation problems for field applications. In this research, we used chitosan to synthesize chitosan-graft-polyacrylamide (CS-g-PAM) as a green and high-cloud-point kinetic hydrate inhibitor (KHIs). The inhibition performance of CS-g-PAM on nucleation and growth of methane hydrate crystals was assessed by a high-pressure autoclave and high-pressure microdifferential scanning calorimeter (HP-μDSC). CS-g-PAM showed no cloud point in both deionized water and 3.5 wt % NaCl solutions, up to 100 °C. Autoclave experiments demonstrated that CS-g-PAM can increase the hydrate nucleation time 13 times (in 1 wt % sample) compared to the pure water system. According to HP-μDSC results, by adding 0.1, 0.5, and 1 wt % CS-g-PAM, the onset methane hydrate formation temperature was decreased from −12.7 °C in the pure water system to −15.8, −17.0, and −19.0 °C, respectively. Also, CS-g-PAM can change the morphology of methane hydrate crystals from solid state into a viscous foam-like slurry. These results show that the modification of acrylamide-based KHIs with natural polymers is an attractive option to improve their deposition point and change the morphology of hydrate crystals.

中文翻译：

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壳聚糖接枝聚丙烯酰胺作为环境友好型高浊点甲烷水合物成核和生长抑制剂的抑制性能

天然气水合物被认为是油气输送管道中的主要问题，其结晶涉及水合物晶体的成核和生长。因此，开发可影响水合物成核和生长的抑制剂对于抑制其形成至关重要。丙烯酰胺聚合物是众所周知的水合物抑制剂，但它们的浊点低，在现场应用时会引起沉淀问题。在这项研究中，我们使用壳聚糖合成了壳聚糖接枝聚丙烯酰胺（CS- g -PAM），作为绿色和高浊点动力学水合物抑制剂（KHIs）。CS- g的抑制性能通过高压釜和高压微分扫描量热仪（HP-μDSC）评估-PAM对甲烷水合物晶体成核和生长的影响。CS- g -PAM在去离子水和3.5 wt％的NaCl溶液（最高100°C）中均未显示浊点。高压釜实验表明，与纯水系统相比，CS- g -PAM可以将水合物成核时间增加13倍（在1 wt％的样品中）。根据HP-μDSC结果，通过添加0.1、0.5和1 wt％的CS- g -PAM，起始甲烷水合物形成温度从纯水系统中的-12.7°C降低到-15.8，-17.0和-分别为19.0°C。另外，CS- g-PAM可以将甲烷水合物晶体的形态从固态变为粘稠的泡沫状浆液。这些结果表明，用天然聚合物对基于丙烯酰胺的KHIs进行改性是提高其沉积点并改变水合物晶体形态的有吸引力的选择。