Formation of gas hydrates is a major problem in flowlines where gas and water are transported together, and can lead to blockages, downtime, economic losses, and potential accidents. One way of preventing gas hydrates from forming is by injection of kinetic hydrate inhibitors (KHIs). KHIs are typically water-soluble polymers, often containing amide pendant groups. Based on our previous work on high cloud point polymers of N,N-dimethylhydrazidoacrylamide (polyDMHAM) and N,N-dimethylhydrazidomethacrylamide (polyDMHMAM), we have now synthesized a series of N-(pyrrolidin-1-yl)methacrylamide polymers (polyNPyMA) which contains a pyrrolidine-substituted hydrazido pendant group. These polymers show improvement on all previous hydrazido polymers as they exhibit improved KHI performance while having no cloud point in deionized water or 7 wt % aqueous NaCl up to 95 °C. Their performance as KHIs have been investigated using a high-pressure gas hydrate rocker rig at a pressure of 76 bar using a structure II forming natural gas mixture and slow temperature ramping experiments. The best performing polymer, polyNPyMA-II, was kept in the reaction mixture of aqueous isopropyl alcohol and gave an average onset temperature of T_o = 8.1 °C at 2500 ppm. We have shown that isopropyl alcohol functions as a synergist with polyNPyMA, reducing the T_o of polyNPyMA-IV from 10.0 to 9.0 °C when added at 7875 ppm. A common synergist for different KHIs, n-butyl glycol ether (BGE), was found to not significantly improve the performance of polyNPyMA. An interesting feature of hydrazidoacrylamide polymers such as polyNPyMA is that they can be protonated and therefore their solubility characteristics can change with pH. PolyNPyMA was shown to perform better at neutral and high pHs, and less well at low pH. The effect of pH was observed to be smaller than previously reported for polyDMHAM and polyDMHMAM, suggesting that the hydrophilicity obtained by protonation of the hydrazido group affects the polymer less when the hydrazido moiety contains bigger hydrophobic groups. Finally, given the fact that KHI polymer performance is dependent on the molecular weight distribution, this paper also highlights that M_n and M_w values determined by size exclusion chromatography (SEC) using calibration standards can give very different results compared to absolute methods such as multiangle light scattering (MALS).

中文翻译：

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N-（吡咯烷基-1-基）甲基丙烯酰胺的聚合物作为高浊点动力学水合物抑制剂

天然气水合物的形成是天然气和水一起运输的流水线中的主要问题，并可能导致堵塞，停机，经济损失和潜在事故。防止气体水合物形成的一种方法是注入动态水合物抑制剂（KHIs）。KHI通常是水溶性聚合物，通常包含酰胺侧基。根据我们以前对N，N-二甲基肼基丙烯酰胺（polyDMHAM）和N，N-N-二甲基肼基甲基丙烯酰胺（polyDMHMAM）的高浊点聚合物的研究，我们现在合成了一系列N-含有吡咯烷取代的肼基侧基的-（吡咯烷-1-基）甲基丙烯酰胺聚合物（polyNPyMA）。这些聚合物显示出对所有先前的酰肼聚合物的改进，因为它们显示出改进的KHI性能，同时在去离子水或7 wt％的NaCl水溶液（至多95°C）中没有浊点。已使用高压天然气水合物摇臂钻机在76 bar的压力下使用结构II形成天然气混合物并进行了缓慢的升温试验，研究了它们作为KHI的性能。将性能最好的聚合物polyNPyMA-II保留在异丙醇水溶液的反应混合物中，在2500 ppm的条件下，平均起始温度为T _o = 8.1°C。我们已经证明异丙醇可与polyNPyMA协同作用，从而降低T_ø polyNPyMA-IV的从10.0到9.0℃，当在7875 ppm的溶液。不同KHI的共同增效剂，n发现丁基丁二醇醚（BGE）不能显着改善polyNPyMA的性能。肼基丙烯酰胺聚合物（例如polyNPyMA）的一个有趣特征是它们可以被质子化，因此其溶解度特性会随pH的变化而变化。结果表明，PolyNPyMA在中性和高pH下表现更好，而在低pH下则表现不佳。观察到pH值的影响小于先前针对polyDMHAM和polyDMHMAM报道的结果，这表明当肼基部分包含较大的疏水基团时，通过肼基的质子化获得的亲水性对聚合物的影响较小。最后，考虑到KHI聚合物的性能取决于分子量分布，本文还着重指出了M _n和M _w 与绝对方法（例如多角度光散射（MALS））相比，使用排阻色谱法（SEC）确定的标准值可以给出截然不同的结果。