黄原胶的化学改性与性能研究
发布时间：2018-10-18 11:33
【摘要】：细菌胞外多糖黄原胶(XG)因其良好的增粘、抗盐、抗剪切以及耐酸碱性能在石油开采领域被广泛应用。但它在使用过程中存在耐温有限、用量大等问题,因此可通过化学改性的方式向黄原胶分子中引入多种官能团并增加其分子量,使其具有更好的耐温性能、更高的粘度以及更强的抗降解能力。据此本论文提出3种改性黄原胶的路线。1.以1-十八烯和马来酸酐的交替共聚物为改性剂,使其与XG在异相条件下发生酯化反应制得了具有微交联结构的改性黄原胶(PX),并通过核磁共振、红外光谱、多角激光光光散射和热重分析进行了结构和形貌的表征。研究表明改性后XG的热转变点由原来的40℃提高50℃,说明酯键的交联以及长烷基链疏水缔合结构的引入使耐温性能大幅提高。当聚合物水溶液浓度达到10g·L-1时,4个PX样品的粘度明显高于黄原胶,尤其是PX-4浓度达到10g·L"1时,其粘度达到1946mPa·s,而黄原胶在相同浓度时粘度仅为790mPa-s。除此以外,改性还使XG的抗盐和抗机械剪切性能有所提高,并且探究聚合物和原油的乳化行为发现,改性黄原胶能使原油乳化为更均匀、更细小的乳状液。2.以十八烷基异氰酸酯为改性剂,利用“一锅煮”法使其与XC在异相条件下发生化学反应制得了两亲性的黄原胶(MXG),并通过核磁共振、红外光谱、元素分析和热重分析进行了结构和热稳定性表征。多角激光光散射测试发现,此改性方法可使黄原胶的表观重均分子量由原来的237万最高增加至658万。通过对比发现,在矿化水中热降解2160h后,MXG-1和MXG-2中粘度分别降为138mPa·s和124mPa·s,而XG粘度降为79mPa·s,说明MXG-1和MXG-2抗老化降解性能更优越。温度和NaCl浓度对聚合物粘度的影响发现,适度MXG比XG具有更优越的耐温和抗盐性能。另外,改性黄原胶具有更高的表面活性,在浓度为5g·L-1时,5个MXG样品中尤以MXG-5表面张力最低,达到52mN·m-1,而XG表张力为63mN·m-1。聚合物和原油的乳化行为表明,疏水基团的引入使改性黄原胶亲油的能力增强,原油的乳化效果得到改善。3.以1-溴代十四烷为改性剂,使其与XG在异相条件下发生醚化反应制得了改性黄原胶BX,并通过核磁共振、红外光谱、热重分析和多角激光光散射进行了结构和形貌表征。通过研究XG和BX水溶液与正庚烷之间的界面张力随聚合物浓度的变化情况可以发现,疏水基团的引入赋予黄原胶一定的界面活性,使改性黄原胶更易在水／油界面发生吸附,导致溶液界面张力明显下降,当浓度为5g.L-1,黄原胶和正庚烷之间的界面张力为48mN·m-1,而改性黄原胶BX-3与正庚烷之间的界面张力最低可以降至37mN·m-1。另外,聚合物长期老化稳定测试表明：通过醚化手段向黄原胶接枝适当比例的疏水基团可改善其水溶液抗老化稳定性能,本实验条件下以4g黄原胶与0.5g溴代十四烷反应为最佳。
[Abstract]:Bacterial extracellular polysaccharide xanthan gum (XG) has been widely used in petroleum exploitation for its good viscosity, salt resistance, shear resistance and acid and alkaline resistance. However, it has some problems such as limited temperature resistance and high dosage, so it can introduce various functional groups into xanthan gum molecule by chemical modification and increase its molecular weight to make it have better temperature resistance. Higher viscosity and higher resistance to degradation. Based on this, three kinds of modified xanthan gum routes are put forward. 1. The modified xanthan gum (PX), with microcrosslinked structure was prepared by esterification of 1-octadecene and maleic anhydride as modifier under heterogeneous conditions. The structure and morphology were characterized by polygonal laser scattering and thermogravimetric analysis. The results show that the thermal transition point of modified XG is increased by 50 鈩，
本文编号：2279002
[Abstract]:Bacterial extracellular polysaccharide xanthan gum (XG) has been widely used in petroleum exploitation for its good viscosity, salt resistance, shear resistance and acid and alkaline resistance. However, it has some problems such as limited temperature resistance and high dosage, so it can introduce various functional groups into xanthan gum molecule by chemical modification and increase its molecular weight to make it have better temperature resistance. Higher viscosity and higher resistance to degradation. Based on this, three kinds of modified xanthan gum routes are put forward. 1. The modified xanthan gum (PX), with microcrosslinked structure was prepared by esterification of 1-octadecene and maleic anhydride as modifier under heterogeneous conditions. The structure and morphology were characterized by polygonal laser scattering and thermogravimetric analysis. The results show that the thermal transition point of modified XG is increased by 50 鈩，
本文编号：2279002
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