The special electrification of nano-Montmorillonite (MMT) was used to gain organic modified montmorillonite (O-MMT) with long alky side chain containing quaternary ammonium salt by ion exchange. The O-MMT obtained was used for preparing nano-composite EVA/O-MMT with melt blending method. The depressive effects of EVA/O-MMT on Changqing waxy crude oil were studied and compared with the pure EVA depressant. The crystallization characteristics of crude oil was investigated by differential scanning calorimeter (DSC) and morphology of their wax crystal with undoped /doped EVA/O-MMT analyzed using polarized light microscope. The result showed that there was the best performance when addition of EVA/O-MMT was at 50 mg·kg−1. Compared with EVA, EVA/O-MMT could make crude oil gelation point further decrease 2.5℃, did average viscosity reduce 25% at 5℃, the maximum rate of viscosity reduction could be up to 28.2%, and the yield stress of crude oil decreased up to 55.5%. DSC results showed that the addition of nano-montmorillonite could rise the initial crystallization temperature of EVA, could widen the crystallization temperature range and reduce wax precipitation point of crude oil. Microscopic results showed the addition of EVA/O-MMT made wax crystal structure of crude oil more compact.%利用纳米蒙脱土（MMT）特殊的带电性，使用含长烷基侧链的季铵盐对其插层改性得到有机改性蒙脱土（O-MMT）。采用熔融共混法制备O-MMT与EVA（聚乙烯醋酸乙烯酯）降凝剂的复合产物EVA/O-MMT，以国内典型含蜡长庆原油为研究对象，通过流变实验从宏观上评价 EVA/O-MMT 对长庆油的作用效果，并与 EVA 降凝剂进行对比，利用 DSC 和偏光显微镜考察加剂前后原油的结晶特性和蜡晶形貌的变化。结果表明：与纯 EVA降凝剂相比较，EVA/O-MMT在最优加剂浓度50 mg·kg−1下使长庆原油胶凝点、黏度、屈服值进一步降低（胶凝点降低2.5℃，5℃下的平均降黏率为25%，3℃下的屈服值下降55.5%），从而大幅改善长庆原油的低温流变性。DSC放热特性表明O-MMT的引入可以提升EVA的初始结晶温度，拓宽EVA结晶放热区间，降低原油析蜡点。显微结果表明添加EVA/O-MMT的原油在低温下蜡晶结构更致密。
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