高含蜡原油聚烯烃降凝防蜡剂合成及性能评价

Synthesis and performance evaluation of polyolefin pour point depressantand paraffin inhibitor for high waxy crude oil

摘要:

为了保障海上原油长距离管输低温流动安全，以丙烯酸十八酯、十八烯和苯乙烯为单体合成三元共聚物，以其为主剂合成聚烯烃降凝防蜡剂POOS，对三元共聚物的合成条件进行了优化，并对加剂前后原油流变性、析蜡特性、微观形态以及降凝防蜡效果进行评价。结果表明，共聚物优化合成工艺条件为：单体摩尔配比n(丙烯酸十八酯):n(十八烯):n(苯乙烯)=5:3:2，引发剂过氧化苯甲酰质量分数5 ‰，反应温度70 ℃，反应时间8 h。当POOS质量浓度为200 mg/L时，原油流变性与未加POOS原油相比变化明显，15 ℃下加剂前后屈服应力为50.3和2.95 Pa，屈服应力降幅94 %，析蜡温度由31.33 ℃降至24.94 ℃，凝点由25 ℃降至15 ℃，冷指测试防蜡率88 %，环道测试防蜡率83.7 %，微观分析蜡晶形态由针状转变为圆状结晶，析出分布不均匀，多个微小蜡晶聚集析出形成单个聚集体，加剂有效改善蜡晶分散形态，抑制网状结构形成，显著改善原油低温流动效果。

Abstract:

In order to ensure the safety of low-temperature flow in long-distance pipeline transportation of offshore crude oil, a ternary copolymer was synthesized using octadecyl acrylate, octadecene, and styrene as monomers. The polyolefin pour point depressant and wax inhibitor POOS was synthesized using it as the main agent. The synthesis conditions of the ternary copolymer were optimized, and the rheological properties, wax precipitation characteristics, microstructure, and pour point and wax reducing and preventing effects of the crude oil before and after the addition of the agent were evaluated. The results showed that the optimized synthesis process conditions for the copolymer were as follows: monomer molar ratio n(octadecyl acrylate): n(octadecene): n (styrene)=5:3:2, initiator benzoyl peroxide mass fraction 5 ‰, reaction temperature 70 ℃, and reaction time 8 hours. When the mass concentration of POOS is 200 mg/L, the rheological properties of crude oil show significant changes compared to non POOS crude oil. At 15 ℃, the yield stresses before and after adding the agent are 50.3 and 2.95 Pa, with a decrease of 94 % in yield stress. The wax precipitation temperature drops from 31.33 ℃ to 24.94 ℃, the pour point drops from 25 ℃ to 15 ℃, the cold index test shows a wax prevention rate of 88 %, and the ring test shows a wax prevention rate of 83.7 %. Microscopic analysis shows that the wax crystal morphology changes from needle shaped to circular shaped, and the precipitation distribution is uneven, Multiple small wax crystals aggregate and precipitate to form a single aggregate. Adding additives effectively improves the dispersion morphology of wax crystals, inhibits the formation of network structures, and significantly improves the low-temperature flow effect of crude oil.