柴油降凝剂与柴油组成的感受性研究

Susceptibility Studies of Diesel Fuel Depressant and Diesel Composition

通过红外光谱法确定降凝剂的主要成分为聚乙烯-醋酸乙烯酯。对来自黑龙江、大连、吉林的0号柴油(依次编号为1~3)进行降凝剂感受性实验。结果表明,聚乙烯-醋酸乙烯酯降凝剂对柴油的感受性较好,可使1~3号柴油的凝点分别降低31、9、26℃,冷滤点分别降低18、12、21℃。2号柴油总正构烷烃含量(17.74%)高于1号(14.29%)和3号(13.03%)柴油,其C10~C19含量占总含量的87.2%。2号柴油的正构烷烃含量较高,因此其降凝效果较1、3号差。采用了偏光显微镜、差示扫描量热法(DSC)以及X射线衍射法(XRD)研究了降凝剂对蜡晶形貌和热力学的影响。加入降凝剂后,蜡晶颗粒由不规则的细长棒状变成细小的类球状。DSC分析结果表明,加剂后1、2号柴油析蜡高峰值温度由-1.46、-2.38升至0.46、2.41℃,结晶峰斜~均变小,在相变过程的固-液相变能(ΔH)绝对值由3278、5.283降至3.459、1.737 J/g。降凝剂通过改变固-液相变能来改变柴油的低温流动性。XRD测试结果表明,降凝剂与柴油发生了共晶作用,蜡晶聚集方式改变,单一晶型生长速~降低。综合偏光显微镜与DSC以及XRD结果说明,降凝剂的降凝机理是成核理论与共晶理论的共同作用。

The main component polyethylene-vinyl acetate in pour point depressant was determined by using infrared spectroscopy.No.0 diesel oil from Heilongjiang,Dalian and Jilin(ordinal numbers for 1—3)was studied by depressant susceptibility tests. The results showed that polyethylene-vinyl acetate depressant could reduce the condensation point of No.1—3 diesel by 31,9 and 26℃,and the cold filter plugging point of that by 18,12 and 21℃,respectively,indicating good sensitivity. The total n-alkane content(17.74%)of No.2 diesel was higher than that of No.1 diesel(14.29%)and No.3 diesel(13.03%),with 87.2% of its total content of C10—C19. The effect of pour point depressant of No.2 diesel was worse than that of No.1 and No.3 diesel because higher content of n-alkane in No. 2 diesel. The effect of depressant on wax crystal morphology and thermodynamics was studied by using polarizing microscope,differential scanning calorimetry(DSC)and X-ray diffraction(XRD). After adding depressant,the shape of wax crystal particles became from irregular elongated rod to small class ball. DSC analysis results showed that the wax precipitation peak temperature of No.1 and No. 2 diesel increased from-1.46 and-2.38 to 0.46 and 2.41℃ after adding depressant,the crystallization peak slope decreased,the absolute value of solid-liquid phase change energy(ΔH)in the phase change process decreased from 3278 and 5.283 to 3.459 and 1.737 J/g. The low temperature fluidity of diesel was changed by depressant through changing ΔH. XRD analysis results showed that the eutectic role occurred between depressant and diesel,the way of wax crystal aggregation changed,and single crystalline growth rate decreased. Polarizing microscope,DSC and XRD results indicated that the mechanism of pour point depressant was a combination of crystal nucleation theory and common theory of joint action.