降凝剂对蜡油中蜡析出与溶解影响的物理化学研究

Physicochemical Research on Effect of Pour Point Depressant on Wax Precipitation and Dissolution of Waxy Oil

用 DSC热分析仪研究了合成蜡油的加热与冷却过程 ,测定了蜡油在不同蜡浓度下 ,添加降凝剂前后的平衡蜡溶点和析蜡点以及溶解度和饱和度 ,并进行了热力学分析 .结果表明 ,含蜡油的平衡蜡溶点高于平衡析蜡点 ,降凝剂使平衡蜡溶点进一步升高 ,析蜡点进一步降低 ,导致含蜡油凝点较大幅度降低 .在实验浓度和温度范围内 ,该过程符合 Van′t Hoff方程 ,降凝剂使蜡的溶解焓和溶解熵增大 ,析出焓和析出熵减少 .降凝剂提高了蜡晶析出的临界半径 ,增大了成核位垒 ,使蜡晶析出困难 .

The heating /cooling procedures were studied with differential scanning calorimeter. Equilibrium wax dissolution temperature(WDT), wax precipitation temperature(WPT) and solubility as well as saturation of undoping and doping pour point depressant were measured and analyzed thermodynamically. The results show that equilibrium WDT is higher than WPT, and pour point depressant(PPD) can make the WDT increase and the WPT decrease, resulting in large depression of pour point of waxy oil. The relationship between wax solubility/saturation and temperature accords to Van′t Hoff equation. The dissolving enthalpy and entropy of the wax of pour point depressant doped oil increased, but the precipitation enthalpy and entropy of the wax of pour point depressant doped oil decreased. PPD makes the critical radius and the potential barrier of nucleation of wax crystal increase, and makes the separation of wax from waxy oil difficult.