高压下甲醇-大豆油液液相平衡数据的测定与关联

Determination and Correlation for Liquid-Liquid Phase of Methanol-Soybean Oil under High Pressure

为考察高压下制备生物柴油的原料甲醇与大豆油的相互溶解度，采用高压平衡釜和静态法测定了温度为381．2～472．2K，压力为9．79～19．80MPa条件下甲醇一大豆油二元体系的液液相平衡数据，用PR状态方程对所测的液液相平衡数据进行了关联；PR方程中的参数a和b采用van der Wails单流体混合规则。采用单参数vander Waals模型计算交互参数项aij和bij二者各包含一可调参数kij和lij对可调参数kij和lij采用了与温度无关和与温度有关的2种处理方法，并用实验数据估算了可调参数值。采用与温度无关的可调参数时，用PR方程关联实验数据所得按质量分数计的均方偏差和平均偏差分别为0．0499和0．0222；用与温度有关的可调参数时，均方偏差和平均偏差相应为0．0426和0．0193。结果表明：PR状态方程适用于高压下甲醇与大豆油的液液相平衡计算。

In order to investigate the mutual solubility of the raw material methanol and soybean oil for producing biodiesel under high pressure, the liquid-liquid phase equilibrium data for the methanol-soybean binary system were measured in the temperature range from 381.2 K to 472.2 K and pres- sure range from 9.79 MPa to 18.6 MPa by use of high pressure balance autoclave and static method. The data were correlated with Peng-Robinson state equation. Van der Walls one-fluid mixing rules were used for both a and b parameters in the Peng-Robinson state equation. One parameter Van der Walls model for the cross coefficient terms aij and bij was adopted, both of them contain one adjustable binary interaction parameters kij and tij respectively. Two methods independent and dependent with temperature were used for these adjustable parameters; the values of the parameters kij and lij were estimated with the experimental data. As for Peng-Robinson equation with parameters independent of temperature, the root mean square deviations （RMSD） and average absolute deviations （AAD） in mass fraction were 0. 049 9 and 0. 022 2 respectively. As for Peng-Robinson equation with parameters dependent of temperature, the RMSD and AAD were 0. 042 6 and 0. 019 3 respectively. Therefore, Peng-Robinson state equation could be used to calculate the liquid -liquid phase equilibrium for methanol and soybean oil system under high pressure.