大港减渣及其超临界溶剂萃取馏分的分子尺寸分布和平均尺寸

重质油的分子尺寸对其催化加工中所用催化剂的设计至关重要。应用隔膜池测定得出大港减压渣油及其超临界流体萃取得到的6个馏分的自由扩散系数，由此计算渣油及其馏分的分子尺寸分布和分子平均尺寸。结果表明，大港减压渣油及其馏分的分子均存在不同程度的尺寸分布，为多分散的混合物体系。萃余残渣的分子尺寸分布范围对比窄馏分明显增宽，多分散程度增大；各个馏分的平均等效直径与平均相对分子质量之间的关系呈现较好的规律性。但是，萃余残渣的分子尺寸随测定时间的变化趋势明显大于窄馏分的，沥青质分子发生聚集可能是其主要原因。大港减压渣油及其馏分的分子尺寸均随累积收率的增加逐渐增大，全馏分的分子尺寸分布范围小于6个馏分的总和，分子的易聚集性可能是造成上述结果的主要原因。

Molecular Size Distribution and Average Size of Dagang Vacuum Residue and Its Fractions

Molecular size of heavy oil is crucial for catalyst design. The bulk phase diffusivities of Dagang vacuum residue(DVR) and its fractions separated by supercritical fluid extraction and fraction (SFEF) were obtained by using a diaphragm cell, from which their molecular size distributions and average sphere equivalent hydrodynamic diameters were calculated. The results indicated that the five narrow SFEF fractions showed slightly polydispersity in molecular size, and the end cut possessed broader size molecular size distribution, meaning that there was higher polydispersity of the end cut than of narrow fractions. 〖JP2〗A good regularity was found between the average equivalent hydrodynamic diameter and the average relative molecular mass in both narrow fraction and the end cut. Strong tendency of asphaltenes to aggregate suggested that the large molecular size of the end cut resulted from the aggregation of asphaltene molecules. The average equivalent hydrodynamic diameters of DVR and its fractions increased with the accumulative yield during determination. The molecular size distribution of the whole DVR was smaller than that of the sum of the six chosen fractions, which might result from the effect of the molecular aggregation.