Abstract: Due to the various properties and yields of deasphalted oil (DAO) produced by two propane deasphalting units (250 kt/a and 800 kt/a) of Karamay Petrochemical Company, a comparison study was carried out for analyzing the process conditions and products properties. It was found that containing excess﹤560℃ components in the DAO of 800 kt/a unit was the main cause of its low viscosity, high yield and poor viscosity index, which was resulted from the differences in processes and operation conditions of the two units. By analyzing the structure of extractors and extraction process, countermeasures for improving the quality of DAO of 800 kt/a unit were proposed, such as enhancing the severity of vacuum distillation to reduce﹤560℃components in vacuum residue feed, increasing the top temperature of extractor and reducing the solvent to oil ratio in extraction.

Key words: propane deasphalting unit, deasphalted oil, viscosity, viscosity index