Improvement of the Thermal Cracking Product Quality of Heavy Vacuum Residue Using Solvent Deasphalting Pretreatment

摘要

In this work we used the vacuum distillation residue from an Iranian heavy crude oil refinery in a solvent deasphalting (SDA) process using different temperatures (60-120 degrees C), pressures (5-9 bar), solvents (n-pentane and ethyl acetate), and solvent to feed ratios (3 to 1, 5 to 1, and 7 to 1). The resulting products included deasphalted oil (DAO) and residue (PITCH). The DAO yields in SDA when n-pentane was used as solvent were significantly higher than those when ethyl acetate was used as solvent. The DAO was subsequently processed by thermal cracking at 500 degrees C and atmospheric pressure to investigate the effect of solvent deasphalting processing conditions on the yield of coke and liquid products as well as the metal and sulfur content of the produced coke. The results indicated that SDA effectively removed up to 45% of vanadium and up to 40% of nickel from the vacuum residue. Simulated distillation (SimDis) results of the liquid products of thermal cracking of DAO indicated that for both n-pentane and ethyl acetate as the SDA solvent, an increase in the solvent to feed ratio resulted in increased amount of lighter compounds (C-5 - C-20) of the liquid products.