Improvement of Process for Reducing the Benzene Content in Motor Gasoline Using an Emulsion Liquid Membrane and Distillation

摘要

The process for removing toxic benzene from reformate based on an emulsion liquid membrane and distillation was improved and the calculation results of the new and old processes were compared. In the new process, benzene and non-aromatic hydrocarbons with boiling points close to that of benzene are removed from the reformate by two ordinary distillators to yield low-benzene reformate. The benzene and non-aromatic hydrocarbons are separated by the liquid membrane. The process calculation was carried out based on the previous empirical correlation of the mass transfer coefficient in the packed column permeator. Low-benzene reformate of the same flow rate and benzene content as in the previous process could be obtained by distillators with practical numbers of stages and operating conditions. The total aromatics content in the low-benzene reformate was higher than that of the original reformate, in contrast to the previous process. The octane number of the low-benzene reformate is thus higher than that of the original reformate. The yield of benzene was almost the same and the mass fraction of benzene in the product considerably increased. The flow rate of the stream to the permeator, consisting of the benzene and non-aromatics removed from the reformate, was naturally smaller than that in the previous process, where the original reformate was fed directly to the permeator. Therefore, the new process can treat larger amounts of the reformate than the previous process with the equivalent size of permeator. In the solvent recovery step, both the number of distillation stages and the heat energy required could be reduced. Solvent recovery absorbed the major part of the energy for the whole process. The energy requirement for the whole process was therefore lowered.