Recovery of pure benzene, toluene or toluene and xylene from aromatic fraction containing non-aromatics uses on column with main zone of 2 parallel chambers for extractive distillation and extractant recovery

摘要

In the recovery of highly pure benzene, toluene or toluene and xylene containing less than 3000 ppm non-aromatics from a preliminary product (I) containing non-aromatics, which has a narrow boiling point or is azeotropic, extractive distillation of non-aromatics and extractant recovery are carried out in one column, with a main zone of 2 parallel chambers, an enhancing zone above and a drive-off zone below the main zone and a heated sump. Recovery of an aromatic product, consisting of benzene or toluene or toluene and xylene of high purity from a preliminary product (I) containing non-aromatics, which has a narrow boiling point or is azeotropic, involves: (1) separating (I) into not less than 2 higher- and lower-boiling aromatic fractions containing non-aromatics; (2) passing both aromatic fractions to a column, so that the lower-boiling fraction is introduced below the higher-boiling fraction and there is a zone with several theoretical separation stages between the 2 inlets; (3) separating the non-aromatics by extractive distillation with a preferential solvent for the aromatics and discharging the non-aromatics at the top of the column; and (4) separating the extractant from the aromatics by distillation and recycling it to the column. The novel features are that extractive distillation of non-aromatics and recovery of the extractant are carried out in a single column, which has a main zone of 2 parallel chambers, an enhancing zone above the main zone, a drive-off zone below the main zone and a sump with heating. The extractant is concentrated in the drive-off zone, discharged from the sump and added above the enhancing zone. The aromatic fractions are added at separate points of an open chamber below and above the main zone. Non-aromatics are stripped from the extractant and concentrated in the enhancement part. An aromatic product containing less than 3000 ppm non-aromatics is obtained from the other chamber of the main zone, which is sealed from the inside of the column at the top and is the enhancement zone with several theoretical separation stages. An independent claim is also included for the plant used.