Patent GB-834276-A (GB)
Title: Benzene recovery from a mixture of a paraffinic and an olefinic feedstock by distillation
IPC: C07C7/00
Filed: 1956-12-03
Abstract: <PICT:0834276/III/1> A modification of the process for recovering benzene from saturated and unsaturated feed-stocks by mixing said stocks and extractively distilling the mixture described and claimed in the parent Specification, comprises mixing a feed-stock containing benzene contaminated with paraffins boiling between 85 DEG  and 96 DEG  C. with a wide boiling range feed-stock containing benzene contaminated with olefines boiling close to benzene and other higher boiling unsaturated hydrocarbons, said stock containing at least 10 wt. per cent aromatics, fractionating the mixture and rejecting a bottoms fraction containing at least a portion of the close-boiling olefines, the paraffins boiling between 85 DEG  and 96 DEG  C., other hydrocarbons boiling above about 85 DEG  C., and very little benzene, and recovering and extractively distilling a benzene fraction.  The saturated feed-stock is fed through line 1 to fractionator 2 from which a 60-96 DEG  C. side stream benzene cut is withdrawn through line 6 where it is joined by the unsaturated feed from line 7 before entering prefractionator 9 through line 8.  95% of the total benzene content is removed as a side stream via line 13 and transferred to extraction zone 14 while the bottoms fraction is rejected via line 12.  A solvent, e.g. phenol, is introduced into zone 14 by line 19, and the solvent extract is taken via line 17 to stripper 18 whence the solvent is recycled to zone 14. Benzene containing between 1 and 4% of olefines is taken off by line 21 after reflux at 20.  In the example the saturated stock is a 60 DEG  to 96 DEG  C. distillate obtained from 2500 barrels of a hydroformed crude stock containing about 159 barrels of benzene by fractionation in a 45-plate column at a 3 : 1 reflux ratio.  The unsaturated stock consists of 2200 barrels of a high temperature cracked naptha fraction which boils from 33 DEG to 143 DEG  C. containing about 460 barrels of benzene.  Tower 9 has 48 plates and is operated at a reflux ratio of about 4 : 1, the cut containing 95% of the benzene which is removed via line 13 having a boiling range of 60-85 DEG  C. and containing 580 barrels of benzene at about 40 vol. per cent concentration.  The phenol extraction in zone 14 is carried out at about 75 molar per cent concentration with a reflux ratio of about 4 : 1.  The overhead temperature in stripper 18 is maintained at about 80.1 DEG  C.  The yield in this example is 557 barrels of benzene at about 98% purity which is further improved by acid treatment.ALSO:A modification of the process for recovering benzene from saturated and unsaturated feed stocks by mixing said stocks and extractively distilling the mixture described and claimed in the parent Specification comprises mixing a feed stock containing benzene contaminated with paraffins boiling between 85 DEG  and 96 DEG  C. with a wide boiling range feed stock containing benzene contaminated with olefines boiling close to benzene and other higher boiling un <PICT:0834276/IV (b)/1> saturated hydrocarbons, said stock containing at least 10 wt. % aromatics, fractionating the mixture and rejecting a bottoms fraction containing at least a portion of the close-boiling olefines, the paraffins boiling between 85 DEG  and 96 DEG  C., other hydrocarbons boiling above about 85 DEG  C., and very little benzene, and recovering and extractively distilling a benzene fraction. The saturated feed stock is fed through line 1 to fractionator 2 from which a 60-96 DEG  C. side stream benzene cut is withdrawn through line 6 where it is joined by the unsaturated feed from line 7 before entering prefractionator 9 through line 8.  95% of the total benzene content is removed as a side stream via line 13 and transferred to extraction zone 14 while the bottoms fraction is rejected via line 12.  A solvent, e.g. phenol is introduced into zone 14 by line 19, and the solvent extract is taken via line 17 to stripper 18 whence the solvent is recycled to zone 14. Benzene containing between 1 and 4% of olefines is taken off by line 21 after reflux at 20.  In the example the saturated stock is a 60 DEG  to 96 DEG  C. distillate obtained from 2,500 barrels of a hydroformed crude stock containing about 159 barrels of benzene by fractionation in a 45 plate column at a 3 : 1 reflux ratio.  The unsaturated stock consists of 2,200 barrels of a high temperature cracked naphtha fraction which boils from 33 DEG  to 143 DEG  C. containing about 460 barrels of benzene.  Tower 9 has 48 plates and is operated at a reflux ratio of about 4 : 1, the cut containing 95% of the benzene which is removed via line 13 having 580 barrels of benzene at about 40 vol. % concentration.  The phenol extraction in zone 14 is carried out at about 75 molar % concentration with a reflux ratio of about 4 : 1.  The overhead temperature in stripper 18 is maintained at about 80.1 DEG  C.  The p  yield in this examples is 557 barrels of benzene at about 98% purity which is further improved by acid treatment.