Energy efficient methods for isomerization of a C5-C6 fraction with dividing wall fractional distillation

An isomerization process having an isomerized product fractionation zone, said process comprising:

• contacting a combined isomerization zone feed comprising at least normal pentane and normal hexane with an isomerization catalyst in an isomerization zone to isomerize at least a portion of the normal pentane and normal hexane and form an isomerization zone effluent comprising at least C5-C6 normal and branched paraffins;
• passing the isomerization zone effluent into an isomerized product fractionation zone comprising a stabilizer and a dividing wall column, wherein the isomerization zone effluent is passed into a stabilizer to remove butane and light gases and form a stabilized isomerized product;
• passing the stabilized isomerized product into a dividing wall column divided into at least a first and second parallel fractionation zones by a dividing wall, with the first and second fractionation zones each having an upper end and a lower end located within the dividing wall column, wherein the first and second parallel fractionation zones are in open communication at the upper ends with an undivided upper section of the column and wherein the first and second parallel fractionation zones are in open communication at the lower ends with an undivided lower section of the column, and wherein the stabilized isomerized product enters the column at an intermediate point in the first parallel fractionation zone;
• and
• removing at least four streams from the dividing wall column, wherein a low octane stream comprising normal pentane is removed as a first side stream from the second parallel fractionation zone of the dividing wall column and a high octane stream comprising paraffins containing 6 carbon atoms with at least two branches is removed as a second side stream from the second parallel fractionation zone of the dividing wall column, and wherein a high octane stream comprising isopentane is removed from a first end of the dividing wall column.

A process for separating an isomerization zone effluent in a product fractionation zone comprising a stabilizer and a dividing wall column, comprising:

• passing an isomerization zone effluent comprising at least C5-C6 normal and branched paraffins to a stabilizer to remove butane and light gases and form a stabilized isomerized product;
• passing the stabilized isomerized product into a dividing wall column divided into at least a first and second parallel fractionation zones by a dividing wall, with the first and second fractionation zones each having an upper end and a lower end located within the dividing wall column, wherein the first and second parallel fractionation zones are in open communication at the upper ends with an undivided upper section of the column and wherein the first and second parallel fractionation zones are in open communication at the lower ends with an undivided lower section of the column, and wherein the stabilized isomerized product enters the column at an intermediate point in the first parallel fractionation zone;
• and
• removing at least three streams from the dividing wall column, wherein at least one side stream comprising normal pentane and paraffins containing 6 carbon atoms with at least two branches is removed from an intermediate point of the second parallel fractionation zone of the dividing wall column, and wherein a high octane stream comprising isopentane is removed from a first end of the dividing wall column.