Process Description

Reactor 1:

In commercial use two approaches predominate the air oxidation of cyclohxane process. cobalt- catalyzed oxidation and borate promoted oxidation. a third method  the high peroxide process has found limited commercial use . cobalt catalyzed air oxidation of cyclohexane is the most widely used method for producing acipic acid . cyclohexane is oxidized with air at 150c to 160c and 810 to 1,013 kpa in the presence of the cobalt catalyst in a sparged reactor or multistaged column contractor. 

several oxidation stages are usually necessary to avoid over oxidizing the KA mixture . cyclohexane on oxidation gives cyclohexanol and cyclohexanone (alcohol and ketone) with 20% cyclohexane remains unreacted. . unreacted (excess) oxygen is drawn out from the product

Distillation column

oxidizer effluent is distilled to recover unconverted cyclohexane then recycled to the rector feed. the resultant KA mixture may then be distilled for improved quality before being sent to the nitric acid oxidation stage. this process yields 75 yo 80 mole percent KA with a ketone to alcohol ratio of 1:2 and water is completely removed KA mixture consisting of ketonic , alcoholic group and water is the bottom product.

Heat Exchanger:

The lightly viscous mixture is then cooled from 150c-80c using water as a coolant

Reactor 2:

The second step in commercial production of acipic acid is nitric acid oxidation of the cyclohexanol & cyclohexanone mixture. the reaction proceeds as follows:

cyclohexanol+ nutric acid  →  adipic acid +NOX + H2O+ heat

cyclohesanone + nitric acid   →  acipic acid + MOX + H2O + heat

as the reaction is highly exothermic heat of reaction is usually dissipated by maintaining a high ratio (40:1)

of nitric acid to KA mixture

nitric acid 50-660% and a copper vanadium catalyst are reacted with the KA mixture in a reactor vessel at 60c to 80 and .1 o .4 Mpa  . conversion yields of 92 to 96 % are attainable when using high purity KA  feedstock upon reaction niteic acid is reduced to nitrogen oxides : NO2, NO, N2O and N2 

This oxidation results unto the formation of 94% adilpic acid along with NOX, salicylic acid , glutaric acid water and excess HNO3 

Vaccum distillation column

For enhancing the concentration of acipic acid up to 95% vacuum distillation of the mixture is done to remove water produced in the reactor 2

Crystallizer

Now moxture is sent for crystallization to achieve up to 98% pure crystals of adipic acid crystals of adipic acid are obtained with small amount of mother liquor (HNO3, Glutaric acid and salicylic acid)

CENTRIFUGE

The mother liquor is separated from crystals here by washing with water in centrifuge. for obtaining highly purre crystals of acipic acid crystals . crystals are sent to dryer

DRYER

Dryer is used to remove the water used for washing the mother liquor away from crystals in centrifuge if water removal is not done then the crystals may remain impure and cause brittleness which are not suitable for handling and transportation . up to 99% pure crystals acipic acid are obtained . this purity is needed because these crystals are going to be used in the manufacturing of very important plastic nylon

Process flow diagram: