Introduction

Chapter 1: Introduction:

Adipic Acid: 

Adipic acid (AA) is one of the most important aliphatic acids with the following chemical formula; COOH(CH₂)4 COOH little of acipic acid occurs naturally but it is produced on large scale all around the world

Physical chemical properties:

Under the normal conditions (room temperature and atmospheric pressure) adipic acid is an odorless, sour tasting solid present as a white powder . the melting point of the acid is 152c . it is solublr in polar solvents the solubility of adipic acid in water grows with increasing temperature

Application of adipic acid :

Adipic acid is an important chemical intermediate the main use of AA is a manufacture of Nylon 6,6 is mainly used for production of fibers (fishing lines , tires , carpets , home furnishing and in tough fabrics for backpacks , parachutes , luggage and business cases) and of resins . Nylon resins are used in electrical connectors auto parts and items such as self-lubricating bearings gears and cams.

although the main use of adipic acid is the above written there are more ways of using acipic acid as can br seen from the figure

Production of A.A 

In 2006 the global AA capacity was around 2.8 million metric tons per year the overall growth for AA is about 3% per year but the demand is growing faster in the year 2010 it was expected ti be abiut 5-6% the most rapidly growing sector is the nylon one where during the past decade it was between 8-10% per year

Current industrial processes

Adipic acid is produced by a two step oxidation process. the first one is oxidation of cyclohexane with air ; the second one is an oxidation of 

a) A mixture of cyclohexanone/cyclohexanol (called KA oil) or

b) only of cyclohexanol with nitric acid

Oxidation of cyclohexane with air:

Cyclohexane is obtained either by the hydrogenation of benzene of from naphtha fraction in small amounts . oxidation of cyclohexane was first performed in the year 1940 by Dupont . the process is performed at temperatures between 150-180c , under the perssure of 10-20 atm , in the presence of Co or Mn organic salts . it is a two step process ; oxidation and deperoxidation step. meanwhile the former one can be done without the catalyst the latter one is always done in the presence of catalyst . the rate limiting step of the process is the synthesis of hydroperoxide its concentration is optimized by carrying out the oxidation in passivated reactors and in the absence of transition metal complexes in order to avoid the decomposition of hydroperoxide , the deperoxidation step in done in the second reactor , where the catalyst amount and reaction condition are optimized , allowing the OL/ONE ratio to be controlled . for the fact that both of the products are more reactive than the starting material . conversion of cyclohexane is kept low only about 5-7% in order to avoid consecutive reactions , the selectivity to KA oil is about 75-80% the byproducts are carboxylic acids and cyclohexylhydroperoxide. the unconverted cyclohexane is recycled

scientific design company has developed a variation of this step it consist in the addition of substantial quantities of anhydrous meta boric acid as slurry in cyclohexane to the first of a staged series of oxidation reactors . no other catalst is necessary . boric acid reacts with cyclohexanol to give a borate ester that  stabilizes the product and reduces its tendency to be oxidized further to form rither cyclohexanone or degradation products . conversion is as high as 10% and selectivity of 90% with molar ratio OL/ONE around 10 . the borate ester formed is easily hydrolysed by hot water to boric acid and cyclohexanol. after distillation a 99.5% OL/ONE mixture is obtained