Saponification of Diethyl Adipate With Sodium Hydroxide Using Reactive Distillation

Saponification of Diethyl Adipate With Sodium Hydroxide Using Reactive Distillation


Prepared by:

Dr. Raghdad Karim Qassim al-Mali, Dr. Asrar Abdullah al-Obaidi, Maha Hadi al-Hasani/Department of chemical engineering/college of engineering – University of Baghdad

Abstract

Saponification of diethyl adipate with sodium hydroxide using reactive distillation is a new technique to produce surface active agents (surfactants). These products are hydrocarbon molecules of long chain which have two ends ; one of them is water-loving (hydrophilic). This is the polar end. The other end is water-hating (hydrophobic) which is the organic end. These products are very important in many industrial processes , such as: wetting, washing, emulsification , dispersion and others. The reactive distillation was applied on a consecutive reaction occurred in two steps. The role of distillation process was withdrawing the intermediate product (monoethyl adipate) which is a surface active agent i.e the desired product that had produced from the first – step reaction , before it converted to the final product (disodium adipate) in the second-step reaction. Monoethyl adipate appeared successfully in the liquid distillate and this led to great increase in the percentage conversion from diethyl adipate to monoethyl adipate, which reached to 86%  in comparison with only 15.3% in the case of conducting the reaction without distillation. This met more than 5 times increase . Two layers appeared in both liquids: the distillate and the residue. The upper layer was water layer and the lower layer was diester (diethyl adipate ) layer. Water layer was larger in liquid distillate. The effect of increasing the concentration of sodium hydroxide solution on the percentage conversion from diethyl adipate to monoethyl adipate was studied. It was found that increasing in sodium hydroxide solution concentration to 40% led to increase in percentage conversion .The maximum percentage conversion occurred in the range 40%-60%.After 60% the percentage conversion decreased notably. This research is important in many industrial application through getting some desired intermediate products with high purity . As an example, in petroleum industry it can be applied to get diethanolamine from monoethanolamine before its second conversion to triethanolamine, whence the demand on diethanolamine is more than triethanolamine.