ESTERIFICATION OF CARBOXYLIC ACIDS AT ROOM TEMPERATURE

Transcription

1 A study on : ESTERIFICATION OF CARBOXYLIC ACIDS AT ROOM TEMPERATURE By : Advanced Multi-Discipline Research and Development Laboratories 5, Lilavati Complex, Sutarwadi, P.O. Kasar-Amboli, Taluka : Mulshi, PUNE Maharashtra, INDIA Page 1 of 5

2 1) INTRODUCTION Room temperature esterification of C1 - C4 aliphatic straight chain acids was studied during The alcohols used were Methanol, Ethanol and n-butanol. Commercialization of the technology so developed was never attempted. The present study i.e. room temperature esterification of straight chain Aliphatic Diabasic acids was undertaken as a sequential investigation. The alcohol used was isopropanol. Iso-Propanol was selected for the following reasons : a. In the previous study, general reaction parameters for esterification with Methanol, Ethanol and n-butanol were already established. b. Iso-Propanol has a different structure and some unique properties. The acids / acid-derivatives studied were Oxalic acid, Maleic Anhydride, Succinic acid and Succinic Anhydride. Physical constants of the finished product as reported in the literature are compared with those obtained experimentally in this study. No attempt was made to evaluate the Kinetics of the reaction 2) Esterification Procedures A Brief Review Historically the most successful laboratory as well as industrial procedure for esterification was and still is the Fischer Esterification Process where the alcohol, the carboxylic acid and the catalyst are refluxed for a varying period of time to get the desired esters. The so called Room Temperature Esterification procedures reported in the literature are basically Reactive esterifications. These Reactive procedures involve the use of reactive intermediates which in most cases have to be prepared separately and are unpleasant and dangerous to handle. There are about 10 different Room Temperature Processes reported in the literature. Most of the intermediates are reactive chlorides or complexes either of the acid or the alcohol or use of alkylating agents with acid, its alkali salt or use of tertiary amines as neutralizing agents. All these intermediates have to be separately synthesized adding to one or more steps in the process, not to speak of the hazardous natures of the intermediates involved. In many cases, these reactive intermediates if uncontrolled can lead to Runaway Reactions. Page 2 of 5

3 3) Room Temperature Esterification : Experimental The process developed by A.M.R.A.D. Labs uses no reactive intermediates, but is still a Room Temperature Esterification using Alcohols, Carboxylic Acids and Catalysts as the only rawmaterials, making it a very safe and non-hazardous procedure Column Reactors for Continuous Esterification Essentially the Room Temperature Esterification is carried out in two columns of glass 30mm in diameter and 30cm in height. Column 1 & 3 contain purified Ion Exchange resin T-63 or T-65 (250g) with the strength of 4.8 m eq /g Column 2 & 4 contain 250g drying agent MgSO 4 (anhydrous) Page 3 of 5

4 Procedure :- 1) Di-isopropyl Maleate :- A) 1.0 mole of Maleic Anhydride is dissolved in 5 moles of Isopropanol. This solution is added gradually from the top of column 1, keeping the stop-cock open and collecting the reaction mixture in a 2 liter beaker. B) The reaction mixture from A) is added gradually from the top of column 2, keeping the stop-cock open. The product mixture is collected in a 2 liter beaker. 5 to 6 repetitions of cycle A-B gives a conversion of % The isopropanol is recovered under reduced pressure, and the residual mass is treated with a saturated solution of sodium bicarbonate till the organic phase is neutral. The organic phase is separated, treated with a little anhydrous MgSO 4 and filtered. Its physical constants determined. Distillation under vacuum gives very pure di-isopropyl maleate. 2) Di-isopropyl Succinate :- C) 1.0 mole of succinic acid is dissolved in 12.0 moles of isopropanol. This solution is added gradually from the top of column 3, keeping the stop-cock open. The reaction mixture is collected in a 2 liter beaker. D) The mixture from C) is added gradually from the top of column 4, keeping the stop-cock open. The reaction product is collected in a 2 liter beaker. 8 to 9 repetition of cycle C-D give a conversion of 80 to 85 %. Isopropanol is recovered under reduced pressure, the residual mass is treated with a saturated solution of sodium bicarbonate till the organic phase is neutral. The organic phase is separated, treated with a little anhydrous MgSO 4 and filtered. Its physical constants determined. Distillation under vacuum gives very pure di-isopropyl succinate. Page 4 of 5

5 4) Physical Constants of Finished Products (Commercial) di iso Propyl Maleate (crude, undistilled) Value by Literature (distilled) Value by our results (undistilled) Melting Point ( C ) Boiling Point ( C ) Refractive Index Density (g/cc) di iso Propyl Succinate (crude, undistilled) Value by Literature (distilled) Value by our results (undistilled) Melting Point ( C ) Boiling Point ( C ) (steady state) Refractive Index Density (g/cc) NOTE : This sample contains free isopropyl alcohol, hence the drop in density 5) Conclusion : This study proves that esterification can be carried out under reasonably mild conditions and the biggest advantage is the sharp drop in energy consumption due to Room Temperature Procedures. There is a distinct advantage in commercializing this process, with regards to saving energy, nonhazardous nature of the process, safety of the workers, etc. 6) Acknowledgements :- We gratefully acknowledge the receipt of approximately 250g of Ion Exchange resins, T-63 from Mr. Tulsidas Awhad and Mr. Mahesh Khedkar of Tulsions Chemical Division, Thermax Ltd. 97-E, MIDC Bhosari, PUNE Page 5 of 5