Date of Award

Spring 1970

Document Type

Dissertation

Degree Name

Doctor of Engineering Science in Chemical Engineering

Department

Chemical Engineering and Chemistry

First Advisor

Saul I. Kreps

Second Advisor

Deran Hanesian

Third Advisor

Ching-Rong Huang

Fourth Advisor

Joseph Joffe

Fifth Advisor

Donald G. Lambert

Abstract

A model is proposed for the reactions occurring when an aqueous 30% lactic acid solution is contacted with a primary alcohol, normal butanol. Kinetic and equilibrium data for the esterification reactions of monomeric lactic acid and dimeric lactic acid were determined in a series of experiments using an ideal overflow back-mix reactor. The variables studied were reaction temperature and catalyst concentration.

It was determined that the significant reactions occurring within this system are the esterification of monomeric lactic acid with n-butanol and the esterification of dimeric lactic acid with n-butanol. Other reactions that may be postulated to occur within the system are negligible.

The data is successfully correlated using this reaction model. Rate constants were evaluated at three temperature levels and catalyst levels ranging from zero to 44 mmoles/liter. The observed rate constants vary linearly with catalyst concentration. The Arrhenius parameters for the reactions were determined. The activation energy and frequency factor for the uncatalyzed formation of butyl lactate were found to be 21220 ± 715 cal and (6.258 ± 0.97) x 108 liter/mole-second, respectively. The activation energy and frequency factor for the catalyzed formation of butyl lactate were found to be 10870 ± 550 cal and 8.91 ± 1.10 liter2/mole-second-mmole of cat, respectively. The activation energy and frequency factor for the uncatalyzed formation of butyllactyllactate were found to be 17580 ± 300 cal and (1.303 ± 0.080) x 106 liter/mole-sec, respectively. The activation energy and the frequency factor for the catalyzed formation of butyllactyl-lactate were found to be 7980 ± 645 cal and (4.54+ 0.55) x 10-2 liter2/mole-sec-mmole catalyst.

The equilibrium constant for the butyllactate formation reaction was determined to be 3.13 ± 0.16. The equilibrium constant for the butyllactyllactate formation reaction was determined to be 2.75 ± 0.15.

Equilibrium constants were evaluated at 25°C and were assumed to be constant with respect to temperature and catalyst concentration.

Kinetic and equilibrium data for the hydrolysis of dimeric lactic acid were determined in a series of experiments using an ideal overflow backmix reactor. The variables studied were reaction temperature and catalyst concentration.

Rate constants were evaluated at three temperature levels and catalyst levels ranging from zero to 35 mmoles/liter. The observed rate constants vary linearly with catalyst concentration. The Arrhenius parameters for the reaction were determined. The activation energy and frequency factor for the uncatalyzed hydrolysis of lactyllactic acid were found to be 22930 ± 1617 cal and (6.307 ± 1.88) x 108 liter/mole-second, respectively. The activation energy and frequency factor for the catalyzed hydrolysis of lactyllactic acid were found to be 12360 ± 219 cal and 6.821 ± 0.253 liter2mole-secon-mmole of catalyst, respectively.

The equilibrium constant for the hydrolysis of lactyllactic acid was determined to be 1.27 ± 0.07. The equilibrium constant was evaluated at 25°C and was assumed to be temperature and catalyst independent.

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