8/9/2019 Konf2003 Abstracts 86

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Tatransk Matliare, Slovak Republic, May 26 30, 200386

Kinetics of esterification of maleic anhydride with n-hexanol using selected

catalysts

Miroslaw Grzesik, Jerzy Skrzypek and Maria Lachowska

Institute of Chemical Engineering, Polish Academy of Sciences, Gliwice, Poland, tel. +48 32 2310651, fax: +48 32 2 310318

Aliphatic maleates have wide industrial applications, mainly as additives for polymers.

Esterification reactions of maleic anhydride using aliphatic alcohols run as two-stage reactions:

maleic anhydride + aliphatic alcohol => monoester

monoester + aliphatic alcohol => diester + H2ODetails of technological fundamentals of the esterification reactions of the maleic anhydride using

aliphatic alcohols are well known [1]. Results of kinetic investigations are limited to the knowledge ofthe esterification of the maleic anhydride with ethanol [2] and 2-ethylhexanol [3,4].

The goal of this work is to establish the kinetics of the esterification reactions of the maleic

anhydride using n-hexanol in the presence of selected catalysts. Sulphuric acid and tetrabutyl titanatewill be used here. Furthermore, the process will be carried out without the presence of external

catalyst.

Experiments were conducted in an experimental, thermostatically controlled, semibatch reactor.

The reactor was equipped with a thermometer, sampling cock, azeotropic head with a cooler, and amagnetic stirrer. Gaseous nitrogen was used to purge water from the reaction area. The gas flow

volume was selected using a trial-and-error method.

Reactions were conducted within a range of temperatures from 383 to 433 K, with the initial

molar ratio of aliphatic alcohol to maleic anhydride equal to 3:1, 5:1, and 10:1 and with sulphuric acid

concentrations from 0.05 to 0.2% by weight and constant amount of tetrabutyl titanate.

We used the acid number as a tracer to follow the process and calculated the degree of

conversion. The discrimination method was used, when the kinetic equation was being selected.

It was established that the second stage of the esterification of maleic anhydride with n-hexanol ina presence of sulphuric acid is of a first order in a relationship to the monoester. The reaction rate is

also directly proportional to the concentration of the catalyst sulphuric acid. In case when tetrabutyl

titanate catalyst is used the reaction is second order with respect to acid and alcohol and when no

catalyst is used the reaction is second order with respect to acid.The full kinetic equation can be thus written in a form (M monoester, cat catalyst {sulphuric

acid}, R 1.987 cal/mole K):

Sulphuric acid as catalyst: r = k ccatcM , where k = 4,63 105exp(-14400200/RT) [m

3/(mol min)]

Tetrabutyl titanate as catalyst:

r = k cMcA , where k = 1.86 103exp(-17200400/RT) [m

3/(mol min)],

Noncatalytic reactions: r = k cM2, where k = 1.20 104exp(-18000100/RT) [m

3/(mol min)]

The results from a comparison of calculated acid numbers (based on the kinetic model) comparedwith experimental results were illustrated on charts.

Obtained kinetic equations can be utilised in designing and in optimisation of industrial chemical

reactors for a synthesis of maleate esters of n-hexyl alcohol.

1. Gonorskaja A.G., Marina S.A., Lakokras. mater. ich primen, 1, 18, (1984).

2. Alvarez J.R., Alvarez J.R. Jr, Hung. J., Ind. Chem., 16, 263, (1988).

3. Grzesik M., Skrzypek J., Ptaszek A., Recents Progres en Genie des Procedes, 13(65), 64 (1999).

4. Grzesik M., Skrzypek J., Gumua T., React. Kinet. Catal. Let., 71/1, 13 (2000).