Esterification of aromatic olefins with acetic acid in the presence of sulphuric acid as a catalyst
Advancing the chemical engineering fundamentals
Catalysis (T2-13P)
Keywords: esterification olefins styrene acid kinetic
Most of the commercially available esters are obtained by the reaction between an alcohol and an organic acid, generally in the presence of a strong mineral acid that acts as a catalyst. The direct esterification of an olefin by an organic acid should be another method to reach identical result of the classic reaction.
In this researching work, esterification reactions of ethenyl benzene and its derivatives were carried out with acetic acid in the presence of sulphuric acid as a catalyst. These compounds have a double bond coupling with the aromatic ring and absorb strongly in the ultraviolet region, which permits a precise analysis when they are in very diluted concentrations. For it, the esterification reactions were carried out and followed in a thermostatized cell device of an ultraviolet-visible spectrophotometer.
A study was made on influence of temperature, catalyst concentration and type of substituted radical have on the conversion of all studied compounds. From the obtained results it can be deduced the following: an increase in temperature and catalyst concentration positively influences the conversion of the corresponding olefins. The substituted radical and the occupied position on the aromatic ring (meta or para) exert a very important influence on the reaction conversion. For identical substitute type, the substituted derivatives in position "para" present a bigger reactivity and olefin conversion than substituted derivatives in position "meta".
The effect of the substitute on the ring benzene over the reaction rate constant of the esterification process can be studied by application of equation:
log k = log ko + x • y
where k is the reaction rate constant of substituted compound and ko is the reaction rate constant of non-substituted compound (ethenyl benzene in this case) as reference value. The parameter "x" is called substitution constant. The parameter "y" is called reaction constant. These values have been calculated with an adequate fitting.
The effect of acidity medium over the reaction rate constant of the esterification process was studied by the application of the Hammett equation.
Finally, a thermodynamic and kinetic study has been done with the calculation of the corresponding parameters.
See the full pdf manuscript of the abstract.
Presented Wednesday 19, 13:30 to 15:00, in session Catalysis (T2-13P).
