| dc.description.abstract | TITLE: THE OXIDATION OF AROMATIC HYDROCARBONS.
The literature on the oxidation of benzene, phenol, p-quinone
and maleic anhydride has been reviewed. Various kinetic models have
been presented for oxidation of benzene but the most accepted model
assumes the formation of only maleic anhydride and carbon dioxide.
However, during the oxidation of benzene several intermediates are
formed. These are phenol, p-quinone and maleic anhydride. The
kinetic models for these intermediates should be known. Therefore,
oxidation studies of these compounds have also been carried out in
addition to benzene.
Thermodynamic calculations of these compounds reveal that the
oxidation of these compounds is feasible with evolution of several kilo
calories of heat and reactions are irreversible.
Economic calculations reveal that benzene oxidation to maleic
anhydride is feasible even at 10% conversion.
In the oxidation of benzene various catalysts based on vanadia
are used but chromia–vanadia and molybdena–vanadia on silica gel are
selected for comprehensive studies on the basis of good conversion of
benzene to maleic anhydride.
The oxidation of benzene, phenol, p-quinone and maleic anhydride
is carried out in the fluidized bed and the effect of various parameters
viz., temperature, mole ratio of the reactants, time factor, size of
the catalyst, L/D ratios and various gaseous promoters like SO?, NO?
and Br? have been investigated. The effect of these parameters reveals
that maleic anhydride and p-quinone oxidation reactions follow a consecutive
reaction mechanism as follows:
Maleic anhydride -k?? Quinone -k?? Maleic anhydride
? Carbon dioxide
k?? Carbon monoxide.
Phenol oxidation reaction is found to follow the parallel and
consecutive reaction:
Phenol -k?? Quinone
-k?? Maleic anhydride
-k?? Carbon dioxide.
The scheme suggested for benzene oxidation on the basis of the
schemes for the intermediates is given as follows:
Benzene -k?? Phenol -k?? Quinone -k?? Maleic anhydride -k?? Carbon dioxide.
Various rate constants and activation energies for the disappearance
of different species are evaluated.
The effect of the various physical and chemical steps on the
rate of various reactions is investigated and effectiveness factors
for the different catalysts employed in the oxidation of these compounds
are determined.
The design of the fluidized bed reactor and optimization studies
are carried out. The characterization of the flow in the reactor has
been carried out by determining the dispersion factor by R.T.D. concepts. | |
