(297d) Polymer Anchored Cu(II) and Mn(II) Complex Catalysts for the Oxidation of Styrene

 Polymer Anchored Cu(II) and
Mn(II) Complex Catalysts for the Oxidation of Styrene

Sweta,
Shishir Sinha, Prakash Biswas, Shri Chand^*

            Department of Chemical Engineering, Indian
Institute of Technology Roorkee, India

Styrene
oxidation is of interest from both academic and commercial point of view for
the synthesis of two important products, styrene oxide and benzaldehyde.
Traditionally oxidation of styrene is carried out by using stoichiometric amounts
of organic peracids such as peracetic acid and m-chlorobenzoic acid with permanganate
as the oxidizing agent. However, peracids are very expensive, hazardous and
also propagate the formation of undesirable side products which create
environmental pollution. Therefore
much attention has been paid for the development of new epoxidation methods
which employ safer oxidants and produce little waste. The employment of
hydrogen peroxide, tert-butyl hydroperoxide (TBHP) and oxygen are attractive options both
on environmental and economic grounds.

Immobilisation of active homogeneous catalysts
on solid supports has attracted a lot of interest as heterogeneous catalysts
are inert, easily separated from the product mixture and can be recycled.Polymer
anchored metal complexes are gaining importance as efficient heterogeneous
catalysts in a variety of organic transformations including oxidation and
hydrogenation reactions.

In the
present work, polymer anchored Cu(II) and Mn(II) complex catalysts for the
oxidation of styrene using 30% H₂O₂ as oxidant has been investigated.
The effect of various reaction parameters such as temperature, styrene to H₂O₂
mole ratio and amount of catalyst on the activity and selectivity of catalysts
is studied. The reaction is also carried in batch reactor (Parr reactor, 4843
series) under pressurized conditions. The kinetic parameters have been
evaluated to understand the reaction mechanism. The Cu(II) based catalysts
showed better catalytic activity than Mn(II) based catalysts. The catalyst
recyclability was studied at optimum reaction conditions. It has been observed
that the catalysts can be reused three times without any loss of conversion and
selectivity to the products.

Keywords: Batch reactor, Oxidation, Polymer anchored complexes,
Styrene

* Corresponding author. Email: schanfch@iitr.ernet.in; Telephone: +91-1332-285383