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Investigation of the Catalytic Efficiency of Cobalt Porphyrins Immobilized

Cobalt porphyrins have been used as catalysts for several organic reactions

1, 2

. A problem

with this catalyst dispersed in solutions is that they can form inactive dimmers

3, 4

, a problem

that can be prevented by immobilization of the catalysts on a support. A former study

indicates that catalysts immobilized on gold wafers strongly improve its homogeneous

congener

1

.

The aim of this project was to extend from two dimensional to three dimensional supports in

an attempt to evaluate the effect on the catalytic activity when going from 2D to a 3D support

with more randomized distribution of the catalytic unit on the support. Another attempt is to

investigate if an up scaling of the process is possible by use of larger surface areas in relation

to volume/weight of the support.

With this method the oxidative catalyst, cobalt porphyrin with thiol linkers (CoTPP-L), was

immobilized via N-Succinimidyl 3-(2-pyridyldithio)-propionate (SPDP) conjugation to

Sicastar

R M-NH2

particles. The immobilized catalyst was successfully used in a

heterogeneous catalytic process for oxidation of hydroquinone to benzoquinone. The catalytic

performance, measured with ultraviolet-visible spectroscopy, was found to be the same as

catalysts supported on gold and about 100 times higher than its homogeneous counterpart.

The content of cobalt porphyrins on Sicastar

R M-NH2

was measured spectrophotometrically

and with Inductively Coupled Plasma – Masspectrometry (ICP-MS).

This study indicates that cobalt porphyrins immobilized on Sicastar

R M-NH2

particles

achieves same catalytic activity as immobilized on gold wafers, which outperformed its

homogeneous congener by far. If Sicastar

R M-NH2

particles should be an alternative support

for up-scaling in heterogenous catalytic processes the efficiency in immobilisation has to be

optimized.

Keywords: