R.K. Sharma, Y. Monga / Applied Catalysis A: General 454 (2013) 1–10
9
Fig. 11. (a) TEM and SEM images of recovered catalyst after six successive runs of reaction.
3.7. Recycling of catalyst
Appendix A. Supplementary data
The reusability is an important criterion for any catalyst. For
performing the reusability experiments, the catalyst was fixed
magnetically at the side wall of the vessel and rest of the solu-
tion was taken off with a pipette. Then, the vessel was recharged
with fresh solvent and substrate. The result from the next run
confirmed that the catalyst can be re-used and can be further
subjected with fresh substrates for progressive reactions under
identical conditions. The experimental results of successive six
reactions demonstrated that the reactivity of the catalyst did not
undergo any appreciable change in its activity and only a steady
morphology and affectivity of the recovered catalyst isolated after
6th run was assessed from the SEM and VSM analysis. Although
during the reaction, nanocatalysts were subjected to continuous
stirring; it is evident from SEM image (Fig. 11) of reused catalyst
that nanoparticles remain intact confirming its good mechani-
cal strength. Likewise, VSM analysis illustrates that the saturation
magnetization values of the reused catalyst almost remains unal-
tered (14.2 emu/g) (Supplementary material).
Supplementary data associated with this article can be
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In summary, we have presented the successful development of
a highly efficient and industrially relevant catalyst for the synthe-
sis of azoxyarenes. The unique arrangement of Zn(II)–acetylpyridyl
complex over the amine functionalized silica coated magnetic
nanoparticle meets the industrial targets under safe and less-
corrosive conditions without any loss of activity during course
of the reaction. The stability and rigidity of catalyst, use of eco-
nomical magnetic nanoparticles as support, easy recoverability and
reusability, makes it a valuable green catalyst compared to the other
non-magnetic heterogeneous catalytic system. Good yield of prod-
ucts, high TON, reduced reaction time and mild reaction conditions
are the other conspicuous advantages of the applied protocol. Con-
ceivably, it is only a matter of time before the real prospective of
silica coated magnetic nanocatalysts are realized and implemented
on a far-reaching scale.
Acknowledgements
Y. Monga thanks the DST (Department of science and technol-
ogy), New Delhi, India, for awarding the Inspire Fellowship. Also
due thanks to USIC-CLF, University of Delhi, Delhi, India for HR-XRD
and HR-TEM and AIRF, JNU, Delhi, India for SEM analysis.