II International Symposium on Carbon for Catalysis ABSTRACTS

PP-I-51
The result showed that surface treatment of CNF can import different kinds of oxygenic
group on the surface of CNF, and these groups have great impact on the Pd/CNF catalysts,
which increase the interaction between the Pd and the CNF surface. As shown in the TPR
plots (Fig.1), greater interaction between the metal and the support lead to higher peak
temperature. Interestingly, the catalytic activity of Pd/CNF have good correlation between
TPR peak temperature, i.e. the activity increased with the increasing peak temperature, which
was shown in Fig.1 and Table.1 (Cat1~Cat4).
The pretreatment of CNF also have great impact on the Pd metal dispersion of Pd/CNF.
As shown in Table. 1, the Pd metal dispersion measured CO pulse chemisorption varied from
4.1% to 24.3% and the average metal diameters varied from 5.3nm to 26.4. As expected, the
higher the metal dispersion, the higher yield of the Heck reaction. The Pd dispersion of
Pd/AC and Pd/Graphite was close to Pd on CNF, which was 20.4% and 17.5%, respectively;
though the activities of Pd/AC and Pd/Graphite were much lower than Pd/CNF. It might be
caused by two reasons. One is that the surface of CNF has great impact on Pd metal
interaction with CNF, and hence improves the activity. The other is that the specific
microstructure of CNF makes the reactants easier to contact with the active metal which make
the reaction fast.
The reusability of the catalysts was also tested. After separation from the reaction mixture
of the initial run and washing with CH 2 Cl 2 , Cat3 was reused for six times in the same reaction
condition. The recycled catalyst showed high activity nearly to the first run.
In summery, the CNF supported Pd catalysts exhibit high activity towards the Heck
reaction. The activity is improved by the relatively strong metal-support interaction, well
dispersed Pd particles and the mesoporous nature of CNF. The catalysts can be easily
separated from the reaction mixture and reused after washing without loss in activity. As the
Pd/CNF can solve the problems of the traditional homogeneous catalysts, it has a bright future
to replace them and enhance the application of Heck reaction in industrial scale.
223