II International Symposium on Carbon for Catalysis ABSTRACTS

PP-I-49
4-Carboxybenzaldehyde (4-CBA) conversion. The reactions were carried out in a batch
autoclave reactor under conditions similar to those in the industry.
Catalysts on modified CNFs were characterized by SEM, BET, TPD-MS, mass titration
and CO chemisorption. Results indicated that physical and chemical properties of platelet
CNFs were very different, depending on the modification conditions. Their physical
properties such as surface area and porosity were affected more significantly by modification
in acetone and concentrated nitric acid than by other modifications, while their chemical
properties were more sensitive to each kind of modification method.
Mass titration measured pH pzc (refer to Table 1) revealed that treatment in air and nitric
acid generated more acidic group on CNF surface, but treatment in acetone, argon and
hydrogen caused more basic surface. TPD analyses showed that the amount of the functional
groups on the surface varied with modification conditions. Treatment in air generated the
more surface groups, whereas hydrogen treatment created fewest surface groups. Fig.1 shows
the catalytic performance of Pd supported on modified CNF for TA hydropurification. Clearly
the catalyst activity was very sensitive to the CNF surface property. Further deconvolution of
TPD spectra elucidated that the carbonyl group on CNF surface was vital for the catalytic
activity of Pd/CNF catalyst for TA hydropurification.
Table 1 Designation of CNF and their pH pzc
100
pH pzc
symbol modification method
C0 Purified CNF 6.65
80
C1 treated in air at 450 o C for 4 h 3.01
C2 Treated in Ar at 900 o C for 4 h 10.22
60
C3 treated in H 2 at 900 o C for 4 h 11.22
C4 refluxed in HNO 3 for 0.5 h 2.50
C0 C1 C2 C3 C4 C5 C6
C5 treated in H 2 O 2 at 25 o modified CNF
C for 24 h 6.63
C6 treated in acetone at 25 o Fig 1 Effect of modification on the
C for 24 h 9.62
catalytic activity of Pd/CNF
In summary, CNF surface chemistry could be tuned by different modification methods.
The catalytic activity of CNF supported catalyst could be controlled by tailoring the surface
chemical property according to a certain specific application such as TA hydropurification.
For TA hydropurification, better activity will be provided when the CNF support is modified
in acetone, or thermal treatment in Ar stream at high temperature, e.g. 900 o C.
4-CBA conversion/%
References
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3862-3866
2 Jing-hong Zhou, Yao Cui, Jun Zhu, et al. Stud. Surf. Sci. Catal. 2005, in press
3 F. Rodriguez-Reinoso., 1998, 36, 159-175
4 Toebes Marjolein L., Prinsloo Frans F., Bitter Johannes H., et al., J. Catal., 2003, 214, 78-87
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