COMPARISON OF PALLADIUM CATALYSTS BASED ON NANODIAMONDS
67
In general, it can be stated that the catalyst based unsaturated substrates and 2–3 times in the reduction
on activated carbon is 1.5–2.8 times less sensitive to of the nitro group in nitrobenzene and its paraꢀsubstiꢀ
changes in the nature of the substrate than 1 wt % tuted analogs. This can be apparently attributed to the
Pd/NDs (Table 1).
fact that, in the case of NDs, the palladium is reduced
more completely: the binding energy on the Pd3d5/2
level is 335.0 eV, whereas for activated carbon it is
335.3 eV.
A linear dependence in the case of reduction of the
multiple bond of compounds with different functional
substituents (Fig. 1b) is indicative of the preservation
of the hydrogenation mechanism upon a change in the
nature of the support for Pd. All the correlation points
are in a 95% confidence interval. The standard Pearꢀ
son correlation coefficient (R) is 0.95.
ACKNOWLEDGMENTS
We thank N.N. Vershinin, V.A. Bakaev, and
O.N. Efimov (Institute of Problems of Chemical
Physics, Russian Academy of Sciences, Cherꢀ
nogolovka) for assistance in the preparation of the
Pd/ND sample.
This work was supported by the Russian Foundaꢀ
tion for Basic Research, project no. 12ꢀ03ꢀ97546ꢀ
r_tsentr_a.
In the hydrogenation of unsaturated organic comꢀ
pounds (cyclohexene, hexeneꢀ1, allyl alcohol, acrylic,
methacrylic, crotonic, and cinnamic acid), it was
found that the activity of 1 wt % Pd/NDs is 1.3–
1.8 times higher than that of 1 wt % Pd/C (Table 2).
Apparently, the key factor that determines the reducꢀ
tion rate of the multiple bond is the spatial arrangeꢀ
ment of the bond. Compounds with a more sterically
accessible multiple bond—acrylic acid, allyl alcohol,
and hexeneꢀ1 (Table 2, entries 2–4)—undergo hydroꢀ
genation significantly faster than the sterically
screened multiple bond in methacrylic, crotonic, and
cinnamic acids (Table 2, entries 5–7): by a factor of 2–
3 and 1.8–2.6 for the 1 wt % Pd/ND and 1 wt % Pd/C
catalysts, respectively. In addition, the lastꢀmentioned
compounds contain a carboxyl group, which decreases
the electron density on the multiple bond. The unsatꢀ
urated cyclic compound holds an intermediate posiꢀ
tion in this series of substrates and is reduced to cycloꢀ
hexane 1.3–1.5 times worse than compounds 2–4 and
1.2–1.6 times better than compounds 5–7 in the presꢀ
ence of the 1 wt % Pd/C catalyst (Table 2). In the case
of 1 wt % Pd/NDs, the TON values for cyclohexene
and methacrylic and crotonic acids are similar
(Table 2, entries 1, 5, 6). It can be assumed that the
multiple bond of cycloalkene in the halfꢀchair conforꢀ
mation [14] is as hardly accessible to catalytic sites as
the multiple bond of methacrylic acid screened by the
methyl and carboxyl groups.
REFERENCES
1. N. N. Vershinin, N. N. Aleinikov, V. A. Bakaev, and
O. N. Efimov, Ross. Nanotekhnol., No. 5/6, 39 (2008).
2. N. N. Vershinin and O. N. Efimov, RU Patent
No. 2348090 (2009).
3. N. N. Vershinin, O. N. Efimov, V. A. Bakaev, et al., in
9th Biennal International Workshop “Fulllerenes and
Atomic Clusters” (St. Petersburg, 2009), Book of
Abstracts, p. 239.
4. O. N. Efimov, N. N. Vershinin, V. F. Tatsii, et al.,
Al’tern. Energ. Ekol., No. 6, 98 (2007).
5. E. S. Lokteva, E. V. Golubina, S. A. Kachevskii, et al.,
Kinet. Catal. 52, 145 (2011).
6. S. A. Kachevskii, E. V. Golubina, E. S. Lokteva, and
V. V. Lunin, Russ. J. Phys. Chem. A 81, 866 (2007).
7. E. V. Golubina, S. A. Kachevsky, E. S. Lokteva, et al.,
Mendeleev Commun. 19, 133 (2009).
8. E. V. Golubina, E. S. Lokteva, A. G. Majouga, et al.,
Diamond Relat. Mater. 20, 960 (2011).
9. N. A. Magdalinova, P. A. Kalmykov, and M. V. Klyuev,
Pet. Chem. 52, 299 (2012).
Thus, 1 wt % Pd/NDs can be used as a catalyst in
hydrogenation of various organic compounds (nitro
compounds, unsaturated hydrocarbons, alcohols, and
acids). It has been shown that the reduction mechaꢀ
nism of unsaturated compounds is preserved upon
switching from the catalyst based on activated carbon
to the NDꢀsupported sample, while in the hydrogenaꢀ
tion of nitro compounds the reaction mechanism is
apparently determined by the nature of the catalyst. In
the hydrogenation of the >C=C< bond, the nature of
this bond plays an important role: the more accessible
and open the bond, the higher the process rate for the
two catalysts. The activity of the metal in the catalyst
systems based on NDs is higher than that on activated
carbon: by 1.4–1.7 times in the hydrogenation of
10. N. A. Magdalinova, M. V. Klyuev, and P. A. Kalmykov,
Russ. J. Gen. Chem. 84, 33 (2014).
11. M. V. Klyuev, Doctoral Dissertation in Chemistry
(Moscow, 1991).
12. I. V. Berezin and A. A. Klesov, A Practical Treatise on
Chemical and Enzymatic Kinetics (Izd. MGU, Moscow,
1976) [in Russian].
13. P. A. Kalmykov, N. A. Magdalinova, and M. V. Klyuev,
XII International Conference “NANO 2014” (Mosꢀ
cow, July 13 18, 2014), Book of abstracts, p. 1030.
−
14. E. L. Eliel, Stereochemistry of Carbon Compounds
(McGrawꢀHill, New York, 1962).
Translated by M. Timoshinina
PETROLEUM CHEMISTRY Vol. 55
No. 1
2015