A. Romero et al. / Applied Catalysis A: General 392 (2011) 19–27
27
30
25
20
15
10
be seen in Fig. 13 higher hydrogen selectivity increases as follows
C3 > C2 > C1, being this in agreement with the dehydration capacity
obtained for these catalysts.
a
key Catalyst
C1
C2
C3
4. Conclusions
Impurities from dehydration reactions were due to the pres-
ence of alumina or chromium in the catalyst. Moreover, as acidity
increases so does the dehydration impurities.
For the three catalysts used few differences are obtained in
the profile of impurities from dehydrogenation reactions vs. cyclo-
hexanone yield, being phenol the impurity produced in higher
amounts. Therefore both species Cu+ and Cu0 can be considered
active in dehydrogenation and phenol formation.
Amounts of phenol and condensation impurities grow expo-
nentially when reactions approach to the equilibrium suggesting
that they are formed from cyclohexanone, which even explain the
maximum of cyclohexanone yield observed in Fig. 4.
Although the three catalysts tested were active in cyclohexanol
dehydrogenation it was noticed that higher activity was obtained
with catalyst containing the smaller copper crystallite size.
1,5
1,0
0,5
0,0
30
b
key Catalyst
C1
C2
C3
25
20
15
10
1,5
1,0
0,5
0,0
Acknowledgment
This work was funded by the Spanish Ministry of Science and
Innovation under contract CTM 2006-00317 and PET 2008-0130.
The authors express their gratitude to UBE Corporation Europe S.A.
for its support and Süd-Chemie AG by catalyst supply.
0
20
40
60
80
YONE (%)
Fig. 13. Selectivity to hydrogen from impurities as a function of cyclohexanone
percentage yield for each catalyst and temperature tested, (a) 290 ◦C and (b) 250 ◦C.
References
both temperature tested. As can be seen in this figure, the pro-
file of hydrogen from impurities is similar for the three catalysts.
Moreover, formation of hydrogen is quite low at low cyclohexanone
anone with lower concentration of cyclohexanol. As temperature
increases also the hydrogen produced due to formation of impuri-
ties does.
this work. Benzene yield was already shown in Fig. 9.
[1] J. Ritz, H. Fuchs, H. Kieczka, W.C. Moran, Caprolactam, in: F.Th. Cambell, R. Pfef-
ferkorn, J.R. Rounsaville (Eds.), Ullmann’s Encyclopedia of Industrial Chemistry,
vol. A5, Wiley-VCH, Weinheim, 1986, pp. 31–50.
[2] H.A. Wittcof, B.G. Reuben, Industrial Organic Chemical, John Wiley & Sons, Inc.,
1996, pp. 253–264.
[3] G. Gut, R. Jaeger, Chem. Eng. Sci. 37 (1982) 319–326.
[4] N.V. Nikiforova, K.A. Zhavnerko, Petrol. Chem. URSS 14 (1974) 25–31.
[5] Y.-M. Lin, I. Wang, C.-T. Yeh, Appl. Catal. 41 (1988) 53–63.
[6] C.H. Sivaraj, M. Reddy, B. Kanta, P. Rao, Appl. Catal. 45 (1988) L11–L14.
[7] F.T.M. Mendes, M. Schmal, Appl. Catal. A 163 (1997) 153–164.
[8] A. Romero, A. Santos, P. Yustos, Ind. Eng. Chem. Res. 43 (2004) 1557–1560.
[9] D.V. Cesar, C.A. Peréz, V.M.M. Salim, M. Schmal, Appl. Catal. A 176 (1999)
205–212.
[10] V.Z. Fridman, A.A. Davydov, J. Catal. 195 (2000) 20–30.
[11] P. Téténtyi, Z. Paál, J. Catal. 208 (2002) 494–496.
As can been observed in Figs. 11 and 12 the profiles of impuri-
ties PhOH and 2-CXENONE are quite similar for the three catalysts.
Therefore, from these results in Figs. 11 and 12, it can be inferred
that no differences can be noticed for both copper sites, Cu+ and
Cu0, on dehydrogenation activity.
Phenol is the most important impurity from dehydrogenation
and a slightly major amount is generated by the C3 catalyst. Besides,
phenol amount produced is quite low at low cyclohexanone yield
but increases exponentially as the reaction approaches at equilib-
rium (media rich in cyclohexanone). Rate of formation of phenol
is negligible at low cyclohexanone yield (medium rich in cyclo-
hexanol). Therefore, it is assumed that phenol is produced mainly
from cyclohexanone, being this a remarkable finding. Selectivity to
[12] V.Z. Fridman, A.A. Davydov, J. Catal. 208 (2002) 497–498.
[13] V.Z. Fridman, A.A. Davydov, K. Titievsky, J. Catal. 222 (2004) 545–557.
[14] V. Siva Kumar, S. Sreevardhan Reddy, A.H. Padmasri, B. David Raju, I. Ajitkumar
Reddy, K.S. Rama Rao, Catal. Commun. 8 (2007) 899–905.
[15] D. Ji, W. Zhu, Z. Wang, G. Wang, Communication 8 (2007) 1891–1895.
[16] B.M. Nagaraja, V. Siva Kumar, V. Shashikala, A.H. Padmasri, S. Sreevardhan
Reddy, B. David Raju, K.S. Rama Rao, J. Mol. Catal. A: Chem. 223 (2004) 339–
345.
[17] B.M. Nagaraja, A.H. Padmasari, P. Seetharamulu, K. Hari Prasad Reddy, B. David
Raju, K.S. Rama Rao, J. Mol. Catal. A: Chem. 278 (2007) 29–37.
[18] K.V.R. Chary, K.K. Seela, D. Naresh, P. Ramakanth, Catal. Commun. 9 (2008)
75–81.
[19] J.M. Campos-Martin, A. Guerrero-Ruiz, J.L.G. Fierro, J. Catal. 156 (1995) 209–212.
[20] M.V. Twigg, Catalyst Handbook, 2nd ed., Wolfe, 1989 (Chapter 6).
[21] Z. Wang, J. Xi, W. Wang, G. Lu, J. Mol. Catal. A: Chem. 191 (2003) 123–124.
[22] G. Bai, X. Fan, H. Wang, J. Xu, F. He, H. Ning, Catal. Commun. 10 (2009)
2031–2035.
[23] R.G. Herman, K. Klier, G.W. Simmons, B.P. Finn, J.B. Bulko, T.P. Kobylinski, J.
Catal. 56 (1979) 407–429.
[24] S. Menta, G.W. Simmons, K. Klier, R.G. Herman, J. Catal. 57 (1979) 339–360.
[25] F.M. Bautista, J.M. Campelo, A. García, D. Luna, J.M. Marinas, R.A. Quirós, A.A.
Romero, Appl. Catal. A Gen. 243 (2003) 93–107.
YH
imp
2
SH
=
(6)
imp
2
YH
O
2
[26] F. García-Ochoa, A. Santos, Ind Eng. Chem. Res. 32 (1993) 2626–2632.
[27] J.M. Rynkowski, T. Paryjczak, M. Lenik, Appl. Catal. A Gen. 106 (1993) 73–83.
values obtained for SH imp vs. cyclohexanone percentage yield are
shown in Fig. 13 for e2ach catalyst and temperature tested. As can