1492 Nui et al.
Asian J. Chem.
TABLE-4
OXIDATION OF p-XYLENE BY USING M(OAc)2 AND M(II)-Sal-APTES-SBA-16 CATALYSTS
p-Xylene
conversion
(wt. %)
Product selectivity (wt. %)
Catalyst
p-Toluic
acid
17.2
7.2
4-Carboxyben-
zaldehyde
Terephthalic
acid
p-Tolylaldehyde
Co(OAc)2(3.0) + Mn(OAc)2(1.0)
Mn(3.0)-Sal-APTES-SBA-16
Co(3.0)-Sal-APTES-SBA-16
Co(3.0)-Mn(1.0)-Sal-APTES-SBA-16(C)
Co(3.0)-Mn(1.0)-Sal-APTES-SBA-16(M)
99.8
23.2
45.6
99.7
93.1
56.2
87.4
91.0
32.0
43.8
10.3
2.1
16.3
3.3
4.7
25.8
3.1
1.2
27.2
28.4
15.0
13.2
14.6
shows that occurring of cobalt and manganese are co-catalysts
that enhance the catalytic activity and may be as interference
in Co/Mn/Br- catalyst system with presence of H2O2 oxidant
agent, hence, oxidation reaction of p-xylene follows a free
radical chain mechanism [5,20,21]. Follow this mechanism
Co3+ is formed by reaction of Co2+ with hydrogen peroxide in
acetic acid, after that Co3+ reacts rapidly with Mn2+ to form
Mn3+. The Mn3+ ion abstracts an electron from Br- generate
the bromine radical, Br•, role of the Br• radical is to oxidized
methyl group of p-xylene.
The liquid-phase oxidation reactions of p-xylene with
hydrogen peroxide as the oxidant were examined with these
catalysts. The product selectivity of p-xylene oxidation using
manganese-cobalt complexes was much different from using
single manganese- and cobalt-complex. Especially, cobalt-
manganese complexes catalysts show higher activity and
selectivity than neat metal acetate salts for the oxidation
reaction of methyl group under mild condition.
REFERENCES
It is clear that the presence of both cobalt and manganese
complexes onto the SBA-16 support which was synthesized
by chemically mixed complexes method have a significantly
higher catalytic activity than its synthesized by mechanical
mixed complexes method, its that may be homogenous inter-
ference of active metal ions phase over catalyst system.A novel
finding in the study is selectivity of desirable product for
terephthalic acid with metal complexes catalyst anchored silica
SBA-16 support showed higher homogenous catalyst of neat
metal acetate salts which may be related to the “shape selec-
tivity” effect [22]. As indicated by N2 sorption analysis, the
synthesized SBA-16 have type of mesopore with the cubic
Im3m ordered uniform pore and the diameters in the range
6.2-7.7 nm that is capable of admitting transition complexes
and product [7,9]. Indeed, these pore sizes well coincide with
the diameter of terephthalic acid molecule.
1. K. Weissermel and H.-J. Arpe, in ed: C.R. Lindley, Industrial Organic
Chemistry, VCH, New York, edn 2 (1993).
2. P.P. Rossi and M. Catoni, Process for the Preparation of ω-lactams in
Particular Caprolactam, US Patent 4349473 (1980).
3. K.-T. Li and S.-W. Li, Appl. Catal. A, 340, 271 (2008).
4. Y. Cheng, G. Peng, L. Wang and X. Li, Chin. J. Chem. Eng., 17, 181
(2009).
5. S.A. Chavan, S.B. Halligudi, D. Srinivas and P. Ratnasamy, J. Mol.
Catal. Chem., 161, 49 (2000).
6. R. Chakrabarty, D. Kalita and B.K. Das, Polyhedron, 26, 1239 (2007).
7. S.M. Islam, A.S. Roy, S. Dalapati, R. Saha, P. Mondal, K. Ghosh, S.
Chatterjee, K. Sarkar, N. Guchhait and P. Mitra, J. Mol. Catal. Chem.,
380, 94 (2013).
8. G.R. Bardajee, R. Malakooti, F. Jami, Z. Parsaei and H. Atashin, Catal.
Commun., 27, 49 (2012).
9. C. Baleizão, B. Gigante, H. García and A. Corma, Tetrahedron, 60,
10461 (2004).
10. H.S.Abbo, S.J.J. Titinchi, R. Prasad and S. Chand, J. Mol. Catal. Chem.,
225, 225 (2005).
11. V.D. Chaube, S. Shylesh and A.P. Singh, J. Mol. Catal. Chem., 241, 79
(2005).
12. P. Sharma, A. Lazar and A.P. Singh, Appl. Catal. A, 439, 101 (2012).
13. G.R. Bardajee, R. Malakooti, I.Abtin and H.Atashin, Micropor. Mesopor.
Mater., 169, 67 (2013).
14. C.R. Jacob, S.P.Varkey and P. Ratnasamy, Appl. Catal. A, 182, 91 (1999).
15. O.C. Gobin,Y. Wan, D. Zhao, F. Kleitz and S. Kaliaguine, J. Phys. Chem.
C, 111, 3053 (2007).
16. G.Yang, X. Chen, X. Wang, W. Xing and N. Xu, Chin. J. Catal., 34, 1326
(2013).
17. B.R. Jermy, S.-Y. Kim, K.V. Bineesh and D.-W. Park, Micropor. Mesopor.
Mater., 117, 661 (2009).
18. L. Guczi, R. Sundararajan, Zs. Koppány, Z. Zsoldos, Z. Schay, F. Mizukami
and S. Niwa, J. Catal., 167, 482 (1997).
19. M. Fujiwara, T. Matsushita and S. Ikeda, J. Electron Spectrosc. Relat.
Phenom., 74, 201 (1995).
20. B. Saha and J.H. Espenson, J. Mol. Catal. Chem., 271, 1 (2007).
21. H. Falcon, J.M. Campos-Martin, S.M. Al-Zahrani and J.L.G. Fierro,
Catal. Commun., 12, 5 (2010).
Conclusion
The uniform mesoporous silica SBA-16 was anchored
with manganese-and cobalt-Schiff base complexes to produce
metal-Schiff base-SBA-16 catalyst [Mn(II)-Sal-APTES-SBA-
16 and Co(II)-Sal-APTES-SBA-16]. The manganese- and
cobalt-Schiff bases were synthesized from salicylaldehyde
(Sal), [(3-aminopropyl)triethoxysilane] (APTES) in ethanol
and manganese acetate or cobalt acetate. Powder X-ray diffrac-
tion and transmission electron microscopy (TEM), nitrogen
adsorption-desorption analyses confirm support properties was
maintained after anchoring. The incorporation of Schiff-base
complex matrix caused a decrease in the mesoscopic order,
amount of adsorbed nitrogen, the pore volume, the specific
surface area, the pore diameter and aa increase in the wall
thickness. The DTA-TGA, FT-IR and XPS prove the presence
of manganese- and cobalt-Schiff base complex within the pores
of SBA-16.
22. H. Yang, L. Zhang, W. Su, Q. Yang and C. Li, J. Catal., 248, 204 (2007).