2834
C. Luo et al.
the spectrum of the reaction between DEG(IV) and ethanol were similar, the
proposed route can be confirmed.
Conclusions
Compared with reported procedure, Khan [17] synthesized N-butylmorpholine from
morpholine and 1-chlorobutane (morpholine:choromethane = 1:1.1, mole ratio) at
room temperature for 48 h, with a yield of 81 %. Although this method has high
yield, low cost and a simple process, the generated hydrogen chloride salified with
morpholine which reduced the utility of morpholine. In addition, the hydrogen
chloride seriously corroded the reactor. Zhang [18] synthesized N- methylmorpho-
line from morpholine, paraformaldehyde and methanoic acid at 115 °C for 20 min,
with a yield of 95 %. The method has high yield, short reaction time and a simple
process, but the raw materials were expensive and largely consumed. In addition,
the reaction was of low atom economy and had high production costs. In this paper,
the synthesis of N-alkylmorpholines from DEG(IV), methanol and ammonia in gas–
solid phase was investigated in a fixed-bed reactor over CuO–NiO/c-Al2O3 at the
temperature of 220–225 °C, hydrogen pressure of 0.9–1.0 MPa and LHSV of
0.25 h-1, with a yield of 86.4 %. Compared to the above methods, this method is of
high selectivity, with less pollution, and it is easy to achieve continuous production.
The mechanism of the heterogeneous catalytic reaction of DEG and amination to
N-alkylmorpholines was investigated via in situ DRIFTS. CuO–NiO/c-Al2O3 was
selected as catalyst, and Al2O3 was chosen as a suitable carrier. The total gas flow
was optimized to 15*25 mL min-1, in which H2 flow was 15 mL min-1, and the
NH3 flow was 5 mL min-1. The mechanism of synthesis of N-alkylmorpholines
was proposed and proved that it proceeded along the path of the reaction between
DEG and alkylamine.
Acknowledgments We gratefully acknowledge the generous financial support by a grant from the
National Natural Science Foundation of China (No. 21006087), the Natural Science Foundation of the
Zhejiang Province (No. Y4100147), Zhejiang low carbon fatty amine Engineering Technology Research
Centre (2012E10033) and the Fundamental Research Funds for the Central Universities (2011QNA4018).
References
1. K. Fujita, Y. Enoki, R. Yamaguchi, Tetrahedron 64, 1943 (2008)
2. R.N. Salvatore, C.H. Yoon, K.W. Jung, Tetrahedron 57, 7785 (2001)
3. V.G. Kozin, A.A. Mukhamadiev, Russ. J. Appl. Chem. 74, 1289 (2001)
4. S.P. Hanlon, A. Camattari, S. Abad, A. Glieder, M. Kittelmann, S. Lutz, B. Wirz, M. Winkler, Chem.
Commun. 48, 6001 (2012)
5. S.K. Roy, D.A. Eastmood, Mutat. Res-Gen. Toxicol. Environ. Mutagen. 726, 181 (2011)
6. X. Wang, Z. Tian, Sci. Technol. Chem. Ind. 13, 63 (2005)
7. G. Guillena, D.J. Ramon, M. Yus, Chem. Rev. 110, 1611 (2010)
8. W.J. Bartley, R.G. Cook, K.E. Curry, S.K. Mierau, U.S. Pat. 6,534,441, 2003
9. X.Z. Chen, H. Luo, C. Qian, C. He, React. Kinet. Mech. Catal. 104, 163 (2011)
10. H. Alinezhad, M. Tajbakhsh, R. Zamani, Synth. Commun. 36, 3609 (2006)
11. S.C. Ghosh, S. Muthaiah, Y. Zhang, X.Y. Xu, S.H. Hong, Adv. Synth. Catal. 351, 2643 (2009)
12. M.A. Centeno, I. Carrizosa, J.A. Odriozola, Phys. Chem. Chem. Phys. 1, 349 (1999)
123