Green Chemistry
Paper
4. Conclusions
A one-pot method to synthesise NMPD from BDO and MA over
Cu-Ni/ZSM-5 was realized by virtue of the borrowing-hydrogen
methodology. NMPD could be obtained with high efficiency
(
92% yield) over a 3%Cu–3%Ni/ZSM-5 catalyst at 300 °C for 6 h
under 1 MPa pressure of H . Meanwhile, the AAS BET, XPS,
XRD, SEM and TEM characterization results indicated that the
main species on the catalyst surface were Cu O and NiO,
which exhibited a high level of dispersion. H -TPR analyses
2
2
2
revealed that the reductive atmosphere and the synergic effect
of Cu and Ni on the ZSM-5 support enhanced the catalytic
activity. Moreover, a possible mechanism was also proposed,
and the developed Cu–Ni/ZSM-5 could act as an excellent cata-
lyst for the ‘borrowing-hydrogen’ reaction. This process offers
a green and economic route for the synthesis of NMPD, which
also has a promising prospect for industrial application.
Conflicts of interest
Scheme 2 Possible reaction mechanism for NMPD and THF.
There are no conflicts to declare.
Acknowledgements
tion to form an imine (V). Finally, the imine (V) converted to
NMPD via a hydrogenation reaction. For the intermediary com-
pounds in the proposed possible mechanism, we did not find
them in the present stage, and more powerful evidence
requires our continued efforts. The intermediates were specu-
lated on via the mechanism of the borrowing-hydrogen
process according to the previous literature.
Meanwhile, a spot of NMP was detected during the syn-
2
thesis of NMPD in the absence of H , meaning that there was
This work was financially supported by National Key Research
and Development Program of China (No. 2017YFA0403101)
and the National Natural Science Foundation of China
(
No. 21761132014).
2
5,33
Notes and references
another route to produce NMPD. Some of the BDO could
readily generate γ-butyrolactone (VI) under test conditions.
The formed γ-butyrolactone easily converted to NMP (VII) in
the presence of MA, and it was also able to yield NMPD
through hydrogenation over the Ni species. So, the hydrogen
atmosphere could not only promote the borrowing-hydrogen
progress, but also facilitate the by-product NMP turning into
the target product. Consequently, the route for NMPD from
BDO and MA was likely to undergo primary Route A with a sec-
ondary Route B.
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34
As the main product generated over the Cu/Ni separately
exchanged ZSM-5 zeolites (3%Cu/ZSM-5, 3%Ni/ZSM-5, 6%Cu/
ZSM-5 and 6%Ni/ZSM-5), the possible reaction pathway to THF
is also given in Scheme 2 (Route C). After the ion exchange of
+
ZSM-5 zeolites, there are still some H sites on the catalysts.
2
4,27
Based on the previous literature,
the BDO could undergo
+
dehydration and cyclization with the help of H , and such a
process generally needs moderately acid sites. So, the high
selectivity for THF over the Cu/Ni separately exchanged ZSM-5
zeolites maybe due to the suitable acidity. Moreover, it is
difficult to induce the borrowing-hydrogen over the separately
exchanged Cu or Ni on ZSM-5 in the absence of the synergistic 10 T. Toyao, S. M. A. H. Siddiki, Y. Morita, T. Kamachi,
effect.
A. S. Touchy, W. Onodera, K. Kon, S. Furukawa, H. Ariga,
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