RSC Advances
Paper
more of the coke. Accordingly, the increase in the external
surface area and mesopore volume and the decrease in the total
concentration of acidic sites promote the stability of the cata-
lysts. In addition, more ZnO clusters are formed in the channels
of HZSM-5-At-acid. This is due to the fact that HZSM-5-At-acid
can provide a more developed pore system during the prepa-
ration of the ZnO/HZSM-5-At-acid catalyst. Thus, this leads to a
shorter distance between the reactants and the active sites,
thereby resulting in acceleration of the reaction rates. Accord-
ingly, pore structure, acidity and ZnO location are important
factors for the synthesis of pyridine and 3-picoline in this
reaction.
6 C. Fernandez, I. Stan, J. P. Gilson, K. Thomas, A. Vicente,
A. Bonilla and J. P ´e rez-Ram ´ı rez, Hierarchical ZSM-5
zeolites in shape-selective xylene isomerization: role of
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9
A. V. Rao, S. J. Kulkarni, R. R. Rao and M. Subrahmanyam,
Synthesis of 2-picoline from acetone over modied ZSM-5
catalysts, Appl. Catal., A, 1994, 111, Ll0l–L108.
4
. Conclusion
In summary, a novel approach for the synthesis of pyridine and
-picoline was developed in this paper. This novel method could
1
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effectively avoid the polymerization of acrolein. Using acrolein
dimethyl acetal as a model reaction, 4-picoline was not found in
the liquid-phase products, making the separation of products
easier. Using acrolein diethyl acetal as the raw material offered a
sustainable method for the synthesis of pyridine and 3-picoline.
It was found that the ZnO-containing catalysts exhibited better
catalytic activity than other catalysts in this work. The stability
of the ZnO/HZSM-5-At-acid catalyst was remarkably higher than
that of the ZnO/HZSM-5 catalyst. The characterization revealed
that the ZnO/HZSM-5-At-acid catalyst possessed a larger
external surface area and mesopore volume, less acidity and
more ZnO clusters located in the channels of HZSM-5-At-acid
relative to the ZnO/HZSM-5 catalyst, thereby leading to longer
stability.
1
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1
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13
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Acknowledgements
This work was supported by the National Natural Science
Foundation of China (Grant. no. 21376068), Program for New
Century Excellent Talents in University, the Ministry of Educa-
tion of P. R. China, and the Program for Fu-Rong Scholar in
Hunan Province, P. R. China.
2
SiO based catalysts, zeolites, and phosphates, Appl. Catal.,
A, 1997, 165, 115–131.
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6 F. Jin, Y. Tian and Y. D. Li, Effect of alkaline treatment on the
catalytic performance of ZSM-5 catalyst in pyridine and
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