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technical support and the large precision instrument platform
for XRD, XPS, SEM and HR-TEM measurements.
Notes and references
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ethanol/acetaldehyde conversion as well as high stability of the
ZnO promoted Zr–Si catalyst. This result was in good agreement
with the study conducted by Sekiguchi, Yasumasa et al.10,43 They
have pointed that a small amount of ZnO can prolong catalyst
life dramatically. As is known, ZrO2 was an high efficient
component to catalysing condensation of acetaldehyde
process44 and much heavier compounds, referred to as C6+ in
the present work, would be formed if adequate acetaldehyde
was added into the feed. Those heavier compounds can be
dehydrated or dehydrogenated on the surface of the catalyst and
transformed into carbon species which may easily cover the
active sites for catalysing ethanol to BD process. The addition of
ZnO into ZrO2–SiO2 system may moderate the speed of acetal-
dehyde condensation process which in turn elevated the selec-
tivity to BD and lowered the selectivity to C6+.
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A series of metal oxide doped ZrO2–SiO2 catalysts were prepared
by sol–gel method and used in the conversion of ethanol and
acetaldehyde into 1,3-butadiene process. The catalysts prepared
by hybrid sol–gel method showed better catalytic performances
compared with those prepared by sol–gel coupled with
impregnation method. ZnO was chosen as the best promoter for
ZrO2–SiO2 catalytic system and Zn0.5–Zr–Si-A catalyst showed
the highest performance with 36.8% ethanol/acetaldehyde
conversion and 83.5% BD selectivity. The reaction conditions
were also optimized with 320 ꢀC, 3.5 and 1.8 hꢁ1 as the
optimum reaction temperature, ethanol/acetaldehyde and
WHSV, respectively. Acid studies showed the addition of ZnO
into ZrO2–SiO2 system can decrease quantity of acidity yet didn't
change the strength of acidity of the catalysts, which in turn
lowered the selectivity to dehydration products and boosted BD
selectivity simultaneously.
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22 R. G. R. Avendano, J. A. D. L. Reyes, J. A. Montoya and
Acknowledgements
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The authors thank the Key Laboratory for Green Chemical 23 Q. Jiang, Z. Y. Wu, Y. M. Wang, Y. Cao, C. F. Zhou and
Technology of Ministry of Education of Tianjin University for
J. H. Zhu, J. Mater. Chem., 2006, 16, 1536–1542.
7148 | RSC Adv., 2017, 7, 7140–7149
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