Ethanol dehydrogenation over Cu-SiO[2] catalysts prepared by sol-gel, impregnation, and deposition
techniques

Tomas Pokorny^1, Vit Vykoukal ^1, Petr Machac^1, Ales Styskalik^1

1 Masaryk University, Department of Chemistry, Brno, Czech Republic

 (corresponding author: styskalik@chemi.muni.cz)


ABSTRACT:

Ethanol dehydrogenation to acetaldehyde represents the first step in ethanol-to-butadiene process
and is effectively catalysed by copper. This reaction is critical for the future due to the ongoing
changes in the oil industry: the possible sustainable production of butadiene from bioethanol would
be highly desired. However, catalysts used for this modern purpose mainly suffer from low stability
with time-on-stream [1].

In this study, different Cu-SiO[2] catalysts were prepared by several techniques: hydrolytic and
non-hydrolytic one-pot sol-gel, dry impregnation technique, strong eletrostatic impregnation, and
deposition of pre-made (by hot injection) Cu NPs on silica [2–4]. Both sol-gel prepared catalysts
were highly porous (up to 560 m^2 g^−^1) and exhibited highly homogeneous (“atomic”) copper
dispersion (STEM-EDS). Other synthetic techniques (i.e., impregnation) led to surface area decrease
and provided larger nanoparticles (e.g., 1-3 nm for strong electrostatic impregnation; 10-20 nm for
pre-made Cu NPs) on the catalysts’ surface. Samples were thoroughly characterized both before and
after catalytic tests (TGA, XPS, P-XRD, ICP-OES).

Catalysts were tested in a gas-phase fixed-bed catalytic reactor in ethanol dehydrogenation.
Samples with atomically dispersed Cu prepared by one-pot sol-gel method were highly active. The
stability with time-on-stream was a major issue for all catalysts; severe deactivation was
observed. Catalysts suffered from both particle sintering and coking. The Cu NPs alloying with Ni
and Co was suggested as a possible solution to the deactivation phenomena.


 Figure 1: Sintering of Cu nanoparticles (red color) prepared by strong electrostatic impregnation
                                   during catalysis (STEM-EDS).

References

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4860–4911.

[2]          A. Styskalik, D. Skoda, C.E. Barnes, J. Pinkas, Catalysts 7 (2017).

[3]          V. Vykoukal, V. Halasta, M. Babiak, J. Bursik, J. Pinkas, Inorg. Chem. 58 (2019)
15246–15254.

[4]          L. Jiao, J.R. Regalbuto, J. Catal. 260 (2008) 329–341.