The_Catalyst_Review_January_2024 - 18

Indium-based Catalysts for CO2
Hydrogenation to Methanol: Key Aspects for Catalytic Performance
In response to the threats posed by global
warming, electrolytic hydrogenation of CO2
has emerged as a viable means of achieving
chemical energy storage and climate change
mitigation. For example, copper-based
catalysts such as Cu/ZnO/Al2
O3 are typically
used for methanol synthesis from mixed
syngas (CO/CO2
/H2). However, this process
suffers from low selectivity due to the reverse
water gas shift (RWGS) reaction as well as
catalyst deactivation and sintering. More
promising results have been obtained using
In2
catalysts. Herein, the authors
set out to identify the best combination
of catalyst support, synthesis, and metal
promoters for In2
O3
/ZrO2
O3
/ZrO2
catalysts in a typical
fixed-bed configuration.
The two most widely used In2
O3
/ZrO2
catalysts
are produced by Alfa Aesar (AA) and Saint
Gobain (SG). Both utilize monoclinic ZrO2
as a support material but exhibit distinct
catalytic performance despite containing the
same amount of In. The In2
O3
/ZrO2
catalysts
were prepared using two different methods
designated as S-AA and M-SG. A comparison
of the CO2
and 75 bar displays significant differences
in the used ZrO2
hydrogenation activity at 300°C
and synthesis method
regarding productivity and yield (Figure 1).
Generally, catalysts prepared according to (M)
showed higher productivity (Pcat
) than catalysts
prepared according to (S). Moreover, the ZrO2
supports supplied by (SG) gave better results
than those of (AA) relative to the mass of the
catalyst.
To further enhance the catalytic performance
of In2
O3/ZrO2 in CO2 hydrogenation to
methanol, various promotors (Cu, Ni, Mg,
Ce) were added to the In2
O3
/ZrO2
catalyst.
These materials can enhance the formation
of methanol in various ways. For example,
basic materials like Ce and Mg can catalyze
the oxidation of in-situ generated CO to
CO2
Figure 2. Catalytic performance of CuO-, NiO-, MgO- and CeO-promoted In2
compared to In2O3/ZrO2
h; T=250°C; p=75 bar; hbed
(M-SG) Reaction conditions: CO2/H2
=5.1+0.1 cm.
O3/ZrO2
=1/3; GHSV=8300 h-1
; TOS=3
Figure 1. Influence of different ZrO (SG or AA) supports and synthesis methods (M
or S) on methanol yield and productivity in comparison to the calculated equilibrium
yield. Reaction conditions: CO2
hbed
/H2
=5.1+0.1 cm.
=1/3; GHSV=8400 h-1
; TOS=3 h; T=300°C; p=75 bar;
, resulting in the formation of additional
oxygen vacancies. To evaluate the different
catalytic activities of the various promoters,
a study was conducted at 250°C and 75 bar
(Figure 2). The NiO-promoted catalyst shows
improved catalytic activity and stability because of a facilitated H2
support. The methanol productivity (Pmeoh) of In2
O3/ZrO2 (M-SG) could be increased from 0.475 gMeOH·g~ cat -1
spillover and strong electronic interactions with the ZrO2
-h -1
to
0.497 gMeOH·g~ cat -1 ·h -1 by the addition of 0.8 wt% Ni without any methane formation. In addition, the NiO-In2
O3
/ZrO2
catalyst remains stable and active over 100 h on stream. Wesner A, Kamp P, Herrmann N, et al. 2023 ChemCatChem, doi.
org/10.1002/cctc.202301125
18
The Catalyst Review
January 2024
The_Catalyst_Review_January_2024

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