(621aj) Hydrogenation of Carbon Dioxide with Fe/Ni-Catalysts

Hydrogenation
of carbon dioxide with Fe/Ni-catalysts

Georg Baldauf-Sommerbauer, Susanne Lux, Darren Kong, Matthäus
Siebenhofer, Institute of Chemical Engineering and Environmental Technology,
Graz University of Technology, NAWI Graz, Graz, Austria

Conversion of
carbon dioxide with hydrogen to value-added products could be a substantial
approach for CO₂ mitigation. The use of sustainably produced
hydrogen would have a dual advantage: Firstly, CO₂-mitigation and
utilization; secondly, chemical hydrogen storage. In this study the performance
of low-loaded (0.3-1.0 %wt.), supported, bi-metallic Iron/Nickel (Fe/Ni)
catalysts with a Fe/Ni-ration of 2.6-6.6 was investigated with a tubular
reactor setup with online gas analysis. Several potential catalysts were screened,
whereas two types of commercial support materials (alumina and silica) were
compared.

The metal
based catalysts were prepared in an incipient wetness method, followed by
drying, calcining and reduction steps. The effect of
the reduction step was analyzed by the following experimental procedure.

1.    Controlled heating (approx. 2.6
K/min) of the catalyst in N₂/H₂/CO₂ (75/20/5
vol.%) from 298 to 773 K (Screening before reduction)

2.    Reduction of the catalyst in
hydrogen atmosphere at 773 K for two hours

3.    Cooling of the catalyst overnight

4.   
Controlled
heating (approx. 2.6 K/min) of the reduced catalyst in N₂/H₂/CO₂
(75/20/5 vol.%)from 298 to 773 K (Screening after
reduction)

The
analysis of the product gas confirmed the formation of carbon monoxide and
methane. Carbon monoxide formation increases with temperature, whereas methane
formation passes an optimum between 350 and 425 °C. The support material plays
a major role in conversion.

As a main
result an optimal catalyst composition and preparation procedure for high CO₂-conversion
near thermodynamic equilibrium for the reverse watergas-shift
reaction at moderate temperature (350-500 °C) was found. This catalyst is
applicable for the conversion of a CO₂-rich hydrogen feed into a
CO-rich process gas for consecutive Fischer-Tropsch-Synthesis
or methanol production.