(562ao) Selective Oxygen Reduction Using Methane for CO2 Purification from a Simulated Flue Gas

Kuhn, A. - Presenter, University of Illinois at Urbana-Champaign
Yang, H., University of Illinois at Urbana-Champaign
Lu, Y., University of Illinois at Urbana-Champaign
Chen, Z., University of Illinois at Urbana-Champaign

Catalytic Oxygen
Reduction using Methane for CO2 Purification from a Simulated Flue

Andrew Kuhn1, Zhitao Chen1,
Yongqi Lu2 and Hong Yang1*

1University of Illinois Urbana Champaign,
Urbana, IL 61801 (USA)

2Prairie Research Institute, Champaign,
IL 61801 (USA)



Introduction. Efficient sequestration of carbon
dioxide (CO2) from flue gas generated from fossil fuel sources
remains a critical endeavor due to the link between rising global temperatures
and increasing atmospheric CO2 concentrations. State of the art
oxy-combustion practices both increase the energy efficiency and maximize the
effluent purity for coal and natural gas power plants (>85% CO2,
dry basis).[1]
Streams with 95% CO2 purity can be utilized in Enhanced Oil Recovery
or chemically-upgraded to value-added chemicals such as methanol. One of the
main impurities, oxygen gas (O2), prevents the direct utilization of
these streams due to undesirable oxidation reactions. Because of selectivity
challenges and the energy requirement, traditional separation technologies
(i.e. membranes and distillation) are unpromising. A new process must be
developed that is both energy efficient and
technologically practical. Here, we propose to catalytically reduce O2
from a simulated flue gas stream to produce high purity CO2.[2]
Methane was used as the primary reducing gas due to its availability and high
energy density (CH4 + 2O2 Wingdings">à CO2
+ 2H2O). In
order to purify flue gas, both the oxygen conversion and selectivity to CO2
must approach 100% because of the tight specifications for O2
and carbon monoxide (CO). Here, we study palladium-based (Pd) catalyst systems as
benchmark catalysts for the purification of CO2 from flue gas. Three
variables to increase the activity of the model Pd system were conducted: the metal
loading, the oxygen-methane feed ratio, and the usage of a copper-based (Cu)
oxygen scavenger sequentially after the Pd bed. This novel approach to purify
and capture CO2 is achieved by careful material design.


Results and Discussion. Pd catalysts were made
by impregnating the precursor onto gamma alumina (γ-Al2O3).
The performance of the catalysts was tested using an
in-house ambient fix-bed reactor system. The CO2 feed composition
was set at 85% (balance: CH4 and O2 at various ratios).
The product compositions were measured (on a dry basis) by gas chromatography.
The temperature was varied from 300 to 600 ºC. Using this fixed bed reactor system,
the Pd catalytic materials were tested for oxygen con
version, selectivity to CO2,
and product CO2 purity. A stoichiometric feed to be optimal for all
catalysts. A summary of the activity of three materials is shown in Figure 1 10.0pt;font-weight:normal">. Notably, the Pd then copper-adsorber (Pd+Cu)
yielded the highest in all three categories. Additionally, we discuss the
outlook for using normal">non-precious metal catalysts to achieve the performance metrics.



. Oxygen conversion,
selectivity to CO2, and product CO2 purity for 1% Pd/Al2O3
(Pd1), 1% Pd/Al2O3 (Pd4), and the sequential beds containing
1% Pd/Al2O3 and 13% Cu/Al2O3 (Pd+Cu).
Ambient pressure. 450 °C. Feed: 50 mL/min (85% CO2, 10% O2,
and 5% CH4). WHSV: 60,000 hr-1.






1.         Buhre,
B.J.P., et al., Oxy-fuel combustion technology for coal-fired power
Progress in Energy and Combustion Science, 2005. 31(4):
p. 283-307.

2.         Kuhn, A.N.,
et al., Sequential Oxygen Reduction and Adsorption for Carbon Dioxide
Purification for Flue Gas Applications.
Energy Technology. 0(0).