(363b) Dual Function Material for the Capture and Catalytic Conversion of CO2 to Fuel from an O2-Containing Flue Gas

Dual Function Material for the Capture and Catalytic
Conversion of CO₂ to Fuel from an O₂-Containing Flue Gas

IEA’s
World Energy Outlook 2018 predicts that with the current and
planned future policies, global energy demand will increase by more than 25% by
2040 and, although renewables will make up more of the global power mix by
2040, coal and gas will remain the first and second largest energy suppliers,
respectively. In addition, a third of energy-related CO­₂ emissions
are locked-in until 2040 due to existing energy infrastructure. Thus, fossil
fuels will remain a major source of energy and will continually contribute to
release of CO₂ to the atmosphere, which is associated with global climate
change, ocean acidification, and other environmental crises [1].
To avoid irreversible damage to our environment, carbon dioxide-reducing
technologies are required for the foreseeable future. Some examples of such
technologies include adsorption via aqueous amine solutions and direct air
capture via membranes [2].
Confidence
that CO₂ can be upgraded or utilized to procure useful products
has aided efforts to develop capturing technology, despite concerns of high
costs [3].

Some
challenges to carbon capture, utilization and storage (CCUS) technologies
include high energy requirement, corrosion, and transportation needs [4].
To mitigate some of these problems, dual function materials (DFMs) were
developed by our group as a novel approach in which CO₂ is captured
from a natural gas power plant flue gas and converted to methane (synthetic
natural gas) in-situ [5]–[7].
Both steps occur in a single reactor at a constant temperature of 320°C
(illustrated in Figure 1), eliminating the need of i) external thermal energy
input as the flue gas exits the power plant in the corresponding temperature
range and ii) the need of transportation as the CO₂ is converted and
recycled directly on site.

The DFM
is composed of an active metallic catalyst (Ru [5]) mixed intimately with an
alkaline sorbent (“Na₂O” [6]), both of which are nano-dispersed on a
porous, high surface area carrier (γ-Al₂O₃ [4-6]). The
material is used to: Step 1) adsorb CO₂ from an O₂-containing
flue gas stream followed by Step 2) off-line catalytic conversion to synthetic
natural gas (methane) upon the introduction of renewable H₂ via a
methanation reaction. The reactions that occur are detailed as follows:

Step 1: CO­₂
+ DFM → CO₂--DFM

Ru+ O­₂ → RuO₂

Step 2: RuO­₂
+ 2H₂ → Ru + 2H₂O

CO₂--DFM + 4H₂ → CH₄ + 2H₂O
+ DFM

Figure
1: Process flow diagram for CO₂ capture and synthetic natural gas
(CH₄) generation for recycle back to a natural gas power plant. The
CO₂ is captured on the DFM (step 1) and catalytically methanated
(step 2) in the same reactor at a constant temperature of 320°C. H₂
required for methanation is generated from renewable sources.

Previous
cyclic aging studies (where 1 cycle = CO₂ capture followed by
methanation) conducted by Wang et al. [7]
showed that scaled up DFM tablets (10g, 5 mm x 5mm) composed of 5% Ru, 6.1% “Na₂O”/γ-Al₂O₃
were stable throughout 50 adsorption and methanation cycles, showing no
deactivation and even a slight improvement in performance. This was supported
by stable BET surface area between fresh and aged samples (101.1 m²/g
to 99.23 m²/g), a slight increase in Ru dispersion after aging (3.90%
to 7.19%), and decreased crystallite size (13.9 nm to 6.20 nm). The DFM was
able to achieve 0.40 mmol/g adsorption of CO­₂ and approach 80%
conversion to methane.

Though
promising, the 5%Ru, 6.1%Na₂O/γ-Al₂O₃ DFM
system is limited by high costs due to the rising
price of ruthenium. Though Ni, a cheaper metal, is commonly used as the
methanation catalyst [8],
[9], it is limited by its poor redubility after the O₂-flue gas
capture step [10].
Instead, we have promising results indicating that a signficant reduction in Ru
loading is possible while maintaining high CO­₂ conversions in DFM at
320°C, consistent with commercial loadings for direct methanation of CO₂
[8],
[11]. Herein, we will seek to optimize the composition of a new DFM,
consequently examining it’s scalability to tablets and stability.

REFERENCES

[1] M. Allen et al., “Framing and Context (Global Warming
of 1.5C, An IPCC Special Report),” 2018.

[2] M. Bui et al., “Carbon capture and storage (CCS): The
way forward,” Energy Environ. Sci., vol. 11, no. 5, pp. 1062–1176, 2018.

[3] L. Irlam, “Global Cost of Carbon Cature and Storage 2017
Update,” 2017.

[4] K. Zenz, C. F. Harvey, M. J. Aziz, and P. Daniel, “The energy
penalty of post-combustion CO2 capture & storage and its implications for
retrofitting the U . S . installed base,” Energy Environ. Sci., vol. 2,
no. 2, 2009.

[5] S. Wang, E. T. Schrunk, H. Mahajan, and and R. J. Farrauto,
“The Role of Ruthenium in CO2 Capture and Catalytic Conversion to Fuel by Dual
Function Materials (DFM),” Catalysts, vol. 7, no. 12, p. 88, 2017.

[6] M. S. Duyar, M. A. Arellano, and R. J. Farrauto, “Dual
function materials for CO₂ capture and conversion using renewable H₂,” Appl.
Catal. B Environ., vol. 168, pp. 370–376, 2015.

[7] S. Wang, R. J. Farrauto, S. Karp, J. H. Jeon, and E. T.
Schrunk, “Parametric, cyclic aging and characterization studies for CO2 capture
from flue gas and catalytic conversion to synthetic natural gas using a dual
functional material (DFM),” J. CO2 Util., vol. 27, no. May, pp. 390–397,
2018.

[8] G. Garbarino et al., “Methanation of carbon dioxide on
Ru/ Al2O3 and Ni/Al2O3 catalysts at atmospheric pressure : Catalysts activation
, behaviour and stability,” Int. J. Hydrogen Energy, vol. 40, no. 30,
pp. 9171–9182, 2015.

[9] P. Frontera, A. Macario, M. Ferraro, and P. Antonucci, “Supported
Catalysts for CO 2 Methanation : A Review,” Cataysts, vol. 59, no. 7,
pp. 1–28, 2017.

[10] M. A. Arellano-Treviño, Z. He, M. C. Libby, and R. J. Farrauto,
“Catalysts and adsorbents for CO2 capture and conversion with dual function
materials: Limitations of Ni-containing DFMs for flue gas applications,” J.
CO2 Util., vol. 31, no. January, pp. 143–151, 2019.

[11] P. J. Lunde and F. L. Kester, “Carbon Dioxide Methanation on a
Ruthenium Catalyst,” Ind. Eng. Chem. Res., vol. 13, no. 1, pp. 27–33,
1974.