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

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

Authors 

Jeong-Potter, C. - Presenter, Columbia University
Arellano, M. A., Tec de Monterrey

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

text-indent:.5in">Ru+ O­2 → RuO2

 

Step 2: RuO­2
+ 2H2 → Ru + 2H2O

text-indent:.5in">CO2--DFM + 4H2 → CH4 + 2H2O
+ DFM

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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

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