performance of a catalytic membrane reactor for air revitalization system

(ARS) and in situ resource utilization (ISRU) of indigenous resource on Mars.

For the proper performance of space life-support systems, for example, the

removal from the cabin atmosphere of the CO2 produced by the inhabitants is

required. For short-term flights, CO2 can be controlled by sorption on metal

hydroxide adsorbents [1]. For long-term space applications, however, continuous

regenerative approaches are required, including pressure-swing adsorption and

membranes which, in addition to removing the CO2, may, potentially, also allow

for the recovery of oxygen [2]. One approach proposed is the use of the

methanation (Sabatier) reaction, in which CO2 reacts catalytically with

hydrogen to simultaneously produce methane and water. In space applications,

an important challenge for the application of catalytic reactor technology is

the dilute concentrations of CO2, which make its pre-concentration a required

step, thus complicating the process train. In this study, we investigate the

application of a reactive separation technology, in which the catalytic and

separation steps are coupled in-situ through the use of high-temperature

membranes.

Another potential application of the Sabatier reaction may be in the ISRU

on Mars. ISRU is a very important new concept to be used to make human

presence on Mars possible. This concept involves utilizing raw resources

from Mars atmosphere to create useful commodities, such as oxygen and

propellants like CH4 [3]. The Sabatier reaction is so highly exothermic that

make the internal temperature control of this unit a challenging task.

Therefore, the process must perform thermally optimal in order be

to obtain higher performance.

For this purpose, the isothermal reaction data were analyzed using

Hougen-Watson type rate equation [4, 5]. To validate the model used in the

design simulations, and the applicability of the rate expressions, we also

carried a series of MR experiments. Agreement between the experiments and

the model predictions is satisfactory, particularly given the various

simplifying assumptions in the model. The experimentally-validated model

is used to study the design characteristics of both the ARS and ISRU

systems. In the paper, we describe our current experimental and modeling

efforts in this area aiming to establish the feasibility of the proposed

reactive separation application for life-support and ISRU systems.

References

[1] D. A. Boryta & A. J. Mass, Industrial & Engineering Chemistry Process Design and Development, 10, 4892 (1971) .

[2] C. T. Chou & C. Y. Chen, Separation and Purification Technology 39, 51 (2004).

[3] J. D. Holladay, K. P. Brooks, R. Wegeng, J. Hu, J. Sanders & S. Baird, Catalysis Today, 120, 35 (2007)

[4] T. Q. Phungquach & D. Rouleau, Journal of Applied Chemistry and Biotechnology 26, 527 (1976).

[5] P. Rotaru & S. I. Blejoiu, Journal of Indian Chemical Society 78, 343 (2001).