Evaluation of Sorbents for Acetylene Separation in Atmosphere Revitalization Loop Closure

Abstract

State-of-the-art carbon dioxide reduction technology uses a Sabatier reactor to recover water from metabolic carbon dioxide. In order to maximize oxygen loop closure, a byproduct of the system, methane, must be reduced to recover hydrogen. NASA is currently exploring a microwave plasma methane pyrolysis system for this purpose. The resulting product stream of this technology includes unreacted methane, product hydrogen, and acetylene. The hydrogen and the small amount of unreacted methane resulting from the pyrolysis process can be returned to the Sabatier reactor thereby substantially improving the overall efficiency of the system. However, the acetylene is a waste product that must be removed from the pyrolysis product. Two materials have been identified as potential sorbents for acetylene removal: zeolite 4A, a commonly available commercial sorbent, and HKUST-1, a newly developed microporous metal. This paper provides an explanation of the rationale behind acetylene removal and the results of separation testing with both materials.

Evaluation of Iron-Based Metal–Organic Framework Activation Temperatures in Acetylene Adsorption

“…Unfortunately, acetylene is a known poison for Sabatier-type catalysts due to the strong interaction and reactivity of acetylene toward the catalysts . As a result, there has been a strong interest in finding viable methods for selectively removing the acetylene byproduct . Given the stringent requirements of space travel on system management, any viable system for chemical separation must have minimal size and energy input requirements .…”

Evaluation of Iron-Based Metal-Organic Framework Activation Temperature in Acetylene Adsorption

“…10 Because of that, there has been a strong interest in finding methods of removing acetylene from the hydrogen streams. 11 In particular, due to the limitations of space exploration, any system that would separate out the acetylene should have minimal equipment requirements or energy inputs. 11 This requires a process that can operate at or near room temperature and at the relatively low pressure of the PPA effluent (50-100 torr).…”

“…11 In particular, due to the limitations of space exploration, any system that would separate out the acetylene should have minimal equipment requirements or energy inputs. 11 This requires a process that can operate at or near room temperature and at the relatively low pressure of the PPA effluent (50-100 torr). 11 These process limitations result in a limited number of options for the efficient separation of acetylene from hydrogen.…”

“…11 This requires a process that can operate at or near room temperature and at the relatively low pressure of the PPA effluent (50-100 torr). 11 These process limitations result in a limited number of options for the efficient separation of acetylene from hydrogen. One of the main systems of interest is the use of sorbent based approaches.…”

“…One of the main systems of interest is the use of sorbent based approaches. 11 Amongst all classes of sorbents, metal-organic frameworks (MOFs), materials produced from the combination of organic linkers and metal oxo clusters, are quickly becoming of great interest for this process. [12][13][14] This is because of the structural features of MOFs, such as their high surface areas, [15][16] and the presence of open metal sites.…”