Kr/Xe SeparatioKr/Xe Separation over Metal Organic Framework Membranes

Technical Report · Wed Dec 11 00:00:00 EST 2019

DOI:https://doi.org/10.2172/1578070· OSTI ID:1578070

Thallapally, Praveen A. ^[1]; Carreon, Moises A ^[2]

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1. Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
2. Colorado School of Mines, Golden, CO (United States)

The central thrust of this project is to develop a novel family of continuous membranes, composed of porous crystalline membranes (mainly metal organic frameworks) which offer the possibility of demonstrating high separation performance for Kr/Xe gas mixtures. The specific objectives of the proposed work are: (1) The development of continuous and reproducible MOF membranes on porous tubular supports displaying high Kr permeabilities and high Kr/Xe separation selectivities.(2) Demonstrating the membrane performance long term stability.(3) Establish the basic structure/separation relationships of MOF membranes in Kr/Xe separations, and (4) Demonstrating that membrane synthesis could be amenable to large scale production. We have demonstrated that porous crystalline molecular sieve membranes including metal organic frameworks, zeolites, and alumino phosphates can effectively separate Kr/Xe gas mixtures ate industrially relevant compositions. Specifically, these three compositions correspond to a different family of microporous crystals, namely zeolites (SAPO-34), metal organic frameworks (ZIF-8) and alumino phosphates (AlPO-18). SAPO-34 membranes displayed the best overall separation performance, while AlPO-18 membranes displayed the highest Kr permeances. The key factors affecting the separation selectivity and permeance of these membranes were identified, and decoupled. The presence of rigid micropores with size lying between Kr and Xe atomic sizes, lower Xe/Kr uptakes (adsorption selectivity), and lower concentration of non-selective pores led to the highest observed Kr/Xe separation selectivities among these three microporous crystals, which corresponded to SAPO-34. The Kr permeances for these three microporous crystalline membrane compositions decreased exponentially with membrane thickness. The best membranes separated Kr/Xe gas mixtures with separation selectivities as high as 45 and Kr permeances ~ as high as 1.2 x 10^-7 mol/m²s Pa. In addition, SAPO-34 and ZIF-8 membranes were effective in separating Air/Xe mixtures. With separation selectivities as high as 30, and air permeances of 2.3 x 10^-7 mol/m²s Pa. Finally, we explore the synthesis in powder form of other potentially suitable porous crystals that if prepared in membrane form could be highly appealing candidates for Kr/Xe and Air/Xe separation. These crystals are porous organic cages which potentially can molecular sieve Kr and air from Xenon based on the unimodal pore sizes lying between the size of the permeant molecules.

• Research Organization: Colorado School of Mines, Golden, CO (United States)
• Sponsoring Organization: USDOE Office of Nuclear Energy (NE)
• DOE Contract Number: NE0008429
• OSTI ID: 1578070
• Report Number(s): DOE-CSM-0008429; TRN: US2000186
• Country of Publication: United States
• Language: English

Related Subjects

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS
Microporous crystalline membranes
metal organic frameworks
Kr/Xe separation
Air/Xe separation