Zeolite Membranes: Functionalizing of Properties by Tailored Compositions

Hannes Richter,Marcus Weyd,Adrian Simon,Jan-Thomas Kühnert,Christiane Günther,Ingolf Voigt,Alexander Michaelis 한국막학회 2017 멤브레인 Vol.27 No.6

Membrane separation is a technology of low energy consumption. Membranes made of zeolites are of great interest because their fixed and open pores in the size of small molecules inside crystalline structures allow separation processes under harsh conditions. While zeolite NaA (LTA-type) is industrially used for dewatering of organic solvents, its pore size and thermal and hydrothermal stability can be tuned by exchange of framework and extra-framework elements. SOD with pores of only 0.28 nm is of great interest for H 2 - und H 2 O-separation and also can be tuned by ion exchange. Zeolites open the opportunity to create membranes of adapted separation behavior for small molecules in conditions of surrounding technical processes.

Zeolite Membranes: Functionalizing of Properties by Tailored Compositions

Richter, Hannes,Weyd, Marcus,Simon, Adrian,Kuhnert, Jan-Thomas,Gunther, Christiane,Voigt, Ingolf,Michaelis, Alexander The Membrane Society of Korea 2017 멤브레인 Vol.27 No.6

Membrane separation is a technology of low energy consumption. Membranes made of zeolites are of great interest because their fixed and open pores in the size of small molecules inside crystalline structures allow separation processes under harsh conditions. While zeolite NaA (LTA-type) is industrially used for dewatering of organic solvents, its pore size and thermal and hydrothermal stability can be tuned by exchange of framework and extra-framework elements. SOD with pores of only 0.28 nm is of great interest for $H_2$- und $H_2O$-separation and also can be tuned by ion exchange. Zeolites open the opportunity to create membranes of adapted separation behavior for small molecules in conditions of surrounding technical processes. 분리막을 이용한 분리 기술은 에너지 소요가 적다. 제올라이트를 기반으로 제작한 분리막의 경우, 결정 구조 내에 작은 분자 크기의 기공을 갖고 있어 이를 이용하여 가혹한 조건에서도 분리가 가능하기 때문에, 그 관심도가 높다. NaA (LTA 유형의 제올라이트) 제올라이트의 경우, 산업적으로 유기 용매에서 수분을 제거하는 데 많이 사용되는 데, 해당 기공 크기나 열적/수열안정성은 제올라이트 내부나 외부의 원소를 바꿔줌으로써 조절할 수 있다. 더 작은 0.28 nm 크기를 지닌 SOD 유형의 제올라이트의 경우, 수소나 물 분리에 적합하여 그 관심도가 높아지고 있으며, 이 제올라이트 유형 또한, 이온교환과 같은 방법으로 성질을 변경할 수 있다. 제올라이트는 주변 기술 및 공정 조건에 맞게 작은 분자들을 적절하게 분리할 수 있는 분리막을 창출할 수 있다는 장점을 지닌 소재이다.

제올라이트 분리막: 조성 변경을 통한 분리막 성질의 조절

Hannes Richter,Marcus Weyd,Adrian Simon,Jan-Thomas Kühnert,Christiane Günther,Ingolf Voigt,Alexander Michaelis 한국막학회 2017 멤브레인 Vol.27 No.6

분리막을 이용한 분리 기술은 에너지 소요가 적다. 제올라이트를 기반으로 제작한 분리막의 경우, 결정 구조 내에 작은 분자 크기의 기공을 갖고 있어 이를 이용하여 가혹한 조건에서도 분리가 가능하기 때문에, 그 관심도가 높다. NaA (LTA 유형의 제올라이트) 제올라이트의 경우, 산업적으로 유기 용매에서 수분을 제거하는 데 많이 사용되는 데, 해당 기공 크기나 열적/수열안정성은 제올라이트 내부나 외부의 원소를 바꿔줌으로써 조절할 수 있다. 더 작은 0.28 nm 크기를 지닌 SOD 유형의 제올라이트의 경우, 수소나 물 분리에 적합하여 그 관심도가 높아지고 있으며, 이 제올라이트 유형 또한, 이온 교환과 같은 방법으로 성질을 변경할 수 있다. 제올라이트는 주변 기술 및 공정 조건에 맞게 작은 분자들을 적절하게 분리할 수 있는 분리막을 창출할 수 있다는 장점을 지닌 소재이다. Membrane separation is a technology of low energy consumption. Membranes made of zeolites are of great interest because their fixed and open pores in the size of small molecules inside crystalline structures allow separation processes under harsh conditions. While zeolite NaA (LTA-type) is industrially used for dewatering of organic solvents, its pore size and thermal and hydrothermal stability can be tuned by exchange of framework and extra-framework elements. SOD with pores of only 0.28 nm is of great interest for H2- und H2O-separation and also can be tuned by ion exchange. Zeolites open the opportunity to create membranes of adapted separation behavior for small molecules in conditions of surrounding technical processes.

Quantitative elucidation of the elusive role of defects in polycrystalline MFI zeolite membranes on xylene separation performance

Hong, Sungwon,Kim, Dongjae,Richter, Hannes,Moon, Jong-Ho,Choi, Nakwon,Nam, Jaewook,Choi, Jungkyu Elsevier 2019 Journal of membrane science Vol.569 No.-

<P><B>Abstract</B></P> <P>The defect structure in a <I>c</I>-out-of-plane oriented MFI membrane was quantitatively analyzed by processing images obtained by fluorescence confocal optical microscopy (FCOM). The MFI membranes were placed in contact with a dye solution at a fixed concentration (1 mM) for 2, 4, and 8 d and at different concentrations (0.01, 0.1, and 1 mM) for 8 d. This approach led to the identification and understanding of two types of defects (cracks and grain boundary defects). The representative quantitative properties (porosity and tortuosity) relevant to the defects were obtained via the image processing. Furthermore, the estimation of the defect sizes was complemented by the use of a one-dimensional permeation model for the molar flux of the <I>p</I>-/<I>o</I>-xylene components across the <I>c</I>-oriented MFI membrane. Using this combination, we found that although the amount of defects in the whole zeolite membrane was close to ~ 1%, they provided non-selective, facile pathways that accounted for ~ 58% of the total molar flux of faster permeating <I>p</I>-xylene. Surprisingly, despite the lower density (pixel-based area fraction) of cracks, wider cracks (~ 7.8–8.2 nm) accounted for the much higher molar flux of permeation components compared to major, but narrower grain boundary defects (~ 1–2 nm). Indeed, the cracks mainly deteriorated a <I>p</I>-/<I>o</I>-xylene separation performance of the <I>c</I>-oriented MFI membrane. Finally, we found that the crack size increased in the presence of <I>p</I>-xylene so that the molar flux of <I>o</I>-xylene in the binary mixture was significantly increased, thus reducing the <I>p</I>-/<I>o</I>-xylene separation performance. This behavior was ascribed to the flexible MFI zeolite structure after the adsorption of <I>p</I>-xylene.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Defects in a MFI zeolite membrane were quantitatively analyzed by a FCOM technique. </LI> <LI> Two types of defects (cracks and grain boundary defects) were investigated. </LI> <LI> The defects with coverage of less than 1% significantly reduced membrane performance. </LI> <LI> Fewer but wider cracks had a stronger influence on the final membrane performance. </LI> <LI> Structural transformation of the MFI zeolite due to <I>p</I>-xylene opened defect spaces. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Chabazite-Type Zeolite Membranes for Effective CO₂ Separation: The Role of Hydrophobicity and Defect Structure

Lee, Minseong,Hong, Sungwon,Kim, Dongjae,Kim, Eunjoo,Lim, Kyunghwan,Jung, Jae Chil,Richter, Hannes,Moon, Jong-Ho,Choi, Nakwon,Nam, Jaewook,Choi, Jungkyu American Chemical Society 2019 ACS APPLIED MATERIALS & INTERFACES Vol.11 No.4

<P>Chabazite (CHA)-type zeolites are promising for the separation of CO<SUB>2</SUB> from larger molecules, such as N<SUB>2</SUB> (relevant to postcombustion carbon capture) and CH<SUB>4</SUB> (relevant to natural gas/biogas upgrading). In particular, the pore size of CHA zeolites (0.37 × 0.42 nm<SUP>2</SUP>) can recognize slight molecular size differences between CO<SUB>2</SUB> (0.33 nm) and the larger N<SUB>2</SUB> (0.364 nm) or CH<SUB>4</SUB> (0.38 nm) molecules, thus allowing separation in favor of CO<SUB>2</SUB> through CHA membranes. Furthermore, the siliceous constituents in the CHA zeolite can reduce the adsorption capacity toward the smaller H<SUB>2</SUB>O molecule (0.265 nm) and, thus, the H<SUB>2</SUB>O permeation rate. This is highly desirable for securing good molecular sieving ability with CO<SUB>2</SUB> permselectivity in the presence of H<SUB>2</SUB>O vapor. Indeed, a siliceous CHA film obtained with a nominal Si/Al ratio of 100 (CHA_100) showed high CO<SUB>2</SUB>/N<SUB>2</SUB> and CO<SUB>2</SUB>/CH<SUB>4</SUB> separation performance, especially in the presence of H<SUB>2</SUB>O vapor; ∼13.4 CO<SUB>2</SUB>/N<SUB>2</SUB> and ∼37 CO<SUB>2</SUB>/CH<SUB>4</SUB> separation factors (SFs) at 30 °C. These SFs were higher than the corresponding values (∼5.2 CO<SUB>2</SUB>/CH<SUB>4</SUB> SFs and ∼31 CO<SUB>2</SUB>/CH<SUB>4</SUB> SFs) under dry conditions; such improvement could be ascribed to defect blocking by physisorbed water molecules. Finally, the contribution of molecular transport through zeolitic and nonzeolitic parts was quantitatively analyzed by combining information extracted from image processing of fluorescence confocal optical microscopy images with a one-dimensional permeation model. It appears that ∼19 and ∼20% of the total CO<SUB>2</SUB> permeance for CHA_100 were reduced due to transport inhibition by the physisorbed water molecules on the membrane surface and defect, respectively.</P> [FIG OMISSION]</BR>