Xe is only produced by cryogenic distillation of air, and its availability is limited by the extremely low abundance. Therefore, Xe recovery after usage is the only way to guarantee sufficient supply and broad application. Herein we demonstrate DD3R zeolite as a benchmark membrane material for CO2/Xe separation. The CO2 permeance after an optimized membrane synthesis is one order magnitude higher than for conventional membranes and is less susceptible to water vapour. The overall membrane performance is dominated by diffusivity selectivity of CO2 over Xe in DD3R zeolite membranes, whereby rigidity of the zeolite structure plays a key role. For relevant anaesthetic composition (<5 % CO2) and condition (humid), CO2 permeance and CO2/Xe selectivity stabilized at 2.0×10−8 mol m−2 s−1 Pa−1 and 67, respectively, during long‐term operation (>320 h). This endows DD3R zeolite membranes great potential for on‐stream CO2 removal from the Xe‐based closed‐circuit anesthesia system. The large cost reduction of up to 4 orders of magnitude by membrane Xe‐recycling (>99+%) allows the use of the precious Xe as anaesthetics gas a viable general option in surgery.

No abstract

This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

The use of an azine-linked covalent organic framework (ACOF-1) as filler in mixed-matrix membranes (MMMs) has been studied for the separation of CO 2 from N 2. To better understand the mechanisms that govern separation in complex composites, MMMs were prepared with different loadings of ACOF-1 and three different polymers as continuous phase: low flux-mid selectivity Matrimid ® , mid flux-high selectivity Polyactive™ and high fluxlow selectivity 6FDA:DAM. The homogeneous distribution of ACOF-1 together with the good adhesion between the ACOF-1 particles and the polymer matrices were confirmed by scanning electron microscopy. In mixed-gas CO 2 /N 2 separation a clear influence of the polymer used was observed on the performance of the composite membranes. While for Matrimid ® and 6FDA:DAM an overall enhancement of the polymer's separation properties could be achieved, in case of Polyactive™ penetration of the more flexible polymer into the COF porosity resulted in a decreased membrane permeability. The best improvement was obtained for Matrimid ®-based MMMs, for which a selectivity increase from 29 to 35, together with an enhancement in permeability from 9.5 to 17.7 Barrer for 16 wt% COF loading, was observed. Our results demonstrate that the combination of the filler-polymeric matrix pair chosen is crucial. For a given filler the polymer performance improvement strongly depends on the polymeric matrix selected, where a good match between the discontinuous and continuous phase, both in the terms of compatibility and gas separation properties, is necessary to optimize membrane performance.

The cobalt-based ZIF-67 has been evaluated for the adsorptive propylene/propane separation in a fixed bed. Characterization techniques and dynamic measurements have been performed over ZIF-67 to evaluate its potential in this defiant process. Cobalt promotes a more rigid framework than zinc in the isostructural ZIF-8. Although the adsorption affinity of ZIF-67 for both hydrocarbons is similar, the lower flexibility of the framework makes ZIF-67 behaving with a clear preference towards propane. This inverse selectivity promotes the enrichment in propylene content upon breakthrough, and may simplify the separation scheme. Therefore, ZIF-67 adsorptive separation is presented as an alternative to energy-demanding distillation.

Separation of propylene/propane is one of the most challenging and energy consuming processes in chemical industry. Propylene demand is increasing and a 99.5 % purity is required for industrial purposes. Adsorption based solutions are the most promising alternative to improve the economical/energetic efficiency of the process. ZIFs combine the desired characteristics from both MOFs and zeolites: tunability and flexibility from the metal organic frameworks, and exceptional thermal and chemical stability from zeolites. In order to enlighten the role of the cation in the sodalite ZIF-8 framework for propane/propylene separation, dynamic breakthrough measurements have been performed over ZIF-8(Zn), ZIF-67(ZIF-8(Co)) and MUV-3 (ZIF-8(Fe)), all materials based on the same linker methylimidazole. Cation substitution has a remarkable influence in the framework flexibility, and, consequently, in SOD-ZIF selectivity for light hydrocarbons. The differences between the crystallographic pore sizes of the material and the molecular dimensions of propane and propylene are so small, that the slightest change in the framework will cause notable advantages/disadvantages in the final application. While cobalt is known to promote a more rigid framework resulting in an adsorption selectivity towards propane, iron presents the inverse effect yielding selectivity to propylene. Zinc has an intermediate effect. A threshold pressure in the isotherm is observed for propylene uptake by ZIF-67 at 273 and 298 K, and only at the lower temperature for ZIF-8. Inlet mixture composition does not highly influence the adsorptive selectivity, although it clearly affects the pure hydrocarbon recovery. Over ZIF-67 breakthrough experiments at 298 K yield a temporary pure propylene flow representing 10-15% of the amount fed. Based on the adsorption selectivity for propane, ZIF-67 is a promising candidate for propylene/propane adsorptive separation.

Xe is only produced by cryogenic distillation of air, and its availability is limited by the extremely low abundance. Therefore,Xerecovery after usage is the only way to guarantee sufficient supply and broad application. Herein we demonstrate DD3R zeolite as ab enchmark membrane material for CO 2 /Xe separation. The CO 2 permeance after an optimized membrane synthesis is one order magnitude higher than for conventional membranes and is less susceptible to water vapour.T he overall membrane performance is dominated by diffusivity selectivity of CO 2 over Xe in DD3R zeolite membranes,whereby rigidity of the zeolite structure playsakey role. Forr elevant anaesthetic composition (< 5% CO 2 )a nd condition (humid), CO 2 permeance and CO 2 /Xe selectivity stabilized at 2.0 10 À8 mol m À2 s À1 Pa À1 and 67, respectively,d uring long-term operation (> 320 h). This endows DD3R zeolite membranes great potential for on-stream CO 2 removal from the Xe-based closed-circuit anesthesia system. The large cost reduction of up to 4o rders of magnitude by membrane Xerecycling (> 99 + %) allows the use of the precious Xe as anaesthetics gas av iable general option in surgery.

A novel anilato-based 3D ultramicroporous MOF is reported, displaying a significant balance of high CO2 separation from CO2:N2 and CO2:CH4 gas mixtures, high thermal stability and high regenerability, a challenge in the separation technology industry.