Unravelling ammonia adsorption mechanisms of adsorbents in humid conditions

Abstract

Air purification of ammonia, a toxic industrial chemicals (TICs), by adsorption process on Metal-Organic Framework solids is attracting high scientific and commercial interests. While active carbon based adsorbents required high level of relative humidity for achieving proper performance ammonia capture, zeolite performance degrades in presence of humidity. For MOFs, the presence of humidity has been shown to be MOF dependent, either beneficial or detrimental. It appears that the role of humidity is of key importance and that different ammonia adsorption mechanisms co-exist depending on the material's physico-chemical features. Based on a screening of various microporous adsorbents including carbons, zeolites and MOFs, we show that in the presence of humidity, the ammonia uptake

Synthesis and Shaping Scale-up Study of Functionalized UiO-66 MOF for Ammonia Air Purification Filters

“…At 40% relative humidity, the breakthrough time and ammonia uptakes are enhanced for the commercial adsorbents. A beneficial effect of humidity on NH3 uptake in activated carbon-based adsorbents has already been reported elsewhere 33 , while the mechanism of ammonia uptake in humid conditions has previously been found over a diverse set of adsorbents 34 . In contrast to the activated carbons, the performances in humid conditions remain almost unchanged for the UiO-66-COOH compressed pellet and extrudates.…”

Emerging Porous Materials and Their Composites for NH3 Gas Removal

“…Several porous materials, such as MOFs (UiO-66-NH 2 , UiO-66-COOH, UiO-66-fumarate, Ni-MOF-74, Zn-MOF-74, Fe-BTC, Cu-BTC, and Al-MIL-101-NH 2 ), zeolites (ZSM-5, Beta, and faujasites), and carbon molecular sieves (Carboxen 564 and Carbosieve G 60/80), were studied by Khabzina and Farrusseng for NH 3 capture to unveil the mechanisms of NH 3 adsorption under humid conditions. [68] The NH 3 capacities of the adsorbents were evaluated via breakthrough measurements under a 100 mL min −1 gas stream with 1200 ppm NH 3 in dry or humid (40% RH) conditions. The NH 3 adsorption mechanism in microporous solids can be explained via solubilization, physisorption, and chemisorption.…”

High Ammonia Uptake of a Metal–Organic Framework Adsorbent in a Wide Pressure Range

“…[9][10][11][12][13][14][15][16] Although introducing acidic functional groups into pore interiors could be av alid strategy to enhance NH 3 affinity at low pressures,i th as several limitations.P re-synthetic modification strategies that functionalize aspacer ligand with acidic moieties could result in astructural difference when compared to the use of anonmodified ligand, because acidic functional groups,s uch as OH, COOH, and SO 3 H, are prone to binding to metal ions during the coordination process. [12,14,17] In contrast, postsynthetic introduction of acidic groups to aM OF platform often requires the framework to be chemically stable due to the harsh synthetic conditions,w hich is not typical for MOFs. [18][19][20] Even upon successfully overcoming these synthetic challenges,M OFs functionalized with acidic groups might display lower adsorption performances than those of non-functionalized materials due to their reduced pore volumes.…”