Olefins-selective asymmetric carbon molecular sieve hollow fiber membranes for hybrid membrane-distillation processes for olefin/paraffin separations

Physical aging in carbon molecular sieve membranes

“…This observation may explain the divergence of some measured values caused by changing testing protocols between different research groups. For example, in our group, a 10-20 GPU ethylene permeance was reported for 6FDA/BPDA-DAM CMS produced by 550°C/ argon purge pyrolysis in our tests with the long term evacuation protocol [11], while the intrinsic values right after pyrolysis, prior to dramatic aging under vacuum would be much higher.…”

“…Details of membrane fabrication are provided in previous publications [3,[11][12][13]; however, general procedures and a few key issues are pointed out, as follows for convenience. The precursor dense film membranes were prepared via a solution casting method.…”

“…The precursor membranes were pyrolyzed in a quartz tube heated in a three-zone furnace. The pyrolysis protocols have been discussed previously [3,[11][12][13]. For dense film membranes, a slotted quartz plate was used as the membrane support; for hollow fibers, stainless steel wire mesh was used as the support for hollow fiber membranes.…”

“…Considerable research has also focused on tailoring the membrane molecular sieve properties for higher permeability and selectivity [7,[11][12][13][14][15][16][17][18][19][20][21]; however, relatively little work has focused on the stability of CMS materials [22][23][24][25][26]. This lack of attention is partially due to the rigid nature of CMS membranes and their enhanced chemical and thermal resistance compared to polymeric materials.…”

Imidazolium-based ionic liquids with cyano groups for the selective absorption of ethane and ethylene

“…The search for alternative separation processes led to the investigation of ionic liquids as new separating agents for olefin/paraffin gas separation, serving as absorbents or alternatively as solvents for the chemical complexation of olefins with silver or copper salts [3,4], ion exchanging resins [2], adsorption on high surface-area SiO 2 [5], on alumina [6], on zeolites [7] and molecular sieves [8], or on metallic organic frameworks [9], and the use of several types of membranes [10]. The use of absorbent agents can be less energy demanding but it is often technologically more challenging as the absorbent needs to be efficiently separated and then recycled with reasonable purity.…”