Control of zeolite pore interior for chemoselective alkyne/olefin separations

Abstract

The efficient removal of alkyne impurities for the production of polymer-grade lower olefins remains an important and challenging goal for many industries. We report a strategy to control the pore interior of faujasite (FAU) zeolites by the confinement of isolated open nickel(II) sites in their six-membered rings. Under ambient conditions, Ni@FAU showed remarkable adsorption of alkynes and efficient separations of acetylene/ethylene, propyne/propylene, and butyne/1,3-butadiene mixtures, with unprecedented dynamic separation selectivities of 100, 92, and 83, respectively. In situ neutron diffraction and inelastic neutron scattering revealed that confined nickel(II) sites enabled chemoselective and reversible binding to acetylene through the formation of metastable [Ni(II)(C2H2)3] complexes. Control of the chemistry of pore interiors of easily scalable zeolites has unlocked their potential in challenging industrial separations.

Metal@Zeolite Hybrid Materials for Catalysis

“…The accurate identification of the metal location and the metal-zeolite interface structure requires combining the multiple advanced characterization techniques including electronic tomographic microscopy, 17 , 85 , 90 , 115 − 117 two-dimensional solid-state NMR spectroscopy, 118 as well as the in situ spectroscopic characterizations such as Raman and IR with well-designed atmosphere. 119 …”

Efficient Trapping of Trace Acetylene from Ethylene in an Ultramicroporous Metal–Organic Framework: Synergistic Effect of High‐Density Open Metal and Electronegative Sites

“…The host–guest interactions were further investigated by in situ FTIR to provide more evidence on the synergistic effect of OMSs and electronegative sites. Compared to the FTIR spectrum of activated Ni 3 (pzdc) 2 (7 Hade) 2 , physisorbed C 2 H 2 on Ni site can be clearly observed at 3150 to 3240 cm −1 in the FTIR spectrum of C 2 H 2 ‐loaded Ni 3 (pzdc) 2 (7 Hade) 2 (Figure d; Figure S20), and the weak interactions between C 2 H 2 and ligand N lead to the red shift of γ s (N‐H) band from 3400 to 3382 cm −1 . In addition, the peak of γ(O‐H) at 3680 cm −1 has widened after C 2 H 2 loading, indicating more O‐H interactions after C 2 H 2 adsorption.…”

Fine‐Tuning Pore Dimension in Hybrid Ultramicroporous Materials Boosting Simultaneous Trapping of Trace Alkynes from Alkenes

“…[ 3 ] However, conventional adsorbents, such as zeolites and ultra‐microporous carbon usually display low or moderate separation factors, and are rarely used for alkyne/alkene separation. [ 4 ] Hybrid ultramicroporous materials (HUMs), a sub‐class of metal‐organic frameworks (MOFs) or porous coordination polymers (PCPs), are novel customizable porous materials consisting of square lattice layers (sql) of organic ligands and metal nodes, pillared by electronegative anions to generate a 3D coordination network as reported by Prof. Zaworotko and Kitagawa. [ 2e,5 ] Benefited from the fine‐tuned pore size and pore chemistry involving high‐density electronegative anions as potential binding sites for gas molecules, HUMs have exhibited glaring merits in hydrocarbon separations, such as C 2 H 2 /C 2 H 4 , C 3 H 4 /C 3 H 6 , and C4 isomers, via strong host–guest, guest–guest interactions, and molecule sieving effect.…”