Unexpected Penetration of CO Molecule into Zeolitic Micropores Almost Plugged by CuCl via π-Complexation of CO-CuCl.

Carbon monoxide (CO) is a key reactant in several Fischer-Tropsch processes, including those used in light olefin and methanol syntheses. However, it is highly toxic and causes serious poisoning of noble metal catalysts. Thus, a solid adsorbent that can selectively capture CO, especially at low concentrations, is required. In this study, zeolite Y-based adsorbents in which Cu(I) ions occupy the supercage cation sites (CuCl/Y) are prepared via solid-state ion exchange. Volumetric adsorption measurements reveal that the Cu(I) ions significantly enhance CO adsorption in the low-pressure range by π-complexation. Furthermore, unexpected molecular sieving behavior, with extremely high CO/CO2 selectivity, is observed when excess CuCl homogeneously covers the zeolite pore structures. Thus, although CO has a larger kinetic diameter, it can penetrate the zeolite supercage while smaller molecules (i.e., Ar and CO2) cannot. Density functional theory calculations reveal that CO molecules can remain adsorbed in pseudoblocked pores by CuCl, thanks to the strong interaction of C 2p and Cu 3d states, resulting in the high CO/CO2 selectivity. One of the prepared adsorbents, CuCl/Y with 50 wt % CuCl, is capable of selectively capturing 3.04 mmol g-1 of CO with a CO/CO2 selectivity of >3370.

Highly selective adsorption of CO over CO2 in a Cu(I)-chelated porous organic polymer.

Cu(I) species were successfully chelated to nitrogen atoms in a nitrogen-rich porous organic polymer (SNW-1) by mixing with a CuCl solution (Scheme 1). Although pristine SNW-1 adsorbs CO2 better than CO, Cu(I)-incorporated SNW-1 (nCu(I)@SNW-1) shows selective CO adsorption over CO2 because of the π-complexation of CO with Cu(I). To the best of our knowledge, this is the first CO/CO2 selectivity observed for POP-based materials. 1.3Cu(I)@SNW-1 exhibits high CO/CO2 selectivity (23) at 1bar and a large CO working capacity (0.6mmol/g) at 0.1-1bar. Moreover, the breakthrough and thermogravimetric experiments show that 1.3Cu(I)@SNW-1 can effectively separate CO from CO2 under dynamic mixture conditions and can be easily regenerated under mild regeneration conditions without heating the column. Furthermore, 1.3Cu(I)@SNW-1 exhibited a good stability under exposure to atmospheric air for 3h or 9h. These results suggest that chelating Cu(I) species to a nitrogen-rich porous organic polymer can be an efficient strategy to separate and recover CO from CO/CO2 mixtures.

Synthesis of CuCl/Boehmite adsorbents that exhibit high CO selectivity in CO/CO2 separation.

We developed nanoporous adsorbent exhibiting unprecedented performance in separation of toxic carbon monoxide (CO). The adsorbent was prepared by dispersing CuCl on mesoporous boehmite via thermal monolayer dispersion route. A key point of the present synthesis is dispersing optimized amount of CuCl on the boehmite at a moderate temperature to maintain the characteristics of the boehmite. We performed a systematic study to reveal that a CuCl/boehmite composite (30wt% CuCl in total) thermally treated at 573K was the best optimized sample for CO separation. The CuCl/boehmite had a high capacity of CO adsorption (1.56mmolg-1) and an exceedingly low capacity of CO2 adsorption (0.13mmolg-1) under 100kPa of each gas at 293K. The CO/CO2 separation factor was 12.4. To the best of our knowledge, this value is the best on record. The achievement of this work is attributed to finding a new type of suitable supporting material: boehmite. The boehmite has a high affinity to CuCl, exhibits excellent dispersion of the CuCl, and achieves a superior CO adsorption capacity. However, it has a weak interaction with CO2. The CuCl/boehmite composite is a promising adsorbent for selective separation of CO from combustion exhaust and industrial off-gas streams.

Power partial-discard strategy to obtain improved performance for simulated moving bed chromatography.

A novel power partial-discard (PPD) strategy was developed as a variant of the partial-discard (PD) operation to further improve the separation performance of the simulated moving bed (SMB) process. The PPD operation varied the flow rates of discard streams by introducing a new variable, the discard amount (DA) as well as varying the reported variable, discard length (DL), while the conventional PD used fixed discard flow rates. The PPD operations showed significantly improved purities in spite of losses in recoveries. Remarkably, the PPD operation could provide more enhanced purity for a given recovery or more enhanced recovery for a given purity than the PD operation. The two variables, DA and DL, in the PPD operation played a key role in achieving the desired purity and recovery. The PPD operations will be useful for attaining high-purity products with reasonable recoveries.

Bio-Diesel Production from Deoxygenation Reaction Over Ce0.6Zr0.4O2 Supported Transition Metal (Ni, Cu, Co, and Mo) Catalysts.

Ce0.6Zr0.4O2 supported transition metal (Me = Ni, Cu, Co, and Mo) catalysts have been investigated to screen for the catalytic activity and selectivity for deoxygenation reaction of oleic acid. Me-Ce0.6Zr0.4O2 catalysts were prepared by a co-precipitation method. Ni-Ce0.6Zr0.4O2 catalyst exhibited much higher oleic acid conversion, selectivity for C9 to C17 compounds, and oxygen removal efficiency than the others. This is mainly ascribed to the presence of free Ni species, synergy effects between Ni and Ce0.6Zr0.4O2, and the highest BET surface area.

Hydrogen molecules trapped in interstitial host channels of alpha-hydroquinone.

Easy come, easy go: Hydroquinone forms a channel structure of cages with hydrogen-bonded hexagons. These may provide an ideal route for the fast inclusion and facile release of hydrogen molecules (see figure), which can lead to reversible hydrogen storage under mild conditions.