High-Performance Adsorbent for Ethane/Ethylene Separation Selected through the Computational Screening of Aluminum-Based Metal–Organic Frameworks

The development of a high-performance ethane (C2H6)-selective adsorbent for the separation of ethane/ethylene (C2H6/C2H4) gas mixtures has been investigated for high-efficiency adsorption-based gas separation. Herein, we investigated Al-based metal–organic frameworks (MOFs) to identify an efficient C2H6-selective adsorbent (CAU-11), supported by a computational simulation study. CAU-11 exhibited numerous advantageous properties (such as low material cost, structural robustness, high reaction yield, and high C2H6/C2H4 selectivity) compared to other Al-based MOFs, indicating immense potential as a C2H6-selective adsorbent. CAU-11 exhibited preferential C2H6 adsorption in single-component gas adsorption experiments, and its predicted ideal adsorption solution theory selectivity of C2H6/C2H4 was over 2.1, consistent with the simulation analysis. Dynamic breakthrough experiments using representative compositions of the C2H6/C2H4 gas mixture confirmed the excellent separation ability of CAU-11; it produced high-purity C2H4 (>99.95%) with productivity values of 0.79 and 2.02 mol L–1 while repeating the cyclic experiment with 1:1 and 1:15 v/v C2H6/C2H4 gas mixtures, respectively, at 298 K and 1 bar. The high C2H6/C2H4 separation ability of CAU-11 could be attributed to its non-polar pore environment and optimum pore dimensions which strengthen the interaction of its pores (via C–H···π interactions) with C2H6 to a greater extent than with C2H4

Propylene/Nitrogen Separation in a By-Stream of the Polypropylene Production: From Pilot Test and Model Validation to Industrial Scale Process Design and Optimization

Two industrial-scale pressure swing adsorption (PSA) processes were designed and optimized by simulations: recovery of only nitrogen and recovery of both nitrogen and propylene from a polypropylene manufacture purge gas stream. MIL-100­(Fe) granulates were used as adsorbent. The mathematical model employed in the simulations was verified by a PSA experiment. The effect of several operating parameters on the performance of the proposed PSA processes was investigated. For the nitrogen recovery, a 5-step 2-column PSA process produced a nitrogen stream of 95.4% purity with recovery of 85.2%, productivity of 6.0 mol N₂/kg adsorbent/h, and power consumption of 156 Wh/kgN₂. Nitrogen and propylene with 96.2% and 97.6% purity, respectively, were obtained from the 6-step 3-column nitrogen and propylene recovery PSA process. The nitrogen and propylene recoveries obtained are 98.4% and 91.0%, respectively. The nitrogen and propylene productivities were estimated as 4.61 and 1.83 mol product/kg adsorbent/h and the power consumption as 383 Wh/kgN₂

In Situ Energy-Dispersive X‑ray Diffraction for the Synthesis Optimization and Scale-up of the Porous Zirconium Terephthalate UiO-66

The synthesis optimization and scale-up of the benchmarked microporous zirconium terephthalate UiO-66­(Zr) were investigated by evaluating the impact of several parameters (zirconium precursors, acidic conditions, addition of water, and temperature) over the kinetics of crystallization by time-resolved in situ energy-dispersive X-ray diffraction. Both the addition of hydrochloric acid and water were found to speed up the reaction. The use of the less acidic ZrOCl₂·8H₂O as the precursor seemed to be a suitable alternative to ZrCl₄·<i>x</i>H₂O, avoiding possible reproducibility issues as a consequence of the high hygroscopic character of ZrCl₄. ZrOCl₂·8H₂O allowed the formation of smaller good quality UiO-66­(Zr) submicronic particles, paving the way for their use within the nanotechnology domain, in addition to higher reaction yields, which makes this synthesis route suitable for the preparation of UiO-66­(Zr) at a larger scale. In a final step, UiO-66­(Zr) was prepared using conventional reflux conditions at the 0.5 kg scale, leading to a rather high space-time yield of 490 kg m^–3 day^–1, while keeping physicochemical properties similar to those obtained from smaller scale solvothermally prepared batches

Coadsorption of <i>n</i>‑Hexane and Benzene Vapors onto the Chromium Terephthalate-Based Porous Material MIL-101(Cr) An Experimental and Computational Study

The adsorption of <i>n</i>-hexane–benzene mixture onto a chromium terephtalate-based porous material (MIL-101­(Cr)) has been studied experimentally and theoretically. The adsorption isotherms of the single components show that MIL-101­(Cr) has a better affinity for benzene than for <i>n</i>-hexane. This is in good agreement with the enthalpies of adsorption determined at low coverage. Values of −68 kJ·mol^–1 and −61 kJ·mol^–1 were found for benzene and <i>n</i>-hexane, respectively. These are consistent with the simulated enthalpies of adsorption and also with the benzene/<i>n</i>-hexane selectivities which range between 2 and 3 depending on the equilibrium pressure. The saturation plateau obtained with <i>n</i>-hexane is 30% lower than that obtained with the adsorption of benzene onto MIL-101­(Cr). In the case of the mixture of <i>n</i>-hexane–benzene, the saturation plateau is located between those obtained after adsorption of the single components. This is an indication that the coadsorption of <i>n</i>-hexane and benzene does not occur at the expense of one component of the mixture. However, the kinetics of adsorption of the mixture shows that benzene is adsorbed preferentially at low coverage. This is consistent with the chromatographic separation of <i>n</i>-hexane–benzene mixture by MIL-101­(Cr)

Syngas Purification by Porous Amino-Functionalized Titanium Terephthalate MIL-125

The adsorption equilibrium of carbon dioxide (CO₂), carbon monoxide (CO), nitrogen (N₂), methane (CH₄), and hydrogen (H₂) was studied at 303, 323, and 343 K and pressures up to 7 bar in titanium-based metal–organic framework (MOF) granulates, amino-functionalized titanium terephthalate MIL-125­(Ti)_NH₂. The affinity of the different adsorbates toward the adsorbent presented the following order: CO₂ > CH₄ > CO > N₂ > H₂, from the most adsorbed to the least adsorbed component. Subsequently, adsorption kinetics and multicomponent adsorption equilibrium were studied by means of single, binary, and ternary breakthrough curves at 323 K and 4.5 bar with different feed mixtures. Both studies are complementary and aim the syngas purification for two different applications, hydrogen production and H₂/CO composition adjustment, to be used as feed in the Fischer–Tropsch processes. The isosteric heats were calculated from the adsorption equilibrium isotherms and are 21.9 kJ mol^–1 for CO₂, 14.6 kJ mol^–1 for CH₄, 13.4 kJ mol^–1 for CO, and 11.7 kJ mol^–1 for N₂. In the overall pressure and temperature range, the adsorption equilibrium isotherms were well-regressed against the Langmuir model. The multicomponent breakthrough experimental results allowed for validation of the adsorption equilibrium predicted by the multicomponent extension of the Langmuir isotherm and validation of the fixed-bed mathematical model. To conclude, two pressure swing adsorption (PSA) cycles were designed and performed experimentally, one for hydrogen purification from a 30/70% CO₂/H₂ mixture (hydrogen purity was 100% with a recovery of 23.5%) and a second PSA cycle to obtain a light product with a H₂/CO ratio between 2.2 and 2.4 to feed to Fischer–Tropsch processes. The experimental cycle produced a light stream with a H₂/CO ratio of 2.3 and a CO₂-enriched stream with 86.6% purity as a heavy product. The CO₂ recovery was 93.5%