A zeolitic imidazolate framework two-layered membrane approach is simulated and experimentally validated to improve the pre-combustion gas separation.

Stable molecular hydrogen isotopes, D 2 and T 2 , are both scarce and essential in several energy, industrial and large-scale, fundamental research applications. Due to the chemical similarity of these isotopes, their extraction and purification from hydrogen has relied for decades on expensive and energy-demanding processes. However, factoring in the phenomenon of quantum sieving could provide a new route for these separations. In this work, we have explored how to separate hydrogen isotopes by adsorption taking these quantum effects into account. To this end, we have conducted adsorption measurements to test our deuterium model, and performed a widespread computational screening over 210 pure-silica zeolites for D 2 :H 2 and T 2 :H 2 separations. Based on low-coverage adsorption properties, a reduced set of zeolites have been singled out and their performance in terms of adsorption capacity, selectivity and dynamic behavior have been assessed. Overall, the BCT-type zeolite clearly stands out for highly selective separations of both D 2 and T 2 over H 2 , achieving the highest reported selectivities at cryogenic temperatures. We also identified other interesting zeolites for the separation of hydrogen isotopes that offer an alternative way to tackle similar isotopic separations by an aimed selection or design of porous materials.

Carbon dioxide release has become an important global issue due to the significant and continuous rise in atmospheric CO concentrations and the depletion of carbon-based energy resources. Plasmolysis is a very energy-efficient process for reintroducing CO into energy and chemical cycles by converting CO into CO and O utilizing renewable electricity. The bottleneck of the process is that CO remains mixed with O and residual CO. Therefore, efficient gas separation and recuperation are essential for obtaining pure CO, which, via water gas shift and Fischer-Tropsch reactions, can lead to the production of CO-neutral fuels. The idea behind this work is to provide a separation mechanism based on zeolites to optimize the separation of carbon dioxide, carbon monoxide, and oxygen under mild operational conditions. To achieve this goal, we performed a thorough screening of available zeolites based on topology and adsorptive properties using molecular simulation and ideal adsorption solution theory. FAU, BRE, and MTW are identified as suitable topologies for these separation processes. FAU can be used for the separation of carbon dioxide from carbon monoxide and oxygen and BRE or MTW for the separation of carbon monoxide from oxygen. These results are reinforced by pressure swing adsorption simulations at room temperature combining adsorption columns with pure silica FAU zeolite and zeolite BRE at a Si/Al ratio of 3. These zeolites have the added advantage of being commercially available.

This work is aimed at optimizing a Fischer-Tropsch Gas To Liquid (GTL) process by recycling compounds of the expelled gas mixture using zeolites for the separation. To that end, we have performed a computational study on four structures widely used in industry. A range of Si/Al ratios have been explored and the effects of their distribution assessed. The ability of the considered force fields and molecular models to reproduce experimental results has been widely proved in previously reported studies. Since this tail gas is formed by a five-component mixture, namely carbon dioxide, methane, carbon monoxide, nitrogen and hydrogen, molecular simulations present clear advantages over experiments. In addition, the viability of the Ideal Adsorption Solution Theory (IAST) has been evaluated to easily handle further separation steps. On the basis of the obtained results, we provide a separation scheme to perform sequentially the separation of CO2, CH4, CO, N2 and H2.

Due to their high cation-exchange ability as well as to their molecular sieve properties, natural zeolites are widely used in industry. In this work, we used molecular simulation to comprehensively explore at the microscopic scale the hydration process in aluminum-rich (Si/Al ratio = 1) LTA-type zeolites with different compositions of charge balancing sodium and calcium cations. The results reveal the nature of the cation to be more influential than the density of the cations, which is detectable in both the adsorption isotherms, and the energetic and structural descriptions of system interactions. The higher affinity of water to calcium cations in relation to sodium cations leads to a more hydrophilic character of Ca-containing zeolites, and the water clustering proceeds differently during the adsorption process. However, the extra-framework cations negligibly influence on the hydrogen-bonded network of the adsorbed water at saturation, when a dense phase is formed, as well as on cation-water interactions.