This work focuses on the study of a pressure swing adsorption (PSA) process for biogas upgrading using a carbon molecular sieve adsorbent. Adsorption equilibrium and diffusion data of pure components were used to predict the multicomponent behavior. To validate the prediction of multicomponent adsorption at different concentrations, breakthrough curve experiments were performed for a gas mixture at different pressures (0.25, 0.5, 1, and 5 bar). Based on basic information, a model was used to predict the performance of a two-column PSA unit. The mixture used as feed was 60% CH 4 and 40% CO 2 with pressure swings between 5 bar in adsorption mode to 0.1 bar in blowdown. Experimental data demonstrated that the model could describe the PSA performance with good accuracy. We have evaluated the influence of different feed times in the biomethane recovery and purity. Biomethane purity higher than 97.5% with recovery higher than 90% was obtained.

Carbon materials have proven to be a suitable choice for hydrogen storage and, recently, for hydrogen compression. Their developed textural properties, such as large surface area and high microporosity, are essential features for hydrogen adsorption. In this work, we first review recent advances in the physisorption characterization of nanoporous carbon materials. Among them, approaches based on the density functional theory are considered now standard methods for obtaining a reliable assessment of the pore size distribution (PSD) over the whole range from narrow micropores to mesopores. Both a high surface area and ultramicropores (pore width < 0.7 nm) are needed to achieve significant hydrogen adsorption at pressures below 1 MPa and 77 K. However, due to the wide PSD typical of activated carbons, it follows from an extensive literature review that pressures above 3 MP are needed to reach maximum excess uptakes in the range of ca. 7 wt.%. Finally, we present the adsorption–desorption compression technology, allowing hydrogen to be compressed at 70 MPa by cooling/heating cycles between 77 and 298 K, and being an alternative to mechanical compressors. The cyclic, thermally driven hydrogen compression might open a new scenario within the vast field of hydrogen applications.

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Due to their very high porosity and superior textural properties, metal−organic frameworks (MOFs) are promising nanoporous materials for hydrogen storage by cryocompression. Herein, we investigated hydrogen adsorption on four commercial MOFs, namely, MIL53-Al, MOF-5, HKUST-1, and MOF-177, over a temperature range of 77 to 273 K and pressures up to 14 MPa. The modified Dubinin−Astakhov equation was used to fit the experimental adsorption data, and six parameters (m, n max , α, β, P 0 , and V a ) were obtained. We concluded that the parameters n max and V a are related to the micropore volume, while α, β, m, and P 0 are related to the average micropore size. Compared to hydrogen compression in an empty tank, the introduction of MOF-5 enhanced the volumetric hydrogen storage at 77 K and 10 MPa from 31 to 42 kg m −3 . The released H 2 capacities of MOFs from a loading pressure of 10 MPa to a discharge pressure of 0.5 MPa were determined for either isothermal discharge at 77 K or after temperature increase to 160 K. For MOF-5, the amount of usable hydrogen increased up to 10.6 wt % (40.8 mg cm −3 ) by pressure drop (from 10 to 0.5 MPa) and temperature increase (from 77 to 160 K).

Two micro-mesoporous carbons (MMCs): a disordered mesoporous carbon (DMC) and an ordered mesoporous carbon (OMC), synthesized by an easy, low-cost, and green method are proposed as efficient hydrocarbon sieves for the separation of C 6 isomers: n-hexane (nHEX), 2-methylpenthane (2MP) and 2,2-dimethylbutane (22DMB). Their textural characterization reveals a highly interconnected pore network within the DMC, while a reverse hierarchy of ordered mesopores only accessible through narrow micropores is found in the OMC. The pore texture strongly affects their adsorption performance by kinetic and molecular sieving effects; the narrow constrictions in the OMC allow adsorption of nHEX and partially 2MP but not 22DMB, whereas the highly connected pore network of DMC allows adsorption of the three isomers. Multi-component adsorption isotherms calculated from the single-component experimental results by ideal adsorbed solution theory (IAST) demonstrates that the OMC material has a remarkably high selectivity for the adsorption of nHEX and nHEX + 2MP from binary and ternary mixtures, respectively. To the best of the authors' knowledge, such behavior has never been reported so far for carbon materials. Hence, this study shows that tannin-derived MMCs have great potential to be used as an eco-friendly and low-cost alternative for the selective separation of di-branched C 6 isomers.

Single atoms and nanoclusters of Fe, Ni, Co, Cu, and Mn are systematically designed and embedded in a well‐defined C1N1‐type material that has internal cavities of ≈0.6 nm based on four N atoms. These N atoms serve as perfect anchoring points for the nucleation of small nanoclusters of different metal natures through the creation of metal‐nitrogen (TM‐N4) bonds. After pyrolysis at 800 °C, TM@CNx‐type structures are obtained, where TM is the transition metal and x < 1. Fe@CNx and Co@CNx are the most promising for oxygen reduction reaction and hydrogen evolution reaction, respectively, with a Pt‐like performance, and Ni@CNx is the most active for oxygen evolution reaction (OER) with an EOER of 1.59 V versus RHE, far outperforming the commercial IrO2 (EOER = 1.72 V). This systematic and benchmarking study can serve as a basis for the future design of advanced multi‐functional electrocatalysts by modulating and combining the metallic nature of nanoclusters and single atoms.