Green Hydrogen Separation from Natural Gas Grids by Adsorption Processes with MOFs

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Kinetic separation of green hydrogen from natural gas grids by using vacuum pressure swing adsorption

Publication . Zafanelli, Lucas F.A.S.; Henrique, Adriano; Aly, Ezzeldin; Rodrigues, Alírio; Mouchaham, Georges; Silva, José A.C.

Transitioning to renewable energy sources is crucial to mitigating climate change. In this scenario, green hydrogen (GH) is considered a promising energy carrier due to its high calorific value, versatility in applications, clean combustion, and potential for local generation in abundance. As interest in GH grows, developing its distribution chain becomes crucial in facilitating its widespread use. The co-transporting GH into existing natural gas grids (NGG) emerges as a viable alternative, eliminating the need for significant infrastructure investments. However, upon blending GH into the NGG, it becomes essential to de-blend and purify it to a high degree to enable, for instance, fuel cell applications (H2 > 99,97%). One problem concerning the separation and purification of GH from NGG relates to the H2 feed concentration (< 20%), which differs significantly from conventional H2 purification processes (> 70%). Moreover, the high CH4 concentration and its relatively weak adsorption affinity on commonly used adsorbents further complicate achieving high-purity H2 and high recovery rates through conventional approaches. In this work, we report a novel conceptual vacuum pressure swing adsorption (VPSA) process to separate H2 from CH4 by exploiting the kinetic selectivity of H2 over CH4 on CMS-3K-172.

2024Conference object

Open access

Vacuum pressure swing adsorption process using binder-free K(23)Y zeolite for post-combustion CO2 capture

Publication . Aly, Ezzeldin; Zafanelli, Lucas F.A.S.; Henrique, Adriano; Gleichmann, Kristin; Rodrigues, Alírio; Freitas, Francisco A. da Silva; Silva, José A.C.

This study presents the development of a Vacuum Pressure Swing Adsorption (VPSA) process utilizing binder- free K(23)Y zeolite for post-combustion CO2 capture. The ion-exchanged K(23)Y zeolite, characterized by a high CO2 selectivity of 97 over N2 at 10 kPa and an adsorption capacity exceeding 7 mol⋅kg− 1 350 kPa at 306 K, was evaluated under various operational conditions to optimize the VPSA process. Experimental and simulated breakthrough analyses provided essential data for adsorption equilibrium and sorption kinetics, which were modelled using Aspen Adsorption software. Optimization of key cycle steps, including pressurization, adsorption, blowdown, and evacuation, revealed that Light Product Pressurization significantly enhances process performance. Parametric studies demonstrated that reducing intermediate pressure from 0.2 bar to 0.07 bar increased CO2 purity from 84 % to 93 %, though it decreased recovery from around 99 % to 78 %, revealing a key trade-off. Similarly, extending adsorption time beyond 86 s enabled CO2 purity to exceed 90 %, though recovery decreased slightly. Under optimal conditions, the VPSA process achieved a CO2 purity and recovery of ~90 % and productivity of 0.367 molCO2⋅m− 3ads⋅s− 1 , with specific energy consumption of 144 kWh per ton of CO2 captured. The study demonstrates the viability of a simple 4-step VPSA configuration with binder-free K(23)Y, offering competitive performance and low energy consumption.

2025Journal article

Restricted access

Separation of CO2/N2 in Ion-Exchange binder-free beads of zeolite NaY for Post-Combustion CO2 capture

Publication . Aly, Ezzeldin; Zafanelli, Lucas F.A.S.; Henrique, Adriano; Gleichmann, Kristin; Rodrigues, Alírio; Freitas, Francisco A. da Silva; Silva, José A.C.

Ion-exchange on bare commercial zeolites can offer improved adsorption processes. In the context of CO2/N2 separation for post-combustion CO2 capture (PCC), here, we report, the effect of ion-exchange on commercial binder-free NaY zeolite with alkali (K+) and alkaline earth (Ca2+) metal cations, achieving exchange levels of 23 %, 58 %, and 95 % for K+ and 56 % and 71 % for Ca2+. Adsorption isotherms of CO2 and N2 were measured over a temperature range of 306–344 K and pressures up to 350 kPa. At low pressures, the CO2 adsorption capacity increases as Na+ ions are exchanged to a higher level of K+, while a reverse trend is observed for Ca2+ exchange. At 25 kPa and 306 K, the CO2 loading (mol∙kg−1) follows the order 2.01-Ca(71)Y < 2.63-Ca(56)Y < 4.05-NaY < 4.29-K(23)Y < 4.59-K(58)Y < 4.72-K(95)Y. The selectivities of CO2 (15 %)/N2 (85 %) at 306 K and 101.3 kPa range from 52 for Ca(71)Y to 101 for K(23)Y, compared to 89 in the bare NaY zeolite. The working capacities for the most promising exchanged sample (K(23)Y) exhibit superior values of 4.51, 2.98, and 2.41 mol∙kg−1 considering regeneration pressures of 3, 10, and 15 kPa, relative to a feed pressure of 101.3 kPa, respectively. Dynamic simulations were conducted using the Aspen Adsorption package to accurately predict both single- and binary-component breakthrough curves.

2024Journal article

Open access

Green hydrogen recovery from natural gas grids by adsorption process

Publication . Zafanelli, Lucas F.A.S.; Aly, Ezzeldin; Henrique, Adriano; Rodrigues, Alírio; Silva, José A.C.

In this work, the binder-free zeolite 13X was tested to purify green hydrogen injected into natural gas grids. Green hydrogen can be a key factor in meeting global energy demand while contributing to climate goals. In this way, breakthrough curve experiments were performed to assess the equilibrium and kinetic adsorption for H2 and CH4 in binder- free zeolite 13X. This work covers the lack of adsorption data and multicomponent breakthrough curves of H2/CH4 at low temperatures (until 195 K) which were not available in the literature. The equilibrium data were modeled by using the dual-site Langmuir isotherm model and the multicomponent breakthrough curves were simulated using a mathematical model implemented in MATLAB. Performance parameters based on equilibrium data were discussed. Overall, binder-free zeolite 13X has great potential to separate H2 from CH4 based on equilibrium (higher capacity for CH4 with fast diffusion of both gases).

2023Conference object

Open access

CO2 capture in 3D-printed carbon monolith by adsorption

Publication . Henrique, Adriano; Zafanelli, Lucas F.A.S.; Aly, Ezzeldin; Rodrigues, Alírio; Silva, José A.C.

Hierarchically structured 3D-printed porous carbon monoliths were evaluated for their applicability in CO2 capture from post-combustion streams. Two materials of the same macroscopic shape were studied, which varied in the micro- and mesoporosity by changing the final CO2 activation time: activated at 1133 K for 6 h (M1) and 12 h (M2), respectively. Fixed bed breakthrough experiments with single (CO2 and N2) and multicomponent (CO2/N2: 15/85 v.%) feed mixtures were conducted, covering the temperature range of 313 - 373 K. Results demonstrated that both materials enable a thermodynamic-based separation of these components due to their strong interaction with CO2. While a higher burn-off during monolith activation enhances its adsorption capacity by increasing the surface area, the highest selectivities were obtained in M1, 18, against 10 in M2. The dual-site and standard Langmuir isotherm models conveniently fitted the adsorption equilibrium data, and a dynamic adsorption model suitably predicted the breakthrough curves.

2023Conference object

Open access