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- Fixed bed adsorption of CO2, CH4, and N2 and their mixtures in potassium-exchanged binder-free beads of Y zeolitePublication . Aly, Ezzeldin; Zafanelli, Lucas F.A.S.; Henrique, Adriano; Pires, Marcella Golini; Rodrigues, Alírio; Gleichmann, Kristin; Silva, José A.C.; Golini Pires, MarcellaThe adsorption of carbon dioxide (CO2), methane (CH4), and nitrogen (N2) has been studied on potassium-exchanged (95%) binder-free beads of Y zeolite through single, binary, and ternary fixed bed breakthrough experiments, covering the temperature range between 313 and 423 K and a pressure of up to 350 kPa. At 313 K and 350 kPa, the single-component data obtained showed that the amounts adsorbed of CO2, CH4, and N2 are around 6.42, 1.45, and 0.671 mol kg-1, respectively. The binary experiments CO2/N2 carried out under typical post-combustion conditions show a selectivity of CO2 over N2 around 104. The ternary experiments resulted in the selectivities of CO2 over CH4 and N2 around 19 and 45, respectively. The adsorption equilibrium data have been modeled by the dual-site Langmuir model, and the breakthrough experiments were numerically simulated with a suitable dynamic fixed bed adsorption model. The model predicts with good accuracy the systematic behavior of all breakthrough experiments. The results shown in the present work prove that the potassium-exchanged binder-free beads of Y zeolite enhance the amount adsorbed of CO2 at low partial pressure over other alkali metal-exchanged faujasites and efficiently separate it from binary (CO2/N2) and ternary (CO2/CH4/N2) mixtures by fixed bed adsorption.
- Post-combustion capture of CO2 in potassium-exchanged binder-free beads of Y zeolitePublication . Aly, Ezzeldin; Zafanelli, Lucas F.A.S.; Henrique, Adriano; Freitas, Francisco A. da Silva; Rodrigues, Alírio; Silva, José A.C.The generation of carbon dioxide is inherent in the combustion of fossil fuels, and the efficient capture of CO2 from industrial operations is regarded as an important strategy to achieve a significant reduction in atmospheric CO2 levels. Adsorption processes are promising capture technologies as they can use specific adsorbents by acting in the limit as molecular sieves to separate CO2 from other flue gas constituents. Experimental and theoretical studies concerning the adsorption of CO2 and N2 and their mixtures in potassium-exchanged Y zeolite (KY) are lacking information in the literature. Accordingly, this work aims to investigate by a series of fixed-bed adsorption breakthrough experiments the adsorption of single and binary mixtures (under compositions typical of post-combustion) of CO2/N2 in binder-free beads of KY zeolite, at 313, 373, and 423 K and total pressures up to 350 K. The single and multi-component breakthrough apparatus used in this work is shown in Figure 1. The dynamic equilibrium loading is calculated by integrating the molar flow profiles of the breakthrough curves, as explained in previous works [1]. The adsorption equilibrium data was then modelled by the extended dual-site Langmuir model, and the breakthrough curves were numerically simulated using ASPEN ADSORPTION. At 313 K and 350 kPa, the single-component data obtained showed that the amount adsorbed of CO2, and N2 is around 6.42 and 0.671 mol.kg-1, respectively. The binary experiments CO2/N2 carried out under typical post-combustion conditions, show a selectivity of CO2 over N2 around 104. Overall the numerical simulations performed on ASPEN ASDSORPTION provided results with decent accuracy and the model can predict the systematic behaviour of the breakthrough experiments as well as the dynamics of the fixed bed adsorption system. The results shown in the present work proves that potassium-exchanged binder-free beads of Y zeolite is a promising adsorbent that can efficiently separate CO2 from post-combustion streams by fixed bed adsorption.
- Vacuum pressure swing adsorption process using binder-free K(23)Y zeolite for post-combustion CO2 capturePublication . 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.
- Sorption of CO2 and N2 in binder-free zeolite KY studied by a chromatographic methodPublication . Aly, Ezzeldin; Silva, José A.C.In the last few decades of industrialization, there has been a significant increase in the concentration of carbon dioxide (CO2) and other greenhouse gases in the atmosphere, which has a visible harmful effect on the environment we live in today. Regarding that, many organizations around the world have invested heavily in research activities towards CO2 capture and storage. Adsorption processes are characterized with low energy costs and can involve low investment in terms of both initial cost and space required. In this work, the adsorption equilibrium of CO2 and N2 in commercial binder-free beads of KY zeolite has been studied between 313 K and 423 K and pressure up to 3.5 bar using a gas chromatographic technique (frontal chromatography/breakthrough technique). At the temperature of 313 K, the results showed that the amount adsorbed of CO2 in binder-free KY is up to 6.42 mol.kg-1 with heats of adsorption of 41.4 kJ.mol-1. The amount adsorbed of N2 at similar conditions is much less compared to CO2 where it doesn’t exceed 0.68 mol.kg-1 being the heat of adsorption around 21.1 kJ.mol-1. The adsorption equilibrium data were fitted with the Langmuir and the dual-site Langmuir (DSL) models and compared with other Y zeolites modified by cation exchange available in literature. The comparisons showed that the commercial binder-free KY studied in this work is a good alternative adsorbent for the adsorption CO2, being also characterized by a high adsorption capacity at low pressure (below 1 bar) when compared to other cation exchanged materials. In addition, the binder-free type KY was responsible for an improvement for up to 20 % in CO2 loading compared to the standard binder beads of KY zeolite. Binary-component experiments CO2/N2 were also carried out under typical post-combustion conditions (15% CO2 / 85% N2) at 313, 373 and 423 K. At 313 K, the selectivity of CO2 over N2 goes over 105 at low pressures below 0.1 bar. At 298 K, the competitive working capacity between 0.03 and 1 bar is equal to 4.52 mol.kg-1, which is a relatively high value when compared with materials such as: Mg-MOF-74 and zeolite 13X. Generally, the results show that binder-free KY works best in the low-pressure region and therefore, is a promising adsorbent for the recovery of CO2 from post-combustion streams. Also, the binary breakthrough curves CO2/N2 onto the binder-free zeolite KY were simulated using a numerical technique developed in MATLAB. The results showed that the zone spreading of the breakthrough curves in the bed are completely dominated by axial dispersion. The effect of the flowrate of N2 to clean the bed was also studied by simulation and the results showed that it is possible to reduce the total volume of N2 used in the desorption step by at least 13% while reducing the N2 purge time up to 71%.
- Single- and multi-component fixed-bed adsorption of CO2, CH4, and N2 on ion-exchanged binder-free NaY zeolitesPublication . Aly, Ezzeldin; Zafanelli, Lucas F.A.S.; Henrique, Adriano; Freitas, Francisco A. da Silva; Rodrigues, Alírio; Silva, José A.C.Ion-exchange was performed on bare commercial binder-free NaY zeolite with alkali (K+) and alkaline earth (Ca2+) metal cations in the range 23, 58, and 95% exchange for K+, and 56 and 71% for Ca2+, to be used as candidates regarding CO2 post-combustion capture (PCC) and biogas upgrading by adsorption processes. Adsorption equilibrium isotherms of CO2, CH4 and N2 were measured on all these cation-exchanged samples using a chromatographic technique between 308 and 348 K and pressures up to 350 kPa and modelled by the dual-site Langmuir isotherm. The CO2 adsorption capacity increases as Na+ is exchanged further by K+ and the reverse for the Ca2+ exchange. The single- and binary-component breakthrough curves were numerically simulated and accurately predicted using the Aspen Adsorption package. This work discloses the importance of ion-exchange on binder-free beads of NaY zeolite to improve its performance in PCC and biogas upgrading applications
- Separation of n/iso-paraffins in a hierarchically structured 3D-printed porous carbon monolithPublication . Henrique, Adriano; Zafanelli, Lucas F.A.S.; Aly, Ezzeldin; Steldinger, Hendryk; Gläsel, Jan; Rodrigues, Alírio; Etzold, Bastian J.M.; Silva, José A.C.Hierarchically structured 3D-printed porous carbons monoliths were investigated for their applicability in adsorptive n/iso-paraffin separation. Three materials of the same macroscopic shape were employed, which varied in the micro- and mesoporosity by altering the final CO2 activation step: non-activated and activated at 1133 K for 6 and 12 h, respectively. Chromatographic breakthrough experiments were conducted for pentane and hexane isomer mixtures at industrially relevant separation conditions. Results demonstrated that the initial porosity for the non-activated monolith enables the complete separation of linear paraffins from their branched isomers (slightly adsorbed) via a near molecular sieving effect. The Langmuir isotherm conveniently fitted the adsorption equilibrium data, and a dynamic mathematical model suitably predicted the breakthrough curves. Regarding the CO2 activated monoliths, both showed adsorption towards all alkanes with practically no selectivity between them.
- Separation of Branched Alkane Feeds with Metal-Organic FrameworksPublication . Henrique, Adriano; Brântuas, Pedro; Zafanelli, Lucas F.A.S.; Aly, Ezzeldin; Rodrigues, Alírio; Maurin, Guillaume; Serre, Christian; Silva, José A.C.The production of high-quality gasoline is currently achieved through the Total Isomerization Process that separates n/iso-paraffins in the pentane (C5) and hexane (C6) range while not reaching the ultimate goal of a research octane number (RON) higher than 92. This work demonstrates two promising alternatives/strategies using metal-organic frameworks (MOF) that lead to a novel adsorptive separation process to overcome this limitation. Here, the efficient discrimination of C5/C6 alkane isomers into valuable fractions of high RON (HRON – 2,3-dimethylbutane (23DMB; RON 105), 2,2-dimethylbutane (22DMB; RON 94), and isopentane (iC5; RON 93.5)) and low RON (LRON – n-pentane (nC5; RON 61.7), (nC6; RON 30), 2-methylpentane (2MP; RON 74.5), and 3-methylpentane (3MP; RON 75.5)) compounds is achieved.
- Dual-Stage Vacuum Pressure Swing Adsorption for Green Hydrogen Recovery from Natural Gas GridsPublication . Zafanelli, Lucas F.A.S.; Aly, Ezzeldin; Henrique, Adriano; Rodrigues, Alírio; Silva, José A.C.A shift to renewable energy sources is crucial to mitigating climate change. Fossil fuels, such as petroleum, natural gas, and coal, mainly contribute to the economy’s growth. However, their use is also the main contributor to global warming. According to the IPCC report, in 2019, the combined energy supply, industry, and transport sectors represented 73% of the total net anthropogenic emissions, which means approximately 42.7 GtCO2 was released into the atmosphere by these sectors. Green Hydrogen (GH), produced from the electrolysis of water, has the potential to play a significant role in reducing CO2 emissions from fossil fuel systems. Additionally, GH can serve as an intersectoral bridge by storing and utilizing intermittent renewable energy sources (such as wind and solar) for later use in the energy supply, industry, and transport sectors. Following the production of GH, it can be injected into existing natural gas grids (NGG) for cost-effective transportation, thus eliminating the need for extensive infrastructure investments. However, when GH is blended into the NGG, it is necessary to recover and purify it to a high purity level to facilitate applications such as fuel cells (H2 > 99.97%). One challenge associated with separating and purifying GH blended in NGG is the low H2 feed concentration (<20%), which is significantly lower than that required for traditional H2 adsorption purification processes, for example, H2 produced from steam methane reforming (>70%). In this work, we develop a conceptual dual-stage vacuum pressure swing adsorption (VPSA) process to separate and purify H2 blended into the natural gas grids with low H2 feed concentration (<20%).
- Simulation of fixed bed adsorption for biogas upgradingPublication . Zafanelli, Lucas F.A.S.; Aly, Ezzeldin; Henrique, Adriano; Rodrigues, Alírio; Silva, José A.C.Great efforts have been devoted to developing clean sources of energy that can contribute to keeping global warming below 2ºC in the coming 30 years. Biogas is a renewable source of energy that can be easily produced by the treatment of agricultural, municipal, and industrial wastes. Furthermore, biogas can be a decentralized alternative to produce clean energy in Portugal and India, as both have a large quantity of feedstock. The second main component of biogas is CO2, which decreases its heating value practically by half relative to natural gas. Therefore, biogas needs to be upgraded (by removing CO2) to obtain biomethane that can be either injected into natural gas networks or directly used as a vehicle fuel. In this way, adsorption processes are a promising alternative to biogas upgrading as it presents a lower energy cost, is easy to operate, can provide higher purity and recovery, as compared to other methods, and especially for the possibility of regenerating the adsorbent material without generating by-products. In this view, this work seeks to develop an adsorption simulator to study the separation of CO2/CH4/N2 mixtures in a fixed bed. To achieve this objective, a mathematical model has been developed to describe the adsorption of mixtures in a fixed bed solved through numerical methods available in the literature. The adsorption mathematical model, derived from mass and energy conservation laws, was implemented in a personal computer to predict the dynamic behavior of the adsorption process. Moreover, this mathematical model includes both effects of axial dispersion and mass-transfer resistances considering an overall effective rate mass-transfer (KLDF) from the linear driving force model. The numerical implementation was performed in MATLAB® simulation environment. To solve the mathematical model the method of lines was used, being the spatial coordinates discretized by orthogonal collocation, and the resulting ordinary and algebraic differential equations were solved with a stiff integrator, ode15s, available in the MATLAB library. The implemented model was tested and validated by simulating experimental data of fixed-bed adsorption of CO2, CH4, and N2 on binder-free zeolite 4A and KY performed in our laboratory. In summary, the simulator implemented in this work is a versatile tool to describe the adsorption process and is useful in processes simulation.
- Green hydrogen recovery from natural gas grids by adsorption processPublication . 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).
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