CO2 Desorption Research Articles

The effect of Fe2O3 doping on a Pt/Co3O4 catalyst for CO oxidation: Improvement of thermal stability and catalytic activity

Although Pt/Co3O4 is an active catalyst for CO oxidation, its low thermal stability may impede its application. The thermal stability and catalytic performance of Pt/Co3O4 were considerably enhanced by Fe2O3 doping. Fe2O3 doping stabilized the mesostructured material during the high-temperature treatment, and the Fe2O3-doped samples retained a larger specific surface area. The characterization results revealed that Fe2O3 doping inhibited catalyst crystallization and decomposition and the growth of catalyst grains during high-temperature calcination. The Fe2O3 doping reduced the Co-O bond strength in the surface Co3O4 lattice, increased the Co3+ ratio, and generated highly active surface oxygen species. Fe2O3 doping also facilitates CO2 desorption, which improves CO adsorption and oxidation. SO2 and NO impede CO oxidation on Pt/Fe2O3/Co3O4. This negative impact was caused by the inert species formed when SO2 or NO reacted with O2 on the catalyst, such as SO42-, HSO4-, or nitrate species, which covered the active sites.

Enhanced CO2 absorption in amine-based carbon capture aided by coconut shell-derived nitrogen-doped biochar

The sluggish CO2 absorption kinetics and constrained CO2 absorption capacity diminish the practicality of using amine-based absorption for CO2 capture, impeding progress toward carbon neutrality goals. This study aims to develop a catalytic CO2 absorption process to promote CO2 absorption by introducing a solid base catalyst, namely, coconut shell-derived nitrogen-doped biochar (NBC), into an amine-based solution. The coconut shells were modified with urea and activated with KOH to prepare an NBC catalyst with improved basic characteristics. The findings showed that compared to non-catalytic absorption, the NBC catalyst increased the CO2 absorption amount, CO2 absorption rate, and absorption efficiency of the monoethanolamine (MEA) solution by 16.9 %, 43.4 %, and 13.1 %, respectively. The basic sites on the NBC surface provided extra electrons to motivate the formation of MEACOO- and HCO3-. NBC’s large surface area and porous structure also advanced the gas–liquid mass transfer, accelerating the CO2 absorption rate. Furthermore, the NBC exhibited excellent cyclic stability and facilitated the subsequent CO2 desorption process. This work develops a promising and practical approach to significantly improve the amine-based absorption and reuse of waste biomass resources for efficient CO2 capture.

A multiphysics model for predicting spatiotemporal temperature profiles in microwave-heated carbon capture processes

Due to alarming rise in atmospheric CO2 ppm levels, the direct air capture process has been engineered to capture low concentrations of CO2 directly from the atmosphere using chemisorbents. However, the regeneration of chemisorbents can be energy-intensive and may not always be efficient. To potentially enhance this, microwave is employed for selective and targeted heating of the chemisorbent. Existing measurement techniques struggle to accurately capture the spatiotemporal temperature profile of solvent impregnated polymer (SIP) under microwave heating. Therefore, it becomes crucial to determine the spatiotemporal temperature distribution inside the polymer phase to expedite CO2 desorption, improve energy efficiency, and prevent material degradation. Motivated by these considerations, we propose a 3D-multiphysics model to study the spatiotemporal distribution of temperature inside a hybrid nanoscale multi-functional material. We focus on the microwave heating of a novel heterogeneous system comprising a SIP with a ferromagnetic additive (Fe3O4), further solving the heat diffusion and Maxwell’s electromagnetic equations to analyze the temperature variation inside the SIP system. By coupling the physics of electromagnetism and heat transfer, our model allows for a comprehensive analysis of the temperature distribution and heating effects inside the chemisorbent. Additionally, we conduct sensitivity analysis of spatiotemporal temperature profile on various thermal and dielectric parameters, as well as the size and location of the Fe3O4 layer. These results can help to optimize desorption rates and make the regeneration process more energy-efficient in future studies.

Catalytic behavior of aluminum-modified SAPO-34 catalysts for reducing the energy penalty of CO2-rich amine solutions regeneration

The goal of this research is to develop a potential strategy to significantly decrease the heat duty for the amine-based CO2 capture process. Here, a variety of Al2O3-modified SAPO-34 composite catalysts with varying Al2O3 contents are synthesized and utilized to catalytically facilitate the CO2 desorption process. The catalytic CO2 desorption characteristics of various catalysts, Al-SAPO-34, SAPO-34, and γ-Al2O3 are investigated in a CO2-loaded 5 M monoethanolamine (MEA) solution. The results indicate that all catalysts accelerate CO2 desorption, while the Al-SAPO-34 catalysts work better than the parent Al2O3 and SAPO-34 catalysts. Especially, the 15 % Al-SAPO-34 increases the CO2 desorption rate by 78.4 % and reduces the relative energy requirement by 37 % at a desorption time of 1440 s. The catalysts are characterized by different methods and their structure–activity relationship is analyzed. The increased acid sites and mesoporous surface area of the Al-SAPO-34 catalyst may be responsible for its greater catalytic activity. The intermediates of the catalytic CO2 desorption process are identified by FT-IR and NMR, and then a possible catalytic regeneration mechanism is put forward. Additionally, the cyclic stability of the Al-SAPO-34 catalyst for cyclic CO2 absorption–desorption is evaluated. This work demonstrates that the Al-SAPO-34 exhibits greater catalytic CO2 desorption performance, and outstanding stability, and has the opportunity to become an attractive industrial catalyst for the amine-based CO2 capture process.

CO2 desorption and mass transfer characteristic study in micropacked bed reactors

The chemical desorption method with amine-based solvent have been widely applied in CO2 capture and storage (CCS) industrial. However, there is still exist mass transfer limitation and difficult to achieve packing/catalyst immobilization in conventional reactors for CO2 desorption process. In this work, micropacked bed reactors (μPBRs) with glass beads are adopted to investigate CO2 desorption performance. Effects of absorbent type, temperature, initial concentration of absorbent, liquid superficial velocity, initial loading of absorbent, particle size, and N2 superficial velocity on the desorption efficiency and desorption rate are discussed. The desorption efficiency of μPBR is 36 ∼ 81 % based on the MDEA absorbent. The value of desorption rate in μPBR is from 0.38 to 3.37 mmol/min, which is bigger than microchannel reactor. Liquid phase mass transfer coefficient of μPBR is 0.06 ∼ 1.38 s−1 for CO2 desorption process, which is 1–3 orders higher than that of packed column. Then, an empirical correlation of mass transfer coefficient is developed in μPBR. μPBR has a high mass transfer rate with an advantage of fixed packing/catalyst compared with other CO2 desorption equipment.

Performance assessment of novel catalytic spouted-bed vapor jet flow heat exchanger in amine-based carbon capture process

This study introduced a spouted bed and jet flow catalytic heat exchanger (SBJ-EX). This novel non-agitated technology can potentially integrate with a conventional desorption column to enhance heat transfer and CO2 desorption performance in amine-based post-combustion carbon capture systems. As its first research in the carbon capture field, this work experimentally evaluated key factors including overall heat transfer coefficient, logarithmic mean temperature difference, temperature distribution along the reactor, and cyclic loading under varied parameters such as inlet temperature of the heating oil, inlet solvent temperature, rich CO2 loadings, and mass of catalysts to simulate real-world operating conditions using benchmark MEA solvent and solid acid catalyst HZSM-5. Compared to conventional plate heat exchangers, the SBJ-EX demonstrated over a 70 % enhancement in heat transfer performance due to its effective overall heat transfer coefficient. It also exhibited impressive CO2 desorption performance even at lower temperatures with sufficient catalysts. Unlike agitated-type heat exchangers, the SBJ-EX could minimize catalyst attrition and offer more excellent stability. In contrast to fixed-bed catalyst desorbed columns, this equipment offered a more compact design for quicker and simpler catalyst replacement to reduce downtime for operators significantly. The SBJ-EX can also function as an optional backup or add-on unit to provide operators with flexibility. This work further discussed advantages and challenges of the SBJ-EX operation. This work enriched the future research outlook for this technology, and contributed a commercially viable approach to catalysts in carbon capture processes.

Cerium-MOF-Derived Composite Hierarchical Catalyst Enables Energy-Efficient and Green Amine Regeneration for CO2 Capture.

The excessive energy consumed restricts the application of traditional postcombustion CO2 capture technology and limits the achievement of carbon-neutrality goals. Catalytic-rich CO2 amine regeneration has the potential to accelerate proton transfer and increase the energy efficiency in the CO2 separation process. Herein, we reported a Ce-metal-organic framework (MOF)-derived composite catalyst named HZ-Ni@UiO-66 with a hierarchical structure, which can increase the CO2 desorbed amount by 57.7% and decrease the relative heat duty by 36.5% in comparison with the noncatalytic monoethanolamine (MEA) regeneration process. The composite catalyst of the CeO2 coating from the UiO-66 precursor on the HZ-Ni carrier shows excellent stability with a long lifespan. The HZ-Ni@UiO-66 catalyst also shows a universal catalytic effect in typical blended amine systems with a large cyclic capacity. The HZ-Ni@UiO-66 catalyst effectively decreases the energy barrier of the CO2 desorption reaction to reduce the time required to reach thermodynamics, consequently saving the energy consumption generated by water evaporation. This research provides a new avenue for advancing amine regeneration with less heat duty at low temperatures.

Synergistic enhancement of CO2 capture via amine decorated hierarchical MIL-101(Cr)/SBA-15 composites

Synthesis of amine incorporated hierarchical metal organic framework (MOF) MIL-101(Cr)/SBA-15, meso/micro-porous composites, with tailored properties for CO2 capture is reported. The synthesized composites were characterized in terms of their crystallinity, morphology, functional groups, and textural properties. Isothermal adsorption of CO2 from concentrated sites as well as ambient conditions were evaluated by gravimetric and volumetric measurements. The optimized composite i.e., MIL-101(Cr)/SBA-15/PEI-25 showed improved pseudo-equilibrium adsorption capacity of 3.2 mmol/g at 303 K and 1 bar, compared to nascent SBA-15 (0.8 mmol/g) and the MOF, i.e., MIL-101(Cr) (1.3 mmol/g). Such adsorption performance can be attributed to the basic sites of the impregnated polyethyleneimine (PEI), unsaturated Cr(III) metal sites, and the hierarchical pore structure of the composite which imparts chemical as well physical adsorption forces towards CO2 uptake. Interestingly, lower amine loading of 25 wt% in the composite resulted in facile CO2 desorption at much lower temperature of 65 °C. This guaranteed energy-efficiency and good reusability of the composite, after ten cycles, are evident from their structural and morphological studies.

Furfural Hydrogenation Over Reduced Pure (LaBO3) and Substituted (LaB0.5B'0.5O3) (B, B': Fe, Co, Ni) Perovskites

AbstractA series of pure and 50 % substituted Fe‐containing (LaFeO3, LaFe0.5Ni0.5O3 and LaFe0.5Co0.5O3) and Co/Ni‐containing (LaCoO3, LaNiO3, and LaCo0.5Ni0.5O3) perovskites were used as precursors to synthesize metallic reduced catalysts to be tested for the liquid hydrogenation of furfural. The catalytic reaction was carried out in a batch reactor at 200 °C and 3.0 MPa of H2 pressure. The calcined perovskites and reduced catalysts were characterized by X‐ray diffraction (XRD), N2 physisorption at 77 K, temperature programmed reduction (H2‐TPR), temperature programmed CO2 and NH3 desorption (CO2‐TPD and NH3‐TPD), Atomic Absorption Spectroscopy (AAS) and X‐ray photoelectron spectroscopy (XPS) techniques. The LaCo0.5Ni0.5O3 reduced catalyst display the highest activity in furfural conversion, which was attributed to a cooperative effect between highly dispersed nickel and cobalt metal nanoparticles after reduction process. The effect of the nature of B‐cation have a high impact on the products selectivity in the hydrogenation of furfural, suggesting that enriched‐Ni metal surface was selectivity to tetrahydrofurfuryl alcohol, meanwhile enriched‐Co metal surface was selective to furfuryl alcohol formation, which was also supported with adsorption mode of furfural over the active sites obtained by quantum calculation.

Characterizing the 2D single atom solutions to capture CO2 by the digital twin model

The digital twin model is developed to characterize the CO2 capture by the Cu and B 2D single atom solution (2DSAS). The key digital functions distributions f[], g[] and h[] characterize the physical 2DSAS system with the digital code 1 and 0. The thermoelectrical effect of the 2DSAS is analyzed. The digital code combinations of Cu atoms sorting from 1111 to 11,111 with B atoms sorting from 00 to 000 were identified as more suitable for CO2 capture. The effects of velocity difference of Cu and B atoms, temperature and CO2 loading were discussed. CO2 desorption efficiency was increased by an average 4.2 % and the energy consumption of desorption was reduced by 35.4 % at h[] of 3.5 × 10-6 m/s to 5 × 10-6 m/s. The 2DSAS of Cu and C, Cu and N and Cu and Si were suggested for CO2 capture.

Reduce energy consumption for organic amine regeneration by MnOOH/HZSM-5 catalysts

Catalytic regeneration has become one of the most promising technologies to solve the high energy consumption problem of CO2 capture in organic amine solutions. As the most mainstream type of catalyst, the instability of acidic catalysts in alkaline solutions attracts increasing attention from researchers. Herein, we proposed a composite catalyst of MnOOH loaded HZSM-5 to weaken the adsorption of alkaline substances and improve the catalytic stability of the catalytic material. The optimized catalytic effect is obtained when the mass ratio of MnOOH is 20% The CO2 desorption efficiency is increased by 68.2%, and the energy consumption is reduced by 31.8% when the dosage of the catalyst is only dosage of 0.2 wt% amine solution. Through materials characterization and DFT calculations, it was found that the surface O and hydroxyl groups on MnOOH are the key factors for proton cycling, and HZSM-5 has an important impact on improving proton transfer rate. This work provides a valuable approach to solving the stability problem of acidic catalysts.

Synergy between electron donor and steric hindrance in Alkylated-Piperazine absorbents for efficient CO2 capture

Piperazine (PZ) and its derivatives are currently regarded as novel amine absorbents for efficient CO2 capture. However, the in-depth investigation of CO2 capture and understanding of the structure–activity relationship in PZ-based absorbents are still lacking. In this study, we conducted a systematic investigation of CO2 capture within the alkylated PZ-based absorbents. The results demonstrated that the increased alkylation degree can promote CO2 absorption by enhancing the electron donor effect of the secondary amine group in PZ. In addition, the incorporated alkyl group in PZ-based absorbent improves the CO2 desorption process by enhancing the steric hindrance effect. Particularly, the synergy between electron donor and steric hindrance effects in isopropyl alkylated-PZ (IPPZ) enables it to present enhanced cyclic capacity and remarkably low regeneration energy consumption (2.36 GJ·t−1 CO2) for CO2 capture. The present study makes a valuable contribution towards the future design and development of highly efficient absorbents for CO2 capture.

CO2, CH4, and N2 Desorption Characteristics in a Low-Rank Coal Reservoir

CO2, CH4, and N2 Desorption Characteristics in a Low-Rank Coal Reservoir

Enhancing Electrocatalytic CO2-to-CO Conversion by Weakening CO Binding through Nitrogen Integration in the Metallic Fe Catalyst.

Metallic iron (Fe) typically demonstrates the unfavorable catalytic activity for the CO2 reduction reaction (CO2RR), mainly attributed to the excessively strong binding of CO products on Fe sites. Toward this end, we employed an effective approach involving electronic structure modulation through nitrogen (N) integration to enhance the performance of the CO2RR. Here, an efficient catalyst has been developed, composed of N-doped metallic iron (Fe) nanoparticles encapsulated in a porous N-doped carbon framework. Notably, this N-integrated Fe catalyst displays significantly enhanced performance in the electrocatalytic reduction of CO2, yielding the highest CO Faradaic efficiency of 97.5% with a current density of 6.68 mA cm-2 at -0.7 V versus the reversible hydrogen electrode. The theoretical calculations, combined with the in situ attenuated total reflection surface-enhanced infrared absorption spectroscopy study, reveal that N integration modulates the electron density around Fe, resulting in the weakening of the binding strength between the Fe active sites and *CO intermediates, consequently promoting the desorption of CO and the overall CO2RR process.

Enhancing Desorption Performance of a Compressible Hybrid Structured Adsorbent via Localized Magnetic Induction Heating

AbstractStructured adsorbents have gained significant importance in gas separation applications due to their ability to fine‐tune mass and heat transfer and lower pressure drop across the bed. This study presents a ferromagnetic compressible hybrid structured adsorbent, allowing regeneration via magnetic induction heating. A compressible melamine sponge is coated with the CO2‐selective Ni‐MOF‐74 adsorbent and Fe3O4 as a ferromagnetic susceptor, capable of dissipating heat instantaneously in an alternating electromagnetic field. Taking advantage of these properties, the potential of rapid CO2 capture and thermal regeneration via magnetic induction swing adsorption is investigated. The successful incorporation of both ingredients on the melamine sponge is confirmed via SEM‐EDX and XRD analysis. Breakthrough experiments with a CO2/CH4‐mixture are performed. The selective property of Ni‐MOF‐74 toward CO2 is retained, with the composite showing a capacity of 1.89 mmol CO2/g. The compressible nature of the melamine sponge allowed for an improvement of 79% in the volumetric capacity of the adsorbent bed and a higher heating rate. In regard to regeneration, within 1 min of subjecting the structured composite to the alternating magnetic field, an efficient desorption (>90%) of CO2 is achieved. Overall, a ferromagnetic compressible hybrid structured adsorbent is presented for fast cyclic gas‐phase separation processes.

Biogas dry reforming over Li–Ni–Al LDH-derived catalysts

Biogas dry reforming or dry reforming of methane (DRM) is an alternative to produce hydrogen, in the context of development of sustainable routes for energy production, since this route uses CH4 and CO2, two greenhouse gases as reactants. However, the deactivation of catalysts due to carbon deposition and sintering is the main drawback of this reaction. In this work, with the aim of minimizing carbon formation and sintering during DRM, the effect of lithium as a promoter in catalysts Ni–Al derived from layered double hydroxides was investigated. The catalysts were prepared by co-precipitation and characterized by different techniques: BET surface area (SBET), X-ray diffraction (XRD), temperature-programmed reduction (TPR), CO2 and H2 temperature-programmed desorption (CO2-TPD and H2-TPD), Scanning Electron Microscopy (SEM-EDS), temperature-programmed oxidation (TPO). The catalytic tests were carried out in a fixed bed reactor using a synthetic biogas (60% CH4 and 40% CO2) in the temperature range of 500–750 °C. The incorporation of Li into the Ni–Al-LDH changed the reducibility and basicity of the catalysts. The Li2 sample containing an intermediary amount of Li (5 wt%) showed the highest reduction temperature and highest density of basic sites, which resulted in the smallest Ni crystallite size before and after the reactions. As a result, this catalyst presented the greater resistance to sintering and a lower rate of carbon produced. For the reaction carried out at 700 °C, only the Li2 catalyst remaining active during the test and reaching a maximum of 80% and a final CH4 conversion of 54% after 480 min of reaction, whereas CO2 conversion was higher than 90%. All other samples deactivated at different rates due to carbon deposition and sintering.

Insight into CO2 capture by aqueous solutions of N,N‐diethylethanolamine promoted with potassium salts of amino acids

AbstractN,N‐Diethylethanolamine (DEEA) is a potential high‐capacity CO2‐capturing solvent. The CO2 reactivity of DEEA can be improved by the addition of rate promoters. Both equilibrium CO2 solubility and desorption rate are also influenced by promoters. In this work, the effect of promotion of DEEA with three amino acid salts, potassium arginate (PA), potassium prolinate (PP), and potassium glycinate (PG), was investigated. In a stirred cell reactor, CO2 reactivity of the promoted solutions was studied at 303 K. Rate promotion with PA was most effective; this was then followed by PP and PG. The value of the liquid‐side mass transfer coefficient (0.005 cm/s) for CO2 absorption in water inside the stirred cell was found. Equilibrium CO2 solubility in the promoted mixtures was measured. Empirical equations that predicted solubility data (accuracy 99%) were proposed. Desorption trials were performed at 363 K. PA, PP, and PG lowered sensible energy constraint by 59%, 32%, and 30%. PA was most‐suited for faster desorption of aqueous solutions of DEEA. Overall, potassium salts of arginine, proline, and glycine were promising candidates for improving the performance of the tertiary amine DEEA. Finally, catalytic desorption of loaded solutions of DEEA was studied and it was found that alumina was a promising catalyst for faster desorption.

Coordination-based synthesis of Fe single-atom anchored nitrogen-doped carbon nanofibrous membrane for CO2 electroreduction with nearly 100% CO selectivity

Carbon-based materials with single-atom (SA) transition metals coordinated with nitrogen (M-Nx) have attracted extensive attention due to their superior electrochemical CO2 reduction reaction (CO2RR) performance. However, the uncontrolled recombination of metal atoms during the typical high-temperature synthesis process in M-Nx causes deterioration of CO2RR activity. Herein, by using electrospinning, we propose a novel strategy for constructing a highly active and selective SA Fe-modified N-doped porous carbon fiber membrane catalyst (Fe-N-CF). This carbon membrane has an interconnected three-dimensional structure and a hierarchical porous structure, which can not only confine Fe to be single atom as active centers, but also provide a diffusion channel for CO2 molecules. Relying on its special structure and stable mechanical properties, Fe-N-CF is directly used for CO2RR, which presents an excellent selectivity (CO Faradaic efficiency of 97%) and stability. DFT calculations reveals that the synthesized Fe-N4-C can significantly reduce the energy barrier for intermediate COOH* formation and CO desorption. This work highlights the specific advantages of using electrospinning method to prepare the optimal SA catalysts.

Amine-functionalized macroporous resin for direct air capture with high CO2 capacity in real atmospheric conditions: Effects of moisture and oxygen

Direct air capture (DAC) is an important negative carbon emission technology that has attracted increasing attention. Amine-functionalized porous CO2 adsorbents are promising materials for DAC because of their high CO2 capacities, fast adsorption and desorption kinetics, and low energy costs during regeneration. In this study, inexpensive macroporous resins with high specific surface areas and pore volumes were selected as carriers of tetraethylenepentamine (TEPA) or polyethyleneimine (PEI). Their DAC performances in relation to their microstructures were explored under different humidity and oxygen conditions. Moisture simultaneously enhanced the CO2 capacity and slowed the adsorption/desorption process. Oxygen did not react with the resin and amine under ambient conditions, but physically adhered to the active sites of the adsorbents and caused a slight decrease in the CO2 uptake capacity. The optimized material reached adsorption equilibrium in 7269 s with CO2 uptake capacity of 5.4 mmol g−1 and desorbed CO2 in 1611 s with CO2 desorption capacity of 5.0 mmol g−1. After five cycles, the materials retained 82.2 % of the adsorption capacity. The findings indicate that amine-functionalized macroporous resins are promising DAC adsorbents under atmospheric conditions.

Environmental Impact Evaluation of CO2 Absorption and Desorption Enhancement by Membrane Gas Absorption: A Life Cycle Assessment Study

Membrane gas absorption technology has been considered a promising approach to mitigate CO2 emissions from power plants. The aim of this study is to evaluate the environmental impacts of CO2 absorption and desorption processes by hollow fiber membrane contactors using a life cycle assessment methodology. On the basis of the ReCipe 2016 Midpoint and the ReCipe 2016 Endpoint methods, the research results show that membrane gas absorption systems exhibit the lowest environmental impacts across the majority of assessed categories in comparison with chemical absorption and membrane gas separation systems. The CO2 capture process via membrane gas absorption has the most significant impact on the METP category, with heat consumption as the primary contributing factor accounting for 55%, followed by electricity consumption accounting for 43.1%. According to the sensitivity analysis, heating by natural gas shows better performance than other heat supply sources in improving overall environmental impacts. In addition, the increasing utilization of renewable energy in electricity supply reduces the global warming potential, fossil resource consumption and ozone formation.