Next Article in Journal
Attentional Keypoint Detection on Point Clouds for 3D Object Part Segmentation
Previous Article in Journal
Three-Dimensional Model-Based Line-of-Sight Analysis for Optimal Installation of IoT Monitoring Devices in Underground Mines
Previous Article in Special Issue
Reduction of Water Color in a Spinning Disc Reactor
 
 
Search for Articles:
Title / Keyword
Author / Affiliation / Email
Journal
Article Type
 
 
Advanced Search
 
Section
Special Issue
Volume
Issue
Number
Page
 
Journals
Applied Sciences
Volume 13
Issue 23
10.3390/app132312536
applsci-logo
Submit to this Journal Review for this Journal Propose a Special Issue
► Article Menu

Article Menu

share Share announcement Help format_quote Cite question_answer Discuss in SciProfiles thumb_up
...
Endorse textsms
...
Comment
first_page
settings
Order Article Reprints
Font Type:
Arial Georgia Verdana
Font Size:
Aa Aa Aa
Line Spacing:
Column Width:
Background:
Article

Trapping and Methanation of CO2 in a Domestic Microwave Oven Using Combinations of Sorbents and Catalysts

by
Loren Acher
*,
Tristan Laredo
,
Thierry Caillot
,
Akim Kaddouri
and
Frederic C. Meunier
*
Univ Lyon, Université Claude Bernard Lyon 1, CNRS, IRCELYON, 2 Av. Albert Einstein, 69626 Villeurbanne, France
*
Authors to whom correspondence should be addressed.
Appl. Sci. 2023, 13(23), 12536; https://doi.org/10.3390/app132312536
Submission received: 3 November 2023 / Revised: 17 November 2023 / Accepted: 20 November 2023 / Published: 21 November 2023
(This article belongs to the Special Issue Pollution Control Chemistry II)
Browse Figures
Review Reports Versions Notes

Abstract

:
CO2 trapping and methanation allow to reduce greenhouse gas emissions and recycle CO2 into a sustainable fuel, provided renewable H2 is employed. Microwave (MW)-based reactors provide an efficient means to use electrical energy for upgrading chemicals, since MW can selectively heat up the load placed in the reactor and not the reactor itself. In this study, CO2 capture and methanation were investigated using solid adsorbents (ZrO2 and Fe3O4), microwave absorbers (SiC and Fe3O4) and Ru/SiO2 as CO2 the methanation catalyst. The sorption and catalyst beds were located in a domestic MW oven that was used to trigger CO2 desorption and methanation in the presence of H2. The working Fe-based structure turned out to be a mixture of FeO and Fe, which allowed for MW absorption and local heating; it also acted as a CO2 sorbent and reverse water–gas shift catalyst. Various reactor configurations were used, leading to different performances and selectivity to CO and CH4. To the best of our knowledge, this is the first report of its kind showing the potential of using inexpensive microwave technology to readily convert trapped CO2 into valuable products.

1. Introduction

CO2 emissions represent a major fraction of greenhouse gas emissions induced by human activities and should be reduced to limit climate change [1]. CO2 capture and utilization (CCU) will play a prominent role in restructuring the energy sector and the fight against global warming. CO2 could be trapped within large industrial units (e.g., power plants, boilers, and cement manufacture) and reprocessed on-site or remotely. The hydrogenation of CO2 into convenient fuels such as CH4 through the Power-to-Gas (PtG) technology is of strong interest [2]. CH4 is produced through Sabatier reaction (Equation (1)), which is catalyzed by Ru- or Ni-based catalysts [3].
CO2 + 4 H2 → CH4 + 2 H2O
CO2 + H2 → CO + H2O
Note that the reverse water–gas shift (RWGS) reaction (Equation (2)) is often proposed as an intermediate step during methanation [4]. The H2 needed for these reactions should preferably be obtained from water electrolysis using renewable or nuclear energy. CH4 could be then directly injected into the already existent pipeline networks or storage infrastructures. Developing an effective system that could combine CO2 capture and conversion to CH4 in a single unit is of particular interest for the efficiency of PtG plants.
Amine solutions are used industrially for CO2 trapping [5], and a recent process was proposed that could produce CH4 at 170 °C in a multiphasic batch reactor by mixing CO2-saturated amine solutions with a Ru-based heterogeneous catalyst [6]. Yet, processing high-pressure multiphasic batch reactors is costly and complex. Simpler isothermal sequential processes solely based on solid traps and catalysts, so-called “dual function materials” (DFMs), have been proposed [7,8,9,10]. DFMs contain a CO2-storing component, typically an alkali or Earth-alkali oxide, which exhibit a strong basic character [11,12,13], and a catalytic metal able to hydrogenate CO2 to methane, usually Ru or Ni or alloys of those [7,8,9,10]. Na-exchanged zeolites exhibit some of the highest CO2 adsorption capacity under direct air capture conditions [14].
The release of the trapped CO2 implies an energy cost, which can be minimized by using oxides of weaker basicity such as zirconia [15]. Energy savings can also be achieved by using microwave (MW) heating, which does not require heating up the whole reactor assembly [16]. Ellison et al. recently reported that the use of microwave heating for CO2 desorption from zeolite 13X increased the adsorption/desorption cycling productivity and potentially reduced the energy penalty of sorbent regeneration [17]. In addition, these authors determined an apparent activation energy of the MW-assisted desorption which is significantly lower than that obtained via conventional heating. Jang et al. also showed that desorption of a solid guanidine carbonate under MW heating is up to 17 times faster than conventional conductive heating at 160 °C, resulting in a 40% electrical energy reduction [18]. Moreover, energy savings for desorption can rise up to 94% when the sorbent is microwave-transparent (i.e., when only the adsorbed molecules are heated up) [19]. Tubes, fitting and reactors can be made of microwave-transparent materials such as polytetrafluoroethylene PTFE (=Teflon®) or quartz [20,21], meaning that those also would not consume electromagnetic energy and remain at low temperatures. Such a design should allow for further energy saving and facilitate process design.
We recently reported on the use of a simple domestic MW oven to carry the combined trapping and combustion of volatile organic compounds (i.e., toluene, n-decane and formaldehyde) [22]. The method and experimental setup used in this previous study is actually well-suited to carry out similar work on the trapping and methanation of CO2. This study will actually be the first of its kind, to the best of our knowledge, as we could not find any previous investigation on the combined trapping and methanation of CO2 in an MW oven. Earlier MW-based studies involving CO2 and CH4 were mostly focused on methane dry reforming [20].
The objective of the present study was to investigate the possibility of using a domestic microwave oven to desorb CO2 from a sorbent under MW irradiation and simultaneously hydrogenate the released CO2 to methane. High surface area ZrO2 was used as CO2 adsorbent because of its known basicity [15] and high thermal stability. The use of Na-exchanged zeolite was avoided in the present study because of the potential temperature runaway under MW that can lead to melting of these solids [22]. SiC and Fe3O4 were employed as MW absorbers [20]. Silica-supported ruthenium was chosen as methanation catalyst because of its high activity [8,9,10] and the ease with which it can be reduced. The results will show that the various extents of CO2 conversion and selectivity to CH4 can be obtained depending on bed configurations, requiring to further optimize the system to maximize the yield to methane and limit bed overheating that led to catalyst deactivation.

2. Materials and Methods

ZrO2 (monoclinic, 131 m2 g–1) was provided by MEL Chemicals and characterized in detail elsewhere [23]. Fe3O4 (10 m2 g–1) was bought from Alfa Aesar (lot X08G023). SiC (120 grit, ca. 137 µm particles) was purchased from Alfa Aesar (batch #10179265). A silica-supported ruthenium methanation catalyst (6.8 wt.% Ru measured with ICP, Ru dispersion = 22% measured using H2 chemisorption, corresponding to 4 nm particles) was prepared via dry impregnation using RuCl3-xH2O precursor. High purity gases N2, H2, O2 and CO2 from Air Liquide were used without any further purification.
The experimental setup is illustrated in Figure 1A,B. The gas flow rates were controlled using Brooks electronic mass flow controllers. A commercial 800 W MW domestic oven (Sharp, model YC-MS01E-W) was modified as described elsewhere [22]. The MW oven power was always set to the maximum when used. Two quartz tubes were placed in the oven to accommodate the sorbent and catalyst beds, using PTFE (Teflon®, Wilmington, NC, USA) Swagelok fittings. Sorbent and catalyst beds were held with quart wool plugs. Gases were flown through polyethylene tubing passing through 2 mm holes drilled in the oven cavity.
The feed could be sent through the sorbent and catalytic beds first or directly into the IR gas analyzer, which consisted of a 10 cm pathlength IR gas cell (from Harrick) fitted in a Bruker Tensor 27. The gas cell was kept at 80 °C and 8 scans were averaged at a resolution of 4 cm−1. A typical FT-IR transmission spectrum showing methane, CO and CO2 bands are given in Figure 1C. IR Band assignment was ascertained via comparison to the NIST database [24,25,26]. CO2 and product concentrations were derived from calibration curves, using the area of the bands located at 670 cm−1 (for CO2), 3015 cm–1 (for methane) and 2145 cm–1 (for CO). The conversion of CO2 was calculated as the ratio between reacted CO2 and the inlet CO2, the reacted CO2 being the difference between the measured CO2 and the inlet CO2. The signal of the inlet CO2 was measured by by-passing the reactor. The yield of CO (or CH4) was calculated as the concentration of CO (or CH4) divided by that of reacted CO2.
Zones in which an effective MW absorption by the materials occurred were determined from sample black body radiation, since it is difficult to measure temperatures in multimode MW ovens and because of the likely presence of strong temperature gradients within long (several centimeters) beds [27,28]. Two positions associated with intense MW fields were found, shown in Figure 1B, expressed by the distance (in mm) from the oven center and height: (50; 30) and (115; 60), respectively. Figure 2 shows typical brilliances obtained from a mixture of SiC and Fe3O4 placed in the catalyst bed. It is worth stressing that the SiC + Fe3O4 mixture became red hot (i.e., T > 500 °C) in less than 10 s.
An operando diffuse reflectance FT-IR spectroscopy (DRIFTS) cell (High Temperature reaction cell from Harrick, described elsewhere [29]) was used to measure the activity for CO2 methanation of the fresh and aged Ru catalysts as a function of temperature and determine the nature of surface species present under reaction conditions. The catalyst temperature was measured with a thermocouple located at the top of the bed within the thin catalyst layer (corresponding to precisely weighted masses around 10 mg) placed on SiC, since DRIFTS reaction cells often present large temperature gradients [29,30].

3. Results and Discussion

3.1. CO2 Methanation under Continuous Flow Conditions under MW

The sorption bed was left empty in this case to measure the activity of various combinations of SiC, Fe3O4 and Ru/SiO2 loaded in the catalytic reactor under a continuous flow of CO2 and H2 while irradiated by MW. The presence of only SiC led to no measurable activity (Figure 3A). A full conversion of CO2 was obtained over the SiC + Fe3O4 physical mixture, but the only product was CO. This observation is consistent with the well-known fact that iron oxides are active catalysts for the RWGS reaction (Equation (2)) but not for COx methanation [31].
A layer of Ru/SiO2 was added to catalytic reactor just after the SiC + Fe3O4 mixture, separated with a 5 mm quartz wool plug. This configuration led to a full CO2 conversion, with methane being the only product at steady-state (Figure 3A, third entry). However, the second run with the same configuration led to a CH4 yield of about 90% and a yield of CO of 10%. This suggests that the Ru-based catalyst had been deactivated during the first run, likely due to sintering of the Ru particles exposed to the high temperatures of the red-hot glowing SiC + Fe3O4 mixture, despite being located about 5 mm away.
The time-resolved product analysis of the second run with the (SiC + Fe3O4) + Ru/SiO2 configuration is shown in Figure 3B. The initial lag time before observing any conversion was both due to the time needed to purge the line dead-volume to reach the IR analyzer and the time needed to heat up the reactor under MW. CO was initially observed as the sole reaction product, before declining in yield, followed by the rise of the methane yield. This suggests that the initial activity was only due to the RWGS activity of the FeOx component and that the temperature of the Ru catalyst was too low to achieve methanation.
Interestingly, the carbon balance was significantly lower than 100% just after the light off (Figure 3B). This suggests that part of the CO formed was initially trapped in the reactor, likely as carbonyl species formed at the surface of the Ru nanoparticles. This hypothesis was checked by carrying out an operando DRIFTS analysis described in the subsequent section.

3.2. CO2 Methanation under Continuous Flow Conditions in a DRIFTS Reactor

The operando study was carried out by introducing the methanation stream (2% CO2 + 20% H2 in N2) at room temperature over the samples without any pre-treatment to mimic typical CCU operations under which the sample is initially exposed to CO2 and air. The Ru nanoparticles were thus likely oxidized. No formation of carbonyl of Ru could be observed at room temperature (Figure 4A), indicating that the Ru surface was oxidized or could not activate CO2.
No methanation activity could be measured below 100 °C neither over the fresh nor on the used sample, although bands assigned to Ru0-CO carbonyls [32] were clearly observed at 94 °C (Figure 4A). This indicates that at 94 °C Ru was partly reduced and able to dissociate CO2 and store CO. This likely explains the uncomplete carbon balance observed around 90 °C during the flow experiment (Figure 3B), as the carbonyls formed poisoned the surface at low temperatures.
The ca. 4-fold lower DRIFTS band area of carbonyls species observed over the used sample as compared to the fresh catalyst (Figure 4B) and ca. 5-fold lower methanation rate indicated by the shifted Arrhenius plots (Figure 4C) suggest that the deactivation was mostly due to sintering of the Ru nanoparticles, likely induced by the high temperature of the neighboring radiating SiC + Fe3O4 when exposed to MW. Sintering is a common process in heterogeneous catalysis and can occur through various mechanisms, e.g., metal particle coalescence and Ostwald ripening [33], depending on the mobility of atoms and thermodynamic stability of the particles with respect to their size. Different strategies can be employed to limit sintering, e.g., using porous supports strongly interacting with the metal particles. The sintering of materials exposed to MW has also been discussed in detail elsewhere [34]
Note that the apparent activation energy remained unchanged at about 76 kJ mol–1, in agreement with those reported for highly loaded Ru-based catalysts [35].

3.3. CO2 Trapping Followed by Desorption and Methanation under MW

In the following pulsed experiments, CO2 adsorption was carried out at room temperature using a 2% CO2 + 20% O2 in N2 for 5 min, which was always sufficient to saturate the sorbent used. The system was then purged under N2 for 5 min, then left for 5 min under 20% H2 in N2 with a total flow of 50 mL min–1. The MW power was then turned on for 5 min still under 20% H2 in N2 with a total flow of 50 mL min–1, while monitoring the gases evolved from the system.
ZrO2 poorly absorbed MW and did not release CO2 if not mixed with SiC. SiC did not adsorb and release any CO2 when used alone. In the first pulse experiment shown, the sorption bed was filled with a mixture of ZrO2 + SiC, while the catalyst bed contained both a mixture of SiC + Fe3O4 as MW absorbers, followed by Ru/SiO2 acting as a methanation catalyst (Figure 5A). Figure 5B shows the compounds desorbed as a function of time during MW irradiation. Only a small concentration of CO2 was released, followed by CO and then a larger peak of methane.
These data are consistent with the steady flow experiment reported in Figure 3, in which CO appeared as a primary reaction product, followed by methane. The heating rate of the Ru catalyst seemed insufficient to convert the CO formed initially via RWGS (Equation (2)) over the Fe3O4.
Experiments were carried out to determine the amount of equivalent C (i.e., sum of CO, CO2 and CH4) released by the main components of the system described in Figure 5A. As mentioned earlier, SiC did not release any carbon-containing compound (Figure 6) and the same was observed with the Ru/SiO2 catalyst. Interestingly, Fe3O4 led to a large amount of products, about 3-fold higher than the ZrO2. It must be concluded that the Fe constituent formed some carbonate species when exposed to the CO2 + O2 stream.
The CO2 released by zirconia under our conditions was about 150 µmol g–1, while the use of amine-based methods can lead to reversible sorption capacity as high as 3500 µmol g–1 [36]. It is therefore clear that the adsorption on solids is unlikely to match that obtained in amine solutions. Some of the interests of solids lie in easier handling, lower toxicity and higher thermal stability.
The gain in terms of released species obtained using a sorbent bed with ZrO2 appeared thus limited. A limited interest was also observed in terms of product selectivity by comparing a series of experiment with and without the sorption bed (Figure 7). Similar high CO2 conversion and selectivity to methane were obtained in both cases.
The significant proportion of CO (ca. 20%) in the reaction products is not desirable, and a different catalyst bed configuration was attempted by mixing directly the Ru catalyst with the iron oxide (which can heat up under MW in the absence of SiC) and zirconia to favor fast reduction and higher activity of Ru (Figure 8A). SiC was left out to limit excess temperature, and the mixture thus used became hot under MW irradiation but never glowed red.
The desorption of compounds was fast and essentially completed in 100 s (Figure 8A), but unreacted CO2 was the main species released. Nonetheless, no CO was observed over five consecutive runs, CH4 being the only product (Figure 8B). The quantity of methane produced per total bed mass somewhat declined before stabilizing to about 35 µmol g–1 over the five runs. This value is about 10-fold lower than those reported by Farrauto over some of the best dual function materials (DFM) operated in conventional ovens [8]. Yet, we believe that this is promising for a system that has not yet been optimized and offers a lot of parameters to adjust (e.g., sorbent, MW-absorber, catalyst, bed configuration, and MW power).
The nature of the iron phases present after use were determined with XRD analyses (Figure 9). The used Fe-based material, collected after the experiment reported in Figure 7, contained metallic iron [37,38] and FeO [39] as the main phases, with only traces of Fe3O4 [40] left. These two phases (metallic iron and FeO) are known to absorb better MW than FeIII compounds, as discussed elsewhere [41,42,43,44]. It is thus important to avoid full oxidation of the iron phases. The abilities of the FeO phase to store CO2 as a carbonate and to absorb MW are much greater than that of metallic iron, thus stabilizing FeO appears important for future investigations.
The present study reports for the first time, to the best of our knowledge, that CO2 desorption and methanation can be readily achieved in a domestic microwave oven. The economics of the process would need to be estimated in detail, but probably once the sorbent, MW absorber, methanation catalyst and the process conditions would have been optimized further from the present proof of concept. Since an earlier study reported up to 94% energy savings for an MW-based desorption processes [19], the present method can be regarded as highly promising that could lead to an inexpensive trapping–methanation technology.

4. Conclusions

CO2 trapping and methanation were investigated over sorbents (ZrO2 and Fe3O4) and MW absorbers (SiC and Fe3O4), using Ru/SiO2 as a CO2 methanation catalyst. Fe3O4 adsorbed significant concentration of CO2 but overheated up above 600 °C under MW, leading to a partial sintering of neighboring Ru catalyst. The working Fe-based structure turned out to be a mixture of FeO and Fe, while the Fe3O4 phase essentially disappeared. The reactor configuration with a sorption bed filled with SiC+ZrO2 followed by a catalytic bed filled with SiC + Fe3O4 ahead of a Ru/SiO2 layer led to almost full CO2 conversion with a significant production of CO (ca. 20%) along with CH4. Using only a catalytic reactor filled with a physical mixture of ZrO2 + Fe3O4 + Ru/SiO2 allowed for fast desorption (<2 min) and full selectivity to CH4, although CO2 conversion was only about 20%.
In conclusion, it is possible to use an inexpensive reactor system to trap/release and methanate CO2 under MW irradiation. The proportions and configurations of sorbent(s), MW absorber(s) and methanation catalysts can be adapted to control product selectivity, CO2 conversion, catalyst deactivation and process timescale.

Author Contributions

Conceptualization: All authors. Methodology: F.C.M.; validation: all authors. All authors have read and agreed to the published version of the manuscript.

Funding

This research received no external funding.

Institutional Review Board Statement

Not applicable.

Data Availability Statement

The data presented in this study are available on request from the corresponding author. The data are not publicly available due to file size constraints.

Acknowledgments

The IRCELYON Scientific Services are acknowledged for carrying out the XRD measurements.

Conflicts of Interest

The authors declare no conflict of interest.

Glossary

DFMDual function materials
DRIFTSDiffuse reflectance Fourier-transform infra red
MWmicrowave
PTFEpolytetrafluoroethylene = Teflon®
PtGPower-to-Gas technology
RWGSreverse water-gas shift reaction

References

  1. Szulejko, J.E.; Kumar, P.; Deep, A.; Kim, K.H. Global warming projections to 2100 using simple CO2 greenhouse gas modeling and comments on CO2 climate sensitivity factor. Atmos. Pollut. Res. 2017, 8, 136–140. [Google Scholar] [CrossRef]
  2. Thema, M.; Bauer, F.; Sterner, M. Power-to-Gas: Electrolysis and methanation status review. Renew. Sustain. Energ. Rev. 2019, 112, 775–787. [Google Scholar] [CrossRef]
  3. Meunier, F.C. Hydrogenation of CO and CO2: Contributions of IR operando studies. Catal. Today 2023, 423, 113863. [Google Scholar] [CrossRef]
  4. Messou, D.; Bernardin, V.; Meunier, F.; Borges Ordoño, M.; Urakawa, A.; Machado, B.F.; Collière, V.; Philippe, R.; Serp, P.; Le Berre, C. Origin of the synergistic effect between TiO2 crystalline phases in the Ni/TiO2-catalyzed CO2 methanation reaction. J. Catal. 2021, 398, 14–28. [Google Scholar] [CrossRef]
  5. Meng, F.; Meng, Y.; Ju, T.; Han, S.; Lin, L.; Jiang, J. Research progress of aqueous amine solution for CO2 capture: A review. Renew. Sustain. Energ. Rev. 2022, 168, 112902. [Google Scholar] [CrossRef]
  6. Kothandaraman, J.; Lopez, J.S.; Jiang, Y.; Walter, E.D.; Burton, S.D.; Dagle, R.A.; Heldebrant, D.J. Integrated Capture and Conversion of CO2 to Methane using a Water-lean, Post-Combustion CO2 Capture Solvent. ChemSusChem 2021, 21, 4812–4819. [Google Scholar] [CrossRef]
  7. Zheng, Q.; Farrauto, R.; Nguyen, A.C. Adsorption and Methanation of Flue Gas CO2 with Dual Functional Catalytic Materials: A Parametric Study. Ind. Eng. Chem. Res. 2016, 55, 6768–6776. [Google Scholar] [CrossRef]
  8. Arellano-Trevino, M.A.; Kanani, N.; Jeong-Potter, C.W.; Farrauto, R.J. Bimetallic catalysts for CO2 capture and hydrogenation at simulated flue gas conditions. Chem. Eng. J. 2019, 375, 121963. [Google Scholar] [CrossRef]
  9. Proano, L.; Arellano-Trevino, M.A.; Farrauto, R.J.; Figueredo, M.; Jeong-Potter, C.W.; Cobo, M. Mechanistic assessment of dual function materials, composed of Ru-Ni, Na2O/Al2O3 and Pt-Ni, Na2O/Al2O3, for CO2 capture and methanation by in situ DRIFTS. Appl. Surf. Sci. 2020, 533, 147469. [Google Scholar] [CrossRef]
  10. Omodolor, I.S.; Otor, H.O.; Andonegui, J.A.; Allen, B.J.; Alba-Rubio, A.C. Dual-function materials for CO2 capture and conversion: A review. Ind. Eng. Chem. Res. 2020, 59, 17612–17631. [Google Scholar] [CrossRef]
  11. Dunstan, M.T.; Donat, F.; Bork, A.H.; Grey, C.P.; Müller, C.R. CO2 Capture at Medium to High Temperature Using Solid Oxide-Based Sorbents: Fundamental Aspects, Mechanistic Insights, and Recent Advances. Chem. Rev. 2021, 121, 12681–12745. [Google Scholar] [CrossRef] [PubMed]
  12. Wang, Q.; Luo, J.; Zhong, Z.; Borgna, A. CO2 capture by solid adsorbents and their applications: Current status and new trends. Energy Environ. Sci. 2011, 4, 42–55. [Google Scholar] [CrossRef]
  13. Tsiotsias, A.I.; Charisiou, N.D.; Yentekakis, I.V.; Goula, M.A. The Role of Alkali and Alkaline Earth Metals in the CO2 Methanation Reaction and the Combined Capture and Methanation of CO2. Catalysts 2020, 10, 812. [Google Scholar] [CrossRef]
  14. Lai, J.Y.; Ngu, L.H.; Hashim, S.S. A review of CO2 adsorbents performance for different carbon capture technology processes conditions. Greenh. Gas Sci. Technol. 2021, 11, 1076–1117. [Google Scholar] [CrossRef]
  15. Martin, D.; Duprez, D. Evaluation of the acid-base surface properties of several oxides and supported metal catalysts by means of model reactions. J. Mol. Catal. A Chem. 1997, 118, 113–128. [Google Scholar] [CrossRef]
  16. An, K.; Li, K.; Yang, C.M.; Brechtl, J.; Nawaz, K. A comprehensive review on regeneration strategies for direct air capture. J. CO2 Util. 2023, 76, 102587. [Google Scholar] [CrossRef]
  17. Ellison, C.; Hoffman, J.; Shekhawat, D. Comparison of microwave and conventional heating for CO2 desorption from zeolite 13X. Int. J. Greenh. Gas Control 2021, 107, 103311. [Google Scholar] [CrossRef]
  18. Jang, G.G.; Kasturi, A.; Stamberga, D.; Custelcean, R.; Keum, J.K.; Yiacoumi, S.; Tsouris, C. Ultra-fast microwave regeneration of CO2 solid sorbents for energy-efficient direct air capture. Sep. Purif. Technol. 2023, 309, 123053. [Google Scholar] [CrossRef]
  19. Fayaz, M.; Shariaty, P.; Atkinson, J.D.; Hashisho, Z.; Phillips, J.H.; Anderson, J.E.; Nichols, M. Using microwave heating to improve the desorption efficiency of high molecular weight VOC from beaded activated carbon. Environ. Sci. Technol. 2015, 49, 4536–4542. [Google Scholar] [CrossRef]
  20. Palma, V.; Barba, D.; Cortese, M.; Martino, M.; Renda, S.; Meloni, E. Microwaves and heterogeneous catalysis: A review on selected catalytic processes. Catalysts 2020, 10, 246. [Google Scholar] [CrossRef]
  21. Bao, C.; Serrano-Lotina, A.; Niu, M.; Portela, R.; Li, Y.; Lim, K.H.; Wang, Q.; Banares, M.A.; Wang, Q. Microwave-associated chemistry in environmental catalysis for air pollution remediation: A review. Chem. Eng. J. 2023, 466, 142902. [Google Scholar] [CrossRef]
  22. Perroud, H.; Miraux, J.; Lions, M.; Caillot, T.; Ferronato, C.; Kaddouri, A.; Meunier, F.C. Combustion of volatile organic compounds in a domestic microwave oven using regenerable sorbent-catalyst combinations. Separ. Purif. Technol. 2024, 330, 125387. [Google Scholar] [CrossRef]
  23. Meunier, F.C.; Dansette, I.; Eng, K.; Schuurman, Y. Differentiating the Reactivity of ZrO2-Bound Formates Formed on Cu/ZrO2 during CO2 Hydrogenation. Catalysts 2022, 12, 793. [Google Scholar] [CrossRef]
  24. CO. Available online: https://webbook.nist.gov/cgi/cbook.cgi?ID=C630080&Units=SI&Type=IR-SPEC&Index=1#IR-SPEC (accessed on 20 November 2023).
  25. CH4. Available online: https://webbook.nist.gov/cgi/cbook.cgi?ID=C74828&Units=SI&Type=IR-SPEC&Index=1#IR-SPEC (accessed on 20 November 2023).
  26. CO2. Available online: https://webbook.nist.gov/cgi/cbook.cgi?ID=C124389&Units=SI&Type=IR-SPEC&Index=1#IR-SPEC (accessed on 20 November 2023).
  27. van de Voort, F.R.; Laureano, M.; Smith, J.P.; Raghavan, G.S.V. A practical thermocouple for Temperature Measurement in Microwave Ovens. Can. Inst. Food Sci. Technol. J. 1987, 20, 279–284. [Google Scholar] [CrossRef]
  28. Kalinke, I.; Kubbutat, P.; Taghian Dinani, S.; Ambros, S.; Ozcelik, M.; Kulozik, U. Critical assessment of methods for measurement of temperature profiles and heat load history in microwave heating processes—A review. Compr. Rev. Food Sci. Food Saf. 2022, 21, 2118–2148. [Google Scholar] [CrossRef]
  29. Li, H.; Rivallan, M.; Thibault-Starzyk, F.; Travert, A.; Meunier, F.C. An operando DRIFTS investigation into the resistance against CO2 poisoning of a Rh/alumina catalyst during toluene hydrogenation. Phys. Chem. Chem. Phys. 2013, 15, 7321–7327. [Google Scholar] [CrossRef]
  30. Meunier, F.C. Pitfalls and benefits of in situ and operando diffuse reflectance FT-IR spectroscopy (DRIFTS) applied to catalytic reactions. React. Chem. Eng. 2016, 1, 134–141. [Google Scholar] [CrossRef]
  31. Zhu, M.; Wachs, I.E. Iron-Based Catalysts for the High-Temperature Water−Gas Shift (HTWGS) Reaction: A Review. ACS Catal. 2016, 6, 722–732. [Google Scholar] [CrossRef]
  32. Hadjiivanov, K.; Lavalley, J.C.; Lamotte, J.; Mauge, F.; Saint-Just, J.; Che, M. FTIR study of CO interaction with Ru/TiO2 catalysts. J. Catal. 1998, 176, 415–425. [Google Scholar] [CrossRef]
  33. Hansen, T.W.; DeLaRiva, A.T.; Challa, S.R.; Datye, A.K. Sintering of Catalytic Nanoparticles: Particle Migration or Ostwald Ripening? Acc. Chem. Res. 2013, 46, 1720–1730. [Google Scholar] [CrossRef]
  34. Rybakov, K.I.; Olevsky, E.A.; Krikun, E.V. Microwave Sintering: Fundamentals and Modeling. J. Am. Ceram. Soc. 2013, 96, 1003–1020. [Google Scholar] [CrossRef]
  35. Wang, X.; Hong, Y.; Shi, H.; Szanyi, J. Kinetic modeling and transient DRIFTS–MS studies of CO2 methanation over Ru/Al2O3 catalysts. J. Catal. 2016, 343, 185–195. [Google Scholar] [CrossRef]
  36. Liu, F.; Jing, G.; Zhou, X.; Lv, B.; Zhou, Z. Performance and Mechanisms of Triethylene Tetramine (TETA) and 2-Amino-2-methyl-1-propanol (AMP) in Aqueous and Nonaqueous Solutions for CO2 Capture. ACS Sustain. Chem. Eng. 2018, 6, 1352–1361. [Google Scholar] [CrossRef]
  37. Hull, A.W. Crystal Structure of Iron. Phys. Rev. 1917, 10, 661–696. [Google Scholar] [CrossRef]
  38. Shull, C.G.; Wilkinson, M.K. Neutron Diffraction Studies of Various Transition Elements. Rev. Mod. Phys. 1953, 25, 100–107. [Google Scholar] [CrossRef]
  39. Fjellvåg, H.; Grønvold, F.; Stølen, S.; Hauback, B. On the Crystallographic and Magnetic Structures of Nearly Stoichiometric Iron Monoxide. J. Solid State Chem. 1996, 124, 52–57. [Google Scholar] [CrossRef]
  40. Dvoryankina, G.G.; Pinsker, Z.G. Electron diffraction pattern investigation of Fe3O4. Dokl. Akad. Nauk SSSR 1960, 132, 110–113. [Google Scholar]
  41. Microwave-Enhanced Chemistry. Fundamentals, Sample Preparation and Applications; Kingston, H.M., Haswell, S.J., Eds.; American Chemical Society: Washington, DC, USA, 1997; p. 772. ISBN 0-8412-3375-6. [Google Scholar]
  42. Buchelnikov, V.D.; Louzguine-Luzgin, D.V.; Xie, G.; Li, S.; Yoshikawa, N.; Sato, M.; Anzulevich, A.P.; Bychkov, I.V.; Inoue, A. Heating of metallic powders by microwaves: Experiment and theory. J. Appl. Phys. 2008, 104, 113505. [Google Scholar] [CrossRef]
  43. Tanaka, M.; Kono, H.; Maruyama, K. Selective heating mechanism of magnetic metal oxides by a microwave magnetic field. Phys. Rev. B 2009, 79, 104420. [Google Scholar] [CrossRef]
  44. McGill, S.L.; Walkiewicz, J.W.; Smyres, G.A. The Effects of Power Level on the Microwave Heating of Selected Chemicals and Minerals. MRS Online Proc. Libr. 1988, 124, 247–252. [Google Scholar] [CrossRef]
Applsci 13 12536 g001
Figure 1. (A) Schematic representation of the catalytic setup used for CO2 trapping and methanation. Gases were fed through mass flow controllers (MFCs). The feed could be sent through a 4-way valve (4-W) to the sorbent and catalytic beds located in the MW oven first or directly into the FT-IR gas analyzer. (B) Picture of the sorption and catalyst beds located in the MW oven. (C) Examples of FT-IR transmission spectra showing the typical signals of methane, CO and CO2 measured with the IR gas cell.
Figure 1. (A) Schematic representation of the catalytic setup used for CO2 trapping and methanation. Gases were fed through mass flow controllers (MFCs). The feed could be sent through a 4-way valve (4-W) to the sorbent and catalytic beds located in the MW oven first or directly into the FT-IR gas analyzer. (B) Picture of the sorption and catalyst beds located in the MW oven. (C) Examples of FT-IR transmission spectra showing the typical signals of methane, CO and CO2 measured with the IR gas cell.
Applsci 13 12536 g001
Applsci 13 12536 g002
Figure 2. Pictures of a physical mixture of 354 mg of SiC and 91 mg of Fe3O4 under a N2 stream after various times under 800 W MW irradiation. A minute-long video of the sequence is available at the following link: https://mycore.core-cloud.net/index.php/s/rhQAXNZGD5O7qq7 (accessed on 2 November 2023).
Figure 2. Pictures of a physical mixture of 354 mg of SiC and 91 mg of Fe3O4 under a N2 stream after various times under 800 W MW irradiation. A minute-long video of the sequence is available at the following link: https://mycore.core-cloud.net/index.php/s/rhQAXNZGD5O7qq7 (accessed on 2 November 2023).
Applsci 13 12536 g002
Applsci 13 12536 g003
Figure 3. (A) Product selectivity at a steady-state under MW irradiation during continuous flow experiments. Catalyst masses used for the various runs (1) 450 mg SiC, (2) mixture of 354 mg SiC + 91 mg Fe3O4, (3) mixture of 354 mg SiC + 91 mg Fe3O4 followed by 25 mg Ru/SiO2 and (4) same as (3). (B) Carbon balance, CO2 conversion and product yields as a function of time under MW irradiation during the second run with SiC + Fe3O4 + Ru/SiO2. Feed: 2% CO2 + 20% H2 in N2, total flow: 50 mL min–1, MW power = 800 W.
Figure 3. (A) Product selectivity at a steady-state under MW irradiation during continuous flow experiments. Catalyst masses used for the various runs (1) 450 mg SiC, (2) mixture of 354 mg SiC + 91 mg Fe3O4, (3) mixture of 354 mg SiC + 91 mg Fe3O4 followed by 25 mg Ru/SiO2 and (4) same as (3). (B) Carbon balance, CO2 conversion and product yields as a function of time under MW irradiation during the second run with SiC + Fe3O4 + Ru/SiO2. Feed: 2% CO2 + 20% H2 in N2, total flow: 50 mL min–1, MW power = 800 W.
Applsci 13 12536 g003
Applsci 13 12536 g004
Figure 4. (A) Operando DRIFTS spectra collected over the used Ru/SiO2 sample under 2% CO2 + 20% H2 in N2 at various temperatures. A KBr spectrum was used as background. (B) Comparison of the operando DRIFTS spectra of the fresh and used Ru/SiO2 samples under 2% CO2 + 20% H2 in N2 at 180 °C. The spectra were normalized to silica overtones to ensure identical optical pathlengths. (C) Corresponding Arrhenius-like plots of the natural logarithm of the rate of methane formation against the reciprocal temperature for both the fresh and used Ru/SiO2 catalysts.
Figure 4. (A) Operando DRIFTS spectra collected over the used Ru/SiO2 sample under 2% CO2 + 20% H2 in N2 at various temperatures. A KBr spectrum was used as background. (B) Comparison of the operando DRIFTS spectra of the fresh and used Ru/SiO2 samples under 2% CO2 + 20% H2 in N2 at 180 °C. The spectra were normalized to silica overtones to ensure identical optical pathlengths. (C) Corresponding Arrhenius-like plots of the natural logarithm of the rate of methane formation against the reciprocal temperature for both the fresh and used Ru/SiO2 catalysts.
Applsci 13 12536 g004
Applsci 13 12536 g005
Figure 5. (A) Configuration used: 350 mg of SiC + 32 mg of ZrO2 were placed in the sorption bed and a mixture made of 354 mg of SiC + 91 mg of Fe3O4 followed by 25 mg of Ru/SiO2 were placed in the catalyst bed. (B) Products released as a function of time under MW. The sample was first exposed to 2% CO2 + 20% O2 in N2 for 5 min, then purged under N2 for 5 min, then left for 5 min under 20% H2 in N2 with a total flow of 50 mL min–1. The MW were then turned on for 5 min still under 20% H2 in N2 with a total flow of 50 mL min–1.
Figure 5. (A) Configuration used: 350 mg of SiC + 32 mg of ZrO2 were placed in the sorption bed and a mixture made of 354 mg of SiC + 91 mg of Fe3O4 followed by 25 mg of Ru/SiO2 were placed in the catalyst bed. (B) Products released as a function of time under MW. The sample was first exposed to 2% CO2 + 20% O2 in N2 for 5 min, then purged under N2 for 5 min, then left for 5 min under 20% H2 in N2 with a total flow of 50 mL min–1. The MW were then turned on for 5 min still under 20% H2 in N2 with a total flow of 50 mL min–1.
Applsci 13 12536 g005
Applsci 13 12536 g006
Figure 6. Amount of carbon released (i.e., sum of CO, CO2 and CH4) by the various elements of the sorbent–catalyst system described in Figure 5A.
Figure 6. Amount of carbon released (i.e., sum of CO, CO2 and CH4) by the various elements of the sorbent–catalyst system described in Figure 5A.
Applsci 13 12536 g006
Applsci 13 12536 g007
Figure 7. CO2 conversion and selectivity to CO and methane obtained over a configuration (Left) including and (Right) lacking a sorption bed. The reaction sequence and catalyst bed are the same as those detailed in Figure 5.
Figure 7. CO2 conversion and selectivity to CO and methane obtained over a configuration (Left) including and (Right) lacking a sorption bed. The reaction sequence and catalyst bed are the same as those detailed in Figure 5.
Applsci 13 12536 g007
Applsci 13 12536 g008
Figure 8. Experiment using a catalyst bed made of a mixture of 111 mg of Fe3O4 + 146 mg of ZrO2 and 28 mg of Ru/SiO2. The sorbent bed was empty. (A) Products released as a function of time under MW. (B) CO2 conversion and selectivity to CO and methane over five consecutive runs. (C) Corresponding production of methane per total mass of the bed. The reaction sequence is the same as that detailed in Figure 5.
Figure 8. Experiment using a catalyst bed made of a mixture of 111 mg of Fe3O4 + 146 mg of ZrO2 and 28 mg of Ru/SiO2. The sorbent bed was empty. (A) Products released as a function of time under MW. (B) CO2 conversion and selectivity to CO and methane over five consecutive runs. (C) Corresponding production of methane per total mass of the bed. The reaction sequence is the same as that detailed in Figure 5.
Applsci 13 12536 g008
Applsci 13 12536 g009
Figure 9. XRD pattern of the (A) fresh and (B) used Fe3O4 material.
Figure 9. XRD pattern of the (A) fresh and (B) used Fe3O4 material.
Applsci 13 12536 g009
Disclaimer/Publisher’s Note: The statements, opinions and data contained in all publications are solely those of the individual author(s) and contributor(s) and not of MDPI and/or the editor(s). MDPI and/or the editor(s) disclaim responsibility for any injury to people or property resulting from any ideas, methods, instructions or products referred to in the content.

Share and Cite

MDPI and ACS Style

Acher, L.; Laredo, T.; Caillot, T.; Kaddouri, A.; Meunier, F.C. Trapping and Methanation of CO2 in a Domestic Microwave Oven Using Combinations of Sorbents and Catalysts. Appl. Sci. 2023, 13, 12536. https://doi.org/10.3390/app132312536

AMA Style

Acher L, Laredo T, Caillot T, Kaddouri A, Meunier FC. Trapping and Methanation of CO2 in a Domestic Microwave Oven Using Combinations of Sorbents and Catalysts. Applied Sciences. 2023; 13(23):12536. https://doi.org/10.3390/app132312536

Chicago/Turabian Style

Acher, Loren, Tristan Laredo, Thierry Caillot, Akim Kaddouri, and Frederic C. Meunier. 2023. "Trapping and Methanation of CO2 in a Domestic Microwave Oven Using Combinations of Sorbents and Catalysts" Applied Sciences 13, no. 23: 12536. https://doi.org/10.3390/app132312536

Note that from the first issue of 2016, this journal uses article numbers instead of page numbers. See further details here.

Article Metrics

Back to TopTop