The urgency to address global climate change, fueled by greenhouse gas emissions, is intensifying. Rapidly increasing in atmospheric CO₂ levels is the main concern. Current predictions show a substantial increase in CO₂ emissions, which could lead to a rise in global temperatures by 1.4 to 6.1 C by the end of the century [1]. The development of efficient gas–solid contactors is crucial for advancing CO₂ capture technologies, particularly in applications such as post-combustion carbon capture and direct air capture (DAC). Monolithic structures present an appealing alternative to conventionally prepared catalyst pellets or powders, boasting several superior properties. They excel in mass transfer efficiency, maintain low pressure drop, exhibit thermal stability, and demonstrate robust mechanical strength compared to traditional catalyst pellets or powders [2]. Monoliths are basically uniform blocks, consisting of parallel channels that can be extruded into different shapes and sizes. Wash coating by slurry coating method and in situ synthesis are the most industrially known processes applied to the monolith to improve surface properties to increase desorption capacity.

Microwave-assisted heating (MW) is one of the emerging technologies for post combustion carbon capture and DAC applications. It is claimed to be energy efficient, time-saving, and improves throughput compared to conventional processing systems, due to concentration heat capacity [3].

In this study, a cordierite monolith wash coated with Zeolite 13X has been used for CO₂ capture of post combustion under mono-mode microwave conditions. The wash coating process involved formulating a suspension of Zeolite 13X and deionized water, followed by immersion of mini monoliths, air drying, and calcination. For zeolite synthesis, a synthesis solution was prepared and introduced with cordierite mini monoliths into an autoclave for crystallization. The in-situ synthesis method yielded monoliths with superior characteristics compared to slurry-coated counterparts, showcasing enhanced mechanical stability and homogeneous zeolite layers, thus offering promising prospects for practical CO₂capture applications.

Microwaves provide precise control, allowing for accurate temperature regulation and uniform heating throughout the sorbent material. The monolithic sorbents were thoroughly characterized and compared based on different coating layers to investigate its effect on the desorption characteristics. Adsorption and microwave desorption experiments were also tested varying two key parameters: regeneration temperature and microwave power. Based on the comparison of the two different methods investigated under experimental conditions, like microwave power and reactor temperature, impact CO₂ adsorption on slurry-coated monoliths.

References

[1] X. Shi, H. Xiao, H. Azarabadi, J. Song, X. Wu, X. Chen, K.S. Lackner, Sorbents for the Direct Capture of CO2 from Ambient Air, Angewandte Chemie International Edition, 59(18) (2020) 6984-7006.

[2] T.A. Nijhuis, A.E.W. Beers, T. Vergunst, I. Hoek, F. Kapteijn, J.A. Moulijn, Preparation of monolithic catalysts, Catalysis Reviews, 43(4) (2001) 345-380.

[3] I.J. Siddique, A.A. Salema, E. Antunes, R. Vinu, Technical challenges in scaling up the microwave technology for biomass processing, Renewable and Sustainable Energy Reviews, 153 (2022) 111767.