Abstract
Artificial carbon dioxide capture is an alternative method to remove the carbon dioxide already accumulated in the atmosphere as well as to stop its release at its large-scale emission points at the source, such as at power plants. However, new adsorbents are needed to make the approach feasible. For this purpose, in this study, hierarchical mesoporous-microporous chabazite-type zeolites were synthesised by applying a dual-templating method. The microporous zeolite structure-directing agent N,N,N-trimethyl-1-adamantanammonium hydroxide was combined with an organosilane mesopore-generating template, 3-(trimethoxysilyl)propyl octadecyl dimethyl ammonium chloride. Materials were characterised for their structural and textural properties and tested for their carbon dioxide capture capacity both in their original sodium form and in their proton-exchanged form by means of breakthrough curve analysis and sorption isotherms. The influence of template ratios on their structure, carbon dioxide capture, and capacity have been identified. All mesoporous materials showed fast adsorption-desorption kinetics due to a reduction in the steric limitations via the introduction of a meso range network of pores. The hierarchical zeolites are recyclable with a negligible loss in crystallinity and carbon dioxide capture capacity, which makes them potential materials for larger-scale application.
Highlights
In recent years, there has been an increasing effort to reduce levels of carbon dioxide (CO2) emissions to the atmosphere
The X-ray diffraction (XRD) patterns of SSZ-13 samples (Figure 1) can be seen to exhibit characteristic peaks at 9.40◦, 20.45◦, and 30.40◦, which are directly comparable to the IZA database obtained data for Chabazite-type materials
Microporous SSZ-13 materials are denoted as x-SSZ-13-micro-y or x-SSZ-13-meso-w depending on whether they are conventional microporous zeolites or mesoporous zeolites, where x denotes the cation in the framework, Na+ or H+, y is the silicon to aluminium ratio, 20 or 40, and w is the template ratio: 0.2, 0.4, 0.6, or 0.8
Summary
There has been an increasing effort to reduce levels of carbon dioxide (CO2) emissions to the atmosphere. Pham et al [17] tested microporous SSZ-13 with Si/Al = 12 for CO2 adsorption and noted that sodium and lithium forms could capture approximately 4 mmol·g−1, with potassium and proton analogues reaching adsorption capacities of 3.60 and 3.30 mmol·g−1, respectively These values are comparable to those obtained in the literature for low-silica zeolite adsorbents [20,21], highlighting the potential of chabazite for this application. The need for a highly regenerable solid sorbent and fast sorption kinetics stems from the requirement that large amounts of the adsorbent material are required due to the large amounts of CO2 in the flue gas [22] In essence, this means that only processes with very short cycle times will be viable at this scale, as longer durations will lead to growing costs to meet the necessary practical efficiencies. The hierarchical mesoporous zeolites were found to be recyclable, and their carbon dioxide capture capacity is retained, which proves their potential for large-scale application
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