Highly Stable and Low-Cost Pure-Silica Zeolite with Narrow 8-Ring Pores: Unlocking Exclusive Carbon Dioxide Recognition from Hydrocarbons.
basic_science · Level V
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- Record sourced from PubMed, PMID 41622898.
- Also identified by DOI 10.1021/acsnano.5c19160.
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Abstract
The similar molecular sizes and physicochemical properties of carbon dioxide (CO<sub>2</sub>) and hydrocarbons like methane (CH<sub>4</sub>), acetylene (C<sub>2</sub>H<sub>2</sub>), ethylene (C<sub>2</sub>H<sub>4</sub>), and ethane (C<sub>2</sub>H<sub>6</sub>) make their separation a major industrial challenge. Here, we develop a low-cost, easily regenerable, pure-silica zeolite adsorbent "Instituto de Tecnología Química-55" (ITQ-55) capable of exclusively recognizing CO<sub>2</sub> over these hydrocarbons. Guided by three-dimensional electron diffraction (3D ED) and density functional theory calculations, we identified commercially available and cost-effective diquaternary ammonium compounds as alternative organic structure-directing agents (OSDAs), partially replacing the previously expensive and complex ones for the synthesis of pure-silica ITQ-55. The calcined ITQ-55 features narrow 8-ring pores that enable selective CO<sub>2</sub> adsorption while minimizing the uptake of CH<sub>4</sub>, C<sub>2</sub>H<sub>2</sub>, C<sub>2</sub>H<sub>4</sub>, and C<sub>2</sub>H<sub>6</sub>. Notably, the uptake ratio of CO<sub>2</sub>/C<sub>2</sub>H<sub>2</sub> is much higher than that of currently reported CO<sub>2</sub>-selective adsorption materials. Dynamic breakthrough tests reveal that ITQ-55 exhibits excellent separation performance for CO<sub>2</sub>/C<sub>2</sub>H<sub>2</sub>, CO<sub>2</sub>/CH<sub>4</sub>, CO<sub>2</sub>/C<sub>2</sub>H<sub>4</sub>, and CO<sub>2</sub>/C<sub>2</sub>H<sub>6</sub>. In addition, the spent ITQ-55 adsorbent can be easily regenerated at 80 °C. Furthermore, theoretical calculations confirm that the separation mechanism of ITQ-55 for CO<sub>2</sub>/hydrocarbons is a size-exclusion mechanism.