Direct Fabrication of Cu(I)/4A Assisted with a Molecular Complex toward High-Efficiency CO-Selective Adsorption from H2
The cuprous-ion-based zeolites constructed by introducing Cu(I) adsorption active sites into zeolite Linde Type A have proved to be efficient in carbon monoxide (CO) adsorption with high selectivity and capacity. However, how to directly fabricate zeolite 4A containing copper species and effectively overcome cuprous ion aggregation during the preparation process is still a challenge. Here, we propose an efficient fabrication method to synthesize highly dispersed Cu(I)-modified octahedral zeolite 4A adsorbents using a molecular complex formed by a hydrogel with a silicon/aluminum molar ratio of 1:1, copper ions, and tetramethylammonium hydroxide (TMAOH) as the template. Zeolite 4A containing copper ions was directly obtained by incorporating the precursor of cuprous ions into the confined space between zeolite 4A channel walls and TMAOH. The target zeolite Cu(I)/4A adsorbent with highly dispersed Cu(I) was constructed after introducing VCl3 as the reducing agent via the solid-state dispersion method during the process of removing the template. In comparison with pristine zeolite 4A, a bimodal microporous pore size distribution was observed in as-synthesized Cu(I)/4A. Cu(I)/4A exhibited an enhanced static (1.15 mmol/g) and dynamic (0.0016 mmol g−1) CO adsorption capacity, respectively, at 25 °C and 1 bar. Moreover, Cu(I)/4A displayed a lower H2 adsorption capacity under identical conditions. Through calculation using the ideal adsorption solution theoretical (IAST) equation, the CO selectivity from the CO/H2 mixture on Cu(I)/4A attained ca. 16.95. Therefore, Cu(I)/4A with highly dispersed Cu(I) was successfully fabricated, and its excellent CO adsorption selectivity and capacity enable it to be potentially applied for the actual deep separation of CO/H2.
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