Synthesis of SAPO-34 with alkanolamines as novel templates and their application for CO2 separation

• SAPO molecular sieves are synthesized with alkanolamines as the novel template.
• The obtained SAPO-34 exhibits good CO2 adsorption/separation ability.
• The CO2 uptake is in line with the acid concentration of SAPO-34 adsorbent.

Alkanolamines are used for the first time as both the solvent and template to explore the syntheses of SAPO molecular sieves. Diglycolamine (DGA) and diisopropanolamine (DIPA) are found to act as novel structure-directing agent for the synthesis of SAPO-34, and N-methyldiethanolamine leads to the crystallization of SAPO-44. The obtained SAPO-34s are well characterized and investigated as adsorbents for selective separation of CO2 from N2 and CH4. A close relationship between the acid concentration of SAPO-34 and CO2 adsorption capacity has been revealed. SAPO-34-DGA with the highest acid concentration (sample D4) exhibits the best CO2 adsorption capacity and high CO2-over-N2 selectivity. Breakthrough experiments are further carried out based on sample D4, which shows an excellent dynamic preferential adsorption ability for CO2 (∼8.2 wt%) from both CO2/N2 and CO2/CH4 mixtures (298 K). These results demonstrate that SAPO-34-DGA could be a promising adsorbent for the CO2 capture.

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