Synthesis of DNL-6 with a High Concentration of Si(4Al) Environments and its Application in CO2 Separation

The synthesis of DNL-6 with a high concentration of Si(4Al) environments [Si/(Si+Al+P)=0.182mol, denoted as M-DNL-6] is demonstrated. This represents the highest reported concentration of such environments in silicoaluminophosphate (SAPO) molecular sieves. Adsorption studies show that the high Si(4Al) content in M-DNL-6, with an increased number of BrOnsted acid sites in the framework, greatly promotes the adsorption of CO2. M-DNL-6 exhibits a large CO2 uptake capacity of up to 6.18mmolg1 at 273K and 101kPa, and demonstrates high ratios of CO2/CH4 and CO2/N2 separation. From breakthrough and cycling experiments, M-DNL-6 demonstrates the ability to completely separate CO2 from CH4 or N2 with a dynamic capacity of approximately 8.0wt% before breakthrough. Importantly, the adsorbed CO2 is easily released from the adsorbent through a simple gas purging operation at room temperature to regain 95% of the original adsorption capacity. These results suggest that M-DNL-6 can be used as a potential adsorbent for CO2 capture in pressure swing adsorption processes.