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

Abstract

The synthesis of DNL-6 with a high concentration of Si (4 Al) environments [Si/(Si+Al+P)=0.182 mol, 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 (4 Al) content in M-DNL-6, with an increased number of Brønsted acid sites in the framework, greatly promotes the adsorption of CO(2). M-DNL-6 exhibits a large CO(2) uptake capacity of up to 6.18 mmol g(-1) at 273 K and 101 kPa, and demonstrates high ratios of CO(2)/CH(4) and CO(2)/N(2) separation. From breakthrough and cycling experiments, M-DNL-6 demonstrates the ability to completely separate CO(2) from CH(4) or N(2) with a dynamic capacity of approximately 8.0 wt % before breakthrough. Importantly, the adsorbed CO(2) 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 CO(2) capture in pressure swing adsorption processes.

Organic‐Free Synthesis of Silicoaluminophosphate Molecular Sieves

“…[12] As such, it is not surprising that the Si fraction of K-SAPO-MER increases with increasing Si concentration in the gel (Tables 1a nd 2). [12] As such, it is not surprising that the Si fraction of K-SAPO-MER increases with increasing Si concentration in the gel (Tables 1a nd 2).…”

Interaction of water with (silico)aluminophosphate zeotypes: a comparative investigation using dispersion-corrected DFT

“…In addition to AlPO-34/SAPO-34, 36,37 AlPO-17/SAPO-17, [37][38][39][40] and AlPO-18/SAPO-18, 38,41,42 pairs where either the AlPO or the SAPO system has already been proposed as adsorbent for heat transformation applications, 5,6,[12][13][14][15][16]20 three other systems are evaluated: AlPO-GIS/SAPO-43, 40,43,44 AlPO-AFX/ SAPO-56, 45 and AlPO-RHO/SAPO-RHO. 9,46,47 With the exception of the last two systems, which so far have only been reported as SAPO materials, not as pure aluminophosphates, all other materials have been successfully synthesised in both AlPO and SAPO form. In all six structures considered, the pores are connected through eight-ring windows.…”

Organic‐Free Synthesis of Silicoaluminophosphate Molecular Sieves

“…[12e] This is expected because the alkali metal ions used as an ISDAa re much smaller than monoquaternary OSDA cations.I ti sr emarkable that although the synthesis of such high Si-containing SAPO materials has long received much attention, all previous studies were confined to the use of OSDAs. [12] As such, it is not surprising that the Si fraction of K-SAPO-MER increases with increasing Si concentration in the gel (Tables 1a nd 2). An interesting observation is that while K-SAPO-MER(2) with Si/(Si + Al + P) = 0.31 possesses 10.5 K + ions per 32 T-atoms,K -SAPO-MER (7) with the highest Si/(Si + Al + P) ratio (0.53) among the MER-type SAPO materials prepared here has the smallest number (9.1) of K + ions per 32 T-atoms.T his indicates the existence of amaximum framework charge density,suggesting changes in the prevailing Si substitution mechanism during K-SAPO-MER syntheses.Infact, we suspected that K-SAPO-MER(2) might have an already large number of extra-framework cations per unit cell and thus no microporosity.T hus we intentionally increased the Si concentration in the SAPO gel in an attempt to generate Si(0Al) units in the K-SAPO-MER framework and thus to decrease the number of extra-framework cations per unit cell.…”

“…They are also compared with the chemical compositions of selected known SAPO materials. [12] It can be seen that all of our materials possess unusually high Si fractions (Si/(Si + Al + P) = 0.31-0.54). In particular, the Si/(Si + Al + P) ratios (0.53 and 0.54, respectively) of K-SAPO-MER (7) and Na-SAPO-GIS(15) are even higher than the ratio (0.50) of SAPO-20C with the SOD topology,w hich is the highest among the previously reported SAPO molecular sieves.…”