Synthesis Strategies for Ultrastable Zeolite GIS Polymorphs as Sorbents for Selective Separations

• Published in: Chemistry : a European journal 2016-11, Vol.22 (45), p.16078-16088
• Main Authors: Oleksiak, Matthew D., Ghorbanpour, Arian, Conato, Marlon T., McGrail, B. Peter, Grabow, Lars C., Motkuri, Radha Kishan, Rimer, Jeffrey D.
• Format: Article
• Language: English
• Subjects: Adsorbents; Adsorption; Carbon dioxide; Carbon sequestration; Catalysis; Chemical synthesis; Chemistry; crystallization; Crystals; Density; Density functional theory; Drug delivery; Drug delivery systems; Functional anatomy; gas/vapor adsorption; Gases; Geographic information systems; Impurities; Light effects; Materials selection; Mathematical analysis; organic free; Physicochemical properties; Satellite navigation systems; Separation; Sorbents; Synthesis; Thermal stability; Topology; zeolite; Zeolites
• ISSN: 0947-6539; 1521-3765
• DOI: 10.1002/chem.201602653

Designing zeolites with tunable physicochemical properties can substantially impact their performance in commercial applications, such as adsorption, separations, catalysis, and drug delivery. Zeolite synthesis typically requires an organic structure‐directing agent to produce crystals with specific pore topology. Attempts to remove organics from syntheses to achieve commercially viable methods of preparing zeolites often lead to the formation of impurities. Herein, we present organic‐free syntheses of two polymorphs of the small‐pore zeolite P (GIS), P1 and P2. Using a combination of adsorption measurements and density functional theory calculations, we show that GIS polymorphs are selective adsorbents for H2O relative to other light gases (e.g., H2, N2, CO2). Our findings refute prior theoretical studies postulating that GIS‐type zeolites are excellent materials for CO2 separation/sequestration. We also show that P2 is significantly more thermally stable than P1, which broadens the operating conditions for GIS‐type zeolites in commercial applications and opens new avenues for exploring their potential use in processes such as catalysis. Subtle twist: Two zeolite GIS‐type polymorphs, P1 and P2, differ by a slight margin (see figure), yet display markedly different properties (e.g., thermal stability). Experimental and computational studies indicate that both GIS polymorphs are excellent sorbents for dehydration processes, but are not viable sieves for CO2 separation, as proposed in prior theoretical studies.