Plasma Catalytic Conversion of Nitrogen and Hydrogen to Ammonia Over Silico Alumino Phosphate (SAPO) Zeolites

• Published in: Plasma chemistry and plasma processing Vol. 44; no. 3; pp. 1357 - 1368
• Main Authors: Gorky, Fnu, Nambo, Apolo, Carreon, Moises A., Carreon, Maria L.
• Format: Journal Article
• Language: English
• Published: New York Springer US 01.05.2024
• Subjects: Characterization and Evaluation of Materials; Chemistry; Chemistry and Materials Science; Classical Mechanics; Inorganic Chemistry; Mechanical Engineering; Original Paper; Non-thermal plasma; Ammonia synthesis; SAPO crystals; Plasma catalysis; Ammonia adsorption
• ISSN: 0272-4324; 1572-8986
• DOI: 10.1007/s11090-023-10397-w

Herein, we demonstrate the catalytic activity of microporous Silico Alumino Phosphate (SAPOs) crystals for the assisted plasma synthesis of ammonia. SAPOs can aid as effective catalysts for the synthesis of ammonia via non-thermal plasma using an atmospheric dielectric barrier discharge (DBD) reactor. We studied three prototypical zeolites having crystallographic limiting pore apertures of 3.4 Å (SAPO-56), 3.8 Å (SAPO-34) and 3.9 Å (SAPO-11). We describe a fundamental insight on the effect of the Si/Al ratio and the pore size on ammonia synthesis rate for the different SAPOs. The resultant SAPO-11 displayed ammonia synthesis rates as high as 0.19 micromoles NH 3 / min m 2 at 20 watts, approximately 1.5 times better compared to other SAPOs. The results indicate that ammonia synthesis is promoted by a lower Si/Al ratio (< 0.25) of the SAPO. Moreover, we observed that SAPO-34 (3.8 Å) and SAPO-11 (3.9 Å) which allow diffusion of N 2 (3.6 Å) in to the pores lead to a higher ammonia yield. The lower intensity observed in optical emission spectroscopy (OES) for SAPO-34 suggests the diffusion of plasma activated species onto the surface and the pores. Proving the importance of porosity in plasma catalysis. Graphical Abstract