Tunability of ammonia adsorption over NaP zeolite

Abstract

Porous adsorbents represent an environmentally-friendly and cost-effective alternative for NH 3 separation from H 2 and N 2 , particularly in the highly energy intensive Haber-Bosch process. Zeolites are deep-rooted in the world of chemical processes due to their chemical, structural, thermal stabilities, and wide variety of pore architectures. Zeolite NaP with a limiting pore of ~2.9 Å, is highly appealing for small molecule separations, in particular for potentially sieving NH 3 from N 2 and H 2 . Herein, we demonstrate the modulable and selective ammonia adsorption over nitrogen and hydrogen of Zeolite NaP. The use of different aluminum precursors led to tunable ammonia uptakes. Zeolite morphology, acidity, crystallinity, and textural properties greatly influenced the observed NH 3 uptakes. Zeolite NaP synthesized using aluminum isopropoxide, displayed high adsorption selectivities of NH 3 /H 2 = 152, and NH 3 /N 2 = 50. Aluminum hydroxide produced a highly crystalline zeolite NaP sample displaying high NH 3 uptake of 8.47 mmol/g 273K. Mesoporosity played an important role on the NH 3 uptake over zeolite NaP. A larger pore NaY zeolite was synthesized, and used to validate the ammonia sieving effectiveness of zeolite NaP. • NaP zeolite was prepared using various aluminum sources, and sodium silicate as a silica source. • Zeolite morphology, and textural properties vary with aluminum source. • NH 3 adsorption, and adsorption selectivity was tunable depending on aluminum source. • NaP displayed high adsorption selectivities of NH 3 /H 2 = 152, and NH 3 /N 2 = 50.