Chlorine‐Tolerant Ruthenium Catalyst Derived Using the Unique Anion‐Exchange Properties of 12 CaO⋅7 Al2O3 for Ammonia Synthesis. Issue 15 (26th June 2017)

• Record Type: Journal Article
• Authors: Li, Jiang; Kitano, Masaaki; Ye, Tian‐Nan; Sasase, Masato; Yokoyama, Toshiharu; Hosono, Hideo
• Is Part Of: ChemCatChem. Volume 9:Issue 15(2017)
• Page Start: 3078
• Page End: 3083
• Publication Date: 2017-06-26
• Subjects: ammonia synthesis -- chlorine -- hydrothermal synthesis -- ruthenium -- supported catalysts; Catalysis -- Periodicals; 541.39505
• DOI: 10.1002/cctc.201700353
• Languages: English
• ISSNs: 1867-3880

Abstract

Abstract: Poisoning is defined as deactivation by the strong adsorption of, usually, impurities on active sites, which is a serious problem in many important catalytic processes. For example, the activity of Ru catalysts is significantly degraded by Cl in ammonia synthesis because of its electron‐withdrawing properties. Here we demonstrate that 12 CaO⋅7 Al2 O3 with subnanometer‐sized cages prevents the poisoning of a Ru catalyst by Cl − ions in ammonia synthesis. Conventional supported Ru catalysts exhibit a negligible activity if a tiny amount of Cl − ions remain on the catalyst surface. In contrast, the catalytic activity of Ru/C12A7 is not influenced by Cl − ions even though the amount of Cl in Ru/C12A7 is one order of magnitude higher than that in the conventional Ru catalysts. The Cl resistance of Ru/C12A7 is attributed to the unique anion‐exchange properties of C12A7; that is, the Cl − ions are trapped preferentially in the positively charged subnanometer‐sized cages of C12A7 instead of OH − ions under ammonia synthesis conditions. Abstract : No chlorine poisoning : C12A7‐supported Ru catalysts prepared hydrothermally from RuCl3 and Ru3 (CO)12 precursors show the same ammonia synthesis activity, whereas for conventional Ru catalysts such as Ru/MgO, the RuCl3 precursor provides a much lower activity than that from Cl‐free precursors. The excellent Cl‐tolerant feature is caused by the anion‐exchange properties of C12A7.