Catalytic ammonia decomposition to COx-free hydrogen over ruthenium catalyst supported on alkali silicates

Abstract

• The oxygen vacancies (Vo) would appear in Ru/Ru/A 2 SiO 3 (A=Li, Na and K) after H 2 reduction. • The formation Vo would induce the production of EMSI effect and higher Ru dispersion. • A 2 SiO 3 (A=Li, Na and K) can transfer their electron to Ru particle through EMSI effect. • K 2 SiO 3 is firstly reported to be an effective support as Ru catalyst for NH 3 decomposition. A series of alkali metal silicates A 2 SiO 3 (A = Li, Na and K) were synthesized by a sol–gel method route and employed as support for Ru nanoparticles to catalyze NH 3 decomposition. The NH 3 conversion can be ranked as the order of Ru/K 2 SiO 3 > Ru/Na 2 SiO 3 > Ru/Li 2 SiO 3 > Ru/SiO 2 at the same conditions, and Ru/K 2 SiO 3 displays the highest NH 3 conversion of 60.5% with the TOF H2 of 2.03 s −1 under the weight hourly space velocity (GHSV) of 30,000 mL.g cat -1 .h −1 at 450 o C. The combination results of different characterization indicate that the formation of alkali metal silicates can increase the strength and number of basic sites, and the strong electronic metal-support interaction (EMSI) would appear between Ru particles and oxygen vacancies in A 2 SiO 3 structure at reduction conditions. The presence of EMSI can result in the higher Ru dispersion and enhanced electronic density of Ru particles over A 2 SiO 3 , greatly facilitating the decomposition of NH 3 to CO x -free hydrogen.