Preparation of Ru/ZrO₂ Catalysts by NaBH₄ Reduction and Their Catalytic Activity for NH₃ Decomposition To Produce H₂

Abstract

ZrO 2 -supported Ru catalysts were prepared by an impregnation method and by NaBH 4 reduction from RuCl 3 •3H 2 O and a commercial ZrO 2 support. The catalyst prepared by NaBH 4 reduction showed high activity (around 60%) at 673 K for NH 3 decomposition, whereas the catalyst prepared by the impregnation method exhibited low activity (10%) under the same reaction conditions. X-ray fluorescence spectrometry indicated that the catalyst prepared by NaBH 4 reduction was free of Cl, whereas the catalyst prepared by the impregnation method contained more than 5 wt % Cl from the Ru precursor. This was main factor that caused the differences in catalytic activity. In addition, the Ru/ZrO 2 catalyst prepared by NaBH 4 reduction was active for NH 3 decomposition without H 2 pretreatment, and its activity was slightly higher than that of the catalyst pretreated with H 2 . The transmission electron microscopy and H 2 pulse chemical adsorption results demonstrated that the Ru metal particle size also affected the activity.

Effect of Alkali Metal Addition to a Ru/CeO₂ Catalyst Prepared by NaBH₄ Reduction on the Catalytic Performance for H₂ Production via NH₃ Decomposition

“…us, catalysts that do not require H 2 pretreatment before NH 3 decomposition are highly desirable. As reported previously (Furusawa et al, 2016b), a Ru/ ZrO 2 catalyst prepared by NaBH 4 reduction catalyzed NH 3 decomposition without H 2 pretreatment because Ru metal was formed by NaBH 4 reduction. erefore, the as-prepared Ru/ZrO 2 catalyst or the Ru/ZrO 2 catalyst treated with Ar (773 K, 1 h) could be used without H 2 pretreatment.…”

“…e catalysts were characterized as described in our previous study (Furusawa et al, 2016b). Brie y, X-ray uorescence spectrometry (XRF; ZSX primus II, Rigaku Co.) was employed to determine the quantities of Ru and Cl in the catalysts.…”

“…e Ru/CeO 2 , Ru/ZrO 2 , and Ru/MgO catalysts exhibited a high activity for NH 3 decomposition. Consequently, we investigated the Ru/ZrO 2 catalyst further (Furusawa et al, 2016b) and found that the Ru/ZrO 2 catalyst prepared by NaBH 4 reduction catalyzed NH 3 decomposition without H 2 pretreatment. e characterization results indicated that the size of the Ru metal particles formed on the catalyst in uenced its activity, and the Ru metal particles were redispersed during the NH 3 decomposition.…”

Highly Active Ruthenium Catalyst Supported on Barium Hexaaluminate for Ammonia Decomposition to COx-Free Hydrogen

“…Compared with the result of CO chemisorption in Table , the Ru particles average sizes derived from CO chemisorption are obviously bigger than that observed from TEM, which often can be explained by the fact that the residual of Cl – will restrain the chemisorption of CO, leading to the overly high valuation for Ru particles . Though the residual of Cl – would attenuate the catalytic performance for the electron-withdrawing effect of Cl – to Ru, RuCl 3 precursor is still thought to be the best alternative for its cheapness and excellent solubility in water . Additionally, the Ru particles size and shape are also thought to have a strong connection with the catalytic performance for NH 3 decomposition because this reaction is a typical structure-sensitive reaction.…”

“…49 Though the residual of Cl − would attenuate the catalytic performance for the electron-withdrawing effect of Cl − to Ru, RuCl 3 precursor is still thought to be the best alternative for its cheapness and excellent solubility in water. 50 Additionally, the Ru particles size and shape are also thought to have a strong connection with the catalytic performance for NH 3 decomposition because this reaction is a typical structuresensitive reaction. Garci ́a-Garci ́a et al 51 found that the socalled B5 sites are responsible for the real active sites available to ammonia decomposition, and Ru particles with a diameter The morphology of BHA and Ru particles supported on BHA after reduction at 500 °C for 2.0 h are shown in Figure 6.…”