Alkali hydroxide-modified Ru/γ-Al2O3 catalysts for ammonia decomposition

• Ru/γ-Al2O3 catalysts are modified with alkali hydroxides to enhance ammonia decomposition.
• Analysis by solid state NMR and XRD measurements showed basic modification of the support by aluminate formation.
• LiOH modification with very high loadings showed the best results (6.5 times higher activity compared to unmodified catalyst) because of a high concentration of basic sites and a partial preservation of the support porosity.

We herein present an easy approach to increase drastically the catalytic activity of Ru/γ-Al2O3 catalysts in ammonia decomposition by surface modification with alkali hydroxides. The best activities have been achieved by a catalyst modification with lithium hydroxide in a Li/Al ratio of 1.7. In contrast, coatings with potassium and caesium hydroxide caused mass transfer limitations in the catalytic material already at low amounts (ratios alkali/Al <0.2–0.3). MAS ssNMR and XRD studies indicate the in-situ formation of alkali aluminates resulting in a basic modification of the support.

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