Investigation on the catalysis of COx-free hydrogen generation from ammonia

Abstract The effects of active component (Ru, Rh, Pt, Pd, Ni, Fe) and support (CNTs, AC, Al 2 O 3 , MgO, ZrO 2 , TiO 2 ) on the catalysis of ammonia decomposition were studied for the generation of CO x -free hydrogen. It was shown that the Ru catalyst using CNTs as support exhibits the highest conversion of NH 3 . The performance can be further improved by modifying CNTs with KOH. According to the results of XRD, TEM, and chemisorption (CO and H 2 as adsorbates) investigations, Ru dispersion is the highest on CNTs. In the range of 2–5 nm, the particle size of Ru on CNTs is the smallest among the supported Ru catalysts; the Ru particles on the metal oxides are in the 3–16 nm range. It seems that larger Ru particles are more active for NH 3 decomposition in terms of TOF. Further investigation on the relationship between support basicity and catalytic activity disclosed that a support material of strong basicity is essential for high catalytic performance. In the N 2 -TPD studies of supported Ru catalysts, desorption was promoted over catalysts of strong basicity, suggesting that N 2 desorption is the rate-determining step in ammonia decomposition. These results implied that it is possible to develop a highly efficient Ru catalyst for NH 3 decomposition by using electron-conductive materials of strong basicity as support.