Carbon nanotubes-supported Ru catalyst for the generation of CO x-free hydrogen from ammonia

• Published in: Catalysis today Vol. 93; pp. 27 - 38
• Main Authors: Yin, S.F., Xu, B.Q., Zhu, W.X., Ng, C.F., Zhou, X.P., Au, C.T.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.09.2004
• Subjects: Ammonia decomposition; Carbon nanotubes; Hydrogen manufacture; Ruthenium catalyst; Ruthenium catalyst; Carbon nanotubes; Ammonia decomposition; Hydrogen manufacture
• ISSN: 0920-5861; 1873-4308
• DOI: 10.1016/j.cattod.2004.05.011

In comparison to Ru catalysts supported on activated carbon (AC), MgO, Al 2O 3, and TiO 2 under similar reaction conditions, Ru catalyst using carbon nanotubes as support (Ru/CNTs) was found to show high NH 3 conversion for the generation of CO x -free hydrogen from NH 3. The modification of the catalyst with KOH leads to a significant improvement in activity, either in term of NH 3 conversion or TOF. The Ru/CNTs catalyst prepared from acetone solvent is more active than that from water solvent, and the use of the former leads to an increase in Ru dispersion and a decrease in residual Cl concentration. The results of H 2-TPD and HRTEM characterization disclosed that the excellent catalytic activity of Ru/CNTs could be ascribed to the high dispersion of Ru particles, and to the high graphitization and high purity of the CNTs material. The residual Cl originated from the RuCl 3 precursor was found to be a strong inhibitor for the decomposition reaction. Once the residual Cl is in the form of KCl, it is difficult to remove. The results of N 2-TPD studies imply that the desorption of N 2 is the rate-determining step, and the modification with KOH leads to a decrease in N 2 desorption temperature and in apparent activation energy of NH 3 decomposition over Ru/CNTs.