Highly efficient Pd–ZnO catalyst doubly promoted by CNTs and Sc2O3 for methanol steam reforming

Authors: Lu Yang, Guo-Dong Lin, Hong-Bin Zhang

Abstract:
A type of Pd–ZnO catalyst doubly promoted by CNTs and Sc₂O₃ for methanol steam reforming (MSR) was developed, and displayed excellent activity and operation stability for the selective formation of H₂ and CO₂. Over a Pd_0.15Zn₁Sc_0.067–10%CNTs catalyst under the reaction conditions of 0.5 MPa and 548K, the STY(H2) can maintain stable at the level of 1.56 mol h⁻¹ g⁻¹ at 75 h after the reaction started, which was 1.7 times that of the corresponding (CNTs and Sc)-free counterpart Pd_0.15Zn₁. Characterization of the catalyst revealed that the highly conductive CNTs could promote hydrogen spillover from the PdZn/ZnOsites to the CNTs adsorption-sites, and then combine to form H₂(a), followed by desorbing to H₂(g), which would help increase the rate of a series of surface dehydrogenation reactions in the MSR process. The pronounced modification action of Sc3+ may be due to the high solubility of  Sc₂O₃ in ZnO lattice. Solution of a small amount of Sc₂O₃ in ZnO lattice resulted in the formation of Schottky defects in the form of cationic vacancies at the surface of ZnO, where the (PdZn)^0–Pd²⁺ clusters can be better stabilized through the Pd²⁺ accommodated at the surface vacant cation-sites. This would be conducive to inhibiting the sintering of the catalytically active (PdZn)⁰ nanoparticles, and thus, markedly prolonging the life of the catalyst.

Keywords:
MWCNTs
Pd–ZnO catalyst
Sc₂O₃
Methanol steam reforming

Published in: Applied catalysis A: General  (Volume 455, Pages 1-266, 30 March 2013)

Publisher: Elsevier

ISSN Information: 0926-860X

Highly efficient Pd–ZnO catalyst doubly promoted by CNTs and Sc2O3 for methanol steam reforming

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