Prominent enhancement of Mn or Co addition on the performance of Cu-Ce-O catalyst used for H2 production via dimethyl ether steam reforming

The Mn or Co promoted Cu-Ce-O catalysts were prepared by citric acid complexation, and used for the catalytic production of hydrogen via the route of dimethyl ether steam reforming (DME SR). Multiple techniques such as X-ray diffraction (XRD), X-ray absorption fine structure (XAFS), X-ray photoelectron spectra (XPS), temperature-programmed reduction by H-2 (H-2-TPR), CO-pulse chemisorption and thermal gravimetry/differential thermal analysis (TG/DTA) were employed for catalyst characterization. It is revealed by the results of XRD, XPS and XAFS that in the spent catalysts the copper species mainly exist as Cu-0 and Cu+. The addition of Co or Mn could enhance both the dispersion and the reducibility of copper species, significantly increasing the DME conversion and H-2 yield at the temperature of 400 degrees C or below. At higher temperature, the H-2 yield over Cu-Ce-Co-O is almost the same as that for Cu-Ce-O, due to the side reactions of CH3OH decomposition and/or DME steam reforming to syngas. Addition of Mn to Cu-Ce-O can increase both DME conversion and H-2 yield in the whole temperature region of 300-450 degrees C. Much higher CO2 selectivity is achieved over the Mn promoted catalyst. XPS and CO-pulse chemisorption results indicate that Cu-Ce-Mn-O catalyst contains more Cu+ species, which determines its novel catalytic performance including higher DME conversion and higher H-2 yield. (C) 2011 Elsevier B.V. All rights reserved.