Improved Performance of Au/Fe 2 O 3 Catalysts Promoted with ZrO 2 and Nb 2 O 5 in the WGS Reaction under Hydrogen-rich C

  • PDF / 314,585 Bytes
  • 6 Pages / 593.972 x 792 pts Page_size
  • 49 Downloads / 175 Views

DOWNLOAD

REPORT


Catalysis Letters Vol. 108, Nos. 3–4, May 2006 ( 2006) DOI: 10.1007/s10562-006-0047-5

Improved performance of Au/Fe2O3 catalysts promoted with ZrO2 and Nb2O5 in the WGS reaction under hydrogen-rich conditions Fengli Zhang,a Qi Zheng,a,* Kemei Wei,a Xingyi Lin,a Hanhui Zhang,b Jinwei Li,a and Yanning Caob a

National Engineering Research Center of Chemical Fertilizer Catalysts, Fuzhou University, Gongye Road 523, Fuzhou 350002, China b Department of Chemistry, Fuzhou University, Fuzhou, Fujian 350002, China

Received 10 January 2006; accepted 21 February 2006

Effect of addition of the ZrO2 and Nb2O5 promoters on the activity and stability of the Au/Fe2O3 catalysts in the WGS reaction under hydrogen-rich conditions was studied. Results showed that this new catalyst possesses enhanced activity and stability under conditions common in fuel processors. Its CO conversion almost reached the maximum value 99% at 200 C and maintained better stability compared with unmodified samples within 50 h on-stream. Detailed characterization including BET, XRD, HRTEM, XPS, XRF and H2-TPR revealed that ZrO2 and Nb2O5 acted as structural promoters and a strong interaction between ZrO2 and Nb2O5 existed. The enrichment of Zr and Nb on the surface kept the gold and magnetite particles apart delaying sintering. More active gold sites, larger surface area and smaller magnetite particles were the main reasons for the enhanced performance. KEY WORDS: gold; iron oxide; zirconium oxide; niobium oxide; water–gas shift; promoters.

1. Introduction The water gas shift (WGS) reaction, CO + H2O M CO2 + H2 is an industrially important route to H2 production and plays an essential role in many current technologies such as the rapidly developing fuel cell technology, an efficient and clean alternative to fuel combustion for primary power generation [1]. Although platinum group metals (PGM) have been employed as the most effective and durable catalysts within most types of low temperature fuel cells [2–4], the high price and limited availability of platinum becomes one of the major barriers to commercialization of fuel cells. Research has also shown that supported gold catalysts are very active in the WGS reaction at low temperatures [5, 6], thus potential candidates for use in fuel processors. However, most of previous studies on gold-based catalysts used a mixture of carbon monoxide and inert gases as feed [7–11], and therefore are not applicable to the hydrogen-rich conditions prevailing in the fuel cell systems. In fact, the fast deactivation of gold catalysts under synthetic and real reformate tests has been reported. The studies by Kim and Thompson showed that despite the high initial activity, Au/CeO2 catalysts lost activity by more than 50% during the first 12 h in a simulated reformate mixture (10% CO, 22% H2O, 6% CO2, 43% H2 and 19% N2) [12]. The deactivation maybe caused by the presence of large amount of H2 [13]. Therefore, the development of gold catalysts which are able to maintain high activity and stability under *To whom correspondence s