(487x) Preferential Oxidation of CO in Hydrogen-Rich Gas through An Au/NaY Zeolite Membrane for Fuel Cell Application

The proton exchange membrane fuel cell (PEMFC)has attracted much interest due to its low operation temperature, fast cold start and high efficiency. However, the Pt anodes of PEMFC are easily poisoned by CO in hydrogen fuel even with a very low concentration. It is critical to eliminate residual CO from the H2-rich gas stream before fed in PEMFC. Preferential oxidation of CO (PROX) is considered as the simplest and cost effective method for removing trace amounts of CO from H2. Recently, nanosized gold catalysts have been reported to have high catalytic activity in PROX at low temperature. Micro or Meso porous materials were generally used as hosts for supporting the nano particles. However, diffusion resistance from the porous channels and CO2 adsorption in the pores at low operation temperature could have important effects on the catalytic performance of gold catalysts. In this paper, we prepared a novel Au/NaY catalytic membrane for PROX to reduce the diffusion resistance and CO2 adsorption. Characterizations were focused on the microstructure and catalytic performance of Au/NaY zeolite membranes (designated (Au/NaY)m) and Au/NaY particles (designated (Au/NaY)p) as well.

Defect-free, pure NaY-type zeolite membranes were synthesized on disc-shaped porous a-Al2O3 substrates by a secondary growth method according to our previous report. The membranes have a thickness of ~15µm. Separation test of CO2/N2 mixture showed the membranes a high CO2 selectivity at low temperature. Au/NaY zeolite membranes were prepared by an ion-exchange method using chloroauric acid as a precursor. XRD analysis revealed the structure of the NaY zeolite did not change after ion exchange process. HRTEM results show the nano-sized gold is mostly in the range of 1~5nm. Preliminary PROX experiment showed that the catalytic membrane exhibited an excellent catalytic performance, which can reduce CO concentration in H2 stream from 2% to 0.7% at 373K by one stage treatment of the feed containing 1% CO, 1 % O2, 49% H2 and He in balance. The catalytic membrane shows a promising application in CO removal from hydrogen fuel. The effects of operation temperature, space velocity and feed pressure are being investigated and the structure of Au/NaY catalytic membrane is under optimization currently.