Efforts have been aimed at utilizing the water–gas shift
reaction (WGSR) (CO+H2 O= CO2+H2) (ΔH0
298K = −41,2 kJ/mol)
for primary CO cleanup and additional hydrogen generation of
hydrocarbon reformate gas, followed by a preferential
oxidation step to reduce the CO level to about 10 ppm to feed a PEM fuel cell. For the LTWGS, Au, Cu, Pt and Rh were
deposited on CeO2 by means of two different deposition methods, that is incipient wetness impregnation (IWI) and combustion synthesis (CS), and the active element load was 2%.
According to the experimental results, the best catalyst
powder for the LTWGS was 2% Pt−CeO2, which gives a CO residual concentration of 1.3% at 325°C, though the conversion temperature was rather high (T suggested for LTWGS is 180−250°C).
A preliminary catalytic activity test on a microchannelled
reactor was also carried out. In order to determine the best
operating conditions, tests were carried out with the same gas feed composition and at different space velocities, varying from 0.8 Nl/min/g to 2.4 Nl/min/g. The conversion increased at lower space velocity, in particular the equilibrium curve was approximatively reached at 0.8 and 1.2 Nl/min/g, and the residual CO concentrations were respectively 1.2% and 1.3%.
For HTWGS, the catalyst 2% Pt−CeO2 (IWI) was tested in powder.