Development of an active, selective and durable water-gas shift catalyst for use in membrane reactors

Abstract

Rh(0.6%)/La2O3 and Rh(0.6%)/La2O3(27 wt%)·SiO2 were assayed for the WGS reaction at 673 K and 1 atm. They were both more active than industrial Cr-Fe based catalysts. Rh(0.6%)/La2O3 was the most active but it progressively deactivated. To investigate its deactivation and the stability of the Rh(0.6%)/La2O3(27 wt%)·SiO2, the WGS reaction was carried out in a DRIFTS cell in operando mode. The deactivation of the former was due to the strong adsorption of intermediate oxygenates. Another disadvantage of the Rh formulations was their methanation activity. Therefore, a series of formulations containing 0.1 wt% through 1.2 wt% Pt supported on La2O3(27 wt%)·SiO2 were synthesized and catalytically evaluated in a fixed-bed reactor. The activity, methane formation and stability were carefully checked. The fresh and used catalysts were characterized through a battery of techniques including XRD, LRS and XPS. The Pt(0.1 wt%) formulation resulted the most active one per gram of platinum and negligible methanation occurred. It maintained the activity and selectivity after 155 h on stream. This catalyst was tested in a Pd-Ag membrane reactor to produce ultrapure H2 (<10 ppm of CO) that can be used to feed a low temperature PEM fuel cell. Comparing our results with those already published, it is concluded that our system is one of the best ones reported so far.