A stable, novel catalyst improves hydrogen production in a membrane reactor

The dry reforming of methane as a source of H-2 was performed using a well-known catalyst, Rh/La2O3, together with a novel one, Rh/La2O3-SiO2, in a hydrogen-permeable membrane reactor. The catalysts were characterized by XRD, TPR, IFTIR, H-2 and CO chemisorption. In all lanthanum-based catalysts, the activity remained constant after 100 h on stream at 823 K. The basis of their high stability could be traced back to the strong metal-support interaction (TPR) in Rh/La2O3 catalysts. The La2O3-SiO2 solids are also stable even though a weaker rhodium-lanthanum interaction (TPR) can be observed. The incorporation of the promoter (La2O3) to the silica support induces a parallel increase in the metal dispersion (CO adsorption). The effect of the operation variables upon the performance of the membrane reactor was also studied. The novel Rh (0.6%)/La2O3 (27%)-SiO2 catalyst proved to be the best formulation. Operating the membrane reactor at 823 K, both methane and CO2 conversions were 40% higher than the equilibrium values, producing 0.5 mol H-2/mol CH4. This catalyst, tested at W/F three times lower than Rh (0.6%)/La2O3, showed a similar performance. Both the increase of the sweep gas flow rate and the decrease of the permeation area significantly affected methane conversion and H-2 production. The presence of tiny amounts of graphite only detectable through LRS did not endanger membrane stability. The better performance of Rh (0.6%)/La2O3 (27%)-SiO2 is related to the high dispersion. (c) 2005 Elsevier B.V. All rights reserved.