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

Abstract

The dry reforming of methane as a source of H 2 was performed using a well-known catalyst, Rh/La 2O 3, together with a novel one, Rh/La 2O 3-SiO 2, in a hydrogen-permeable membrane reactor. The catalysts were characterized by XRD, TPR, FTIR, 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/La 2O 3 catalysts. The La 2O 3-SiO 2 solids are also stable even though a weaker rhodium–lanthanum interaction (TPR) can be observed. The incorporation of the promoter (La 2O 3) 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%)/La 2O 3 (27%)-SiO 2 catalyst proved to be the best formulation. Operating the membrane reactor at 823 K, both methane and CO 2 conversions were 40% higher than the equilibrium values, producing 0.5 mol H 2/mol CH 4. This catalyst, tested at W/ F three times lower than Rh (0.6%)/La 2O 3, 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%)/La 2O 3 (27%)-SiO 2 is related to the high dispersion.