Surface properties and catalytic behavior of Ru supported on composite La(2)O(3)-SiO(2) oxides

Binary La(2)O(3)-SiO(2) supports were employed to obtain active, stable Ru catalysts with high dispersions for the dry reforming of methane. Supports with 15, 27, 40 and 50 wt.% of La(2)O(3) were prepared by incipient wetness impregnation on SiO(2). The Ru loading was 0.6 wt.% for all catalysts. The solids were evaluated in a fixed-bed reactor under differential conditions. Previously, they were reduced at either 673 or 823 K. The most active catalyst was Ru/La(2)O(3)(50)-SiO(2). All the uncalcined formulations were stable after 100 h on stream. XRD, CO chemisorption, TPR, XPS, ISS and CO adsorption monitored by FTIR were employed to characterize the catalysts and the Ru species. XRD showed the presence of La(2)Si(2)O(7) with low crystallinity in all the supports. By means of XPS and ISS, the formation of a surface La(2)Si(2)O(7) phase was suggested for samples containing La(2)O(3) up to 40 wt.%. Higher contents could lead to surface La(2)O(3) particle growth. The TOF(CH(4)) values showed a minimum for the Ru/La(2)O(3)(40)-SiO(2) solid in agreement with a lower metal-support interaction. The Ru/La(2)O(3)(50)-SiO(2) catalyst exhibited the highest TOF(CH(4)) for both reduction treatments. The differences in thermal stability of the CO adsorbed species on Ru supported on silica or on binary La(2)O(3)-SiO(2) supports sustain that the presence of lanthanum influences the metal-support interaction and metal dispersion.