Production of ultrapure hydrogen in a Pd-Ag membrane reactor using Ru/ La2O3 catalysts

B.FAROLDI, C. CARRARA, E.A. LOMBARDO, L.M. CORNAGLIA

APPLIED CATALYSIS A-GENERAL

ELSEVIER

Año: 2006

0926-860X

Ru catalysts supported on lanthanum oxide with  different loadings were prepared  by  wet impregnation.  These solids were characterized  by  Laser Raman spectroscopy,  XPS, XRD and TPR. The catalytic activity toward hydrogen production through the dry reforming of methane was determined  in a fixed-bed reactor and a membrane reactor. The reaction rate expressed per gram of Ru decreased when  the metal loading increased. In the Pd-Ag membrane reactor, when the sweep gas flow rate (SG)  increased, the conversions overcame the equilibrium values and the difference between CH4 and CO2  conversions  decreased.  Both Ru(0.6) and Ru(1.2) catalysts were able to restore the equilibrium  for the dry reforming reaction up to values of  SG=30 ml min-1; Ru(0.6) was the most effective catalyst.  By employing  a CO2/CH4 =1 and a  SG of  0.05 mmol s-1, both a high H2 permeation flux  of 5.68 10-7 mol s-1 m-2 and  a hydrogen recovery of  80%  were obtained. Both the TPR and the Raman spectroscopy  data indicated the presence of Ru(III) strongly interacting with La. Significantly, this observation was further confirmed by the appearance of  Ru(III) on the  surface.  When the Ru  content increased,  the  higher Ru 3d binding energy component  was proposed  as arising from Ru(IV). Concerning the Ru(1.2) solid, the presence of Ru(IV)  was detected by means of  TPR experiments, in agreement with  the  high  proportion  of Ru(IV) on the  surface.  Therefore, a  fraction of Ru  loading was  present in this solid as species  with  weaker metal-support interaction leading to the  slight deactivation of this catalyst in the membrane reactor.