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

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

Natal, Brasil

Congreso; 8th Natural Gas Conversion Symposium; 2007

Catalytic dry reforming is the reaction of  carbon  dioxide  with  methane  to  produce syngas.  If the main goal is to  produce H2, this reaction  can be carried out  in two different ways: in a fixed-bed  reactor followed by the purification steps, or in a  membrane reactor combining the  reaction  and the purification in a single vessel. In the latter option, the system offers the possibility of overcoming the thermodynamic limitations of this endothermic reaction, allowing the attainment of higher methane conversions at  lower temperatures. Dense Pd/Ag membranes exhibit almost 100%  selectivity towards hydrogen, so that ultrapure hydrogen could be produced. Noble metals like   rhodium and ruthenium are more active than Ni for the methane reforming reactions.  Furthermore, when the appropriate supports are used these formulations are catalytically stable and do not produce a significant amount of carbonaceous residues. Ruthenium, which has applications in several hydrogen-producing reactions, has been selected as an active element due to its relative low price compared with Rh. In La-containing  Rh  catalysts,  a high  stability  has been   reported, attributed to   metal-support interaction. For Rh/La2O3  solids, this interaction  was  very strong. However, when a composite  La2O3- SiO2 material  was used as support, a weaker  interaction  was observed.  The purpose of this work is to develop low-loading Ru/La2O3 catalyts to be applied  in membrane reactors  for ultrapure hydrogen production. The  catalysts were prepared by the conventional wet impregnation of RuCl3.3H2O onto La2O3. The solids were characterized by Laser Raman spectroscopy, XPS, XRD and TPR. The catalytic activity toward hydrogen production was determined in both a fixed-bed reactor and a membrane reactor.