In this work, 3% Ru-Al2O3 and 2% Rh-CeO2 catalysts were synthesized and tested for CH4-CO2 reforming activity using either CO2-rich or CO2-lean model biogas feed. Low carbon deposition was observed on both catalysts, which negligibly influenced catalytic activity. Catalyst deactivation during temperature programmed reaction was observed only with Ru-Al2O3, which was caused by metallic cluster sintering. Both catalysts exhibited good stability during the 70 h exposure to undiluted equimolar CH4/CO2 gas stream at 750 °C. By varying residence time in the reactor during CH4-CO2 reforming, very similar quantities of H2 were consumed for water formation. Reverse water-gas shift (RWGS) reaction occurred to a very similar extent either with low or high WHSV values over both catalysts, revealing that product gas mixture contained near RWGS equilibrium composition, confirming the dominance of WGS reaction and showing that shortening the contact time would actually decrease the H2/CO ratio in the syngas produced by CH4-CO2 reforming, as long as RWGS is quasi equilibrated. H2/CO molar ratio in the produced syngas can be increased either by operating at higher temperatures, or by using a feed stream with CH4/CO2 ratio well above 1.
COBISS.SI-ID: 4844826
The present paper deals with the study concerning the CO removal from reforming H2-rich gas stream through WGS reaction over Rh-based catalysts supported on CeO2 carriers. CeO2 was prepared by two different methods: solution combustion synthesis (SCS) and hard template (HT); incipient wetness impregnation method was used to deposit the active metal on the carriers. The screening at powder level in a fixed bed micro-reactor highlighted that feeding 5% CO and 20% H2O (N2 balance) with the HT-prepared catalyst, CO conversion started at slightly lower temperature, but CH4 outlet concentrations were higher than those of the SCS-prepared one. With a simulated reformate mixture (5% CO + 20% H2O + 11% CO2 + 40% H2, N2 balance), the equilibrium WGS curve was exceeded for both catalysts (for the HT-preparedcatalyst, CO conversion started at lower temperature and reached 100%), due to the parasite methanation reactions of both CO and CO2, favoured by the presence of a large hydrogen concentration in the reactor. A very high CH4 outlet concentration (max 18.6%) was measured for the HT-prepared catalyst. Then, tests at different weight space velocities WSV were carried out: with the SCS-prepared catalyst the best performance was obtained by lowering WSV.
COBISS.SI-ID: 4800538
The contribution of co-author (Dr. Stanko Hočevar) from the Laboratory of Catalysis and Chemical Reaction Engineering at the National Institute of Chemistry in this paper is double: as an expert he has contributed to the concept of R&D in the field of hydrogen technologies of interest for MoD and, on the other side, as one of the partners in the R&D project he contributed to the concept of microreactor fuel processor system built in LTCC technology, to the development of catalysts precursor syntheses and to the development of methods for catalysts deposition and activation in the closed microchannel structure made of LTCC. He also performed part of the measurements of methanol steam reforming in microreactor system embeded in experimental laboratory test station built in the Laboratory of Catalysis and Chemical Reaction Engineering at the National Institute of Chemistry. The oucome of this research is the first ceramic microreactor fuel processor for hydrogen production in Slovenia.
COBISS.SI-ID: 25415207