Experimental and numerical investigation of supported rhodium catalysts for partial oxidation of methane in exhaust gas diluted reaction mixtures
2007 (English)In: Chemical Engineering Science, ISSN 0009-2509, E-ISSN 1873-4405, Vol. 62, no 15, 3991-4011 p.Article in journal (Refereed) Published
The partial oxidation of methane/oxygen mixtures with large exhaust gas dilution (46.3 vol% H2O and 23.1 vol% CO2) has been investigated experimentally and numerically over Rh/CeO2-ZrO2, Rh/ZrO2 and Rh/alpha-Al2O3 catalysts. Experiments were carried out in a short-contact-time (similar to 8 ms) reactor at 5 bar and included exhaust gas analysis, temperature measurements along the reactor, and catalyst characterization. Additional experiments were performed in an optically accessible channel-flow reactor and involved in situ Raman measurements of major gas-phase species concentrations over the catalyst boundary layer and laser-induced fluorescence (LIF) of formaldehyde. A full elliptic two-dimensional numerical code that included elementary hetero-/homogeneous chemical reaction schemes and relevant heat transfer mechanisms in the solid was used in the simulations. The employed heterogeneous reaction mechanism, including only active Rh sites, reproduced the experiments with good accuracy. The ratio of active to geometrical surface area, deduced from hydrogen chemisorption measurements, was the single model parameter needed to account for the effect of different supports. This indicated that water activation occurring on support sites, resulting in inverse OH spillover from the support to the noble metal sites, could be neglected under the present conditions with high water dilution. An evident relationship between noble metal dispersion and catalytic behavior, in terms of methane conversion and synthesis gas yields, could be established. Both measurements and predictions indicated that an increasing Rh dispersion (in the order Rh/alpha-Al2O3, Rh/ZrO2, and Rh/CeO2-ZrO2) resulted in higher methane conversions, lower surface temperatures, and higher synthesis gas yields.
Place, publisher, year, edition, pages
2007. Vol. 62, no 15, 3991-4011 p.
partial oxidation of methane on rhodium, in situ Raman and LIF, catalyst support, catalyst selectivity, simulation, reaction engineering
IdentifiersURN: urn:nbn:se:kth:diva-6642DOI: 10.1016/j.ces.2007.04.041ISI: 000248779100012ScopusID: 2-s2.0-34347347126OAI: oai:DiVA.org:kth-6642DiVA: diva2:11406
QC 201101252006-12-152006-12-152011-01-25Bibliographically approved