Catalytic partial oxidation of methane on platinum investigated by spatial reactor profiles, spatially resolved spectroscopy, and microkinetic modeling

Abstract

Spatially resolved profile measurements, Raman spectroscopy, electron microscopy, and microkinetic modeling have been used to study the catalytic partial oxidation of methane on Pt. The measured species profiles through Pt coated foam catalysts exhibit a two-zone structure: an abrupt change in reaction rates separates the fast exothermic oxidation chemistry at the entrance of the reactor from the slow endothermic reforming chemistry. Spatially resolved Raman spectroscopy and electron microscopy confirm that the position of the mechanistic change could be correlated with Pt transportation and formation of carbonaceous deposits blocking the majority of active Pt sites in the reforming zone. The species profiles were simulated using a pseudo-2D heterogeneous model, which includes heat and mass transport limitations, and two state-of-the-art chemical kinetic mechanisms. Although both mechanisms are in quantitative agreement with the oxygen profiles, the two mechanisms differ substantially in their predictions of the branching ratio between partial and complete oxidation, as well as surface site coverages. The experimentally observed change in reaction rates is attributed to carbon formation, which the mechanisms are unable to reproduce, since they do not include carbon–carbon coupling reactions

Methane Activation by Heterogeneous Catalysis

“…On Rh, model predictions are in excellent agreement with experimental data [38,41,44]. On Pt, agreement between elementary step models and experimental data is less good [45] [46]. From the catalyst perspective, temperature and coke resistant CPO catalysts are required.…”

Stable Rh particles in hydrotalcite-derived catalysts coated on FeCrAlloy foams by electrosynthesis

“…As materials for the support, honeycombs and open-cell foams made of ceramic (cordierite [12][13][14], ␣-Al 2 O 3 [3,15,16], SiC [17]) and metallic (Ni [18,19], FeCrAlloy [20][21][22][23]) materials are mainly employed.…”

Comment on “The Critical evaluation of in situ probe techniques for catalytic honeycomb monoliths” by Hettel et al.

“…These differences imply that, while there may be significant invasiveness of the probes under the conditions used by Hettel et al this is not necessarily the case for the experimental setup used by Sá et al [2] or any of the similar systems that use in-situ probes [3][4][5][6][7][8][9][10]. In fact, due 'falsification' or "falsified" was incorrectly used in reference to work using intra-catalyst probes, such as our work [2].…”