Partial oxidation of methane to syngas on Rh/Al2O3 and Rh/Ce-ZrO2 catalysts

Abstract

A oxidação parcial do metano sobre catalisadores de ródio suportados em g-Al 2 O 3 , CeO 2 , ZrO 2 e Ce-ZrO 2 foi investigada. Medidas de DRIFTS (espectroscopia no infravermelho com reflectância difusa) de CO adsorvido mostraram que houve a formação de diferentes espécies de ródio nos diferentes suportes, o que por sua vez influenciou na dispersão do metal. Os efeitos da dispersão metálica e da capacidade de armazenamento de oxigênio sobre a atividade dos catalisadores na oxidação parcial foram discutidos.The partial oxidation of methane with g-Al 2 O 3 -, CeO 2 -, ZrO 2 -and Ce-ZrO 2 -supported rhodium catalysts was investigated. DRIFTS (diffuse reflectance infrared spectroscopy) measurements of adsorbed CO showed the formation of different rhodium species on different supports, which influenced the dispersion of the metal. The effects of the metal dispersion, oxygen storage capacity on the activity of these catalysts for the partial oxidation of methane are discussed.Keywords: methane partial oxidation, methane, ceria-zirconia, rhodium, DRIFTS IntroductionThe catalytic partial oxidation of methane is an alternative to steam reforming, the industrial process for the production of synthesis gas from methane. Partial oxidation is a more energy efficient and less expensive process than steam reforming. The partial oxidation of methane (POM) is a mildly exothermic reaction, in which methane reacts with a limited amount of oxygen to produce hydrogen and carbon monoxide:The POM process is capable of producing syngas with a H 2 /CO ratio of approximately 2, which makes it a favorable method for methanol and hydrocarbon synthesis. 1,2 Noble metal catalysts (Ir, Ru, Rh, Pt, Pd) exhibit high activity, along with long-term stability, while minimizing the levels of coking, particularly when compared to the non-noble metals (such as Fe, Co, Ni). 1,2 The lack of a hydrogen infrastructure, as well as disadvantages in hydrogen storage, has stimulated the development of compact fuel processors, which are able to produce a rich hydrogen gas mixture from hydrocarbons. Several studies have reported that Rh catalysts are especially appropriate for use in compact fuel processors because of their high activity, selectivity for syngas and resistance to carbon deposition. 2 One of the main disadvantages of methane conversion is the deactivation due to coke formation. Thus, there is a great interest in designing catalysts that minimize the deleterious effect of coking. The presence of oxygen vacancies in supports that contain CeO 2 proved to be instrumental in keeping the metal particles free from coke deposition during the steam reforming, 3-5 partial oxidation, 6-9 CO 2 reforming and autothermal reforming of methane, 10-12 when using nickel or noble metals as catalysts. [13][14][15] Furthermore, ceria may also improve the catalytic performance by increasing the noble metal dispersion and stabilizing the support. Both the metal dispersion and support reducibility of Pt/CeO 2 and Pt/Ce x Zr 1-x O 2 were found to influence the catalytic ...

Continuous gas phase catalytic transformation of levulinic acid to γ‐valerolactone over supported Au catalysts

“…Oxygen chemisorption post‐TPR was negligible on Au/Al 2 O 3 and Pd/Al 2 O 3 (Table ), consistent with the non‐reducibility of Al 2 O 3 where temperatures ≥1373 K are required for oxide reduction . Greater uptake on Au/CeO 2 and Au/TiO 2 is consistent with vacancy formation during TPR of these reducible oxides.…”

Fe catalysts for methane decomposition to produce hydrogen and carbon nano materials

“…The better Fe dispersion thus explains the higher reduction temperature of impregnated samples, meanwhile the separation of overlapped Fe3O4→FeO→Fe 0 broad reduction peaks over fused samples into two peaks over impregnated samples. One additional peak belongs to CeO2-ZrO2 solid solution [54] is detected at c.a. 600°C for I-Fe20-CeO2/ZrO2.…”

Selective C−O Hydrogenolysis of Erythritol over Supported Rh‐ReOx Catalysts in the Aqueous Phase

“…The mass spectrum of the evolved gas was recordeda safunctiono f temperature. Theo nly signals observed were at m/z = 17 and 18, which correspond to the formation of water caused by the reduction.P reviously,t he temperature-programmed reduction (TPR) profiles of as eries of Rh catalysts supported on TiO 2 [34] and ZrO 2 [35] showedt hat ar eduction temperature lower than 180 8Cw as high enough to reduce all rhodium oxide to the metallics tate. The Rh-Re/TiO 2 and Rh-Re/ZrO 2 catalysts presented differentH 2 -TGAprofiles.…”