Magnesia ceria

Similar results were obtained with other supports such as silica, alumina, magnesia ceria. It was also verified that the direct exchange between the gas phase and the support could not occur at a significant rate on most oxide supports. TPIE were carried out on the bare supports and... 

Catalysts. - Group VIII metals, conventional base metal catalysts (Ni, Co, and Fe) as well as noble metal catalysts (Pt, Ru, Rh, Pd) are active for the SR reaction. These are usually dispersed on various oxide supports. y-Alumina is widely used but a-alumina, magnesium aluminate, calcium aluminate, ceria, magnesia, pervoskites, and zirconia are also used as support materials. The following sections discuss the base metal and noble metal catalysts in detail, focusing on liquid hydrocarbon SR for fuel cell applications. 

The method works well with supports having an PZC greater than five, such as magnesia, titania (usually Degussa P25, 70% anatase and 30% rutile), alumina, zirconia and ceria,10,37,65 but it is not suitable for silica (PZC 2), silica-alumina (PZC 1), tungsta (PZC l),10 or for supports such as activated carbon68 (see Section 4.5.4). For zeolites, surprisingly, it does seem to work (see Section 4.5.1). 

In addition to titania, alumina and ceria supports (Table 4.4), the DPU method has been applied to other supports. Gold particles supported on ferric oxide were quite small (3-7 nm) after thermal treatment is static air at 623 K.80 Another study reported the use of the DPU method to deposit gold onto other supports (MgO, CaO, SrC>2 and BaO).81 After calcination at 673 K, gold particles of moderate size were obtained on magnesia (8 nm) and on calcia (6nm). In all cases, all the gold in solution was deposited on the support. 

From the suggestions found in the literature as summarised in Section 6.3.3, one might conclude that with ceramic oxides, including titania and zirconia, the dominant active species is Au°, either alone or with some cationic species. With ferric oxide, it may be Au° associated with Au111, with magnesia, it may be Au° associated with Au1, and with ceria, it is not clear which combination of the three species is active. 

Precipitation-deposition can be used to produce catalysts with a variety of supports, not only those that are formed from coprecipitated precursors. It has been employed to prepare nickel deposited on silica, alumina, magnesia, titania, thoria, ceria, zinc oxide and chromium oxide.36 It has also been used to make supported precious metal catalysts. For example, palladium hydroxide was precipitated onto carbon by the addition of lithium hydroxide to a suspension of... 

New generations of catalysts still at the R D stage combine reducible supports such as (doped) ceria and magnesia supporting noble and non-noble metals [5-19]. 

Regarding ceramic-containment materials," sihca, SiO, and alumina, Al O, are strongly attacked and hence readily dissolve in liquid lithium. By contrast, alkaline-earth oxides such as beryllia (BeO), magnesia (MgO), and calcia (CaO) and rare-earth oxides such as ceria (CeOJ, yttria (YfiJ, chromite spinel (FeCr OJ, and yttrium aluminum garnet (Y AljOj ) seem to be noncorroded below 500 C, while aluminum, titanium, and zirconium nitrides or... 

Aluminum silicate, zirconium silicate, alumina, zirconia, ceria, magnesia, tin oxide, silicon carbide, boron carbide, tungsten carbide Hard coatings, abrasives, polishing media... 

Similar results were reported by Frusteri et of. for their nickel/magnesia and nickel/ceria catalysts [198]. At a reaction temperature of 650 °C, coke formation was significant under conditions of steam reforming. In the nickel/magnesia catalyst, which contained 15wt.% nickel, less than O.lwt.% carbon was formed within a 20-h test duration when operated under autothermal conditions. Consequently, no deactivation of the catalyst was observed. However, the 0/C ratio that was required to achieve this stable performance was rather high at 1.2, and the S/C ratio of 4.2 was also very high. Besides methane, small amounts of acetaldehyde were formed as a by-product. 

Higher in activity, but also more costly, are catalysts that contain precious metals such as rhodium, ruthenium, platinum, palladium and rhenium or mixtures thereof [107], while alumina or magnesia [214] and rare earth oxides such as ceria and zirconia or mixtures thereof serve as the carrier material. Rare earth metals have an oxygen storage capability, they interact with the precious metal and generate active sites for hydrocarbon activation [164]. 

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