Catalyst ruthenium/titania

Krishna and Bell used tracers to define the role of intermediates in the FTS over a ruthenium-titania catalyst. A conversion was established using a CO/H2/He feed and then at 20 minutes the feed was switched to one that contained 250 ppm or 1.2 percent C2H4/ CO/H2/He feed at 30 minutes the feed was switched again to CO/H2/He. The data in Figure 40 show the transient response of the fraction of each product that is C-labeled, Fj,(t), when the feed is switched from one containing to one containing... 

F-T Catalysts The patent literature is replete with recipes for the production of F-T catalysts, with most formulations being based on iron, cobalt, or ruthenium, typically with the addition of some pro-moter(s). Nickel is sometimes listed as a F-T catalyst, but nickel has too much hydrogenation activity and produces mainly methane. In practice, because of the cost of ruthenium, commercial plants use either cobalt-based or iron-based catalysts. Cobalt is usually deposited on a refractory oxide support, such as alumina, silica, titania, or zirconia. Iron is typically not supported and may be prepared by precipitation. 

The fonn of the titania is also an important issue. We have found that the rutile form is the preferred component for use in the aqueous processing environment. The anatase form is readily converted to the rutile in tlK aqueous environment over a period of hours to days depending on the operating temperature. As a result, ruthenium catalysts formulated on anatase support lose activity over time, while those formulated on rutile maintain tlieir activity at operating conditions. 

The deposition of platinum, rhodium and ruthenium acetylacetonates on titania takes place by reaction with the surface hydroxy groups to give a supported complex. Thermal decomposition of these supported complexes in vacuum gave highly dispersed titania supported metal catalysts having metal particles about 2 nm in diameter. ... 

This new single-step synthesis unites the simplicity of preparation and lower production costs, with the outstanding properties of the final catalysts. By the single-step procedure proposed here, deposition of dispersed nanoparticles of noble metals on ceramic supports with customised textural properties and shape was achieved. Noble metals including platinum, palladium, rhodium, ruthenium, iridium, etc. and metal oxides including copper, iron, nickel, chromimn, cerium oxides, etc on sepiolite or its mixtures with alumina, titania, zirconia or other refractory oxides have been also studied. 

A possible mechanism for the hydrogenation of carboxyl bond over titania supported ruthenium catalyst with the involvement of Metal Support Interaction (MSI) is seen in Scheme 6. The reaction proceeds via the formation of alkoxide surface intermediates. 

When titania is used as a support for cobalt iron or ruthenium, veiy active catalysts are prepared, indicating the importance of certain oxide-metal interfaces as active sites for CO hydrogenation. 

Preferential oxidation catalysts usually consist of precious metals such as platinum, ruthenium, palladium, rhodium, gold and alloys of platinum with tin, ruthenium [164] or rhodium. Typical carrier materials are alumina and zeolites [164], such as zeolite A, mordenite and zeolite X. Other possible carriers are cobalt oxide, ceria, tin oxide, zirconia, titania and iron oxide [214]. A high precious metal loading usually improves catalyst performance [164]. 

Takenaka ct al. studied the activity of various catalysts for carbon monoxide methanation in the absence of carbon dioxide [342]. From the different active species on a silica carrier, 5 wt.% ruthenium, 10wt% nickel and 10 wt.% cobalt were significantly more active than iron, palladium or platinum, each prepared with an active species content of 10 wt.%. Then Takenaka tested nickel, ruthenium and cobalt catalysts on different carrier materials, namely, alumina, silica, titania and zirconia. The formulations most active were nickel/zirconia and mthenium/ titania catalysts. The best performing catalyst was the 5 wt.% mthenium/titania, which converted the carbon monoxide apart from less than 20 ppm from a feed mixture containing 60 vol.% hydrogen, 15 vol.% carbon dioxide, 0.9 vol.% steam, 0.5 vol.% carbon monoxide, with a balance of helium at 220 °C. The space velocity was rather high at 300 L (hgcat) -... 

Rosa et al. [251] set up a complete 5-kW diesel fuel processor based on autothermal reforming and catalytic carbon monoxide clean-up, which was dedicated to a low temperature PEM fuel cell. The breadboard system was composed of the autothermal reformer operated between 800 and 850 °C with a ruthenium/perovskite catalyst (see Section 4.2.8), a single water-gas shift reactor containing platinum/titania/ceria catalyst operated between 270 and 300 °C (see Section 4.5.1), and a preferential oxidation reactor containing platinum/alumina catalyst operated between 165 and 180 °C. Figure 9.54 shows the gas composition and reactor temperatures achieved. The hydrogen content of the reformate was in the range from 40 to 44 vol.% on a dry basis. The carbon monoxide content of the reformate was 7.4 vol.% and could be reduced to values of between 0.3 and 1 vol.% after the water-gas shift reactor and to below 100 ppm after the preferential oxidation reactor. 

Arena (J9) devised more active and more hydrothermally stable mixed titania supports for Ru hydrogenation of glucose at 120 °C. Elliot has recently developed an even longer activity Ru/Ti02 (rutile) catalyst (20). Operation at lower temperature (100 °C) and with pH neutral conditions (for glucose) obviously helps to extend catalyst life compared to the conditions required for the raw biomass reactions herein. However, the rutile-supported ruthenium might be less prone to absorption and is scheduled for IDAHH tests. 

TI Fischer-Tropsch hydrocarbon synthesis - using, as catalyst, cobalt or ruthenium on titania with addn of water to feed to increase conversion and liq hydrocarbon yield... 

Ceria, titania, and zirconia supported ruthenium and eopper catalysts were tested in the production of n-butanal by n-butanol oxidation. These eatalysts were characterized by means of X-ray diffraction (XRD), N2 adsorption-desorption isotherms, temperature-programmed reduction (TPR), and X-ray photoelectron spectroscopy (XPS) techniques. The activity tests were performed in a fixed bed reaetor at 0.1 MPa and 623 K and pure mixture of reactants, air and n-butanol, in stequiometric proportion was introduced to the reactor. The rathenium catalysts showed a higher activity and stability than the copper catalysts, nevertheless the copper system showed a higher selectivity toward butyraldehyde production by n-butanol oxidation. 

EXAFS is a technique which has come into its own within the last five years [32-34] and has provided conclusive evidence which can be interpreted in terms of retention of the clustered state in active ruthenium catalysts derived from Ru3(CO)j 2 H4Ru4(C0)i2 active osmium catalysts derived from Os3(CO)32> H40s4(C0)] 2> 055(00) 3, supported on silica, alumina, and titania in our joint work with Hull University (Fig. 2) [35]. A particular advantage of EXAFS is that it is a technique which, in prospect, can be used iji situ to study working catalysts. 

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