Alumina monoliths

Lead aerosol in the air is poisonous to breathe, especially for young children. Many people called for the abolition of lead in gasoline. In the 1970s, the photochemical smog in California was attributed to unburned hydrocarbons and carbon monoxide from automobile tailpipes, and the best solution was the catalytic converter which works with finely divided platinum particles deposited on alumina monoliths. When leaded gasoline is used, these platinum atoms would be quickly covered by a barrage of lead aerosols. This finally led to the abolishment of TEL as a gasoline additive. 

Similar results were achieved over a Rh/alumina monolith catalyst " using catalytic POX for the reforming of a simulated JP-8 military feed containing 500 ppm of sulfur (as benzothiophene or dibenzothiophene). Stable performance for over 500 h with complete conversion of the hydrocarbons to syngas at 1,050°C, 0.5 s contact time, and LHSV of about 0.5 h was reported. At this high temperature, carbon formation was not reported and the sulfur exited as hydrogen sulfide. 

Recently, the use of Rh supported on washcoated alumina monoliths has attracted interest for ATR of higher hydrocarbons.Reyes et al carried out ATR of n-C6 in monolithic catalysts containing Rh as an active component. A maximum H2 yield of 170% was obtained from the reforming of n-C6 at an O/C ratio of 1, a S/C of 1, preheat temperature of 700°C, and GHSV of 68,000 h Brandmair et al. also carried out ATR of n-C6 over Rh supported on ceramic monoliths at similar conditions, and reported that the Rh catalyst provided better performance over time. 

More recent studies of gas-phase imaging with more direct relevance to chemical processing and reaction engineering have involved the examination of thermally polarized gas (and liquid) flow in monolithic catalysts. Koptyug et al. (2000a) have obtained quantitative, spatially resolved velocity maps for the flow of thermally polarized acetylene, propane, butane and water flowing through the channels of alumina monoliths with an in-plane spatial resolution of 400 pm. The monoliths had a channel cross-section of 4.0 mm2 and a wall channel... 

The CVD method requires a high surface area support because the carbon that is formed usually does not show any porosity itself. In earlier CVD work, so-called carbon-covered-alumina monoliths were made by subjecting the alumina monolith to a flow of a hydrocarbon gas (e.g., cyclohexene) at high temperature (873-973 K) (56,87). 

The discrepancy between the lEP of alumina monoliths (pH 5) and that of alumina powders (pH 9) has divided the scientific community into two groups. One group considers the low lEP of monoliths to be a well-established experimental... 

Figure 2. Conversions and selectivities to CO and H2 over Pt (right) and Rh (left) on a-alumina monolith catalysts at atmospheric pressure at catalyst contact times of -1 millisecond.

A. S. Quiney, G. German , Y. Schuurman, Optimization of a water-gas diift reactor over a Pt/ ceria/alumina monolith, J. Power Sources 160 (2006) 1163-1169. 

Recently, the hydrogenation a mixture of toluene, styrene and 1-octene, representing a model feed for hydrotreating in the refining industry, was performed in monolith reactors [37]. One is a y-alumina monolith of diameter 1 cm and 15 or 30 cm long and the other is a more conventional cordierite monolith with a wall-coated layer of y-alumina. In both monoliths, the channels size is 1-2 mm and the catalyst is based on Ni. Substantial alkene conversions of more than 50% were observed in the small-channel reactors, which was attributed to the intensified mass-transfer rate generally measured in monolith reactors [16]. 

Tokudome Y, Nakanishi K, Hanada T (2009) Effect of La addition on thermal microstructural evolution of macroporous alumina monolith prepared from ionic precursors. J Ceramic Soc Japan 117 351-355. 

Gawel et al. present a scheme for sol-gel alumina monolith preparation starting with aluminiun alkoxides, aluminum salts, or aliuninum oxide hydroxide [8]. In the case of aliuninimi salts, they hydrolyze and condensate it into aliuninimi oxide hydroxide gels imder basic conditions [44,45]. However, since aqueous aluminum salt solutions are acidic, this requires a gradual process of increasing pH. 

The blast furnace stove, which heats the air that will be blown into the furnace from the tuyeres and burns the coke, is insulated with an acid-resistant gurmed material. The stack section is also lined with a gunned castable. A high-alumina monolithic refractory is used around the spout of the torpedo ladle. Torpedo ladles are used for transferring molten iron from the iron-making section of the plant to the steel section. Often when shortterm repairs are done to this item, monolithic refractories are used. 

Refractories in applications such as petroleum refineries are used primarily with insulating and abrasion-resistant properties in mind. Sections such as cyclone walls and reactors are lined with dense high-alumina castables. Various areas of chemical plants, such as reactors and high-pressure vessels, are commonly lined with high-grade alumina monolithics. 

Annaland TV, Kuipers JAM, van Swaaij WPM A kinetic rate expression for the time-dependent coke formation rate during propane dehydrogenation over a platinum alumina monolithic catalyst, Catal Today 66(2—4) 427—436, 2001. 

Zn-Al hydrotalcite-like film has been directly grown on the surface of porous anodic alumina monoliths. The highly porous structure of the AI2O3-AI monolith provided multiple chaimels for supplying Al species and promoted a chemical anchoring of the coating. The CuO was successfully impregnated on the hydrotaldte surface. In this way, active catalytic structures have been prepared and tested in total oxidation of ethanol and ethyl acetate. 

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