Aluminum-chromium oxides

Aluminum chromium oxide catalyst Cr203,Af203... 

C and 19,600 kPa (2800 psi). The catalyst is a complex aluminum—ca dmium —chromium oxide that has high activity and exceptionally long life. The process is claimed to give a conversion of ester to alcohol of about 99% retaining essentially all of the original double bonds. 

There is also a two-step process of chromizing foUowed by aluminizing. Above 900°C the chromizing begins to rediffuse and the protective oxide changes to Al O from Cr202. Aluminum oxide is less volatile than chromium oxide and better for high temperature oxidation resistance above 1000°C. 

Chromium Oxide-Based Catalysts. Chromium oxide-based catalysts were originally developed by Phillips Petroleum Company for the manufacture of HDPE resins subsequendy, they have been modified for ethylene—a-olefin copolymerisation reactions (10). These catalysts use a mixed sihca—titania support containing from 2 to 20 wt % of Ti. After the deposition of chromium species onto the support, the catalyst is first oxidised by an oxygen—air mixture and then reduced at increased temperatures with carbon monoxide. The catalyst systems used for ethylene copolymerisation consist of sohd catalysts and co-catalysts, ie, triaLkylboron or trialkyl aluminum compounds. Ethylene—a-olefin copolymers produced with these catalysts have very broad molecular weight distributions, characterised by M.Jin the 12—35 and MER in the 80—200 range. 

Dehydrogenation of /i-Butane. Dehydrogenation of / -butane [106-97-8] via the Houdry process is carried out under partial vacuum, 35—75 kPa (5—11 psi), at about 535—650°C with a fixed-bed catalyst. The catalyst consists of aluminum oxide and chromium oxide as the principal components. The reaction is endothermic and the cycle life of the catalyst is about 10 minutes because of coke buildup. Several parallel reactors are needed in the plant to allow for continuous operation with catalyst regeneration. Thermodynamics limits the conversion to about 30—40% and the ultimate yield is 60—65 wt % (233). 

Chromium oxide is mixed with aluminum powder, placed in a refractory-lined vessel, and ignited with barium peroxide and magnesium powder. The reaction is exothermic and self-sustaining. Chromium metal of 97—99% purity is obtained, the chief impurities being aluminum, iron, and silicon (Table 4). Commercial chromium metal may also be produced from the oxide by reduction with silicon in an electric-arc furnace. 

The product is similar to that obtained by the aliiminothermic process however, the aluminum content is lower and silicon may mn as high as 0.8%. Chromium oxide may also be reduced with carbon at low pressure. 

Alloys./ A substantial amount of chromic oxide is used in the manufacture of chromium metal and aluminum—chromium master alloys. 

Chrornium—cobalt—alurninum oxide [68187-11-1]—Cl Pigment Blue 36, Cl No. 77343. A blue—green pigment obtained by calcining a mixture of chromium oxide, cobalt carbonate, and aluminum oxide. It may contain small amounts (<1% each) of oxides of barium, boron, siUcon, and nickel. 

A wide variety of greens ranging from blue to yellow in shade ate based on cobalt in combination with chromium, aluminum, titanium, nickel, magnesium, antimony, or zinc. These are brighter than the chromium oxides. 

With Acyl Halides, Hydrogen Halides, and Metallic Halides. Ethylene oxide reacts with acetyl chloride at slightly elevated temperatures in the presence of hydrogen chloride to give the acetate of ethylene chlorohydrin (70). Hydrogen haUdes react to form the corresponding halohydrins (71). Aqueous solutions of ethylene oxide and a metallic haUde can result in the precipitation of the metal hydroxide (72,73). The haUdes of aluminum, chromium, iron, thorium, and zinc in dilute solution react with ethylene oxide to form sols or gels of the metal oxide hydrates and ethylene halohydrin (74). 

Chromium Oxide is present in just about every maintenance shop in the world. We call it the GRINDING WHEEL The abrasive material in your electric grinding wheel Is Chromium Oxide. Cheap wheels may tend to use aluminum oxide. 

Titanium, vanadium or chromium oxides activated with chlorine-free organo-aluminum compounds, triethyl- or triisobutyl aluminum, have also been used as catalysts [285],... 

Aluminum oxide, which has the mineral name corundum, is a solid that has several important uses. Because it will withstand very high temperatures, it is a refractory material, and because of its hardness it is commonly used in abrasives. Corundum often contains traces of other metals that impart a color to the crystals, making them valuable as gemstones. For example, ruby contains a small amount of chromium oxide, which causes the crystal to have a red color. By adding a small amount of a suitable metal oxide, it is possible to produce gemstones having a range of colors. 

Hitachi Cable Ltd. (35) has claimed that dehydrogenation catalysts, exemplified by chromium oxide—zinc oxide, iron oxide, zinc oxide, and aluminum oxide—manganese oxide inhibit drip and reduce flammability of a polyolefin mainly flame retarded with ATH or magnesium hydroxide. Proprietary grades of ATH and Mg(OH)2 are on the market which contain small amounts of other metal oxides to increase char, possibly by this mechanism. 

Many barium aluminosilicate-based compositions will eventually react with the chromium oxide or aluminum oxide scales on the metal interconnect or metal edge rails to form barium chromate or a celsian phase at the interface [6], This can cause a mechanical weakness that is easily delaminated. Also, compositions that contain boron can react over time with water (steam) to produce B2(OH)2 or B(OH)3 gas. This can decompose the glass and greatly limit the lifetime of the seal. Thus many of the new investigations have emphasized low or no boron glass compositions. 

However, in many cases, the oxide layer adheres, or sticks firmly, to the metal surface. This layer protects the metal from further corrosion. For example, aluminum, chromium, and magnesium are readily oxidized in air to form their oxides, AI2O3, Cr203, and MgO. Unless the oxide layer is broken by a cut or a scratch, the layer prevents further corrosion. In contrast, rust easily flakes off from the surface of an iron object and provides little protection against further corrosion. 

In only rare cases does one find minerals or metals in pure form (such as gold). The earth s surface consists of a variety of minerals (major components iron, silica oxides, calcium, magnesium, aluminum, chromium, cobalt, and titanium). 

The Econ-Abator system is a fluidized-bed catalytic oxidation system. Catalytic fluidized beds allow for destruction of volatile organic compounds (VOCs) at lower temperatures than conventional oxidation systems (typically 500 to 750°F). The technology uses a proprietary catalyst consisting of an aluminum oxide sphere impregnated with chromium oxide. 

Reforming Both thermal and catalytic processes are utilized to convert naphtha fractions into high-octane aromatic compounds. Thermal reforming is utilized to convert heavy naphthas into gasoline-quality aromatics. Catalytic reforming is utilized to convert straight-run naphtha fractions into aromatics. Catalysts utilized include oxides of aluminum, chromium, cobalt, and molybdenum as well as platinum-based catalysts. 

Fig. 1.1.8 Scanning electron micrographs (SEM) of (A) aluminum (hydrous) oxide particles. obtained by aging at 100°C for 72 h a solution containing I X 10-3 mol dm-3 A1(CI04)3 and 1 X 10-3 mol dm-3 AINHjfSO.,. (B) TEM of chromium (hydrous) oxide particles, obtained by aging at 75 C for 24 h a 4.0 X 10-4 mol dm-3 solution of CrK(S04)2.

The pigment properties of chromium oxides can be modified by precipitation of hydroxides (e.g., of titanium or aluminum), and subsequent calcining. This treatment changes the color to yellow-green, and decreases the flocculation tendency [3.54], Aftertreatment with organic compounds (e.g., alkoxylated alkylsulfon-amides) is also used [3.55]. 

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