Alumina nature

A variety of material could be used as the basis for cracking catalyst, including synthetic silica-alumina, natural clay, or silica-magnesia. If these materials did not contain significant amounts of metals such as chromium or platinum that catalyzed the burning of carbon, the burning rate of the coke is independent of the base as shown in Fig. 7. 

Davydov, A. A., Kantcheva, M. and Chepotko, M. L. FTIR spectroscopic study on nickel(II)-exchanged sulfated alumina nature of the active sites in the catalytic oligomerization of ethene. Catal. Lett., 2002, 83, 97-108. 

Chupas et al. (2001) NMR Fluorination of alumina Nature of active phase, role of defects + + + Fluorocarbon dismutation... 

The dynamic desiccant capacity of the alumina in a TSA process depends on the type of alumina, nature and composition of the feed stream, regeneration temperature, etc. A typical water removal capacity for alumina is 5-15% by weight. The typical total cycle time for a TSA process is 2-8 hours. 

These include alumina, natural graphite, manganese, fluorspar, quartz crystal, strontium, thaUium, thorium, and yttrium. These come from places such as Canada, China, Mexico, Germany, and South Africa. 

De Mumbrum, L. E., and M. L. Jackson, 1956. Infrared absorption evidence on exchange reaction mechanism of copper and zinc with layer silicate clays and peats. Soil Sci. Soc. Am. Proc. 20 234. Diamond, S., 1964. Rapid reaction of lime with hydrous alumina. Nature 204 183. 

Many catalysts have been used but the standard catalysts are generally mixtures of silica and alumina or natural or synthetic aluminium silicate zeolites. 

Prepared by heating ammonium mucate, or from butyne-l,4-diol and ammonia in the presence of an alumina catalyst. The pyrrole molecule is aromatic in character. It is not basic and the imino-hydrogen atom can be replaced by potassium. Many pyrrole derivatives occur naturally, e.g. proline, indican, haem and chlorophyll. 

Many solids have foreign atoms or molecular groupings on their surfaces that are so tightly held that they do not really enter into adsorption-desorption equilibrium and so can be regarded as part of the surface structure. The partial surface oxidation of carbon blacks has been mentioned as having an important influence on their adsorptive behavior (Section X-3A) depending on conditions, the oxidized surface may be acidic or basic (see Ref. 61), and the surface pattern of the carbon rings may be affected [62]. As one other example, the chemical nature of the acidic sites of silica-alumina catalysts has been a subject of much discussion. The main question has been whether the sites represented Brpnsted (proton donor) or Lewis (electron-acceptor) acids. Hall... 

Aluminium oxide occurs naturally as emery (an impure form) and as corundum. Corundum is a crystalline form which may be coloured by traces of impurity, for example as ruby (red) and sapphire (blue). Small synthetic rubies and sapphires have been made by heating alumina with the colouring oxide in an oxy-hydrogen flame. 

The method of obtaining aluminum metal by the electrolysis of alumina dissolved in cryolite was discovered in 1886 by Hall in the U.S. and at about the same time by Heroult in France. Cryolite, a natural ore found in Greenland, is no longer widely used in commercial production, but has been replaced by an artificial mixture of sodium, aluminum, and calcium fluorides. 

The compounds of greatest importance are aluminum oxide, the sulfate, and the soluble sulfate with potassium (alum). The oxide, alumina, occurs naturally as ruby, sapphire, corundum, and emery, and is used in glassmaking and refractories. Synthetic ruby and sapphire are used in lasers for producing coherent light. 

Ruby Laser. Ruby (essentially alumina) owes its well-known color to the presence of very small proportions of chromium ions (Cr +) distributed through it. Ruby lasers do not use natural rubies because of the imperfections they contain. Instead, synthetic single crystals of chromium... 

Neodymium and YAG Lasers. The principle of neodymium and YAG lasers is very similar to that of the ruby laser. Neodymium ions (Nd +) are used in place of Cr + and are often distributed in glass rather than in alumina. The light from the neodymium laser has a wavelength of 1060 nm (1.06 xm) it emits in the infrared region of the electromagnetic spectrum. Yttrium (Y) ions in alumina (A) compose a form of the naturally occurring garnet (G), hence the name, YAG laser. Like the ruby laser, the Nd and YAG lasers operate from three- and four-level excited-state processes. 

Gas purifications H2O/olefin-containing cracked gas, natural gas, air, synthesis gas, etc sHica, alumina, zeoHte... 

Hydrolysis is a significant threat to phosphate ester stabiHty as moisture tends to cause reversion first to a monoacid of the phosphate ester ia an autocatalytic reaction. In turn, the fluid acidity can lead to corrosion, fluid gelation, and clogged filters. Moisture control and filtration with Fuller s earth, activated alumina, and ion-exchange resias are commonly used to minimise hydrolysis. Toxicity questions have been minimised ia current fluids by avoiding triorthocresyl phosphate which was present ia earlier natural fluids (38). 

Because the synthesis reactions are exothermic with a net decrease in molar volume, equiUbrium conversions of the carbon oxides to methanol by reactions 1 and 2 are favored by high pressure and low temperature, as shown for the indicated reformed natural gas composition in Figure 1. The mechanism of methanol synthesis on the copper—zinc—alumina catalyst was elucidated as recentiy as 1990 (7). For a pure H2—CO mixture, carbon monoxide is adsorbed on the copper surface where it is hydrogenated to methanol. When CO2 is added to the reacting mixture, the copper surface becomes partially covered by adsorbed oxygen by the reaction C02 CO + O (ads). This results in a change in mechanism where CO reacts with the adsorbed oxygen to form CO2, which becomes the primary source of carbon for methanol. 

Natural gas contains both organic and inorganic sulfur compounds that must be removed to protect both the reforming and downstream methanol synthesis catalysts. Hydrodesulfurization across a cobalt or nickel molybdenum—zinc oxide fixed-bed sequence is the basis for an effective purification system. For high levels of sulfur, bulk removal in a Hquid absorption—stripping system followed by fixed-bed residual clean-up is more practical (see Sulfur REMOVAL AND RECOVERY). Chlorides and mercury may also be found in natural gas, particularly from offshore reservoirs. These poisons can be removed by activated alumina or carbon beds. 

Methylphenol. This phenol, commonly known as o-cresol, is produced synthetically by the gas phase alkylation of phenol with methanol using modified alumina catalysis or it may be recovered from naturally occurring petroleum streams and coal tars. Most is produced synthetically. Reaction of phenol with methanol using modified zeoHte catalysts is a concerted dehydration of the methanol and alkylation of the aromatic ring. 2-Methylphenol [95-48-7] is available in 55-gal dmms (208-L) and in bulk quantities in tank wagons and railcars. 

Calcined alumina, a-Al202, and naturally occurring comndum are practically insoluble in acids and bases, but partially calcined and low temperature amorphous oxide, such as that which forms on nacent commercial aluminum surfaces, is soluble... 

---