Silica-alumina high-temperature acid

The reaction of u-butenes to give isobutylene is cataly zed by a wide variety of solid acids but requires relatively high temperature. Typical catalysts include alumina, halogenated alumina, amorphous silica-alumina, supported phosphoric acid, and supported tungsten or molybdemmi oxide. The most characteristic features of the skeletal isomerization of n-butenes... 

Besides catalyst exploration, we were also exploring other feed stocks besides our standard test gas oil and also doing some catalytic cracking of pure hydrocarbons with silica-alumina. This led to the conclusion that the silica-alumina must be a high temperature acid a concept that came gradually rather than a "flash of genius". 

There remained the question How can silica-alumina be a high temperature acid Minerology described many minerals in... 

A conventional FCC unit can be an olefin machine with proper operating conditions and hardware. Catalysts with a low unit cell size and a high silica/alumina ratio favor olefins. Additionally, the addition of ZSM-5, with its lower acid site density and very high framework silica-alumina ratio, converts gasoline into olefins. A high reactor temperature and elimination of the post-riser residence time will also produce more olefins. Mechanical modification of the FCC riser for millisecond cracking has shown potential for maximizing olefin yield. 

Silica-alumina is the most popular mixed oxide support, combining characteristic features of silica and alumina, including (i) high surface area, (ii) persistent OH population at high temperature and (iii) strong Lewis acidic sites. The predominant surface hydroxyl groups on silica-alumina are [=Si-OH], while [Als-OH] surface species have not been observed [79, 89, 90]. Note that the silica-alumina bulk is mainly composed of [=Si-0-Si=] along with [=Si-0-Als] moieties (Lewis... 

Metallic beryllium is produced by reduction of beryllium halide with sodium, potassium or magnesium. Commercially, it is obtained primarily from its ore, beryl. Beryllium oxide is separated from silica and alumina in ore by melting the ore, quenching the solid solution, and solubilizing in sulfuric acid at high temperatures and pressure. Silica and alumina are removed by pH adjustment. Beryllium is converted to its hydroxide. Alternatively, beryl is roasted with complex fluoride. The products are dissolved in water and then pH is adjusted to produce beryllium hydroxide. 

Although sulphuric acid expels many other acids from their salts, it can in a similar manner be displaced from its own salts by heating with still less volatile acids such as phosphoric or boric acid or even with silica or alumina 6 on account of the high temperature necessary, the liberated sulphuric acid or anhydride is partly decomposed into sulphur dioxide. 

J-Butyl Ether. -Butyl ether is prepared by dehydration of -butyl alcohol by sulfuric acid or by catalytic dehydration over ferric chloride, copper sulfate, silica, or alumina at high temperatures. It is an important solvent for Grignard reagents and other reactions that require an anhydrous, inert medium. /7-Butyl ether is also an excellent extracting agent for use with aqueous systems owing to its very low water-solubility. 

Although a variety of amines, particularly trimethylamine and n-butylamine have widely been used as poisons in catalytic reactions and for surface acidity determinations (20), comparably few spectroscopic data of adsorbed amines are available. As with ammonia, coordinatively adsorbed amines held by co-ordinatively unsaturated cations have preferentially been found on pure oxides (176, 193-196), whereas the protonated species were additionally observed on the surfaces of silica-aluminas and zeolites (196-199). However, protonated species have also been detected on n-butylamine adsorption on alumina (196) and trimethylamine adsorption on anatase (176) due to the high basicity of these aliphatic amines. In addition, there is some evidence for dissociative adsorption of n-butylamine (196) and trimethylamine (221) on silica-alumina. Some amines undergo chemical transformations at higher temperatures (195, 200) and aromatic amines, such as diphenylamine, have been shown to produce cation radicals on silica-alumina (201, 201a). 

Beginning in 1956, E. M. Flanigen learned how to make X with silica/alumina ratios between 4.0 and 5.7. Now with a full range of ratios from 2.5 to 5.7, we were able to study systematically the variation in properties with alumina content. Breck s original hypothesis proved to be correct. The high silica forms were more stable to acid attack and to high temperatures in the presence of water vapor than the low silica forms [23]. 

Breck s preparation of type Y faujasite in die late 1950 s still stands as the outstanding success in zeolite synthesis (2). Type X might have had some catalytic applications but I doubt the International Zeolite Association would exist without the interest and support generated by the catalytic applications of the Type Y materials. It didn t seem that critical at the time after all Breck had reproduced a material which exists naturally. Synthetic counterparts of natural zeolites have been prepared dozens of times since (3). But die extra silica content, or perhaps die diminished alumina content, was enough to give high temperature stability in the acid form and to get zeolites into catalysts for petroleum processes (4). 

The acidic solid catalysts, such as silica-alumina are very active for the conversion of olefins to skeletal isomers. Evidence for such high reactivity, at relatively low temperatures, can be found, for example, in the early work of Egloff et al. 20), and of Greensfelder and Voge 21). 

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