Isomerization aluminum chloride-hydrogen

Isopropylnaphthalenes can be prepared readily by the catalytic alkylation of naphthalene with propjiene. 2-lsopropylnaphthalene [2027-17-0] is an important intermediate used in the manufacture of 2-naphthol (see Naphthalenederivatives). The alkylation of naphthalene with propjiene, preferably in an inert solvent at 40—100°C with an aluminum chloride, hydrogen fluoride, or boron trifluoride—phosphoric acid catalyst, gives 90—95% wt % 2-isopropylnaphthalene however, a considerable amount of polyalkylate also is produced. Preferably, the propylation of naphthalene is carried out in the vapor phase in a continuous manner, over a phosphoric acid on kieselguhr catalyst under pressure at ca 220—250°C. The alkylate, which is low in di- and polyisopropylnaphthalenes, then is isomerized by recycling over the same catalyst at 240°C or by using aluminum chloride catalyst at 80°C. After distillation, a product containing >90 wt % 2-isopropylnaphthalene is obtained (47). 

The work of Petrov (288) and of Moldavskil (236) on the isomerization of some paraffins in the presence of aluminum chloride points to the similarity in temperature required for cracking and for isomerization of these paraffins in the presence of the catalyst used. Moldavskil used aluminum chloride-hydrogen chloride for isomerization of butanes and pentanes and observed a redistribution of methyl groups (241). 

Effect of Olefins upon the Isomerization of n-Bulane Catalyzed by Aluminum Chloride-Hydrogen Chloride... 

It was found (Pines and Wackher, 7) that aluminum chloride-hydrogen chloride did not cause the isomerization of n-butane to isobutane at 100°. The presence however of 1 part butenes per 10,000 parts n-butane was sufficient to cause the isomerization. When the concentration of butenes was increased to 2.5% side reactions occurred, as evidenced by the formation of higher hydrocarbons and a small amount of a viscous dark layer the latter was produced by a complex formation between the catalyst and unsaturated hydrocarbons. 

During World War II, the great demand for aircraft fuel necessitated the production of large quantities of isobutane, a basic raw material in the production of high octane aviation gasoline. (See chapter on Alkylation of Alkanes. ) Various processes have been developed for the isomerization of n-butane to isobutane all of them employed aluminum chloride-hydrogen chloride as catalyst. The difference between the various processes consisted either in the method of introduction of aluminum chloride to the reaction zone, the catalyst support, or the state of the catalyst. The following summary describes some of the main features of the various processes which were developed ... 

These experimental data, summarized in Table XXV show that aluminum chloride-hydrogen chloride caused a great deal of decomposition of n-pentane. The addition of a little benzene inhibited both isomerization and the cracking of n-pentane. The effect of benzene was pronounced even when the concentration of hydrogen chloride was increased from 1 to 7%. 

The mechanism described above does not explain the fact that imder controlled conditions, benzene in the presence of aluminum chloride-hydrogen chloride catalyst, inhibits not only the cracking but also the isomerization reaction (Table XXV, experiment 3) while in the absence of benzene cracking is the predominant reaction. The mechanism postulated above does not take into consideration the observations made that under controlled conditions saturated hydrocarbons such as methylcyclopentane, cyclohexane, or butanes (7, 23, 35) do not undergo isomerization, unless traces of olefins are present. 

Initially, aluminum chloride was the catalyst used to isomerize butane, pentane, and hexane. Siace then, supported metal catalysts have been developed for use ia high temperature processes that operate at 370—480°C and 2070—5170 kPa (300—750 psi), whereas aluminum chloride and hydrogen chloride are universally used for the low temperature processes. 

The demand for aviation gasoline during World War II was so great that isobutanc from alkylation feedstock was insufficient. This deficiency was remedied by isomerization of abundant normal butane into isobutane using the isomerization catalyst aluminum chloride on alumina promoted by hydrogen chloride gas. 

Catalysts like hydrogen fluoride or aluminum chloride catalyze not only the alkylation but the side reactions such as polymerization, isomerization, and disproportionation of tetrapropylene. All three side reactions are observed. In... 

The process involves first separating mixed butane compounds by distillation to isobutane and n-butane. The n-butane is then mixed with hydrogen, heated and passed through a reactor containing a platinum catalyst or an HC1 activated aluminum chloride catalyst. The n-butane is isomerized to isobutane and separated. 

Frjedel-Crafts Reaction. Any organic reaction brought about by the catalytic action of anhydrous aluminum chloride or related, so-called Lewis acid type catalysts. Discovered in 1877 by C. Friedel and J.M. Crafts, who later uncovered most of the types of reaction such as substitution, isomerization, elimination, cracking, olefin polymerization, addition, etc. Commonly used to displace an aromatic hydrogen atom with an alkyl, aryl or acyl chain... 

Catalyst. In all of the commercial isomerization processes applied to paraffins and naphthenes, the catalyst is aluminum chloride plus hydrogen chloride. In the pure state, these two ingredients do not associate chemically (1), but they become associated in the presence of certain hydrocarbons normally occurring in petroleum stocks. 

The butane isomerization process developed by the Universal Oil Products Co. is shown in Figure 4. In this process (3), the feed is maintained essentially in the liquid phase under pressure. Part of the feed is by-passed through a saturator, where it dissolves aluminum chloride. The feed later picks up hydrogen chloride and passes through the reactor, which is packed with quartz chips. Some insoluble liquid complex is formed, and this adheres to the quartz chips. The aluminum chloride in the feed is preferentially taken up by the complex, which thus maintains an active catalyst bed. The complex slowly drains through the reactor, losing activity en route. It arrives at the bottom in essentially spent condition and is discarded. Aluminum chloride carried overhead in the reactor products is returned to the reactor from the bottom of the recovery tower. The rest of the process is the same as in the vapor-phase processes. 

The other commercialized pentane isomerization process is that of the Standard Oil Co. (Indiana) (20). This process differs from the Indiana-Texas butane process in that the aluminum chloride is introduced as a slurry directly to the reactor and that about 0.5% by volume of benzene is added continuously in the feed to suppress side reactions. Temperature, catalyst composition, space velocity, and hydrogen chloride concentration are generally similar to those in the corresponding butane process, but the reactor pressure is about 100 pounds lower. The Pan American Refining Co. operated the Indiana pentane isomerization process commercially during the last nine months of the war and produced about 400 barrels of isopentane per calendar day. 

In 1946 Bloch, Pines, and Schmerling17 observed that w-butane (1) isomerizes to isobutane (2) under the influence of pure aluminum chloride only in the presence of HC1. They proposed that the ionization step takes place through initial protolysis of the alkane as evidenced by formation of minor amounts of hydrogen in the initial stage of the reaction [Eq. (5.1)]. 

Butane vapor-phase isomerization a process for isomerizing n-butane to iso-butane using aluminum chloride catalyst on a granular alumina support and with hydrogen chloride as a promoter. 

Interestingly, the comparable monocation (190) is not reactive towards benzene or cyclohexane. This is an indication of the superelectrophilic character of dication 188. The isomeric hydroxyquinolines and 5-hydroxy-isoquinoline react with 5-7 molar excess of aluminum chloride and cyclohexane at 90°C to give ionic hydrogenation products, and the corresponding distonic superelectrophiles (191-193) are proposed as intermediates. 

In certain reactions, such as the isomerization of butane and the alkylation of isoparaffins, problems of handling hydrogen chloride and acidic sludge are encountered. The corrosive action of the aluminum chloride-hydrocarbon complex, particularly at 70 to 100°C, has long been recognized and various reactor liners have been found satisfactory. 

When treated with aluminum chloride in refluxing hexane, perhydrotriquinacene was rapidly isomerized to adamantane.382 Exposure of 1-, exo-2, or endo-2-per-hydrotriquinacenol to fluorosulfonic acid, followed by aqueous quenching, has been shown to produce 1-adamantanol. McKervey and his co-workers have found that 358 exchanges ten hydrogen atoms when subjected to exchange with deuterium and palladium.385 On this basis, the prediction was made that olefin 409 (presently an unknown molecule) should be a compound of moderate stability. 

In all commercial processes for isomerizing paraffins and naphthenes, the catalyst is essentially aluminum chloride plus hydrogen chloride. The... 

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