Alkylation reaction sulfuric acid

Alkyl tertiary alkyl ethers can be prepared by the addition of an alcohol or phenol to a tertiary olefin under acid catalysis (Reycler reaction) sulfuric acid, phosphoric acid, hydrochloric acid, and boron trifluoride have all been used as catalysts ... 

Either concentrated sulfuric acid or anhydrous hydrofluoric acid is used as a catalyst for the alkylation reaction. These acid catalysts are capable of providing a proton, which reacts with the olefin to form a carbocation. For example, when propene is used with isohutane, a mixture of C5 isomers is produced. The following represents the reaction steps ... 

Liquid-liquid reactions of industrial importance are fairly numerous. A list of 26 classes of reactions with 61 references has been compiled by Doraiswamy Sharma (Heterogeneous Reactions, 1984). They also indicate the kind of reactor normally used in each case. The reactions range from prosaic examples such as making of soap with alkali, nitration of aromatics to make explosives and alkylations with sulfuric acid to make improved gasoline, to some much less familiar operations. 

Such reactions can take place predominantly in either the continuous or disperse phase or in both phases or mainly at the interface. Mutual solubilities, distribution coefficients, and the amount of interfadal surface are factors that determine the overall rate of conversion. Stirred tanks with power inputs of 5-10 HP/1000 gal or extraction-type equipment of various kinds are used to enhance mass transfer. Horizontal TFRs usually are impractical unless sufficiently stable emulsions can be formed, but mixing baffles at intervals are helpful if there are strong reasons for using such equipment. Multistage stirred chambers in a single shell are used for example in butene-isobutane alkylation with sulfuric acid catalyst. Other liquid-liquid processes listed in Table 17.1 are numbers 8, 27, 45, 78, and 90. 

The first catalyst to be used widely in commercial alkylation for the production of aviation alkylate was sulfuric acid. The catalyst in the reaction zone is normally 88 to 92 wt. % H2SO4 with the makeup acid usually having a strength of 98 % or higher. 

As has been Indicated earlier (1,2), C, olefins react to a significant, and maybe even predominant, extent before Isotutane reacts during alkylations using sulfuric acid as a catalyst. In the previous paper (3) of this series the reactions that occur when n-butene and Isobutylene were contacted with relatively small amounts of sulfuric acid In the temperature range of about -30 to -10°C were Investigated. These reactions defined as first-step reactions In the two-step alkylation process were found to be as follows ... 

The above discussion was devoted to alkylations with sulfuric acid. In the case of HF alkylations, considerable amounts of DMH s are produced however by means of the 1-butene reaction as will be considered in detail later. 

Reactions A, B, and D are predominant routes for most alkylations using sulfuric acid as the catalyst. 

Several points need to be emphasized. Eirst, the /-CgHis (frequently indicated in the literature as TMP) is really a mixture of C5-C16 isoparaffins, often with RON values in the 93-94 range. This mixture (or alkylate) is formed basically by mechanism 2 reactions. Second, when n-olefins (propylene, n-butenes, and n-pentenes) are used, the light n-paraffins formed are propane, n-butane, or n-pentane, respectively none are suitable in the gasoline pool. Third, isobutane consumption per production of a given quantity of alkylate is often increased by 6-10% when HE is employed because of the importance of mechanism 4, as compared to little or most likely no importance for alkylations with sulfuric acid. Eourth, C5 olefins are not usually used in the feedstocks when HE is the catalyst because of the large amounts of isopentane and n-pentane produced further, isobutane consumption increases. 

In sulfuric acid alkylation, concentrated sulfuric acid of 98 percent purity serves as the catalyst for the reaction that is carried out at 2 to 7°C. Refrigeration is necessary because of the heat generated by the reaction. The octane numbers of the alkylates produced range from 85 to 95. An example of sulfuric acid alkylation is shown in Figure 6.17. 

In the formation of ether and water, or of ethylene and water from alcohol and sulfuric acid, or the reverse reactions, sulfuric acid plays the part of the catalyst, and the intermediate addition compound may be represented by alkyl sulfuric acid, RSO4H, or a hydrate of it. 

Note that metal halides such as FeBrj and AICI3 are catalysts for halogenation and alkylation, and sulfuric acid is a catalyst for nitration. These reactions do not contradict the earlier discussion on the high stability of the aromatic structure. The aromatic structure is intact after these reactions. All of the reagents in these reactions bring about addition to alkenes (including the nitration and alkylation reagents which were not previously discussed in Chap. 11), but there is no addition to the double bonds in benzene, only substitution. 

Conjunct polymers have both beneficial and detrimental effects on alkylation. Fresh sulfuric acids used for alkylation normally have acidity values of 98.5-99.5% (with the remainder being water). As alkylation reactions occur, the acidity decreases to about 89-91%. At such times, the catalytic activity is generally seriously reduced, and the acid needs to be regenerated. As the acidity decreases, the concentrations of both CPs and water increase. Oft n, waste acids contain 6-8% CPs and 3- % water. Albright and co-workers (21) found that preferred sulfuric acids, at least for alkylation reactions with C4 olefins, contain about 3-6% CPs and 3-4% water. They also found that sulfuric acids containing 0.5-1.0% water were effective catalysts with acidity values as low as 85%. 

Unlike the addition of concentrated sulfuric acid to form alkyl hydrogen sulfates this reaction is carried out m a dilute acid medium A 50% water/sulfuric acid solution is often used yielding the alcohol directly without the necessity of a separate hydrolysis step Markovmkov s rule is followed... 

Although 2 methylpropene undergoes acid catalyzed hydration m dilute sulfuric acid to form tert butyl alcohol (Section 6 10) a different reaction occurs m more concentrated solutions of sulfuric acid Rather than form the expected alkyl hydrogen sulfate (see Sec tion 6 9) 2 methylpropene is converted to a mixture of two isomeric C Hig alkenes... 

Acetic anhydride adds to acetaldehyde in the presence of dilute acid to form ethyUdene diacetate [542-10-9], boron fluoride also catalyzes the reaction (78). Ethyfldene diacetate decomposes to the anhydride and aldehyde at temperatures of 220—268°C and initial pressures of 14.6—21.3 kPa (110—160 mm Hg) (79), or upon heating to 150°C in the presence of a zinc chloride catalyst (80). Acetone (qv) [67-64-1] has been prepared in 90% yield by heating an aqueous solution of acetaldehyde to 410°C in the presence of a catalyst (81). Active methylene groups condense acetaldehyde. The reaction of isobutfyene/715-11-7] and aqueous solutions of acetaldehyde in the presence of 1—2% sulfuric acid yields alkyl-y -dioxanes 2,4,4,6-tetramethyl-y -dioxane [5182-37-6] is produced in yields up to 90% (82). 

The amide group is readily hydrolyzed to acrylic acid, and this reaction is kinetically faster in base than in acid solutions (5,32,33). However, hydrolysis of N-alkyl derivatives proceeds at slower rates. The presence of an electron-with-drawing group on nitrogen not only facilitates hydrolysis but also affects the polymerization behavior of these derivatives (34,35). With concentrated sulfuric acid, acrylamide forms acrylamide sulfate salt, the intermediate of the former sulfuric acid process for producing acrylamide commercially. Further reaction of the salt with alcohols produces acrylate esters (5). In strongly alkaline anhydrous solutions a potassium salt can be formed by reaction with potassium / /-butoxide in tert-huty alcohol at room temperature (36). 

The synthesis of 2,4-dihydroxyacetophenone [89-84-9] (21) by acylation reactions of resorcinol has been extensively studied. The reaction is performed using acetic anhydride (104), acetyl chloride (105), or acetic acid (106). The esterification of resorcinol by acetic anhydride followed by the isomerization of the diacetate intermediate has also been described in the presence of zinc chloride (107). Alkylation of resorcinol can be carried out using ethers (108), olefins (109), or alcohols (110). The catalysts which are generally used include sulfuric acid, phosphoric and polyphosphoric acids, acidic resins, or aluminum and iron derivatives. 2-Chlororesorcinol [6201-65-1] (22) is obtained by a sulfonation—chloration—desulfonation technique (111). 1,2,4-Trihydroxybenzene [533-73-3] (23) is obtained by hydroxylation of resorcinol using hydrogen peroxide (112) or peracids (113). 

The susceptibihty of dialkyl peroxides to acids and bases depends on peroxide stmcture and the type and strength of the acid or base. In dilute aqueous sulfuric acid (<50%) di-Z fZ-butyl peroxide is resistant to reaction whereas in concentrated sulfuric acid this peroxide gradually forms polyisobutylene. In 50 wt % methanolic sulfuric acid, Z fZ-butyl methyl ether is produced in high yield (66). In acidic environments, unsymmetrical acychc alkyl aralkyl peroxides undergo carbon—oxygen fission, forming acychc alkyl hydroperoxides and aralkyl carbonium ions. The latter react with nucleophiles,... 

Ritter Reaction (Method 4). A small but important class of amines are manufactured by the Ritter reaction. These are the amines in which the nitrogen atom is adjacent to a tertiary alkyl group. In the Ritter reaction a substituted olefin such as isobutylene reacts with hydrogen cyanide under acidic conditions (12). The resulting formamide is then hydroly2ed to the parent primary amine. Typically sulfuric acid is used in this transformation of an olefin to an amine. Stoichiometric quantities of sulfate salts are produced along with the desired amine. 

Uses. There may be some captive use of carbonyl sulfide for production of certain thiocarbamate herbicides (qv). One patent (38) describes the reaction of diethylamine with carbonyl sulfide to form a thiocarbamate salt which is then alkylated with 4-chloroben2yl haUde to produce 3 -(4-chloroben2yl) A[,A/-diethylthiocarbamate [28249-77-6] ie, benthiocarb [28249-77-6]. Carbonyl sulfide is also reported to be useful for the preparation of abphatic polyureas. In these preparations, potassium thiocyanate and sulfuric acid are used to first generate carbonyl sulfide, COS, which then reacts with a diamine ... 

Reactions other than those of the nucleophilic reactivity of alkyl sulfates iavolve reactions with hydrocarbons, thermal degradation, sulfonation, halogenation of the alkyl groups, and reduction of the sulfate groups. Aromatic hydrocarbons, eg, benzene and naphthalene, react with alkyl sulfates when cataly2ed by aluminum chloride to give Fhedel-Crafts-type alkylation product mixtures (59). Isobutane is readily alkylated by a dipropyl sulfate mixture from the reaction of propylene ia propane with sulfuric acid (60). 

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