Hydration isobutylene

V. P. Gupta and W. J. M. Douglas [AIChE J., 13 (1967) 883] carried out the isobutylene hydration reaction with excess water in a stirred tank reactor utilizing a cationic exchange resin as the catalyst. Use the following data to determine the effectiveness factor for the ion exchange resin at 85°C and 3.9 percent conversion. 

The inactivity of pure anhydrous Lewis acid haUdes in Friedel-Crafts polymerisation of olefins was first demonstrated in 1936 (203) it was found that pure, dry aluminum chloride does not react with ethylene. Subsequentiy it was shown (204) that boron ttifluoride alone does not catalyse the polymerisation of isobutylene when kept absolutely dry in a vacuum system. However, polymers form upon admission of traces of water. The active catalyst is boron ttifluoride hydrate, BF H20, ie, a conjugate protic acid H" (BF20H) . 

Butanol is produced commercially by the indirect hydration of / -butenes. However, current trends are towards the employment of inexpensive Raffinate 11 type feedstocks, ie, C-4 refinery streams containing predominandy / -butenes and saturated C-4s after removal of butadiene and isobutylene. In the traditional indirect hydration process, / -butenes are esterified with Hquid sulfuric acid and the intermediate butyl sulfate esters hydroly2ed. DEA Mineraloel (formerly Deutsche Texaco) currentiy operates a 2-butanol plant employing a direct hydration of / -butenes route (18) with their own proprietary catalyst. 

The other significant industrial route to /-butyl alcohol is the acid cataly2ed hydration of isobutylene (24), a process no longer practiced in the United States. Raffinate 1, C-4 refinery streams containing isobutylene [115-11-7], / -butenes and saturated C-4s or C-4 fluid catalytic cracker (ECC) feedstocks (23)... 

Butyl alcohol, obtained from hydration of Raffinate 1, can be dehydrated and subsequently refined to high purity, polymer-grade isobutylene (25). Alternatively, the isobutylene from alcohol dehydration can react with methanol in the presence of an acid catalyst to give methyl /-butyl ether (MTBE) gasoHne additive (see Ethers organic). 

Sulfuric acid is about one thousand times more reactive with isobutylene than with the 1- and 2-butenes, and is thereby very useful in separating isobutylene as tert-huty alcohol from the other butenes. The reaction is simply carried out by bubbling or stirring the butylenes into 45—60% H2SO4. This results in the formation of tert-huty hydrogen sulfate. Dilution with water followed by heat hydrolyzes the sulfate to form tert-huty alcohol and sulfuric acid. The Markovnikov addition implies that isobutyl alcohol is not formed. The hydration of butylenes is most important for isobutylene, either directiy or via the butyl hydrogen sulfate. 

Examples are given of common operations such as absorption of ammonia to make fertihzers and of carbon dioxide to make soda ash. Also of recoveiy of phosphine from offgases of phosphorous plants recoveiy of HE oxidation, halogenation, and hydrogenation of various organics hydration of olefins to alcohols oxo reaction for higher aldehydes and alcohols ozonolysis of oleic acid absorption of carbon monoxide to make sodium formate alkylation of acetic acid with isobutylene to make teti-h ty acetate, absorption of olefins to make various products HCl and HBr plus higher alcohols to make alkyl hahdes and so on. 

C4 cuts, after extraction of butadiene, are preferred as feed to isobutylene extraction units because the isobutylene concentration (about 30-40%) is higher than in C4 streams from catalytic cracking. The basic reaction in isobutylene extraction is the reversible hydration of isobutylene to tertiary butyl alcohol in the presence of sulfuric acid. 

The acid-catalyzed hydration of isobutylene produces ter-butyl alcohol. The reaction occurs in the liquid phase in the presence of 50-65% H2SO4 at mild temperatures (10-30°C). The yield is approximately 95% ... 

Gupta and Douglas [AIChE J., 13 (883), 1967] have studied the catalytic hydration of isobutylene to f-butanol, using a cation exchange resin catalyst in a stirred tank reactor. 

The rate of hydration of an olefin increases with acidity. It has recently been demonstrated that the hydration of isobutylene follows the Ho acidity function, i.e. dlogkj — dHo) = 1, where Hq is the acidity function defined by equation (10). The behaviour of secondary and tertiary alcohols in 0-55 % H2SO4 is very similar (Beishlin, 1963). 

Unfortunately, secondary and tertiary butyl alcohols (SBA and TBA) cannot be made by the Oxo process. Instead they are produced either by indirect or direct hydration of the corresponding olefin. Normal butylene gives SBA and isobutylene gives TBA. The processes are similar to the corresponding routes to IPA. 

Synthesis gas is also the precursor to MTBE via methanol. The process requires isobutylene as well. Ethyl alcohol is made by direct, catalyzed hydration of ethylene. The route to isopropyl alcohol historically used to be solely indirect hydration of propylene, which occurs at much lower pressures and temperatures than the direct method, but advances in catalysis now make the direct route competitive. 

Water has also been shown to be essential for the liquid phase polymerization of isobutylene with stannic chloride as catalyst (Norrish and Russell, 87). The rates of reaction were measured by a dilatometric method using ethyl chloride as common solvent at —78.5°. With a mixture consisting of 1.15% stannic chloride, 20 % isobutylene, and 78.8% ethyl chloride, the rate of polymerization was directly proportional to the amount of added water (up to 0.43% of which was added). A rapid increase in the rate of polymerization occurred as the stannic chloride concentration was increased from 0.1 to 1.25% with higher concentrations the rate increased only gradually. It was concluded that a soluble hydrate is formed and functions as the active catalyst. The minimum concentration of stannic chloride below which no polymerization occurred was somewhat less than half the percentage of added water. When the concentration of the metal chloride was less than about one-fifth that of the added water, a light solid precipitated formation of this insoluble hydrate which had no catalytic activity probably explains the minimum catalyst concentration. The addition of 0.3% each of ethyl alcohol, butyl alcohol, diethyl ether, or acetone in the presence of 0.18% water reduced the rate to less than one-fifth of its normal value. On the other hand, no polymerization occurred on the addition of 0.3 % of these substances in the absence of added water. The water-promoted reaction was halved when 1- and 2-butene were present in concentrations of 2 and 6%, respectively. 

Solid superacidic Nafion-H was also found to be effective in the hydration of acyclic alkenes.16 Isopropyl alcohol was produced with 97% selectivity in hydrating propylene17 at 150°C, whereas isobutylene yielded tert-butyl alcohol18 with 84% selectivity at 96°C. 

Ion exchange resins are used widely as heterogeneous catalysts of processes that require acid or base catalysis, for example, hydration of propylene to isopropanol, reaction of isobutylene with acetonitrile, and many others. The same kind of equipment is suitable as for ion exchange, but usually regeneration is not necessary, although some degradation of the resin naturally occurs over a period of time. 

Among the many alkyl-substituted epoxides that have hi n reported to undergo hydration under various conditions are propylnm oxide, isobutylene oxide, 1,2-epoxybutone, trimethylethylene oxide, and others-. . . , jtf, i w. . shown in JSq, (50 ). 

Pritchard and Long1416-141 studied the distribution of lsO in products obtained on hydration of propylene oxide and isobutylene oxide in Hs180, both in alkaline and in acid solutions (Eqs. 611 and 612). Their results are consistent with the premise that attack by water occurs predominantly on the terminal epoxide carbon atom, unless an... 

Pseudoliquid-phase catalysis (bulk type I catalysis) was reported in 1979, and bulk type II behavior in 1983. In the 1980s, several new large-scale industrial processes started in Japan based on applications of heteropoly catalysts that had been described before (5, 6, 72) namely, oxidation of methacro-lein (1982), hydration of isobutylene (1984), hydration of n-butene (1985), and polymerization of tetrahydrofuran (1987). In addition, there are a few small- to medium-scale processes (9, 10). Thus the level of research activity in heteropoly catalysis is very high and growing rapidly. 

Fig. 24. Dependences of the initial rate of TBA formation and ratio of DIP/TBA on H3PMo,2O40 concentration in the hydration of butenes. TBA, lerl-butyl alcohol DIB, diisobutylene. 357 K, isobutylene/1-butene = 1/1 (molar). (From Ref. 163.)...

Izumi et al. (162, 166) observed high activities of heteropolyacids for the hydration of isobutylene in dilute solution, as follows. The activation energy is 4 kcal mol 1 lower for H3PW12O40 than for HNO3. The reaction order with... 

A commercial process for the separation of isobutylene from a mixture of isobutylene and -butenes through direct hydration of isobutylene to give tert-butyl alcohol has been established by use of a concentrated solution of heteropolyacids (6, 163, 170). The reaction order in the heteropolyanion varies from 1 to 2 as the concentration of heteropolyanion increases from 0.05 to 10 mol dm-3. This increase corresponds to a change from the first to the second term in Eq. (11a). At concentration of the heteropolyanion greater than 0.5 mol dm-3, path B in Scheme 3 becomes dominant. 

The data of H2S04, HC1, HNO3, and HC104 also fit this equation. On this basis, they suggested that the hydration of isobutylene in the presence of heteropolyacids and inorganic acids proceeds via a common mechanism, in which the rate-limiting step is the conversion of the 7t-complex into a carbenium ion (Scheme 3). The complexation effect as described above is possibly included in the value of Ho according to this explanation. 

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