Processes isobutane process

There are other commercial processes available for the production of butylenes. However, these are site or manufacturer specific, eg, the Oxirane process for the production of propylene oxide the disproportionation of higher olefins and the oligomerisation of ethylene. Any of these processes can become an important source in the future. More recentiy, the Coastal Isobutane process began commercialisation to produce isobutylene from butanes for meeting the expected demand for methyl-/ rZ-butyl ether (40). 

The catalyst is reported to be a true solid acid without halogen ion addition. In the patent describing the process (239), a Pt/USY zeolite with an alumina binder is employed. It was claimed that the catalyst is rather insensitive to feed impurities and feedstock composition, so that feed pretreatment can be less stringent than in conventional liquid acid-catalyzed processes. The process is operated at temperatures of 323-363 K, so that the cooling requirements are less than those of lower temperature processes. The molar isobutane/alkene feed ratio is kept between 8 and 10. Alkene space velocities are not reported. Akzo claims that the alkylate quality is identical to or higher than that attained with the liquid acid-catalyzed processes. 

Isobutane process i-C4Hio, air One-step catalytic oxidation Several companies... 

Butane isomerization and pentane-hexane isomerization are the two most important isomerization processes. Isobutane is utilized primarily as alkylate feedstock. Isopentanes and isohexanes have become valuable high-octane blending components in gasoline. 

Feed stock for the first sulfuric acid alkylation units consisted mainly of butylenes and isobutane obtained originally from thermal cracking and later from catalytic cracking processes. Isobutane was derived from refinery sources and from natural gasoline processing. Isomerization of normal butane to make isobutane was also quite prevalent. Later the olefinic part of the feed stock was expanded to include propylene and amylenes in some cases. When ethylene was required in large quantities for the production of ethylbenzene, propane and butanes were cracked, and later naphtha and gas oils were cracked. This was especially practiced in European countries where the cracking of propane has not been economic. 

Isobutene is present in refinery streams. Especially C4 fractions from catalytic cracking are used. Such streams consist mainly of n-butenes, isobutene and butadiene, and generally the butadiene is first removed by extraction. For the purpose of MTBE manufacture the amount of C4 (and C3) olefins in catalytic cracking can be enhanced by adding a few percent of the shape-selective, medium-pore zeolite ZSM-5 to the FCC catalyst (see Fig. 2.23), which is based on zeolite Y (large pore). Two routes lead from n-butane to isobutene (see Fig. 2.24) the isomerization/dehydrogenation pathway (upper route) is industrially practised. Finally, isobutene is also industrially obtained by dehydration of f-butyl alcohol, formed in the Halcon process (isobutane/propene to f-butyl alcohol/ propene oxide). The latter process has been mentioned as an alternative for the SMPO process (see Section 2.7). 

In the isobutane process the f-butanol (TBA) co-product is converted to the gasoline additive, methyl t-butyl ether (MTBE), via dehydration to isobutene and reaction with methanol. The theoretical weight ratio of TBA/PO is 1.32 1 but commercial plants produce 2-3 kg TBA per kg, depending on demand. Because of the very large gasoline pool, marketing 2-3 kg of TBA per kg PO is not a problem. 

Typical mixtures that can be separated by extractive distillation in processes similar to the one described above include cyclohexane and benzene, and toluene and methylcyclohexane, both using phenol as the solvent. In another process, isobutane and 1-butene are separated using furfural as the solvent. 

FI, 7.4. Propylene oxide production by oxidation with peroxide compounds. ARCO Chemical (Oxirunc) process, isobutane version. 1 - I... 

The low operating pressure and temperature of CATOFIN reactors, along with the robust Sud-Chemie catalyst, allows the CATOFIN technology to process isobutane feedstock without fouling of process... 

The oxirane process for the epoxidation of propene is of industrial importance. In this process, isobutane is oxidized with air to tert-butyl hydroperoxide, preferably with hard Mo and Mo salts as catalysts. The hydroperoxide then oxidizes the propene. 

Ethylene oxide was conventionally prepared by reacting CI2, ethylene, and water to produce chlorohydrin, which is further treated with caustic to generate the oxide. This process was superseded by the direct oxidation of ethylene in the presence of silver catalysts with air or oxygen. The isobutane process displaced the route fiom propylene chlorohydrin to produce PO. Another significant loss was the conversion of DuPont s hexamethylene diamine process from butadiene to a non-chlorine-based technology. All these changes led to a loss of 140 000 tons of market demand for chlorine. 

In the first process, isobutane is oxidized by air at 120-150°C and about 3 MPa (30 atmospheres) to give fert-butyl hydroperoxide. This is then treated with propylene in the liquid phase at 120-140°C and about 3.5 MPa (35 atmospheres) in the presence of a molybdenum catalyst to give propylene oxide. tert-Butyl alcohol is obtained as a by-product. In the second process, ethylbenzene is utilized under similar conditions and 1-phenylethanol (which can be dehydrated to styrene) is the by-product. 

Sulfuric Acid Process. This process has been applied primarily to isobutane and butenes. The absorption of the olefin hydrocarbon occurs at a rate several hundred times as fast as the absorption of paraffins, and hence in order to maintain the proper concentration of the two hydrocarbons in the acid it is necessary to recycle a large excess of the saturated... 

Alkylation is a process that produces high octane number (RON and MON) components from light olefins ( 3=, 4=, 05=) by addition of isobutane. 

Butane-Naphtha Catalytic Liquid-Phase Oxidation. Direct Hquid-phase oxidation ofbutane and/or naphtha [8030-30-6] was once the most favored worldwide route to acetic acid because of the low cost of these hydrocarbons. Butane [106-97-8] in the presence of metallic ions, eg, cobalt, chromium, or manganese, undergoes simple air oxidation in acetic acid solvent (48). The peroxidic intermediates are decomposed by high temperature, by mechanical agitation, and by action of the metallic catalysts, to form acetic acid and a comparatively small suite of other compounds (49). Ethyl acetate and butanone are produced, and the process can be altered to provide larger quantities of these valuable materials. Ethanol is thought to be an important intermediate (50) acetone forms through a minor pathway from isobutane present in the hydrocarbon feed. Formic acid, propionic acid, and minor quantities of butyric acid are also formed. 

Products do not contain 2,2,3-trimethylbutane or 2,2,3,3-tetramethylbutane, which would be expected as the primary alkylation products of direct alkylation of isobutane with propylene and isobutylene, respectively. In fact, the process iavolves alkylation of the alkenes by the carbocations produced from the isoalkanes via intermolecular hydride abstraction. 

Methyl /-Butyl Ether. MTBE is produced by reaction of isobutene and methanol on acid ion-exchange resins. The supply of isobutene, obtained from hydrocarbon cracking units or by dehydration of tert-huty alcohol, is limited relative to that of methanol. The cost to produce MTBE from by-product isobutene has been estimated to be between 0.13 to 0.16/L ( 0.50—0.60/gal) (90). Direct production of isobutene by dehydrogenation of isobutane or isomerization of mixed butenes are expensive processes that have seen less commercial use in the United States. 

Propylene oxide [75-56-9] is manufactured by either the chlorohydrin process or the peroxidation (coproduct) process. In the chlorohydrin process, chlorine, propylene, and water are combined to make propylene chlorohydrin, which then reacts with inorganic base to yield the oxide. The peroxidation process converts either isobutane or ethylbenzene direcdy to an alkyl hydroperoxide which then reacts with propylene to make propylene oxide, and /-butyl alcohol or methylbenzyl alcohol, respectively. Table 1 Hsts producers of propylene glycols in the United States. 

Butanes are naturally occurring alkane hydrocarbons that are produced primarily in association with natural gas processing and certain refinery operations such as catalytic cracking and catalytic reforming. The term butanes includes the two stmctural isomers, / -butane [106-97-8] CH2CH2CH2CH2, and isobutane [79-28-9], (CH2)2CHCH2 (2-methylpropane). 

Isomerization. Stmctural isomerization of / -butane to isobutane is commercially useful when additional isobutane feedstock is needed for alkylation (qv). The catalysts permit low reaction temperatures which favor high proportions of isobutane in the product. The Butamer process also is well known for isomerization of / -butane. 

Production of maleic anhydride by oxidation of / -butane represents one of butane s largest markets. Butane and LPG are also used as feedstocks for ethylene production by thermal cracking. A relatively new use for butane of growing importance is isomerization to isobutane, followed by dehydrogenation to isobutylene for use in MTBE synthesis. Smaller chemical uses include production of acetic acid and by-products. Methyl ethyl ketone (MEK) is the principal by-product, though small amounts of formic, propionic, and butyric acid are also produced. / -Butane is also used as a solvent in Hquid—Hquid extraction of heavy oils in a deasphalting process. 

One of the most efficient implementations of the slurry process was developed by Phillips Petroleum Company in 1961 (Eig. 5). Nearly one-third of all HDPE produced in the 1990s is by this process. The reactor consists of a folded loop with four long (- 50 m) vertical mns of a pipe (0.5—1.0 m dia) coimected by short horizontal lengths (around 5 m) (58—60). The entire length of the loop is jacketed for cooling. A slurry of HDPE and catalyst particles in a light solvent (isobutane or isopentane) circulates by a pump at a velocity of 5—12 m/s. This rapid circulation ensures a turbulent flow, removes the heat of polymeriza tion, and prevents polymer deposition on the reactor walls. 

Phillips Petroleum Company developed an efficient slurry process used for the production of both HDPE and LLDPE (Eig. 6). The reactor is built as a large folder loop containing long mns of pipe from 0.5 to 1 m ia diameter coimected by short horizontal stretches of pipe. The reactor is filled with a light solvent (usually isobutane) which circulates through the loop at high speed. A mixed stream containing ethylene and comonomers (1-butene,... 

The catalysts used in the industrial alkylation processes are strong Hquid acids, either sulfuric acid [7664-93-9] (H2SO or hydrofluoric acid [7664-39-3] (HE). Other strong acids have been shown to be capable of alkylation in the laboratory but have not been used commercially. Aluminum chloride [7446-70-0] (AlCl ) is suitable for the alkylation of isobutane with ethylene (12). Super acids, such as trifluoromethanesulfonic acid [1493-13-6] also produce alkylate (13). SoHd strong acid catalysts, such as Y-type zeoHte or BE -promoted acidic ion-exchange resin, have also been investigated (14—16). 

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