Methyl/-butyl ether production

Methyl -butyl ether production is the single largest consumer of butylenes. Liquid phase reaction of methanol with isobutylene in the presence of an acidic ion-exchange resin catalyst at temperatures of below 100°C and moderate pressures give excellent yields of this oxygenated gasoline additive (Eq. 19.54). 

Isobutyl alcohol [78-83-1] forms a substantial fraction of the butanols produced by higher alcohol synthesis over modified copper—zinc oxide-based catalysts. Conceivably, separation of this alcohol and dehydration affords an alternative route to isobutjiene [115-11 -7] for methyl /-butyl ether [1624-04-4] (MTBE) production. MTBE is a rapidly growing constituent of reformulated gasoline, but its growth is likely to be limited by available suppHes of isobutylene. Thus higher alcohol synthesis provides a process capable of supplying all of the raw materials required for manufacture of this key fuel oxygenate (24) (see Ethers). 

Capacity Limitations and Biofuels Markets. Large biofuels markets exist (130—133), eg, production of fermentation ethanol for use as a gasoline extender (see Alcohol fuels). Even with existing (1987) and planned additions to ethanol plant capacities, less than 10% of gasoline sales could be satisfied with ethanol—gasoline blends of 10 vol % ethanol the maximum volumetric displacement of gasoline possible is about 1%. The same condition apphes to methanol and alcohol derivatives, ie, methyl-/-butyl ether [1634-04-4] and ethyl-/-butyl ether. 

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. 

High temperature steam reforming of natural gas accounts for 97% of the hydrogen used for ammonia synthesis in the United States. Hydrogen requirement for ammonia synthesis is about 336 m /t of ammonia produced for a typical 1000 t/d ammonia plant. The near-term demand for ammonia remains stagnant. Methanol production requires 560 m of hydrogen for each ton produced, based on a 2500-t/d methanol plant. Methanol demand is expected to increase in response to an increased use of the fuel—oxygenate methyl /-butyl ether (MTBE). 

Methyl -Butyl Ether. MTBE is used as an oxygen additive foi gasoline. Production of MTBE in tiie United States has increased due to the... 

CATOFIN [CATalytic OleFIN] A version of the Houdry process for converting mixtures of C3 - C5 saturated hydrocarbons into olefins by catalytic dehydrogenation. The catalyst is chromia on alumina in a fixed bed. Developed by Air Products Chemicals owned by United Catalysts, which makes the catalyst, and licensed through ABB Lummus Crest. Nineteen plants were operating worldwide in 1991. In 1994, seven units were used for converting isobutane to isobutylene for making methyl /-butyl ether for use as a gasoline additive. 

Meanwhile, many other chemicals have enabled our society to accomplish great technical advances. For example, we have learned to recover fossil hydrocarbons from the earth and use these for heating, for transportation fuels, and for synthetic starting materials. Likewise, synthetic compounds like tetraethyllead, chlorinated solvents, freons, methyl /-butyl ether (MTBE), polychlorinated biphenyls (PCBs), and many others (see Chapter 2) have enabled us to develop products and perform industrial processes with greater efficiencies and safety. However, it has become quite apparent that even such contained applications always result in a certain level of discharge of these compounds to the environment. 

Oxirane Process. In Arco s Oxiiane process, tert-buty alcohol is a by-product in the production of propylene oxide from a propylene—isobutane mixture. Polymer-grade isobutylene can be obtained by dehydration of the alcohol, tert-Butyl alcohol [75-65-0] competes directly with methyl-/ -butyl ether as a gasoline additive, but its potential is limited by its partial miscibility with gasoline. Current surplus dehydration capacity can be utilized to produce isobutylene as more methyl-/ -butyl ether is diverted as high octane blending component. 

The synthesis of methyl /-butyl ether (MTBE) from isobutylene and methanol on TS-1 has been investigated. This reaction is catalyzed by acids and the industrial production is carried out with sulfonic acid resin catalysts. It has been reported that at 363-383 K the reaction proceeds in the presence of the acidic HZSM-5, but also on TS-1, which is much more weakly acidic. However, the characterization of the catalysts used is not completely satisfactory for instance, the IR spectra reported do not show the 960-cm 1 band that is always present in titanium-containing silicas. It is therefore possible that the materials with which the reaction has been studied are not pufe-phase TS-1. The catalytic activity for MTBE synthesis is, in any case, an interesting result, and further investigations with fully characterized catalysts are expected to provide a satisfactory interpretation of these results (Chang et al., 1992). 

Irradiation of (S )-tropolone 2-methyl butyl ether in solution yields a 4-electron electrocyclization product as a 1 1 diastereomeric mixture (Sch. 8) [106]. In solution the presence of the chiral auxiliary in proximity to the reactive center has no influence on the product stereochemistry. When irradiated within NaY zeolite, however, the same molecule affords the cyclized product in 53% diastereomeric excess. The restricted space of the zeolite supercage apparently forces communication between the chiral center and the reaction site. 

McMillan and Wijnen87 in a more thorough investigation, detected small amounts of methyl (-butyl ether and f-butylene oxide in the products which were accounted for by the following reactions ... 

A homogeneous catalytic process, developed by Oxirane, uses a molybdenum catalyst that epoxidizes propylene by transferring an oxygen atom from tertiary butyl hydroperoxide. This is shown by 8.28. The hydroperoxide is obtained by the auto-oxidation of isobutane. The co-product of propylene oxide, /-butanol, finds use as an antiknock gasoline additive. It is also used in the synthesis of methyl /-butyl ether, another important gasoline additive. The over-... 

Mitsubishi Rayon in Japan has commercialized a three-step process on the basis of a two-step catalytic oxidation of isobutene, preferentially through f-butanol as primary intermediate. This process suffers not only from a relatively moderate overall MMA yield ( 80%), but also from increasing isobutene cost due to its alternative use for MTBE (methyl fert.-butyl ether) production as a gasoline additive. 

Major end uses for methanol are for the production of formaldehyde, about 30%, which is used for the preparation of phenol-formaldehyde resins. About 20% is used for the production of methyl -butyl ether, which is used as an additive alone, and in blends with methanol as a fuel component. Further uses are for the esterification of terephthalic, and acrylic acids, and for acetic acid preparation, about 10% each. 

Isobutylene itself ranks 38th in volume in the American chemical industry. Its two major uses are for the production of methyl -butyl ether and 1,3-butadiene, which stood 12th and 36th in volume of production in 1995. 

Commercial production of methyl -butyl ether began in 1979, shortly after the discovery of its octane-improving capability for motor fuels. Although a higher proportion of this additive was required for equivalent octane enhancement, it was less costly and eliminated the lead particulate discharges associated with the tetraethyl lead previously used (Chap. 18). By 1984 it ranked 49th in American volume of production and jumped to 12th by 1995, an... 

The design equations for a single-feed distillation column using these variables have been formulated by Barbosa and Doherty (1988a,b,c) (see also Rev, 1994). The procedure has been extended to multiple reactions by several authors (see, e.g., Ung and Doherty, 1994a,b,c, and Kolah et al., 1996). The appearance of multiple steady states in the solution of the DCR equations has also been considered (Huan et al., 1995) in methyl-/ert-butyl ether production. 

U.S. methanol production in 1993 amounted to 4 8 Mt, but demand possibly exceeded 8 Mt, the difference being met by imports. The increased production of MTBE (methyl /-butyl ether, see section 12.9.3) appears to have consumed some 4Mt of methanol, compared with l 45Mt for formaldehyde (1-3 Mt, 100% bases) and possibly 0 7-0 8Mt for the carbonylation routes to acetic acid anhydride. (Amino-, phenolic- and polyacetal-resins accounted for 27%, 22% and 12% of formaldehyde use respectively, and C4 diols about 12%.)... 

Most -butanol is now obtained as a co-product of Arco s propylene oxide manufacture (section 12.8.2). In addition to minor speciality uses, some is used directly in gasoline, but most is dehydrated to isobutene for conversion into MTBE (methyl -butyl ether), a preferred octane improver in reformulated (lead-free) gasoline. 

Mono-alkyl ethers of ethylene glycol, ROCHjCHjOH. The mono methyl, ethyl and n-butyl ethers are inexpensive and are known as methyl cellosolve, cellosolve, and butyl cellosolve respectively. They are completely miscible with water, and are excellent solvents. The commercial products are purified by drying over anhydrous potassium carbonate or anhydrous calcium sulphate, followed by fractionation after... 

Compounds which dissolve in concentrated sulphuric acid may be further subdivided into those which are soluble in syrupy phosphoric acid (A) and those which are insoluble in this solvent (B) in general, dissolution takes place without the production of appreciable heat or colour. Those in class A include alcohols, esters, aldehydes, methyl ketones and cyclic ketones provided that they contain less than nine carbon atoms. The solubility limit is somewhat lower than this for ethers thus re-propyl ether dissolves in 85 per cent, phosphoric acid but re-butyl ether and anisole do not. Ethyl benzoate and ethyl malonate are insoluble. 

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). 

Methyl tert-Butyl Ether (MTBE). Methyl tert-hutyi ether [1634-04-4] is made by the etherification of isobutylane with methanol, and there are six commercially proven technologies available. These technologies have been developed by Arco, IFF, CDTECH, Phillips, Snamprogetti, and Hbls (hcensed jointly with UOP). The catalyst in all cases is an acidic ion-exchange resin. The United States has been showing considerable interest in this product. Western Europe has been manufacturing it since 1973 (ANIC in Italy and Huls in Germany). Production of MTBE in Western Europe exceeded 600,000 tons in 1990. 

Typical normal-phase operations involved combinations of alcohols and hexane or heptane. In many cases, the addition of small amounts (< 0.1 %) of acid and/or base is necessary to improve peak efficiency and selectivity. Usually, the concentration of polar solvents such as alcohol determines the retention and selectivity (Fig. 2-18). Since flow rate has no impact on selectivity (see Fig. 2-11), the most productive flow rate was determined to be 2 mL miiT. Ethanol normally gives the best efficiency and resolution with reasonable back-pressures. It has been reported that halogenated solvents have also been used successfully on these stationary phases as well as acetonitrile, dioxane and methyl tert-butyl ether, or combinations of the these. The optimization parameters under three different mobile phase modes on glycopeptide CSPs are summarized in Table 2-7. 

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