Methyl-tert-butyl ether synthesis

Over the last decade reactive distillation (RD) has become a key technology for meeting increased productivity demands. The best-known example in C4 chemistry is given by MTBE (methyl tert butyl ether) synthesis. Both the CD Tech process and the Ethermax process by UOP consist of fixed-bed reactors followed by an RD col-... 

Jacobs R. and Krishna R. (1993). Multiple solutions in reactive distillation for methyl tert-butyl ether synthesis. Industrial and Engineering Chemistry Research 32 (8), 1706-1709. 2.1, 2.9, 2.9.1.1,... 

Zhang T. and Datta R. (1995). Integral analysis of methyl tert-butyl ether synthesis kinetics. Industrial and Engineering Chemistry Research 34 (3), 730-740. 5.5.1, B.4... 

Mixed C4 olefins (primarily iC4) are isolated from a mixed C olefin and paraffin stream. Two different liquid adsorption high-purity C olefin processes exist the C4 Olex process for producing isobutylene (iCf ) and the Sorbutene process for producing butene-1. Isobutylene has been used in alcohol synthesis and the production of methyl tert-butyl ether (MTBE) and isooctane, both of which improve octane of gasoHne. Commercial 1-butene is used in the manufacture of both hnear low-density polyethylene (LLDPE) and high-density polyethylene (HDPE)., polypropylene, polybutene, butylene oxide and the C4 solvents secondary butyl alcohol (SBA) and methyl ethyl ketone (MEK). While the C4 Olex process has been commercially demonstrated, the Sorbutene process has only been demonstrated on a pilot scale. 

Hydroxynitrile lyase Synthesis of (R)-mandelonitrile in sodium phosphate buffer/methyl tert-butyl ether [70]... 

Activity of Heteropolyacid in Synthesis of Methyl tert-Butyl Ether" (179)... 

In many olefmic reactions activation of the C=C double bond occurs, although in many reactions at least one C-H bond is transformed. Established processes are summarized in Table 3. Examples of liquid-phase reactions are the synthesis of ethers, especially methyl tert-butyl ether by reacting olefins (isobutene) and alcohol (methanol) in the liquid phase at slightly elevated temperature and pressure (Table 3, entry 22). Different processes developed differ only slightly in feed composition and design, which is optimized for heat removal [2]. 

The apparent activation energy for the synthesis reaction of methyl tert-butyl ether or MTBE, was found to be 64 KJ/mole. The best activity and selectivity for MTBE were observed at temperatures of 85 - 90 °C, and contact times of circa 2.5 h when the methanol / isobutene molar ratio was kept within the 1.2 - 1.5 range. There was a fierce competition between the ethyl tert-butyl ether formation and that of diethylether at reaction temperatures higher than 85 °C. 

Shikata S., Okuhara T. and Misono M., Gas phase synthesis of methyl tert-butyl ether over heteropolyacids. J. Mol. Catal. 100 (1995) pp. 49-59. 

The hydrogenation of carbon dioxide was studied using composite catalysts comprised of Fe-Zn-M (M= Cr, Al, Ga, Zr) catalysts and the HY zeolite, where the methanol synthesis and the methanol-to-gasoline(MTG) reaction are combined. The results show that light olefins are important intermediates for iso-butane formation. In all of the cases, the selectivity of isobutane, which can be used as a reactant in subsequent methyl-tert-butyl ether (MTBE) synthesis, was the highest in hydrocarbons. 

By tailoring the reaction conditions, alkenes may be cleaved oxidatively to yield aldehydes and carboxylic acids [10f]. The presence of a Brpnsted acid, e. g., HBF4 or HCIO4, required to accelerate the oxidation of the olefin with respect to the deactivation of the catalyst, results in the synthesis of the aldehyde without overoxidation to the acid. Significant quantities of the diol are also present, however. A three-fold excess of H2O2 is required to oxidize the alkene to the acid. However, this also results in the simultaneous oxidation of the methyl tert-butyl ether solvent to the peroxide. 

Today, synthesis gas is mainly used for the production of ammonia (120 x 10 t/yr ) and methanol (30 X 10 t/yr ) followed by pure hydrogen for hydro-treating in refineries. Other current applications are in the production of higher alcohols by hydroformulation and a number of products including acetic acid, formaldehyde, dimethyl ether (DME), and methyl-tert-butyl ether (MTBE) in all cases methanol is used as a coreactant. 

Processes based on these catalysts could provide isobutene and isopentene for the synthesis of MTBE (methyl tert-butyl ether) and TAME (tert-amyl methyl... 

Most industrial processes of this kind use strong-acid ion exchangers for reactions catalyzed by hydrogen ions. A large-scale example is the synthesis of methyl tert. -butyl ether (MTBE) from methanol and isobutene as anti-knock gasoline additive [34,35],... 

Another form of nonuniform deactivation can occur if catalyst sites differ in their activity and their adsorption affinity or chemical sensitivity. Usually, the most active sites are also the most susceptible to deactivation. If so, the activity of a fresh catalyst declines steeply at first and then at a steady, slower pace. This is believed to happen in some petroleum refining operations. Another example is loss of sulfonic acid groups in synthesis of methyl tert. -butyl ether catalyzed by ion exchangers. In this application, the acid shed by the catalyst causes corrosion problems, and catalysts are therefore "aged" under reaction conditions to eliminate the most labile acid groups before being charged to the reactors. 

The light alkenes (propene, butene and pentene) are important feedstocks for alkylation, oligomerization and the synthesis of ethers (refs. 1,2). MTBE (methyl tert-butyl ether) and TAME (tert-amyl methyl ether) have research octane numbers of 118 and 112 respectively. These premium blend stocks are synthesised by reaction of methanol with isobutene or isopentene (refs. 3,4). The reaction with methanol is selective towards the branched alkenes so that a mixture may be treated and the straight chain alkenes recovered for other processing such as alkylation. 

Finally, integrating chemical reaction and separation in a single vessel offers opportunities for waste reduction. As an example of this strategy, consider the synthesis of methyl-tert-butyl ether (MTBE). Two processes are in common industrial use in the synthesis of MTBE from methanol and isobutylene. In one process, a series of fixed-bed catalytic reactors send a mix of product, unreacted methanol, and unreacted isobutylene to a series of separation devices. In an alternative process configuration, the feed materials are sent to a distillation column that contains a series of catalytic beds. The processes are contrasted in Fig. 17. There are several advantages to the catalytic distillation configuration ... 

Mukai and co-workers [105] used Keggin-type heteropolyacids immobilized in the network structure of resorcinol-formaldehyde carbon gels as catalysts for the synthesis of methyl tert-butyl ether from methyl alcohol and tert-butyl alcohol. Large amounts of 12-tungstophosphoric and 12-molybdophosphoric acids were immobilized into the support by two methods, pore shrinkage and the ship-in-the-bottle method, which are essentially impregnation methods. The authors reported that these catalysts showed activity in the reaction studied and could be of practical utility as solid acid catalysts in various reactions. 

OTHER COMMENTS used as a gasoline additive to prevent knocking in motors (has been largely replaced by methyl-tert-butyl ether) used in the synthesis of ethylmercury compounds used as a chemical intermediate for mixed alkyl leads. 

A further process for which reactive distillation is commonly used in industrial practice is the synthesis of methyl-tert-butyl ether (MTBE) which is an additive for gasoline. MTBE is produced by etherification ofisobutene with methanol. The process based on reactive distillation leads to conversions of 99%. Isobutene and methanol are fed into the pre-reactor where the equilibrium conversion is obtained. The stream leaving the pre-reactor is fed into the reactive distillation column where MTBE is obtained as the bottom product. 

Nair and co-workers [8] have coupled of semi-continuous NF with the Heck reaction. The objective was the synthesis of trans-stilbene from styrene and iodobenzene using Pd(OAc)2(PPh3)2 as catalyst and Pjo-tolyljj as stabilizing agent. They used solvent-resistant membranes and different aqueous/solvent systems (ethyl acetate and acetone/H20 methyl tert-butyl ether and acetone/H20 tetra-hydrofuran/H20). The best conversion was obtained with the first-mentioned solvent mixture. A selectivity of 100% of trans-stilbene with a cumulative turnover number of 1200 was reported, where the rejection of the catalyst turned out to be as high as 97%. Therefore, the authors concluded that NF was a convenient technique to run catalytic reactions with catalyst recycling, since this method saves the catalyst, prevents the metal contamination of the products, and increases reactor productivity. 

Olah et al. reported the triflic acid-catalyzed isobutene-iso-butylene alkylation, modified with trifluoroacetic acid (TFA) or water. They found that the best alkylation conditions were at an acid strength of about//q = —10.7, giving a calculated research octane number (RON) of 89.1 (TfOH/TFA) and91.3 (TfOH/HaO). Triflic acid-modified zeohtes can be used for the gas phase synthesis of methyl tert-butyl ether (MTBE), and the mechanism of activity enhancement by triflic acid modification appears to be related to the formation of extra-lattice Al rather than the direct presence of triflic acid. A thermally stable solid catalyst prepared from amorphous silica gel and triflic acid has also been reported. The obtained material was found to be an active catalyst in the alkylation of isobutylene with n-butenes to yield high-octane gasoline components. A similar study has been carried out with triflic acid-functionalized mesoporous Zr-TMS catalysts. Triflic acid-catalyzed carbonylation, direct coupling reactions, and formylation of toluene have also been reported. Tritlic acid also promotes transalkylation and adaman-tylation of arenes in ionic liquids. Triflic acid-mediated reactions of methylenecyclopropanes with nitriles have also been investigated to provide [3 + 2] cycloaddition products as well as Ritter products. Tritlic acid also catalyzes cyclization of unsaturated alcohols to cyclic ethers. ... 

Colombo F., Cori L., Dalioro L. and Delogu P. (1983). Equilibrium constant for the methyl tert-butyl ether liquid phase synthesis by use of UNIFAC. Industrial Engineering Chemistry Fundamentals 22 (2), 219-223. B.4, B.5... 

Izquierdo J., Cunill F., Vila M., Tejero J. and Iborra M. (1992). Ekjuilibrium constants for methyl tert-butyl ether liquid-phase synthesis. Journal of Chemical and Engineering Data 37, 339-343. B.4, B.5, B.6... 

Izquierdo, J.F., Cunnill, F., Vila, M.. Tejero, J., and Iborra, M. (1992) Equilibrium Constants for Methyl tert-Butyl Ether Liquid-Phase Synthesis. J. Chem. Eng. Data, 37, 339-343. 

---