Methanol MTBE from

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. 

United States, methanol derived from natural gas as a fuel additive is a promising future market. Methanol has neither the environmental problems of methyl-t-butyl ether (MTBE), nor the evaporating qualities of ethanol. 

Clay-supported heteropoly acids such as H3PW12O40 are more active and selective heterogeneous catalysts for the synthesis of MTBE from methanol and tert-butanol, etherification of phenethyl alcohols with alkanols, and alkylation of hydroquinone with MTBE and tert-butanoi (Yadav and Kirthivasan, 1995 Yadav and Bokade, 1996 Yadav and Doshi, 2000), and synthesis of bisphenol-A (Yadav and Kirthivasan, 1997). 

The next 10 chapters cover a collection of petrochemicals not altogether related to each other. Synthesis gas is a basic building block that leads to the manufacture of ammonia and methanol. MTBE is made from methanol from synthesis gas (with a little isobutylene thrown in). The alcohols in Chapter 14 and 15, the aldehydes in 16, the ketones in 17, and the acids in 18 are all closely related to each other by looks, though the routes to get to them are perplexingly different. Alpha olefins and the plasticizer and detergent alcohols have the same roots and routes, but different ones from the rest. Maleic anhydride, acrylonitrile, and the acrylates— well, they re all used to make polymers and they had to be somewhere. 

The acidity of a clay can be either of the Brpnsted (H+ donor) or Lewis (electron pair acceptor) type. Even at temperatures below 100 °C, tertiary carbocation intermediates can be generated on clays with high Brpnsted acidity through protonation of the C=C double bond in secondary alkenes, as in the clay-catalyzed formation of MTBE from methanol and isobutene ... 

MTBE is used on a large scale as an octane number boosting additive in unleaded gasoline. Sulfonic acid resins are applied as efficient catalysts for the industrial production of MTBE from methanol and isobutylene (222). Since 1987, investigations of the synthesis of MTBE with reactants in the gas phase have been performed with zeolites HY (223-225), H-Beta (226), HZSM-5 (224,225), and H-BZSM-5 (227) as catalysts. 

Further improvements in alkylation can be achieved when an MTBE unit (acid-catalyzed addition of methanol to isobutylene to form tert-butyl methyl ether) is added before the alkylation unit.299 The MTBE unit removes the lowest-octane-producing isomer, isobutylene, from the C4 stream (and produces a very-high-octane number component, MTBE). The H2S04 alkylation unit then can be operated under better conditions to produce an alkylate with a somewhat increased octane number (0.75-1). Higher acid consumption, however, may be experienced as a result of methanol, MTBE and dimethyl ether impurities in the olefin feed. The combination of MTBE with HF alkylation offers no apparent advantages. 

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). 

M.S.K. Chen, G.S. Markiewicz and K.G. Venugopal, Development of Membrane Pervaporation TRIM Process for Methanol Recovery from CH3OII/MTBE/C4 Mixtures, in Membrane Separations in Chemical Engineering, AIChE Symposium Series Number 272, A.E. Fouda, J.D. Hazlett, T. Matsuura and J. Johnson (eds), AIChE, New York, NY, p. 85 (1989). 

Figure 1 Examples of industrial processes employing reactive distillation (a) methyl ferf-butyl ether (MTBE) from isobutene and methanol (b) cumene via alkylation of benzene with propylene (c) ethylene glycol via hydration of ethylene oxide.

Show all of the steps in the mechanism for the formation of MTBE from methanol and isobutylene. 

Diphenyl carbonate from dimethyl carbonate and phenol Dibutyl phthalate from butanol and phthalic acid Ethyl acetate from ethanol and butyl acetate Recovery of acetic acid and methanol from methyl acetate by-product of vinyl acetate production Nylon 6,6 prepolymer from adipic acid and hexamethylenediamine MTBE from isobutene and methanol TAME from pentenes and methanol Separation of close boiling 3- and 4-picoline by complexation with organic acids Separation of close-boiling meta and para xylenes by formation of tert-butyl meta-xyxlene Cumene from propylene and benzene General process for the alkylation of aromatics with olefins Production of specific higher and lower alkenes from butenes... 

Ether synthesis produces branched ethers like methyl t-butyl ether (MTBE) by reacting methanol (or ethanol) with branched alkenes such as isobutene. These ethers are valuable for their high octane quality and also, on account of the oxygen they contain, their ability to reduce both CO and hydrocarbon exhaust emissions. Alcohols, such as methanol, manufactured from natural gas or coal, and ethanol, produced by fermentation, are other oxygenated components in limited use. 

Methanol removal from mixtures with toluene, MTBE, IPA, and acetonitrile... 

Iso-butane is a highly demanded chemical in the refinery industry for the production of alkylates (by alkylation with butenes), and methyl tert-butyl ether (MTBE) (from isobutene and methanol), both important additives for reformulated gasolines. n-Butane isomerization is performed over platinum supported on chlorinated alumina. The chlorine compound which is continuously supplied to the feed in order to maintain the activity [1] is harmful to the environment. 

The reaction of mono- and poly-alcohols catalyzed by solid acids has been widely investigated. An important application is the synthesis of five membered cyclic ethers starting from di- or triols. Several authors described such cyclisation reactions, starting from 1,2,4-butanetriol (clay) [1], 1,2,5-pentatriol (pentasile, mordenite, erionite) [2]. Linear ethers like dimethyl ether are formed from methanol (modified aluminosilicate, zeolites) [3,4] or MTBE from methanol and i-butene (zeolite, resin) [5,6] The yields of the desired products are often quite high, e g over 90 % in the case of 1,2,4-butanetriol to 3-hydroxy-tetrahydrofiiran and about 60 % in the case of dimethyl ether. The reactions are either carried out in the presence of water as slurry process [1,2] at 150 - 200 °C or at temperatures > 300 °C in the gas phase with a fixed bed catalyst [2-4]... 

Higher levels of conversions (> 99%) can be achieved by a two-stage MTBE synthesis process (Figure 3.26). The first reactor is a typical MTBE synthesis, using isobutene and methanol as feeds over a packed-bed ion-exchange reactor. The product is separated in a debutanizer tower and the overhead of this reactor is charged to another synthesis reactor to achieve higher conversion of isobutene. A secondary debutanizer is used to separate the additional MTBE produced in the secondary packed bed reactor. Methanol removed from the overhead stream is recycled back to the primary synthesis reactor [52]. 

CDTech uses catalytic distillation to convert isobutene and methanol to MTBE, where the simultaneous reaction and fractionation of MTBE reactants and products takes place [51], A block diagram of this process is shown in Figure 3.31. The C4 feed from catalytic crackers undergoes fractionation to extract deleterious nitrogen compounds. It is then mixed with methanol in a BP reactor where 90% of the equilibrium reaction takes place. The reactor effluent is fed to the catalytic distillation (CD) tower where an overall isobutene conversion of 97% is achieved. The catalyst used is a conventional ion-exchange resin. This process selectively removes MTBE from the product to overcome the chemical equilibrium limitation of the reversible reaction. The MTBE product stream is further fiactionated to remove pentanes, which are sent to gasoline blending, whereas the raffinate from the catalytic distillation tower is washed with water and then fractionated to recover the methanol. 

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],... 

Matouq et al [3.31] tested two types of catalysts an ion exchange-resin (the form of Amberlyst 15) and a heteropolyacid (HPA) in the production of MTBE from methanol and -butyl alcohol (TBA). Both were shown, active, but the ion-exchange resin showed poor selectivity, producing substantial amounts of by-product isobutylene (IB). Matouq et al. [3.31] tested the production of MTBE using the ion-exchange resin in a reactive distillation column. It was difficult to test the HPA catalyst in the reactive distillation system, however, because its particle size was too small and was carried out by the liquid phase. Matouq et al. [3.31] proposed, instead, the use of a PVMR incorporating a PVA membrane. As shown in Figure 3.9, in the proposed system the PVMR is coupled with a con-... 

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 ... 

Today methanol has become a very important feedstock for the production of many chemicals. Use as a clean fuel has increased and methanol is used in the production of the popular oxygenated fuel additive, MTBE. It has also been postulated that methanol could be a carrier of energy for safe transportation between remote countries. Furthermore, to prevent a greenhouse effect caused by COj generated from the tremendous oxidation reactions on the earth, methanol synthesis from CO2 is regarded as one of the potential solutions to decrease CO2 by the reaction with hydrogen which is produced by electrolysis of water, for example. Due to the increasing demand for methanol, many researchers are involved in the development of more active methanol synthesis catalysts. 

Finally, we comment from a wider perspective on the energy efficiency of producing MTBE. In the route of producing MTBE from field butanes and methanol, a typical figure... 

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