Ethers tert., etherification

Ether, tert-butyl phenyl, 41, 91 Etherification of cholestanol with diazomethane, 41, 9... 

Ethanol, 2-nitro-, 41, 67 conversion to nitroethylene, 41, 71 Ether, tert-butyl phenyl, 41, 91 Etherification of cholestanol, 41, 9 with diazomethane, 41, 9 3-Ethoxy-2-cyclohexenone, 40, 41 reduction to 2-cyclohexenone, 40, 14... 

After the above discussion on RD of ideal ternary mixtures, in this section two nonideal ternary systems are considered. These are the heterogeneously catalyzed syntheses of the fuel ethers MTBE (methyl tert-butyl ether) and TAME (fert-amyl methyl ether) by etherification of methanol with isobutene or isoamlyenes respectively. Both reaction systems have enormous industrial importance because of the outstanding antiknock properties of MTBE and TAME as gasoline components. 

Isomerization. Isomerization is a catalytic process which converts normal paraffins to isoparaffins. The feed is usually light virgin naphtha and the catalyst platinum on an alumina or zeoflte base. Octanes may be increased by over 30 numbers when normal pentane and normal hexane are isomerized. Another beneficial reaction that occurs is that any benzene in the feed is converted to cyclohexane. Although isomerization produces high quahty blendstocks, it is also used to produce feeds for alkylation and etherification processes. Normal butane, which is generally in excess in the refinery slate because of RVP concerns, can be isomerized and then converted to alkylate or to methyl tert-huty ether (MTBE) with a small increase in octane and a large decrease in RVP. 

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. 

Fig. 5.5.15 Spatially resolved 13C DEPT spectra recorded for the competitive etherification and hydration reactions of 2-methyl-2-butene (2M2B) to 2-methoxy-2-methylbutane (tert-amyl methyl ether, TAME) and 2-methyl-butan-2-ol (tert-amyl alcohol, TAOH), respectively. The molar composition of the feed was in the ratio 2 10 1 for 2M2B methanol water. The...

Disubstituted dihydrofurans and dihydropyrans were prepared via allylic etherification [68] in a similar manner to dihydropyrroles (cf Section 9.4.6). Thus, diaste-reoisomeric ethers were generated by the reaction of cinnamyl tert-butyl carbonate with the copper alkoxide prepared from (Rj-l-octen-3-ol, depending on which enantiomer of the phosphoramidite ligand was used (Scheme 9.39). Good yields and excellent selectivities were obtained. RCM in a standard manner gave cis- and trans-dihydrofuran derivatives in good yield, and the same method was used for the preparation of dihydropyrans. 

Originally it was believed that etherification with sulfuric acid proceeded through the intermediate formation of alkyl sulfuric acids (R0S03H), since these products sometimes could be isolated from the reaction mixture. It now seems clear, however, that alkyl sulfuric acids are formed only as by-products in the reaction and are not actually intermediates in the etherification process. Thus, ethyl ter -butyl ether was prepared in yields of 95 per cent by heating a mixture of tert-butyl and ethyl alcohols containing 15 per cent sulfuric acid at 70°, yet titration of the cooled reaction mixture showed no evidence of the formation of an alkyl sulfuric acid.4 Furthermore, the yield of diethyl ether was 95 per cent when ethanol was passed through concentrated sulfuric acid heated to 140°, but when the reaction was carried out with ethyl sulfuric acid at the same temperature, much sulfur dioxide was evolved and the yield dropped to 70 per cent.4 8 We can, therefore, conclude that the... 

Even though new MTBE plants are not being built in North America, CD is used currently for the production of other oxygenates such as TAME or ETBE, which being less soluble in water (i.e., less tendency to be transported in groundwater) are being considered or used as alternative octane enhancers. Ethyl-tert-butyl ether is produced from the etherification of ethanol and isobutylene while TAME production requires isoamylene and methanol. A simulation of the industrial production of a green octane enhancer from... 

Selectivity to ETBE is usually very high and the main side reactions are isobutene dimerization with formation of 2,4,4-trimethyl-l-pentene and 2,4,4-trimethyl-2-pentene (DIB), ethanol self-condensation to diethyl ether (DEE), water addition to isobutene with formation of tert-butyl alcohol (TBA) and the etherification of linear butenes, if present, to produce ethyl sec-butyl ether (ESBE). 

When zeolite MCM-22 is employed as catalyst for the reaction between substituted cyclohexanones and sec-alcohols, instead of the MPV reduction obtained with Beta, a novel reductive etherification occurs to give, for example, from 4-tcrt-butylcyclohexanone and i-PrOH the isopropyl ether of 4-tert-butylcyclohexa-nol with a cisitrans isomer ratio of 60 40 [34]. It is considered that in this reaction the higher Brpnsted-acid site population relative to MPV sites favors the formation of the ether via an intermediate hemiacetal. 

Application The Snamprogetti Etherification Technology allows producing high-octane oxygenates compounds such as methyl tert-butyl ether (MTBE), ethyl tert-butyl ether (ETBE), tert-amyl methyl ether (TAME), tert-amyl ethyl ether (TAEE) and etherified light cracked naphtha (ELCN). 

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. 

A third class of RD processes that are known to show intricate nonlinear behavior, are processes for the production of fuel ethers methyl tert-butyl ether (MTBE) and tert-amyl methyl ether (TAME). These are produced by etherification of iso-olefins with methanol according to... 

A somewhat different type of distillation with reaction is catalytic distillation fPoherty et al.. 2008 Parkinson. 200S1. In this process bales of catalyst are stacked in the column. The bales serve both as the catalyst and as the column packing (see Chapter 101. This process was used commercially for production of methyl tert-butyl ether (MTBE) from the liquid-phase reaction of isobutylene and methanol. The heat generated by the exothermic reaction is used to supply much of the heat required for the distillation. Since MTBE use as a gasoline additive has been oudawed because of pollution problems from leaky storage tanks, these units are shut down. Other applications of catalytic distillation include desulfurization of gasoline, separation of 2-butene from a mixed C4 stream, esterification of fatty acids and etherification. 

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