Hydration and etherification

The use of RD in the manufacture of other ethers such as ETBE, TAME, and so on, has been demonstrated to be beneficial and several patents and investigations have emerged [3, 4]. UOP describes a process for the manufacture of DIPE (di-isopropyl ether), which uses propylene and water feedstock. It is a two-stage RD process associated with simultaneous hydration and etherification [5]. The ethers, being the heaviest components, are collected in the bottom stream. 

For the reasons outlined above, some typical acid-catalysed reactions, such as hydration and etherification, may be better performed over non-microporous acid catalysts, but microporous acids have found uses in this area. Asahi, for example, have established the zeolite-catalysed hydration of cyclohexene as a commercial process, " where in a two-phase reaction mixture (aqueous and non-aqueous layers) the H-ZSM-5 catalyst stays in the aqueous phase but adsorbs enough cyclohexene, because of its relative hydrophobicity, that the reaction proceeds in the zeolite pores. This has the advantage over the previously used cyclohexene/sulfuric acid system that the aqueous layer is not acidic and corrosive. Furthermore, the medium-pore structure impedes etherification to dicyclohexyl ether and the highly siliceous zeolite has long-term stability in boiling water. 

Hydration and etherification. The direct hydration of ethylene has been discussed (section 11.5). Propylene can also be hydrated in the gas phase over supported phosphoric acid (c. 180°C), or with an ion-exchange resin catalyst at about 140°C, with liquid water and gaseous propylene. The use of an ion-exchange resin as a catalyst has also been commercialized for the hydration of n-butenes, though the sulphuric acid two-stage process still predominates. The use of very weak acid systems at much higher temperatures (> 250 "C) has also been studied. 

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...

Fig. 15 Spatially resolved 13C DEPT-MRI spectra recorded for the competitive etherification and hydration reactions of 2M2B to TAME and TAOH, respectively. Spectra recorded at 6 positions along the length of the bed are shown, at 2.5 mm intervals. The entrance to the bed is at 0 mm. 

C-M bond addition, for C-C bond formation, 10, 403-491 iridium additions, 10, 456 nickel additions, 10, 463 niobium additions, 10, 427 osmium additions, 10, 445 palladium additions, 10, 468 rhodium additions, 10, 455 ruthenium additions, 10, 444 Sc and Y additions, 10, 405 tantalum additions, 10, 429 titanium additions, 10, 421 vanadium additions, 10, 426 zirconium additions, 10, 424 Carbon-oxygen bond formation via alkyne hydration, 10, 678 for aryl and alkenyl ethers, 10, 650 via cobalt-mediated propargylic etherification, 10, 665 Cu-mediated, with borons, 9, 219 cycloetherification, 10, 673 etherification, 10, 669, 10, 685 via hydro- and alkylative alkoxylation, 10, 683 via inter- andd intramolecular hydroalkoxylation, 10, 672 via metal vinylidenes, 10, 676 via SnI and S Z processes, 10, 684 via transition metal rc-arene complexes, 10, 685 via transition metal-mediated etherification, overview,... 

The pioneer work in this field was carried out on polystyrene-supported acid catalysts [161]. Thereafter, several works on the use of sulfonic, strong acidic cation exchangers as acid catalysts were reported for alkylation, hydration, etherification, esterification, cleavage of ether bonds, dehydration, and aldol condensation [162,168-171], Besides, industrial applications of these materials were evaluated with reactions related to the chemistry of alkenes, that is, alkylation, isomerization, oligomerization, and acylation. [163,169], Also, Nation, an acid resin which has an acid strength equivalent to concentrated sulfuric acid, can be applied as an acid catalyst. It is used for the alkylation of aromatics with olefins in the liquid or gas phases and other reactions however, due to its low surface area, the Nation resin has relatively low catalytic activity in gas-phase reactions or liquid-phase processes where a nonpolar reactant or solvent is employed [166],... 

The first commercial and most well-known application of CD was in the production of MTBE. Besides etherification for the production of MTBE, CD could be applied in a number of processes such as alkylation, hydrogenation, isomerization, esterification, desulfurization, aldol condensation, oligomerization, hydration, hydrolysis, amination, and halogenation. Catalytic Distillation Technology (CDTECH), a partnership between ABB Lummus Global and Chemical Research and Licensing, is the leader in the development and commercialization of CD processes particularly related to the refining, petrochemical, and chemical industries. However, there are many more potential applications of CD that could be developed. 

Etherification of propylene and isopropyl alcohol to produce diisopropyl ether, an octane enhancer, has been patented as a two-stage process.The first step involves the hydration of propylene to isopropyl alcohol using acidic ion-exchange resins or acidic zeolites and an optional cosolvent and the second step involves the etherification of propylene and isopropyl alcohol using an acidic catalyst such as Amberlyst 36 in a CD column. 

Many industrial processes are based on acid/base catalysis (over 130). Examples include alkylation, etherification, cracking, dehydration, condensation, hydration, oligomerizations, esterification, isomerization and disproportionation. The dimensions of the processes range from very large scale in the field of refinery (thousand tons per day) to very small productions in fine and specialty chemical industries. In the latter case, adds and bases are often used in stoichiometric quantities, leading thus to large amounts of waste. 

---