Industrial epoxides

Titanium Alkoxides Silica-supported titanium(IV) alkoxides and Ti-silicalite are industrial epoxidation catalysts [53-56] and have been applied in deperoxidation reactions [57]. Computational and EXAFS data [53, 54] as well as spectroscopic investigations on the surface species [58] have indicated that the dominant active surface species is a four-coordinate trisUoxy complex [(=SiO)3TiOH] [59] whose coordination shell expands to six-coordinate during catalysis [60]. 

Active O stoichiometry G(T,P) analysis. Figure 14 plots the free energy of adsorption as a function of temperature for the most stable Ag oxide overlayer at each O coverage.14 The pressure is 15 atmospheres, which is characteristic of the pressure used in industrial epoxidation catalysis [10]. We find that at zero Kelvin the most stable overlayer is the Agt 22O overlayer, i.e. the Ag oxide with an additional O adatom inside each oxide ring... 

Unsaturated fatty compounds are the preferred educts in industrial epoxidation. Numerous methods are available to transform then to the corresponding epoxides. Epoxidation with molecular oxygen [3], dioxiranes [4], hydrogen peroxide with methyltrioxorhenium as catalyst [5, 6], the Halcon process [7], or enzymatic reactions [8] are the most important industrial processes (cf. Section 2.4.3). 

Several modifications of either the catalyst formulation or the process conditions were then reported, with remarkable improvements in performance being recorded. However, in all cases gas-phase promoters, be they organic halides or NOx, were necessary to have acceptable conversion and relatively stable performance. Carbon dioxide is also a promoter, since in the presence of CO2 the selectivity was improved, but the conversion considerably decreased. These features are clearly analogous to those applied in the industrial epoxidation of ethene. 

Despite the above drawbacks, metal-peroxo chemistry will have an increasing contribution to clean industrial epoxidations. One of the current technologies used for propylene oxide and epichlorhydrin is the chlorhydrin route, where olefin is reacted with hypochlorous acid (from chlorine) followed by ring-closure of the chlorhydrin with lime ... 

Ethylene oxide and propylene oxide are by far the most important industrial epoxides. The production of these two compounds has been selected as a process example in this textbook and is described in detail in Section 6.12. Table 5.3.5 summarizes the most relevant applications of these important intermediates and gives the actual production capacities. 

Peroxyacetic acid in acetic acid is used in industrial epoxidation reactions. Peroxyacetic acid is produced from the reaction of hydrogen peroxide with acetic acid. 

Bromine is used in the manufacture of many important organic compounds including 1,2-dibromoethane (ethylene dibromide), added to petrol to prevent lead deposition which occurs by decomposition of the anti-knock —lead tetraethyl bromomethane (methyl bromide), a fumigating agent, and several compounds used to reduce flammability of polyester plastics and epoxide resins. Silver(I) bromide is used extensively in the photographic industry... 

Epichlorohydnn is the common name of an industrial chemical used as a component in epoxy cement The molecular formula of epichlorohydnn is C3H5CIO Epichlorohydnn has an epoxide functional group it does not have a methyl group Write a structural formula for epichloro hydrin... 

Three membered rings that contain oxygen are called epoxides At one time epox ides were named as oxides of alkenes Ethylene oxide and propylene oxide for exam pie are the common names of two industrially important epoxides... 

Ethylene glycol and propy lene glycol are prepared industrially from the corre spending alkenes by way of their epoxides Someapplica tions were given in the box in Section 6 21... 

Glycols and epoxides react with maleic anhydride to give linear unsaturated polyesters (61,62). Ethylene glycol and maleic anhydride combine to form the following repeating unit. This reaction is the first step in industrially important polyester resin production (see Polyesters, unsaturated). 

The main industrial uses of petoxycatboxyhc acids ate in the manufacture of epoxides, synthetic glycerol (qv), and epoxy resins (qv) (165,167,168). They also have been used as disinfectants (177), fungicides, and bleaching agents and for shrink-proofing wool (34). 

Propylene oxide and other epoxides undergo homopolymerization to form polyethers. In industry the polymerization is started with multihinctional compounds to give a polyether stmcture having hydroxyl end groups. The hydroxyl end groups are utilized in a polyurethane forming reaction. This article is mainly concerned with propylene oxide (PO) and its various homopolymers that are used in the urethane industry. 

The majority of 2-methylphenol is used in the production of novolak phenoHc resins. High purity novolaks based on 2-methylphenol are used in photoresist appHcations (37). Novolaks based on 2-methylphenol are also epoxidized with epichlorohydrin, yielding epoxy resins after dehydrohalogenation, which are used as encapsulating resins in the electronics industry. Other uses of 2-methylphenol include its conversion to a dinitro compound, 4,6-dinitro-2-methylphenol [534-52-1] (DNOC), which is used as a herbicide (38). DNOC is also used to a limited extent as a polymerization inhibitor in the production of styrene, but this use is expected to decline because of concerns about the toxicity of the dinitro derivative. 

Dichlorides and e2thers are the main by-products in this reaction. Treatment with base produces propylene oxide. Specialty epoxides, eg, butylene oxide, are also produced on an industrial scale by means of HOCl generated from calcium hypochlorite and acetic acid followed by dehydrohalogenation with base. 

Dehydrochlorination to Epoxides. The most useful chemical reaction of chlorohydrins is dehydrochlotination to form epoxides (oxkanes). This reaction was first described by Wurtz in 1859 (12) in which ethylene chlorohydria and propylene chlorohydria were treated with aqueous potassium hydroxide [1310-58-3] to form ethylene oxide and propylene oxide, respectively. For many years both of these epoxides were produced industrially by the dehydrochlotination reaction. In the past 40 years, the ethylene oxide process based on chlorohydria has been replaced by the dkect oxidation of ethylene over silver catalysts. However, such epoxides as propylene oxide (qv) and epichl orohydrin are stiU manufactured by processes that involve chlorohydria intermediates. 

Recently (79MI50500) Sharpless and coworkers have shown that r-butyl hydroperoxide (TBHP) epoxidations, catalyzed by molybdenum or vanadium compounds, offer advantages over peroxy acids with regard to safety, cost and, sometimes, selectivity, e.g. Scheme 73, although this is not always the case (Scheme 74). The oxidation of propene by 1-phenylethyl hydroperoxide is an important industrial route to methyloxirane (propylene oxide) (79MI5501). 

The manufacture and uses of oxiranes are reviewed in (B-80MI50500, B-80MI50501). The industrially most important oxiranes are oxirane itself (ethylene oxide), which is made by catalyzed air-oxidation of ethylene (cf. Section 5.05.4.2.2(f)), and methyloxirane (propylene oxide), which is made by /3-elimination of hydrogen chloride from propene-derived 1-chloro-2-propanol (cf. Section 5.05.4.2.1) and by epoxidation of propene with 1-phenylethyl hydroperoxide cf. Section 5.05.4.2.2(f)) (79MI50501). 

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