Chlorohydrin route

Due to the presence of a terminal double bond in 1-butene, oxidation of this isomer via a chlorohydrination route is similar to that used for propylene. 

Isobutylene oxide is produced in a way similar to propylene oxide and butylene oxide by a chlorohydrination route followed by reaction with Ca(OH)2. Direct catalytic liquid-phase oxidation using stoichiometric amounts of thallium acetate catalyst in aqueous acetic acid solution has been reported. An isobutylene oxide yield of 82% could be obtained. 

The classical chlorohydrin route has an atom efficiency of 25% and is better described as a calcium chloride process, with ethylene oxide as the major by-product. In other words, even if... 

The process was commercially so superior to the chlorohydrin route, that by the 1970s, the new chemistry had completely replaced the old. Adding some momentum to this transition was the fact that the obsolete and abandoned chlorohydrin plants could be readily converted to propylene oxide plants. The silver bullet for that process has yet to be found. 

You have to talk about propylene oxide and propylene glycol after ethylene oxide and glycol. Its not that the chemical configurations are so similar (they are), or that the process chemistry is about the same (it is). The Fact is that much of the propylene oxide is now made in plants originally designed and constructed to produce EO, not PO. As you read in the last chapter, the chlorohydrin route to EO was abandoned by the 1970s in favor of direct oxidation. At the same time, the EO producers found that the old EO plants were suitable for the production of PO and certainly the cheapest hardware available to satisfy growing PO demands. 

The chlorohydrin route takes two steps. The description.of them, unfortunately, is a sentence whose average word length is nine letters reaction of propylene with hypochlorous acid (HO-Cl) followed by dehydrochlorination of the propylene chlorohydrin with calcium hydroxide. Thats a tough way of... 

One ocher reaction noc shown is the formation of propylene dichloride. The demand for this compound is generally insufficient to absorb all the coproduction, so it also ends up on the list of things to be disposed of coming from the PO-chlorohydrin process, But despite this and all the ocher problems already mentioned about the chlorohydrin route, the process remains economically healthy—breathing heavily, but healthy. Indeed, 40 to 50% of the PO produced in the United States comes from this route. 

Z. Why is the chlorohydrin route losing favor as the preferred route to propylene oxide ... 

Another example of a famous organic chemical reaction being replaced by a catalytic process is furnished by the manufacture of ethylene oxide. For many years it was made by chlorohydrin formation followed by dehydrochlorination to the epoxide. Although the chlorohydrin route is still used to convert propylene to propylene oxide, a more efficient air epoxidation of ethylene is used and the chlorohydrin process for ethylene oxide manufacture has not been used since 1972. 

The direct oxidation of ethylene to EO by O2 has now replaced the chlorohydrin process entirely because it is cheaper and involves less byproducts, but propylene oxide (a monomer in polyurethanes) is still made by the chlorohydrin route. 

There are several alternatives to the polluting chlorohydrin route. One is the styrene monomer propene oxide (SMPO) process, used by Shell and Lyondell (Figure 1.6a) [14]. It is less polluting, but couples the epoxide production to that of styrene, a huge-volume product. Thus, this route depends heavily on the styrene market price. Another alternative, the ARCO/Oxirane process, uses a molybdenum... 

PO was manufactured by the chlorohydrin route first during World War I in Germany by BASF and others. This route (below) involves reaction of propylene with hypochlorous acid followed by treatment of the resulting propylene chlorohydrin with a base such as caustic or lime. The products of the second reaction are PO and sodium or calcium chloride (Fig. 10.22). 

To minimize hydrolysis of the propylene oxide (b.p. 34.2°C) as it is formed, it is flashed (rapidly removed) from the reactive lime slurry. Yields of propylene oxide are 75% or better based on propylene. The advantage of the chlorohydrin route to propylene oxide over the two hydroperoxidation processes is that it yields essentially a single product to market. The disadvantage is the large quantities of coproduced aqueous calcium chloride that has to be discarded safely. The small amount of by-product 1,2-dichloropropane may be pyrolyzed to allyl chloride, useful for the preparation of allyl monomers, allyl alcohol, and allylamines. Or it may be blended with 1,3-dichloropropene to produce an effective soil fumigant. 

Propylene oxide (PO) is an important chemical intermediate, which is mainly used in the manufacture of polyols, propylene glycols, and propylene glycol ethers [1]. The world annual production capacity of PO is about 7 million metric tons [2]. PO is mainly produced commercially by either the chlorohydrin (about 43%) or organic hydroperoxide processes. The chlorohydrin route produces large amounts of salt by-product, and new plants have used the hydroperoxide processes [3]. 

New routes to hydrogen peroxide new methods for direct synthesis of hydrogen peroxide (from hydrogen and oxygen) in a controlled, safe manner could provide a lower cost oxidant that reduces the use of chlorine. For example, in situ generation of hydrogen peroxide can be used to produce propylene oxide in place of the chlorohydrin route and... 

Synthesis of Oxirans by Halohydrin Cyclizations and Related Reactions. One of the oldest commercial methods for the production of ethene oxide is the chlorohydrin route, involving chlorohydration of ethene followed by dehydrochlorination. An improved procedure for the second stage of this process has been reported in which a basic ion-exchange resin is used to... 

Ethylene oxide was first synthesized by A. Wurtz in 1859 and the first industrial process based on chlorohydrin technology was commercialized in 1925 by the Union Carbide Corporation. In 1931, T. E. Letort carried out experiments on direct oxidation of ethylene to ethylene oxide and this technology was commercialized by Union Carbide in 1937. The direct oxidation process offered superior economics because it avoided the high cost of chemical feedstock in the form of chlorine and caustic required for the chlorohydrin route. For new plants, the air oxidation process became the preferred technology and by the early 1950s chlorohydrin was being phased out in favor of direct air oxidation [2]. 

The Chlorohydrin process involves the reaction of propylene with chlorine and water to produce propylene chlorohydrin. The propylene chlorohydrin is then dehydrochlorinated with lime or caustic to yield propylene oxide and a salt by-product. The chemistry is very similar to the chlorohydrin route from ethylene to ethylene oxide which was eventually replaced by the direct oxidation process. There are two major problems with the chlorohydrin route which provided the incentive for developing an improved process. There is a large water effluent stream containing about 5-6% calcium chloride or 5-10% sodium chloride (depending on whether lime or caustic is used for dehydrochlorination) and trace amounts of chlorinated hydrocarbon by-products that must be treated before disposal. Treatment of these by-products is expensive. The only practical way to handle it is to use caustic so that sodium chloride is produced and then integrate the effluent stream with a caustic-chlorine plant so that it can be recycled to the caustic plant. This, however, is also expensive because recovery of sodium chloride from this relatively dilute stream has a high energy cost. 

The most important example of this reaction is the formation of ethylene oxide (Eqn. 1), over Ag-catalysts which displaced the two-step chlorohydrine route (Eqn. 2). Ethylene oxide is used in the production of ethylene glycol, antifreeze, polyesters and surfactants, and accounts for 18% of U.S. ethylene consumption (Figure 3). ... 

Explain the atom efficiency concept by comparing the classical chlorohydrin route and the newer petrochemical ethylene oxide manufacture. 

Until about 1970, the chlorohydrin route to propylene oxide predominated worldwide. 

In the chlorohydrin route, generally preferred in the epoxidation of C3-C4 olefins, stoichiometric amounts of sodium or calcium chlorides are produced by the dehydrohalogenation of intermediate halohydrins. Chlorinated organic by-products, such as halogen ethers and dichlorides, are formed as well in the process, fur er increasing the quantity of wastes. 

Modern propylene oxide plants in which the chlorohydrin route is followed have reached a close integration of the chlorine cycle with a conventional chlor-alkali plant. 

Since the introduction of the direct ethene oxidation process, the chlorohydrin route lost its commercial significance. 

There are two major processes used to produce propylene oxide the chlorohydrin process and peroxidation of propylene. More than half of world production is by the chlorohydrin route. In this process, the first step is reaction of propylene with hypochlorous acid to obtain propylene chlorohydrin. 

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