Chlorohydrin process/route

Ethylene oxide has been produced commercially by two basic routes the ethylene chlorohydrin and direct oxidation processes. The chlorohydrin process was first iatroduced dufing World War I ia Germany by Badische Anilin-und Soda-Eabfik (BASE) and others (95). The process iavolves the reaction of ethylene with hypochlorous acid followed by dehydrochlofination of the resulting chlorohydrin with lime to produce ethylene oxide and calcium chloride. Union Carbide Corp. was the first to commercialize this process ia the United States ia 1925. The chlorohydrin process is not economically competitive, and was quickly replaced by the direct oxidation process as the dominant technology. At the present time, all the ethylene oxide production ia the world is achieved by the direct oxidation process. 

The disadvantage of the chlorohydrin process is the use of toxic, corrosive, and expensive chlorine the major drawback of the peroxide process is the formation of co-oxidates in larger amounts than the desired PO. The direct epoxidation of propylene using 02 (i.e., partial oxidation of propylene) from air has been recognized as a promising route. 

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. 

Early routes to AA were complex and expensive. In 1927 the ethylene chlorohydrin process was introduced, but it was also still expensive, and not much commercial interest was stimulated in AA. In 1940 a process came literally right off the farm—pyrolysis of lactic acid, a waste product of the dairy industry found in sour milk. 

The epoxidation of propylene to propylene oxide is a high-volume process, using about 10% of the propylene produced in the world via one of two processes [127]. The oldest technology is called the chlorohydrin process and uses propylene, chlorine and water as its feedstocks. Due to the environmental costs of chlorine and the development of the more-efficient direct epoxidation over Ti02/Si02 catalysts, new plants all use the hydroperoxide route. The disadvantage here is the co-production of stoichiometric amounts of styrene or butyl alcohol, which means that the process economics are dependent on finding markets not only for the product of interest, but also for the co-product The hydroperoxide route has been practiced commercially since 1979 to co-produce propylene oxide and styrene [128], so when TS-1 was developed, epoxidation was looked at extensively [129]. 

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. 

Chlorine is principally used to produce organic compounds. But, in many cases chlorine is used as a route to a final product that contains no chlorine. For instance propylene oxide has traditionally been manufactured by the chlorohydrin process. Modern technology permits abandoning this route in favor of direct oxidation, thus eliminating a need for chlorine. 

Two process routes to propylene oxide are commercially practiced hydroperoxide formation and then use of this to oxidize propylene, and formation of propylene chlorohydrin followed by treatment with a base to form propylene oxide [22, 23]. It has not been possible to produce adequate yields of propylene oxide via the direct oxidation of propylene with air in the manner in which ethylene oxide is now produced, although attempts to come close to this continue [24]. 

Improvements in the direct-oxidation route to ethylene oxide, contributing to reduced costs, have resulted in increased manufacturing capacity which now surpasses the chlorohydrin process capacity. By the direct-oxidation route, catalysts costs have been reported to be in the range 0.38-0.40 cents per pound ethylene oxide. Fixed-bed catalyst plants have been stated to attain yields of 55-65 per cent in commercial practice. Investment costs for large-scale direct-oxidation ethylene oxide plants have been reported to be 10-11 cents per annual pound of capacity. ... 

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. 

Two processes are currently used for the production of propylene oxide. About 50% is produced by the chlorohydrin process and the other 50% by the peroxidation process. The chlorohydrin process is the older technology and it is slowly being replaced by the more economical and environmentally acceptable peroxidation route. There are environmental issues associated with the large aqueous by-product stream of calcium chloride and chlorinated hydrocarbon by-products from the chlorohydrin process. The only producers that will continue to operate chlorohydrin plants are highly integrated caustic-chlorine producers who have chlorine production facilities which can handle the calcium chloride by-product and chlorinated hydrocarbons [9]. 

The majority of propylene oxide is produced in the chlorohydrin process (CHPO), or co-product routes Baer, H., Bergamo, M., Forlin, A., Pottenger, L.H., and Lindner, J. (2012) Propylene oxide, in UUmann s Encyclopedia of Industrial Chemistry, Wiley-VCH Verlag GmbH Co. KGaA, Weinheim. 

Olin has developed a new process for manufacturing PO by direct oxidation of propylene. There are also several peroxidation technologies for production of PO. Possible breakthroughs in the non-propylene chlorohydrin-based routes could reduce the demand for chlorine for making PO. 

Direct comparison of the two main PO production routes - chlorohydrin process and indirect oxidation with organic hydroperoxides - is difficult because the technologies are very different and the portfolio and the back integration of the... 

EO is toxic, highly flammable, and can decompose explosively. EO is manufactured by two different routes, the chlorohydrin process and by direct oxidation of ethylene. 

The most widely used industrial routes to propylene oxide (PO) are based on the chlorohydrin process or hydroperoxide methods. Much attention has also been directed to processes performed in the presence of hydrogen peroxide in the liquid phase with a TS-1 molecular sieve as the catalyst, iron complexes accommodated in amorphous SBA-15 and MCM-41 modified with alkaline metal salts, and SBA-3 mesoporous molecular sieves doped with transition metal ions (Fe, V, Nb, and Ta). 

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. 

Propylene oxide 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 propylene oxide and sodium or calcium chloride. Figure 22.26 is a diagram of the chlorohydrin process. 

The boric and sulfuric acids are recycled to a HBF solution by reaction with CaF2. As a strong acid, fluoroboric acid is frequently used as an acid catalyst, eg, in synthesizing mixed polyol esters (29). This process provides an inexpensive route to confectioner s hard-butter compositions which are substitutes for cocoa butter in chocolate candies (see Chocolate and cocoa). Epichlorohydrin is polymerized in the presence of HBF for eventual conversion to polyglycidyl ethers (30) (see Chlorohydrins). A more concentrated solution, 61—71% HBF, catalyzes the addition of CO and water to olefins under pressure to form neo acids (31) (see Carboxylic acids). 

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. 

To exemplify the second relationship, process competition, there are the two alternate routes from ethylene to ethylene oxide-direct oxidation and chlorohydrination. Even more involved is the acetic acid picture, in which, as has been described, at least ten processes have been in use at the same time in commercial competition with one another. 

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... 

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