Propylene chlorohydrin/oxide

Propylene oxide [75-56-9] is manufactured by either the chlorohydrin process or the peroxidation (coproduct) process. In the chlorohydrin process, chlorine, propylene, and water are combined to make propylene chlorohydrin, which then reacts with inorganic base to yield the oxide. The peroxidation process converts either isobutane or ethylbenzene direcdy to an alkyl hydroperoxide which then reacts with propylene to make propylene oxide, and /-butyl alcohol or methylbenzyl alcohol, respectively. Table 1 Hsts producers of propylene glycols in the United States. 

The chlorohydrin process involves reaction of propylene and chlorine in the presence of water to produce the two isomers of propylene chlorohydrin. This is followed by dehydrochlorination using caustic or lime to propylene oxide and salt. The Dow Chemical Company is the only practitioner of the chlorohydrin process in North America. However, several companies practice the chlorohydrin process at more than 20 locations in Germany, Italy, Bra2il, Japan, Eastern Europe, and Asia. 

Epoxid tion. Epoxidation, also referred to as saponification or dehydrochlorination, of propylene chlorohydrin (both isomers) to propylene oxide is accompHshed using a base, usually aqueous sodium hydroxide or calcium hydroxide. 

Yields of propylene chlorohydrin range from 87—90% with dichloropropane yields of 6—9%. The dichloropropane is not only a yield loss but also represents a disposal problem as few uses are known for this material. Since almost all the propylene chlorohydrin is dehydrochlorinated to propylene oxide with lime or sodium hydroxide, none of the chlorine appears in the final product. Instead, it ends up as dilute calcium or sodium chloride solutions, which usually contain small amounts of propylene glycol and other organic compounds that can present significant disposal problems. 

There have been a number of cell designs tested for this reaction. Undivided cells using sodium bromide electrolyte have been tried (see, for example. Ref. 29). These have had electrode shapes for in-ceU propylene absorption into the electrolyte. The chief advantages of the electrochemical route to propylene oxide are elimination of the need for chlorine and lime, as well as avoidance of calcium chloride disposal (see Calcium compounds, calcium CHLORIDE Lime and limestone). An indirect electrochemical approach meeting these same objectives employs the chlorine produced at the anode of a membrane cell for preparing the propylene chlorohydrin external to the electrolysis system. The caustic made at the cathode is used to convert the chlorohydrin to propylene oxide, reforming a NaCl solution which is recycled. Attractive economics are claimed for this combined chlor-alkali electrolysis and propylene oxide manufacture (135). 

Reaction of dibenzylamine with ethylene oxide affords the amino alcohol, 82. Treatment of that product with thionyl chloride gives the a-sympathetic blocking agent, dibenamine (83). (Condensation of phenol with propylene chlorohydrin (84) gives the alcohol, 85. Reaction with thionyl chloride affords the chloride (86). Use of the halide to alkylate ethanolamine affords the secondary amine (87). Alkylation of this last with benzyl chloride... 

The main method to obtain propylene oxide is chlorohydrination followed by epoxidation. This older method still holds a dominant role in propylene oxide production. Chlorohydrination is the reaction between an olefin and hypochlorous acid. When propylene is the reactant, propylene chlorohydrin is produced. The reaction occurs at approximately 35°C and normal pressure without any catalyst ... 

CH2=CH2 + Cl2 + h2o = CH20H-CH2C1 + HC1 Chloroalcohols are important intermediates. Propylene chlorohydrin is made similarly and is used for making propylene oxide by hydrolysis with either calcium hydroxide or sodium hydroxide. If calcium hydroxide is used, the byproduct calcium chloride is useless and must be dumped. If sodium hydroxide is used, the byproduct sodium chloride can be recycled to the Castner-Kellner process. 

Propylene Chlorohydrin. Propylene chlorohydrin is synthesized with the aim of producing propylene oxide. Although the latter is manufactured commercially mainly by the direct oxidation of propylene, the chlorohydrination process is still in limited use. 

In an older version of the synthesis, propylene and chlorine react in an aqueous solution to form propylene chlorohydrin.192-194 The slightly exothermic reaction maintains the 30-40°C reaction temperature to yield isomeric propylene chlorohy-drins (l-chloro-2-propanol/2-chloro-1-propanol = 9 1). The main byproduct is 1,2-dichloropropane formed in amounts up to 10%. The product propylene chlorohydrin then undergoes saponification to propylene oxide with calcium hydroxide or sodium hydroxide. 

Hydroxypropylated starch 1440 E1440 Propylene oxide <10% (or 25%e) Propylene chlorohydrin <1 mg/kg... 

Propylene Chlorohydrin Determine the residual propylene chlorohydrin in hydroxypropyl starch, hydroxypropyl starch phosphate, and oxidized hydroxypropyl starch as directed under Propylene Chlorohydrin, Appendix X. 

Chlorine and hydrogen as obtained directly from the diaphragm cell are both hot and wet, and the 8-12% sodium hydroxide liquid cell effluent still contains 12-19% dissolved ( undecomposed ) sodium chloride. Some applications of these products can use them in the form obtained directly from the cell. For example, propylene chlorohydrin may be ring-closed to propylene oxide using the crude sodium hydroxide solution still containing sodium chloride (Eq. 8.27). However, majority of uses require at least a simple cleanup of the crude products prior to use. 

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]. 

E. Bartolome, W. Koehler, G. Stoeckelman, A. May, Continuous manufacture of propylene oxide from propylene chlorohydrine, U.S. Patent No. 3,886,187,1975, Assigned to BASF Corporation. 

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 first equation shows the formation of hypochlorous acid by the reaction of chlorine and water. The second shows the reaction of the acid with propylene to form propylene chlorohydrin. The third equation represents the dehydrochlorination of propylene chlorohydrin with calcium hydroxide to propylene oxide and aqueous calcium chloride. Sodium hydroxide can also be used in the dehydrochlorination step. The effluent will then be a dilute sodium chloride stream rather than the calcium chloride by-product shown in Eq. (12). 

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