Patent Watch

May 26, 2014

Use an economical propylene oxide process to make epichlorohydrin. Recently, Dow Chemical, in collaboration with BASF, developed and commercialized a method of producing propylene oxide (PO) that avoids unwanted coproducts. The process relies on a reaction between propylene and hydrogen peroxide, catalyzed by titanium silicalite (TS-1). This method frees PO producers from having to cope with the market vagaries of styrene or methyl tert-butyl ether, which are coproducts of traditional PO manufacture. Two commercial plants using this process are in operation, and another is under construction.

H. L. Crampton and co-inventors are applying this technique to producing other oxiranes, such as epichlorohydrin, the key raw material for making epoxy resins. Epichlorohydrin is currently made by the reaction of allyl chloride with hypochlorous acid. The resulting mixture of dichloropropanol isomers is dehydrohalogenated with base to give epichlorohydrin.

The inventors’ method uses the reaction between allyl chloride and hydrogen peroxide, a simpler and potentially more economical route. In one of the patent’s examples, the inventors added allyl chloride, TS-1 catalyst, and solvents methanol and o-dichlorobenzene to a jacketed glass reactor. They brought the reaction mixture to 25 ºC and then added aqueous hydrogen peroxide slowly to the reactor. When the mixture was stirred, heat released by the reaction raised the temperature to 40 ºC, and a cooling coil kept it at that temperature. After 60 min, the conversion of hydrogen peroxide was 99.3% and selectivity to epichlorohydrin was 94.7%. (Dow Global Technologies [Midland, MI]. US Patent 8,697,895, April 15, 2014; Jeffrey S. Plotkin)