Propylene oxide with aqueous hydrogen peroxide

An issue which deserves further mention is the environmentally fiiendly nature of TS-l/H Oj system. It involves the use of a safe silica based catalyst, titanium silicalite, and a reagent, hydrogen peroxide, which yields water as the coproduct. This holds for the in situ route illustrated in Scheme I and also for the epoxidation of propylene with preformed hydrogen peroxide, either used as an aqueous solution (72) or extracted by means of die epoxidation solvent (Scheme 11). Hazardous chemicals, such as chlorine, performic or other organic peracids, are not required in the process. The disposal of chlorinated salts or the recycle of brine (chloroydrin process) and any possible burden resulting from the coproduction of odier chemicals (styrene and r-butanol in the hydroperoxide route) are eliminated. The liquid phase oxidation of isobutane and ethylbenzene with air under pressure and at high temperature, to produce... 

Using hydrogen peroxide for the manufacture of propylene oxide means that water is co-produced in the reaction and no by-product needs to be disposed of or utilized. The reaction is carried out in a dilute solution of hydrogen peroxide (<10 wt%) in aqueous methanol, below 60°C and moderate pressure. The reaction is fast even with < 1 % H2O2. 

The TS-1 catalyst has also been found effective in the epoxidation of olefinic compounds. It is of particular interest in the preparation of propylene oxide by oxidation of propylene with hydrogen peroxide (Hoelderich, 1988). Ethylene has also been epoxidized to ethylene oxide with 30% H2O2 in aqueous /-butanol to obtain 96% selectivity at 97% H2O2 conversion (Sheldon, 1991). 

Disturbances of the hydrophilic-hydrophobic balance of the monolayer-forming material could also be a factor to exploit when studying film responsiveness to external stimuli. In combination with the oxidation-responsive poly(propylene sulfide), PPS, PEO forms di- and triblock copolymers whose molecular and supramolecular organization is strongly dependent on the oxidative stress present in the system [52], Monolayers from PPS-PEO on an aqueous subphase remain stable due to PPS hydrophobicity. However, in the presence of hydrogen peroxide in the subphase, oxidation of the PPS blocks occurs and the hydrophilic-to-lipophilic balance is disturbed, producing hydrophilic species. Obviously, an increased hy-drophilicity favors dissolution of the material in the subphase and, consequently, a decrease of the mean molecular area. In this study [52], the monolayer model was used to explain physical details of vesicle degradation under the oxidative stress. 

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