| Oxidation of propylene with air or oxygen yields a spectrum of products consisting of aldehydes, ketones, and epoxides. One of the important industrial chemicals obtained from propylene oxidation is propylene oxide. Currently it is manufactured by a liquid phase oxidation process, and recent publications and patents have appeared highlighting development of the vapor phase catalytic process. Partly this is spurred by the success in the production of ethylene oxide from ethylene, the immediately preceding homologue of propylene. The gas phase oxidation process over silver catalyst has now replaced the liquid phase oxidation. However such a transition has not yet occurred for propylene oxide production.; The present investigations focus on the performance of a number of catalysts for the oxidation of propylene to propylene oxide. The catalyst systems studied include bismuth molybdate, bismuth molybdate promoted with methylene chloride, tungstates of silver and iron, zirconium dioxide, and a molybdate doped with an alkali and called catalyst-K. Catalyst-K was found to be superior, and was subjected to further study. A high molar feed ratio of propylene to oxygen of 5 and a low contact time of the reactants favored the production of propylene oxide while carbon dioxide formation was considerably reduced. The total pressure was kept at one atm. and the reaction temperature was varied between 360(DEGREES)C and 403(DEGREES)C. A parallel reaction scheme was proposed for the production of acrolein, acetone, propylene oxide and carbon dioxide. The overall rate of the raction 'r' was r = 5.39 x P(,1)(P(,2))('0.4)exp(-5690/RT) gmole/g-cat. hr., where P(,1) is the partial pressure of propylene in atm., P(,2) is the partial pressure of oxygen in atm., temperature T in (DEGREES)K and R is the universal gas constant in cal/g-mole/(DEGREES)K. The predicted initial rates were within 5 percent of the calculated values. |
