Propylene Oxide Production from Propylene and Hydrogen Peroxide

The process under analysis comprises three major sections: (1) Epoxidation; (2) Raw Materials Recovery; and (3) Purification.

Epoxidation. Fresh propylene, along with propylene recovered downstream and hydrogen peroxide, are fed to fixed-bed reactors, where the epoxidation takes place in the presence of titanium silicate catalysts. Fresh and recovered methanol, used as reaction solvent, are also fed to the reactors.The reaction is carried out in the liquid phase, at elevated pressures and moderate temperatures. The reactors are operated alternatively: while one is in operation, the other is in regeneration mode. More than 95% of the propylene is converted to Propylene Oxide. The epoxidation yields a mixture containing the Propylene Oxide product and water as co-product, but also unreacted propylene, methanol and residual amounts of impurities such as glycol ethers.

Raw Materials Recovery. The epoxidation effluent is passed subsequently through a flash vessel and two distillation columns for unreacted propylene and methanol recovery. Each raw material is sent to a different column in order to remove impurities and is recycled to epoxidation.

Purification. The crude PO is directed to a extractive system composed of two distillation columns, in which most hydrocarbon contaminants are stripped off, using an aqueous solution of tert-butyl alcohol. The bottom product of the system is fed to a last column, which further purifies the Propylene Oxide from impurities.