Currently, PO is produced commercially by:
The POSM process convert propylene and ethyl benzene simultaneously into propylene oxide (PO) and styrene monomer (a co-product). The PO/TBA process converts isobutane into PO and tertiary butyl alcohol (TBA) (a co-product). TBA is the main raw material for the fuel additive MTBE. In the chlorohydrin process the propylene is chlorinated and then hydrolysed to PO. The POSM is considered the best because of its significantly lower costs.
Over the years researchers have been trying to find a direct route, analogous to the silver-catalyzed oxidation of ethylene to ethylene oxide, to prepare PO. Unlike ethylene oxide, the allylic hydrogen in propylene carried the oxidation all the way to CO2.
A related direct oxidation approach is to use a combination of oxygen and hydrogen as the oxidizing agent, making water as a coproduct. One of the challenges to this method is that the water tends to hydrolyze the propylene oxide to produce high levels of propylene glycol and oligomers.
Lyondell Chemical Company, based in Houston, Texas, the world's leading producer of propylene oxide (PO), is working on a one-step, direct oxidation PO technology. The new technology is to produce just PO without co-products. Since 1990, Lyondell has secured more than 130 US patents in this area.
Sumitomo Chemical of Japan has also announced the development of a new coproduct-free route to propylene oxide. This technology is believed to proceed via oxidation of cumene to cumene hydroperoxide, which in turn is used to epoxidise propylene. The resulting byproduct, cumyl alcohol, then undergoes dehydration and hydrogenation to regenerate the starting cumene. The cumene method for PO production is characterized by high conversion (99.5%) and selectivity (98-99.3%). To produce 1 tonne of PO, it need 0.78 t of propylene, 0.21 t of cumene and 0.06 t of hydrogen.
August 1, 2002: BASF and Dow Chemical Company announced plans to join forces in the development of technology for the manufacture of propylene oxide (PO) utilizing hydrogen peroxide (HP) as a key raw material. Dow inherited the HP-PO technology when it acquired EniChem's polyurethanes business in May 2001. BASF has been developing the HP-PO technology since 1995.
