Make propylene from ethylene without adding butene.(Chementator)

Researchers from the Chemical Resources Laboratory of Tokyo Institute of Technology (Tokyo; res.titech.ac.jp) have developed a new catalytic process to make propylene from ethylene. Normally, propylene is made by the metathesis reaction of ethylene and butene, which requires a separate source for supplying the butene.

The new process produces propylene from ethylene at about 400[degrees]C and 1 bar pressure. Ethylene and a trace of water are reacted in a fixed-bed reactor over a nickel catalyst that is supported on mesoporous silica. The net reaction produces two moles of propylene from three moles of ethylene. The actual reaction mechanism is believed to follow two steps on the same catalyst, says professor Masakazu Iwamoto: First two ethylene molecules combine to form butene, then a metathesis of the butene with a third ethylene forms two propylene molecules. In a single pass, the ethylene conversion is about 53%, with propylene and butene selectivities of about 50 and 42%, respectively. The butene is converted to propylene on the same catalyst by reacting with ethylene to increase propylene yield further.

The new process is expected to boost the production of propylene when combined with an existing cracker for making ethylene, which is important as the demand for propylene becomes larger than ethylene. Iwamoto plans to begin a cooperative study with industrial firms to commercialize the process.