December 3, 2012
Make intermediate olefins from bioethanol. Braskem (São Paulo, Brazil) is producing “green” polyethylene made by polymerizing ethylene derived from bioethanol. This type of polymer has changed the meaning of “green polymer”. Ten years ago, “green” meant that the polymer is biodegradable; nowadays, “green” can also mean that the polymer is produced from a renewable resource.
The marketplace seems to prefer the newer definition. For example, Braskem’s green polyethylene does not require any changes in the downstream manufacturing or packaging equipment; but consumer-products companies can now put “environmentally friendly” on their product label. This is a driving force to broaden the range of polymers that can be made from bioethanol.
V. Coupard and co-inventors disclose a procedure for synthesizing ethanol-cracking catalysts that produce C3–C6 olefins in addition to ethylene. They found that C3–C6 olefins are favored when the catalysts have larger pore volumes. The pore volume is controlled by adjusting the level of pore-volume–forming agent used to prepare the zeolite-containing catalyst.
The pore-volume–forming agent is a petroleum fraction, preferably a paraffinic kerosene fraction that has 10–14 carbon atoms. The forming agent is used with a surfactant that makes it possible to prepare an emulsion with alumina and the zeolite in the aqueous phase.
To test the catalysts’ efficacy, a 1:1 w/w EtOH–H2O solution is passed over the catalyst at 515 °C and 0.15 MPa. The inventors tested four catalysts: one in which no forming agent was used and three with increasing levels of forming agent. In all cases, EtOH conversion was >99%, but the selectivity to C3–C6 olefins increased from 69.7% with no forming agent to >88% when the highest level of agent was used. (IFP Energies nouvelles [Rueil-Malmaison, France]. US Patent 8,309,781, Nov. 13, 2012; Jeffrey S. Plotkin)