August 19, 2013
Make alkylbenzenes from bioethanol. The use of bioethanol as a feedstock for producing conventional petrochemicals is one way to make environmentally friendly or “green” products. For example, Braskem cracks bioethanol to make ethylene and then converts the ethylene to high-density polyethylene (HDPE). The HDPE is identical to petroleum-based HDPE and has the marketing advantage of being renewable. Coca-Cola is sponsoring work in which ethylene from bioethanol is converted to ethylene glycol, a feedstock for 30%-green poly(ethylene terephthalate) for soda and water bottles.
E. Sanchez and E. Guillon disclose a method to convert bioethanol-derived ethylene to a mixture of olefinic oligomers and then to convert these long-chain green olefins to branched alkylbenzenes that can be used to make detergents. They first describe catalysts and operating conditions for cracking bioethanol to ethylene. They then show that ethylene can be oligomerized in two stages and that a portion of the oligomers can be used to alkylate benzene.
The first stage uses a supported nickel catalyst at 140 °C and a pressure of 3.0 MPa. The composition of the effluent is 5 wt% ethylene and 95 wt% C4+ olefins, of which 73.7 wt% is C4–C8 olefins, and 26.3 wt% is C9+ olefins.
The effluent from the first stage is sent to a second-stage oligomerization reactor that contains a ZSM-5 zeolite catalyst and is operated at 220 °C and 4.0 MPa. The effluent is fractionated to give the olefin distribution shown in the table.
In the alkylbenzene production step, the C10–C14 fraction reacts with benzene over a zeolite USY catalyst at 135 °C and 4 MPa. The benzene/olefin mol ratio is 30:1. The olefin conversion is >95%, and the selectivity to alkylbenzenes is 95%. (IFP Energies nouvelles [Rueil-Malmaison, France]. US Patent 8,461,405, June 11, 2013; Jeffrey S. Plotkin)
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