January 31, 2011
Produce ethylene from oil-based and biobased feedstocks. Combining biofeedstocks and petroleum hydrocarbon feedstocks has the potential to optimize the economics of olefin production in a fluid catalytic cracking (FCC unit). Inventors A. de R. Pinho, J. A. R. Cabral, and L. F. Leite performed experiments in which they fed ethanol (EtOH) and heavy gas oil to an FCC reactor. They found that the best way to run this process is to feed the EtOH and heavy oil into separate reaction zones instead of feeding a mixture of the components into one zone.
To demonstrate this invention, a 4:1 mixture of heavy gas oil and EtOH was introduced into the FCC reactor in a single batch. At a reactor temperature of 540 °C, pressure of 239 kPa, and contact time of 1.3 s, ethylene was produced in 4.4% yield, but ethane was coproduced in 5.9% yield. The inventors attribute the undesirable high yield of ethane to hydrogen donation from the heavy oil to the produced ethylene promoted by the FCC catalyst.
In a second experiment, the heavy oil and EtOH were fed to the reactor in separate reaction zones under conditions similar to the first experiment. The contact time for the EtOH in the second experiment, however, was limited to 0.06 s, whereas the heavy oil contact time was 1.3 s as in the initial experiment. Feeding the two feedstocks separately doubled the ethylene yield to 11.1% and halved the undesirable ethane yield to 2.3%. (Petroleo Brasileiro S.A.-Petrobras [Rio de Janeiro]. US Patent 7,867,378, Jan. 11, 2011; Jeffrey S. Plotkin)