August 1, 2011
Part of your Coke bottle may come from cellulose. Biofeedstock conversion to traditional petrochemicals is receiving more and more attention. These processes are attractive from a sustainability perspective, and, as the price of oil increases, biobased methods may actually become the low-cost routes.
One of the potential drawbacks to using feedstocks based on sugar and starch food crops is the “food-versus-fuels” dilemma, which can be restated as “food versus chemicals and plastics”. Technologies that use nonfood feedstocks such as cellulose, however, can obviate this problem. The challenge is that cellulose is difficult to derivatize by fermentation or chemical techniques.
T. Zhang and co-inventors found catalysts and operating conditions that can convert cellulose to ethylene glycol (EG) in one step in fairly good yields. The catalyst that appears to give the best selectivity is 15% nickel and 30% tungsten supported on activated carbon. The catalytic conversion of cellulose was carried out in a 200-mL autoclave at 5 MPa hydrogen pressure and 240 °C for 30 min. In each experiment, 1.0 g cellulose, 0.3 g catalyst, and 100 mL water were added to the reactor and stirred. When the Ni–W/C catalyst is used, cellulose conversion was 100%, and EG yield was 69%.
Coca-Cola is promoting a “PlantBottle” that it claims is poly(ethylene terephthalate) made from “green” EG and petroleum-based terephthalic acid. The EG is produced from ethylene made by dehydrating fermentation ethanol. The invention described here is a more direct, and potentially more cost-effective, route to green EG. This route also has the virtue of starting from a nonfood food crop. (Dalian Institute of Chemical Physics [China]. US Patent 7,960,594, June 14, 2011; Jeffrey S. Plotkin)