Plastics are a petroleum product. To make plastics, oil is broken down into lower olefins--such as ethylene and propylene--at large petrochemical plants. These lower olefins serve as precursors in the production of plastics.
There has been some research into making these lower olefins from something other than oil. One method involves burning plant material to create a synthesis gas (syngas) that reacts with a catalyst to breakdown the syngas into these lower olefins. The problem, however, has been that the yield of lower olefins from this process has been low--only 40%.
Now researchers from Utrecht University and Dow Chemical Company have developed a new, iron-based catalyst using nanoscale particles that improves the yield for this plant-based process by 50%.
The research, which was published in February 17th edition of Science, led by Krijn P. de Jong,professor of inorganic chemistry and catalysis at Utrecht University, focuses on an iron-based catalyst that allowed for much smaller grains (measured at a mere 20 nanometers) than the 500-nanometer grain size typically seen for these types of catalysts.
As with all nanocatalysts the benefit of the nanoscale is that you get more overall surface area, which makes the catalysts more reactive.
In this particular case, the Dutch researchers also serendipitously discovered that the catalyst’s effectiveness improved when some of the material became contaminated with sulfur and sodium.
This method of producing plastics from plant materials should not in any way be confused with the synthesis of plastics from corn and sugar—so-called bioplastics. Perhaps the most notable difference between these two is that bioplastics are biodegradable, whereas the lower olefin-derived plastics are not.
Of course, some environmentalists may be disturbed that we are creating another plastic that is non-biodegradable. However, they may take some comfort in knowing that at least now these olefins could potentially come from a renewable resource as opposed to the finite resources of oil.
While there is a 50% improvement in this catalyst’s ability to change the syngas into lower olefins, it still only manages to turn 60% of the syngas into the plastic precursors (as opposed to 40% with the previous catalysts), leaving 40% still as natural gas or leftover materials.
A 50% improvement in yield of just about any chemical process is significant, however, it’s not clear, according to some independent scientists interviewed in the Los Angeles Times, whether this promising experiment will make economic sense in the long run.
Dexter Johnson is a contributing editor at IEEE Spectrum, with a focus on nanotechnology.
