Energy Efficient Plastic Production
Polyethylene is the most common plastic in the world with about 80 million metric tons being produced each year for use in everything from grocery bags to medical implants to bullet-proof vests. But the process for making this ubiquitous plastic is extremely energy-intensive. In the U.S. alone, the amount of power used in the production of ethylene is equivalent to that generated by seven average-sized nuclear power plants – more than 46 million megawatt hours per year. Now a new material has been developed that could make the process much more efficient.
A large portion of the power expended in making polyethylene goes to separating ethylene from a nearly identical chemical, ethane, through a costly distillation technique. The new compound has 13 times more separating power than the materials currently used. The improved performance is attributed to the addition of silver ions which enable the compound to distinguish between ethylene and ethane molecules, “grab” the ethylene molecules from the mixture and then release them once the ethane has been removed.
One drawback is that the silver ions are more prone to picking up contaminants, and since the gas mixtures being used are by-products of petroleum refineries, they can contain impurities which would inhibit the selectivity of the silver ions. But the researchers are hopeful that this can be addressed in the molecular carrier being used.