Researchers develop process to remove 6PPD from waste tires

Newark, Delaware – Researchers at the University of Delaware have developed a technique to remove anti-degradant substance 6PPD from end-of-life tires (ELTs).

The process, developed by the center for plastics innovation and department of chemical and biomolecular engineering, ‘upgrades 6PPD’ into safe chemicals and turns leftover crumb rubber into aromatics and carbon black.

Led by Dion Vlachos, University of Delaware Dan Rich chair in energy, the research tried to remove 6PPD from ELTs via chemical extraction, the US university team reported 20 Nov.

The process involved heating 'millimetre-sized' pieces of tire or crumb rubber in a microwave reactor: using a chemical solvent to quickly separate the 6PPD from the other molecules present.

Once the 6PPD molecules are removed, they can be chemically converted into safe chemicals that can be used or sold for a small price, according to the release.

The rest of the tire, meanwhile, can be safely recycled for use in sports pitches and road surfaces or processed into feedstock materials such as as carbon black.

6PPD is currently used by the tire industry to ensure that the tire components are protected from ozone and oxygen.

However, over the recent years, some researches have raised concerns over a 6PPD transformation product, 6PPD-quinone (6PPDQ), which can impact aquatic life, particularly salmon.

According to Vlachos, attempts to break down the tire material using high heat, including pyrolysis, have failed to remove 6PPD from ELTs.

The diketone molecules remain in the pyrolysis oil after the process, the research team leader explained.

If the pyrolysis oil is then used in fuel or other materials, the diketone molecules will remain in the product, potentially causing environmental damage.

The approach has been proven at lab-scale, continued Vlachos, adding that a techno-economic analysis showed “the cost looks to be very reasonable.”