Technology

Today, waste plastic is first pyrolyzed to obtain a pyrolysis oil (pyoil) and gas; and that pyoil is then processed in a steam cracker or fluid catalytic cracker (FCC) to produce ethylene, propylene and a wide variety of other products which can then be used to form polymers.  Since the inlet to the cracking coils in this process is typically 650-750 °C, pyoil feed to steam crackers needs to be light enough to vaporize and not prematurely coke the tubes.  Unfortunately, much of the pyoil produced by current processes has a final boiling point of greater than 700 °C and therefore the amount of this pyoil that can be blended into cracker feed is limited.

Trans Ionics’ process, TransPyr, produces a pyoil than has a final boiling point 250 – 350 °C lower than that produced by other processes and requires only light saturation of olefins to produce a pure paraffinic feed.

To compare TransPyr with conventional pyrolysis, a base case thermal run was carried out using a pure HDPE feed (Figure 1) in a 300 cc stirred autoclave at 450 °C and produced the pyoil product shown in Figure 2.

This liquid represents the entire pyoil product without distillation or hydrotreating and less than 1 wt% coke was produced.

A second run was carried out with the same HDPE feed under TransPyr configuration and conditions at 475 °C and produced the pyroil shown in Figure 3. Again this liquid represents the entire pyoil product and has not been distilled or hydrotreated. Coke yield was less than 0.7 wt% on feed.

Both liquids were analyzed by ASTM D2887. The pyoil from the thermal run showed a final boiling point (FBP) of 655 °C while the TransPyr pyoil showed a FBP of only 390 °C – a reduction of 265 °C. As a result of the lower boiling range, the TransPyr pyoil is expected to behave better when blended into naphtha to a steam cracker.