Transesterification of Bis(2-Ethylhexyl) Phthalate for the Recycling of Flexible Polyvinyl Chloride Scraps in the Circular Economy Framework

The identification of suitable process solutions for the recycling of plastics is nowadays one of the main challenges to reduce their environmental impact and promote their sustainability. In this context, the recycling of flexible polyvinyl chloride (PVC) has severe limitations because this material can contain bis(2-ethylhexyl) phthalate (DEHP), a plasticizing additive recently banned by the European Chemicals Agency (ECHA) due to its endocrine disruptor effect. In this study, we investigated a transesterification process for the possible conversion of DEHP to other less toxic phthalates applicable in the context of PVC mechanical recycling using a selective dissolution process. Different catalytic routes have been tested to find optimal concentrations for pure DEHP conversion and applied under real process conditions. Best results have been obtained at 80 degrees C with tetrabutyl titanate [Ti(OBu)(4)], using alcohol/DEHP molar ratios from 10:1 to 5:1, with conversions of more than 90% for pure DEHP in 15 min. However, limitations are related to the final conversion of DEHP in the presence of the PVC phthalate mixture, ranging between 57 and 60% after 90 min for the Ti(OBu)(4) catalyst. Such results are ascribed to dilution for complete PVC dissolution and the preferential formation of monosubstituted phthalates.

Automated summary

This study investigated a transesterification process to convert DEHP to less toxic phthalates in the context of PVC mechanical recycling, achieving high conversion rates for pure DEHP but facing limitations in the presence of PVC phthalate mixture.