Catalytic upcycling of phthalate plasticizers

Bernus Ric, Carla
Windels, Simon (dir.)

Universidad de Zaragoza, CIEN, 2022

Graduado en Química

Resumen: The importance of plastics - has been increasing over the last century, reaching production rates of 368 million tons in 2019. Today, the plastic economy is still dominated by a linear profile (consecutive production, consumption and disposal) as less than 30% of the produced plastics are recycled. In order to minimize the pressure on natural resources, to drastically reduce CO2 emissions and to achieve the 2050 climate neutrality target, The European Green Deal and its “Circular Economy Action Plan” were initiated. In this report we will go deeper into the concept of legacy additives and in particular the use of phthalate plasticitisticzers in PVC. The phthalates plasticizers were the general plasticizer used in industry, however, since that they are classified as endocrine disruptors and reprotoxic the European Registration, Evaluation and Authorization of Chemicals has implemented strict regulations for the production, handling and disposal of these components. In fact, low molecular weight phthalates are currently banned in Europe, so that the plasticizers can also not be present in recycled material, which complicates traditional recycling of flexible PVC. In this report, it was investigated whether these toxic phthalate esters can possibly be revalorized via the oxidative coupling to form 3,3’,4,4’-biphenyltetracarboxylic tetraester (S-BPTT), which is used as precursor for polyimide resins.
Throughout this dissertation, the effect of the main reaction parameters on the activity (TON) and selectivity of the oxidative coupling of dimethyl phthalate has been investigated. It was in particular observed that rather drastic conditions (16 bar O2 and ≥140 °C) are necessary to obtain a fairly active coupling system. While many solvents proved completely unsuitable for the oxidative coupling of phthalates, the addition of acetic acid to the mixture improved both the activity and selectivity of the gold catalyst. In the last steps of this work, the Au-catalyst and its preparation method was further analysed. The urea deposition method in combination with an activation step (heat treatment in air) proved to be the most suitable method to produce heterogeneous catalyst up to 8 wt.% Au. Remarkably, it was concluded that the metal loading does not affect the catalysts performance, as the chosen preparation method presumably gives rise to catalysts with the same metal particle sizes regardless of the metal loading. In the catalyst support screening, Au supported on ZrO2 proved to be an excellent catalyst, as it combined the highest observed coupling activity with a high regio- and chemoselectivity.

Tipo de Trabajo Académico: Trabajo Fin de Grado