Titanate Nanotubes as New Nanostrutured Catalyst for Depolymerization of PET by Glycolysis Reaction

Gabrielle Ritter Lima,Wesley Formentin Monteiro,Rosane Ligabue,Ruth Marlene Campomanes Santana

doi:10.1590/1980-5373-mr-2017-0645

Gabrielle Ritter Lima, Wesley Formentin Monteiro + Show 2 more

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https://doi.org/10.1590/1980-5373-mr-2017-0645

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Abstract

The final destination of PET packaging is creating economic and environmental concerns. One of the alternatives to minimize this problem would be making use of chemical recycling of this material through glycolysis with the aim to produce bis(hydroxiethyl) terephthalate, BHET monomer. This reaction is well known, but it still presents problems as BHET purity since it makes necessary the development of new catalysts highly selective. In this context, the present work studied the catalytic activity of a nanostructured material, titanate nanotubes (TNT), and compared it to a commercial catalyst (zinc acetate), which is the most used for this glycolysis reaction according to literature researches, and analyzed the influence of PET type (virgin and post-consumer) in the depolymerization for reaction times of 2, 3 and 4 hours. Using TNT as catalyst, BHET production yield and values of turnover number for the evaluated reaction times were higher than the results using Zn(OAc)2 for virgin PET, proving itself as a promising catalyst.

Highlights

Poly(ethylene terephthalate), PET, is a commodity polymer of great importance due to its excellent physical and chemical properties[1]
This study aims to evaluate the catalytic activity of titanate nanotubes (TNT) compared with zinc acetate, at different reaction times and to evaluate the influence of PET source in the PET depolymerization
In order to confirm the bis(hydroxyethyl) terephthalate (BHET) production as the main product of PET glycolysis obtained at different times and with catalysts TNT or Zn(OAC)[2], Differential Scanning Calorimetry (DSC), Thermogravimetric Analysis (TGA), 1H and 13C-Nuclear Magnetic Resonance Spectroscopy (NMR) analysis were performed

Summary

Introduction

Poly(ethylene terephthalate), PET, is a commodity polymer of great importance due to its excellent physical and chemical properties[1]. PET offers excellent barrier property and low weight compared to glass packaging[2]. This polymer is especially used in the packing industry. Among the various possibilities to mitigate this problem, the chemical recycling process would be the best alternative for this material. Chemical recycling by glycolysis is one of de most used recycling types It can be described as a depolymerization process by transesterification between PET ester groups and a diol (generally ethylene glycol, EG)[4,5], allowing obtaining of bis(hydroxyethyl) terephthalate (BHET)[6] as main depolymerization product (Figure 1)

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