Characterization of waste PET simultaneous hydrolysis-glycolysis products by DSC: Determination of product composition and distribution

Öz

In this study, the possible product composition and distribution of the functional products obtained as a result of the depolymerization of waste PET were investigated using DSC technique. Thus, it was provided to obtain data for the optimization and standardization of the reaction conditions. First, waste PET flakes obtained from post-consumer water bottles were depolymerized at high pressure by simultaneous hydrolysis-glycolysis reactions. The reactions were carried out using a fixed amount of water, at different mole ratios of PET/diol, in the presence or absence of solvent, and at different temperatures. Crude depolymerization products were extracted with boiling water and separated into "water-soluble and crystallizable (WSCF)" and "water-insoluble (WIF)" fractions. Then, the yields% by weight (conversion ratios) of depolymerization reactions and, these fractions' ratios% by weight, functional group contents (acid value (AV), hydroxyl value (HV) analyses), theoretical number average molecular weights (Mn) were determined, and DSC analyzes were performed. The optimum conditions for most efficient fragmentation were observed in the depolymerization reaction that mole ratio of PET/diol was 1/5, in the presence of 2.5 moles of water, on the xylene medium and at 200oC. In these conditions, 99% conversion was achieved, and product distribution was observed as 81% WSCF and 19% WIF. In the WSCF product composition, PET's hydroxyl-terminated monomer (BHET) and in the WIF product composition, PET's carboxyl-terminated monomer were obtained at around~80% and ~80%, respectively. The Mn value of the final product composition is 234, the AV and HV values are 121 mg KOH/g and 358 mg KOH/g, respectively.

Anahtar Kelimeler

• Waste PET
• Depolymerization
• Recycling
• DSC technique
• Product composition and distribution

Proje Numarası

FBA-2017-24002

Atık PET’in eş zamanlı hidroliz-glikoliz ürünlerinin DSC ile karakterizasyonu: Ürün bileşimi ve dağılımının belirlenmesi

Öz

Bu çalışmada, atık PET'in depolimerizasyonu sonucunda elde edilen fonksiyonel ürünlerin muhtemel ürün bileşimi ve dağılımı DSC tekniği kullanılarak araştırılmıştır. Böylece, reaksiyon koşullarının optimizasyonu ve standardize edilmesi için veriler elde edilmesi sağlanmıştır. Öncelikle, tüketim sonrası su şişelerinden elde edilen atık PET kırpıntıları, yüksek basınçta, eş zamanlı hidroliz-glikoliz reaksiyonları ile depolimerize edilmiştir. Reaksiyonlar, sabit miktarda su kullanılarak, farklı PET/diol mol oranlarında, çözücü varlığında veya yokluğunda ve farklı sıcaklıklarda gerçekleştirilmiştir. Ham depolimerizasyon ürünleri, kaynar su ile ekstrakte edilerek "suda çözünen ve kristallenebilen (SÇ+)" ve "suda çözünmeyen (SÇ-)" fraksiyonlarına ayrılmıştır. Daha sonra, depolimerizasyon reaksiyonlarının ağırlıkça %verimleri (dönüşüm oranları), bu fraksiyonların ağırlıkça %oranları, fonksiyonel grup içerikleri (asit indisi (AI), hidroksil indisi (HI) analizleri), teorik sayıca ortalama molekül ağırlıkları (Mn) belirlenmiş ve DSC analizleri gerçekleştirilmiştir. En etkin parçalanma için optimum koşullar; PET/diol mol oranının 1/5 olduğu, 2.5 mol su varlığında, ksilenli ortamda ve 200oC’de gerçekleştirilen depolimerizasyon reaksiyonunda gözlenmiştir. Bu koşullarda, %99 oranında dönüşüm sağlanmış %81 (SÇ+) ve %19 (SÇ-) şeklinde ürün dağılımı gözlenmiştir. (SÇ+) ürün bileşiminde ~%80 civarında, PET’in hidroksil sonlu monomeri (BHET) ve (SÇ-) ürün bileşiminde de ~%80 civarında PET’in karboksil sonlu monomeri elde edilmiştir. Nihai ürün bileşiminin Mn değeri 234, AI ve HI değerleri de, sırasıyla, 121 mg KOH/g ve 358 mg KOH/g’dır.

Anahtar Kelimeler

• Atık PET
• Depolimerizasyon
• Geri dönüşüm
• DSC tekniği
• Ürün bileşimi ve dağılımı

Destekleyen Kurum

İstanbul Üniversitesi-Cerrahpaşa, Bilimsel Araştırma Projeleri Koordinasyon Birimi

Proje Numarası

FBA-2017-24002

Kaynakça

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