MSc.Thesis Defense:Gökmen Tamer Şanlı
SUSTAINABLE RECYCLING OF WASTE CELLULOSE: MICROWAVE-ASSISTED CELLULOSE DISSOLUTION IN IONIC LIQUID AND REACTOR DESIGN
Gökmen Tamer ŞANLI
Material Science and Nano Engineering Program, MSc. Thesis, 2024
Thesis Jury
Prof. Yusuf Ziya MENCELOĞLU (Thesis Advisor), Prof.Fevzi Çakmak CEBECİ,
Prof. Elçin Yılmaz
Date & Time: 23rd, July 2024 – 3.00 PM
Place: FENS L063
Keywords : Cellulose Dissolution, Ionic Liquid, Microwave, Reactor Design, Recycling, Natural Polymer
Abstract
The reuse of waste materials is crucial for a sustainable future. In recycling processes, it is essential to select processes that are both economically and environmentally suitable, as this is important for both environmental sensitivity and economic viability. In recent years, recycling of waste textile fabrics has become increasingly important. Materials such as polyester, polyamide, acrylic, and elastane are widely used synthetic polymers in the textile industry, and their recycling with organic solvents forms a straightforward process. On the other hand, cellulose-containing materials such as cotton, linen, hemp, and ramie are among the most challenging materials to recycle in the textile industry. Cellulose forms a complex structure due to the hydrogen bonds it creates within and between molecules, making it difficult to dissolve. Although some solvent combinations have been developed to dissolve cellulose, these solvents are not sufficiently sustainable or environmentally friendly, such as N,N-dimethylacetamide/LiCl (DMAc/LiCl), N,N-dimethylsulfoxide/tetrabutylammonium fluoride (DMSO/TBAF), copper (II) hydroxide/aqueous ammonia (cuoxam). Apart from these solvents, N-methylmorpholine-N-oxide (NMMO), also known as Lyocell, is considered relatively more sustainable and environmentally friendly for cellulose dissolution compared to other chemicals, but the polymerization degree of cellulose used in this process typically ranges between 300- 600, resulting in lower material strength.
Recently, it has been discovered that ionic liquids can also be used in cellulose dissolution processes. Ionic liquids, which contain organic cations and organic/inorganic anions, are environmentally friendly and highly sustainable due to the millions of possible combinations that can be created. In this thesis, the dissolution of cellulose using 1-butyl-3-methylimidazolium chloride ionic liquid has been studied both through conventional heating methods and microwave-assisted heating using a household microwave oven. After it was understood that the dissolution process is significantly accelerated when using the microwave method, a temperature-controlled microwave reactor with a capacity of 10 liters and equipped with 3 magnetrons was designed and got manufactured to enable small-scale production on an industrial level. In this reactor, the dissolution of cellulose under different parameters such as temperature and concentration was investigated. Additionally, the usability of the prepared solution has been tested through yarn production experiments in both laboratory and industrial settings. The results indicate that the cellulose regenerated in the coagulation bath transitions from cellulose I to cellulose II form, exhibits a more amorphous structure, and undergoes cellulose depolymerization during the dissolution process.