Selüloz Asetat Üretimi İçin Çevre Dostu Bir Çözücü Seçeneği: Etil Laktat

Abstract

Bu çalışmanın amacı, selüloz asetat sentezi sırasında endüstriyel üretimde en çok tercih edilen çözücü olan asetik asidin yerine biyobozunur etil laktatın kullanım olanaklarını belirli koşullar altında araştırmaktır. Çalışma sürecinde, sırasıyla su ve asetik asit ile ön işlemlere (aktivasyona) uğratılmış çözünür hamur lifleri, preslendikten sonra etil laktat içinde dağıtılmış ve ardından sülfürik asit katalizörlüğünde asetik anhidrit ile asetilasyon reaksiyonuna tabi tutulmuştur. Asetillenmiş selülozun özellikleri X-ışını kırınım analizleri, Fourier-transform kızılötesi spektroskopisi ve diğer kimyasal analiz yöntemleri (viskozite, bağlı asit yüzdesi) kullanılarak belirlenmiştir. Çözünür hamuru kullanılarak 40°C'de etil laktat içinde 2,79 DS değerine sahip selüloz asetat üretmenin mümkün olduğu belirlenmiştir. Fourier-transform kızılötesi spektroskopisi çalışmaları, asetil gruplarının varlığını gösteren 1739 cm-1 bölgesinde karakteristik bir bant genişlemesi ortaya çıkarmıştır. X-ışını kırınım analizlerinin sonuçları da selülozun kristal yapısının tamamen dağıldığını ve difraktogramlarda bant genişlemelerinin meydana geldiğini göstermiştir. Bununla birlikte, X-ışını difraktogramları üzerinde yapılan hesaplama kristalit boyutları açısından da ilginç bulgular sağlamıştır. Asetatların kristalit boyutlarının çözünür hamura kıyasla daha yüksek olduğu görülmüştür. Numunelerin yüksek kristalinitesinin çözünme gibi işleme özellikleri açısından bir sorun teşkil ettiği belirlenmiştir. Kullanılan çözücüler arasında yalnızca Dimetilsülfoksitin yeterli çözme gücüne sahip olduğu görülmüştür.

Keywords

• − Selüloz asetat sentezi
• Etil laktat
• Çözücü değişimi
• Fourier dönüşümü kızılötesi spektroskopisi
• X-Işını kırınım analizi

An Environmentally Friendly Solvent for Cellulose Acetate Production: Ethyl Lactate

Abstract

The aim of this study was to investigate the possibilities of using biodegradable ethyl lactate instead of acetic acid, the most preferred solvent in industrial production, during cellulose acetate synthesis under certain conditions. In the study, dissolving pulp fibres, which were activated with water and acetic acid respectively, were dispersed in ethyl lactate after pressing and then subjected to acetylation reaction with acetic anhydride catalysed by sulfuric acid. The properties of acetylated cellulose were determined using X-Ray diffraction analysis, Fourier-transform infrared spectroscopy, Differential Scanning Calorimetry and other chemical analysis methods (viscosity, the percentage of bounded acid, chemical resistance). It was determined that it was possible to produce cellulose acetate with a DS value of 2.79 in ethyl lactate at 40°C using dissolving pulp. Fourier-transform infrared spectroscopy studies revealed a characteristic band broadening in the 1739 cm-1 region, indicating the presence of acetyl groups. The results of X-ray diffraction analyses also showed that the crystalline structure of cellulose was completely dispersed and band broadenings on diffractograms occurred. However, the calculation made on X-ray diffractograms also provided interesting findings in terms of crystallite sizes. It was observed that the crystallite sizes of the acetates were higher compared to the dissolving pulp. It was determined that the high crystallinity of the samples posed a problem in terms of processing properties such as dissolution. Among the solvents used, only Dimethylsulfoxide was found to have sufficient dissolving power.

Keywords

• Synhthesis of cellulose acetate
• Ethyl lactate
• Solvent exchange
• Fourier-transform infrared spectroscopy
• X-Ray diffraction analysis

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