Lignoselülozik biyokütleden değerli kimyasal eldesinde kullanılabilecek katalizörlerin geliştirilmesi
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Dosyalar
Tarih
2023
Yazarlar
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Yayıncı
Bursa Teknik Üniversitesi, Lisansüstü Eğitim Enstitüsü
Erişim Hakkı
info:eu-repo/semantics/openAccess
Özet
Lignoselülozik biyokütle, sanayileşme ve nüfus artış hızına paralel olarak artan enerji ve kimyasal hammadde ihtiyacının karşılandığı fosil kaynaklara alternatif olarak karşımıza çıkmaktadır. Bitkisel ve tarım atıklarını, hayvansal atıkları ve kentsel atıkları da bünyesinde bulunduran lignoselülozik biyokütle fosil kaynakların aksine sürdülebilir ve yenilebilir kaynaklar arasında önemli yere sahiptir. Lignoselülozik biyokütleden enerji, yakıt ve değerli kimyasalların elde edilmesinde geleneksel olarak kullanılan yöntemler enerji yoğun olan pahalı yöntemlerdir. Bu yöntemlerin yerine oda sıcaklığı ve atmosferik basınç altında gerçekleşen fotokatalitik tepkimelerin kullanılması ekonomik açıdan da sürdürülebilirliliği sağlayacaktır. Bu çalışmada, lignoselülozik biyokütleden fotokatalitik tepkimeyle 5 ve 6 karbonlu şekerler ve bu şekerlerden değerli kimyasal eldesini sağlayacak katalizörlerin sentezi ve tepkime koşullarının belirlenmesi incelenmiştir. Temelde hidrotermal yöntemi esas alarak 4 farlı reçetede ve farklı ağırlık oranların ZnO/TiO2 ikili metal oksit katalizörler sentezlenmiştir. Sentezlenen katalizörler XRD, SEM, FTIR, DRS, fiziksel ve kimyasal sorpsiyon yöntemleri ile karakterize edilmiştir. İkili metal oksit katalizörlerin sentez yöntemleri ve karışım oranlarının fotokatalitik aktivite üzerindeki etkileri incelenerek biyokütle dönüşüm oranı ve ürün verimi açısından en uygun fotokatalizör tespit edilmiştir. Biyokütle kaynağı olarak ham ve seyreltik NaOH ile muamele edilmiş fındık kabuğu ve kahve kabuğu kullanılmıştır. Biyokütlenin fotokatalik bozunması özel olarak tasarlanmış kesikli fotoreaktörde gerçekleştirilmiştir. Fotokatalik bozunma sonucunda elde edillen ürünlerin kimyasal analizi HPLC ile yapılmıştır. Fotoreaktörde gerçekleştirilen fotokatalitik denemelerde biyokütle miktarı, zaman, pH ve H2O2 miktarı parametrelerinin biyokütle dönüşümü ve ürün verimi üzerindeki etkileri incelenmiştir. Elde edilen veriler ışığında ZnO/TiO2 ikili metal oksitlerin sahip olduğu sinerjik etkinin biyokütleden değerli kimyasal eldesindeki önemli role sahip olduğu görülmüştür. 7525ZT-III katalizörünün ürün verimi ve biyokütle dönüşüm konusunda en etkili katalizör olduğu sonucuna ulaşılmıştır. Biyokütle çeşitleri değerlendirildiğinde NaOH ile yapılan ön işlemin kahve kabuğunun üzerinde daha etkili olduğu görülmüştür. Ön işlem sonucunda yapıdaki lignin bariyerinin aşılarak selüloz ve hemiselüloz yapısının serbest kaldığı ve biyokütle yüzey alanının arttığı sonucuna varılmıştır. Parametrik çalışmalar sonucunda da parametrelerin ürün seçiciliği bakımından önem sırası H2O2 miktarı>biyokütle miktarı>zaman>pH olarak bulunmuştur.
Lignocellulosic biomass emerges as an alternative to fossil resources, which meet the increasing need for energy and chemical raw materials in parallel with the industrialization and population growth rate. Contrary to fossil resources, lignocellulosic biomass, which includes plant and agricultural wastes, animal wastes and urban wastes, has an important place among sustainable and renewable resources. Traditionally used methods of obtaining energy, fuel and valuable chemicals from lignocellulosic biomass are energy-intensive and expensive methods. The use of photocatalytic reactions at room temperature and atmospheric pressure instead of these methods will also provide economic sustainability. In this study, the synthesis of 5 and 6 carbon sugars from lignocellulosic biomass by photocatalytic reaction and the determination of the reaction conditions of catalysts that will provide valuable chemicals from these sugars were investigated. Basically, based on the hydrothermal method, ZnO/TiO2 binary metal oxide catalysts with 4 different recipes and different weight ratios were synthesized. The synthesized catalysts were characterized by XRD, SEM, FTIR, DRS, physical and chemical sorption methods. By examining the effects of synthesis methods and mixing ratios of binary metal oxide catalysts on photocatalytic activity, the most suitable photocatalyst was determined in terms of biomass conversion rate and product yield. Hazelnut shell and coffee shell treated with crude and dilute NaOH were used as biomass source. Photocatalic degradation of biomass was carried out in a specially designed batch photoreactor. Chemical analysis of the products obtained as a result of photocatalytic degradation was done by HPLC. In the photocatalytic experiments carried out in the photoreactor, the effects of biomass amount, time, pH and H2O2 amount parameters on biomass conversion and product yield were investigated. In the light of the data obtained, it has been seen that the synergistic effect of ZnO/TiO2 binary metal oxides has an important role in obtaining valuable chemicals from biomass. It has been concluded that the 7525ZT-III catalyst is the most effective catalyst for product yield and biomass conversion. When the biomass varieties were evaluated, it was seen that the pretreatment with NaOH was more effective on the coffee husk. As a result of the pretreatment, it was concluded that the lignin barrier in the structure was overcome and the cellulose and hemicellulose structure were released and the biomass surface area increased. As a result of parametric studies, the order of importance of the parameters in terms of product selectivity was found to be H2O2 amount>biomass amount>time>pH.
Lignocellulosic biomass emerges as an alternative to fossil resources, which meet the increasing need for energy and chemical raw materials in parallel with the industrialization and population growth rate. Contrary to fossil resources, lignocellulosic biomass, which includes plant and agricultural wastes, animal wastes and urban wastes, has an important place among sustainable and renewable resources. Traditionally used methods of obtaining energy, fuel and valuable chemicals from lignocellulosic biomass are energy-intensive and expensive methods. The use of photocatalytic reactions at room temperature and atmospheric pressure instead of these methods will also provide economic sustainability. In this study, the synthesis of 5 and 6 carbon sugars from lignocellulosic biomass by photocatalytic reaction and the determination of the reaction conditions of catalysts that will provide valuable chemicals from these sugars were investigated. Basically, based on the hydrothermal method, ZnO/TiO2 binary metal oxide catalysts with 4 different recipes and different weight ratios were synthesized. The synthesized catalysts were characterized by XRD, SEM, FTIR, DRS, physical and chemical sorption methods. By examining the effects of synthesis methods and mixing ratios of binary metal oxide catalysts on photocatalytic activity, the most suitable photocatalyst was determined in terms of biomass conversion rate and product yield. Hazelnut shell and coffee shell treated with crude and dilute NaOH were used as biomass source. Photocatalic degradation of biomass was carried out in a specially designed batch photoreactor. Chemical analysis of the products obtained as a result of photocatalytic degradation was done by HPLC. In the photocatalytic experiments carried out in the photoreactor, the effects of biomass amount, time, pH and H2O2 amount parameters on biomass conversion and product yield were investigated. In the light of the data obtained, it has been seen that the synergistic effect of ZnO/TiO2 binary metal oxides has an important role in obtaining valuable chemicals from biomass. It has been concluded that the 7525ZT-III catalyst is the most effective catalyst for product yield and biomass conversion. When the biomass varieties were evaluated, it was seen that the pretreatment with NaOH was more effective on the coffee husk. As a result of the pretreatment, it was concluded that the lignin barrier in the structure was overcome and the cellulose and hemicellulose structure were released and the biomass surface area increased. As a result of parametric studies, the order of importance of the parameters in terms of product selectivity was found to be H2O2 amount>biomass amount>time>pH.
Açıklama
Anahtar Kelimeler
Alkali işlem, Alkali process, Biyokütle, Biomass, Fotokatalitik, Photocatalytic, Katalitik reaksiyon, Catalytic reaction, Lignoselülozik yapı, Lignocellulosic structure, Metal oksitler, Metal oxides
