Selective fructose dehydration to 5-hydroxymethylfufural by heterogeneous sulfated catalysts in different solvents

Thesis (Doctoral)--Izmir Institute of Technology, Chemical Engineering, Izmir, 2016
Includes bibliographical references (leaves: 96-99)
Text in English; Abstract: Turkish and English
xiii, 99 leaves
In the present study, different sulfated (SO4/ZrO2, SO4/SiO2, SO4/AC, SO4/TiO2SiO2 and SO4/Ti-SBA-15) and zirconium sulfate loaded (ZrSO4/SiO2 and ZrSO4/AC) catalysts were prepared and characterized. Effect of sulfur content (2.5, 3.0 and 3.5 wt. %) in SO4/ZrO2, effect of Ti content (2 and 6 wt. %) in SO4/ TiO2SiO2 and SO4/Ti-SBA-15, also La incorporation in to SO4/TiO2SiO2 and SO4/Ti-SBA-15 were investigated. Prepared catalysts were tested in fructose dehydration using dimethylsulfoxide (DMSO), water and biphasic aqueous solvents which were water-MIBK and water- MIBK-butanol. Effect of reaction temperature (110, 160 and 200 oC) and effect of fructose/catalyst weight ratio (WFr/Wcat = 0.5, 1.0 and 2.0) on activity and selectivity were investigated. Activity tests were performed in a batch reactor under N2 atmosphere. Reusability tests were carried out up to 4 times. Sulfated catalysts showed different activities. However, there was sulfur leaching in all of them except SO4/TiO2SiO2 and SO4/Ti-SBA-15. This was due to chelating bidendate bond formation between S, Ti and S. Sulfur leaching was also observed over zirconium sulfate loaded catalysts. Acidity of the catalysts increased with sulfur and Ti content; and also La addition. Sulfation created Brønsted acid sites. The most active, selective and stable catalyst was found to be SO4/La-TS-6 (95 % HMF selectivity at 58 % fructose conversion at 110 oC) in DMSO. Testing of this catalyst in water gave high amount of byproducts. Introducing second phase (MIBK) to water, improved HMF selectivity significantly (up to 78 %) and reduced conversion (by 7 %). Fructose dehydration kinetics was also investigated over this catalyst in water- MIBK-butanol (the most selective environmental benign solvent). Selectivity to HMF increased with reaction temperature up to 160 oC, above which it dropped. Increase in WFr/Wcat from 0.5 to 2.0, reduced the selectivity to HMF from 98 to 82 % at high fructose conversions (~90 %). Reaction was found to be 1st order in fructose concentration.
Bu çalışmada, farklı sülfatlanmış (SO4/ZrO2, SO4/SiO2, SO4/AC, SO4/ TiO2SiO2 ve SO4/Ti-SBA–15) ve zirkonyum sülfat yüklenmiş (ZrSO4/SiO2 ve ZrSO4/AC) katalizörler hazırlanmış ve karakterizasyonları yapılmıştır. SO4/ZrO2 içindeki sülfür miktarının (2.5, 3.0 ve 3.5 ağ. %), SO4/TiO2SiO2 ve SO4/Ti-SBA-15 içindeki Ti miktarının (2 ve 6 ağ. %), ayrıca SO4/TiO2SiO2 ve SO4/Ti-SBA-15 içine La eklenmesinin etkisi incelenmiştir. Hazırlanan katalizörler fruktoz dehidrasyonunda dimetilsülfoksit (DMSO), su ve çift fazlı sulu çözücüler (su-MIBK ve su-MIBK-bütanol) kullanılarak test edilmiştir. Reaksiyon sıcaklığının (110, 160 ve 200 oC) ve fruktoz/katalizör ağırlık oranının (WFr/Wcat = 0.5, 1.0 ve 2.0) aktivite ve seçicilik üzerine etkisi incelenmiştir. Aktivite testleri kesikli reaktör içinde azot ortamında gerçekleştirilmiştir. Tekrar kullanılabilirlik testleri 4 kereye kadar yapılmıştır. Sülfatlanmış katalizörler farklı aktivite sonuçları göstermiştir. Ancak, SO4/TiO2SiO2 ve SO4/Ti-SBA-15 dışındaki tüm sülfatlanmış katalizörlerde sülfür liçi görülmüştür. Elde edilen bu sonuç şelatlayıcı bidentate bağların oluşumuna bağlanmıştır. Zirkonyum sülfat yüklü katalizörlerde de sülfür liçi gözlemlenmiştir. Katalizörlerin asitliği sülfür, Ti miktarı ve La eklemesiyle artmıştır. Sülfatlama işlemi Brønsted tipi asit merkezleri oluşturmuştur.