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Author:Ukkonen, Mari
Title:Heterogeneous catalysts in the conversion of xylose to furfural
Heterogeeniset katalyytit ksyloosin konversiossa furfuraaliksi
Publication type:Master's thesis
Publication year:2011
Pages:vii + 96 + [4]      Language:   eng
Department/School:Kemian laitos
Main subject:Teknillinen kemia   (Kem-40)
Supervisor:Niemelä, Marita
Instructor:Karinen, Reetta ; Vilonen, Kati
OEVS:
Electronic archive copy is available via Aalto Thesis Database.
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Location:P1 Ark Aalto  2068   | Archive
Keywords:2-furaldehyde
D-xylose
zeolite
2-furaldehydi
D-ksyloosi
mordeniitti
Abstract (eng): The commercial synthesis of furfural involves the homogeneously catalysed cyclodehydration of xylose formed by the hydrolysis of xylan.
Due to the drawbacks of homogeneously catalysed processes as well as the risk factors related to the toxic liquid acids, efficient, heterogeneously catalysed industrial synthesis of furfural from xylose is strongly desirable.
Based on the literature survey, zeolites were found to be one of the promising catalyst materials for the dehydration.

Aqueous phase dehydration of D-xylose into furfural was performed in a continuous stirred tank reactor (CSTR).
Thermal dehydration experiments were carried out at 180 and 200°C.
H-mordenite with nSi/nAl = 18 (HSZ-640) was examined as a heterogeneous acid catalyst in the temperature range of 160 - 200 °C.
The activity of HSZ-640 was found to increase with increasing temperature.
At best, furfural yield of 36 % could be achieved at 80 % conversion with HSZ-640.
H-mordenites with different surface acidities were studied at 180°C.
HSZ-640 was found to exhibit higher activity for xylose dehydration than the H-mordenite with nSi/nAl = 240 (HSZ-690).
Selectivity of the heterogeneously catalysed reaction was found to be similar to, or lower than, that of the thermal dehydration experiment.
At 200°C in toluene/water solvent mixture a pentose conversion of 100 % was obtained.
However, the selectivity dropped dramatically to 6 % during the experiment.
Furthermore, the xylose loss to side-products increased with the addition of toluene.

Temperature-programmed oxidation (TPO) and total carbon content analysis were used to study the carbonaceous deposits of the used catalysts.
Although HSZ-640 was found to be strongly coked at 200°C, it could maintain its activity for 11 hours.
Abstract (fin): Teollinen furfuraalin valmistusprosessi koostuu homogeenisesti happokatalysoiduista ksylaanin hydrolyysista ja sitä seuraavasta ksyloosin dehydratoinnista.
Homogeenisen katalyysin haittojen vuoksi olisi tarpeen löytää tehokas, teolliseen käyttöön soveltuva heterogeeninen happokatalyytti furfuraalin valmistukselle ksyloosista.
Kirjallisuuskatsauksen perusteella tseoliitit ovat yksi lupaavista katalyyttimateriaaleista dehydratoinnille.

Ksyloosin dehydratointi furfuraaliksi suoritettiin vesiliuoksessa jatkuvatoimisessa sekoitussäiliöreaktorissa (CSTR).
Termiset dehydratointikokeet suoritettiin 180 ja 200 °C:ssa.
H-mordeniittia, jonka nSi/nAl = 18 (HSZ-640), käytettiin heterogeenisena katalyyttinä lämpötilavälillä 160 - 200 °C.
HSZ-640:n aktiivisuuden todettiin kasvavan lämpötilan kasvaessa.
Parhaimmillaan saavutettiin 36 %:n furfuraalisaanto 80 %:n konversiolla käyttäen HSZ-640 katalyyttia.
H-mordeniitin pintahappamuuden, nSi/nAl = 18 (HSZ-640) ja nSi/nAl = 240 (HSZ-690), vaikutusta ksyloosin konversioon tutkittiin 180°C:ssa.
H-mordeniitin, jonka pintahappamuus on suurempi (HSZ-640) todettiin olevan aktiivisempi ksyloosin dehydratoinnissa.
Heterogeenisesti katalysoidun dehydratoinnin selektiivisyys furfuraaliksi oli alhaisempi tai yhtä suuri kuin termisen dehydratoinnin selektiivisyys.
HSZ-640 katalyyttia tutkittiin 200°C:ssa myös käyttäen liuottimena tolueeni/vesi-seosta.
Pentoosisokereiden konversio oli tällöin 100 %, mutta selektiivisyys laski 6 %:iin kokeen kuluessa.
Lisäksi tolueenin lisäyksen todettiin kasvattavan ksyloosin konvergoitumista sivutuotteiksi.

Koksaantumista tutkittiin lämpötilaohjelmoidulla hapetuksella (TPO) sekä määrittämällä käytettyjen katalyyttien kokonaishiilipitoisuus.
Vaikka HSZ-640 katalyytin todettiin koksaantuvan voimakkaasti 200°C:ssa, sen aktiivisuus säilyi 11 tunnin ajan.
ED:2011-03-18
INSSI record number: 41584
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