Investigation of zeolite acid sites for 2,5-dimethylfuran conversion
Typ
Examensarbete för masterexamen
Program
Publicerad
2022
Författare
Mestre Tosas, Pol
Modellbyggare
Tidskriftstitel
ISSN
Volymtitel
Utgivare
Sammanfattning
Finding new routes for chemical valorisation of biological feedstocks is an essential part for developing
a biobased economy and reducing the use of fossil fuels. This project tailor’s new zeolite‐based catalytic
materials over which green aromatics, i.e., benzene, toluene, and xylenes (BTX), can be produced from
2,5‐dimethylfuran (2,5‐dmf), which can be obtained from pre‐processed low‐cost hemicellulose.
The acid sites present in different zeolite samples have been quantified and differentiated under
several experimental conditions to better understand the role of the acid sites in zeolites. The samples
studied are silica powder, alumina spheres and 3 HZSM‐5 zeolites ranging different SiO2/Al2O3 (SAR),
27, 55 and 330.
The experiments have been performed in a continuous flow reactor whose final stream has been
analysed by infrared and mass spectrometry in parallel. A, diffuse reflectance infrared Fourier
transform spectroscopy, DRIFTS experiment has also been performed to analyse the in‐situ evolution
of acid sites and products formed on the surface of the zeolite during a reaction.
The experiments revealed a decrease on the total amount of acid sites before and after the reaction
with 2,5‐dmf. Differences were found between the different types of acid sites, Brønsted acid sites
(BAS) and Lewis acid sites (LAS). BAS are the most abundant types of acid sites on HZSM‐5‐SAR55
zeolite but are easily deactivated with time on stream, while LAS showed the opposite behaviour,
allowing the production of compounds for longer periods of time and at higher temperatures.
Different group compounds such as olefins, aromatics or isomers have different production trends over
time. Aromatics production decreases faster with time on stream, compared to olefins and isomer
production, which decreases at slower pace over time. Coke formation, as well as the production of
compounds such as naphthalene, ethylene and toluene increase with temperature. Compounds such
as p‐xylene, which has a high value and was not obtained during continuous reaction, was only
produced when adsorbing 2,5‐dmf on the zeolite at low temperatures and then slowly increasing the
temperature. This is an indicator of different reaction mechanism compared to continuous production.
Beskrivning
Ämne/nyckelord
acid sites , BTX , catalyst , zeolite , 2,5‐dimethylfuran