Hydrodeoxygenation of lignin-derived model compound isoeugenol over Fe-, Ni-, and Fe-Ni-supported on zeolites
Gauli, Bibesh (2021)
Julkaisun pysyvä osoite on
https://urn.fi/URN:NBN:fi-fe2021112256422
https://urn.fi/URN:NBN:fi-fe2021112256422
Tiivistelmä
As the world is transitioning away from fossil fuels, lignocellulosic biomass is scrutinized as a source of renewable fuels and chemicals. Political motivations and environmental concerns have increased the research in lignin, an underutilized resource currently, as a potential source of bio-oils. These bio-oils cannot be used in the existing petroleum-based infrastructures due to their high oxygen content and complex structures. Hence, catalytic hydrodeoxygenation could be used to reduce the oxygen content of the bio-oils.
This thesis aims to contribute to the ever-growing knowledge of the HDO of lignin-derived model compounds, as the HDO of isoeugenol over Fe- and Fe-Ni-based catalysts was conducted for the first time in this work. The reaction was investigated at 300 °C, and 30 bar total H2 pressure with hexadecane as a solvent. Iron was chosen for the metal modifications of zeolites because it is inexpensive, oxophilic, and environmentally friendly. The synthesized fresh and spent catalysts were characterized using different characterization techniques to explain their activity, selectivity, and stability in the HDO of isoeugenol.
The Fe-modified zeolites contained highly dispersed metal nanoparticles and microporous structures, according to the characterization results. However, the unreduced Fe-based catalysts exhibited poor activity in the HDO of isoeugenol as neither cycloalkanes nor alkylbenzenes were formed. A plethora of cracking products was produced, which could have originated both from the reactant and the solvent. The reduced Fe-based catalysts still did not exhibit sufficient HDO activity, as only minor concentrations of deoxygenated products were formed.
A suite of novel Fe, Ni, and Fe-Ni supported on H-Y-5.1 support was synthesized to study the synergistic effects of Fe and Ni active sites. Compared to the monometallic Fe and Ni catalysts, the bimetallic Fe-Ni catalyst exhibited better performance in the catalytic HDO of isoeugenol due to the synergy between Fe and Ni sites. The yield of the desired compounds such as propylcyclohexane, ethyl-methylcyclohexane, butylcyclopentane, and propylbenzene over the Fe-Ni catalyst with Fe to Ni weight ratio of 1:1 was 18%, 15%, 7%, and 3%, respectively.
This thesis aims to contribute to the ever-growing knowledge of the HDO of lignin-derived model compounds, as the HDO of isoeugenol over Fe- and Fe-Ni-based catalysts was conducted for the first time in this work. The reaction was investigated at 300 °C, and 30 bar total H2 pressure with hexadecane as a solvent. Iron was chosen for the metal modifications of zeolites because it is inexpensive, oxophilic, and environmentally friendly. The synthesized fresh and spent catalysts were characterized using different characterization techniques to explain their activity, selectivity, and stability in the HDO of isoeugenol.
The Fe-modified zeolites contained highly dispersed metal nanoparticles and microporous structures, according to the characterization results. However, the unreduced Fe-based catalysts exhibited poor activity in the HDO of isoeugenol as neither cycloalkanes nor alkylbenzenes were formed. A plethora of cracking products was produced, which could have originated both from the reactant and the solvent. The reduced Fe-based catalysts still did not exhibit sufficient HDO activity, as only minor concentrations of deoxygenated products were formed.
A suite of novel Fe, Ni, and Fe-Ni supported on H-Y-5.1 support was synthesized to study the synergistic effects of Fe and Ni active sites. Compared to the monometallic Fe and Ni catalysts, the bimetallic Fe-Ni catalyst exhibited better performance in the catalytic HDO of isoeugenol due to the synergy between Fe and Ni sites. The yield of the desired compounds such as propylcyclohexane, ethyl-methylcyclohexane, butylcyclopentane, and propylbenzene over the Fe-Ni catalyst with Fe to Ni weight ratio of 1:1 was 18%, 15%, 7%, and 3%, respectively.